Display device, display system, mobile unit, and display panel housing device

Abstract

This prevents deformation of optical components and misalignment of optical components from occurring, which can lead to a decrease in display quality. [Solution] The display device comprises a housing having a viewing section, a display panel located inside the housing and having a display surface, and an optical system located inside the housing between the viewing section and the display panel, having a semi-transparent mirror, for forming an image of the display surface and creating a virtual image. The first angle is defined as the size of the angle between the two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, and each of the pair of endpoints of the semi-transparent mirror, which are aligned horizontally, and the second angle is defined as the size of the angle between the two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, and each of the pair of endpoints of the semi-transparent mirror, which are aligned vertically, and the first angle is greater than the second angle.

Description

[Technical Field]

[0001] This disclosure relates to a display device, a display system, a mobile device, and a display panel housing device. [Background technology]

[0002] Conventionally, a display device described in, for example, Patent Document 1 is known. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-63533 [Overview of the project]

[0004] The display device of this disclosure comprises a housing having a viewing section, A display panel located inside the aforementioned housing and having a display surface, The housing is located between the viewing section and the display panel and includes an optical system having a semi-transparent mirror for forming an image of the display surface and creating a virtual image. When the first angle is defined as the angle between the two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, and each of the pair of endpoints of the semitransparent mirror, which are aligned horizontally, and the second angle is defined as the angle between the two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, and each of the pair of endpoints of the semitransparent mirror, which are aligned vertically, the first angle is greater than the second angle.

[0005] The display device of this disclosure comprises a housing having a viewing section, A display panel located inside the aforementioned housing and having a display surface, The housing is located between the viewing section and the display panel and includes an optical system having a semi-transparent mirror for forming an image of the display surface and creating a virtual image. When the intersection of two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, to each of the pair of endpoints of the semi-transparent mirror, which are aligned horizontally, is defined as the first intersection point, and the intersection of two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, to each of the pair of endpoints of the semi-transparent mirror, which are aligned vertically, is defined as the second intersection point, the first intersection point is located closer to the semi-transparent mirror than the second intersection point.

[0006] The display system of this disclosure comprises the display device, A camera capable of communicating with the aforementioned display device, The system comprises a control unit for controlling the image displayed on the display panel, The display panel displays the image captured by the camera. The control unit controls the video so that supplementary information is displayed in the first and second regions.

[0007] The mobile device of this disclosure includes the display device.

[0008] The display panel housing device disclosed herein comprises a housing having a viewing section, A display panel mounting section located within the aforementioned housing, on which a display panel having a display surface can be installed, The housing is located between the display panel mounting section and the viewing section and includes an optical system having a semi-transparent mirror for forming an image of the display surface and creating a virtual image. When the first angle is defined as the angle between the two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, and each of the pair of endpoints of the semitransparent mirror, which are aligned horizontally, and the second angle is defined as the angle between the two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, and each of the pair of endpoints of the semitransparent mirror, which are aligned vertically, the first angle is greater than the second angle.

[0009] The display panel housing device disclosed herein comprises a housing having a viewing section, A display panel mounting section located within the aforementioned housing, on which a display panel having a display surface can be installed, It is located between the display panel installation part and the viewing part in the housing, has a semi-transparent mirror, and includes an optical system for forming a virtual image by imaging the display surface. When the intersection of two straight lines connecting each of the pair of both ends arranged in the left-right direction of the virtual image and each of the pair of both ends arranged in the left-right direction of the semi-transparent mirror is defined as the first intersection point, and the intersection of two straight lines connecting each of the pair of both ends arranged in the up-down direction of the virtual image and each of the pair of both ends arranged in the up-down direction of the semi-transparent mirror is defined as the second intersection point, the first intersection point is located closer to the semi-transparent mirror side than the second intersection point.

Brief Description of the Drawings

[0010] The object, features, and advantages of the present disclosure will become more apparent from the following detailed description and the drawings. [Figure 1] It is a diagram schematically showing the configuration of the display device of the present disclosure. [Figure 2] It is a cross-sectional view showing an example of the main part configuration of the display device according to an embodiment of the present disclosure. [Figure 3] It is a cross-sectional view showing another example of the main part configuration of the display device according to an embodiment of the present disclosure. [Figure 4] It is a cross-sectional view showing an example of the main part configuration of the display device according to another embodiment of the present disclosure. [Figure 5] It is a cross-sectional view showing another example of the main part configuration of the display device according to another embodiment of the present disclosure. [Figure 6] It is a diagram for explaining the projection of the virtual image in the display device of FIG. 4. [Figure 7] It is a diagram for explaining the projection of the virtual image in the display device of FIG. 5. [Figure 8] It is a diagram for explaining the design of the optical system in the display device of FIG. 5. [Figure 9] It is a cross-sectional view showing an example of the main part configuration of the display device according to still another embodiment of the present disclosure. [Figure 10] It is a diagram showing an example of the configuration of the imaging device according to an embodiment of the present disclosure. [Figure 11]This figure shows another example of the configuration of an imaging apparatus according to one embodiment of the present disclosure. [Figure 12] This figure shows another example of the configuration of an imaging apparatus according to one embodiment of the present disclosure. [Figure 13] This is a top view illustrating another example of a display device. [Figure 14] This is a top view illustrating another example of a display device. [Figure 15] This is a cross-sectional view illustrating another example of a display device. [Figure 16] This is a cross-sectional view illustrating another example of a display device. [Figure 17A] This is a diagram illustrating the optical system in another example of a display device. [Figure 17B] This is a diagram illustrating the optical system in another example of a display device. [Figure 17C] This is a diagram illustrating the optical system in another example of a display device. [Figure 17D] This is a diagram illustrating the optical system in another example of a display device. [Figure 18A] This is a diagram illustrating the optical system in another example of a display device. [Figure 18B] This is a diagram illustrating the optical system in another example of a display device. [Figure 18C] This is a diagram illustrating the optical system in another example of a display device. [Figure 18D] This is a diagram illustrating the optical system in another example of a display device. [Figure 19] This is a graph illustrating the optical system in other examples of display devices. [Figure 20] This is a cross-sectional view illustrating another example of a display device. [Figure 21] This is a cross-sectional view illustrating another example of a display device. [Figure 22] This is a cross-sectional view illustrating another example of a display device. [Figure 23] This is a cross-sectional view showing an example of the configuration of the second semi-transparent mirror. [Figure 24]This is a cross-sectional view illustrating another example of a display device. [Figure 25] This diagram illustrates how virtual images appear when a user is positioned directly in front of the display device. [Figure 26] This diagram illustrates how virtual images appear when the user is not positioned directly in front of the display device. [Figure 27] This diagram illustrates how virtual images appear after adjusting the display device. [Figure 28] This diagram illustrates how virtual images appear after adjusting the display device. [Figure 29] This is a flowchart explaining the control of the imaging device. [Figure 30] This is a cross-sectional view showing another example of the main components of a display device according to one embodiment of the present disclosure. [Figure 31] This is a cross-sectional view showing another example of the main components of a display device according to another embodiment of the present disclosure. [Figure 32] This is a cross-sectional view showing another example of the essential components of a display device according to yet another embodiment of the present disclosure. [Figure 33] This is a perspective view showing a cross-section of another example of a display device according to one embodiment of the present disclosure. [Figure 34] This is a cross-sectional view showing another example of a display device according to one embodiment of the present disclosure. [Figure 35] This is a perspective view showing a cross-section of another example of a display device according to one embodiment of the present disclosure. [Figure 36] This is a cross-sectional view showing another example of a display device according to one embodiment of the present disclosure. [Figure 37] Figure 2 shows the optical path of the display light in the display device. [Figure 38] Figure 2 is a cross-sectional view showing another example of a display device. [Figure 39] This figure shows an example of the configuration of a display system and a vehicle according to one embodiment of the present disclosure. [Figure 40] This is a perspective view showing a cross-section of yet another example of a display device according to one embodiment of the present disclosure. [Figure 41] Figure 40 is a plan view of the image formed by the display device shown. [Figure 42] This is a top view illustrating how to view the viewing area directly. [Figure 43] This diagram compares the length of the viewing section along its longitudinal direction with the length of the semi-transparent mirror along its longitudinal direction. [Figure 44] This diagram illustrates the two straight lines connecting the endpoints of the image and the endpoints of the semi-transparent mirror in a cross-sectional view. [Figure 45] This diagram illustrates the two straight lines connecting the endpoints of the image and the endpoints of the semi-transparent mirror in a cross-sectional view. [Figure 46] This is a perspective view showing a cross-section of yet another example of a display device according to one embodiment of the present disclosure. [Figure 47] This block diagram shows another example of a display device according to one embodiment of the present disclosure. [Figure 48] This is a plan view of the image formed by the display device shown in Figure 47. [Figure 49] This is a cross-sectional view showing an example of the main components of a display device according to the present disclosure. [Figure 50] This is a cross-sectional view showing an example of the main components of a display device according to the present disclosure. [Figure 51] This is a cross-sectional view showing an example of the main components of a display device according to the present disclosure. [Figure 52] This is a cross-sectional view showing an example of the main components of a display device according to the present disclosure. [Figure 53A] Figures 49-52 illustrate the optical functions of the respective display devices. [Figure 53B] Figures 49-52 illustrate the optical functions of the respective display devices. [Figure 54] Figure 34 shows an example of various dimensions of the display device. [Modes for carrying out the invention]

[0011] Conventionally, various small display devices have been proposed for use in digital rearview mirrors placed inside the vehicle's interior, head-mounted displays worn on the user's head, and so on. The display device described in Patent Document 1 is configured to emit display light from a display panel through a plurality of optical components such as a phase difference plate and a reflective polarizing plate.

[0012] Conventional display devices were prone to deformation of optical components and misalignment of optical components, which could lead to a decrease in display quality.

[0013] Embodiments of this disclosure will be described below with reference to the drawings. Some of the figures used in the following description are schematic. The figures used in the following description show the main components of the display device and virtual image display device of this disclosure. The display device and virtual image display device of this disclosure may include well-known components not shown, such as optical system holders and housings. In this specification, in some drawings, a Cartesian coordinate system XYZ is defined for convenience. The X-axis direction is also referred to as the left-right direction. The Y-axis direction is also referred to as the height direction or up-down direction. The Z-axis direction is also referred to as the output direction or depth direction. In this disclosure, the Y-axis direction may be the direction along the vertical direction of the image of the virtual image V, and the X-axis direction may be the direction along the left-right direction of the image of the virtual image V.

[0014] Figures 1-39 are diagrams or graphs illustrating the display device, imaging device, display system, and vehicle of the present disclosure. In Figures 2-5, 9, 15, 16, 20-22, 24, and 30-32, the optical path of light incident on a light-reflective optical member and the optical path of light reflected by the optical member are shown shifted in the height direction (Y-axis direction) for ease of illustration.

[0015] A display device 1 in one embodiment of the present disclosure comprises a display panel 2 and an optical system 3, as shown in Figure 1. The display device 1 directs a portion of the display light emitted from the display panel 2 into the eyes of a user 22, allowing the user 22 to view it as an image, picture, or aerial image. The display device 1 can cause the user 22 to view the display on the display panel 2 at a position different from the position of the display panel 2. In the positional embodiment of the present disclosure, the display device 1 allows the user 22 to view it as a virtual image V. The virtual image V may be formed on the side of the display device 1 that is further away from the user 22. The virtual image V may be an upright virtual image that is an enlarged version of the display image displayed on the display panel 2. If the display device 1 comprises a housing (see Figures 33-36) that houses the display panel 2 and the optical system 3, the virtual image V may be formed inside the housing or outside the housing. The virtual image V may be formed on the side of the user 22 that is further away from the display panel 2 or on the side that is closer to the display panel 2. If the housing has a window 37 (see Figures 33-36) that transmits the display light emitted from the optical system 3, the virtual image V may be formed on the side farther from the window 37 (light-transmitting plate 38) as seen from the user 22, or on the side closer to the window. If the display device 1 has a touch panel 41 (see Figures 35 and 36), the virtual image V may be formed on the side farther from the touch panel 41 as seen from the user 22, or on the side closer to the touch panel 41.

[0016] The display device 1 in one embodiment of this disclosure may be a non-attachable device for the user 22. That is, it may not be attached to the user 22 but may be fixed to the environment. The display device 1 may be fixed to, for example, a wall, column, or ceiling. The display device 1 may also be fixed to the interior of a vehicle. The display device 1 may be attached to the user 22. If attached to the user 22, the display device 1 may have a mounting part (not shown) so that the window 37 is fixed at the position of the user 22's eyes.

[0017] The display device 1 may be configured to direct a portion of the display light emitted from the display panel 2 into the eyes of the user 22, allowing the user 22 to perceive it as a real image. The real image may be formed on the side closer to the display device 1 as seen from the user 22. If the display device 1 includes a housing 36 (see Figures 33-36) that houses the display panel 2 and the optical system 3, the real image may be formed inside the housing 36 or outside the housing 36. The real image may be formed on the side farther from the display panel 2 as seen from the user 22, or on the side closer to the display panel 2. If the housing 36 has a window 37 (see Figures 33-36) that transmits the display light emitted from the optical system 3, the real image may be formed on the side farther from the window 37 (light-transmitting plate 38) as seen from the user 22, or on the side closer to the window 37 (light-transmitting plate 38). If the display device 1 has a touch panel 41 (see Figures 35 and 36), the real image may be formed on the side farther from the touch panel 41 or on the side closer to the touch panel 41, as viewed from the user 22.

[0018] The display panel 2 has a display surface 2a, on which a display image is displayed. In other words, the display panel 2 emits display light of the display image from the display surface 2a. The display panel 2 may be configured to emit linearly polarized display light. The following description will focus on, but is not limited to, the case in which the display panel 2 emits S-wave polarized display light.

[0019] Display panel 2 may be a liquid crystal panel. The liquid crystal panel may have a known liquid crystal panel configuration. Known liquid crystal panels may be, for example, IPS (In-Plane Switching), FFS (Fringe Field Switching), VA (Vertical Alignment), or ECB (Electrically Controlled Birefringence) liquid crystal panels.

[0020] The display device 1 may include an irradiator 4 that illuminates the display panel 2 in a planar manner. The irradiator 4 is also called a backlight. The irradiator 4 may be an edge-lit backlight or a direct-lit backlight. An edge-lit backlight has one or more light sources arranged on the outer periphery of the display panel 2, and guides the light emitted from the light sources to the entire back surface of the display panel 2 by a light guide plate for uniform dispersion. A direct-lit backlight has multiple light sources arranged on the back side of the display panel 2, and illuminates the display panel 2 with light emitted from the multiple light sources. The light sources of the irradiator 4 may be cold cathode fluorescent lamps, halogen lamps, or xenon lamps, or they may be light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), semiconductor lasers (LDs), etc. If the light source of the irradiator 4 is an LD with excellent monochromaticity, the design of the optical system 3, in particular the design of optical components whose optical properties are wavelength-dependent, becomes easier.

[0021] The display panel 2 is not limited to a liquid crystal panel (transmissive display panel). The display panel 2 may be a self-emissive display panel that includes self-emissive elements such as a light-emitting diode (LED), an organic light-emitting diode (OLED), or a semiconductor laser (LD).

[0022] The optical system 3 projects the display light emitted from the display panel 2 as a virtual image V within the user's field of view 22. The optical system 3 may be configured to include a first phase difference plate 5, a semi-transparent mirror 6, a second phase difference plate 7, and a reflective polarizer 8, as shown in Figure 2. The first phase difference plate 5, the semi-transparent mirror 6, the second phase difference plate 7, and the reflective polarizer 8 are arranged in this order in the direction of emission of the display light from the display panel 2 (positive direction in the Z-axis direction).

[0023] The first phase difference plate 5 is positioned opposite the display surface 2a of the display panel 2. The first phase difference plate 5 is positioned away from the display surface 2a in the direction of emission of display light from the display panel 2. The second phase difference plate 7 is positioned away from the first phase difference plate 5 in the direction of emission of display light from the display panel 2. The first phase difference plate 5 and the second phase difference plate 7 are quarter-wave plates. The first phase difference plate 5 and the second phase difference plate 7 impart a quarter-wave phase difference to the polarization plane (polarization plane in the direction of electric field vibration) of the incident light. This makes it possible to reflect a portion of the display light emitted from the display panel 2 by the reflective polarizer 8 and direct it into the semi-transparent mirror 6.

[0024] The first phase difference plate 5 and the second phase difference plate 7 only need to be able to provide the necessary phase difference to the light transmitted through them so that the light transmitted through them is reflected by the reflective polarizer 8. That is, for example, when the polarization obtained after transmitting through the first phase difference plate 5 and the second phase difference plate 7 is defined as the second polarization, the first phase difference plate 5 and the second phase difference plate 7 may be other wavelength plates or combinations thereof, rather than quarter-wave plates, as long as the second polarization is obtained. In this disclosure, the case where the first phase difference plate 5 and the second phase difference plate 7 are quarter-wave plates will be explained as an example.

[0025] Furthermore, the second phase difference plate 7 only needs to be able to provide the necessary phase difference to the light that has passed through the second phase difference plate 7 so that the light that has been reflected by the reflective polarizer 8 and passed through the second phase difference plate 7 passes through the reflective polarizer 8 again when it reaches the reflective polarizer 8. In other words, for example, if the polarization obtained after being reflected by the reflective polarizer 8 and passed through the second phase difference plate 7 is taken as the first polarization, the second phase difference plate 7 may be a wave plate other than a quarter wave plate, as long as the first polarization is obtained.

[0026] The first phase difference plate 5 may be integrated with the display panel 2, as shown in Figure 30. "Integration" may mean that the two members are arranged so as to be in contact with each other, or that the two members are joined to each other by an optically transparent adhesive such as OCA (Optically Clear Adhesive).

[0027] The semi-transparent mirror 6 is positioned between the first phase difference plate 5 and the second phase difference plate 7. The semi-transparent mirror 6 may transmit a portion of the incident light (e.g., approximately 50%) and reflect the remainder (e.g., approximately 50%). The semi-transparent mirror 6 reflects a portion of the display light reflected by the reflective polarizer 8 and directs it into the eyes of the user 22. This makes it possible for the user 22 to see the virtual image V. The semi-transparent mirror 6 has the function of focusing or converging light. Specifically, the semi-transparent mirror 6 has the function of focusing or converging light that is incident on and reflected by the semi-transparent mirror 6. In this embodiment, the semi-transparent mirror 6 can focus or converge light more effectively than other members of the optical system 3. In other words, the semi-transparent mirror 6 has a larger setting for indicators such as the degree of focusing, degree of convergence, or the reciprocal of the focal length than other members of the optical system 3. Furthermore, in this embodiment, the optical system 3 may have only a semi-transparent mirror 6 as a component having a light-gathering or focusing function. The semi-transparent mirror 6 may be a concave mirror having a concave reflective surface 6a, as shown in Figure 2. The semi-transparent mirror 6 faces the second phase difference plate 7, and more specifically, the reflective surface 6a of the semi-transparent mirror 6 may face the second phase difference plate 7. In this embodiment, the semi-transparent mirror 6 can gather or focus light by having a concave reflective surface 6a. The reflective surface 6a of the semi-transparent mirror 6 has a greater curvature than the other components of the optical system 3. The semi-transparent mirror 6 may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface 6a. The transmittance of the semi-transparent mirror 6 is not limited to 50%.

[0028] The semi-transparent mirror 6 is composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The semi-transparent reflective layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film, etc. The semi-transparent mirror 6 may be configured to reflect light with the semi-transparent reflective layer. The semi-transparent reflective layer may be formed on the surface of the substrate facing the second phase difference plate 7.

[0029] The reflective polarizer 8 is positioned opposite the surface of the second phase difference plate 7 that faces the semi-transparent mirror 6. In other words, the reflective polarizer 8 is positioned downstream of the second phase difference plate 7 in the direction of emission of display light from the display panel 2. The reflective polarizer 8 may transmit a portion of the incident light and reflect the remainder. In this embodiment, the reflective polarizer 8 is configured to reflect polarized light having a polarization axis perpendicular to the polarization axis of the display light (also called P-wave polarization or second polarization) and transmit polarized light having a polarization axis parallel to the polarization axis of the display light (also called S-wave polarization or first polarization). This makes it possible for the user 22 to see the virtual image V. The reflective polarizer 8 may be integrated with the second phase difference plate 7, as shown in Figure 30.

[0030] The reflective polarizer 8 may be a wire grid polarizer comprising, for example, a substrate and a plurality of metal nanowires (also called a metal nanowire grid) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, a resin material, a glass material, etc. The metal nanowires may be made of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The reflective polarizer 8 can transmit light components vibrating in a direction perpendicular to the grid and can reflect light components vibrating in a direction parallel to the grid.

[0031] The display device 1 includes a controller 43. The controller 43 is connected to each component of the display device 1 and controls each component. The controller 43 may control the irradiator 4. The controller 43 may control the display image displayed on the display panel 2 and the irradiator 4. The controller 43 may control the irradiator 4 based on the display image displayed on the display panel 2. The controller 43 may be configured to include one or more processors. The processors may include general-purpose processors configured to load specific programs and execute specific functions, and dedicated processors specialized for specific processing. The processors may include PLDs (Programmable Logic Devices). The controller 43 may be either a SoC (System-on-a-Chip) or a SiP (System In a Package) in which one or more processors cooperate. The controller 43 includes a memory unit, which may store various information or programs for operating each component of the display device 1. The memory unit may be composed of, for example, semiconductor memory. The memory unit may function as the work memory of the controller 43.

