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

Abstract

To solve the problem in which: in a conventional display unit, deformation of optical members, positional deviation between the optical members, and the like easily occur, which may reduce display quality.SOLUTION: A display unit comprises: a housing having a visual recognition part; a display panel located inside the housing and having a display surface; and an optical system located inside the housing and forming an image on the display surface. The image has a first area that can be visually recognized from the visual recognition part and a second area that cannot be visually recognized from the visual recognition part and is smaller than the first area when the image is seen away from the visual recognition part and facing the visual recognition part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a display device, a display system, a vehicle, and a display panel housing device. [Background technology]

[0002] BACKGROUND ART A display device described in Patent Document 1, for example, is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-63533 Summary of the Invention

[0004] The display device of the present disclosure includes a housing having a viewing portion; a display panel located within the housing and having a display surface; an optical system located within the housing and focusing the image on the display surface to form an image; Equipped with When viewed from a distance from the viewing portion and facing the viewing portion, the image has a first area that is visible from the viewing portion and a second area that is not visible from the viewing portion and is smaller than the first area.

[0005] The display system of the present disclosure also includes the display device, a camera capable of communicating with the display device, The display panel displays an image captured by the camera.

[0006] The vehicle of the present disclosure is equipped with the display device.

[0007] The display panel housing device of the present disclosure includes: a housing having a viewing portion; an optical system that forms an image by focusing an image of the display panel when the display panel is installed in the housing; Equipped with When viewed from a distance from the viewing unit and facing the viewing unit, the optical system is capable of forming an image having a first area that is visible from the viewing unit and a second area that is not visible from the viewing unit and is smaller than the first area. [Brief explanation of the drawings]

[0008] The objects, features, and advantages of the present disclosure will become more apparent from the following detailed description and drawings. [Figure 1] 1 is a diagram schematically illustrating a configuration of a display device according to the present disclosure. [Figure 2] 1 is a cross-sectional view illustrating an example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 3] FIG. 10 is a cross-sectional view showing another example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 4] FIG. 10 is a cross-sectional view showing an example of a main configuration of a display device according to another embodiment of the present disclosure. [Figure 5] FIG. 10 is a cross-sectional view showing another example of a main configuration of a display device according to another embodiment of the present disclosure. [Figure 6] 5 is a diagram illustrating the projection of a virtual image in the display device of FIG. 4. FIG. [Figure 7] 6 is a diagram illustrating the projection of a virtual image in the display device of FIG. 5. FIG. [Figure 8] FIG. 6 is a diagram illustrating the design of an optical system in the display device of FIG. [Figure 9] FIG. 10 is a cross-sectional view showing an example of a main configuration of a display device according to still another embodiment of the present disclosure. [Figure 10] FIG. 1 is a diagram illustrating an example of a configuration of an imaging device according to an embodiment of the present disclosure. [Figure 11] FIG. 10 is a diagram illustrating another example of the configuration of an imaging device according to an embodiment of the present disclosure. [Figure 12] FIG. 10 is a diagram illustrating another example of the configuration of an imaging device according to an embodiment of the present disclosure. [Figure 13] FIG. 10 is a top view illustrating another example of the display device. [Figure 14]FIG. 10 is a top view illustrating another example of the display device. [Figure 15] FIG. 10 is a cross-sectional view illustrating another example of the display device. [Figure 16] FIG. 10 is a cross-sectional view illustrating another example of the display device. [Figure 17A] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 17B] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 17C] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 17D] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 18A] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 18B] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 18C] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 18D] FIG. 10 is a diagram illustrating an optical system in another example of a display device. [Figure 19] 10 is a graph illustrating an optical system in another example of a display device. [Figure 20] FIG. 10 is a cross-sectional view illustrating another example of the display device. [Figure 21] FIG. 10 is a cross-sectional view illustrating another example of the display device. [Figure 22] FIG. 10 is a cross-sectional view illustrating another example of the display device. [Figure 23] FIG. 4 is a cross-sectional view showing an example of the configuration of a second semi-transparent mirror. [Figure 24] FIG. 10 is a cross-sectional view illustrating another example of the display device. [Figure 25] 10A and 10B are diagrams illustrating how a virtual image appears when a user is positioned in front of the display device. [Figure 26] 10A and 10B are diagrams illustrating how a virtual image appears when a user is not positioned in front of the display device. [Figure 27]10A and 10B are diagrams illustrating how a virtual image appears when the display device is adjusted. [Figure 28] 10A and 10B are diagrams illustrating how a virtual image appears when the display device is adjusted. [Figure 29] 10 is a flowchart illustrating control of the imaging device. [Figure 30] FIG. 10 is a cross-sectional view showing another example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 31] FIG. 10 is a cross-sectional view showing another example of a main configuration of a display device according to another embodiment of the present disclosure. [Figure 32] FIG. 10 is a cross-sectional view showing another example of a main configuration of a display device according to still another embodiment of the present disclosure. [Figure 33] FIG. 10 is a perspective view showing a cross section of another example of a display device according to an embodiment of the present disclosure. [Figure 34] FIG. 10 is a cross-sectional view illustrating another example of a display device according to an embodiment of the present disclosure. [Figure 35] FIG. 10 is a perspective view showing a cross section of another example of a display device according to an embodiment of the present disclosure. [Figure 36] FIG. 10 is a cross-sectional view illustrating another example of a display device according to an embodiment of the present disclosure. [Figure 37] 3 is a diagram showing an optical path of display light in the display device of FIG. 2. FIG. [Figure 38] 3 is a cross-sectional view showing another example of the display device of FIG. 2. FIG. [Figure 39] 1 is a diagram illustrating an example of a configuration of a display system and a vehicle according to an embodiment of the present disclosure. [Figure 40] FIG. 10 is a perspective view showing a cross section of yet another example of a display device according to an embodiment of the present disclosure. [Figure 41] FIG. 41 is a plan view of an image formed by the display device shown in FIG. 40. [Figure 42] FIG. 10 is a top view illustrating the viewing portion viewed from the front. [Figure 43] 10 is a diagram comparing the length of the viewing portion along the longitudinal direction with the length of the semi-transparent mirror along the longitudinal direction. FIG. [Figure 44]10 is a diagram illustrating two straight lines connecting both end points of an image and both end points of a semi-transparent mirror in a cross-sectional view. FIG. [Figure 45] 10 is a diagram illustrating two straight lines connecting both end points of an image and both end points of a semi-transparent mirror in a cross-sectional view. FIG. [Figure 46] FIG. 10 is a perspective view showing a cross section of yet another example of a display device according to an embodiment of the present disclosure. [Figure 47] FIG. 10 is a block diagram illustrating another example of a display device according to an embodiment of the present disclosure. [Figure 48] FIG. 48 is a plan view of an image formed by the display device shown in FIG. 47. [Figure 49] 1 is a cross-sectional view illustrating an example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 50] 1 is a cross-sectional view illustrating an example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 51] 1 is a cross-sectional view illustrating an example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 52] 1 is a cross-sectional view illustrating an example of a main configuration of a display device according to an embodiment of the present disclosure. [Figure 53A] FIG. 53 is a diagram illustrating the optical functions of the display devices according to each of FIGS. 49 to 52. [Figure 53B] FIG. 53 is a diagram illustrating the optical functions of the display devices according to each of FIGS. 49 to 52. [Figure 54] An example of various dimensions of the display device shown in FIG. 34 is shown below. DETAILED DESCRIPTION OF THE INVENTION

[0009] Various small display devices have been proposed for use in digital rearview mirrors placed inside vehicle cabins, head-mounted displays worn on the user's head, etc. The display device described in Patent Document 1 is configured to emit display light emitted from a display panel via multiple optical members such as a retardation plate and a reflective polarizing plate.

[0010] In conventional display devices, deformation of optical members and misalignment of optical members are likely to occur, which may result in a decrease in display quality.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Some of the drawings used in the following description are schematic. The drawings used in the following description show major components of the display device and virtual image display device of the present disclosure. The display device and virtual image display device of the present disclosure may include well-known components not shown, such as a holding member for the optical system and a housing. In this specification, a Cartesian coordinate system XYZ is defined in some drawings 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 the up-down direction. The Z-axis direction is also referred to as the emission direction or the depth direction. In the present disclosure, the Y-axis direction may be the direction along the up-down 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.

[0012] 1 to 39 are diagrams or graphs for explaining the display device, imaging device, display system, and vehicle of the present disclosure. In Figures 2 to 5, 9, 15, 16, 20 to 22, 24, and 30 to 32, for ease of illustration, the optical path of light incident on a light-reflective optical element and the optical path of light reflected by the optical element are shown shifted in the height direction (Y-axis direction).

[0013] As shown in FIG. 1 , a display device 1 according to an embodiment of the present disclosure includes a display panel 2 and an optical system 3. The display device 1 directs a portion of display light emitted from the display panel 2 into the eyes of a user 22, allowing the user 22 to view the image, image, or aerial image. The display device 1 allows the user 22 to view the display on the display panel 2 at a position different from the position of the display panel 2 using the display light emitted from the display panel 2. In an embodiment of the present disclosure, the display device 1 allows the user 22 to view the display on the display panel 2 as a virtual image V. The virtual image V may be formed on a side farther from the display device 1 as viewed from the user 22. The virtual image V may be an erect virtual image obtained by enlarging the display image displayed on the display panel 2. When the display device 1 includes a housing (see FIGS. 33 to 36 ) that houses the display panel 2 and the optical system 3, the virtual image V may be formed inside or outside the housing. The virtual image V may be formed on a side farther from the display panel 2 as viewed from the user 22, or on a side closer to the display panel 2. If the housing has a window 37 (see FIGS. 33 to 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 viewed by the user 22, or may be formed on the side closer to the window. If the display device 1 has a touch panel 41 (see FIGS. 35 and 36), the virtual image V may be formed on the side farther from the touch panel 41 as viewed by the user 22, or may be formed on the side closer to the touch panel 41.

[0014] The display device 1 according to an embodiment of the present disclosure may be a non-wearable device for the user 22. In other words, it may be used while being fixed to the environment, rather than being worn by the user 22. This means that the display device 1 is fixed to, for example, a wall, a pillar, or a ceiling. The display device 1 may also be fixed to the interior of a vehicle. The present disclosure may also be worn by the user 22. When worn by the user 22, the display device 1 may include a mounting unit (not shown) so that the window 37 is fixed at the position of the user's 22's eyes.

[0015] The display device 1 may be configured to allow a portion of the display light emitted from the display panel 2 to be incident on the eyes of the user 22, allowing the user 22 to view the image as a real image. The real image may be formed closer to the user 22 than the display device 1. If the display device 1 includes a housing 36 (see FIGS. 33 to 36) that houses the display panel 2 and the optical system 3, the real image may be formed inside or outside the housing 36. The real image may be formed farther from the user 22 than the display panel 2, or may be formed closer to the user 22 than the display panel 2. If the housing 36 has a window 37 (see FIGS. 33 to 36) that transmits the display light emitted from the optical system 3, the real image may be formed farther from the user 22 than the window 37 (light-transmitting plate 38), or may be formed closer to the user 22 than the window 37 (light-transmitting plate 38). When the display device 1 has a touch panel 41 (see FIGS. 35 and 36), the real image may be formed on the farther side than the touch panel 41 when viewed from the user 22, or may be formed on the closer side than the touch panel 41.

[0016] The display panel 2 has a display surface 2a and displays a display image on the display surface 2a. In other words, the display panel 2 emits display light for 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 be given of a case where the display panel 2 emits S-wave polarized display light, but the present invention is not limited to this.

[0017] The display panel 2 may be a liquid crystal panel. The liquid crystal panel may have a known liquid crystal panel configuration. The known liquid crystal panel may be, for example, an IPS (In-Plane Switching) type, an FFS (Fringe Field Switching) type, a VA (Vertical Alignment) type, or an ECB (Electrically Controlled Birefringence) type liquid crystal panel.

[0018] The display device 1 may include an illuminator 4 that illuminates the display panel 2 in a planar manner. The illuminator 4 is also referred to as a backlight. The illuminator 4 may be an edge-lit backlight or a direct-lit backlight. An edge-lit backlight has one or more light sources arranged around the periphery of the display panel 2. The light emitted from the light sources is guided by a light guide plate to the entire rear surface of the display panel 2, where it is uniformly dispersed. A direct-lit backlight has multiple light sources arranged on the rear side of the display panel 2 and illuminates the display panel 2 with light emitted from the multiple light sources. The light source of the illuminator 4 may be a cold cathode fluorescent lamp, a halogen lamp, a xenon lamp, a light-emitting diode (LED), an organic light-emitting diode (OLED), a semiconductor laser (LD), or the like. If the light source of the illuminator 4 is an LD with excellent monochromaticity, the design of the optical system 3, particularly the design of optical components whose optical characteristics are wavelength-dependent, becomes easier.

[0019] The display panel 2 is not limited to a liquid crystal panel (transmissive display panel), but may be a self-luminous display panel including self-luminous elements such as light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), and semiconductor lasers (LDs).

[0020] The optical system 3 projects the display light emitted from the display panel 2 as a virtual image V into the field of view of the user 22. As shown in FIG. 2 , the optical system 3 may include a first retardation plate 5, a semi-transparent mirror 6, a second retardation plate 7, and a reflective polarizer 8. The first retardation plate 5, the semi-transparent mirror 6, the second retardation plate 7, and the reflective polarizer 8 are arranged in this order in the emission direction of the display light from the display panel 2 (positive direction of the Z-axis).

[0021] The first retardation plate 5 is positioned opposite the display surface 2a of the display panel 2. The first retardation plate 5 is positioned away from the display surface 2a in the emission direction of display light from the display panel 2. The second retardation plate 7 is positioned away from the first retardation plate 5 in the emission direction of display light from the display panel 2. The first retardation plate 5 and the second retardation plate 7 are quarter-wave plates. The first retardation plate 5 and the second retardation plate 7 impart a phase difference of a quarter wavelength to the polarization plane of the incident light (the polarization plane in the electric field vibration direction). This allows a portion of the display light emitted from the display panel 2 to be reflected by the reflective polarizer 8 and incident on the semi-transparent mirror 6.

[0022] The first retardation plate 5 and the second retardation plate 7 only need to impart a 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 polarized light obtained by transmission through the first retardation plate 5 and the second retardation plate 7 is the second polarized light, the first retardation plate 5 and the second retardation plate 7 may be other wave plates or a combination thereof instead of quarter-wave plates, as long as the second polarized light is obtained. In the present disclosure, an example will be described in which the first retardation plate 5 and the second retardation plate 7 are quarter-wave plates.

[0023] Furthermore, the second retardation plate 7 only needs to impart a necessary phase difference to the light that has transmitted through the second retardation plate 7 so that the light that has been reflected by the reflective polarizing plate 8 and transmitted through the second retardation plate 7 is transmitted through the reflective polarizing plate 8 when it reaches the reflective polarizing plate 8 again. In other words, for example, when the polarized light obtained by reflection by the reflective polarizing plate 8 and transmission through the second retardation plate 7 is defined as the first polarized light, the second retardation plate 7 may be any other wave plate instead of a quarter wave plate as long as the first polarized light is obtained.

[0024] The first retarder 5 may be integrated with the display panel 2 as shown in Fig. 30. "Integrated" 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 with an optically clear adhesive such as OCA (Optically Clear Adhesive).

[0025] The semi-transmitting mirror 6 is located between the first retardation plate 5 and the second retardation plate 7. The semi-transmitting mirror 6 may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remaining portion (e.g., approximately 50%). The semi-transmitting mirror 6 reflects a portion of the display light reflected by the reflective polarizer 8 and makes it incident on the eyes of the user 22. This allows the user 22 to view the virtual image V. The semi-transmitting mirror 6 has a function of collecting or converging light. Specifically, the semi-transmitting mirror 6 has a function of collecting or converging light that is incident on and reflected by the semi-transmitting mirror 6. In this embodiment, the semi-transmitting mirror 6 can collect or converge light more effectively than other components of the optical system 3. In other words, the semi-transmitting mirror 6 is set to have a larger degree of collection, a larger degree of convergence, or an index represented by the reciprocal of the focal length, than other components of the optical system 3. In this embodiment, the optical system 3 may include only the semi-transparent mirror 6 as a component having a light collecting or converging function. The semi-transparent mirror 6 may be a concave mirror having a concave reflecting surface 6a, as shown in FIG. 2 . The semi-transparent mirror 6 faces the second retardation plate 7; more specifically, the reflecting surface 6a of the semi-transparent mirror 6 may face the second retardation plate 7. In this embodiment, the semi-transparent mirror 6 has a concave reflecting surface 6a, thereby being able to collect or converge light. The reflecting surface 6a of the semi-transparent mirror 6 has a larger curvature than the other components of the optical system 3. At least a portion of the reflecting surface 6a of the semi-transparent mirror 6 may have a spherical, aspherical, or free-form surface shape. The transmittance of the semi-transparent mirror 6 is not limited to 50%.

[0026] The semi-transmitting mirror 6 includes, for example, a substrate and a semi-transmitting 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, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The semi-transmitting reflective layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum or chromium. The semi-transmitting reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film. The semi-transmitting mirror 6 may be configured to reflect light by a semi-transmitting reflective layer. The semi-transmitting reflective layer may be formed on the surface of the substrate facing the second retardation plate 7.