[0032] The optical function of optical system 3 will now be described. Display panel 2 emits display light that is S-wave polarized (first linearly polarized light L1). The display light of the first linearly polarized light L1 emitted from display panel 2 passes through the first phase difference plate 5 and is converted into light of the first circularly polarized light C1. A portion of the first circularly polarized light C1 that has passed through the first phase difference plate 5 (for example, approximately 50%) passes through the semi-transparent mirror 6. The first circularly polarized light C1 that has passed through the semi-transparent mirror 6 passes through the second phase difference plate 7 and is converted into light of the second linearly polarized light L2, whose polarization direction is orthogonal to the first linearly polarized light L1 (i.e., it is P-wave polarized). The light of the second linearly polarized light L2 is incident on the reflective polarizer 8. As described above, the reflective polarizer 8 reflects P-wave polarized light and transmits S-wave polarized light. The light of the second linearly polarized light L2 incident on the reflective polarizer 8 is reflected by the reflective polarizer 8 and converted into light of the third linearly polarized light L3. The third linearly polarized light L3 passes through the second phase difference plate 7 and is converted into the second circularly polarized light C2. A portion of the second circularly polarized light C2 that has passed through the second phase difference plate 7 (for example, about 50%) is reflected by the semitransparent mirror 6 and converted into the third circularly polarized light C3. The third circularly polarized light C3 passes through the second phase difference plate 7 and is converted into the fourth linearly polarized light L4, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., it is S-wave polarized). The fourth linearly polarized light L4 passes through the reflective polarizer 8 and is emitted to the outside. The amount of light (luminance) emitted from the display device 1 is, for example, about 25% of the amount of display light (luminance) emitted from the display panel 2.

[0033] The first phase difference plate 5, the semi-transparent mirror 6, the second phase difference plate 7, and the reflective polarizing plate 8 are held by a holding member (not shown) to maintain their relative positions. Air is interposed between the first phase difference plate 5 and the second phase difference plate 7 (i.e., between the first phase difference plate 5 and the semi-transparent mirror 6, and between the semi-transparent mirror 6 and the second phase difference plate 7). Since the display device 1 does not have a member made of resin material such as polymer between the first phase difference plate 5 and the second phase difference plate 7, the risk of deformation of the semi-transparent mirror 6 when the resin material is cured during the manufacturing process of the display device 1, and misalignment of the semi-transparent mirror 6 with the first phase difference plate 5 and the second phase difference plate 7 can be reduced. In addition, resin materials such as polymers have material-specific retardation, and the risk of changing the polarization state of light transmitted through the resin material can also be reduced. As a result, the deterioration of display quality can be reduced.

[0034] Since the optical system 3 is an on-axis type optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the space occupied by the optical system 3 can be reduced, and as a result, the display device 1 can be miniaturized. In addition, because the optical system 3 is on-axis, distortion and brightness unevenness of the virtual image V seen by the user 22 can be reduced, and the design of the optical system 3 is simplified.

[0035] In the display device 1, the optical path length of the light emitted from the display panel 2, passing through the semi-transparent mirror 6, reflected by the reflective polarizer 8, and returning to the semi-transparent mirror 6 may be smaller than the focal length of the semi-transparent mirror 6. In this case, the user 22 can perceive a virtual image V. In the display device 1, the optical path length of the light emitted from the display panel 2, passing through the semi-transparent mirror 6, reflected by the reflective polarizer 8, and returning to the semi-transparent mirror 6 may be larger than the focal length of the semi-transparent mirror 6. In this case, the user 22 can perceive a real image.

[0036] In Figure 2, for the sake of illustration, the optical path of light incident on the reflective polarizer 8 and the optical path of light reflected by the reflective polarizer 8 are shown shifted in the height direction (Y-axis direction), and the optical path of light incident on the semi-transparent mirror 6 and the optical path of light reflected by the semi-transparent mirror 6 are also shown shifted in the height direction (Y-axis direction). However, in reality, the display light emitted from the display panel 2 propagates substantially along a single axis, as shown in Figure 37. This is also true for the optical paths shown in Figures 3-5, 9, 15, 16, 20-22, 24, and 30-32.

[0037] As shown in Figure 38, the display device 1 may replace the first phase difference plate 5, semi-transparent mirror 6, second phase difference plate 7, and reflective polarizer 8 with a convex lens 42. The optical path length from the display panel 2 to the convex lens 42 of the display device 1 may be shorter than the focal length of the convex lens 42. In this case, the virtual image V of the user 22 can be viewed. The optical path length from the display panel 2 to the convex lens 42 of the display device 1 may be longer than the focal length of the convex lens 42. In this case, the real image of the user 22 can be viewed.

[0038] The display panel 2 may display a mixed image including a left-eye image and a right-eye image having parallax with respect to each other, and may emit display light of the mixed image. The display device 1 may include an optical element 9 located in the optical path of the display light emitted from the display panel 2, as shown in Figure 3. The optical element 9 is configured to direct a portion of the display light of the mixed image to one of the user 22's left or right eye, and to direct another portion of the display light to the other of the user 22's left or right eye. The optical element 9 is configured to direct at least a portion of the display light of the left-eye image to the user 22's left eye and at least a portion of the display light of the right-eye image to the user 22's right eye by defining the direction of each ray of the display light of the left-eye image and the display light of the right-eye image. This enables the display device 1 to allow the user 22 to view a stereoscopic image.

[0039] The optical element 9 only needs to be capable of directing a portion of the display light of the mixed image to one of the user's left and right eyes, and the other portion of the display light to the other of the user's left and right eyes. For example, it may be a parallax barrier or a lenticular lens. The parallax barrier may be composed of a liquid crystal panel. The position of the optical element 9 is arbitrary within the display device 1. The optical element 9 may be located between the display panel 2 and the first phase difference plate 5, or after the reflective polarizer 8 in the direction of the display light emission, or between the semi-transparent mirror 6 and the second phase difference plate 7.

[0040] Next, a display device according to another embodiment of the present disclosure will be described. The display device of this embodiment differs from the display device of the above embodiment in the configuration of the optical system, but otherwise has the same configuration. Therefore, the same reference numerals are used for the same components, and a detailed description will be omitted.

[0041] As shown in Figure 4, the display device 1A of this embodiment comprises a display panel 2 and an optical system 10. The display panel 2 has a display surface 2a, on which a display image is displayed. The optical system 10 projects the display light emitted from the display panel 2 as a virtual image V within the user's field of view 22.

[0042] The optical system 10 comprises a first semi-transparent mirror 11, a first phase difference plate 12, a second semi-transparent mirror 13, a second phase difference plate 14, and a polarizing plate 15. That is, the optical system 10 has a pair of semi-transparent mirrors (first semi-transparent mirror 11, second semi-transparent mirror 13). The first semi-transparent mirror 11, the first phase difference plate 12, the second semi-transparent mirror 13, the second phase difference plate 14, and the polarizing plate 15 are arranged in this order in the direction of emission of display light from the display panel 2.

[0043] The first semi-transparent mirror 11 has a reflective surface 11a that reflects light. The first phase difference plate 12 is opposite the first semi-transparent mirror 11, and more specifically, is positioned opposite the reflective surface 11a of the first semi-transparent mirror 11. The first phase difference plate 12 is positioned away from the display surface 2a in the direction of emission of display light from the display panel 2. The second phase difference plate 14 is positioned away from the first phase difference plate 12 in the direction of emission of display light. The first semi-transparent mirror 11 has a function of collecting or focusing light. Specifically, the first semi-transparent mirror 11 has a function of collecting or focusing light that is incident on and reflected by the reflective surface 11a of the first semi-transparent mirror 11. In this embodiment, the first semi-transparent mirror 11 has, for example, an index that is larger than the other members of the optical system 10, such as a degree of collection, degree of convergence, or index expressed as the reciprocal of the focal length. The first phase difference plate 12 and the second phase difference plate 14 are quarter-wave plates.

[0044] The first semi-transparent mirror 11 is located between the display panel 2 and the first phase difference plate 12. The first semi-transparent mirror 11 may transmit a portion of the incident light and reflect the remainder. As shown in Figure 4, the first semi-transparent mirror 11 is a concave mirror having a concave reflective surface 11a facing the first phase difference plate 12. In this embodiment, the first semi-transparent mirror 11 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. The first semi-transparent mirror 11 may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface 11a.

[0045] The first semi-transparent mirror 11 may be composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal nanowires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The first semi-transparent mirror 11 can transmit light components vibrating in a direction perpendicular to the grid and reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate on the side of the first phase difference plate 12. In this example, the metal nanowire grid is used to impart a reflective polarization function to the first semi-transparent mirror 11, but the first semi-transparent mirror 11 may be used as a simple half-mirror and a separate reflective polarizer may be provided.

[0046] The second semi-transparent mirror 13 is located between the first phase difference plate 12 and the second phase difference plate 14. The second semi-transparent mirror 13 may transmit a portion of the incident light (e.g., approximately 50%) and reflect the remainder (e.g., approximately 50%). The second semi-transparent mirror 13 has a reflective surface 13a. The second semi-transparent mirror 13 is facing the first phase difference plate 12, and more specifically, as shown in Figure 4, it may be a plane mirror positioned so that the reflective surface 13a faces the first phase difference plate 12. The second semi-transparent mirror 13 is also called a plane half-mirror. The second semi-transparent mirror 13 may be integrated with at least one of the first phase difference plate 12 and the second phase difference plate 14, as shown in Figure 31.

[0047] The second semi-transparent mirror 13 may be composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent reflective layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film, etc.

[0048] The polarizing plate 15 is positioned opposite the surface of the second phase difference plate 14 that faces the second semitransparent mirror 13. In other words, the polarizing plate 15 is positioned downstream of the second phase difference plate 14 in the direction of emission of display light from the display panel 2. The polarizing plate 15 may transmit a portion of the incident light and absorb the remainder. In this embodiment, the polarizing plate 15 is configured to transmit P-wave polarized light and absorb S-wave polarized light. The polarizing plate 15 may be integrated with the second phase difference plate 14, as shown in Figure 31.

[0049] The polarizing plate 15 may have the configuration of a known absorption polarizing plate. Known absorption polarizing plates may be, for example, an iodine-based polarizing plate in which an iodine compound is adsorbed and oriented on a polyvinyl alcohol (PVA) film, or a dye-based polarizing plate in which a dichroic organic dye is adsorbed and oriented on a PVA film.

[0050] The optical function of the optical system 10 is described below. The display light, which is S-wave polarized (first linearly polarized L1), emitted from the display panel 2, passes through the first semi-transparent mirror 11. The display light of the first linearly polarized L1 passes through the first phase difference plate 12 and is converted into light of the first circularly polarized C1. The light of the first circularly polarized C1 is incident on the second semi-transparent mirror 13. A portion of the light of the first circularly polarized C1 (for example, approximately 50%) is reflected by the second semi-transparent mirror 13 and converted into light of the second circularly polarized C2. The light of the second circularly polarized C2 passes through the first phase difference plate 12 and is converted into light of the second linearly polarized L2, whose polarization direction is perpendicular to that of the first linearly polarized L1 (i.e., it is P-wave polarized). The light of the second linearly polarized L2 is reflected by the first semi-transparent mirror 11 and is converted into light of the third linearly polarized L3, whose polarization direction is perpendicular to that of the first linearly polarized L1. The third linearly polarized light L3 passes through the first phase difference plate 12 and is converted into the third circularly polarized light C3. A portion of the third circularly polarized light C3 (for example, approximately 50%) passes through the second semitransparent mirror 13. The third circularly polarized light C3 that has passed through the second semitransparent mirror 13 passes through the second phase difference plate 14 and is converted into the fourth linearly polarized light L4, whose polarization direction is perpendicular to the first linearly polarized light L1 (i.e., it is P-wave polarized). The fourth linearly polarized light L4 passes through the polarizer 15 and is emitted to the outside.

[0051] The remaining portion of the light from the first circularly polarized light C1 (for example, approximately 50%) passes through the second semi-transparent mirror 13, then through the second phase difference plate 14, and is converted into fifth linearly polarized light L5, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized light). The fifth linearly polarized light L5 is absorbed by the polarizer 15 and is therefore not emitted to the outside. In other words, the fifth linearly polarized light L5 is light that is not transmitted through the polarizer 15. Therefore, the amount of light (luminance) emitted from the display device 1A is, for example, approximately 25% of the amount of display light (luminance) emitted from the display panel 2.

[0052] In the above example, the first phase difference plate 12 and the second phase difference plate 14 are described as quarter-wave plates. However, the first phase difference plate 12 and the second phase difference plate 14 may be other wave plates or a combination thereof, as long as some of the light is absorbed by the polarizer plate 15 and the other light is transmitted through the polarizer plate 15. Furthermore, the first phase difference plate 12 and the second phase difference plate 14 may be other wave plates or a combination thereof, as long as some of the light is reflected by the first semi-transparent mirror 11 and the other light is transmitted through the first semi-transparent mirror 11.

[0053] The first semi-transparent mirror 11, the first phase difference plate 12, the second semi-transparent mirror 13, the second phase difference plate 14, and the polarizing plate 15 are held by a holding member (not shown) to maintain their relative positions. Air is interposed between the first semi-transparent mirror 11 and the first phase difference plate 12. Since the display device 1A does not have a member made of a resin material such as polymer between the first semi-transparent mirror 11 and the first phase difference plate 12, the risk of deformation of the first semi-transparent mirror 11 when the resin material is cured during the manufacturing process of the display device 1A, and misalignment between the first semi-transparent mirror 11 and the first phase difference plate 12 can be reduced. As a result, the deterioration of display quality can be reduced.

[0054] Since the optical system 10 is an on-axis type optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the space occupied by the optical system 10 can be reduced, and as a result, the display device 1A can be miniaturized. In addition, because the optical system 10 is on-axis, distortion and brightness unevenness of the virtual image V seen by the user 22 can be reduced, and the design of the optical system 10 is simplified.

[0055] Display device 1A may also include an optical element 9, similar to display device 1. In this case, display device 1A can allow the user 22 to view a stereoscopic image. The optical element 9 may be located between the display panel 2 and the first semi-transparent mirror 11, or after the polarizing plate 15 in the direction of light emission, or between the first semi-transparent mirror 11 and the first phase difference plate 12.

[0056] Next, another example of the display device 1A will be described. The display device 1A' in this example differs from the display device 1A described above in the configuration (shape) of the second semi-transparent mirror, but otherwise has the same configuration. Therefore, the same reference numerals are used for the same components, and detailed explanations are omitted.

[0057] The display device 1A' in this example comprises a display panel 2 and an optical system 10, as shown in Figure 5. The optical system 10 is composed of a first semi-transparent mirror 11, a first phase difference plate 12, a second semi-transparent mirror 13', a second phase difference plate 14, and a polarizing plate 15. That is, the optical system 10 consists of a pair of semi-transparent mirrors (first semi-transparent mirror 11, second semi-transparent mirror 13'), the first semi-transparent mirror 11, the first phase difference plate 12, the second semi-transparent mirror 13', the second phase difference plate 14, and the polarizing plate 15, arranged in this order in the direction of emission of display light from the display panel 2.

[0058] The second semi-transparent mirror 13' has a convex reflective surface 13'a. The second semi-transparent mirror 13' faces the first phase difference plate 12, and more specifically, the reflective surface 13'a faces the first phase difference plate 12. The second semi-transparent mirror 13' is also called a convex half-mirror. The second semi-transparent mirror 13' may transmit a portion of the incident light (for example, approximately 50%) and reflect the remainder (for example, approximately 50%). In this case, the reflective surface of the second semi-transparent mirror 13' diverges the light incident from the first semi-transparent mirror 11 side and reflects it, while the reflective surface of the first semi-transparent mirror 11 converges the light incident from the second semi-transparent mirror 13 side and reflects it.

[0059] The second semi-transparent mirror 13' may be composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent reflective layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film, etc.

[0060] The optical system 10 may be configured such that the focal length of the second semi-transparent mirror 13' is greater than the distance between the display panel 2 and the second semi-transparent mirror 13'. In other words, the optical system 10 may be configured such that the second semi-transparent mirror 13' projects a reduced virtual image Q' (see Figure 7) of the object (i.e., the display surface 2a). Furthermore, the optical system 10 may be configured such that the focal length of the first semi-transparent mirror 11 is greater than the distance between the virtual image Q' and the first semi-transparent mirror 11. In other words, the optical system 10 may be configured such that the first semi-transparent mirror 11 projects an enlarged virtual image V of the object (i.e., the virtual image Q'). In this case, it becomes possible to adjust the magnification ratio and projection distance of the virtual image V while reducing the thickness of the optical system 10 in the depth direction (Z-axis direction).

[0061] The first semi-transparent mirror 11, the first phase difference plate 12, the second semi-transparent mirror 13', the second phase difference plate 14, and the polarizing plate 15 are held by a holding member (not shown) to maintain their relative positions. Air is interposed between the first semi-transparent mirror 11 and the first phase difference plate 12. Since the display device 1A' does not have a member made of a resin material such as polymer between the first semi-transparent mirror 11 and the first phase difference plate 12, the risk of deformation of the first semi-transparent mirror 11 when the resin material is cured during the manufacturing process of the display device 1A' can be reduced, as can the displacement of the first semi-transparent mirror 11 and the first phase difference plate 12. As a result, the deterioration of display quality can be reduced.

[0062] Since the optical system 10 is an on-axis type optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the space occupied by the optical system 10 can be reduced, and as a result, the display device 1A' can be miniaturized. In addition, because the optical system 10 is on-axis, distortion and brightness unevenness of the virtual image V seen by the user 22 can be reduced, and the design of the optical system 10 is simplified.

[0063] The display device 1A' may also include an optical element 9, in which case it becomes possible to make the user 22 see the three-dimensional virtual image V.

[0064] Furthermore, according to the display device 1A' of this example, the optical system 10 can be made thinner in the depth direction (Z-axis direction), thus providing a thin display device. The thinning of the optical system 10 will be explained below with reference to Figures 6 and 7. The first semi-transparent mirror 11 of the display devices 1A and 1A' has a concave reflective surface 11a that reflects the display light emitted to the outside, so below, the first semi-transparent mirror 11 may be referred to as a concave mirror. The second semi-transparent mirror 13 of the display device 1A has a planar reflective surface 13a that reflects the display light emitted to the outside, so below, the second semi-transparent mirror 13 may be referred to as a planar mirror. The second semi-transparent mirror 13' of the display device 1A' has a convex reflective surface 13'a that reflects the display light emitted to the outside, so below, the second semi-transparent mirror 13' may be referred to as a convex mirror. In addition, the dimension of the optical system 10 in the depth direction (Z-axis direction) may be referred to as the thickness of the optical system 10.

[0065] Figure 6 illustrates the projection of the virtual image V in the display device 1A. In Figure 6, the illuminator 4 and optical components that do not contribute to the projection distance (virtual image distance) and magnification of the virtual image V (first phase difference plate 12, second phase difference plate 14, and polarizer plate 15) are omitted. Also, the concave mirror 11 is positioned in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be considered as "0". In the following explanation, the focal length of the concave mirror 11 is denoted as f, and the distance between the concave mirror 11 and the plane mirror 13 is denoted as a / 2. The distance a / 2 corresponds to the thickness of the optical system 10 of the display device 1A.

[0066] The display device 1A is configured to project a virtual image V by magnifying the virtual image Q of the display surface 2a, which is formed by the plane mirror 13, using the concave mirror 11. As shown in Figure 6, the virtual image Q is located on the opposite side of the concave mirror 11 from the plane mirror 13, and its distance from the plane mirror 13 is a / 2. The virtual image Q is an image of the display surface 2a magnified to 1x.

[0067] The virtual image distance b and virtual image magnification m of the virtual image V are expressed by the following equations (1) and (2), respectively. The virtual image distance b is the distance between the virtual image V and the concave mirror 11, and the virtual image magnification m is the magnification ratio of the virtual image V relative to the display surface 2a.

[0068] b = 1 / (1 / a - 1 / f) …(1) m = b / a …(2)

[0069] [Table 1]

[0070] Table 1 shows configuration examples 1 and 2 of the display device 1A. The units for focal length f, thickness a / 2, and virtual image distance b shown in Table 1 are "mm". Configuration examples 1 and 2 are configured to have a virtual image distance b of 200 mm and a virtual image magnification m of 2 or 3. As shown in Table 1, when the optical system 10 includes a plane mirror 13, in order to have a virtual image distance b of 200 mm and a virtual image magnification m of 2, the thickness a / 2 of the optical system 10 must be 50 mm (see Configuration Example 1), and in order to have a virtual image distance b of 200 mm and a virtual image magnification m of 3, the thickness a / 2 of the optical system 10 must be 33.5 mm (see Configuration Example 2).

[0071] Figure 7 illustrates the projection of the virtual image V in the display device 1A'. In Figure 7, the illuminator 4 and optical components that do not contribute to the projection distance (virtual image distance) and magnification of the virtual image V (first phase difference plate 12, second phase difference plate 14, and polarizer plate 15) are omitted. Also, the concave mirror 11 is positioned in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be considered as "0". In the following explanation, the focal length of the convex mirror 13' is denoted as f', the focal length of the concave mirror 11 as f'', and the distance between the concave mirror 11 and the convex mirror 13' as a' / 2. The distance a' / 2 corresponds to the thickness of the optical system 10 of the display device 1A'.

[0072] The display device 1A’ is configured to magnify the virtual image Q’ of the display surface 2a by the convex mirror 13’ and project it as a virtual image V by the concave mirror 11. As shown in FIG. 7, the virtual image Q’ is located on the opposite side of the concave mirror 11 with respect to the convex mirror 13’. The distance b’ between the virtual image Q’ and the convex mirror 13’ is expressed by the following formula (3). The magnification m’ of the virtual image Q’ with respect to the display surface 2a is expressed by the following formula (4). As is clear from formula (3), since b’ < a’ / 2, the magnification m’ of the virtual image Q’ is less than 1. Therefore, the virtual image Q’ is a reduced virtual image of the display surface 2a.

[0073] b’ = 1 / {1 / f’ + 1 / (a’ / 2)} …(3) m’ = b’ / (a’ / 2) …(4) The virtual image distance b’’ and the virtual image magnification m’’ of the virtual image V are respectively expressed by the following formulas (5) and (6). The virtual image distance b’’ is the distance between the virtual image V and the concave mirror 11, and the virtual image magnification m’’ is the magnification of the virtual image V with respect to the display surface 2a.

[0074] b’’ = 1 / {1 / (a’ / 2 + b’) - 1 / f’’} …(5) m’’ = (b’ / (a’ / 2)) × b’’ / (a’ / 2 + b’)…(6) [[ID=十六]]Table 2 shows Configuration Examples 3 and 4 of the display device 1A’. The units of the focal lengths f’, f’’, the thickness a’ / 2, and the virtual image distance b’’ shown in Table 2 are “mm”. Similar to Configuration Examples 1 and 2, Configuration Examples 3 and 4 are configured such that the virtual image distance b’’ is 200 mm and the virtual image magnification m’’ is 2 or 3. As shown in Table 2, when the optical system 10 includes the convex mirror 13’, with the optical system having a thickness a’ / 2 of 32 mm, similar to Configuration Example 1, the virtual image distance b’’ can be set to 200 mm and the virtual image magnification m’’ can be set to 2 (see Configuration Example 3). With the optical system having a thickness a’ / 2 of 25.5 mm, similar to Configuration Example 2, the virtual image distance b’’ can be set to 200 mm and the virtual image magnification m’’ can be set to 3 (see Configuration Example 4). Therefore, according to the display device 1A’, the optical system 10 can be thinned, and as a result, a thin display device can be provided.

[0075] [Table 2]

[0076] Given the values ​​of the virtual image distance b'', virtual image magnification m'', and thickness a' / 2, the display device 1A' can be designed to realize the optical system 10.

[0077] The design of the optical system 10 of the display device 1A' will be described below with reference to Figure 8. In Figure 8, as in Figure 7, the illuminator 4, the first phase difference plate 12, the second phase difference plate 14, and the polarizer 15 are omitted. Also, the concave mirror 11 is positioned in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be considered as "0". In the following description, the thickness of the optical system 10 will be a1, the distance between the convex mirror 13' and the virtual image Q' will be b1, and the distance between the concave mirror 11 and the virtual image V will be b2. Furthermore, the magnification ratio of the virtual image Q' relative to the display surface 2a will be m1, and the magnification ratio of the virtual image V relative to the virtual image Q' will be m2. In addition, the focal length of the convex mirror 13' will be f1, and the focal length of the concave mirror 11 will be f2.

[0078] The magnification M of the virtual image V on the display surface 2a is expressed as the product of magnification m1 and magnification m2, as shown in equation (7) below. Also, the distance a2 between the concave mirror 11 and the virtual image Q' is expressed as the sum of thickness a1 and distance b1, as shown in equation (8) below.

[0079] M = m1 × m2 …(7) a² = a¹ + b¹ …(8) If we define the thickness a1 of the optical system 10 as T and the virtual image distance (i.e., the distance b1 between the concave mirror 11 and the virtual image V) as D, then the magnification M is expressed by the following equation (9).

[0080] M = m1 × m2 =(b1 / a1)×(b2 / a2) =(b1 / T)×(D / a2) …(9) Substituting equation (10), which holds true for the distance b1 between the convex mirror 13' and the virtual image Q', into equation (9), we obtain equation (11).

[0081] 1 / a1 = 1 / b1 + 1 / f1 …(10) M = f1 × (1 + D / f2) / (T + f1) …(11) Furthermore, by substituting equation (12), which holds true for the distance b2 between the concave mirror 11 and the virtual image V, into equation (8), we obtain equation (13).

[0082] 1 / a² = 1 / b² + 1 / f² …(12) D×f2 / (D+f2)=T+T×f1 / (T+f1) …(13) From equations (9) and (13), the focal length f1 of the convex mirror 13' and the focal length f2 of the concave mirror 11 can be determined as shown in equations (14) and (15) below. In equation (15), A is expressed by the following equation (16).

[0083] f1=M×T×T / (D-2×M×T) …(14) f² = D × A / (MA) …(15) A = f1 / (T+f1) …(16) As can be seen from the above calculations, the display device 1A' can determine the focal lengths f1 and f2 (i.e., design the optical system 10) to achieve the magnification M, thickness T, and virtual image distance D, respectively, given these values.

[0084] In the display devices 1A and 1A', the optical path length of the light emitted from the display panel 2, passing through the first semi-transparent mirror 11, reflected by the second semi-transparent mirrors 13 and 13', and returning to the first semi-transparent mirror 11 may be smaller than the focal length of the first semi-transparent mirror 11. In this case, a virtual image V can be perceived by the user 22. In the display devices 1A and 1A', the optical path length of the light emitted from the display panel 2, passing through the first semi-transparent mirror 11, reflected by the second semi-transparent mirrors 13 and 13', and returning to the first semi-transparent mirror 11 may be larger than the focal length of the first semi-transparent mirror 11. In this case, a real image can be perceived by the user 22.

[0085] Next, a display device according to yet another embodiment of this disclosure will be described. The display device of this embodiment differs from the display device of the above embodiment in the configuration of the optical system, but otherwise has the same configuration. Therefore, the same reference numerals are used for the same components, and a detailed description is omitted.

[0086] As shown in Figure 9, the display device 1B of this embodiment includes a display panel 2 and an optical system 16.

[0087] The optical system 16 includes a first semi-transparent mirror 17, a first phase difference plate 18, a second semi-transparent mirror 19, a second phase difference plate 20, and a third semi-transparent mirror 21. The first semi-transparent mirror 17, the first phase difference plate 18, the second semi-transparent mirror 19, the second phase difference plate 20, and the third semi-transparent mirror 21 are arranged in this order in the direction of emission of display light from the display panel 2. The first semi-transparent mirror 17 and the third semi-transparent mirror 21 have the function of collecting or focusing light. In this embodiment, the first semi-transparent mirror 17 and the third semi-transparent mirror 21 have, for example, a greater degree of collecting, a greater degree of focusing, or an index expressed as the reciprocal of the focal length than other members of the optical system 16.

[0088] The first phase difference plate 18 is positioned opposite the first semi-transparent mirror 17. For example, the first phase difference plate 18 is positioned opposite the reflective surface 17a of the first semi-transparent mirror 17. The first semi-transparent mirror 17 has the function of collecting or focusing the light that is incident on and reflected by the reflective surface 17a of the first semi-transparent mirror 17. The first phase difference plate 18 is positioned away from the display surface 2a in the direction of emission of display light from the display panel 2. The second phase difference plate 20 is positioned away from the first phase difference plate 12 in the direction of emission of display light. The first phase difference plate 18 and the second phase difference plate 20 are quarter-wave plates.

[0089] The first semi-transparent mirror 17 is positioned between the display panel 2 and the first phase difference plate 18. The first semi-transparent mirror 17 may transmit a portion of the incident light and reflect the remainder. In this embodiment, the first semi-transparent mirror 17 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. The first semi-transparent mirror 17 may be a concave mirror having a concave reflective surface 17a facing the first phase difference plate 18, as shown in Figure 9. The first semi-transparent mirror 17 may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface 17a.

[0090] The first semi-transparent mirror 17 is composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal nanowires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The first semi-transparent mirror 17 can transmit light components vibrating in a direction perpendicular to the grid and can reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate facing the first phase difference plate 18. In this example, the metal nanowire grid provides the first semi-transparent mirror 11 with a reflective polarization function, but the first semi-transparent mirror 11 may be used as a simple half-mirror and a separate reflective polarizer may be provided.

[0091] The second semi-transparent mirror 19 is located between the first phase difference plate 18 and the second phase difference plate 20. The second semi-transparent mirror 13 may transmit a portion of the incident light (e.g., approximately 50%) and reflect the remainder (e.g., approximately 50%). The second semi-transparent mirror 19 faces the first phase difference plate 18 and, more specifically, may be a plane mirror having a reflective surface 19a facing the first phase difference plate 18 and a reflective surface 19b facing the second phase difference plate 20, as shown in Figure 9. The second semi-transparent mirror 19 is also called a plane half-mirror. The second semi-transparent mirror 19 may be integrated with at least one of the first phase difference plate 18 and the second phase difference plate 20, as shown in Figure 32.

[0092] The second semi-transparent mirror 19 may be composed of, for example, a substrate and a semi-transparent layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film. The first phase difference plate 18 and the second phase difference plate 20 may be fixed to the second semi-transparent mirror 19 with an optically transparent adhesive such as OCA (Optically Clear Adhesive). The adhesive may be a material with low retardation.

[0093] The third semi-transparent mirror 21 is positioned opposite to the surface of the second phase difference plate 20 that is opposite to the surface facing the second semi-transparent mirror 19. The third semi-transparent mirror 21 is positioned downstream of the second phase difference plate 20 in the direction of emission of display light from the display panel 2. The third semi-transparent mirror 21 may transmit a portion of the incident light and reflect the remainder. In this embodiment, the third semi-transparent mirror 21 may be configured to reflect S-wave polarized light and transmit P-wave polarized light. The third semi-transparent mirror 21 may be a concave mirror having a concave reflective surface 21a facing the second phase difference plate 20, as shown in Figure 9. The third semi-transparent mirror 21 has the function of focusing light that is incident on and reflected by the reflective surface 21a of the third semi-transparent mirror 21. The third semi-transparent mirror 21 may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface 21a of the third semi-transparent mirror 21.

[0094] The third semi-transparent mirror 21 is composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal nanowires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The third semi-transparent mirror 21 can transmit light components vibrating in a direction perpendicular to the grid and can reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate facing the second phase difference plate 20. In this example, the metal nanowire grid provides the third semi-transparent mirror 21 with a reflective polarization function, but the third semi-transparent mirror 21 may be used as a simple half-mirror and a separate reflective polarizer may be provided.

[0095] The optical function of the optical system 16 will now be described. In the display device 1B, the display light emitted from the display panel 2 may travel along path P1 or path P2 and be emitted to the outside. First, the light traveling along path P1 will be described. The S-wave polarized (first linearly polarized L1) display light emitted from the display panel 2 passes through the first semi-transparent mirror 17. The first linearly polarized L1 light passes through the first phase difference plate 18 and is converted into first circularly polarized C1 light. The first circularly polarized C1 light is incident on the second semi-transparent mirror 19. A portion of the first circularly polarized C1 light (for example, approximately 50%) is reflected by the second semi-transparent mirror 19 and converted into second circularly polarized C2 light. The second circularly polarized C2 light passes through the first phase difference plate 18 and is converted into second linearly polarized L2 light whose polarization direction is orthogonal to the first linearly polarized L1 (i.e., P-wave polarized). The light of the second linear polarization L2 is reflected by the first semi-transparent mirror 17 and converted into light of the third linear polarization L3, whose polarization direction is perpendicular to that of the first linear polarization L1 (i.e., it is P-wave polarized). The third linear polarization L3 is transmitted through the first phase difference plate 18 and converted into light of the third circular polarization C3. The light of the third circular polarization C3 is incident on the second semi-transparent mirror 19. A portion of the light of the third circular polarization C3 (for example, approximately 50%) is transmitted through the second semi-transparent mirror 19. The light of the third circular polarization C3 that has been transmitted through the second semi-transparent mirror 19 is transmitted through the second phase difference plate 20 and converted into light of the fourth linear polarization L4, whose polarization direction is perpendicular to that of the first linear polarization L1 (i.e., it is P-wave polarized). The light of the fourth linear polarization L4 is transmitted through the third semi-transparent mirror 21 and emitted to the outside.

[0096] Next, we will describe the light traveling along path P2. The remainder (for example, approximately 50%) of the first circularly polarized light C1 incident on the second semi-transparent mirror 19 passes through the second semi-transparent mirror 19. The first circularly polarized light C1 that has passed through the second semi-transparent mirror 19 passes through the second phase difference plate 20 and is converted into fifth linearly polarized light L5, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized light). The fifth linearly polarized light L5 is reflected by the third semi-transparent mirror 21 and is converted into sixth linearly polarized light L6, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized light). The sixth linearly polarized light L6 passes through the second phase difference plate 20 and is converted into fourth circularly polarized light C4. The fourth circularly polarized light C4 is incident on the second semi-transparent mirror 19. A portion of the light from the fourth circularly polarized light C4 (for example, approximately 50%) is reflected by the second semi-transparent mirror 19 and converted into light from the fifth circularly polarized light C5. The light from the fifth circularly polarized light C5 passes through the second phase difference plate 20 and is converted into light from the seventh linearly polarized light L7, whose polarization direction is perpendicular to the first linearly polarized light L1 (i.e., it is P-wave polarized). The light from the seventh linearly polarized light L7 passes through the third semi-transparent mirror 21 and is emitted to the outside.

[0097] As described above, in the display device 1B, the display light emitted from the display panel 2 travels along path P1 or path P2 and is emitted to the outside. As a result, the amount of light (luminance) emitted from the display device 1B is, for example, approximately 50% of the amount of light (luminance) of the display light emitted from the display panel 2. The display device 1B can improve light utilization efficiency and increase the luminance of the light emitted to the outside.

[0098] In the above example, the first phase difference plate 18 and the second phase difference plate 20 are described as quarter-wave plates. However, the first phase difference plate 18 and the second phase difference plate 20 may be other wave plates or a combination thereof, as long as some of the light is reflected by the first semi-transparent mirror 17 and the other light is transmitted through the first semi-transparent mirror 17. Furthermore, the first phase difference plate 18 and the second phase difference plate 20 may be other wave plates or a combination thereof, as long as some of the light is reflected by the third semi-transparent mirror 21 and the other light is transmitted through the third semi-transparent mirror 21.

[0099] The first semi-transparent mirror 17, the first phase difference plate 18, the second semi-transparent mirror 19, the second phase difference plate 20, and the third semi-transparent mirror 21 are held by a holding member (not shown) to maintain their relative positions. Air is interposed between the first semi-transparent mirror 17 and the first phase difference plate 18, and between the third semi-transparent mirror 21 and the second phase difference plate 20. Since the display device 1B does not have members made of resin material such as polymer between the first semi-transparent mirror 17 and the first phase difference plate 18, and between the third semi-transparent mirror 21 and the second phase difference plate 20, the risk of deformation of the first semi-transparent mirror 11, misalignment between the first semi-transparent mirror 11 and the first phase difference plate 12, etc. can be reduced. As a result, the deterioration of display quality can be reduced.

[0100] Since the optical system 16 is an on-axis type optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the space occupied by the optical system 16 can be reduced, and as a result, the display device 1B can be miniaturized. In addition, because the optical system 16 is on-axis, distortion and brightness unevenness of the virtual image V seen by the user 22 can be reduced, and the design of the optical system 16 is simplified.

[0101] The display device 1B may be configured such that the focal length of the first semi-transparent mirror 17 is equal to the focal length of the third semi-transparent mirror 21, and the second semi-transparent mirror 19 is a plane mirror. In this case, in the imaging device including the display device 1B, the virtual image formed by light traveling along path P1 and the virtual image formed by light traveling along path P2 substantially coincide, thereby improving the display quality.

[0102] The display device 1B is configured such that the optical path length of light emitted from the display panel 2, passing through the first semi-transparent mirror 17, reflected by the second semi-transparent mirror 19, and returning to the first semi-transparent mirror 17 is smaller than the focal length of the first semi-transparent mirror 17, and the optical path length of light emitted from the display panel 2, passing through the first semi-transparent mirror 17, passing through the second semi-transparent mirror 19, and returning to the third semi-transparent mirror 21 is also smaller than the focal length of the first semi-transparent mirror 17. In this case, the user 22 can perceive the virtual image V. The display device 1B is configured such that the optical path length of light emitted from the display panel 2, passing through the first semi-transparent mirror 17, reflected by the second semi-transparent mirror 19, and returning to the first semi-transparent mirror 17 is greater than the focal length of the first semi-transparent mirror 17, and the optical path length of light emitted from the display panel 2, passing through the first semi-transparent mirror 17, passing through the second semi-transparent mirror 19, and returning to the third semi-transparent mirror 21 is also greater than the focal length of the first semi-transparent mirror 17. In this case, the user 22 can perceive a real image.

[0103] Next, an imaging device according to one embodiment of the present disclosure will be described. The imaging device 100 of this embodiment includes display devices 1, 1A, 1A', and 1B. The imaging device 100 causes the user 22 to view the display light emitted from the display panel 2 as a virtual image V. Since the imaging device 100 includes display devices 1, 1A, 1A', and 1B, a compact imaging device can be realized, and the user 22 can view a virtual image V with improved display quality. In particular, when the imaging device 100 includes display device 1A', a thin imaging device can be realized. The imaging device 100 may also cause the user 22 to view the display light emitted from the display panel 2 as a real image.

[0104] The imaging device 100 may be mounted on the mobile body 23, as shown in Figure 10. The mobile body 23 may be a vehicle. Although Figure 10 shows the case where the vehicle is a passenger car, the vehicle is not limited to a passenger car and may be an automobile such as a truck, bus, or trolleybus. The positions of the display devices 1, 1A, 1A', and 1B are arbitrary within the mobile body 23. The display devices 1, 1A, 1A', and 1B may be located on the dashboard (instrument panel), inside the dashboard, on the ceiling of the vehicle compartment, on the A-pillar, etc. The imaging device 100 may share some of its components with other devices and parts provided by the mobile body 23.

[0105] The imaging device 100 may include a camera 102 that captures the scenery behind the moving object 23, as shown in Figure 10. The camera 102 may include, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging device 100 and the camera 102 are connected by at least one of wired communication and wireless communication. If the moving object 23 is a vehicle, the imaging device 100 and the camera 102 may be connected via a vehicle network such as a CAN (Control Area Network).

[0106] The imaging device 100 may be configured to display at least a portion of the captured image captured by the camera 102 on the display panel 2. In this case, the imaging device 100 can allow the user 22 (driver of the mobile vehicle 23) to view the scenery behind the mobile vehicle 23 as a virtual image V projected to a point further away from the imaging device 100. As a result, the user 22 can view the scenery behind the mobile vehicle 23 without significantly changing their gaze distance (point of gaze) while driving the mobile vehicle 23, making it easier to see the virtual image V and improving driving safety. Furthermore, since the imaging device 100 is a small imaging device, it does not occupy a large volume in the driver's cab of the mobile vehicle 23 even when placed there, and is less likely to interfere with driving. The imaging device 100, mounted on the mobile vehicle 23 and configured to allow the user 22 to view the scenery behind the mobile vehicle 23 as a virtual image V, is also called a digital rearview mirror.

[0107] The imaging device 100 may have display devices 1, 1A, 1A', and 1B equipped with optical elements 9 (see Figure 3). The imaging device 100 may be configured such that the display panel 2 displays a mixed image including a left-eye image and a right-eye image having parallax with respect to each other, emits display light for the left-eye image and display light for the right-eye image, and the optical elements 9 cause the display light for the left-eye image to reach the left eye of the user 22 and the display light for the right-eye image to reach the right eye of the user 22. In this case, the display light for the left-eye image and the display light for the right-eye image emitted from the display panel 2 can be perceived by the user 22 as a three-dimensional virtual image V.

[0108] The imaging device 100 may include a reflective optical element 101, as shown in Figure 11. The imaging device 100 may be configured such that the display devices 1, 1A, 1A', and 1B emit display light toward the reflective optical element 101, and the reflective optical element 101 directs a portion of the display light to the eyes of the user 22. If the imaging device 100 is mounted on a mobile body 23, the imaging device 100 may also use the windshield 24 of the mobile body 23 as the reflective optical element 101.

[0109] The imaging device 100 may be applied to a digital side mirror. In this case, as shown in Figure 12, the imaging device 100 may include a display device 1, 1A, 1A', 1B (hereinafter also referred to as the left-side display device 1L) located on the left A-pillar of the mobile body 23, a camera 102 (hereinafter also referred to as the left-side camera 102L) that captures the left rear of the mobile body 23, a display device 1, 1A, 1A', 1B (hereinafter also referred to as the right-side display device 1R) located on the right A-pillar of the mobile body 23, and a camera 102 (hereinafter also referred to as the right-side camera 102R) that captures the right rear of the mobile body 23. The left-side display device 1L may allow the user 22 to view the image of the left rear of the mobile body 23 captured by the left-side camera 102L as a virtual image V (hereinafter also referred to as the virtual image V2). The right-side display device 1R may display to the user 22 a virtual image V (hereinafter also referred to as virtual image V3) of the right rear of the moving object 23 captured by the right-side camera 102R. The image may be a moving image (also called a video) or a still image. The left-side camera 102L may be positioned in the same position as the left-side door mirror, and the right-side camera 102R may be positioned in the same position as the right-side door mirror.