[0027] The reflective polarizer 8 is positioned opposite to the surface of the second retardation plate 7 opposite to the surface facing the semi-transmitting mirror 6. In other words, the reflective polarizer 8 is positioned after the second retardation plate 7 in the emission direction of the display light from the display panel 2. The reflective polarizer 8 may transmit a portion of the incident light and reflect the remaining portion. 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 (P-wave polarized light, also referred to as second polarization) and transmit polarized light having a polarization axis parallel to the polarization axis of the display light (S-wave polarized light, also referred to as first polarization). This allows the user 22 to view the virtual image V. The reflective polarizer 8 may be integrated with the second retardation plate 7 as shown in FIG. 30 .

[0028] The reflective polarizer 8 may be, for example, a wire grid polarizer including a substrate and a plurality of thin metal wires (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 range. The substrate may be made of, for example, a resin material, a glass material, or the like. The thin metal wires may be made of a metal material such as aluminum, chromium, or titanium oxide. The thin metal wires may be arranged in one direction. The reflective polarizer 8 can transmit light components vibrating in a direction perpendicular to the grid and reflect light components vibrating in a direction parallel to the grid.

[0029] 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 processor may include a general-purpose processor configured to load a specific program and execute a specific function, and a dedicated processor specialized for a specific process. The processor may include a programmable logic device (PLD). The controller 43 may be either an SoC (System-on-a-Chip) or an SiP (System-in-a-Package) in which one or more processors work together. The controller 43 may include a memory unit and store various information or programs for operating each component of the display device 1. The memory unit may be configured, for example, with a semiconductor memory. The memory unit may function as a work memory for the controller 43.

[0030] The optical function of the optical system 3 will be described. The display panel 2 emits display light of S-wave polarized light (first linearly polarized light L1). The first linearly polarized light L1 emitted from the display panel 2 passes through the first retardation plate 5 and is converted into first circularly polarized light C1. A portion (e.g., approximately 50%) of the first circularly polarized light C1 that passes through the first retardation plate 5 passes through the semi-transparent mirror 6. The first circularly polarized light C1 that passes through the semi-transparent mirror 6 passes through the second retardation plate 7 and is converted into second linearly polarized light L2 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., P-wave polarized light). The second linearly polarized light L2 enters the reflective polarizer 8. As described above, the reflective polarizer 8 reflects P-wave polarized light and transmits S-wave polarized light. The second linearly polarized light L2 that enters the reflective polarizer 8 is reflected by the reflective polarizer 8 and converted into third linearly polarized light L3. The third linearly polarized light L3 passes through the second retardation plate 7 and is converted into the second circularly polarized light C2. A portion (e.g., approximately 50%) of the second circularly polarized light C2 that passes through the second retardation plate 7 is reflected by the semi-transparent mirror 6 and converted into the third circularly polarized light C3. The third circularly polarized light C3 passes through the second retardation 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., S-wave polarized light). The fourth linearly polarized light L4 passes through the reflective polarizer 8 and is emitted to the outside. The amount of light (brightness) of the light emitted from the display device 1 is, for example, approximately 25% of the amount of display light (brightness) emitted from the display panel 2.

[0031] The first retarder 5, semi-transmitting mirror 6, second retarder 7, and reflective polarizer 8 are held by a holding member (not shown), thereby maintaining their relative positions. Air is interposed between the first retarder 5 and the second retarder 7 (i.e., between the first retarder 5 and the semi-transmitting mirror 6 and between the semi-transmitting mirror 6 and the second retarder 7). The display device 1 does not include a member made of a resin material such as a polymer between the first retarder 5 and the second retarder 7. This reduces the risk of deformation of the semi-transmitting mirror 6 when the resin material is cured during the manufacturing process of the display device 1, as well as misalignment between the semi-transmitting mirror 6 and the first retarder 5 and the second retarder 7. Furthermore, resin materials such as polymers have a specific retardation characteristic, which reduces the risk of changing the polarization state of light passing through the resin material. As a result, degradation of display quality is reduced.

[0032] 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 outgoing light are substantially aligned, which makes it possible to reduce the space occupied by the optical system 3 and, as a result, to miniaturize the display device 1. Furthermore, because the optical system 3 is on-axis, it is possible to reduce distortion, brightness unevenness, etc. of the virtual image V visually recognized by the user 22, and also makes it easier to design the optical system 3.

[0033] In the display device 1, the optical path length of light emitted from the display panel 2, transmitted through the semi-transmitting mirror 6, reflected by the reflective polarizer 8, and reaching the semi-transmitting mirror 6 may be shorter than the focal length of the semi-transmitting mirror 6. In this case, the user 22 can view a virtual image V. In the display device 1, the optical path length of light emitted from the display panel 2, transmitted through the semi-transmitting mirror 6, reflected by the reflective polarizer 8, and reaching the semi-transmitting mirror 6 may be longer than the focal length of the semi-transmitting mirror 6. In this case, the user 22 can view a real image.

[0034] 2, for ease 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 shown shifted in the height direction (Y-axis direction), but in reality, the display light emitted from the display panel 2 propagates substantially on one axis, as shown in Fig. 37. This is also true for the optical paths shown in Figs. 3 to 5, 9, 15, 16, 20 to 22, 24, and 30 to 32.

[0035] As shown in FIG. 38 , the display device 1 may have the first retardation plate 5, the semi-transparent mirror 6, the second retardation plate 7, and the reflective polarizer 8 replaced with a convex lens 42. In the display device 1, the optical path length from the display panel 2 to the convex lens 42 may be shorter than the focal length of the convex lens 42. In this case, the user 22 can view a virtual image V. In the display device 1, the optical path length from the display panel 2 to the convex lens 42 may be longer than the focal length of the convex lens 42. In this case, the user 22 can view a real image.

[0036] The display panel 2 may display a mixed image including a left-eye image and a right-eye image having a parallax therebetween, and may emit display light for the mixed image. As shown in FIG. 3 , 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. The optical element 9 is configured to direct a portion of the display light for the mixed image to one of the left eye and the right eye of the user 22, and direct another portion of the display light to the other of the left eye and the right eye of the user 22. The optical element 9 is configured to determine the respective light ray directions of the display light for the left-eye image and the display light for the right-eye image, thereby directing at least a portion of the display light for the left-eye image to the left eye of the user 22, and at least a portion of the display light for the right-eye image to the right eye of the user 22. This enables the display device 1 to allow the user 22 to view a stereoscopic image.

[0037] The optical element 9 may be any element that allows a portion of the display light of the mixed image to reach one of the left and right eyes of the user 22 and another portion of the display light to reach the other of the left and right eyes of the user 22, and may be, for example, a parallax barrier or a lenticular lens. The parallax barrier may be formed of a liquid crystal panel. The optical element 9 may be positioned arbitrarily within the display device 1. The optical element 9 may be positioned between the display panel 2 and the first retardation plate 5, may be positioned after the reflective polarizer 8 in the emission direction of the display light, or may be positioned between the semi-transparent mirror 6 and the second retardation plate 7.

[0038] Next, a display device according to another embodiment of the present disclosure will be described. The display device according to this embodiment has the same configuration as the display device according to the above embodiment except for the optical system configuration. Therefore, the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0039] 4, the display device 1A of this embodiment includes a display panel 2 and an optical system 10. The display panel 2 has a display surface 2a and displays a display image on the display surface 2a. The optical system 10 projects display light emitted from the display panel 2 as a virtual image V into the field of view of a user 22.

[0040] The optical system 10 includes a first semi-transparent mirror 11, a first retardation plate 12, a second semi-transparent mirror 13, a second retardation 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 retardation plate 12, the second semi-transparent mirror 13, the second retardation plate 14, and the polarizing plate 15 are arranged in this order in the emission direction of the display light from the display panel 2.

[0041] The first semi-transmitting mirror 11 has a reflective surface 11a that reflects light. The first retardation plate 12 faces the first semi-transmitting mirror 11, more specifically, faces the reflective surface 11a of the first semi-transmitting mirror 11. The first retardation 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 retardation plate 14 is positioned away from the first retardation plate 12 in the direction of emission of display light. The first semi-transmitting mirror 11 has a function of collecting or converging light. Specifically, the first semi-transmitting mirror 11 has a function of collecting or converging light that is incident on and reflected from the reflective surface 11a of the first semi-transmitting mirror 11. In this embodiment, the first semi-transmitting mirror 11 has, for example, a greater degree of collection, a greater degree of convergence, or an index expressed as the reciprocal of the focal length than other components of the optical system 10. The first retardation plate 12 and the second retardation plate 14 are quarter-wave plates.

[0042] The first semi-transmitting mirror 11 is located between the display panel 2 and the first retardation film 12. The first semi-transmitting mirror 11 may transmit a portion of the incident light and reflect the remainder. As shown in FIG. 4, the first semi-transmitting mirror 11 is a concave mirror having a concave reflective surface 11a facing the first retardation film 12. In this embodiment, the first semi-transmitting mirror 11 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. At least a portion of the reflective surface 11a of the first semi-transmitting mirror 11 may include a spherical, aspherical, or free-form surface shape.

[0043] The first semi-transmitting mirror 11 may be configured, for example, to include a substrate and a plurality of thin metal wires (metal nanowire grid) positioned on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light range. The substrate may be configured, for example, of a resin material, a glass material, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The thin metal wires may be configured, for example, of a metal material such as aluminum, chromium, or titanium oxide. The thin metal wires may be arranged in one direction. The first semi-transmitting mirror 11 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 retardation film 12. In this example, the metal nanowire grid provides the first semi-transmitting mirror 11 with a reflective polarization function. However, the first semi-transmitting mirror 11 may simply be a half mirror with a separate reflective polarizer.

[0044] The second semi-transmitting mirror 13 is located between the first retardation plate 12 and the second retardation plate 14. The second semi-transmitting mirror 13 may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remaining portion (e.g., approximately 50%). The second semi-transmitting mirror 13 has a reflective surface 13a. The second semi-transmitting mirror 13 faces the first retardation plate 12. More specifically, as shown in FIG. 4, the second semi-transmitting mirror 13 may be a plane mirror positioned so that the reflective surface 13a faces the first retardation plate 12. The second semi-transmitting mirror 13 is also referred to as a plane half mirror. The second semi-transmitting mirror 13 may be integrated with at least one of the first retardation plate 12 and the second retardation plate 14, as shown in FIG. 31.

[0045] The second semi-transparent mirror 13 may be configured to include, 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 configured from, for example, inorganic glass, a resin material, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The semi-transparent reflective layer may be a metal thin film. The metal thin film may be configured from a metal material such as aluminum, chromium, or the like. The semi-transparent reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, or the like.

[0046] The polarizing plate 15 is positioned opposite to the surface of the second retardation plate 14 that faces the second semi-transmitting mirror 13. In other words, the polarizing plate 15 is positioned after the second retardation plate 14 in the emission direction 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 retardation plate 14, as shown in FIG. 31 .

[0047] The polarizing plate 15 may have the configuration of a known absorptive polarizing plate. Examples of known absorptive polarizing plates include an iodine-based polarizing plate in which an iodine compound is adsorbed and aligned on a polyvinyl alcohol (PVA) film, and a dye-based polarizing plate in which a dichroic organic dye is adsorbed and aligned on a PVA film.

[0048] The optical function of the optical system 10 will be described. S-wave polarized display light (first linearly polarized light L1) emitted from the display panel 2 passes through the first semi-transparent mirror 11. The first linearly polarized display light L1 passes through the first retardation plate 12 and is converted into first circularly polarized light C1. The first circularly polarized light C1 enters the second semi-transparent mirror 13. A portion (e.g., approximately 50%) of the first circularly polarized light C1 is reflected by the second semi-transparent mirror 13 and converted into second circularly polarized light C2. The second circularly polarized light C2 passes through the first retardation plate 12 and is converted into second linearly polarized light L2 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., P-wave polarized light). The second linearly polarized light L2 is reflected by the first semi-transparent mirror 11 and converted into third linearly polarized light L3 whose polarization direction is orthogonal to that of the first linearly polarized light L1. The third linearly polarized light L3 passes through the first retardation plate 12 and is converted into the third circularly polarized light C3. A portion (e.g., approximately 50%) of the third circularly polarized light C3 passes through the second semi-transparent mirror 13. The third circularly polarized light C3 that passed through the second semi-transparent mirror 13 passes through the second retardation plate 14 and is converted into the fourth linearly polarized light L4 whose polarization direction is orthogonal to the first linearly polarized light L1 (i.e., P-wave polarization). The fourth linearly polarized light L4 passes through the polarizing plate 15 and is emitted to the outside.

[0049] The remaining portion (e.g., approximately 50%) of the first circularly polarized light C1 passes through the second semi-transparent mirror 13 and then the second retardation plate 14, where it is converted into fifth linearly polarized light L5 whose polarization direction is parallel to that of the first linearly polarized light L1 (i.e., S-wave polarized light). The fifth linearly polarized light L5 is absorbed by the polarizing plate 15 and is not emitted to the outside. In other words, the fifth linearly polarized light L5 is light that is only slightly transmitted through the polarizing plate 15. Therefore, the amount of light (brightness) of the light emitted from the display device 1A is, for example, approximately 25% of the amount of light (brightness) of the display light emitted from the display panel 2.

[0050] In the above, an example has been described in which first retardation plate 12 and second retardation plate 14 are quarter-wave plates, but first retardation plate 12 and second retardation plate 14 may be other wave plates or a combination thereof instead of quarter-wave plates, as long as part of the light is absorbed by polarizing plate 15 and part of the light is transmitted through polarizing plate 15. Furthermore, first retardation plate 12 and second retardation plate 14 may be other wave plates or a combination thereof instead of quarter-wave plates, as long as part of the light is reflected by first semi-transparent mirror 11 and part of the light is transmitted through first semi-transparent mirror 11.

[0051] First semi-transmitting mirror 11, first retardation plate 12, second semi-transmitting mirror 13, second retardation plate 14, and polarizing plate 15 are held by a holding member (not shown), thereby maintaining their relative positions. Air is interposed between first semi-transmitting mirror 11 and first retardation plate 12. Display device 1A is configured such that no member made of a resin material such as a polymer is provided between first semi-transmitting mirror 11 and first retardation plate 12. This reduces the risk of deformation of first semi-transmitting mirror 11 or misalignment between first semi-transmitting mirror 11 and first retardation plate 12 occurring when the resin material is cured during the manufacturing process of display device 1A. As a result, degradation of display quality can be reduced.

[0052] Since the optical system 10 is an on-axis optical system in which the optical axis of the incident light and the optical axis of the outgoing light are substantially aligned, it is possible to reduce the space occupied by the optical system 10, thereby enabling the miniaturization of the display device 1A. Furthermore, since the optical system 10 is on-axis, it is possible to reduce distortion, brightness unevenness, etc. of the virtual image V visually recognized by the user 22, and it also becomes easier to design the optical system 10.

[0053] Like the display device 1, the display device 1A may include an optical element 9. In this case, the display device 1A allows 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 may be located after the polarizing plate 15 in the emission direction of the display light, or may be located between the first semi-transparent mirror 11 and the first retardation plate 12.

[0054] Next, another example of the display device 1A will be described. The display device 1A' of this example is different from the above-described display device 1A in the configuration (shape) of the second semi-transparent mirror, but has the same configuration as the other parts. Therefore, the same components are given the same reference numerals and detailed description will be omitted.

[0055] 5, the display device 1A' of this example includes a display panel 2 and an optical system 10. The optical system 10 includes a first semi-transparent mirror 11, a first retardation plate 12, a second semi-transparent mirror 13', a second retardation plate 14, and a polarizing plate 15. That is, the optical system 10 includes a pair of semi-transparent mirrors (first semi-transparent mirror 11, second semi-transparent mirror 13'), the first semi-transparent mirror 11, the first retardation plate 12, the second semi-transparent mirror 13', the second retardation plate 14, and the polarizing plate 15, which are arranged in this order in the direction in which display light from the display panel 2 is emitted.

[0056] Second semi-transmitting mirror 13' has a convex reflective surface 13'a. Second semi-transmitting mirror 13' faces first retardation plate 12; more specifically, reflective surface 13'a faces first retardation plate 12. Second semi-transmitting mirror 13' is also referred to as a convex half mirror. Second semi-transmitting mirror 13' may transmit a portion (e.g., approximately 50%) of incident light and reflect the remaining portion (e.g., approximately 50%). In this case, the reflective surface of second semi-transmitting mirror 13' diverges light that is incident from the first semi-transmitting mirror 11 side and reflected, while the reflective surface of first semi-transmitting mirror 11 converges light that is incident from the second semi-transmitting mirror 13 side and reflected.

[0057] The second semi-transparent mirror 13' may be configured to include, 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 configured from, for example, inorganic glass, a resin material, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The semi-transparent reflective layer may be a metal thin film. The metal thin film may be configured from a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, or the like.

[0058] The optical system 10 may be configured so 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 so that the second semi-transparent mirror 13' projects a reduced virtual image Q' (see FIG. 7) of the object (i.e., the display surface 2a). Furthermore, the optical system 10 may be configured so 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 so 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 is possible to adjust the magnification and projection distance of the virtual image V while reducing the thickness of the optical system 10 in the depth direction (Z-axis direction).

[0059] First semi-transmitting mirror 11, first retardation plate 12, second semi-transmitting mirror 13′, second retardation plate 14, and polarizing plate 15 are held by a holding member (not shown), thereby maintaining their relative positions. Air is interposed between first semi-transmitting mirror 11 and first retardation plate 12. Display device 1A′ is configured so that no member made of a resin material such as a polymer is provided between first semi-transmitting mirror 11 and first retardation plate 12. This reduces the risk of deformation of first semi-transmitting mirror 11 or misalignment between first semi-transmitting mirror 11 and first retardation plate 12 occurring when the resin material is cured during the manufacturing process of display device 1A′. As a result, degradation of display quality can be reduced.