[0110] The imaging device 100 may be configured such that the distance between the user 22's eye (or eyebox) and the virtual images V2 and V3 are approximately equal. In this case, the user 22 can check the situation to the left rear and right rear of the moving object 23 without significantly changing the fixation distance (the distance between the user 22's eye and the fixation point that the user 22 is fixating on). Therefore, driving safety can be improved. The eyebox refers to the real-space region where the user 22's eye is assumed to be located.

[0111] The imaging device 100 may be configured such that the distance between the user's eye (or eyebox) and each of the virtual images V1 to V3 is approximately equal to each other. In this case, the user 22 can check the situation immediately behind, to the left rear, and to the right rear of the moving object 23 without significantly changing the gaze distance. Therefore, driving safety can be improved.

[0112] The imaging device 100 may be applied to the cluster 29 in the dashboard of the mobile vehicle 23 (see Figure 12). In this case, the display devices 1, 1A, 1A', and 1B may allow the user 22 to view images showing driving information such as vehicle speed, engine rotation speed, and fuel level as virtual images V (hereinafter also referred to as virtual images V4).

[0113] The imaging device 100 may be applied to the CID (Center Information Display) 30 (see Figure 12). In this case, the display devices 1, 1A, 1A', and 1B are placed in the center cluster of the mobile body 23, and images showing information related to navigation, the in-vehicle environment (for example, settings for the air conditioning system, audio system, etc.) may be viewed by the user 22 as virtual images V (hereinafter also referred to as virtual images V5).

[0114] The imaging device 100 may be configured such that the distances between the user's eye (or eyebox) and the virtual images V4 and V5 are approximately equal. In this case, the user 22 can view information related to the operation of the moving object 23, as well as information related to navigation, the in-vehicle environment, etc., without significantly changing the viewing distance. Therefore, driving safety can be improved.

[0115] The imaging device 100 may be configured such that the distance between the user's eye (or eyebox) and each of the virtual images V1 to V5 is approximately equal. In this case, the user 22 can check the area directly behind, to the left rear, and to the right rear of the moving object 23 without significantly changing the gaze distance, and can also check information related to the operation of the moving object 23, navigation, and the in-vehicle environment. Therefore, driving safety can be improved.

[0116] The imaging device 100 may be applied to a PID (Passenger Information Display) 31 (see Figure 12). In this case, the display devices 1, 1A, 1A', and 1B are positioned near the passenger seat on the dashboard, and may display images of entertainment content and images showing information about audio equipment, air conditioning equipment, etc., as virtual images V for the passenger.

[0117] The imaging device 100 may be applied to the RSE (Rear Seat Entertainment) system 32 (see Figure 10). In this case, the display devices 1, 1A, 1A', and 1B are positioned on the backs of the front seats and may display images of entertainment content and images showing information about audio equipment, air conditioning equipment, etc., as virtual images V for passengers seated in the rear seats of the mobile body 23.

[0118] The display devices 1, 1A, 1A', and 1B may include a drive unit that adjusts the relative positions of the display panel 2, the semi-transparent mirror 6, the first semi-transparent mirrors 11 and 17, and the second semi-transparent mirrors 13, 13', and 21 in the depth direction. The image data of the display image displayed on the display panel 2 may include depth information representing the depth (distance in the depth direction) from a reference position. The reference position may be, for example, the position of the display panel 2. The virtual image display device 100 may be configured to adjust the distance between the display panel 2, the semi-transparent mirror 6, the first semi-transparent mirrors 11 and 17, and the second semi-transparent mirrors 13, 13', and 21 based on the depth information included in the image data, thereby changing the imaging position of the virtual image V in the depth direction. The drive unit may consist of, for example, an electric slider or an electric cylinder. The drive unit may be configured to allow the user 22 to manually adjust the relative positions between the display panel 2, the semitransparent mirror 6, the first semitransparent mirrors 11, 17 and the second semitransparent mirrors 13, 13', 21.

[0119] Other examples of the display devices of this disclosure are described below.

[0120] First, other examples of the display devices 1, 1A, 1A', and 1B will be described. Figures 13 and 14 are top views showing other examples of the display devices of this disclosure. In Figures 13 and 14, the first phase difference plate 5, the second phase difference plate 7, and the optical element 9 are omitted. In the following description, the display device 1 will be used as an example, but the same applies to the display devices 1A, 1A', and 1B.

[0121] Display device 1 may constitute part of imaging device 100 (digital rearview mirror). In a normal rearview mirror, that is, a rearview mirror using mirrors, the image seen by the user's left eye (also called the left-eye mirror image) and the image seen by the right eye (also called the right-eye mirror image) are different, and the user, through the cognitive function of the brain, recognizes the left-eye mirror image and the right-eye mirror image as mirror images seen by both eyes.

[0122] The display device 1 may be configured such that the virtual image projected within the user 22's field of view has a binocular visible area (virtual image V in Figures 13 and 14) that is visible to both the user 22's left eye 22L and right eye 22R, a left-eye visible area VLa that is visible only to the left eye 22L, and a right-eye visible area VRa that is visible only to the right eye 22R. In other words, if the virtual image seen by the left eye 22L is called the left-eye virtual image VL, and the virtual image seen by the right eye 22R is called the right-eye virtual image VR, then the left-eye virtual image VL may have a left-eye visible area VLa that is visible only to the left eye 22L, and the right-eye virtual image VR may have a right-eye visible area VRa that is visible only to the right eye 22R. Within the user 22's field of view, the left-eye visible area VLa is located to the right of the binocular visible area, and the right-eye visible area VRa is located to the left of the binocular visible area. Furthermore, as shown in Figure 13, the display device 1 may be configured such that the rightmost end 6R visible to the user 22 in the semi-transparent mirror 6 is located on a straight line connecting the left eye 22L and the rightmost end VLR of the left eye virtual image VL, and the leftmost end 6L visible to the user 22 in the semi-transparent mirror 6 is located on a straight line connecting the right eye 22R and the leftmost end VRL of the right eye virtual image VR.

[0123] With this configuration, just like with a normal rearview mirror, the range observed by the user 22 through the left eye virtual image VL is different from the range observed by the user 22 through the right eye virtual image VR. Therefore, just as when using a normal rearview mirror, the user 22 can recognize the left eye virtual image VL and the right eye virtual image VR as a virtual image V seen by both eyes 22L and 22R through the cognitive function of the brain. Thus, the risk of causing discomfort to the user 22 can be reduced.

[0124] The display device 1 may have a reflective polarizer 8 where the size of the reflective surface on the display surface 2a side is greater than or equal to the size of the display surface 2a. In this case, the reflective polarizer 8 can reflect the image of the entire display surface 2a toward the semitransparent mirror 6. The display device 1 may also be configured such that the virtual image (hereinafter also referred to as the display surface virtual image) VD when the image of the entire display surface 2a is projected into the user's field of view 22 encompasses the left eye virtual image VL and the right eye virtual image VR. In this case, a region R that appears in the field of view of the left eye 22L and the right eye 22R when the user's head moves can be formed, i.e., a viewing region R that can be peered into with the left eye 22L or the right eye 22R. As a result, the user 22 can see the left eye virtual image VL and the right eye virtual image VR, which change according to the movement of the head, just as when using a normal rearview mirror. Therefore, the risk of causing discomfort to the user 22 can be reduced. The size (dimensions) of the viewing region R can be controlled, for example, by controlling the size of the display surface 2a, the magnification of the virtual image, etc.

[0125] The size of the viewing area R can also be controlled by controlling the image display area (the area where the image is actually displayed) A on the display surface 2a. Increasing the image display area A expands the viewing area R. Decreasing the image display area A shrinks the viewing area R. When the image display area A becomes smaller than a predetermined threshold area, the viewing area R disappears, and the virtual image VL of the left eye and the virtual image VR of the right eye can be made to be the same virtual image.

[0126] As described above, the display device 1 may include a housing 27. The housing 27 may have an aperture 28 on its front side (user 22 side). Within the user 22's field of view, the virtual image V may be larger than the aperture 28. The size of the viewing area R can also be controlled by the size of the aperture 28. As shown in Figure 14, by appropriately designing the size of the aperture 28, it is possible to form a left-eye virtual image VL that includes an area that the right eye 22R cannot see, and a right-eye virtual image VR that includes an area that the left eye 22L cannot see. Furthermore, by appropriately designing the size of the aperture 28, it is possible to form a viewing area R and control the size of the viewing area R. When the size of the viewing area R is controlled by the aperture 28, the size of the semi-transparent mirror 6 only needs to be large enough to project the image of the entire display surface 2a into the user 22's field of view, which simplifies the design of the optical system 3.

[0127] The same applies to the display devices 1A, 1A', and 1B. The display devices 1A, 1A', and 1B may be configured such that the virtual image projected into the user's field of view has a binocular visible area that can be seen by the left eye 22L and the right eye 22R, a left-eye visible area that can be seen by the left eye 22L only, and a right-eye visible area that can be seen by the right eye 22R only. In this case, the risk of causing discomfort to the user 22 can be reduced. The display devices 1A and 1A' may be configured such that the right end of the first semi-transparent mirror 11 that can be seen by the user 22 is located on a straight line connecting the left eye 22L and the right end of the left-eye virtual image, and the left end of the first semi-transparent mirror 11 that can be seen by the user 22 is located on a straight line connecting the right eye 22R and the left end of the right-eye virtual image. Display device 1B may be configured such that the rightmost edges of the first semi-transparent mirror 17 and the third semi-transparent mirror 21, which are visible to the user 22, lie on a straight line connecting the left eye 22L and the rightmost edge of the virtual image of the left eye, and the leftmost edges of the first semi-transparent mirror 17 and the third semi-transparent mirror 21, which are visible to the user 22, lie on a straight line connecting the right eye 22R and the leftmost edge of the virtual image of the right eye. Display devices 1A, 1A', and 1B may be configured to have a viewing area R. Display devices 1A, 1A', and 1B may be configured such that the size of the viewing area R is controlled by the image display area A, or by the opening 28 of the housing 27.

[0128] Next, other examples of display devices 1, 1A, and 1A' will be described. Figures 15 and 16 are cross-sectional views illustrating other examples of display devices, Figures 17A to 17D and 18A to 18D are diagrams illustrating the optical system in other examples of display devices, and Figure 19 is a graph illustrating the optical system in other examples of display devices. In the following explanation, display device 1 will be used as an example, but the same applies to display devices 1A and 1A'.

[0129] The display device 1 is configured such that when the user 22 is positioned in front of the display device 1, the light of the second linearly polarized element L2 is reflected by the reflective polarizer 8 and not emitted from the display device 1 (see Figures 2 and 3). In other words, when viewed from the front of the display device 1, the display device 1 is configured such that the transmission axis of the polarizer on the front side (user 22 side) of the display panel 2 (liquid crystal panel) and the transmission axis of the reflective polarizer 8 are orthogonal (in a crossed nicol arrangement). As a result, as shown in Figures 2 and 3, the light of the second linearly polarized element L2 is not emitted from the display device 1, and the light of the fourth linearly polarized element L4 is emitted from the display device 1. In other words, the user 22 does not directly view the display panel 2, but views the reflected image reflected by the semitransparent mirror 6 as a virtual image V.

[0130] If the user 22 is not positioned directly in front of the display device 1, the crossed nicol arrangement of the transmission axis of the front polarizer plate of the display panel 2 and the transmission axis of the reflective polarizer plate 8 may be disrupted, causing some of the light of the second linearly polarized L2 to pass through the reflective polarizer plate 8. As a result, the user 22 may be able to see both the real image directly viewed from the display panel 2 and the virtual image V reflected by the semitransparent mirror 6, which may degrade the display quality of the display device 1.

[0131] As shown in Figures 15 and 16, the display device 1 in this example has a third phase difference plate 25 located between the display panel 2 and the reflective polarizer 8. This allows the relative angle between the transmission axis of the front polarizer of the display panel 2 and the transmission axis of the reflective polarizer 8 to be brought closer to a crossed nicol arrangement, even when the user 22 is not positioned directly in front of the display device 1, thereby reducing the degradation of the display quality of the display device 1. The third phase difference plate 25 may be a half-wave plate, a quarter-wave plate, an eighth-wave plate, a sixteenth-wave plate, or any other wave plate that imparts a phase difference. The optical axis of the third phase difference plate 25 may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer 8. The third phase difference plate 25 may be located between the second phase difference plate 7 and the reflective polarizer 8, or between the display panel 2 and the first phase difference plate 5.

[0132] The display device 1 in this example may further have a fourth phase difference plate 26 located between the display panel 2 and the reflective polarizer 8, as shown in Figures 15 and 16. In this case, even when the user 22 is not positioned in front of the display device 1, the relative angle between the transmission axis of the front polarizer of the display panel 2 and the transmission axis of the reflective polarizer 8 can be brought closer by the crossed nicol arrangement, further reducing the deterioration of the display quality of the display device 1. The fourth phase difference plate 26 may be a half-wave plate, a quarter-wave plate, an eighth-wave plate, a sixteenth-wave plate, etc., or any other wave plate that imparts a phase difference. The optical axis of the fourth phase difference plate 26 may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer 8. The fourth phase difference plate 26 may be located between the second phase difference plate 7 and the reflective polarizer 8, or between the display panel 2 and the first phase difference plate 5.

[0133] The third phase difference plate 25 and the fourth phase difference plate 26 only need to be positioned between the display panel 2 and the reflective polarizer 8, and their positions are arbitrary. If no other optical elements are located between the third phase difference plate 25 and the fourth phase difference plate 26, the third phase difference plate 25 and the fourth phase difference plate 26 may be in contact with each other. In this case, the thickness of the optical system 3 in the depth direction can be reduced. The optical axes of the third phase difference plate 25 and the fourth phase difference plate 26 are approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer 8, and the optical axis of the third phase difference plate 25 may be approximately perpendicular to the optical axis of the fourth phase difference plate 26.

[0134] The third phase difference plate 25 and the fourth phase difference plate 26 may be a quarter-wave plate and the other a half-wave plate. In this case, the deterioration of the display quality of the display device 1 can be effectively reduced. The third phase difference plate 25 and the fourth phase difference plate 26 may both be half-wave plates. In this case, the deterioration of the display quality of the display device 1 can be reduced more effectively.

[0135] Figures 17A, 17B, 17C, and 17D show a Poincaré sphere illustrating the optical functions (effects on the polarization state of light) of the third phase plate 25 and the fourth phase plate 26 when they are half-wave plates. Figures 17A and 17B illustrate the optical function of the third phase plate 25, and Figures 17C and 17D illustrate the optical function of the fourth phase plate 26. Figures 17A and 17C show the Poincaré sphere viewed from the north pole (S3 axis direction), and Figures 17B and 17D show the Poincaré sphere viewed from the side (S1 axis direction). In Figures 17A, 17B, 17C, and 17D, S LCD This shows the polarization state of the light immediately after it is emitted from the display panel 2. 25 This indicates the polarization state of light that has passed through the third phase difference plate 25, and S 26 This shows the polarization state of the light that has passed through the fourth phase difference plate 26. 26 This can be said to represent the polarization state of the light immediately before it enters the reflective polarizer 8. RP This indicates the polarization state of light that passes through the reflective polarizer 8 with substantially 100% transmittance, S AP is, S RPis the antipodal point (the point symmetric with respect to the center of the Poincaré sphere). S 26 is S AP is located at, or S AP is located in the vicinity of, it is possible to reduce the risk that light emitted from the display panel 2 and passing through the third retardation plate 25 and the fourth retardation plate 26 passes through the reflective polarizing plate 8. As a result, it is possible to reduce the risk that the user 22 visually recognizes the real image directly viewing the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0136] As shown in FIGS. 17C and 17D, when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates, S 26 is substantially located at S AP . Therefore, it is possible to reduce the risk that the user 22 visually recognizes the real image directly viewing the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0137] FIGS. 18A, 18B, 18C, and 18D are Poincaré spheres showing the optical functions of the third retardation plate 25 and the fourth retardation plate 26 when the third retardation plate 25 is a quarter-wave plate and the fourth retardation plate 26 is a half-wave plate. FIGS. 18A and 18B are diagrams for explaining the optical function of the third retardation plate 25, and FIGS. 18C and 18D are diagrams for explaining the optical function of the fourth retardation plate 26. FIGS. 18A and 18C show views of the Poincaré sphere seen from the north pole (S3 axis direction), and FIGS. 18B and 18D show views of the Poincaré sphere seen from the side (S1 axis direction). S LCD , S 25 , S 26 , S RP and S AP are as described above.

[0138] As shown in FIGS. 18C and 18D, when the third retardation plate 25 is a quarter-wave plate and the fourth retardation plate 26 is a half-wave plate, S 26 is located in the vicinity of S AP . Therefore, it is possible to reduce the risk that the user 22 visually recognizes the real image directly viewing the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0139] Figure 19 is a graph showing the relationship between the light transmittance of an optical system formed by inserting a third phase difference plate 25 and a fourth phase difference plate 26 between polarizers PP1 and PP2 whose transmission axes are mutually orthogonal, and the phase difference between the third phase difference plate 25 and the fourth phase difference plate 26. Figure 19 shows the results obtained by simulation. The incident light was green light with a wavelength λ of 550 nm. Polarizers PP1, 3rd phase difference plate 25, 4th phase difference plate 26, and PP2 are arranged in this order in the direction of propagation of the incident light. Polarizer PP1 is modeled after the front polarizer of the display panel 2, and polarizer PP2 is modeled after the reflective polarizer 8.

[0140] The solid line in the graph of Figure 19 shows the transmittance when the phase difference of the fourth phase difference plate 26 is fixed at 0 nm and the phase difference of the third phase difference plate 25 is varied, with the transmittance being minimum when the phase difference of the third phase difference plate 25 is approximately 275 nm (half the wavelength λ of the incident light). The dashed line in the graph of Figure 19 shows the transmittance when the phase difference of the third phase difference plate 25 is fixed at 270 nm and the phase difference of the fourth phase difference plate 26 is varied, with the transmittance being minimum when the phase difference of the fourth phase difference plate 26 is approximately 275 nm (half the wavelength of the incident light).

[0141] From the simulation results shown in the graph of Figure 19, it can be seen that when the third phase difference plate 25 and the fourth phase difference plate 26 of the display device 1 are half-wave plates, the risk of the user 22 directly viewing the real image on the display panel 2 can be effectively reduced, and the deterioration of the display quality of the display device 1 can be effectively reduced. Furthermore, even when the phase difference of the fourth phase difference plate 26 of the display device 1 is fixed at 0 nm (i.e., when only the third phase difference plate 25 is present), if the third phase difference plate 25 can impart a phase difference greater than 0 nm (i.e., non-zero) to the light incident on the third phase difference plate 25, the risk of the user 22 directly viewing the real image on the display panel 2 can be effectively reduced, and the deterioration of the display quality of the display device 1 can be effectively reduced.

[0142] The same applies to the display devices 1A and 1A'. The display devices 1A and 1A' may have a third phase difference plate 25 located between the display panel 2 and the polarizing plate 15. In this case, the risk of the user 22 directly viewing the real image on the display panel 2 can be reduced, and the deterioration of the display quality of the display devices 1A and 1A' can be reduced. The display devices 1A and 1A' may further have a fourth phase difference plate 26 located between the display panel 2 and the polarizing plate 15. In this case, the risk of the user 22 directly viewing the real image on the display panel 2 can be further reduced, and the deterioration of the display quality of the display devices 1A and 1A' can be further reduced. The third phase difference plate 25 and the fourth phase difference plate 26 may be a half-wave plate, a quarter-wave plate, an eighth-wave plate, a sixteenth-wave plate, etc., or other wave plates that impart a phase difference. The third phase difference plate 25 and the fourth phase difference plate 26 may be a quarter-wave plate and the other a half-wave plate. In this case, the degradation of the display quality of the display device 1 can be effectively reduced. The third phase difference plate 25 and the fourth phase difference plate 26 may both be half-wave plates. In this case, the degradation of the display quality of the display device 1 can be reduced more effectively. The third phase difference plate 25 and the fourth phase difference plate 26 may be located between the display panel 2 and the polarizing plate 15, and their positions are arbitrary. The third phase difference plate 25 and the fourth phase difference plate 26 may be located between the second phase difference plate 14 and the polarizing plate 15, or between the display panel 2 and the first phase difference plate 12. The optical axes of the third phase difference plate 25 and the fourth phase difference plate 26 may be approximately parallel or approximately perpendicular to the transmission axis of the polarizing plate 15. The optical axes of the third phase difference plate 25 and the fourth phase difference plate 26 are substantially parallel or substantially perpendicular to the transmission axis of the polarizing plate 15, and the optical axis of the third phase difference plate 25 may be substantially perpendicular to the optical axis of the fourth phase difference plate 26.

[0143] Next, other examples of the display devices 1, 1A, 1A', and 1B will be described. Figure 20 is a cross-sectional view showing another example of the display device 1A', and Figure 21 is a cross-sectional view showing another example of the display device 1A. Descriptions of the components or parts described in the above embodiments may be omitted.

[0144] The second semi-transparent mirror 13' of the display device 1A' may include a holographic optical element (HOE). In this case, as shown in Figure 20, the optical function of the second semi-transparent mirror 13' can be realized by a flat optical element, and the thickness of the second semi-transparent mirror 13' in the depth direction (Z-axis direction) can be reduced. As a result, the display device 1A' can be made smaller in the depth direction. Furthermore, because the second semi-transparent mirror 13' is a flat optical element, the distance between the second semi-transparent mirror 13' and the second phase difference plate 14 can be reduced, or the second semi-transparent mirror 13' and the second phase difference plate 14 can be brought into contact with each other, making it possible to further miniaturize the display device 1A' in the depth direction.

[0145] The first semi-transparent mirror 11 of the display device 1A' may include a HOE (Heat Edge Enclosure). In this case, as shown in Figure 20, the optical function of the first semi-transparent mirror 11 can be realized by a flat optical element, and the thickness of the first semi-transparent mirror 11 in the depth direction can be reduced. As a result, the display device 1A' can be made smaller in the depth direction. Furthermore, because the first semi-transparent mirror 11 is a flat optical element, the distance between the first semi-transparent mirror 11 and the display panel 2 can be reduced, or the first semi-transparent mirror 11 and the display panel 2 can be brought into contact with each other, making it possible to make the display device 1A' even smaller in the depth direction.

[0146] If the first semi-transparent mirror 11 does not have polarization selectivity, the amount of light emitted from the display device 1A' decreases, and the brightness of the virtual image V seen by the user 22 decreases. Therefore, the first semi-transparent mirror 11, including the HOE, may be configured to have polarization selectivity. For example, the first semi-transparent mirror 11, including the HOE, may have multiple metal nanowires (metal nanowire grids) formed on the surface facing the display panel 2 or the surface facing the first phase difference plate 12, which transmit S-wave polarized light and reflect P-wave polarized light, thereby achieving polarization selectivity. In this case, the decrease in brightness of the virtual image V seen by the user 22 can be reduced.

[0147] The first semi-transparent mirror 11 of the display device 1A may include a Homo-E (Hyper-Optical Enhancer). In this case, as shown in Figure 21, the optical function of the first semi-transparent mirror 11 can be realized by a flat optical element, and the thickness of the first semi-transparent mirror 11 in the depth direction can be reduced. As a result, the display device 1A can be made smaller in the depth direction. Furthermore, because the first semi-transparent mirror 11 is a flat optical element, the distance between the first semi-transparent mirror 11 and the display panel 2 can be reduced, or the first semi-transparent mirror 11 and the display panel 2 can be brought into contact with each other, making it possible to further miniaturize the display device 1A in the depth direction. The first semi-transparent mirror 11 including the Homo-E may have polarization selectivity. For example, the first semi-transparent mirror 11 including the Homo-E may have a plurality of fine metal wires formed on the surface facing the display panel 2 or the surface facing the first phase difference plate 12, which transmit S-wave polarized light and reflect P-wave polarized light, thereby achieving polarization selectivity. In this case, the reduction in brightness of the virtual image V seen by the user 22 can be reduced.

[0148] The semi-transparent mirror 6 of the display device 1 may include a HOE (Heat Edge Enclosure). In this case, the optical function of the semi-transparent mirror 6 can be realized by a flat optical element, and the thickness of the semi-transparent mirror 6 in the depth direction can be reduced. As a result, the display device 1 can be made smaller in the depth direction. Furthermore, because the semi-transparent mirror 6 is a flat optical element, the distance between the semi-transparent mirror 6 and the first phase difference plate 5 can be reduced, or the semi-transparent mirror 6 and the first phase difference plate 5 can be brought into contact with each other, making it possible to make the display device 1 even smaller in the depth direction.

[0149] The first semi-transparent mirror 17 of the display device 1B may include a Homo-E (Hyper-Optical Enhancer). In this case, the optical function of the first semi-transparent mirror 17 can be realized by a flat optical element, and the thickness of the first semi-transparent mirror 17 in the depth direction can be reduced. As a result, the display device 1B can be made smaller in the depth direction. Furthermore, because the first semi-transparent mirror 17 is a flat optical element, the distance between the first semi-transparent mirror 17 and the display panel 2 can be reduced, or the first semi-transparent mirror 17 and the display panel 2 can be brought into contact with each other, making it possible to further miniaturize the display device 1B in the depth direction. The first semi-transparent mirror 17 including the Homo-E may have polarization selectivity. For example, the first semi-transparent mirror 17 including the Homo-E may have a plurality of fine metal wires formed on the surface facing the display panel 2 or the surface facing the first phase difference plate 18 to achieve polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the reduction in brightness of the virtual image V seen by the user 22 can be reduced.

[0150] The third semi-transparent mirror 21 of the display device 1B may be configured to include a Homo-E (Hyper-Optical Envelope). In this case, the optical function of the third semi-transparent mirror 21 can be realized by a flat optical element, and the thickness of the third semi-transparent mirror 21 in the depth direction can be reduced. As a result, the display device 1B can be made smaller in the depth direction. The third semi-transparent mirror 21 including the Homo-E may have polarization selectivity. For example, the third semi-transparent mirror 21 including the Homo-E may have a plurality of fine metal wires formed on the surface facing the second phase difference plate 20 or on the surface opposite to the surface facing the second phase difference plate 20, thereby achieving polarization selectivity that reflects S-wave polarized light and transmits P-wave polarized light. In this case, the degradation of the quality of the virtual image V seen by the user 22 can be reduced, and the degradation of the brightness of the virtual image V can be reduced.

[0151] A holographic optical element may, for example, have an interference fringe pattern and be configured to diffract incident light in a predetermined direction.

[0152] The display device 1A' may be configured such that the second semi-transparent mirror 13' includes a Fresnel lens. In other words, the display device 1A' may have a Fresnel shape on the surface of the second semi-transparent mirror 13'. In this case, as shown in Figure 22, the optical function of the second semi-transparent mirror 13' can be realized by a substantially flat optical element with a reduced thickness (dimension in the depth direction) compared to a convex half-mirror, thereby reducing the thickness of the second semi-transparent mirror 13' in the depth direction. As a result, the display device 1A' can be made smaller in the depth direction. Furthermore, because the second semi-transparent mirror 13' is substantially flat, the distance between the second semi-transparent mirror 13' and the second phase difference plate 14 can be reduced, or the second semi-transparent mirror 13' and the second phase difference plate 14 can be brought into contact with each other, making it possible to further miniaturize the display device 1A' in the depth direction. The second semi-transparent mirror 13' including a Fresnel lens is also called a Fresnel half-mirror 13'.

[0153] The Fresnel half-mirror 13' may be composed of a Fresnel lens (Fresnel convex lens) 33 having a planar first surface 33a facing the second phase difference plate 14 and a Fresnel-shaped second surface 33b facing the first phase difference plate 12, as shown in Figure 23, and a semi-transparent reflective layer 34 located on the second surface 33b. The Fresnel shape has concentric grooves centered on a reference point 33c. The grooves include a surface substantially perpendicular to the first surface 33a and an inclined surface inclined with respect to the first surface 33a. The inclined surface may be a curved surface or a flat surface. The semi-transparent reflective layer 34 may be located on the inclined surface of the Fresnel shape. The semi-transparent reflective layer 34 may transmit a portion of the incident light (e.g., approximately 50%) and reflect the remainder (e.g., approximately 50%). The semi-transparent reflective layer 34 may be a thin metal film. The thin metal film may be made of a metallic material such as aluminum or chromium. The thin metal film may be formed by a vapor deposition method such as CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition).

[0154] The Fresnel half-mirror 13' has both an optical function as a lens and an optical function as a half-mirror. The optical function as a lens (e.g., focal length) is determined by the curvature and angle of inclination of the inclined surface, the refractive index of the material constituting the Fresnel lens 33, etc. The optical function as a half-mirror (e.g., focal length, transmittance, etc.) is determined by the curvature and angle of inclination of the inclined surface, the transmittance of the semi-transparent reflective layer 34, etc.

[0155] The Fresnel half-mirror 13' may have a transparent material layer formed on the second surface 33b of the Fresnel lens 33, which flattens the surface facing the second phase difference plate 14. The transparent material layer may be made of a material having substantially the same refractive index as the material constituting the Fresnel lens 33. The transparent material layer may be made of the same material as the material constituting the Fresnel lens 33.

[0156] The display device 1A' may be configured such that the first semi-transparent mirror 11 includes a Fresnel lens. In this case, as shown in Figure 22, the thickness of the first semi-transparent mirror 11 can be reduced, and as a result, the display device 1A' can be made smaller in the depth direction. Furthermore, since the first semi-transparent mirror 11 including the Fresnel lens is substantially flat, the distance between the first semi-transparent mirror 11 and the display panel 2 can be reduced, or the first semi-transparent mirror 11 and the display panel 2 can be brought into contact with each other, making it possible to make the display device 1A' even smaller in the depth direction. The first semi-transparent mirror 11 including the Fresnel lens is also called a Fresnel half mirror 11. The Fresnel half mirror 11 may have the same configuration as the Fresnel half mirror 13'. The Fresnel half mirror 11 may be configured including a Fresnel concave lens.

[0157] If the first semi-transparent mirror 11 is replaced with a Fresnel half-mirror 11 that does not have polarization selectivity, the amount of light emitted from the display device 1A' will decrease, and the brightness of the virtual image V seen by the user 22 will decrease. Therefore, the Fresnel half-mirror 11 may be configured to have polarization selectivity. For example, the Fresnel half-mirror 11 may have multiple metal nanowires (metal nanowire grids) formed on the surface facing the display panel 2 or the surface facing the first phase difference plate 12, which transmit S-wave polarized light and reflect P-wave polarized light, thereby achieving polarization selectivity. This can reduce the decrease in brightness of the virtual image V seen by the user 22.

[0158] The first semi-transparent mirror 11 of the display device 1A may be configured to include a Fresnel lens, as shown in Figure 23. In this case, the thickness of the first semi-transparent mirror 11 can be reduced, and as a result, the display device 1A can be made smaller in the depth direction. Furthermore, since the first semi-transparent mirror 11 including the Fresnel lens is substantially flat, the distance between the first semi-transparent mirror 11 and the display panel 2 can be reduced, or the first semi-transparent mirror 11 and the display panel 2 can be brought into contact with each other, making it possible to further miniaturize the display device 1A in the depth direction. The first semi-transparent mirror 11 including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transparent mirror 11 including the Fresnel lens may have a plurality of fine metal wires formed on the surface facing the display panel 2 or the surface facing the first phase difference plate 12 to achieve polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the reduction in brightness of the virtual image V seen by the user 22 can be reduced.

[0159] The semi-transparent mirror 6 of the display device 1 may include a Fresnel lens. In this case, the thickness of the semi-transparent mirror 6 can be reduced, and as a result, the display device 1 can be made smaller in the depth direction. Furthermore, since the semi-transparent mirror 6 including the Fresnel lens is substantially flat, the distance between the semi-transparent mirror 6 and the first phase difference plate 5 can be reduced, or the semi-transparent mirror 6 and the first phase difference plate 5 can be brought into contact with each other, making it possible to make the display device 1 even smaller in the depth direction.

[0160] The first semi-transparent mirror 17 of the display device 1B may include a Fresnel lens. In this case, the thickness of the first semi-transparent mirror 17 can be reduced, and as a result, the display device 1B can be made smaller in the depth direction. Furthermore, since the first semi-transparent mirror 17 including the Fresnel lens is substantially flat, the distance between the first semi-transparent mirror 17 and the display panel 2 can be reduced, or the first semi-transparent mirror 17 and the display panel 2 can be brought into contact with each other, making it possible to further miniaturize the display device 1B in the depth direction. The first semi-transparent mirror 17 including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transparent mirror 17 including the Fresnel lens may have a plurality of fine metal wires formed on the surface facing the display panel 2 or the surface facing the first phase difference plate 18 to achieve polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the reduction in brightness of the virtual image V seen by the user 22 can be reduced.

[0161] The third semi-transparent mirror 21 of the display device 1B may include a Fresnel lens. In this case, the thickness of the third semi-transparent mirror 21 can be reduced, and as a result, the display device 1B can be miniaturized in the depth direction. The third semi-transparent mirror 21 including the Fresnel lens may be configured to have polarization selectivity. For example, the third semi-transparent mirror 21 including the Fresnel lens may have a plurality of fine metal wires formed on the surface facing the second phase difference plate 20 or on the surface opposite to the surface facing the second phase difference plate 20, thereby achieving polarization selectivity that reflects S-wave polarized light and transmits P-wave polarized light. In this case, the degradation of the quality of the virtual image V seen by the user 22 can be reduced, and the degradation of the brightness of the virtual image V can be reduced.

[0162] The following describes the control of the viewing area in the imaging device 100 (display devices 1, 1A, 1A', 1B). In the following description, the imaging device 100 is assumed to be a digital rearview mirror (see Figure 10). The imaging device 100 is equipped with an angle sensor that detects the orientation of the display devices 1, 1A, 1A', 1B in a predetermined direction fixed to the mobile body 23. The predetermined direction may be, for example, the vehicle length direction of the mobile body 23, but is not limited thereto. The angle sensor may be a 3-axis angle sensor capable of detecting the orientation (roll, pitch, yaw) of the display devices 1, 1A, 1A', 1B. The mobile body 23 is equipped with a DMS (Driver Monitoring System), and the imaging device 100 is assumed to be able to communicate with and control the DMS. The DMS is capable of capturing an image of the face of a user 22 seated in the driver's seat of the mobile body 23, performing facial recognition of the user 22, and determining whether the user 22 is a known user or not. A known user may mean a user whose information (also called user information) such as features used for facial recognition, eye position during driving, and face orientation is stored in at least one of the memory units of the controller 43 and the DMS.

[0163] When user 22 is positioned directly in front of the display devices 1, 1A, 1A', and 1B, the size of the left viewing area PL and the size of the right viewing area PR are approximately the same (see Figure 25). Therefore, user 22 can see the virtual image V that changes according to the movement of their head, just as when using a normal rearview mirror. When user 22 is not positioned directly in front of the display devices 1, 1A, 1A', and 1B, the size of the left viewing area PL and the size of the right viewing area PR are not the same (see Figure 26). As a result, user 22 cannot see the virtual image V that changes according to the movement of their head, just as when using a normal rearview mirror, and may experience discomfort.

[0164] The control of the imaging device 100 by the controller 43 will be explained with reference to the flowchart shown in Figure 29. In the flowchart, "step" is abbreviated as "S," and within the chart, "positive" (computer flag = 1) in the decision control is represented by [Yes], and "negative" (computer flag = 0 zero) is represented by [No].

[0165] The flowchart in Figure 29 begins, for example, when user 22 sits in the driver's seat of the mobile vehicle 23 and starts the engine of the mobile vehicle 23.

[0166] In [S1], the DMS is controlled to confirm the user 22 seated in the driver's seat of the mobile unit 23 (user confirmation).

[0167] In [S2], facial recognition is performed on user 22, who is seated in the driver's seat, and the DMS is controlled to determine whether user 22 is a known user or not. In [S2], if user 22 is a known user [Yes], the process proceeds to [S3]. In [S2], if user 22 is not a known user [No], the process proceeds to [S7].

[0168] In [S3], user information of user 22 (information such as eye position and face orientation while driving) is obtained from the DMS.

[0169] In [S4], the display devices 1, 1A, 1A', and 1B are adjusted based on the user information acquired in [S3]. The adjustment of the display devices 1, 1A, 1A', and 1B may include changing the display area of ​​the display image on the display surface 2a of the display panel 2 according to the orientation of the display devices 1, 1A, 1A', and 1B, the position of the user's eyes and face orientation, etc. The change in the display area may be made into a non-display area 2b where an image is not displayed, as shown in Figure 27. As shown in Figure 27, by changing the display area of ​​the display image on the display surface 2a, even if the user 22 is not positioned directly in front of the display devices 1, 1A, 1A', and 1B, the size of the left viewing area PL and the size of the right viewing area PR can be made to be approximately the same, and as a result, the risk of the user 22 feeling uncomfortable can be reduced.

[0170] Adjusting the display devices 1, 1A, 1A', and 1B may include sliding (translating) at least one of the reflective polarizer 8, semi-transparent mirror 6, and display panel 2 in a direction perpendicular to the direction of emission of display light from the display panel 2, depending on the orientation of the display devices 1, 1A, 1A', and 1B, the position of the user 22's eyes, the orientation of their face, etc. By sliding at least one of the reflective polarizer 8, semi-transparent mirror 6, and display panel 2, the size of the left viewing area PL and the size of the right viewing area PR can be made to be approximately the same, as shown in Figure 28, and as a result, the likelihood of the user 22 feeling uncomfortable can be reduced. Furthermore, when sliding at least one of the reflective polarizer 8, semi-transparent mirror 6, and display panel 2, the size of the left viewing area PL and the right viewing area PR can be reduced compared to when the user 22 is positioned directly in front of the display devices 1, 1A, 1A', and 1B.

[0171] In [S5], the controller 43 receives instructions from the user 22 regarding whether or not readjustment of the display devices 1, 1A, 1A', and 1B is necessary. The imaging device 100 may be configured so that the user 22 can indicate that readjustment is necessary by operating a button or the like on the steering wheel. The imaging device 100 may also be configured so that the user 22 can indicate that readjustment is necessary by shaking the imaging device 100 and changing its orientation. The change in the orientation of the imaging device 100 may be detected by the three-axis angle sensor of the imaging device 100. If the controller 43 does not receive instructions from the user 22 within a predetermined time after starting to receive instructions from the user 22, it may determine that readjustment is not necessary. The predetermined time may be, for example, 3 to 10 seconds, but is not limited thereto.

[0172] If readjustment of display devices 1, 1A, 1A', and 1B is required in [S5] [Yes], proceed to [S6]. If readjustment of display devices 1, 1A, 1A', and 1B is not required in [S5] [No], terminate this flowchart. If readjustment of display devices 1, 1A, 1A', and 1B is required in [S5] [Yes], you may proceed to [S7].

[0173] In [S6], the controller 43 controls the DMS to detect user information of user 22 (information such as the position of the eyes and the direction of the face while driving), and also obtains user information of user 22 from the DMS.

[0174] In [S7], the display devices 1, 1A, 1A', and 1B are adjusted based on the user information obtained in [S6]. The adjustment of the display devices 1, 1A, 1A', and 1B may be the same as the adjustment of the display devices 1, 1A, 1A', and 1B in [S4].

[0175] In [S8], the system receives instructions from user 22 regarding whether or not readjustment of display devices 1, 1A, 1A', and 1B is necessary. The reception of user 22's instructions may be the same as in [S5]. In [S8], if readjustment of display devices 1, 1A, 1A', and 1B is necessary [Yes], the system returns to [S6]. In [S8], if readjustment of display devices 1, 1A, 1A', and 1B is not necessary [No], the system proceeds to [S9]. In [S8], if readjustment of display devices 1, 1A, 1A', and 1B is necessary [Yes], the system may return to [S7].

[0176] In [S9], the controller 43 stores user information of user 22 and information regarding the adjustment of display devices 1, 1A, 1A', 1B in at least one of the storage units of the controller 43 and the storage unit of the DMS, and this flowchart ends.

[0177] According to the flowchart in Figure 29, the viewing area in the digital rearview mirror can be efficiently controlled, reducing the likelihood of the user 22 feeling uncomfortable. The flowchart in Figure 29 can also be applied when the imaging device 100 constitutes a digital side mirror.

[0178] Other examples of the display devices 1, 1A, 1A', and 1B will be described. For components with the same configuration as those in the display devices 1, 1A, 1A', and 1B, the same reference numerals are used, and detailed explanations are omitted. The display device 1C in this example comprises a display panel 2, an optical system 35, and a housing 36, as shown in Figure 33.

[0179] The display panel 2 has a display surface 2a, on which a display image is displayed. The optical system 35 projects the display light emitted from the display panel 2 as a virtual image V into the user's field of view 22. The optical system 35 may be optical system 3 (see Figures 2, 3, 30), optical system 10 (see Figures 4, 5, 31), or optical system 16 (see Figures 9, 32). Figures 33 to 36 show the case where the optical system 35 is the optical system 3 shown in Figure 30.

[0180] The housing 36 houses the display panel 2 and the optical system 35. The housing 36 may hold the display panel 2 and the optical system 35. If the display device 1C includes an illuminator 4, the housing 36 may house and hold the illuminator 4. The housing 36 has a window (aperture) 37 that transmits light emitted from the optical system 35. The display device 1C may be arranged such that the window 37 and the display panel 2 overlap when viewed from the window 37 of the housing 36. Alternatively, the display device 1C may be arranged such that the window 37 and the optical system 35 overlap when viewed from the window 37 of the housing 36. Alternatively, the display device 1C may be arranged so that the display panel 2 and the optical system 35 overlap when viewed from the window 37 of the housing 36. In this case, the space occupied by the display device 1C can be reduced, and as a result, the display device 1C can be miniaturized. In the display device 1C, the display light emitted from the display panel 2 propagates substantially along one axis and is imaged as a virtual image V. Therefore, distortion and brightness unevenness of the virtual image V seen by the user 22 can be reduced, and the design of the optical system 35 becomes easier.

[0181] The housing 36 may have a light-transmitting plate 38 positioned in the window 37, as shown in Figures 33 and 34. The light-transmitting plate 38 may transmit light emitted from the optical system 35. The light-transmitting plate 38 at least partially blocks the window 37. The light-transmitting plate 38 may be made of, for example, glass, resin, or the like.