[0060] Since the optical system 10 is an on-axis optical system in which the optical axis of the incident light and the optical axis of the outgoing light are substantially aligned, the space occupied by the optical system 10 can be reduced, and as a result, the display device 1A' can be made smaller. Furthermore, since the optical system 10 is on-axis, distortion and brightness unevenness of the virtual image V viewed by the user 22 can be reduced, and the design of the optical system 10 becomes easier.

[0061] The display device 1A' may include an optical element 9, in which case the user 22 can view the stereoscopic virtual image V.

[0062] 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), thereby providing a thin display device. Hereinafter, the thinning of the optical system 10 will be described with reference to FIGS. 6 and 7. The first semi-transmitting mirror 11 of the display devices 1A and 1A' has a concave reflecting surface 11a that reflects the display light emitted to the outside, and therefore, hereinafter, the first semi-transmitting mirror 11 will be referred to as a concave mirror. The second semi-transmitting mirror 13 of the display device 1A has a planar reflecting surface 13a that reflects the display light emitted to the outside, and therefore, hereinafter, the second semi-transmitting mirror 13 will be referred to as a flat mirror. The second semi-transmitting mirror 13' of the display device 1A' has a convex reflecting surface 13'a that reflects the display light emitted to the outside, and therefore, hereinafter, the second semi-transmitting mirror 13' will be referred to as a convex mirror. Furthermore, the dimension of the optical system 10 in the depth direction (Z-axis direction) will be referred to as the thickness of the optical system 10.

[0063] FIG. 6 is a diagram illustrating the projection of virtual image V in display device 1A. In FIG. 6, illuminator 4 and optical components (first retardation plate 12, second retardation plate 14, and polarizing plate 15) that do not contribute to the projection distance (virtual image distance) and magnification of virtual image V are omitted. Furthermore, concave mirror 11 is disposed so as to be in contact with display panel 2 so that the distance between display panel 2 and concave mirror 11 can be considered to be "0." In the following description, the focal length of concave mirror 11 is defined as f, and the distance between concave mirror 11 and plane mirror 13 is defined as a / 2. The distance a / 2 corresponds to the thickness of optical system 10 of display device 1A.

[0064] Display device 1A is configured to enlarge virtual image Q on display surface 2a by plane mirror 13 using concave mirror 11 and project it as virtual image V. As shown in FIG. 6, virtual image Q is located on the opposite side of plane mirror 13 from concave mirror 11, and is at a distance of a / 2 from plane mirror 13. Virtual image Q is an image of display surface 2a enlarged to the same magnification (1x).

[0065] The virtual image distance b and virtual image magnification m of the virtual image V are respectively expressed by the following formulas (1) and (2): 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 relative to the display surface 2a.

[0066] b=1 / (1 / a-1 / f) …(1) m=b / a …(2)

[0067] [Table 1]

[0068] Table 1 shows configuration examples 1 and 2 of display device 1A. The focal length f, thickness a / 2, and virtual image distance b shown in Table 1 are in mm. Configuration examples 1 and 2 are configured so that the virtual image distance b is 200 mm and the virtual image magnification m is 2 or 3. As shown in Table 1, when optical system 10 includes plane mirror 13, in order to set the virtual image distance b to 200 mm and the virtual image magnification m to 2, the thickness a / 2 of optical system 10 needs to be 50 mm (see configuration example 1), and in order to set the virtual image distance b to 200 mm and the virtual image magnification m to 3, the thickness a / 2 of optical system 10 needs to be 33.5 mm (see configuration example 2).

[0069] FIG. 7 is a diagram illustrating the projection of virtual image V in display device 1A'. In FIG. 7, illuminator 4 and optical components (first retardation plate 12, second retardation plate 14, and polarizing plate 15) that do not contribute to the projection distance (virtual image distance) and magnification of virtual image V are omitted. Concave mirror 11 is disposed in contact with display panel 2 so that the distance between display panel 2 and concave mirror 11 can be considered to be "0." In the following description, the focal length of convex mirror 13' is defined as f', the focal length of concave mirror 11 as f'', and the distance between concave mirror 11 and convex mirror 13' as a' / 2. The distance a' / 2 corresponds to the thickness of optical system 10 of display device 1A'.

[0070] 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 represented by the following formula (3). The magnification m’ of the virtual image Q’ with respect to the display surface 2a is represented 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.

[0071] 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 represented by the following formulas (5) and (6), 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 of the virtual image V with respect to the display surface 2a.

[0072] b’’ = 1 / {1 / (a’ / 2 + b’) - 1 / f’’} …(5) m’’ = (b’ / (a’ / 2)) × b’’ / (a’ / 2 + b’)…(6) Table 2 shows configuration examples 3 and 4 of the display device 1A’. The units of the focal lengths f’ and f’’, the thickness a’ / 2, and the virtual image distance b’’ shown in Table 2 are “mm”. Configuration examples 3 and 4 are configured, like configuration examples 1 and 2, to set the virtual image distance b’’ to 200 mm and the virtual image magnification m’’ to 2 or 3. As shown in Table 2, when the optical system 10 includes the convex mirror 13’, the optical system 10 having a thickness a’ / 2 of 32 mm can set the virtual image distance b’’ to 200 mm and the virtual image magnification m’’ to 2, similar to configuration example 1 (see configuration example 3), and the optical system 10 having a thickness a’ / 2 of 25.5 mm can set the virtual image distance b’’ to 200 mm and the virtual image magnification m’’ to 3, similar to configuration example 2 (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.

[0073] [Table 2]

[0074] In the display device 1A', when the values ​​of the virtual image distance b'', the virtual image magnification m'', and the thickness a' / 2 are given, the optical system 10 can be designed to realize them.

[0075] The design of the optical system 10 of the display device 1A' will be described below with reference to FIG. 8. Similar to FIG. 7, the illuminator 4, the first retardation film 12, the second retardation film 14, and the polarizing film 15 are omitted in FIG. 8. The concave mirror 11 is disposed in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be considered to be zero. In the following description, the thickness of the optical system 10 is defined as a1, the distance between the convex mirror 13' and the virtual image Q' is defined as b1, and the distance between the concave mirror 11 and the virtual image V is defined as b2. The magnification of the virtual image Q' relative to the display surface 2a is defined as m1, and the magnification of the virtual image V relative to the virtual image Q' is defined as m2. Furthermore, the focal length of the convex mirror 13' is defined as f1, and the focal length of the concave mirror 11 is defined as f2.

[0076] The magnification M of the virtual image V relative to the display surface 2a is expressed as the product of the magnification m1 and the magnification m2, as shown in the following equation (7). Also, the distance a2 between the concave mirror 11 and the virtual image Q' is expressed as the sum of the thickness a1 and the distance b1, as shown in the following equation (8).

[0077] M = m1 × m2 …(7) a2=a1+b1 …(8) When the thickness a1 of the optical system 10 is defined as T and the virtual image distance (that is, the distance b1 between the concave mirror 11 and the virtual image V) is defined as D, the magnification M is expressed by the following equation (9).

[0078] M=m1×m2 =(b1 / a1)×(b2 / a2) =(b1 / T)×(D / a2) …(9) When the following equation (10), which holds true for the distance b1 between the convex mirror 13' and the virtual image Q', is substituted into equation (9), the following equation (11) is obtained.

[0079] 1 / a1=1 / b1+1 / f1 …(10) M = f1 × (1 + D / f2) / (T + f1) … (11) Furthermore, when the following equation (12), which holds true for the distance b2 between the concave mirror 11 and the virtual image V, is substituted into equation (8), the following equation (13) is obtained.

[0080] 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 convex mirror 13' and the focal length f2 of concave mirror 11 can be calculated as shown in the following equations (14) and (15). A in equation (15) is expressed by the following equation (16).

[0081] 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, when the magnification ratio M, thickness T, and virtual image distance D are given, the focal lengths f1 and f2 of the display device 1A' can be determined (i.e., the optical system 10 can be designed) to achieve these values.

[0082] In the display devices 1A and 1A', the optical path length of light emitted from the display panel 2, transmitted through the first semi-transmitting mirror 11, reflected by the second semi-transmitting mirror 13 and 13', and reaching the first semi-transmitting mirror 11 may be shorter than the focal length of the first semi-transmitting mirror 11. In this case, the user 22 can view a virtual image V. In the display devices 1A and 1A', the optical path length of light emitted from the display panel 2, transmitted through the first semi-transmitting mirror 11, reflected by the second semi-transmitting mirror 13 and 13', and reaching the first semi-transmitting mirror 11 may be longer than the focal length of the first semi-transmitting mirror 11. In this case, the user 22 can view a real image.

[0083] Next, a display device according to still another embodiment of the present disclosure will be described. The display device of this embodiment is different from the display device of the above embodiment in the configuration of the optical system, but otherwise has the same configuration. Therefore, the same configurations are assigned the same reference numerals and detailed descriptions are omitted.

[0084] The display device 1B of this embodiment includes a display panel 2 and an optical system 16, as shown in FIG.

[0085] The optical system 16 includes a first semi-transmitting mirror 17, a first retardation plate 18, a second semi-transmitting mirror 19, a second retardation plate 20, and a third semi-transmitting mirror 21. The first semi-transmitting mirror 17, the first retardation plate 18, the second semi-transmitting mirror 19, the second retardation plate 20, and the third semi-transmitting mirror 21 are arranged in this order in the direction of emission of display light from the display panel 2. The first semi-transmitting mirror 17 and the third semi-transmitting mirror 21 have the function of collecting or converging light. In this embodiment, the first semi-transmitting mirror 17 and the third semi-transmitting mirror 21 have, for example, a greater degree of collection, a greater degree of convergence, or an index expressed as the reciprocal of the focal length than the other components of the optical system 16.

[0086] The first retardation plate 18 is positioned opposite the first semi-transmitting mirror 17. For example, the first retardation plate 18 is positioned opposite the reflecting surface 17a of the first semi-transmitting mirror 17. The first semi-transmitting mirror 17 has a function of collecting or converging light that is incident on and reflected by the reflecting surface 17a of the first semi-transmitting mirror 17. The first retardation plate 18 is positioned away from the display surface 2a in the emission direction of the display light from the display panel 2. The second retardation plate 20 is positioned away from the first retardation plate 12 in the emission direction of the display light. The first retardation plate 18 and the second retardation plate 20 are quarter-wave plates.

[0087] The first semi-transmitting mirror 17 is located between the display panel 2 and the first retardation film 18. The first semi-transmitting mirror 17 may transmit a portion of the incident light and reflect the remainder. In this embodiment, the first semi-transmitting mirror 17 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. As shown in FIG. 9 , the first semi-transmitting mirror 17 may be a concave mirror having a concave reflective surface 17a facing the first retardation film 18. At least a portion of the reflective surface 17a of the first semi-transmitting mirror 17 may include a spherical, aspherical, or free-form surface shape.

[0088] The first semi-transmitting mirror 17 may include, for example, a substrate and a plurality of thin metal wires (metal nanowire grid) positioned on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light range. The substrate may be made of, for example, a resin material, a glass material, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The thin metal wires may be made of a metal material, for example, aluminum, chromium, or titanium oxide. The thin metal wires may be arranged in one direction. The first semi-transmitting mirror 17 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 facing the first retardation plate 18. In this example, the metal nanowire grid provides the first semi-transmitting mirror 11 with a reflective polarization function. However, the first semi-transmitting mirror 11 may simply be a half mirror with a separate reflective polarizer.

[0089] The second semi-transmitting mirror 19 is located between the first retardation plate 18 and the second retardation plate 20. The second semi-transmitting mirror 19 may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remaining portion (e.g., approximately 50%). The second semi-transmitting mirror 19 faces the first retardation plate 18. More specifically, as shown in FIG. 9, the second semi-transmitting mirror 19 may be a plane mirror having a reflective surface 19a facing the first retardation plate 18 and a reflective surface 19b facing the second retardation plate 20. The second semi-transmitting mirror 19 is also referred to as a plane half mirror. As shown in FIG. 32, the second semi-transmitting mirror 19 may be integrated with at least one of the first retardation plate 18 and the second retardation plate 20.

[0090] The second semi-transmitting mirror 19 may include, for example, a substrate and a semi-transmitting 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, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The semi-transmitting layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum or chromium. The semi-transmitting layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film. The first retardation plate 18 and the second retardation plate 20 may be fixed to the second semi-transmitting mirror 19 by an optically transparent adhesive such as OCA (Optically Clear Adhesive). The adhesive may be a material with low retardation.

[0091] The third semi-transmitting mirror 21 is positioned opposite the surface of the second retardation plate 20 opposite to the surface facing the second semi-transmitting mirror 19. The third semi-transmitting mirror 21 is positioned after the second retardation plate 20 in the emission direction of display light from the display panel 2. The third semi-transmitting mirror 21 may transmit a portion of the incident light and reflect the remainder. In this embodiment, the third semi-transmitting mirror 21 may be configured to reflect S-wave polarized light and transmit P-wave polarized light. As shown in FIG. 9 , the third semi-transmitting mirror 21 may be a concave mirror having a concave reflective surface 21a facing the second retardation plate 20. The third semi-transmitting mirror 21 has a function of focusing light that is incident on and reflected by the reflective surface 21a of the third semi-transmitting mirror 21. At least a portion of the reflective surface 21a of the third semi-transmitting mirror 21 may include a spherical, aspherical, or free-form surface shape.

[0092] The third semi-transmitting mirror 21 may include, for example, a substrate and a plurality of thin metal wires (metal nanowire grid) positioned on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light range. The substrate may be made of, for example, a resin material, a glass material, or the like. The resin material may be, for example, an acrylic resin, a polycarbonate resin, or the like. The thin metal wires may be made of a metal material, for example, aluminum, chromium, or titanium oxide. The thin metal wires may be arranged in one direction. The third semi-transmitting 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 retardation plate 20. In this example, the metal nanowire grid provides the third semi-transmitting mirror 21 with a reflective polarization function. However, the third semi-transmitting mirror 21 may be a simple half mirror with a separate reflective polarizer.

[0093] The optical function of the optical system 16 will now be described. In the display device 1B, display light emitted from the display panel 2 may travel along path P1 or path P2 and be emitted to the outside. First, light traveling along path P1 will be described. The S-wave polarized display light (first linearly polarized light L1) emitted from the display panel 2 passes through the first semi-transparent mirror 17. The first linearly polarized light L1 passes through the first retardation plate 18 and is converted into first circularly polarized light C1. The first circularly polarized light C1 enters the second semi-transparent mirror 19. A portion (e.g., approximately 50%) of the first circularly polarized light C1 is reflected by the second semi-transparent mirror 19 and converted into second circularly polarized light C2. The second circularly polarized light C2 passes through the first retardation plate 18 and is converted into second linearly polarized light L2 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., P-wave polarized light). The second linearly polarized light L2 is reflected by the first semi-transparent mirror 17 and converted into third linearly polarized light L3, whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., P-polarized light). The third linearly polarized light L3 passes through the first retardation plate 18 and is converted into third circularly polarized light C3. The third circularly polarized light C3 enters the second semi-transparent mirror 19. A portion (e.g., approximately 50%) of the third circularly polarized light C3 passes through the second semi-transparent mirror 19. The third circularly polarized light C3 that passed through the second semi-transparent mirror 19 passes through the second retardation plate 20 and is converted into fourth linearly polarized light L4, whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., P-polarized light). The fourth linearly polarized light L4 passes through the third semi-transparent mirror 21 and is emitted to the outside.

[0094] Next, the light traveling along path P2 will be described. The remainder (e.g., approximately 50%) of the light of the first circularly polarized light C1 incident on the second semi-transparent mirror 19 is transmitted through the second semi-transparent mirror 19. The light of the first circularly polarized light C1 transmitted through the second semi-transparent mirror 19 is transmitted through the second retardation plate 20 and converted into light of fifth linearly polarized light L5 whose polarization direction is parallel to that of the first linearly polarized light L1 (i.e., S-wave polarization). The light of the fifth linearly polarized light L5 is reflected by the third semi-transparent mirror 21 and converted into light of sixth linearly polarized light L6 whose polarization direction is parallel to that of the first linearly polarized light L1 (i.e., S-wave polarization). The light of the sixth linearly polarized light L6 is transmitted through the second retardation plate 20 and converted into light of fourth circularly polarized light C4. The light of the fourth circularly polarized light C4 is incident on the second semi-transparent mirror 19. A portion (e.g., approximately 50%) of the fourth circularly polarized light C4 is reflected by the second semi-transparent mirror 19 and converted into fifth circularly polarized light C5. The fifth circularly polarized light C5 passes through the second retardation plate 20 and is converted into seventh linearly polarized light L7 whose polarization direction is orthogonal to the first linearly polarized light L1 (i.e., P-polarized light). The seventh linearly polarized light L7 passes through the third semi-transparent mirror 21 and is emitted to the outside.

[0095] 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 (brightness) of the light emitted from the display device 1B is, for example, approximately 50% of the amount of light (brightness) of the display light emitted from the display panel 2. The display device 1B can increase the light utilization efficiency and can improve the brightness of the light emitted to the outside.