[0182] The optical system 35 (optical system 3) may have a third phase difference plate 25 and a fourth phase difference plate 26. The third phase difference plate 25 may be located on the surface of the second phase difference plate 7 facing the semi-transparent mirror 6. The fourth phase difference plate 26 may be located on the surface of the third phase difference plate 25 facing the semi-transparent mirror 6. This makes it possible to bring the relative angle between the transmission axis of the front polarizer plate of the display panel 2 and the transmission axis of the reflective polarizer plate 8 closer to a cross-nicol arrangement, even when the user 22 is not located in front of the display device 1C, thereby reducing the deterioration of the display quality of the display device 1C. The third phase difference plate 25 and the fourth phase difference plate 26 may be half-wave plates, but are not limited to this. The third phase difference plate 25 and the fourth phase difference plate 26 may be quarter-wave plates, eighth-wave plates, sixteenth-wave plates, etc., or other wave plates that impart phase difference. The third phase difference plate 25 and the fourth phase difference plate 26 may be waveplates that impart the same phase difference, or they may be waveplates that impart different phase differences. The optical axis of the third phase difference plate 25 may be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizer 8.

[0183] The optical system 35 (optical system 3) may have a moth-eye structured film 39 located on the surface of the first phase difference plate 5 facing the semi-transparent mirror 6. The moth-eye structured film 39 can attenuate the reflected light of light incident from the semi-transparent mirror 6 side. This reduces the amount of unwanted light and ambient light that are reflected by the first phase difference plate 5, emitted from the display device 1C, and incident on the user's eyes 22.

[0184] The optical system 35 (optical system 3) may have a moth-eye structure film 40 located on the surface of the fourth phase difference plate 26 facing the semi-transparent mirror 6. This reduces the amount of unwanted light and ambient light that are reflected by the fourth phase difference plate 26, emitted from the display device 1C, and incident on the user's eyes 22.

[0185] The reflective polarizing plate 8, the second phase difference plate 7, the third phase difference plate 25, the fourth phase difference plate 26, the moth-eye structure film 40, and the light-transmitting plate 38 may be integrated. This makes it possible to make the display device 1C thinner in the depth direction (Z-axis direction). In addition, deformation of the reflective polarizing plate 8, the second phase difference plate 7, the third phase difference plate 25, the fourth phase difference plate 26, the moth-eye structure film 40, and the light-transmitting plate 38 can be reduced.

[0186] The display device 1C may have a touch panel 41. The touch panel 41 may at least partially cover the window 37. The touch panel 41 may be mounted on the housing 36 as shown in Figures 35 and 36. The touch panel 41 may be mounted on the housing 36 so as to cover the window 37 on which the light-transmitting plate 38 is located, as shown in Figures 35 and 36. The touch panel 41 may cover the light-transmitting plate 38. The touch panel 41 is communicably connected to the controller 43 via a wired or wireless communication line. This allows the user 22 to operate the display device 1C via the touch panel 41. The touch panel 41 may be a known touch panel.

[0187] The display system 200 of this disclosure will now be described. As shown in Figure 39, the display system 200 comprises display devices 1, 1A, 1A', 1B, 1C and a camera 201. The display panels 2 of the display devices 1, 1A, 1A', 1B, 1C are capable of communicating with the camera 201 and display images captured by the camera 201. The display panels 2 and the camera 201 may be connected, for example, via wired, wireless, or CAN (Controller Area Network) connections.

[0188] The mobile body (vehicle) 23 of this disclosure is equipped with a display system 200. The display devices 1, 1A, 1A', 1B, 1C are small display devices and, even when placed in the driver's cab of the vehicle 23, do not occupy a large volume in the driver's cab and are unlikely to interfere with driving. Therefore, the user 22 can appropriately view a virtual image V or a real image. The display system 200 may be applied to the digital rearview mirror of the vehicle 23, or to the digital side mirrors 1L, 1R (see Figure 12). The display system 200 may also be applied to the cluster 29, CID (Center Information Display) 30, PID (Passenger Information Display) 31, RSE (Rear Seat Entertainment) system 32, etc. in the dashboard of the vehicle 23 (see Figures 10, 12).

[0189] According to this disclosure, it is possible to reduce the degradation of display quality in small display devices and improve light utilization efficiency. Furthermore, according to this disclosure, it is possible to provide a small imaging device that can allow users to clearly perceive virtual images.

[0190] Figure 40 is a perspective view showing a cross-section of yet another example of a display device according to one embodiment of the present disclosure.

[0191] The display device 501 may include a housing 36 having a viewing section with a window 37, a display panel 2 located inside the housing 36 and having a display surface 2a, and an optical system 35 located inside the housing 36 that forms a virtual image (image) V (see Figure 1) by imaging the display surface 2a. The cross-section of the display device 501 shown in Figure 40 is a diagram cut vertically along the direction of light emission from the display panel 2. In other words, it can also be said to be a diagram cut vertically along the arrangement direction of the display panel 2 and the optical system 35.

[0192] Although the above describes an example in which the viewing area has a window 37, the window 37 may also be the viewing area. Furthermore, the viewing area is not limited to the window 37, and may have other light-transmitting members, or it may be a space in which no members exist.

[0193] Figure 41 is a plan view of the image formed by the display device shown in Figure 40. The virtual image V may have a first region 401 that is visible from the viewing unit when viewed from a distance from the viewing unit and facing the viewing unit directly, and a second region 402 that is not visible from the viewing unit and is smaller than the first region 401. In the longitudinal direction of the virtual image V, the length of the virtual image V may be greater than the length of the viewing unit. Also, in the short direction of the virtual image V, the length of the virtual image V may be longer than the length of the viewing unit.

[0194] In this case, the second region 402 may be located on at least one of the left or right sides of the first region 401, or on at least one of the top and bottom of the first region 401, or the second region 402 may be located on all of the left and right sides and the top and bottom of the first region 401. In other words, the second region 402 only needs to be located on at least one of the left, right, top, or bottom of the first region 401. The first region 401 and the second region 402 may be calculated based on the size of the display image shown on the display panel 2, the magnification when this display image is projected onto the virtual image V, the positional relationship between the virtual image V and the viewing area, and the size of the viewing area.

[0195] The relative sizes of the first region 401 and the second region 402 can be compared by the area of ​​each region. For example, it is sufficient if the first region 401 comprises 60% or more of the virtual image V, and the second region 402 comprises 40% or less of the virtual image V. Furthermore, the first region 401 may have more than twice the area of ​​the second region 402.

[0196] When viewing the virtual image V from a distance from the viewing area, for example, it is sufficient to view it from a position where the background surrounding the housing 36 is within the viewer's direct field of vision. In this case, for example, the housing 36 and its surrounding background should be included within a 70-degree range in the up, down, left, and right directions from the viewer's position. In this embodiment, for example, the viewer may view the window 37 directly from a distance of 30 cm or more from the viewing area (window 37).

[0197] Figure 42 is a top view illustrating the act of viewing the viewing area directly. Viewing the viewing area directly may mean that the user 22 views the viewing area from above the normal 404 to the center 403 of the virtual image V. That is, for example, if the light-transmitting plate 38, which is a window 37, is installed at an angle to the housing 36, and the viewing area is viewed from above the normal 404, the viewer does not need to view the virtual image V from a position parallel to the inclined surface of the light-transmitting plate 38, but may view the virtual image V from a position non-parallel to the inclined surface of the light-transmitting plate 38. In this disclosure, when the viewing area is not viewed directly (when the virtual image V is viewed from a position off the normal 404), the virtual image V may have an area that is not visible from the viewing area that is larger than the area that is visible from the viewing area, or it may not have an area that is not visible from the viewing area.

[0198] According to the above configuration, since the user 22, who is viewing the viewing unit from a distance and directly facing it, can see most of the virtual image V, it becomes easy to recognize the content of the video that is flowing as a virtual image V.

[0199] Furthermore, the second region 402, which should be located above and below the first region 401, may be smaller than the second region 402, which should be located on the side of the first region 401. In this case, the second region 402 may be present on the side of the first region 401, but it is not necessary for the second region 402 to be present above and below the first region 401. In this embodiment, the second region 402 is located above, below, and on the side of the first region 401, and the first portion 406 of the second region 402, which is located above and below the first region 401, is set to be smaller than the second portion 407 of the second region 402, which is located on the side of the first region 401.

[0200] The second region 402 can be seen from the viewing area when viewed from a distance and without directly facing the viewing area. The first part 406 of the second region 402 can be seen from the window 37 when viewed from above or below, and the second part 407 of the second region 402 can be seen from the window 37 when viewed from the side. In this case, the user 22 can more easily see the virtual image V.

[0201] Furthermore, the vertical magnification of the virtual image V may be smaller than the horizontal magnification of the virtual image V. For example, the horizontal magnification of the virtual image V may be twice or more than the vertical magnification. With the above configuration, a virtual image V with a large width can be formed, making it easier for the user 22 to see the virtual image V.

[0202] Figure 43 is a diagram comparing the length of the viewing area and the length of the semi-transparent mirror in the longitudinal direction of the viewing area. The optical system 35 is positioned within the housing 36 so as to overlap with the display panel 2 when viewing the inside of the housing 36 from the window 37. The optical system 35 also has a semi-transparent mirror 6, and the length L37 of the viewing area (window 37) in the longitudinal direction WL of the viewing area (window 37) may be greater than the length L6 of the semi-transparent mirror 6. If the viewing area (window 37) is parallel to the XY plane, the longitudinal direction WL of the viewing area (window 37) may be, for example, the X direction or the Y direction. If the viewing area (window 37) is not parallel to the XY plane, the longitudinal direction WL of the viewing area (window 37) may be, for example, along the X direction or the Y direction, and the length L37 of the viewing area (window 37) will be the X component or the Y component. According to the above configuration, the visible area of ​​the virtual image V can be increased.

[0203] Furthermore, as shown in Figure 42, the angle θa between the first straight line 410 connecting the first end 408 in the longitudinal direction of the virtual image V and the center 409 of the window 37, and the second straight line 412 connecting the second end 411 in the longitudinal direction of the virtual image V and the center 409 of the window 37, may be 70 degrees or less.

[0204] An example of an angle θa is shown in Figure 42. Figure 42 is an example where the longitudinal direction of the virtual image V is the X direction. The longitudinal direction of the virtual image V is not limited to the X direction, but may also be the Y direction or other direction parallel to the XY plane.

[0205] Since the effective field of view of a human being is approximately 70 degrees, the above configuration makes it easy for the user 22 to recognize the content of the video that is flowing as a virtual image V.

[0206] The virtual image V may have a size such that more than half of it is visible from the viewing area when viewed by the user 22 at a position further away from the focal point of the optical system 35. This makes it easier for the user 22 to recognize the content of the image flowing as the virtual image V. When the optical system 51 collects or focuses light using the semi-transparent mirror 6, the focal point of the optical system 35 is synonymous with the focal point of the semi-transparent mirror 6. Furthermore, when the optical system 51 collects or focuses light using multiple optical elements, the focal point of the optical system 35 is a position based on the combined focal length of the multiple optical elements.

[0207] The optical system 35 has a semi-transparent mirror 6 having a reflective surface 6a, and the optical path length from the display panel 2 to the reflective surface 6a of the semi-transparent mirror 6 entering from the viewing side may be two-thirds or less of the focal length Lf6 of the semi-transparent mirror 6 (see Figure 40). In this case, for example, referring to Figure 2, the optical path length from the display panel 2 to the reflective surface 6a of the semi-transparent mirror 6 may be the sum of the optical path lengths of the first linearly polarized display light L1, the first circularly polarized light C1, the second linearly polarized light L2, the third linearly polarized light L3, and the second circularly polarized light C2. Figure 40 shows the focal point f6 of the semi-transparent mirror 6. With the above configuration, the magnification of the virtual image V can be suppressed, and therefore the decrease in the resolution of the virtual image V can be reduced for the user 22.

[0208] Figures 44 and 45 are diagrams illustrating two straight lines connecting a pair of endpoints of an image and a pair of endpoints of a semi-transparent mirror in a cross-sectional view. A pair of endpoints refers to, for example, two endpoints that form the outer edge of a component or member such as an image or semi-transparent mirror, located on opposite sides or corners and aligned in the left-right or up-down direction. The cross-sections in Figures 44 and 45 are cross-sections obtained when cutting in the left-right or up-down direction. That is, examples of such cross-sectional views include the ZX cross-sectional view shown in Figure 44 and the YZ cross-sectional view shown in Figure 45. The cross-section corresponding to these cross-sectional views may be a plane parallel to the Z-axis direction.

[0209] In this embodiment, the optical system 35 has a semi-transparent mirror 6, and in a cross-sectional view, the angle θb between the two straight lines 417 and 418 connecting the pair of endpoints 413 and 414 of the virtual image V to the pair of endpoints 415 and 416 of the semi-transparent mirror 6 may be acute. Alternatively, the angle θb between the two straight lines 417 and 418 connecting the pair of endpoints 413 and 414 of the virtual image V to the pair of endpoints 415 and 416 of the semi-transparent mirror 6 may be less than or equal to the effective field of view (70 degrees).

[0210] Furthermore, if the first angle is defined as the angle between the two lines connecting each of the pair of endpoints of the virtual image V, which are aligned horizontally, and each of the pair of endpoints of the semitransparent mirror 6, which are aligned horizontally, and the second angle is defined as the angle between the two lines connecting each of the pair of endpoints of the virtual image V, which are aligned vertically, and each of the pair of endpoints of the semitransparent mirror 6, which are aligned vertically, then the first angle may be greater than the second angle.

[0211] Furthermore, the optical system 35 includes a semi-transparent mirror 6, and in a cross-sectional view, the intersection point 419 of two straight lines 417 and 418, which connect the endpoints 413 and 414 of the virtual image V to the endpoints 415 and 416 of the semi-transparent mirror 6, may be located outside the display device 501 with respect to the window 37.

[0212] Furthermore, when the intersection of two lines connecting each of the pair of endpoints of the virtual image V aligned horizontally and the pair of endpoints of the semitransparent mirror 6 aligned horizontally is defined as the first intersection, and the intersection of two lines connecting each of the pair of endpoints of the virtual image V aligned vertically and the pair of endpoints of the semitransparent mirror 6 aligned vertically is defined as the second intersection, the first intersection may be located closer to the display device 501 than the second intersection.

[0213] Furthermore, the two straight lines connecting each of the pair of endpoints of the virtual image V, which are aligned horizontally, to the pair of endpoints of the semi-transparent mirror 6, which are aligned horizontally, may pass through the viewing area, as shown in Figures 44 and 45. Also, the two straight lines connecting each of the pair of endpoints of the virtual image V, which are aligned vertically, to the pair of endpoints of the semi-transparent mirrors 6 and 11, which are aligned vertically, may pass through the viewing area, as shown in Figures 44 and 45.

[0214] The optical system 35 has a semi-transparent mirror 6 positioned within the housing 36 so as to overlap with the display panel 2 when the inside of the housing 36 is viewed from the viewing area (window 37). The semi-transparent mirror 6 may have a planar shape similar to the display image displayed on the display panel 2. That is, when the semi-transparent mirror 6 is viewed from the direction of the viewing area (window 37), the semi-transparent mirror 6 may have a planar shape similar to the display image. Specifically, in this embodiment, since the display panel 2 displays a rectangular display image, the semi-transparent mirror 6 has a rectangular planar shape. This makes it easy to associate the shape of the virtual image V with the shape of the display surface 2a, thereby reducing the risk of the image on the display surface 2a being missing in the virtual image V.

[0215] The display device 501 may further include a shielding wall 421 that shields at least a portion of the end 420 of the semi-transparent mirror 6, as shown in Figure 40. In other words, the shielding wall 421 may be provided so as to hide the edge of the semi-transparent mirror 6 when the user 22 views the virtual image V from the viewing area. The shielding wall 421 may be provided on the inner surface of the housing 36. In this embodiment, the shielding wall 421 may be positioned to shield the upper end of the semi-transparent mirror 6. The shielding wall 421 may be positioned to shield the lower end of the semi-transparent mirror 6. The shielding wall 421 may be positioned to shield the right end of the semi-transparent mirror 6. The shielding wall 421 may be positioned to shield the left end of the semi-transparent mirror 6.

[0216] Furthermore, the display device 501 may have shielding portions located at the ends 420 of the semi-transparent mirrors 6 and 11. Specifically, as shown in Figure 46, the light absorption rate at the end 420 of the semi-transparent mirror 6 may be set higher than the light absorption rate at other parts of the semi-transparent mirror 6. For example, the end 420 may be painted black, covered with a light-shielding film or other material, or made of a highly light-shielding material. Each of these reduces the risk of light scattering near the end 420, thereby reducing the risk of unintended luminescence appearing on the virtual image V due to this light scattering.

[0217] The size of the virtual image V may be larger than the outer dimensions of the viewing surface 422 on which the window 37 of the housing 36 is located. Alternatively, the size of the virtual image V may be less than twice the size of the viewing surface 422. The magnification of the virtual image V may be less than three times. Each of these factors ensures that the magnification of the virtual image V is sufficiently suppressed, allowing the user 22 to perceive a virtual image V with sufficiently high resolution.

[0218] Furthermore, the size of the virtual image V may be larger than the housing 36. Specifically, the size of the virtual image V may be larger than the surface of the housing 36 that includes the viewing surface 422. Also, the outer edge of the virtual image V may be located outside the housing 36. In this case, for example, the virtual image V may have a third region located outside the housing 36 with respect to the surface of the housing 36 that includes the viewing surface 422. Also, for example, the virtual image V may have a third region located outside the housing 36 when viewed from a distance from the window 37 and facing the window 37 directly. The third region may be located on the left-right side of the virtual image V, on the top or bottom of the virtual image V, or on the sides, top and bottom of the virtual image V. In this case, the viewing area of ​​the housing 36 of the display device 501 can be maximized.

[0219] The window 37 is elongated in the vertical or horizontal direction, the display panel 2 displays an image, the optical system 35 forms an image of the image to create a virtual image V, and the image may be elongated along the longitudinal direction of the window 37. In other words, the viewing area has an elongated shape that is elongated along the longitudinal direction of the displayed image on the display panel 2. Furthermore, the semi-transparent mirrors 6 and 11 have an elongated shape that is elongated along the longitudinal direction of the displayed image on the display panel 2. Furthermore, the semi-transparent mirrors 6 and 11 have an elongated shape that is elongated along the longitudinal direction of the viewing area.

[0220] In the above explanation with reference to Figures 40-46, a display device 501 in which the optical system 35 is the optical system 3 (see Figures 2, 3, and 30) was used as an example. However, the optical system 35 of the display device 501 is not limited to the optical system 3, but may be the optical system 10 (see Figures 4, 5, and 31) described in other embodiments, or it may be the optical system 16 (see Figures 9 and 32). In this case, each component of the optical system 10 or each component of the optical system 16 may appropriately correspond to each component of the optical system 35. For example, if the optical system 35 corresponds to the optical system 10, the semi-transparent mirror 6 may correspond to, for example, the first semi-transparent mirror 11. Also, if the optical system 35 corresponds to the optical system 16, the semi-transparent mirror 6 may correspond to, for example, the first semi-transparent mirror 17 and the second semi-transparent mirror 19.

[0221] From the above, the display device 501 may be interpreted as either (first configuration) or (second configuration) below.

[0222] (First configuration) A display device 501 comprising a display panel 2 having a display surface 2a, and an optical system 35 that forms a virtual image V by imaging the display surface 2a, wherein the optical system 35 comprises a reflective polarizer 8, a first phase difference plate 5 located between the display panel 2 and the reflective polarizer 8, a second phase difference plate 7 located between the first phase difference plate 5 and the reflective polarizer 8, and a semi-transparent mirror 6 located between the first phase difference plate 5 and the second phase difference plate 7 and having a reflective surface 6a, wherein the optical path length from the light emitted from the display panel 2 to the reflective surface 6a of the semi-transparent mirror 6 is two-thirds or less of the focal length Lf6 of the semi-transparent mirror 6 (see Figure 40). The first configuration corresponds to an example where the optical system 35 is an optical system 3, and an example thereof may be shown in Figure 40. The semi-transparent mirror 6 may be rectangular. This makes it easy to associate the shape of the virtual image V with the shape of the display surface 2a, thereby reducing the risk of the image on the display surface 2a being missing in the virtual image V.

[0223] (Second configuration) A display device 501 comprising a display panel 2 having a display surface 2a, and an optical system 35 that forms a virtual image V by imaging the display surface 2a, wherein the optical system 35 comprises a first phase difference plate 12 and a second phase difference plate 14, a first semi-transparent mirror 11 located between the display panel 2 and the first phase difference plate 12 and having a reflective surface (first reflective surface) 11a, and a second semi-transparent mirror 13 located between the first phase difference plate 12 and the second phase difference plate 14 and having a reflective surface (second reflective surface) 13a, wherein the optical path length from the display panel 2 to the reflective surface 11a of the first semi-transparent mirror 11 is two-thirds or less of the focal length of the first semi-transparent mirror 11. The second configuration corresponds to an example where the optical system 35 is an optical system 10, and one example of this may be the display device 501 shown in Figure 40 in which the optical system 3 is replaced with an optical system 10 (see Figure 4). For example, referring to Figure 4, the optical path length from the display panel 2 to the reflective surface 11a of the first semi-transparent mirror 11 may be the sum of the optical path lengths of the first linearly polarized display light L1, the first circularly polarized light C1, the second circularly polarized light C2, and the second linearly polarized light L2. The first semi-transparent mirror 11 may be rectangular. This makes it easy to associate the shape of the virtual image V with the shape of the display surface 2a, thereby reducing the risk of the image of the display surface 2a being missing in the virtual image V.

[0224] Figure 47 is a block diagram showing another example of a display device according to one embodiment of the present disclosure. Figure 48 is a plan view of the image formed by the display device shown in Figure 47. In addition to Figures 47 and 48, Figures 40 to 46 are also referred to here.

[0225] The display device 501 may include a housing 36 having a window 37, a display panel 2 located inside the housing 36 that displays an image showing supplementary information, an optical system 35 located inside the housing 36 that forms an image to create a virtual image V, and a control unit 423 that controls the image on the display panel 2. The virtual image V may have a first region 401 that is visible from the window 37 and a second region 402 that is not visible from the window 37 when viewed from a distance and facing the window 37 directly. The control unit 423 may control the image so that a lot of supplementary information is displayed in the first region 401.

[0226] The control unit 423 may also be a controller 43 (see Figure 1). The control unit 423 may, but is not limited to, control the display panel 2 to control the image, and may also control various components such as the optical system 35 and the illuminator 4 (see Figure 1). The control unit 423 can display supplementary information in the first region 401 by displaying the supplementary information in a desired area. The size of the first region 401 can be estimated based on the image magnification and the size of the viewing area.

[0227] The virtual image V is, for example, an image formed from the video captured by the camera 201 (see Figure 39) when the display device 501 is mounted on the mobile body 23. In this case, the supplementary information is information other than the video from the camera 201, and may be various types of information related to the user 22 or the mobile body 23. The supplementary information may also be information to supplement the user 22's operation of the mobile body 23. More specifically, the supplementary information may be information such as instructions or warnings for the user 22. That is, the supplementary information may be an arrow indicating the direction the mobile body 23 should move or a warning mark indicating the presence of a pedestrian. This makes it possible to realize a display device 501 in which the supplementary information can be seen when viewed from a distance from the window 37 and facing the window 37 directly. The supplementary information may be displayed not only in the first area 401 but also in the second area 402. In this case, it is sufficient that the first area 401 is controlled to be able to display more supplementary information. Also, the density of supplementary information may be higher in the first area 401 than in the second area 402.

[0228] A mobile body (vehicle) 23 equipped with a display device 501 is also included in the scope of this disclosure (see Figure 39). This makes it possible to realize a mobile body 23 that has the same effect as the display device 501.

[0229] Figures 49 and 50 are cross-sectional views showing examples of the configuration of a display device according to the present disclosure. In Figures 49 and 50, some components not relevant to the description may be omitted. Also, the description of components or parts equivalent to those in the above examples may be omitted.

[0230] The display device 501 comprises a display panel 2 and an optical system 3. The optical system 3 may include a first phase difference plate 5, a semi-transparent mirror 6, a second phase difference plate 7, and a reflective polarizing plate 8. Alternatively, the optical system 3 may be arranged in the order of the first phase difference plate 5, semi-transparent mirror 6, second phase difference plate 7, and reflective polarizing plate 8 from the display panel 2 side.

[0231] The functions of the optical system 3 in FIGS. 49 and 50 are the same as those of the optical system 3 in FIG. 2 from the time when the display light of the first linearly polarized light L1 passes through the first retardation plate 5 until the light of the fourth linearly polarized light L4 passes through the reflective polarizing plate 8 and is emitted to the outside.

[0232] In the present embodiment, the reflective polarizing plate 8 can condense or converge the light that is incident on and reflected by the reflective polarizing plate 8. Specifically, the reflective polarizing plate 8 has a concave shape located on the display panel 2 side. As a result, the reflective polarizing plate 8 can condense or converge the light. It can also be said that the reflective polarizing plate 8 has a concave shape that is open on the display panel 2 side. Also, it can be said that the reflective polarizing plate 8 has a concave shape that is recessed toward the side opposite to the display panel 2. Also, it can be said that the reflective polarizing plate 8 has a convex shape that protrudes toward the side opposite to the display panel 2 (user 22 side). As shown in FIG. 49, the reflective polarizing plate 8 may be disposed on the inner surface of a base material 424 having a concave shape on the display panel 2 side.

[0233] In the present embodiment, the semi-transmissive mirror 6 can condense or converge the light that is incident on and reflected by the semi-transmissive mirror 6. Specifically, the semi-transmissive mirror 6 has a concave shape located on the side opposite to the display panel 2 (user 22 side). As a result, the semi-transmissive mirror 6 can condense or converge the light. It can also be said that the semi-transmissive mirror 6 has a concave shape that is open on the user 22 side. Also, it can be said that the semi-transmissive mirror 6 has a concave shape that is recessed toward the display panel side. Also, it can be said that the semi-transmissive mirror 6 has a convex shape that protrudes toward the display panel 2 side.

[0234] As shown in FIG. 50, at least one of the reflective polarizing plate 8 and the semi-transmissive mirror 6 may be flat. Also, in this case, at least one of the reflective polarizing plate 8 and the semi-transmissive mirror 6 may be a holographic optical element, or at least one of the surface shapes of the reflective polarizing plate 8 and the semi-transmissive mirror 6 may have a Fresnel shape. In this case, the reflective polarizing plate 8 may be disposed on the surface of a flat base material 424. The base material 424 may be made of glass as an example of its material.

[0235] Each member of the optical system 3 in FIGS. 49 and 50 may respectively correspond to each member of the optical system 3 in FIG. 2. Each member of the optical system 10 in FIGS. 51 and 52 may respectively correspond to each member of the optical system 10 in FIG. 4, including the corresponding relationship between the reflective polarizing plate 425 and the first semi-transmissive mirror 11.

[0236] Each of FIGS. 51 and 52 is a cross-sectional view showing an example of the configuration of the display device according to an embodiment of the present disclosure. In each of FIGS. 51 and 52, illustration of members not related to the description may be omitted. Also, description of configurations or parts equivalent to the above example may be omitted.

[0237] The display device 501 includes a display panel 2 and an optical system 10. The optical system 10 may include a reflective polarizing plate 425, a first retardation plate 12, a second semi-transmissive mirror 13, a second retardation plate 14, and a polarizing plate 15. Also, the optical system 10 may be arranged in the order of the reflective polarizing plate 425, the first retardation plate 12, the second semi-transmissive mirror 13, the second retardation plate 14, and the polarizing plate 15 from the display panel 2 side. The reflective polarizing plate 425 may have substantially the same function as the first semi-transmissive mirror 11 (see FIG. 4).

[0238] The function of the optical system 10 in each of FIGS. 51 and 52 is the same as the function of the optical system 10 in FIG. 4 until the display light of the first linearly polarized light L1 passes through the reflective polarizing plate 425 having substantially the same function as the first semi-transmissive mirror 11, and then the light of the fourth linearly polarized light L4 passes through the polarizing plate 15 and is emitted to the outside while the light of the fifth linearly polarized light L5 is absorbed by the polarizing plate 15.

[0239] In this embodiment, the reflective polarizing plate 425 can collect or focus the light that is incident on and reflected by the reflective polarizing plate 425. Specifically, the reflective polarizing plate 425 has a concave shape located on the opposite side from the display panel 2 (the user 22 side). As a result, the reflective polarizing plate 425 can collect or focus the light. It can also be said that the reflective polarizing plate 425 has a concave shape that opens towards the user 22 side. It can also be said that the reflective polarizing plate 425 has a concave shape that is recessed toward the display panel 2 side. It can also be said that the reflective polarizing plate 425 has a convex shape that protrudes toward the display panel 2 side. As shown in Figure 51, the reflective polarizing plate 425 may be arranged on the inner surface of the base material 426 which has a concave shape toward the user 22 side.

[0240] In this embodiment, the second semi-transparent mirror 13 can collect or focus the light that is incident on and reflected by the second semi-transparent mirror 13. Specifically, the second semi-transparent mirror 13 has a concave shape located on the display panel 2 side. As a result, the second semi-transparent mirror 13 can collect or focus the light. It can also be said that the second semi-transparent mirror 13 has a concave shape that opens towards the display panel 2 side. Furthermore, it can also be said that the second semi-transparent mirror 13 has a concave shape that is recessed toward the opposite side of the display panel 2 (towards the user 22 side). Furthermore, it can also be said that the second semi-transparent mirror 13 has a convex shape that protrudes toward the user 22 side.

[0241] As shown in Figure 52, at least one of the reflective polarizing plate 425 and the second semi-transparent mirror 13 may be flat. In this case, at least one of the reflective polarizing plate 425 and the second semi-transparent mirror 13 may be a holographic optical element, or the surface shape of at least one of the reflective polarizing plate 425 and the second semi-transparent mirror 13 may have a Fresnel shape. In this case, the reflective polarizing plate 425 may be disposed on the surface of a flat substrate 426. Glass is one example of a material for the substrate 426.

[0242] The display panel 2 and optical system 3 (see Figures 49 and 50) and the display panel 2 and optical system 10 (see Figures 51 and 52) may be interpreted as including a display system 427, a concave mirror section 428, and a concave mirror section 429, respectively. The concave mirror sections 428 and 429 may transmit a portion of the incident light and reflect the remainder. The concave mirror sections 428 and 429 are not limited to concave mirrors themselves, and may have the function of a concave mirror optically regardless of their shape.

[0243] Figures 53A and 53B illustrate the optical functions of the display devices shown in Figures 49 to 52, respectively. As shown in Figure 53A, the concave mirror portion 429 forms an image on the display surface 2a of the display system 427, forming a virtual image V429 that is magnified relative to the display surface 2a. Then, as shown in Figure 53B, the concave mirror portion 428 forms an image on the virtual image V429, forming a virtual image V428 that is magnified relative to the virtual image V429. This makes it easier to adjust the magnification ratio of the virtual image V relative to the display surface 2a.

[0244] According to the display device 501 shown in Figures 49 to 52, the focal lengths of each concave mirror section 428 and 429 can be made longer, which is convenient when the spacing between components is narrowed. Also, since the aspect ratio of the Fresnel shape can be set small, molding and deposition are easy. For each of the display panel 2 and optical system 3 (see Figures 49 and 50) and the display panel 2 and optical system 10 (see Figures 51 and 52), two adjacent components may or may not be in contact with each other, at least in part.

[0245] Figure 54 shows an example of various dimensions of the display device shown in Figure 34. All dimensions in Figure 54 may be in the direction of the optical axis of the light incident on the optical system 3 or 10. The inequality sign "<" in Figure 54 means that the stated dimension may be less than the actual dimension. The spatial dimension (reference numeral 6-40) may be the distance from the part of the semi-transparent mirror 6 that is closest to the display panel 2 on the exit side to the moth-eye structure film 40. The distance between the display panel and the reflective polarizer (including members 2 and 8) (reference numeral 2-8) may be the sum of the thickness of the display panel 2, the distance between the display panel 2 and the reflective polarizer 8, and the thickness of the reflective polarizer 8. The amount of curvature (reference numeral 6-6) may be the dimension from the part of the semi-transparent mirror 6 that is closest to the display panel 2 on the incident side to the semi-transparent mirror 6 to the part of the semi-transparent mirror 6 that is closest to the second phase difference plate 7 on the exit side to the semi-transparent mirror 6.

[0246] Although embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments described above.

[0247] For example, the above describes a display device equipped with a display panel, but is not limited to this. For example, the present disclosure may be implemented as a display panel housing device in which the housing has an opening into which a display panel can be inserted. In this case, the display panel housing device may have the same configuration as the display device, except that the housing has an opening into which a display panel can be inserted from the outside.

[0248] Furthermore, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the gist of this disclosure. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. It should also be noted that these modifications, alterations, or alterations are included in the scope of this disclosure.

[0249] The display device of the present disclosure can be implemented in the following aspects (1) to (71).

[0250] (1) A display panel that emits linearly polarized display light, A first retardation plate facing the display panel, A second retardation plate disposed apart from the first retardation plate, A reflective polarizing plate that transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light, A semi-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a reflective surface facing the second retardation plate, The first retardation plate and the second retardation plate are quarter-wave plates, the display device. <​​​​​​​​​​​​​​​​​​​​​​​​

[0255] (5) The display device according to (4) above, wherein one of the third phase difference plate and the fourth phase difference plate is a quarter-wave plate and the other is a half-wave plate.

[0256] (6) The display device according to (4) above, wherein the third phase difference plate and the fourth phase difference plate are half-wave plates.

[0257] (7) The display device according to any one of (1) to (6) above, wherein the reflective surface of the semi-transparent mirror is concave.

[0258] (8) The display device according to any one of (1) to (6) above, wherein the semi-transparent mirror is a flat optical element composed of holographic optical elements.

[0259] (9) The display device according to any one of (1) to (6) above, wherein the semi-transparent mirror includes a Fresnel lens.

[0260] (10) The display device according to (8) or (9) above, wherein the semitransparent mirror is integrated with at least one of the first phase difference plate and the second phase difference plate.

[0261] (11) A display panel that emits linearly polarized display light, A first phase difference plate facing the display panel, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate, The polarizing plate is located opposite the second phase difference plate, A display device in which the first phase difference plate and the second phase difference plate are quarter-wave plates.

[0262] (11') A display panel that emits display light, A first phase difference plate facing the display panel, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate, The polarizing plate is located opposite the second phase difference plate, A display device comprising a first phase difference plate and a second phase difference plate that converts the display light into a first polarization that is transmitted through the polarizing plate and a second polarization that is transmitted less through the polarizing plate than the first polarization.

[0263] (12) The display device according to (11) above, wherein the second reflective surface is a convex surface protruding toward the first phase difference plate side.

[0264] (13) The display device according to (11) or (12) above, wherein air is interposed between the first semi-transparent mirror and the first phase difference plate.

[0265] (14) The display device according to any one of (11) to (13) above, comprising a third phase difference plate disposed between the display panel and the polarizing plate.

[0266] (15) The display device according to (14), further comprising a fourth phase difference plate disposed between the display panel and the polarizing plate.

[0267] (16) The display device according to (15) above, wherein one of the third phase difference plate and the fourth phase difference plate is a quarter-wave plate and the other is a half-wave plate.

[0268] (17) The display device according to (15) above, wherein the third phase difference plate and the fourth phase difference plate are half-wave plates.

[0269] (18) The display device according to any one of (11) to (17) above, wherein the first reflective surface is concave.

[0270] (19) The display device according to any one of (11) to (17) above, wherein the first semi-transparent mirror and the second semi-transparent mirror are flat optical elements composed of holographic optical elements.

[0271] (20) The display device according to any one of (11) to (17) above, wherein the first semi-transparent mirror and the second semi-transparent mirror include a Fresnel lens.

[0272] (21) The display device according to (19) or (20), wherein the first semitransparent mirror is integrated with at least one of the display panel and the first phase difference plate.

[0273] (22) The display device according to (19) or (20) above, wherein the second semitransparent mirror is integrated with at least one of the first phase difference plate and the second phase difference plate.

[0274] (23) A display panel that emits linearly polarized display light, A first phase difference plate facing the display panel, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate. A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate. The system comprises a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate, A display device in which the first phase difference plate and the second phase difference plate are quarter-wave plates.

[0275] (23') A display panel that emits display light, A first phase difference plate that transmits the aforementioned display light, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate. A display device comprising: a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate.

[0276] (24) The display device according to (23), wherein air is interposed between the first semi-transparent mirror and the first phase difference plate, and between the third semi-transparent mirror and the second phase difference plate.

[0277] (25) The display device according to (23) or (24) above, wherein the first reflective surface and the fourth reflective surface are concave.

[0278] (26) The display device according to (23) or (24) above, wherein the first semi-transparent mirror and the third semi-transparent mirror are flat optical elements composed of holographic optical elements.

[0279] (27) The display device according to (23) or (24) above, wherein the first semi-transparent mirror and the third semi-transparent mirror include a Fresnel lens.

[0280] (28) The display device according to (26) or (27), wherein the first semitransparent mirror is integrated with at least one of the display panel and the first phase difference plate.

[0281] (29) The display device according to any one of (26) to (28) above, wherein the second semitransparent mirror is integrated with the second phase difference plate.

[0282] (30) The display light includes the display light for the left eye image and the display light for the right eye image, The display device according to any one of (1) to (29) above, further comprising an optical element that defines the direction of each ray of the display light for the left eye image and the display light for the right eye image.

[0283] (31) An imaging device including a display device as described in any of (1) to (30) above.

[0284] (32) The imaging device according to (31) above, wherein the virtual image projected into the user's field of view includes a binocular visible area that can be seen by both the user's left and right eyes, a left-eye visible area that can be seen by the left eye only, and a right-eye visible area that can be seen by the right eye only.

[0285] (33) Display panel and, An optical system that projects the display light emitted from the display panel as a virtual or real image, The system comprises a housing that accommodates the display panel and the optical system, The housing has a window that transmits light emitted from the optical system, A display device in which, when the window of the housing is viewed, the window, the optical system, and the display panel are arranged to overlap.

[0286] (34) The display device according to (33) above, wherein the housing has a light-transmitting plate arranged in the window.

[0287] (35) The display device according to (34) above, further comprising a touch panel mounted on the housing so as to cover the light-transmitting plate.

[0288] (36) The display device according to any one of (1) to (30) and (33) to (35) above, wherein the display panel has a display surface and is equipped with an irradiator that irradiates light onto the surface of the display panel opposite to the display surface.

[0289] (37) The display device according to (36), further comprising a controller having a function for controlling the image displayed on the display panel and at least one of the irradiator.

[0290] (38) A vehicle equipped with the display device described in (37) above.

[0291] (39) A display panel that emits linearly polarized display light, A first phase difference plate facing the display panel, A second phase difference plate is positioned at a distance from the first phase difference plate, A reflective polarizing plate that transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light, It comprises a semi-transparent mirror positioned between the first phase difference plate and the second phase difference plate, and having a reflective surface facing the second phase difference plate, The first phase difference plate and the second phase difference plate are quarter-wave plates. A display device wherein the optical path length of light emitted from the display panel, passing through the semitransparent mirror, reflected by the reflective polarizing plate, and reaching the semitransparent mirror is less than the focal length of the semitransparent mirror.

[0292] (40) A display panel that emits linearly polarized display light, A first phase difference plate facing the display panel, A second phase difference plate is positioned at a distance from the first phase difference plate, A reflective polarizing plate that transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light, It comprises a semi-transparent mirror positioned between the first phase difference plate and the second phase difference plate, and having a reflective surface facing the second phase difference plate, The first phase difference plate and the second phase difference plate are quarter-wave plates. A display device wherein the optical path length of light emitted from the display panel, passing through the semitransparent mirror, reflected by the reflective polarizing plate, and reaching the semitransparent mirror is greater than the focal length of the semitransparent mirror.

[0293] (41) A display panel that emits linearly polarized display light, A first phase difference plate that transmits the aforementioned display light, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate, The polarizing plate is located opposite the second phase difference plate, The first phase difference plate and the second phase difference plate are quarter-wave plates. A display device wherein the optical path length of light emitted from the display panel, passing through the first semitransparent mirror, reflected by the second semitransparent mirror, and reaching the first semitransparent mirror is less than the focal length of the first semitransparent mirror.

[0294] (42) A display panel that emits linearly polarized display light, A first phase difference plate that transmits the aforementioned display light, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate, The polarizing plate is located opposite the second phase difference plate, The first phase difference plate and the second phase difference plate are quarter-wave plates. A display device wherein the optical path length of light emitted from the display panel, passing through the first semitransparent mirror, reflected by the second semitransparent mirror, and returning to the first semitransparent mirror is greater than the focal length of the first semitransparent mirror.

[0295] (43) A display panel that emits linearly polarized display light, A first phase difference plate that transmits the aforementioned display light, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate. The system comprises a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate, The first phase difference plate and the second phase difference plate are quarter-wave plates. A display device wherein the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror, reflected by the second semi-transparent mirror, and reaching the first semi-transparent mirror is smaller than the focal length of the first semi-transparent mirror, and the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror, passing through the second semi-transparent mirror, and reaching the third semi-transparent mirror is smaller than the focal length of the first semi-transparent mirror.

[0296] (44) A display panel that emits linearly polarized display light, A first phase difference plate that transmits the aforementioned display light, A second phase difference plate is positioned at a distance from the first phase difference plate, A first semi-transparent mirror is disposed between the display panel and the first phase difference plate and has a first reflective surface facing the first phase difference plate, A second semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate. The system comprises a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate, The first phase difference plate and the second phase difference plate are quarter-wave plates. A display device wherein the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror, reflected by the second semi-transparent mirror, and reaching the first semi-transparent mirror is greater than the focal length of the first semi-transparent mirror, and the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror, passing through the second semi-transparent mirror, and reaching the third semi-transparent mirror is greater than the focal length of the first semi-transparent mirror.

[0297] (45) A display panel that emits display light, The system comprises a convex lens through which the aforementioned display light is transmitted, A display device in which the optical path length from the display panel to the convex lens is smaller than the focal length of the convex lens.

[0298] (46) A display panel that emits display light, The system comprises a convex lens through which the aforementioned display light is transmitted, A display device in which the optical path length from the display panel to the convex lens is greater than the focal length of the convex lens.

[0299] (47) A display device as described in any of (1) to (30), (33) to (37), and (39) to (46) above, Equipped with a camera, The display panel is capable of communicating with the camera and displays images captured by the camera, forming a display system.

[0300] (48) A vehicle equipped with the display system described in (47) above.

[0301] (49) A housing having a viewing section, A display panel located inside the aforementioned housing and having a display surface, An optical system located within the housing and forming an image on the display surface, Equipped with, The image is a display device having a first region visible from the viewing unit and a second region smaller than the first region that is not visible from the viewing unit, when viewed from a distance from the viewing unit and facing the viewing unit directly.

[0302] (50) The second region is located above, below, and to the side of the first region. The display device according to (49) above, wherein the portion of the second region located above and below the first region is smaller than the portion of the second region located on the side of the first region.