[0096] In the above, an example has been described in which first retardation plate 18 and second retardation plate 20 are quarter-wave plates, but first retardation plate 18 and second retardation plate 20 may be other wave plates or a combination thereof instead of quarter-wave plates, as long as part of the light is reflected by first semi-transparent mirror 17 and part of the light is transmitted through first semi-transparent mirror 17. Furthermore, first retardation plate 18 and second retardation plate 20 may be other wave plates or a combination thereof instead of quarter-wave plates, as long as part of the light is reflected by third semi-transparent mirror 21 and part of the light is transmitted through third semi-transparent mirror 21.

[0097] First semi-transmitting mirror 17, first retardation plate 18, second semi-transmitting mirror 19, second retardation plate 20, and third semi-transmitting mirror 21 are held by a holding member (not shown), thereby maintaining their relative positions. Air is interposed between first semi-transmitting mirror 17 and first retardation plate 18 and between third semi-transmitting mirror 21 and second retardation plate 20. Display device 1B is configured such that no members made of a resin material such as polymer are provided between first semi-transmitting mirror 17 and first retardation plate 18 and between third semi-transmitting mirror 21 and second retardation plate 20. This reduces the risk of deformation of first semi-transmitting mirror 11 and misalignment between first semi-transmitting mirror 11 and first retardation plate 12. As a result, degradation of display quality can be reduced.

[0098] Since optical system 16 is a uniaxial (on-axis) optical system in which the optical axis of the incident light and the optical axis of the outgoing light are substantially aligned, it is possible to reduce the space occupied by optical system 16, thereby enabling the miniaturization of display device 1B. Furthermore, since optical system 16 is a uniaxial type, it is possible to reduce distortion, brightness unevenness, etc. of virtual image V visually recognized by user 22, and it also becomes easier to design optical system 16.

[0099] Display device 1B may be configured such that the focal length of first semi-transparent mirror 17 is equal to the focal length of third semi-transparent mirror 21, and second semi-transparent mirror 19 is a plane mirror. In this case, in an imaging device including 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 with each other, thereby improving display quality.

[0100] In display device 1B, the optical path length of light emitted from display panel 2, transmitted through first semi-transmitting mirror 17, reflected by second semi-transmitting mirror 19, and reaching first semi-transmitting mirror 17 may be shorter than the focal length of first semi-transmitting mirror 17, and the optical path length of light emitted from display panel 2, transmitted through first semi-transmitting mirror 17, transmitted through second semi-transmitting mirror 19, and reaching third semi-transmitting mirror 21 may be shorter than the focal length of first semi-transmitting mirror 17. In this case, user 22 can view virtual image V. In display device 1B, the optical path length of light emitted from display panel 2, transmitted through first semi-transmitting mirror 17, reflected by second semi-transmitting mirror 19, and reaching first semi-transmitting mirror 17 may be longer than the focal length of first semi-transmitting mirror 17, and the optical path length of light emitted from display panel 2, transmitted through first semi-transmitting mirror 17, transmitted through second semi-transmitting mirror 19, and reaching third semi-transmitting mirror 21 may be longer than the focal length of first semi-transmitting mirror 17. In this case, user 22 can view a real image.

[0101] Next, an imaging device according to an 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 allows a user 22 to view display light emitted from a display panel 2 as a virtual image V. Since the imaging device 100 includes the 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 the display device 1A', a thin imaging device can be realized. The imaging device 100 may allow a user 22 to view display light emitted from the display panel 2 as a real image.

[0102] The imaging device 100 may be mounted on a moving object 23 as shown in FIG. 10. The moving object 23 may be a vehicle. FIG. 10 shows a case where the vehicle is a passenger car, but the vehicle is not limited to a passenger car and may be an automobile such as a truck, a bus, or a trolleybus. The display devices 1, 1A, 1A', and 1B may be positioned arbitrarily inside the moving object 23. The display devices 1, 1A, 1A', and 1B may be positioned on the dashboard (instrument panel), inside the dashboard, on the ceiling of the passenger compartment, on an A-pillar, or the like. Part of the configuration of the imaging device 100 may be shared with other devices or components provided in the moving object 23.

[0103] As shown in Fig. 10, the imaging device 100 may include a camera 102 that captures an image of a scene behind the moving object 23. The camera 102 may include, for example, a charge coupled device (CCD) imaging element or a complementary metal oxide semiconductor (CMOS) imaging element. The imaging device 100 and the camera 102 are connected via 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 control area network (CAN).

[0104] The imaging device 100 may be configured to display at least a portion of an image captured by the camera 102 on the display panel 2. In this case, the imaging device 100 allows the user 22 (the driver of the mobile object 23) to visually recognize the scenery behind the mobile object 23 as a virtual image V formed on a side farther from the imaging device 100. As a result, the user 22 can visually recognize the scenery behind the mobile object 23 without significantly changing the gaze distance (gazing point) while driving the mobile object 23, making it easier to visually recognize the virtual image V and improving driving safety. In addition, since the imaging device 100 is a compact imaging device, even when placed in the driver's cab of the mobile object 23, it does not occupy a large volume in the cab and is unlikely to interfere with driving. The imaging device 100, which is mounted on the mobile object 23 and configured to allow the user 22 to visually recognize the scenery behind the mobile object 23 as a virtual image V, is also referred to as a digital rearview mirror.

[0105] In the imaging device 100, the display devices 1, 1A, 1A', and 1B may each include an optical element 9 (see FIG. 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 therebetween, emits display light for the left-eye image and display light for the right-eye image, and the optical element 9 causes 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 viewed by the user 22 as a stereoscopic virtual image V.

[0106] 11 , the imaging device 100 may include a reflective optical element 101. 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 causes part of the display light to reach the eyes of the user 22. When the imaging device 100 is mounted on a moving object 23, the imaging device 100 may also use the windshield 24 of the moving object 23 as the reflective optical element 101.

[0107] The imaging device 100 may be applied to a digital side mirror. In this case, as shown in Fig. 12, the imaging device 100 may include a display device 1, 1A, 1A', 1B (hereinafter also referred to as a left display device 1L) located on an A-pillar on the left side of the moving object 23, a camera 102 (hereinafter also referred to as a left camera 102L) that captures an image of the left rear of the moving object 23, a display device 1, 1A, 1A', 1B (hereinafter also referred to as a right display device 1R) located on an A-pillar on the right side of the moving object 23, and a camera 102 (hereinafter also referred to as a right camera 102R) that captures an image of the right rear of the moving object 23. The left display device 1L may allow the user 22 to visually recognize an image of the left rear of the moving object 23 captured by the left camera 102L as a virtual image V (hereinafter also referred to as a virtual image V2). The right-side display device 1R may allow the user 22 to view an image of the right rear of the moving object 23 captured by the right-side camera 102R as a virtual image V (hereinafter also referred to as virtual image V3). The image may be a moving image (also referred to as a video) or a still image. The left-side camera 102L may be located in the same position as the left door mirror, and the right-side camera 102R may be located in the same position as the right door mirror.

[0108] The imaging device 100 may be configured so that the distances between the eyes (or eyebox) of the user 22 and the virtual images V2 and V3 are approximately the same. In this case, the user 22 can check the conditions behind the left and right sides of the moving object 23 without significantly changing the gaze distance (the distance between the eyes of the user 22 and the gaze point at which the user 22 is gazing). This can improve driving safety. The eyebox refers to the area in real space where the eyes of the user 22 are assumed to be located.

[0109] The imaging device 100 may be configured so that the distances between the eyes (or eyeboxes) of the user 22 and the virtual images V1 to V3 are approximately the same. In this case, the user 22 can check the conditions immediately behind, to the left rear, and to the right rear of the moving object 23 without significantly changing the gaze distance. This can improve driving safety.

[0110] The imaging device 100 may be applied to a cluster 29 in the dashboard of a moving object 23 (see FIG. 12). In this case, the display devices 1, 1A, 1A', 1B may allow the user 22 to view an image showing information related to driving, such as vehicle speed, engine rotation speed, remaining fuel, etc., as a virtual image V (hereinafter also referred to as virtual image V4).

[0111] The imaging device 100 may be applied to a CID (Center Information Display) 30 (see FIG. 12). In this case, the display devices 1, 1A, 1A', and 1B may be arranged in a center cluster of a mobile object 23, and may allow a user 22 to view an image showing information about navigation, the in-vehicle environment (e.g., settings of an air conditioner, an audio device, etc.), etc., as a virtual image V (hereinafter also referred to as virtual image V5).

[0112] The imaging device 100 may be configured so that the distances between the eyes (or eyeboxes) of the user 22 and the virtual images V4 and V5 are approximately the same. In this case, the user 22 can check information about driving the mobile object 23, as well as information about navigation and the in-vehicle environment, without significantly changing the gaze distance. This can improve driving safety.

[0113] The imaging device 100 may be configured so that the distance between the eyes (or eyebox) of the user 22 and each of the virtual images V1 to V5 is approximately the same. In this case, the user 22 can see directly behind, behind the left side, and behind the right side of the moving object 23 without significantly changing the gaze distance, and can also check information related to the driving, navigation, and in-vehicle environment of the moving object 23. Therefore, driving safety can be improved.

[0114] The imaging device 100 may be applied to a PID (Passenger Information Display) 31 (see FIG. 12). In this case, the display devices 1, 1A, 1A', and 1B may be arranged on the dashboard near the passenger seat, and may allow the passenger to view images of entertainment content and images showing information about an audio device, an air conditioning device, etc. as virtual images V.

[0115] The imaging device 100 may be applied to an RSE (Rear Seat Entertainment) system 32 (see FIG. 10). In this case, the display devices 1, 1A, 1A', 1B may be arranged on the back of the front seats, and may display images of entertainment content and images showing information about an audio device, an air conditioning device, etc. as virtual images V to passengers seated in the rear seats of the vehicle 23.

[0116] The display devices 1, 1A, 1A', and 1B may include a drive unit that adjusts the relative positions in the depth direction among the display panel 2, the semi-transmitting mirror 6, the first semi-transmitting mirrors 11 and 17, and the second semi-transmitting mirrors 13, 13', and 21. Image data of a display image displayed on the display panel 2 may include depth information that indicates 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 distances among the display panel 2, the semi-transmitting mirror 6, the first semi-transmitting mirrors 11 and 17, and the second semi-transmitting 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 be, for example, an electric slider, an electric cylinder, or the like. The drive unit may be configured so that the user 22 can manually adjust the relative positions between the display panel 2, the semi-transparent mirror 6, the first semi-transparent mirrors 11, 17 and the second semi-transparent mirrors 13, 13', 21.

[0117] Hereinafter, other examples of the display device of the present disclosure will be described.

[0118] 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 the present disclosure. In Figures 13 and 14, the first retardation plate 5, the second retardation plate 7, and the optical element 9 are omitted. The following description will be given using the display device 1 as an example, but the same applies to the display devices 1A, 1A', and 1B.

[0119] The display device 1 can constitute a part of an imaging device 100 (digital rearview mirror). In a normal rearview mirror, that is, a rearview mirror using a mirror, the image seen by the user's left eye (also called the left eyeglass image) and the image seen by the right eye (also called the right eyeglass image) are different, and the user recognizes the left eyeglass image and the right eyeglass image as mirror images seen by both eyes through the cognitive function of the brain.

[0120] The display device 1 may be configured so that the virtual image projected into the visual field of the user 22 has a binocular visible area (virtual image V in FIGS. 13 and 14 ) that is viewed by the left eye 22L and right eye 22R of the user 22, a left eye visible area VLa that is viewed only by the left eye 22L, and a right eye visible area VRa that is viewed only by the right eye 22R. In other words, when the virtual image viewed by the left eye 22L is defined as the left eye virtual image VL and the virtual image viewed by the right eye 22R is defined as the right eye virtual image VR, the left eye virtual image VL may have a left eye visible area VLa that is viewed only by the left eye 22L, and the right eye virtual image VR may have a right eye visible area VRa that is viewed only by the right eye 22R. Within the visual field of the user 22, 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 so that the right end 6R of the semi-transparent mirror 6 that is visible to the user 22 is located on a straight line connecting the left eye 22L and the right end VLR of the left-eye virtual image VL, and the left end 6L of the semi-transparent mirror 6 that is visible to the user 22 is located on a straight line connecting the right eye 22R and the left end VRL of the right-eye virtual image VR.

[0121] With this configuration, the range observed by the user 22 through the left eye virtual image VL and the range observed by the user 22 through the right eye virtual image VR are different, just like the left and right eyeglass images in a normal rearview mirror. Therefore, just like 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 virtual images V viewed by both eyes 22L, 22R through the cognitive functions of the brain. Therefore, it is possible to reduce the risk of the user 22 feeling uncomfortable.

[0122] In the display device 1, the size of the reflective surface of the reflective polarizer 8 on the display surface 2a side may be equal to or larger than the size of the display surface 2a. In this case, the reflective polarizer 8 can reflect the entire image on the display surface 2a toward the semi-transparent mirror 6. Furthermore, the display device 1 may be configured so that a virtual image VD (hereinafter also referred to as a display surface virtual image) formed when the entire image on the display surface 2a is projected into the field of view of the user 22 includes a left-eye virtual image VL and a 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 22 moves their head can be formed, i.e., a viewing region R into which the left eye 22L or the right eye 22R can look. As a result, the user 22 can view the left-eye virtual image VL and the right-eye virtual image VR, which change depending on the movement of their head, just as when using a normal rearview mirror. This reduces the risk of discomfort to the user 22. 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.

[0123] It is also possible to control the size of the looking-in area R by controlling the image display area A (area where the image is actually displayed) on the display surface 2a. Increasing the image display area A allows the looking-in area R to be enlarged. Reducing the image display area A allows the looking-in area R to be reduced. When the image display area A becomes smaller than a predetermined threshold area, the looking-in area R disappears, and the left eye virtual image VL and the right eye virtual image VR can be made the same virtual image.

[0124] As described above, the display device 1 may include a housing 27. The housing 27 may have an opening 28 on its front side (the side facing the user 22). Within the field of view of the user 22, the virtual image V may be larger than the opening 28. The size of the viewing region R can also be controlled by the size of the opening 28. As shown in FIG. 14 , by appropriately designing the size of the opening 28, it is possible to form a left-eye virtual image VL including an area that cannot be viewed by the right eye 22R and a right-eye virtual image VR including an area that cannot be viewed by the left eye 22L. Furthermore, by appropriately designing the size of the opening 28, it is possible to form the viewing region R and control the size of the viewing region R. When the size of the viewing region R is controlled by the opening 28, the size of the semi-transparent mirror 6 only needs to be large enough to project the entire image of the display surface 2a into the field of view of the user 22, which simplifies the design of the optical system 3.

[0125] The same applies to the display devices 1A, 1A', and 1B. The display devices 1A, 1A', and 1B may be configured so that the virtual image projected into the field of view of the user 22 has a binocular visible region visible with the left eye 22L and the right eye 22R, a left-eye visible region visible only with the left eye 22L, and a right-eye visible region visible only with the right eye 22R. In this case, the risk of causing discomfort to the user 22 can be reduced. The display devices 1A and 1A' may be configured so that the right edge of the first semi-transmitting mirror 11 visible to the user 22 is located on a line connecting the left eye 22L and the right edge of the left-eye virtual image, and the left edge of the first semi-transmitting mirror 11 visible to the user 22 is located on a line connecting the right eye 22R and the left edge of the right-eye virtual image. Display device 1B may be configured such that the right ends of first semi-transmitting mirror 17 and third semi-transmitting mirror 21 that are visible to user 22 are located on a line connecting left eye 22L and the right end of the left-eye virtual image, and the left ends of first semi-transmitting mirror 17 and third semi-transmitting mirror 21 that are visible to user 22 are located on a line connecting right eye 22R and the left end of the right-eye virtual image. Display device 1A, 1A', 1B may be configured to have a viewing region R. Display device 1A, 1A', 1B may be configured such that the size of viewing region R is controlled by image display region A, or may be configured such that the size of viewing region R is controlled by opening 28 of housing 27.

[0126] Next, other examples of the display devices 1, 1A, and 1A' will be described. Figures 15 and 16 are cross-sectional views illustrating the other examples of the display device, Figures 17A to 17D and 18A to 18D are diagrams illustrating the optical system in the other examples of the display device, and Figure 19 is a graph illustrating the optical system in the other examples of the display device. In the following, the display device 1 will be described as an example, but the same applies to the display devices 1A and 1A'.

[0127] The display device 1 is configured so that, when the user 22 is positioned in front of the display device 1, the light of the second linearly polarized light L2 is reflected by the reflective polarizer 8 and does not exit from the display device 1 (see FIGS. 2 and 3). In other words, the display device 1 is configured so that, when viewed from the front of the display device 1, 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 configuration). As a result, as shown in FIGS. 2 and 3, the light of the second linearly polarized light L2 does not exit from the display device 1, and the light of the fourth linearly polarized light L4 exits from the display device 1. In other words, the user 22 does not directly view the display panel 2, but rather views the image reflected by the semi-transparent mirror 6 as a virtual image V.

[0128] If the user 22 is not positioned in front of the display device 1, the crossed Nicol arrangement between the transmission axis of the front polarizer of the display panel 2 and the transmission axis of the reflective polarizer 8 is disrupted, and part of the light of the second linearly polarized light L2 may be transmitted through the reflective polarizer 8. As a result, the user 22 may be able to see both the real image seen when looking directly at the display panel 2 and the virtual image V reflected by the semi-transparent mirror 6, which may degrade the display quality of the display device 1.

[0129] As shown in FIGS. 15 and 16 , the display device 1 of this example has a third retardation plate 25 positioned 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 approach a crossed Nicol arrangement, even when the user 22 is not positioned in front of the display device 1, thereby reducing degradation in display quality of the display device 1. The third retardation plate 25 may be a half-wave plate (1 / 2 wave plate), a quarter-wave plate, an eighth-wave plate, a sixteenth-wave plate, or the like, or may be a wave plate that provides other retardation. The optical axis of the third retardation plate 25 may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer 8. The third retardation plate 25 may be positioned between the second retardation plate 7 and the reflective polarizer 8, or between the display panel 2 and the first retardation plate 5.

[0130] As shown in FIGS. 15 and 16 , the display device 1 of this example may further include a fourth retardation plate 26 positioned between the display panel 2 and the reflective polarizer 8. 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 closer to a crossed Nicol arrangement, thereby further reducing degradation in display quality of the display device 1. The fourth retardation plate 26 may be a half-wave plate (1 / 2 wave plate), a quarter-wave plate, an eighth-wave plate, a sixteenth-wave plate, or the like, or may be a wave plate that provides other retardation. The optical axis of the fourth retardation plate 26 may be approximately parallel or perpendicular to the transmission axis of the reflective polarizer 8. The fourth retardation plate 26 may be positioned between the second retardation plate 7 and the reflective polarizer 8, or between the display panel 2 and the first retardation plate 5.

[0131] The third retardation plate 25 and the fourth retardation plate 26 may be positioned arbitrarily as long as they are located between the display panel 2 and the reflective polarizer 8. If no other optical element is located between the third retardation plate 25 and the fourth retardation plate 26, the third retardation plate 25 and the fourth retardation 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 retardation plate 25 and the fourth retardation plate 26 may be approximately parallel to or approximately perpendicular to the transmission axis of the reflective polarizer 8, and the optical axis of the third retardation plate 25 may be approximately perpendicular to the optical axis of the fourth retardation plate 26.

[0132] One of the third retardation film 25 and the fourth retardation film 26 may be a quarter-wave plate and the other a half-wave plate. In this case, degradation of the display quality of the display device 1 can be effectively reduced. Both the third retardation film 25 and the fourth retardation film 26 may be half-wave plates. In this case, degradation of the display quality of the display device 1 can be more effectively reduced.

[0133] 17A, 17B, 17C, and 17D are Poincaré spheres showing the optical functions (effects on the polarization state of light) of the third retardation plate 25 and the fourth retardation plate 26 when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates. FIGS. 17A and 17B are diagrams explaining the optical function of the third retardation plate 25, and FIGS. 17C and 17D are diagrams explaining the optical function of the fourth retardation plate 26. FIGS. 17A and 17C show the Poincaré sphere as viewed from the north pole (S3 axis direction), and FIGS. 17B and 17D show the Poincaré sphere as viewed from the side (S1 axis direction). In FIGS. 17A, 17B, 17C, and 17D, S LCD indicates the polarization state of light immediately after it is emitted from the display panel 2. 25 indicates the polarization state of the light that has passed through the third retardation plate 25, and S 26 indicates the polarization state of the light that has passed through the fourth retardation plate 26. 26 It can be said that S represents the polarization state of the light immediately before it enters the reflective polarizer 8. RP indicates the polarization state of light that passes through the reflective polarizer 8 with substantially 100% transmittance, and S AP is S RPThe antipodal point of (the point symmetric with respect to the center of the Poincaré sphere) S 26 S AP Located in or S AP When the third retardation film 25 and the fourth retardation film 26 are positioned in the vicinity of the reflective polarizer 8, it is possible to reduce the risk that the light that has been emitted from the display panel 2 and passed through the third retardation film 25 and the fourth retardation film 26 will be transmitted through the reflective polarizer 8. As a result, it is possible to reduce the risk that the user 22 will see a real image when looking directly at the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0134] 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 essentially S AP Therefore, it is possible to reduce the risk that the user 22 will see a real image when looking directly at the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0135] 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 explaining the optical function of the third retardation plate 25, and FIGS. 18C and 18D are diagrams explaining the optical function of the fourth retardation plate 26. FIGS. 18A and 18C show the Poincaré sphere as viewed from the north pole (S3 axis direction), and FIGS. 18B and 18D show the Poincaré sphere as viewed from the side (S1 axis direction). LCD , S 25 , S 26 , S RP and S AP is as described above.

[0136] 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 S AP Therefore, it is possible to reduce the risk that the user 22 will see a real image when looking directly at the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0137] FIG. 19 is a graph showing the relationship between the optical transmittance of an optical system having a third retardation plate 25 and a fourth retardation plate 26 inserted between polarizers PP1 and PP2 whose transmission axes are orthogonal to each other, and the retardation of the third retardation plate 25 and the fourth retardation plate 26. FIG. 19 shows the results obtained by simulation. The incident light was green light with a wavelength λ of 550 nm. The polarizer PP1, the third retardation plate 25, the fourth retardation plate 26, and the polarizer PP2 are arranged in this order in the direction of propagation of the incident light. The polarizer PP1 is modeled after the front polarizer of the display panel 2, and the polarizer PP2 is modeled after the reflective polarizer 8.

[0138] 19 shows the transmittance when the phase difference of the fourth retardation plate 26 is fixed at 0 nm and the phase difference of the third retardation plate 25 is changed, and is minimum when the phase difference of the third retardation plate 25 is about 275 nm (half the wavelength λ of the incident light). The dashed line in the graph of Fig. 19 shows the transmittance when the phase difference of the third retardation plate 25 is fixed at 270 nm and the phase difference of the fourth retardation plate 26 is changed, and is minimum when the phase difference of the fourth retardation plate 26 is about 275 nm (half the wavelength λ of the incident light).

[0139] 19, it can be seen that when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates, the display device 1 can effectively reduce the risk of the user 22 viewing a real image when looking directly at the display panel 2, and can effectively reduce degradation of the display quality of the display device 1. Furthermore, even when the retardation of the fourth retardation plate 26 is fixed to 0 nm (i.e., when the display device 1 has only the third retardation plate 25), it can be seen that the risk of the user 22 viewing a real image when looking directly at the display panel 2 can be effectively reduced, and degradation of the display quality of the display device 1 can be effectively reduced, as long as the third retardation plate 25 can impart a retardation greater than 0 nm (i.e., a non-zero value) to light incident on the third retardation plate 25.

[0140] The same applies to the display devices 1A and 1A'. The display devices 1A and 1A' may have a third retardation plate 25 positioned between the display panel 2 and the polarizing plate 15. In this case, it is possible to reduce the risk that the user 22 will see a real image when looking directly at the display panel 2, thereby reducing degradation in the display quality of the display devices 1A and 1A'. The display devices 1A and 1A' may further have a fourth retardation plate 26 positioned between the display panel 2 and the polarizing plate 15. In this case, it is possible to further reduce the risk that the user 22 will see a real image when looking directly at the display panel 2, thereby further reducing degradation in the display quality of the display devices 1A and 1A'. The third retardation plate 25 and the fourth retardation plate 26 may be a ½ wavelength plate (half wavelength plate), a ¼ wavelength plate, a ⅛ wavelength plate, a ⅙-sixteenth wavelength plate, or the like, or may be wavelength plates that impart other retardations. One of the third retardation film 25 and the fourth retardation film 26 may be a quarter-wave plate and the other a half-wave plate. In this case, degradation of the display quality of the display device 1 can be effectively reduced. Both the third retardation film 25 and the fourth retardation film 26 may be half-wave plates. In this case, degradation of the display quality of the display device 1 can be more effectively reduced. The third retardation film 25 and the fourth retardation film 26 may be located between the display panel 2 and the polarizing film 15, and their positions are arbitrary. The third retardation film 25 and the fourth retardation film 26 may be located between the second retardation film 14 and the polarizing film 15, or may be located between the display panel 2 and the first retardation film 12. The optical axes of the third retardation film 25 and the fourth retardation film 26 may be approximately parallel to or approximately perpendicular to the transmission axis of the polarizing film 15. The optical axes of the third retardation plate 25 and the fourth retardation plate 26 may be approximately parallel or perpendicular to the transmission axis of the polarizing plate 15, and the optical axis of the third retardation plate 25 may be approximately perpendicular to the optical axis of the fourth retardation plate 26.

[0141] Next, other examples of the display devices 1, 1A, 1A', and 1B will be described. Fig. 20 is a cross-sectional view showing another example of the display device 1A', and Fig. 21 is a cross-sectional view showing another example of the display device 1A. Descriptions of the configurations or parts described in the above embodiments may be omitted.

[0142] The second semi-transmitting mirror 13' of the display device 1A' may be configured to include a holographic optical element (HOE). In this case, as shown in FIG. 20, the optical function of the second semi-transmitting mirror 13' can be realized by a flat optical element, and the thickness of the second semi-transmitting mirror 13' in the depth direction (Z-axis direction) can be reduced. As a result, the display device 1A' can be made more compact in the depth direction. Furthermore, since the second semi-transmitting mirror 13' is a flat optical element, the distance between the second semi-transmitting mirror 13' and the second retardation plate 14 can be reduced, or the second semi-transmitting mirror 13' and the second retardation plate 14 can be brought into contact with each other, which makes it possible to further reduce the size of the display device 1A' in the depth direction.

[0143] The first semi-transmitting mirror 11 of the display device 1A' may be configured to include an HOE. In this case, as shown in FIG. 20 , the optical function of the first semi-transmitting mirror 11 can be realized by a flat optical element, and the thickness of the first semi-transmitting mirror 11 in the depth direction can be reduced. As a result, the display device 1A' can be made more compact in the depth direction. Furthermore, because the first semi-transmitting mirror 11 is a flat optical element, the distance between the first semi-transmitting mirror 11 and the display panel 2 can be reduced, or the first semi-transmitting mirror 11 and the display panel 2 can be brought into contact with each other, making it possible to further reduce the size of the display device 1A' in the depth direction.

[0144] If first semi-transparent mirror 11 does not have polarization selectivity, the amount of light emitted from display device 1A' will decrease, resulting in a decrease in the brightness of virtual image V viewed by user 22. Therefore, first semi-transparent mirror 11 including an HOE may be configured to have polarization selectivity. For example, first semi-transparent mirror 11 including an HOE may have a plurality of metal fine wires (metal nanowire grid) formed on the surface facing display panel 2 or the surface facing first retardation plate 12, which achieves polarization selectivity by transmitting S-wave polarized light and reflecting P-wave polarized light. In this case, the decrease in brightness of virtual image V viewed by user 22 can be reduced.

[0145] The first semi-transmitting mirror 11 of the display device 1A may include an HOE. In this case, as shown in FIG. 21 , the optical function of the first semi-transmitting mirror 11 can be realized by a flat optical element, thereby reducing the thickness of the first semi-transmitting mirror 11 in the depth direction. As a result, the display device 1A can be made more compact in the depth direction. Furthermore, since the first semi-transmitting mirror 11 is a flat optical element, the distance between the first semi-transmitting mirror 11 and the display panel 2 can be reduced, or the first semi-transmitting mirror 11 and the display panel 2 can be brought into contact with each other, thereby further reducing the size of the display device 1A in the depth direction. The first semi-transmitting mirror 11 including an HOE may have polarization selectivity. For example, the first semi-transmitting mirror 11 including an HOE may have multiple thin metal wires formed on the surface facing the display panel 2 or the surface facing the first retarder 12, which achieves polarization selectivity by transmitting S-wave polarized light and reflecting P-wave polarized light. In this case, the reduction in brightness of the virtual image V viewed by the user 22 can be reduced.

[0146] The semi-transmitting mirror 6 of the display device 1 may be configured to include an HOE. In this case, the optical function of the semi-transmitting mirror 6 can be realized by a flat optical element, and the thickness of the semi-transmitting 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, since the semi-transmitting mirror 6 is a flat optical element, the distance between the semi-transmitting mirror 6 and the first retardation plate 5 can be reduced, or the semi-transmitting mirror 6 and the first retardation plate 5 can be brought into contact with each other, which makes it possible to further reduce the size of the display device 1 in the depth direction.

[0147] The first semi-transmitting mirror 17 of the display device 1B may include an HOE. In this case, the optical function of the first semi-transmitting mirror 17 can be realized by a flat optical element, thereby reducing the thickness of the first semi-transmitting mirror 17 in the depth direction. As a result, the display device 1B can be made more compact in the depth direction. Furthermore, since the first semi-transmitting mirror 17 is a flat optical element, the distance between the first semi-transmitting mirror 17 and the display panel 2 can be reduced, or the first semi-transmitting mirror 17 and the display panel 2 can be brought into contact with each other, thereby further reducing the size of the display device 1B in the depth direction. The first semi-transmitting mirror 17 including an HOE may have polarization selectivity. For example, the first semi-transmitting mirror 17 including an HOE may have multiple thin metal wires formed on the surface facing the display panel 2 or the surface facing the first retarder 18, which achieves polarization selectivity by transmitting S-polarized light and reflecting P-polarized light. In this case, the reduction in brightness of the virtual image V viewed by the user 22 can be reduced.

[0148] The third semi-transmitting mirror 21 of the display device 1B may include an HOE. In this case, the optical function of the third semi-transmitting mirror 21 can be realized by a flat optical element, thereby reducing the thickness of the third semi-transmitting mirror 21 in the depth direction. As a result, the display device 1B can be made smaller in the depth direction. The third semi-transmitting mirror 21 including the HOE may have polarization selectivity. For example, the third semi-transmitting mirror 21 including the HOE may have a plurality of thin metal wires formed on the surface facing the second retardation plate 20 or on the surface opposite to the surface facing the second retardation plate 20, which realizes polarization selectivity by reflecting S-wave polarized light and transmitting P-wave polarized light. In this case, degradation in the quality of the virtual image V viewed by the user 22 can be reduced, and degradation in the brightness of the virtual image V can also be reduced.

[0149] The holographic optical element may have, for example, a pattern of interference fringes and be configured to diffract incident light in a predetermined direction.

[0150] In the display device 1A', the second semi-transmitting mirror 13' may include a Fresnel lens. In other words, the display device 1A' may have a Fresnel shape on the surface of the second semi-transmitting mirror 13'. In this case, as shown in FIG. 22, the optical function of the second semi-transmitting mirror 13' can be realized by a substantially flat optical element having a thickness (dimension in the depth direction) smaller than that of a convex half mirror, thereby reducing the thickness of the second semi-transmitting mirror 13' in the depth direction. As a result, the display device 1A' can be made more compact in the depth direction. Furthermore, since the second semi-transmitting mirror 13' is substantially flat, the distance between the second semi-transmitting mirror 13' and the second retardation plate 14 can be reduced, or the second semi-transmitting mirror 13' and the second retardation plate 14 can be brought into contact with each other, thereby further reducing the size of the display device 1A' in the depth direction. The second semi-transmitting mirror 13' including a Fresnel lens is also referred to as a Fresnel half mirror 13'.

[0151] As shown in FIG. 23 , the Fresnel half mirror 13′ may include a Fresnel lens (Fresnel convex lens) 33 having a planar first surface 33a facing the second retardation film 14 and a Fresnel-shaped second surface 33b facing the first retardation film 12, and a semi-transmissive 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 curved or flat. The semi-transmissive reflective layer 34 may be located on the inclined surface of the Fresnel shape. The semi-transmissive reflective layer 34 may transmit a portion (e.g., approximately 50%) of incident light and reflect the remaining portion (e.g., approximately 50%). The semi-transmissive reflective layer 34 may be a metal thin film. The metal thin film may be made of a metal material such as aluminum or chromium. The metal thin film may be formed by a vapor deposition method such as a CVD (Chemical Vapor Deposition) method or a PVD (Physical Vapor Deposition) method.

[0152] The Fresnel half mirror 13' has the optical function of a lens and the optical function of a half mirror. The optical function of the lens (e.g., focal length, etc.) is determined by the curvature and tilt angle of the inclined surface, the refractive index of the material constituting the Fresnel lens 33, etc. The optical function of the half mirror (e.g., focal length, transmittance, etc.) is determined by the curvature and tilt angle of the inclined surface, the transmittance of the semi-transmissive reflective layer 34, etc.

[0153] The Fresnel half mirror 13′ may have a surface facing the second retardation plate 14 flattened by a transparent material layer formed on the second surface 33b of the Fresnel lens 33. 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.

[0154] In the display device 1A', the first semi-transmitting mirror 11 may include a Fresnel lens. In this case, as shown in FIG. 22, the thickness of the first semi-transmitting mirror 11 can be reduced, resulting in a reduction in the size of the display device 1A' in the depth direction. Furthermore, since the first semi-transmitting mirror 11 including a Fresnel lens is substantially flat, the distance between the first semi-transmitting mirror 11 and the display panel 2 can be reduced, or the first semi-transmitting mirror 11 and the display panel 2 can be brought into contact with each other, thereby making it possible to further reduce the size of the display device 1A' in the depth direction. The first semi-transmitting mirror 11 including a Fresnel lens is also referred to as 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 include a Fresnel concave lens.

[0155] If the first semi-transparent mirror 11 were replaced with a Fresnel half mirror 11 that does not have polarization selectivity, the amount of light emitted from the display device 1A' would decrease, resulting in a decrease in the brightness of the virtual image V viewed by the user 22. Therefore, the Fresnel half mirror 11 may be configured to have polarization selectivity. For example, the Fresnel half mirror 11 may have a plurality of metal fine wires (metal nanowire grid) formed on the surface facing the display panel 2 or the surface facing the first retardation plate 12, which achieves polarization selectivity by transmitting S-wave polarized light and reflecting P-wave polarized light. This can reduce the decrease in brightness of the virtual image V viewed by the user 22.