[0303] (51) The display device according to (49) above, wherein the image is a virtual image and the magnification of the image in the vertical direction is less than twice the magnification of the image in the horizontal direction.

[0304] (52) The optical system is positioned within the housing so as to overlap with the display panel when viewed from the viewing section into the housing, and has a semi-transparent mirror. The display device according to (49) above, wherein the length of the viewing portion along its longitudinal direction is greater than the length of the semi-transparent mirror along its longitudinal direction.

[0305] (53) The display device according to (49) above, wherein the angle between a first straight line connecting the first end of the image in the longitudinal direction and the center of the viewing area and a second straight line connecting the second end of the image in the longitudinal direction and the center of the viewing area is 70 degrees or less.

[0306] (54) The display device according to (49) above, wherein the image is of a size that allows more than half of it to be visible from the viewing area when viewed from a distance greater than the focal position of the image.

[0307] (55) The optical system has a semi-transparent mirror having a reflective surface, The display device according to (49) above, wherein the optical path length from the display panel to the reflective surface of the semitransparent mirror is two-thirds or less of the focal length of the semitransparent mirror.

[0308] (56) The display device described in (49) above, wherein the viewing section is a window.

[0309] (57) The optical system has a semi-transparent mirror, The display device according to (49) above, wherein, in a cross-sectional view, the angle between the two straight lines connecting the endpoints of the image and the endpoints of the semitransparent mirror is an acute angle.

[0310] (58) The optical system has a semi-transparent mirror, The display device according to (49) above, wherein, in a cross-sectional view, the intersection of two straight lines connecting the endpoints of the image and the endpoints of the semi-transparent mirror is located outside the display device with respect to the viewing area.

[0311] (59) The display device according to (49), wherein the optical system is positioned within the housing so as to overlap with the display panel when the inside of the housing is viewed from the viewing section, and has a rectangular semi-transparent mirror.

[0312] (60) The display device according to (52) above, further comprising a shielding wall that shields the end of the semi-transparent mirror.

[0313] (61) The display device according to (60), wherein the shielding wall is positioned to shield the upper end, lower end, right end, and left end of the semi-transparent mirror.

[0314] (62) The display device according to (52), wherein the end of the semi-transparent mirror has a higher light absorption rate than the other end of the semi-transparent mirror.

[0315] (63) The display device according to (49) above, wherein the size of the image is larger than the outer dimensions of the viewing surface on which the viewing portion of the housing is located, and less than twice the size of the viewing surface.

[0316] (64) The display device according to (49) above, wherein the magnification of the image is less than 3 times.

[0317] (65) The viewing section is elongated in the vertical or horizontal direction, The aforementioned display panel displays an image, The optical system forms an image by focusing the image, The display device described in (49) above, wherein the image is a long image along the longitudinal direction of the viewing section.

[0318] (66) A display panel having a display surface, An optical system that forms an image by imaging the aforementioned display surface, Equipped with, The optical system described above is Reflective polarizing plate and A first phase difference plate is positioned between the display panel and the reflective polarizing plate, A second phase difference plate is positioned between the first phase difference plate and the reflective polarizing plate, It includes a semi-transparent mirror located between the first phase difference plate and the second phase difference plate and having a reflective surface, A display device in which the optical path length from the display panel to the reflective surface of the semi-transparent mirror is two-thirds or less of the focal length of the semi-transparent mirror.

[0319] (67) The display device according to (66) above, wherein the semi-transparent mirror is rectangular.

[0320] (68) A display panel having a display surface, An optical system that forms an image by imaging the aforementioned display surface, Equipped with, The optical system described above is A first phase difference plate and a second phase difference plate, A first semi-transparent mirror, which is located between the display panel and the first phase difference plate and has a first reflective surface, It comprises a second semi-transparent mirror located between the first phase difference plate and the second phase difference plate and having a second reflective surface, A display device in which the optical path length from the display panel to the first reflective surface of the first semi-transparent mirror is two-thirds or less of the focal length of the first semi-transparent mirror.

[0321] (69) The display device according to (68) above, wherein the first semi-transparent mirror is rectangular.

[0322] (70) A housing having a viewing section, A display panel located inside the aforementioned enclosure, which displays images showing supplementary information, An optical system located within the housing that forms an image by focusing the image, A control unit for controlling the image on the display panel, Equipped with, The aforementioned image has a first region visible from the viewing area and a second region not visible from the viewing area when viewed from a distance from the viewing area and facing the viewing area directly. The control unit is a display device that controls the video so that the supplementary information is displayed in the first region.

[0323] (71) A vehicle equipped with a display device as described in any one of the above items (49) to (70).

[0324] (72) A display panel for emitting display light, The system comprises an optical system for imaging the aforementioned display light, The optical system described above is Reflective polarizing plate and A first phase difference plate is positioned between the display panel and the reflective polarizing plate, A second phase difference plate is positioned between the first phase difference plate and the reflective polarizing plate, The optical system includes a first semi-transparent mirror located between the first phase difference plate and the second phase difference plate, having a first reflective surface, and having an index expressed as the reciprocal of the degree of light collection, degree of convergence, or focal length that is greater than that of the other members of the optical system. Display device.

[0325] (73) The display device according to (72), wherein the first reflective surface of the first semitransparent mirror has a concave surface having a greater curvature than the other members of the optical system.

[0326] (74) A display panel for emitting display light, The system comprises an optical system for imaging the aforementioned display light, The optical system described above is Reflective polarizing plate and A first phase difference plate is positioned between the display panel and the reflective polarizing plate, A second phase difference plate is positioned between the first phase difference plate and the reflective polarizing plate, It includes a first semi-transparent mirror located between the first phase difference plate and the second phase difference plate and having a first reflective surface, Except for the first semi-transparent mirror, and excluding lenses, Display device. See (72) above. (75) A display panel for emitting display light, The system comprises an optical system for imaging the aforementioned display light, The optical system described above is Reflective polarizing plate and A first phase difference plate is positioned between the display panel and the reflective polarizing plate, A second phase difference plate is positioned between the first phase difference plate and the reflective polarizing plate, It includes a first semi-transparent mirror located between the first phase difference plate and the second phase difference plate and having a first reflective surface, A display device having only the first semi-transparent mirror as a member for focusing the display light.

[0327] (76) The display device according to any one of the above items (72) to (75), wherein air is interposed between the first phase difference plate and the second phase difference plate.

[0328] (77) The display device according to any one of (72) to (75) above, having a third phase difference plate positioned between the display panel and the reflective polarizing plate.

[0329] (78) The display device according to any one of (72) to (75) above, further comprising a fourth phase difference plate positioned between the display panel and the reflective polarizing plate.

[0330] (79) The display device according to any one of (72) to (75) above, wherein the first phase difference plate is arranged on the surface of the first semitransparent mirror.

[0331] (80) The display device according to any one of (72) to (75) above, wherein the second phase difference plate is arranged on the surface of the first semitransparent mirror.

[0332] (81) A housing having a window, A display panel located inside the aforementioned housing and for emitting display light, Within the housing, the first semi-transparent mirror is positioned so as to overlap with the display panel when the inside of the housing is viewed from the window, and the optical system for forming an image of the display light is provided. Equipped with, A display device wherein the index expressed as the reciprocal of the light-gathering degree, focusing degree, or focal length of the first semi-transparent mirror is greater than that of other components included in the optical system.

[0333] (82) A housing having a window, A display panel located inside the aforementioned housing and for emitting display light, Within the housing, the first semi-transparent mirror is positioned so as to overlap with the display panel when the inside of the housing is viewed from the window, and the optical system for forming an image of the display light is provided. Equipped with, The optical system is a display device that does not include lenses, except for the first semi-transparent mirror.

[0334] (83) A housing having a window, A display panel located inside the aforementioned housing and for emitting display light, Within the housing, the first semi-transparent mirror is positioned so as to overlap with the display panel when the inside of the housing is viewed from the window, and the optical system for forming an image of the display light is provided. Equipped with, The optical system is a display device having only the first semi-transparent mirror as a member for focusing the display light.

[0335] (84) The display device according to any one of the above items (72) to (83), wherein the first semi-transparent mirror has a Fresnel shape.

[0336] (85) The display device according to any one of the above items (72) to (83), wherein the first semi-transparent mirror has a holographic optical element.

[0337] (86) The display device according to any one of items (72) to (83) above, wherein the first semi-transparent mirror is a reflective polarizing plate.

[0338] (87) The display device according to any one of the above items (72) to (83), wherein the optical system has a second semi-transparent mirror.

[0339] (88) The display device according to any one of (72) to (87) above, wherein the display light includes a display light for a left-eye image and a display light for a right-eye image, and further includes an optical element for defining the direction of each ray of the display light for the left-eye image and the display light for the right-eye image.

[0340] (89) The display device according to any one of the above items (72) to (88), further comprising an irradiator for irradiating light onto the side of the display panel opposite to the display surface for emitting the display light.

[0341] (90) The display device according to any one of (72) to (89) above, comprising a controller having a function for controlling an image to be displayed on the display panel and at least one of the irradiator.

[0342] (91) A vehicle equipped with a display device as described in any one of the above items (72) to (90).

[0343] (92) A display device as described in any one of the above items (72) to (90), Equipped with a camera, The display device is a display system that can communicate with the camera and displays images captured by the camera.

[0344] (93) A vehicle equipped with the display system described in (92) above.

[0345] (94) An imaging device including the display device described in any one of the above items (72) to (90).

[0346] (95) A vehicle equipped with the imaging device described in (94) above.

[0347] (96) A housing having a window, A display panel located inside the aforementioned housing and for emitting display light, An optical system located within the housing for forming an image of the display light, Equipped with, A display device wherein the longitudinal length of the image is greater than the length of the window along the longitudinal direction.

[0348] (97) The display device according to (96) above, wherein the longitudinal length of the image is greater than the length of the housing along the longitudinal direction.

[0349] (98) A housing having a window, A display panel located inside the aforementioned housing and for emitting display light, The housing comprises an optical system located within the housing for forming an image of the display light. The aforementioned image has a visible area that is visible from the window and an invisible area that is not visible from the window when the user is stationary and looking at the window from a distance. Display device.

[0350] (99) The display device according to any one of (96) to (98) above, further comprising a mechanism for changing the size or position of the image.

[0351] (100) Further comprising a controller for controlling the display of the display panel, The controller is a display device according to any one of items (96) to (99) above, capable of changing the size or display position of the image.

[0352] (101) The display device described in (100) above, wherein the controller changes the size or display position of the image based on user information.

[0353] (102) When a user stands still away from the window and looks at the window, the image has a first region located to the right and outside of the window and a second region located to the left and outside of the window. The display device according to (101) above, wherein the controller controls the size or display position of the image so as to reduce the difference between the size of the first region and the size of the second region.

[0354] (103) When a user stands still away from the window and looks at the window, the image has a first region located to the right and outside of the window and a second region located to the left and outside of the window. The display device according to (101) above, wherein the controller controls the difference between the width in the left-right direction of the first region and the width in the left-right direction of the second region to be reduced.

[0355] (104) A vehicle equipped with a display device as described in any one of the above items (96) to (103).

[0356] (105) A display device as described in any one of the above items (96) to (103), The system includes a camera capable of communicating with the aforementioned display device. The display panel is a display system that displays images captured by the camera.

[0357] (106) A vehicle equipped with the display system described in (105) above.

[0358] (107) A display panel for emitting display light, The system comprises an optical system for imaging the display light, each having a pair of semi-transparent mirrors, each having a reflective surface, Display device.

[0359] (108) The pair of semi-transparent mirrors includes a first semi-transparent mirror located on the display panel side and a second semi-transparent mirror different from the first semi-transparent mirror. The reflective surface of the second semi-transparent mirror diverges the light that is incident from the side of the first semi-transparent mirror and reflected. The reflective surface of the first semi-transparent mirror focuses the light that is incident from the second semi-transparent mirror side and reflected. The display device described above.

[0360] (109) The display device according to (108), wherein the reflective surface of the first semi-transparent mirror has a concave curved surface.

[0361] (110) The display device according to (108) above, wherein the reflective surface of the second semi-transparent mirror has a convex curved surface.

[0362] (111) The display device according to any one of the pair of semi-transparent mirrors, wherein at least one of them has a Fresnel shape.

[0363] (112) The display device according to any one of the pair of semi-transparent mirrors, wherein at least one of them is a holographic optical element, as described in any one of (107) to (110).

[0364] (113) The display device according to any one of the pair of semi-transparent mirrors, wherein at least one of them is a reflective polarizer.

[0365] (114) The display device according to any one of (107) to (113), wherein the optical system further comprises a first phase difference plate located between the pair of semitransparent mirrors.

[0366] (115) The display device according to any one of (107) to (113), wherein the optical system further comprises a polarizing plate positioned between the display panel and the pair of semi-transparent mirrors, and a second phase difference plate positioned between the polarizing plate and the pair of semi-transparent mirrors.

[0367] (116) The display device according to (115), wherein the optical system further comprises a third phase difference plate located between the display panel and the polarizing plate.

[0368] (117) The display device according to (116), wherein the optical system further comprises a fourth phase difference plate located between the display panel and the polarizing plate.

[0369] (118) A housing having a window and further comprising the display panel and the optical system, The display device according to any one of items (107) to (117) above, wherein the optical system is positioned so as to overlap with the display panel when the inside of the housing is viewed from the window.

[0370] (119) The display device according to any one of (107) to (118), wherein the display light includes a display light for a left-eye image and a display light for a right-eye image, and further includes an optical element that defines the direction of each ray of the display light for the left-eye image and the display light for the right-eye image.

[0371] (120) The display device according to any one of (107) to (119) above, further comprising an irradiator for irradiating light onto the surface of the display panel opposite to the display surface from which the display light is emitted.

[0372] (121) The display device according to any one of (107) to (120) above, comprising a controller having a function for controlling an image to be displayed on the display panel and at least one of the irradiator.

[0373] (122) A vehicle equipped with a display device as described in any one of the above items (107) to (121).

[0374] (123) A display device as described in any one of the above items (107) to (121), The system includes a camera capable of communicating with the aforementioned display device. The display panel is a display system that displays images captured by the camera.

[0375] (124) A vehicle equipped with the display system described in (123) above.

[0376] (125) An imaging device including a display device as described in any one of the above items (107) to (121).

[0377] (126) A vehicle equipped with the imaging device described above.

[0378] (127) A housing having a viewing section, A display panel located inside the aforementioned housing and having a display surface, An optical system located within the housing and forming an image on the display surface, Equipped with, The image is a display device having a first region visible from the viewing unit and a second region smaller than the first region that is not visible from the viewing unit, when viewed from a distance from the viewing unit and facing the viewing unit directly. [Explanation of Symbols]

[0379] 1,1A,1A',1B represent devices. 2 means パネル 2a represents a surface 3. Optics Department 4 Irradiators 5. Phase Difference Plate (1st Position) 6. Semi-transparent lens 6a Reflective surface 7. Second phase difference plate 8 reflective polarizer 9 optical elements 10 Optics Department 11. The first semi-transparent lens 11a Reflecting surface 12 First phase difference plate 13,13' Second semi-transparent lens 13a, 13'a Reflecting surfaces 14 Second phase difference plate 15 polarizing plate 16 Department of Optics 17. The first semi-transparent lens 17a Reflecting surface 18. First phase difference plate 19 Second semi-transparent lens 19a Reflecting surface 19b Reflective surface 20 Second phase difference plate 21. Third semi-transparent lens 21a Reflecting surface 22 users 22L Left eye 22R Right eye 23 Moving bodies 24 ウインドシールド 25. Third phase difference plate 26. 4th phase difference plate 27 box 28 Opening 29 クラスタ 30 CID 31 PID 32 RSE 33 フレネルレンズ 33a Page 1 33b Page 2 33c reference point 34 Semi-transparent reflective layer 35 Department of Optics 36 cabinets 37 windows 38 Light transmission plate 39,40 Moth-eye structure film 41 Touch panel 42 Convex lenses 43 Controllers 100 Imaging device 101 Reflecting optical element 102 Cameras 200 Display Systems 201 Camera 401 1st area 402 Second area 403 The Center of the Illusion 404 Normal vector to the center of the virtual image 405 User Center 406 The portion of the second region located above and below the first region. 407 The portion of the second region located on the side of the first region. 408 1st end 409 Center of the window 410 1st straight line 411 2nd end 412 Second straight line 413 and 414 The endpoints of the virtual image 415 and 416 Endpoints of the semi-transparent mirror 417 and 418 Two straight lines connecting the endpoints of the virtual image to the endpoints of the semitransparent mirror, respectively. 419 The intersection of two lines connecting the endpoints of the virtual image and the endpoints of the semitransparent mirror. 420 End of semi-transparent mirror 421 Shielding Wall 422 Visibility 423 Control Unit 424 Base material 425 Reflective polarizer 426 Base material 427 Display system 428 Concave mirror part 429 Concave mirror part 501 Display device f6 semi-transparent mirror focus L6 is the longitudinal length of the semi-transparent mirror. L37 Length along the longitudinal direction of the window Lf6 Focal length of a semi-transparent mirror V428 Illusion V429 Illusion WL (Long side of the window)

Claims

1. A housing having a viewing section, A display panel located inside the aforementioned housing and having a display surface, The housing is located between the viewing section and the display panel and includes an optical system having a semi-transparent mirror for imaging the display surface to form a virtual image, A display device in which, when the first angle is defined as the angle between two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, and each of the pair of endpoints of the semitransparent mirror, which are aligned horizontally, and the second angle is defined as the angle between two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, and each of the pair of endpoints of the semitransparent mirror, which are aligned vertically, the first angle is greater than the second angle.

2. A housing having a viewing section, A display panel located inside the aforementioned housing and having a display surface, The housing is located between the viewing section and the display panel and includes an optical system having a semi-transparent mirror for imaging the display surface to form a virtual image, A display device in which, when the intersection of two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally in the left-right direction, to each of the pair of endpoints of the semi-transparent mirror, which are aligned horizontally, is defined as the first intersection point, and the intersection of two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, to each of the pair of endpoints of the semi-transparent mirror, which are aligned vertically, is defined as the second intersection point, the first intersection point is located closer to the semi-transparent mirror than the second intersection point.

3. Two straight lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, to each of the pair of endpoints of the semitransparent mirror, which are aligned horizontally, pass through the viewing section. The display device according to claim 1 or 2.

4. The two straight lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, and each of the pair of endpoints of the semitransparent mirror, which are aligned vertically, pass through the viewing section. The display device according to claim 1 or 2.

5. The display device according to claim 1 or 2, wherein the size of the virtual image is less than twice the size of the viewing area.

6. The display device according to claim 1 or 2, wherein the size of the virtual image is larger than the housing.

7. The display device according to claim 6, wherein the outer edge of the virtual image is located outside the housing when viewed from a distance from the viewing unit and facing the viewing unit directly.

8. The display device according to claim 1 or 2, wherein the focal point of the semitransparent mirror is located outside the housing.

9. The display device according to claim 1, wherein the semi-transparent mirror has a reflective surface, and the optical path length from the light emitted from the display panel to the reflective surface of the semi-transparent mirror from the viewing section side is two-thirds or less of the focal length of the semi-transparent mirror.

10. The virtual image has a first region that is visible from the viewing unit and a second region that is not visible from the viewing unit when viewed from a distance from the viewing unit and facing the viewing unit directly. The display device according to claim 1 or 2, wherein the first region has an area at least twice that of the second region.

11. The display device according to claim 10, A camera capable of communicating with the aforementioned display device, The system comprises a control unit for controlling the image displayed on the display panel, The display panel displays the image captured by the camera. The control unit controls the video so that supplementary information is displayed in the first and second regions, and the display system is also described.

12. The display system according to claim 11, wherein the control unit controls the first region to display more of the supplementary information than the second region.

13. The display system according to claim 11, wherein the control unit controls the first region to have a higher density of supplementary information than the second region.

14. The display device according to claim 1 or 2, which is a non-wearable display device for the user.

15. The display device according to claim 14, which is fixed to the interior of a mobile body.

16. A mobile body comprising the display device described in claim 1 or 2.

17. A housing having a viewing section, A display panel mounting section located within the aforementioned housing, on which a display panel having a display surface can be installed, The housing is located between the display panel mounting section and the viewing section and includes an optical system having a semi-transparent mirror for forming an image of the display surface and creating a virtual image. A display panel housing device wherein, when the first angle is defined as the angle between two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally, and each of the pair of endpoints of the semitransparent mirror, which are aligned horizontally, and the second angle is defined as the angle between two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, and each of the pair of endpoints of the semitransparent mirror, which are aligned vertically, the first angle is greater than the second angle.

18. A housing having a viewing section, A display panel mounting section located within the aforementioned housing, on which a display panel having a display surface can be installed, The housing is located between the display panel mounting section and the viewing section and includes an optical system having a semi-transparent mirror for forming an image of the display surface and creating a virtual image. A display panel housing device wherein, when the intersection of two lines connecting each of the pair of endpoints of the virtual image, which are aligned horizontally in the left-right direction, to each of the pair of endpoints of the semi-transparent mirror, which are aligned horizontally, is defined as the first intersection point, and the intersection of two lines connecting each of the pair of endpoints of the virtual image, which are aligned vertically, to each of the pair of endpoints of the semi-transparent mirror, which are aligned vertically, is defined as the second intersection point, the first intersection point is located closer to the semi-transparent mirror than the second intersection point.

Images