[0156] As shown in FIG. 23 , the first semi-transmitting mirror 11 of the display device 1A may include a Fresnel lens. In this case, the thickness of the first semi-transmitting mirror 11 can be reduced, thereby enabling the display device 1A to be more compact in the depth direction. Furthermore, since the first semi-transmitting mirror 11 including the Fresnel lens is substantially flat, the distance between the first semi-transmitting mirror 11 and the display panel 2 can be reduced, or the first semi-transmitting mirror 11 and the display panel 2 can be brought into contact with each other, thereby enabling the display device 1A to be further compact in the depth direction. The first semi-transmitting mirror 11 including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transmitting mirror 11 including the Fresnel lens may have a plurality of thin metal wires formed on the surface facing the display panel 2 or the surface facing the first retardation film 12, which achieves polarization selectivity by transmitting S-wave polarized light and reflecting P-wave polarized light. In this case, the reduction in brightness of the virtual image V viewed by the user 22 can be reduced.

[0157] The semi-transmitting mirror 6 of the display device 1 may be configured to include a Fresnel lens. In this case, the thickness of the semi-transmitting mirror 6 can be reduced, and as a result, the display device 1 can be made smaller in size in the depth direction. Furthermore, since the semi-transmitting mirror 6 including the Fresnel lens is substantially flat, the distance between the semi-transmitting mirror 6 and the first retardation film 5 can be reduced, or the semi-transmitting mirror 6 and the first retardation film 5 can be brought into contact with each other, making it possible to further reduce the size of the display device 1 in the depth direction.

[0158] The first semi-transmitting mirror 17 of the display device 1B may include a Fresnel lens. In this case, the thickness of the first semi-transmitting mirror 17 can be reduced, thereby enabling the display device 1B to be more compact in the depth direction. Furthermore, since the first semi-transmitting mirror 17 including the Fresnel lens is substantially flat, the distance between the first semi-transmitting mirror 17 and the display panel 2 can be reduced, or the first semi-transmitting mirror 17 and the display panel 2 can be brought into contact with each other, thereby enabling the display device 1B to be more compact in the depth direction. The first semi-transmitting mirror 17 including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transmitting mirror 17 including the Fresnel lens may have a plurality of thin metal wires formed on the surface facing the display panel 2 or the surface facing the first retardation film 18, which achieves polarization selectivity by transmitting S-wave polarized light and reflecting P-wave polarized light. In this case, the reduction in brightness of the virtual image V viewed by the user 22 can be reduced.

[0159] The third semi-transmitting mirror 21 of the display device 1B may be configured to include a Fresnel lens. In this case, the thickness of the third semi-transmitting mirror 21 can be reduced, thereby enabling the display device 1B to be miniaturized in the depth direction. The third semi-transmitting mirror 21 including the Fresnel lens may be configured to have polarization selectivity. For example, the third semi-transmitting mirror 21 including the Fresnel lens may have a plurality of thin metal wires formed on the surface facing the second retardation plate 20 or on the surface opposite to the surface facing the second retardation plate 20, which realizes polarization selectivity by reflecting S-wave polarized light and transmitting P-wave polarized light. In this case, degradation in the quality of the virtual image V viewed by the user 22 can be reduced, and degradation in the brightness of the virtual image V can also be reduced.

[0160] 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 FIG. 10). The imaging device 100 is assumed to include an angle sensor fixed to the mobile object 23 that detects the orientation of the display devices 1, 1A, 1A', 1B relative to a predetermined direction. The predetermined direction may be, for example, the longitudinal direction of the mobile object 23, but is not limited to this. The angle sensor may be a three-axis angle sensor that can detect the orientations (roll, pitch, yaw) of the display devices 1, 1A, 1A', 1B. The mobile object 23 is assumed to include a DMS (Driver Monitoring System), and the imaging device 100 is assumed to be capable of communicating with and controlling the DMS. The DMS is assumed to be capable of capturing an image of the face of a user 22 seated in the driver's seat of the mobile object 23, performing facial authentication of the user 22, and determining whether the user 22 is a known user. A known user may mean a user whose information (also referred to as user information) such as features used for facial recognition, eye position while driving, and face direction is stored in at least one of the memory unit of the controller 43 and the memory unit of the DMS.

[0161] When the 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 FIG. 25), and the user 22 can view the virtual image V that changes in response to head movement, just as when using a normal rearview mirror. When 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 do not match (see FIG. 26), and the user 22 cannot view the virtual image V that changes in response to head movement, just as when using a normal rearview mirror, and this may cause the user 22 to feel uncomfortable.

[0162] 29, the control of the imaging device 100 by the controller 43 will be described. In the flowchart, "step" is abbreviated as "S," and within the chart, "positive" (computer flag = 1) in the judgment control is represented by [Yes], and "negative" (computer flag = 0) is represented by [No].

[0163] The flowchart of FIG. 29 starts, for example, when the user 22 sits in the driver's seat of the vehicle 23 and starts the engine of the vehicle 23.

[0164] In [S1], the DMS is controlled to confirm the user 22 seated in the driver's seat of the vehicle 23 (user confirmation).

[0165] In [S2], the DMS is controlled to perform facial authentication of the user 22 sitting in the driver's seat and determine whether the user 22 is a known user. If in [S2] the user 22 is a known user [Yes], the process proceeds to [S3]. If in [S2] the user 22 is not a known user [No], the process proceeds to [S7].

[0166] In [S3], user information of the user 22 (information such as eye position and face direction while driving) is acquired from the DMS.

[0167] 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 image on the display surface 2a of the display panel 2 in accordance with the orientation of the display devices 1, 1A, 1A', and 1B, the eye position of the user 22, the facial orientation, and the like. The change of the display area may involve making a portion of the display surface 2a a non-display area 2b in which no image is displayed, as shown in FIG. 27. As shown in FIG. 27, by changing the display area of ​​the image on the display surface 2a, the size of the left viewing area PL and the size of the right viewing area PR can be made approximately the same even when the user 22 is not positioned directly in front of the display devices 1, 1A, 1A', and 1B, thereby reducing the risk of the user 22 feeling uncomfortable.

[0168] Adjustment of the display devices 1, 1A, 1A', and 1B may include sliding (translating) at least one of the reflective polarizer 8, the semi-transparent mirror 6, and the 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 eye position of the user 22, the facial orientation, and the like. By sliding at least one of the reflective polarizer 8, the semi-transparent mirror 6, and the display panel 2, the size of the left viewing area PL and the size of the right viewing area PR can be made to approximately match, as shown in FIG. 28, thereby reducing the risk of the user 22 feeling uncomfortable. Furthermore, when sliding at least one of the reflective polarizer 8, the semi-transparent mirror 6, and the 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.

[0169] In [S5], the controller 43 receives an instruction from the user 22 as to 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 provided on a steering wheel. The imaging device 100 may be configured so that the user 22 can indicate that readjustment is necessary by swinging the imaging device 100 and changing the orientation of the imaging device 100. The change in the orientation of the imaging device 100 may be detected by a three-axis angle sensor of the imaging device 100. The controller 43 may determine that readjustment is not necessary if no instruction is received from the user 22 within a predetermined time after starting to accept instructions from the user 22. The predetermined time may be, for example, about 3 to 10 seconds, but is not limited to this.

[0170] If readjustment of the display devices 1, 1A, 1A', and 1B is necessary [Yes] in [S5], proceed to [S6]. If readjustment of the display devices 1, 1A, 1A', and 1B is not necessary [No] in [S5], end this flowchart. If readjustment of the display devices 1, 1A, 1A', and 1B is necessary [Yes] in [S5], proceed to [S7].

[0171] In [S6], the controller 43 controls the DMS to detect user information of the user 22 (information such as the eye position and face direction while driving), and acquires the user information of the user 22 from the DMS.

[0172] In [S7], the display devices 1, 1A, 1A', and 1B are adjusted based on the user information acquired 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].

[0173] In [S8], an instruction from the user 22 as to whether or not readjustment of the display devices 1, 1A, 1A', 1B is required is accepted. The acceptance of the instruction from the user 22 may be the same as in [S5]. In [S8], if readjustment of the display devices 1, 1A, 1A', 1B is required [Yes], the process returns to [S6]. In [S8], if readjustment of the display devices 1, 1A, 1A', 1B is not required [No], the process proceeds to [S9]. In [S8], if readjustment of the display devices 1, 1A, 1A', 1B is required [Yes], the process may return to [S7].

[0174] In [S9], the controller 43 stores the user information of the user 22 and information regarding adjustment of the display devices 1, 1A, 1A', 1B in at least one of the memory unit of the controller 43 and the memory unit of the DMS, and ends this flowchart.

[0175] According to the flowchart in Fig. 29, the viewing area in the digital rearview mirror can be efficiently controlled, reducing the possibility of the user 22 feeling uncomfortable. The flowchart in Fig. 29 can also be applied to the case where the imaging device 100 constitutes a digital side mirror.

[0176] Another example of the display devices 1, 1A, 1A', and 1B will be described. The same components as those of the display devices 1, 1A, 1A', and 1B will be given the same reference numerals, and detailed descriptions will be omitted. As shown in FIG. 33, the display device 1C of this example includes a display panel 2, an optical system 35, and a housing 36.

[0177] The display panel 2 has a display surface 2a and displays a display image on the display surface 2a. The optical system 35 projects display light emitted from the display panel 2 as a virtual image V into the field of view of the user 22. The optical system 35 may be the optical system 3 (see FIGS. 2, 3, and 30), the optical system 10 (see FIGS. 4, 5, and 31), or the optical system 16 (see FIGS. 9 and 32). FIGS. 33 to 36 show a case where the optical system 35 is the optical system 3 shown in FIG. 30.

[0178] The housing 36 accommodates the display panel 2 and the optical system 35. The housing 36 may hold the display panel 2 and the optical system 35. When the display device 1C includes an illuminator 4, the housing 36 may accommodate and hold the illuminator 4. The housing 36 has a window (opening) 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 through the window 37 of the housing 36. The display device 1C may also be arranged such that the window 37 and the optical system 35 overlap when viewed through the window 37 of the housing 36. The display device 1C may also be arranged such that the display panel 2 and the optical system 35 overlap when viewed through 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 made more compact. In the display device 1C, display light emitted from the display panel 2 propagates substantially uniaxially and is formed as a virtual image V. Therefore, distortion, brightness unevenness, etc. of the virtual image V visually recognized by the user 22 can be reduced, and the design of the optical system 35 becomes easier.

[0179] 33 and 34, the housing 36 may have a light-transmitting plate 38 disposed in the window 37. The light-transmitting plate 38 may transmit light emitted from the optical system 35. The light-transmitting plate 38 at least partially covers the window 37. The light-transmitting plate 38 may be made of, for example, glass, resin, or the like.

[0180] The optical system 35 (optical system 3) may include a third retardation plate 25 and a fourth retardation plate 26. The third retardation plate 25 may be located on the surface of the second retardation plate 7 facing the semi-transparent mirror 6. The fourth retardation plate 26 may be located on the surface of the third retardation plate 25 facing the semi-transparent mirror 6. 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 approach a crossed Nicol arrangement, even when the user 22 is not positioned directly in front of the display device 1C, thereby reducing degradation in display quality of the display device 1C. The third retardation plate 25 and the fourth retardation plate 26 may be, but are not limited to, half-wave plates. The third retardation plate 25 and the fourth retardation plate 26 may also be quarter-wave plates, eighth-wave plates, sixteenth-wave plates, or other wave plates that impart retardation. The third retardation plate 25 and the fourth retardation plate 26 may be wave plates that impart the same retardation or may be wave plates that impart different retardations. The optical axis of the third retardation plate 25 may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer 8.

[0181] The optical system 35 (optical system 3) may have a moth-eye structure film 39 located on the surface of the first retardation plate 5 facing the semi-transmitting mirror 6. The moth-eye structure film 39 can attenuate reflected light of light incident from the semi-transmitting mirror 6 side. This makes it possible to reduce unnecessary light, ambient light, and the like, which is reflected by the first retardation plate 5, is emitted from the display device 1C, and is then incident on the eyes of the user 22.

[0182] The optical system 35 (optical system 3) may have a moth-eye structure film 40 located on the surface of the fourth retardation plate 26 facing the semi-transmitting mirror 6. This makes it possible to reduce unnecessary light, ambient light, and the like, which are reflected by the fourth retardation plate 26, emitted from the display device 1C, and incident on the eyes of the user 22.

[0183] The reflective polarizer 8, the second retarder 7, the third retarder 25, the fourth retarder 26, the moth-eye structure film 40, and the light-transmitting plate 38 may be integrated together. This allows the display device 1C to be made thinner in the depth direction (Z-axis direction). Also, deformation of the reflective polarizer 8, the second retarder 7, the third retarder 25, the fourth retarder 26, the moth-eye structure film 40, and the light-transmitting plate 38 can be reduced.

[0184] 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 attached to the housing 36 as shown in FIGS. 35 and 36. The touch panel 41 may be attached to the housing 36 so as to cover the window 37 in which the light-transmitting plate 38 is arranged as shown in FIGS. 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.

[0185] A display system 200 according to the present disclosure will now be described. As shown in Fig. 39, the display system 200 includes display devices 1, 1A, 1A', 1B, and 1C, and a camera 201. The display panel 2 of the display devices 1, 1A, 1A', 1B, and 1C is capable of communicating with the camera 201, and displays an image captured by the camera 201. The display panel 2 and the camera 201 may be connected via, for example, a wired connection, a wireless connection, a CAN (Controller Area Network), or the like.

[0186] A moving body (vehicle) 23 of the present disclosure includes a display system 200. The display devices 1, 1A, 1A', 1B, and 1C are small display devices that do not occupy a large volume in the driver's cab of the vehicle 23 even when placed therein, and are unlikely to interfere with driving. Therefore, the user 22 can appropriately view the virtual image V or the real image. The display system 200 may be applied to a digital rearview mirror of the vehicle 23, or to digital side mirrors 1L and 1R (see FIG. 12). The display system 200 may also be applied to a cluster 29, a Center Information Display (CID) 30, a Passenger Information Display (PID) 31, a Rear Seat Entertainment (RSE) system 32, and the like (see FIGS. 10 and 12) in the dashboard of the vehicle 23.

[0187] According to the present disclosure, it is possible to reduce degradation of display quality in a small display device and improve light utilization efficiency. Furthermore, according to the present disclosure, it is possible to provide a small imaging device that allows a user to clearly view a virtual image.

[0188] FIG. 40 is a perspective view showing a cross section of yet another example of a display device according to an embodiment of the present disclosure.

[0189] The display device 501 may include a housing 36 having a viewing section with a window 37, a display panel 2 located within the housing 36 and having a display surface 2a, and an optical system 35 located within the housing 36 and focusing the display surface 2a to form a virtual image (image) V (see FIG. 1). The cross section of the display device 501 shown in FIG. 40 is a diagram cut in the vertical direction along the light emission direction of the display panel 2. In other words, it can be said to be a diagram cut in the vertical direction along the arrangement direction of the display panel 2 and the optical system 35.

[0190] Although the above describes an example in which the viewing portion has window 37, window 37 may also be the viewing portion. Furthermore, the viewing portion is not limited to window 37, and may have a translucent member other than window 37, or may be a space with no member present.

[0191] Fig. 41 is a plan view of an image formed by the display device shown in Fig. 40. When viewed from a distance from the viewing unit facing the viewing unit, the virtual image V may have a first region 401 that is visible from the viewing unit 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 longer than the length of the viewing unit. Furthermore, in the lateral direction of the virtual image V, the length of the virtual image V may be longer than the length of the viewing unit.

[0192] In this case, the second region 402 may be located on at least one of the left and right sides of the first region 401, or at least one of the upper and lower parts 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 parts of the first region 401. In other words, the second region 402 may be located on at least one of the left and right sides and the top and bottom parts 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 displayed on the display panel 2, the magnification ratio when this display image is formed into a virtual image V, the positional relationship between the virtual image V and the viewing portion, and the size of the viewing portion.

[0193] The size of the first region 401 and the second region 402 can be compared based on the area of ​​each region. For example, the first region 401 may occupy 60% or more of the virtual image V, and the second region 402 may occupy 40% or less of the virtual image V. The first region 401 may have an area twice or more that of the second region 402.

[0194] When viewing virtual image V at a distance from the viewing unit, it is sufficient to view it from a position where the background around the housing 36 is within the viewer's direct field of vision. In this case, it is sufficient to include the housing 36 and its surrounding background within a range of 70 degrees in the vertical and horizontal directions from the viewer's position. In this embodiment, for example, the viewer may view virtual image V from a distance of 30 cm or more from the viewing unit (window 37) while facing the window 37 directly.

[0195] FIG. 42 is a top view illustrating viewing the viewing unit from a frontal view. Viewing the viewing unit from a frontal view may mean that the user 22 views the viewing unit from a normal 404 relative to the center 403 of the virtual image V. That is, for example, when the light-transmitting plate 38, which is the window 37, is installed at an angle with respect to the housing 36, if the viewer views the viewing unit from a 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, and may view the virtual image V from a position non-parallel to the inclined surface of the light-transmitting plate 38. In the present disclosure, when the virtual image V is not viewed from a frontal view (when the virtual image V is viewed from a position deviated from the normal 404), the area of ​​the virtual image V that is not visible from the viewing unit may be larger than the area that is visible from the viewing unit, or the virtual image V may not have an area that is not visible from the viewing unit.

[0196] According to the above configuration, the user 22 who is facing the viewing unit from a distance can view most of the virtual image V, and therefore it is easy to recognize the content of the video that appears as the virtual image V.

[0197] Furthermore, the second regions 402 that should be located above and below the first region 401 may be smaller than the second regions 402 that should be located on the sides of the first region 401. In this case, the second regions 402 may be present on the sides of the first region 401, but may not be present above or below the first region 401. In this embodiment, the second regions 402 are located above, below, and on the sides of the first region 401, and first portions 406 of the second region 402 that are located above and below the first region 401 are set smaller than second portions 407 of the second region 402 that are located on the sides of the first region 401.

[0198] The second region 402 may be visible from the viewing unit when viewed from a distance without facing the viewing unit. A first portion 406 of the second region 402 may be visible from the window 37 when the window 37 is viewed from above or below, and a second portion 407 of the second region 402 may be visible from the window 37 when the window 37 is viewed from the side. In this case, it is possible to make it easier for the user 22 to view the virtual image V.

[0199] Furthermore, the magnification of the virtual image V in the vertical direction may be smaller than the magnification of the virtual image V in the horizontal direction. For example, the magnification of the virtual image V in the horizontal direction may be two or more times the magnification of the virtual image V in the vertical direction. According to the above configuration, a virtual image V with a large width can be formed, making it easier for the user 22 to view the virtual image V.

[0200] FIG. 43 is a diagram comparing the length of the viewing section and the length of the semi-transmitting mirror in the longitudinal direction of the viewing section. The optical system 35 is positioned within the housing 36 so as to overlap with the display panel 2 when the interior of the housing 36 is viewed through the window 37. The optical system 35 also includes a semi-transmitting mirror 6, and the length L37 of the viewing section (window 37) in the longitudinal direction WL of the viewing section (window 37) may be greater than the length L6 of the semi-transmitting mirror 6. When the viewing section (window 37) is parallel to the XY plane, the longitudinal direction WL of the viewing section (window 37) may be, for example, the X direction or the Y direction. When the viewing section (window 37) is not parallel to the XY plane, the longitudinal direction WL of the viewing section (window 37) is, for example, along the X direction or the Y direction, and the length L37 of the viewing section (window 37) is the X component or the Y component. This configuration allows the viewable area of ​​the virtual image V to be increased.

[0201] Also, as shown in Figure 42, the angle θa formed by a first straight line 410 connecting a first end 408 in the longitudinal direction of the virtual image V and the center 409 of the window 37 and a second straight line 412 connecting a 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.

[0202] An example of the angle θa is shown in Fig. 42. Fig. 42 shows an example in which 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, and may be a direction parallel to the XY plane, such as the Y direction.

[0203] Since the effective visual field 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 appears as the virtual image V.

[0204] The virtual image V may have a size such that when viewed by the user 22 at a position farther away than the focal position of the optical system 35, more than half of the image is visible from the viewing area. This makes it easier for the user 22 to recognize the content of the image that appears as the virtual image V. When the optical system 51 collects or converges light using the semi-transparent mirror 6, the focal position of the optical system 35 is synonymous with the focal position of the semi-transparent mirror 6. When the optical system 51 collects or converges light using multiple optical members, the focal position of the optical system 35 is a position based on the combined focal length of the multiple optical members.

[0205] The optical system 35 includes a semi-transparent mirror 6 having a reflecting surface 6a, and the optical path length from the light emitted from the display panel 2 to the reflecting surface 6a of the semi-transparent mirror 6 from the viewing area side may be two-thirds or less of the focal length Lf6 of the semi-transparent mirror 6 (see FIG. 40). In this case, for example, referring to FIG. 2, the optical path length from the display panel 2 to the reflecting surface 6a of the semi-transparent mirror 6 may be the sum of the optical path lengths of the display light of the first linearly polarized 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. FIG. 40 shows the focal point f6 of the semi-transparent mirror 6. This configuration can suppress the magnification of the virtual image V, thereby reducing the degradation of the resolution of the virtual image V for the user 22.

[0206] 44 and 45 are diagrams illustrating two lines connecting a pair of end points of an image and a pair of end points of a semi-transparent mirror in a cross-sectional view. A pair of end points refers to, for example, two end points that are located on opposing sides or corners and aligned in the left-right or up-down direction among the points constituting the outer edge of a component or member such as an image or semi-transparent mirror. The cross sections in FIGS. 44 and 45 are cross sections cut in the left-right or up-down direction. Examples of such cross sections include the ZX cross section shown in FIG. 44 and the YZ cross section shown in FIG. 45. The cross section corresponding to such a cross section may be a plane parallel to the Z-axis direction.

[0207] In this embodiment, the optical system 35 has a semi-transparent mirror 6, and in a cross-sectional view, the angle θb formed by two straight lines 417 and 418 connecting the pair of end points 413 and 414 of the virtual image V and the pair of end points 415 and 416 of the semi-transparent mirror 6 may be an acute angle. Furthermore, the angle θb formed by the two straight lines 417 and 418 connecting the pair of end points 413 and 414 of the virtual image V and the pair of end points 415 and 416 of the semi-transparent mirror 6 may be equal to or less than the effective viewing angle (70 degrees).

[0208] Furthermore, when the magnitude of the angle formed by the two straight lines connecting each of a pair of end points aligned in the left-right direction of the virtual image V and each of a pair of end points aligned in the left-right direction of the semi-transparent mirror 6 is defined as a first angle, and the magnitude of the angle formed by the two straight lines connecting each of a pair of end points aligned in the up-down direction of the virtual image V and each of a pair of end points aligned in the up-down direction of the semi-transparent mirror 6 is defined as a second angle, the first angle may be larger than the second angle.

[0209] In addition, the optical system 35 has a semi-transparent mirror 6, and in a cross-sectional view, the intersection 419 of two straight lines 417 and 418 connecting the end points 413 and 414 of the virtual image V and the end points 415 and 416 of the semi-transparent mirror 6, respectively, may be located outside the display device 501 relative to the window 37.

[0210] Furthermore, when the intersection of two straight lines connecting each of a pair of end points aligned in the left-right direction of the virtual image V and each of a pair of end points aligned in the left-right direction of the semi-transparent mirror 6 is defined as a first intersection, and the intersection of two straight lines connecting each of a pair of end points aligned in the up-down direction of the virtual image V and each of a pair of end points aligned in the up-down direction of the semi-transparent mirror 6 is defined as a second intersection, the first intersection may be located closer to the display device 501 than the second intersection.

[0211] Furthermore, two straight lines connecting a pair of both end points aligned in the left-right direction of the virtual image V and a pair of both end points aligned in the left-right direction of the semi-transparent mirror 6 may pass through the viewing area, as shown in Figures 44 and 45. Furthermore, two straight lines connecting a pair of both end points aligned in the up-down direction of the virtual image V and a pair of both end points aligned in the up-down direction of the semi-transparent mirrors 6 and 11 may pass through the viewing area, as shown in Figures 44 and 45.

[0212] The optical system 35 has a semi-transmitting mirror 6 located within the housing 36 so as to overlap with the display panel 2 when the interior of the housing 36 is viewed from the viewing section (window 37). The semi-transmitting mirror 6 may have a planar shape similar to that of the display image displayed on the display panel 2. That is, when the semi-transmitting mirror 6 is viewed from above in the direction of the viewing section (window 37), the semi-transmitting mirror 6 may have a planar shape similar to that of the display image. Specifically, in this embodiment, the display panel 2 displays a rectangular display image, and therefore the semi-transmitting 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 from the virtual image V.

[0213] As shown in FIG. 40 , the display device 501 may further include a shielding wall 421 that shields at least a portion of an end 420 of the semi-transparent mirror 6. In other words, the display device 501 may include a shielding wall 421 that is arranged to hide the edge of the semi-transparent mirror 6 when the user 22 views the virtual image V from the viewing unit. The shielding wall 421 may be provided on the inner surface of the housing 36. In this embodiment, the shielding wall 421 may be arranged to shield the upper end of the semi-transparent mirror 6. The shielding wall 421 may be arranged to shield the lower end of the semi-transparent mirror 6. The shielding wall 421 may be arranged to shield the right end of the semi-transparent mirror 6. The shielding wall 421 may be arranged to shield the left end of the semi-transparent mirror 6.

[0214] Furthermore, the display device 501 may have a shielding portion located at the end 420 of the semi-transmitting mirror 6, 11. Specifically, as shown in FIG. 46 , the light absorptance of the end 420 of the semi-transmitting mirror 6 may be set higher than the light absorptance of the portions other than the end 420 of the semi-transmitting mirror 6. For example, the end 420 may be painted black, covered with a member such as a light-blocking film, or made of a material with high light-blocking properties. Each of these methods can reduce the risk of light scattering near the end 420, thereby reducing the risk of unintended glitter or the like appearing on the virtual image V due to this light scattering.

[0215] The size of the virtual image V may be larger than the outer shape of the viewing surface 422 where the window 37 of the housing 36 is located. Also, 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. In each of these cases, the magnification of the virtual image V is sufficiently suppressed, allowing the user 22 to view the virtual image V with a sufficiently high resolution.

[0216] 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 that includes the viewing surface 422 among the surfaces that make up the housing 36. Furthermore, 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 that is located outside the housing 36 with respect to the surface that includes the viewing surface 422 among the surfaces that make up the housing 36. Furthermore, for example, the virtual image V may have a third region that is 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, or on the upper or lower part of the virtual image V, or on the side, upper, and lower part of the virtual image V. In this case, the viewing area can be maximized with respect to the housing 36 of the display device 501.

[0217] The window 37 is elongated in the vertical or horizontal direction, the display panel 2 displays an image, and the optical system 35 focuses the image to form a virtual image V, which may be elongated along the longitudinal direction of the window 37. In other words, the viewing portion has an elongated shape that is elongated along the longitudinal direction of the display image on the display panel 2. Furthermore, the semi-transmitting mirrors 6 and 11 have an elongated shape that is elongated along the longitudinal direction of the display image on the display panel 2. Furthermore, the semi-transmitting mirrors 6 and 11 have an elongated shape that is elongated along the longitudinal direction of the viewing portion.

[0218] In the above description with reference to FIGS. 40 to 46, the display device 501 in which the optical system 35 is the optical system 3 (see FIGS. 2, 3, and 30) has been described as an example. However, the optical system 35 of the display device 501 is not limited to the optical system 3 and may be the optical system 10 (see FIGS. 4, 5, and 31) described in other embodiments or the optical system 16 (see FIGS. 9 and 32). In this case, each member of the optical system 10 or each member of the optical system 16 may appropriately correspond to each member of the optical system 35. For example, when 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. Furthermore, when 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.

[0219] From the above, the display device 501 may be interpreted as being in either of the following (first configuration) and (second configuration).

[0220] (First Configuration) A display device 501 including a display panel 2 having a display surface 2a and an optical system 35 that focuses the display surface 2a to form a virtual image V, wherein the optical system 35 includes a reflective polarizer 8, a first retardation plate 5 positioned between the display panel 2 and the reflective polarizer 8, a second retardation plate 7 positioned between the first retardation plate 5 and the reflective polarizer 8, and a semi-transmitting mirror 6 having a reflective surface 6a and positioned between the first retardation plate 5 and the second retardation plate 7, wherein the optical path length of light emitted from the display panel 2 from the second retardation plate 7 of the semi-transmitting mirror 6 to incident on the reflective surface 6a is two-thirds or less of the focal length Lf6 of the semi-transmitting mirror 6 (see FIG. 40). The first configuration corresponds to an example in which the optical system 35 is an optical system 3, an example of which may be shown in FIG. 40. The semi-transmitting 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 that the image on the display surface 2a will be missing from the virtual image V.

[0221] (Second Configuration) A display device 501 including a display panel 2 having a display surface 2a and an optical system 35 that images the display surface 2a to form a virtual image V, wherein the optical system 35 includes a first retardation plate 12 and a second retardation plate 14, a first semi-transparent mirror 11 located between the display panel 2 and the first retardation plate 12 and having a reflecting surface (first reflecting surface) 11a, and a second semi-transparent mirror 13 located between the first retardation plate 12 and the second retardation plate 14 and having a reflecting surface (second reflecting surface) 13a, wherein the optical path length from the display panel 2 to the reflecting 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 in which the optical system 35 is optical system 10, and an example thereof may be one in which the optical system 3 of the display device 501 shown in FIG. 40 is replaced with the optical system 10 (see FIG. 4). 4, the optical path length from the display panel 2 to the reflecting surface 11a of the first semi-transparent mirror 11 may be the sum of the optical path lengths of the display light of the first linearly polarized 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 from the virtual image V.

[0222] Fig. 47 is a block diagram showing another example of a display device according to an embodiment of the present disclosure. Fig. 48 is a plan view of an image formed by the display device shown in Fig. 47. Here, Figs. 40 to 46 will be referred to in addition to Figs. 47 and 48.

[0223] Display device 501 may include a housing 36 having a window 37, a display panel 2 located within housing 36 and displaying an image showing supplemental information, an optical system 35 located within housing 36 and focusing the image to form a virtual image V, and a control unit 423 controlling the image on display panel 2. When viewed from a distance away from window 37 and facing window 37, virtual image V may have a first region 401 that is visible through window 37 and a second region 402 that is not visible through window 37. Control unit 423 may control the image so that a large amount of supplemental information is displayed in first region 401.

[0224] The control unit 423 may be the controller 43 (see FIG. 1). To control the image, the control unit 423 may, but is not limited to, control the display panel 2, and may also control various components such as the optical system 35 and the illuminator 4 (see FIG. 1). The control unit 423 can display the supplemental information in the first area 401 by displaying the supplemental information in a desired area. The size of the first area 401 may be estimated based on the magnification ratio of the image and the size of the viewing area.

[0225] For example, when the display device 501 is mounted on the mobile object 23, the virtual image V is an image formed by imaging an image captured by the camera 201 (see FIG. 39 ). In this case, the supplemental information may be information other than the image captured by the camera 201, such as various types of information related to the user 22 or the mobile object 23. The supplemental information may also be information for supplementing the user 22's operation of the mobile object 23. More specifically, the supplemental information may be information such as instructions or warnings for the user 22. That is, the supplemental information may be an arrow indicating the direction in which the mobile object 23 should move or a warning mark indicating the presence of a pedestrian. This makes it possible to realize the display device 501 in which the supplemental information can be viewed when viewed from a distance from the window 37 and facing the window 37 directly. The supplemental information may be displayed not only in the first region 401 but also in the second region 402. In this case, the first region 401 may be controlled so that more supplemental information can be displayed. The density of supplemental information may be greater in the first region 401 than in the second region 402.

[0226] A moving body (vehicle) 23 equipped with the display device 501 is also included in the scope of the present disclosure (see FIG. 39). As a result, a moving body 23 that achieves the same effects as the display device 501 can be realized.

[0227] 49 and 50 are cross-sectional views showing examples of the configuration of a display device according to an embodiment of the present disclosure. In each of Fig. 49 and Fig. 50, illustrations of members that are not relevant to the description may be omitted. Also, descriptions of configurations or parts equivalent to those in the above example may be omitted.

[0228] The display device 501 includes a display panel 2 and an optical system 3. The optical system 3 may include a first retardation plate 5, a semi-transparent mirror 6, a second retardation plate 7, and a reflective polarizer 8. Alternatively, the optical system 3 may include the first retardation plate 5, the semi-transparent mirror 6, the second retardation plate 7, and the reflective polarizer 8 arranged in this order from the display panel 2 side.

[0229] The function of the optical system 3 in each of Figures 49 and 50 is the same as that of the optical system 3 in Figure 2, from the time when the display light of the first linearly polarized light L1 passes through the first retardation plate 5 to the time when the light of the fourth linearly polarized light L4 passes through the reflective polarizer 8 and is emitted to the outside.

[0230] In this embodiment, the reflective polarizer 8 can collect or converge light that is incident on and reflected from the reflective polarizer 8. Specifically, the reflective polarizer 8 has a concave shape located on the display panel 2 side. As a result, the reflective polarizer 8 can collect or converge light. The reflective polarizer 8 can also be said to have a concave shape that opens toward the display panel 2 side. The reflective polarizer 8 can also be said to have a concave shape that is recessed toward the side opposite the display panel 2. The reflective polarizer 8 can also be said to have a convex shape that protrudes toward the side opposite the display panel 2 (the user 22 side). As shown in FIG. 49, the reflective polarizer 8 may be disposed on the inner surface of a substrate 424 that has a concave shape toward the display panel 2 side.

[0231] In this embodiment, the semi-transmitting mirror 6 can collect or converge light that is incident on and reflected from the semi-transmitting mirror 6. Specifically, the semi-transmitting mirror 6 has a concave shape located on the opposite side from the display panel 2 (the user 22 side). As a result, the semi-transmitting mirror 6 can collect or converge light. It can also be said that the semi-transmitting mirror 6 has a concave shape that opens toward the user 22. It can also be said that the semi-transmitting mirror 6 has a concave shape that is recessed toward the display panel side. It can also be said that the semi-transmitting mirror 6 has a convex shape that protrudes toward the display panel 2 side.

[0232] 50, at least one of the reflective polarizer 8 and the semi-transparent mirror 6 may be flat. In this case, at least one of the reflective polarizer 8 and the semi-transparent mirror 6 may be a holographic optical element, or the surface shape of at least one of the reflective polarizer 8 and the semi-transparent mirror 6 may have a Fresnel shape. In this case, the reflective polarizer 8 may be disposed on the surface of a flat substrate 424. One example of the material for the substrate 424 is glass.

[0233] Each component of the optical system 3 in each of Figures 49 and 50 may correspond to each component of the optical system 3 in Figure 2. Each component of the optical system 10 in each of Figures 51 and 52 may correspond to each component of the optical system 10 in Figure 4, including the corresponding relationship between the reflective polarizer 425 and the first semi-transparent mirror 11.

[0234] 51 and 52 are cross-sectional views showing examples of the configuration of a display device according to an embodiment of the present disclosure. In each of Fig. 51 and Fig. 52, illustrations of members that are not relevant to the description may be omitted. Furthermore, descriptions of configurations or parts equivalent to those in the above example may be omitted.

[0235] The display device 501 includes a display panel 2 and an optical system 10. The optical system 10 may include a reflective polarizer 425, a first retardation plate 12, a second semi-transparent mirror 13, a second retardation plate 14, and a polarizer 15. Alternatively, the optical system 10 may include the reflective polarizer 425, the first retardation plate 12, the second semi-transparent mirror 13, the second retardation plate 14, and the polarizer 15 arranged in this order from the display panel 2 side. The reflective polarizer 425 may have substantially the same function as the first semi-transparent mirror 11 (see FIG. 4).

[0236] The function of the optical system 10 in each of Figures 51 and 52 is the same as that of the optical system 10 in Figure 4, from the time when the display light of the first linearly polarized light L1 passes through the reflective polarizer 425, which has substantially the same function as the first semi-transparent mirror 11, until the light of the fourth linearly polarized light L4 passes through the polarizer 15 and is emitted to the outside, and the light of the fifth linearly polarized light L5 is absorbed by the polarizer 15.

[0237] In this embodiment, the reflective polarizer 425 can condense or converge light that is incident on and reflected by the reflective polarizer 425. Specifically, the reflective polarizer 425 has a concave shape located on the opposite side (user 22 side) from the display panel 2. As a result, the reflective polarizer 425 can condense or converge light. It can also be said that the reflective polarizer 425 has a concave shape that opens toward the user 22. It can also be said that the reflective polarizer 425 has a concave shape that is recessed toward the display panel 2. It can also be said that the reflective polarizer 425 has a convex shape that protrudes toward the display panel 2. As shown in FIG. 51 , the reflective polarizer 425 may be disposed on the inner surface of a base material 426 that has a concave shape toward the user 22.

[0238] In this embodiment, second semi-transmitting mirror 13 can collect or converge light that is incident on and reflected from second semi-transmitting mirror 13. Specifically, second semi-transmitting mirror 13 has a concave shape located on the display panel 2 side. As a result, second semi-transmitting mirror 13 can collect or converge light. Second semi-transmitting mirror 13 can also be said to have a concave shape that opens on the display panel 2 side. Second semi-transmitting mirror 13 can also be said to have a concave shape that is recessed toward the side opposite to display panel 2 (user 22 side). Second semi-transmitting mirror 13 can also be said to have a convex shape that protrudes toward user 22.

[0239] 52, at least one of the reflective polarizer 425 and the second semi-transparent mirror 13 may be flat. In this case, at least one of the reflective polarizer 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 polarizer 425 and the second semi-transparent mirror 13 may have a Fresnel shape. In this case, the reflective polarizer 425 may be disposed on the surface of a flat substrate 426. One example of the material for the substrate 426 is glass.

[0240] The display panel 2 and optical system 3 (see FIGS. 49 and 50, respectively) and the display panel 2 and optical system 10 (see FIGS. 51 and 52, respectively) may be interpreted as including a display system 427, a concave mirror unit 428, and a concave mirror unit 429. The concave mirror units 428 and 429 may transmit a portion of incident light and reflect the remainder. The concave mirror units 428 and 429 are not limited to being concave mirrors themselves, and may optically function as concave mirrors regardless of their shape.

[0241] Figures 53A and 53B are diagrams illustrating the optical functions of the display devices according to each of Figures 49 to 52. As shown in Figure 53A, concave mirror unit 429 focuses an image of display surface 2a of display system 427 to form a virtual image V429 that is enlarged relative to display surface 2a. As shown in Figure 53B, concave mirror unit 428 focuses virtual image V429 to form a virtual image V428 that is enlarged relative to virtual image V429. This makes it easier to adjust the magnification of virtual image V relative to display surface 2a.

[0242] According to the display device 501 shown in each of Figures 49 to 52, the focal length of each concave mirror portion 428 and 429 can be made longer, which is convenient when narrowing the gap between components. Furthermore, the aspect ratio of the Fresnel shape can be set small, facilitating molding and vapor deposition. Regarding 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 partially.

[0243] FIG. 54 shows an example of various dimensions of the display device shown in FIG. 34. The various dimensions in FIG. 54 may all be dimensions in the optical axis direction of light incident on the optical system 3 or 10. The inequality sign "<" in FIG. 54 means that the dimension may be less than the indicated dimension. The spatial dimension (reference numeral 6-40) may be the distance from the portion of the semi-transparent mirror 6 on the exit side closest to the display panel 2 to the moth-eye structure film 40. The display panel-reflective polarizer distance (including components 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 warping (reference numeral 6-6) may be the dimension from the portion of the semi-transparent mirror 6 on the entrance side closest to the display panel 2 to the portion of the semi-transparent mirror 6 on the exit side closest to the second retardation film 7.

[0244] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments.

[0245] For example, although the above describes a display device including a display panel, the present disclosure is not limited to this. For example, the present disclosure may be implemented as a display panel accommodating device in which a housing has an opening and a display panel can be inserted. In this case, the display panel accommodating device may have the same configuration as the display device, except that the housing has an opening and a display panel can be inserted from the outside.

[0246] Furthermore, the present disclosure is not limited to the above-described embodiments. Various modifications and improvements are possible within the scope of the gist of the present disclosure. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention of the present disclosure. For example, functions contained in each component can be rearranged so as not to cause logical contradictions, and multiple components can be combined into one or divided. In other words, it should be noted that a person skilled in the art would easily be able to make various modifications or alterations based on the present disclosure. It should also be noted that these modifications, alterations, and alterations are included within the scope of the present disclosure.

[0247] The display device of the present disclosure can be implemented in the following aspects (1) to (71).

[0248] (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-transparent mirror disposed between the first retardation plate and the second retardation plate and having a reflecting surface facing the second retardation plate, The display device, wherein the first retardation plate and the second retardation plate are quarter-wave plates.

[0249] (1') a display panel that emits 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 disposed opposite the second retardation plate and transmitting the first polarized light and reflecting the second polarized light; a semi-transparent mirror disposed between the first retardation plate and the second retardation plate and having a reflecting surface facing the second retardation plate, The first retardation plate and the second retardation plate polarize the display light into the first polarization and the second polarization.

[0250] (2) The display device according to (1), wherein air is interposed between the first retardation plate and the second retardation plate.

[0251] (3) The display device according to (1) or (2) above, further comprising a third retardation plate disposed between the display panel and the reflective polarizer.

[0252] (4) The display device according to (3), further comprising a fourth retardation plate disposed between the display panel and the reflective polarizer.

[0253] (5) The display device according to (4), wherein one of the third retardation plate and the fourth retardation plate is a quarter-wave plate and the other is a half-wave plate.

[0254] (6) The display device according to (4), wherein the third retardation plate and the fourth retardation plate are half-wave plates.

[0255] (7) The display device according to any one of (1) to (6) above, wherein the reflecting surface of the semi-transparent mirror is concave.

[0256] (8) The display device according to any one of (1) to (6) above, wherein the semi-transparent mirror is a flat optical element made of a holographic optical element.

[0257] (9) The display device according to any one of (1) to (6) above, wherein the semi-transparent mirror includes a Fresnel lens.

[0258] (10) The display device according to (8) or (9), wherein the semi-transparent mirror is integrated with at least one of the first retardation plate and the second retardation plate.

[0259] (11) 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 first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate and having a second reflecting surface facing the first retardation plate; a polarizing plate facing the second retardation plate, The display device, wherein the first retardation plate and the second retardation plate are quarter-wave plates.

[0260] (11') a display panel that emits display light; a first retardation plate facing the display panel; a second retardation plate disposed apart from the first retardation plate; a first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate and having a second reflecting surface facing the first retardation plate; a polarizing plate facing the second retardation plate, The display device, wherein the first retardation plate and the second retardation plate convert the display light into a first polarized light that is transmitted through the polarizing plate and a second polarized light that is transmitted less through the polarizing plate than the first polarized light.

[0261] (12) The display device according to (11), wherein the second reflecting surface is a convex surface that protrudes toward the first retardation plate.

[0262] (13) The display device according to (11) or (12) above, wherein air is interposed between the first semi-transparent mirror and the first retardation plate.

[0263] (14) The display device according to any one of (11) to (13) above, further comprising a third retardation plate disposed between the display panel and the polarizing plate.

[0264] (15) The display device according to (14), further comprising a fourth retardation plate disposed between the display panel and the polarizing plate.

[0265] (16) The display device according to (15), wherein one of the third retardation plate and the fourth retardation plate is a quarter-wave plate and the other is a half-wave plate.

[0266] (17) The display device according to (15), wherein the third retardation plate and the fourth retardation plate are half-wave plates.

[0267] (18) The display device according to any one of (11) to (17) above, wherein the first reflecting surface is concave.

[0268] (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 made of holographic optical elements.

[0269] (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.

[0270] (21) The display device according to (19) or (20), wherein the first semi-transparent mirror is integrated with at least one of the display panel and the first retardation plate.

[0271] (22) The display device according to (19) or (20), wherein the second semi-transparent mirror is integrated with at least one of the first retardation plate and the second retardation plate.

[0272] (23) 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 first semi-transparent mirror disposed between the display panel and the first retardation film and having a first reflecting surface facing the first retardation film; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate, the second semi-transparent mirror having a second reflecting surface facing the first retardation plate and a third reflecting surface facing the second retardation plate; a third semi-transparent mirror having a fourth reflecting surface facing the second retardation plate, The display device, wherein the first retardation plate and the second retardation plate are quarter-wave plates.

[0273] (23') a display panel that emits display light; a first retardation plate that transmits the display light; a second retardation plate disposed apart from the first retardation plate; a first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate, the second semi-transparent mirror having a second reflecting surface facing the first retardation plate and a third reflecting surface facing the second retardation plate; a third semi-transparent mirror having a fourth reflecting surface facing the second retardation plate.

[0274] (24) The display device according to (23), wherein air is interposed between the first semi-transparent mirror and the first retardation plate, and between the third semi-transparent mirror and the second retardation plate.

[0275] (25) The display device according to (23) or (24), wherein the first reflecting surface and the fourth reflecting surface are concave.

[0276] (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 made of holographic optical elements.

[0277] (27) The display device according to (23) or (24) above, wherein the first semi-transparent mirror and the third semi-transparent mirror include Fresnel lenses.

[0278] (28) The display device according to (26) or (27), wherein the first semi-transparent mirror is integrated with at least one of the display panel and the first retardation plate.

[0279] (29) The display device according to any one of (26) to (28) above, wherein the second semi-transparent mirror is integrated with the second retardation plate.

[0280] (30) The display light includes a display light for a left eye image and a display light for a 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 of the light rays of the display light for the left eye image and the display light for the right eye image.

[0281] (31) An imaging device including the display device according to any one of (1) to (30) above.

[0282] (32) An imaging device as described in (31) above, wherein the virtual image projected within the user's field of view includes a binocular visible area that is visible to both the user's left and right eyes, a left eye visible area that is visible only to the left eye, and a right eye visible area that is visible only to the right eye.

[0283] (33) a display panel; an optical system that projects display light emitted from the display panel as a virtual image or a real image; a housing that houses the display panel and the optical system, the housing has a window that transmits light emitted from the optical system, The display device is arranged so that the window, the optical system, and the display panel overlap when the window of the housing is viewed.

[0284] (34) The display device according to (33), wherein the housing has a light-transmitting plate disposed in the window.

[0285] (35) The display device according to (34) above, further comprising a touch panel attached to the housing so as to cover the light-transmitting plate.

[0286] (36) The display device according to any one of (1) to (30) and (33) to (35), wherein the display panel has a display surface and is provided with an illuminator that irradiates light onto a surface of the display panel opposite to the display surface.

[0287] (37) The display device according to (36) above, further comprising a controller having a function of controlling at least one of the image displayed on the display panel and the illuminator.

[0288] (38) A vehicle equipped with the display device described in (37) above.

[0289] (39) 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-transparent mirror disposed between the first retardation plate and the second retardation plate and having a reflecting surface facing the second retardation plate, the first retardation plate and the second retardation plate are quarter-wave plates, a light path length of light emitted from the display panel, transmitted through the semi-transmitting mirror, reflected by the reflective polarizing plate, and reaching the semi-transmitting mirror is shorter than a focal length of the semi-transmitting mirror;

[0290] (40) 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-transparent mirror disposed between the first retardation plate and the second retardation plate and having a reflecting surface facing the second retardation plate, the first retardation plate and the second retardation plate are quarter-wave plates, a light path length of light emitted from the display panel, transmitted through the semi-transmitting mirror, reflected by the reflective polarizing plate, and reaching the semi-transmitting mirror is longer than a focal length of the semi-transmitting mirror;

[0291] (41) A display panel that emits linearly polarized display light; a first retardation plate that transmits the display light; a second retardation plate disposed apart from the first retardation plate; a first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate and having a second reflecting surface facing the first retardation plate; a polarizing plate facing the second retardation plate, the first retardation plate and the second retardation plate are quarter-wave plates, a display device in which the optical path length of light emitted from the display panel, transmitted through the first semi-transparent mirror, reflected by the second semi-transparent mirror, and reaching the first semi-transparent mirror is shorter than the focal length of the first semi-transparent mirror.

[0292] (42) A display panel that emits linearly polarized display light; a first retardation plate that transmits the display light; a second retardation plate disposed apart from the first retardation plate; a first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate and having a second reflecting surface facing the first retardation plate; a polarizing plate facing the second retardation plate, the first retardation plate and the second retardation plate are quarter-wave plates, a display device in which the optical path length of light emitted from the display panel, transmitted through the first semi-transparent mirror, reflected by the second semi-transparent mirror, and reaching the first semi-transparent mirror is longer than the focal length of the first semi-transparent mirror.

[0293] (43) A display panel that emits linearly polarized display light; a first retardation plate that transmits the display light; a second retardation plate disposed apart from the first retardation plate; a first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate, the second semi-transparent mirror having a second reflecting surface facing the first retardation plate and a third reflecting surface facing the second retardation plate; a third semi-transparent mirror having a fourth reflecting surface facing the second retardation plate, the first retardation plate and the second retardation plate are quarter-wave plates, a display device in which the optical path length of light that is emitted from the display panel, passes through the first semi-transparent mirror, is reflected by the second semi-transparent mirror, and reaches the first semi-transparent mirror is shorter than the focal length of the first semi-transparent mirror, and the optical path length of light that is emitted from the display panel, passes through the first semi-transparent mirror, is reflected by the second semi-transparent mirror, and reaches the third semi-transparent mirror is shorter than the focal length of the first semi-transparent mirror.

[0294] (44) A display panel that emits linearly polarized display light; a first retardation plate that transmits the display light; a second retardation plate disposed apart from the first retardation plate; a first semi-transparent mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate; a second semi-transparent mirror disposed between the first retardation plate and the second retardation plate, the second semi-transparent mirror having a second reflecting surface facing the first retardation plate and a third reflecting surface facing the second retardation plate; a third semi-transparent mirror having a fourth reflecting surface facing the second retardation plate, the first retardation plate and the second retardation plate are quarter-wave plates, a display device in which the optical path length of light that is emitted from the display panel, passes through the first semi-transparent mirror, is reflected by the second semi-transparent mirror, and reaches the first semi-transparent mirror is longer than the focal length of the first semi-transparent mirror, and the optical path length of light that is emitted from the display panel, passes through the first semi-transparent mirror, is reflected by the second semi-transparent mirror, and reaches the third semi-transparent mirror is longer than the focal length of the first semi-transparent mirror.

[0295] (45) A display panel that emits display light; a convex lens through which the display light passes, The display device, wherein the optical path length from the display panel to the convex lens is shorter than the focal length of the convex lens.

[0296] (46) A display panel that emits display light; a convex lens through which the display light passes, The display device, wherein the optical path length from the display panel to the convex lens is longer than the focal length of the convex lens.

[0297] (47) A display device according to any one of (1) to (30), (33) to (37), and (39) to (46) above; a camera; The display panel is capable of communicating with the camera and displays images captured by the camera.

[0298] (48) A vehicle equipped with the display system described in (47) above.

[0299] (49) A housing having a visible portion; a display panel located within the housing and having a display surface; an optical system located within the housing and focusing the image on the display surface to form an image; Equipped with A display device in which the image has, when viewed from a distance from the viewing unit and facing the viewing unit directly, a first area that is visible from the viewing unit and a second area that is not visible from the viewing unit and is smaller than the first area.

[0300] (50) The second region is located above, below, and to the sides of the first region; The display device described in (49) above, wherein the portions of the second region located above and below the first region are smaller than the portions of the second region located to the sides of the first region.

[0301] (51) The display device according to (49), 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.

[0302] (52) The optical system is positioned in the housing so as to overlap with the display panel when the inside of the housing is viewed from the viewing unit, and includes a semi-transparent mirror; The display device according to (49), wherein the length of the viewing portion along the longitudinal direction is greater than the length of the semi-transparent mirror along the longitudinal direction.

[0303] (53) The display device described in (49) above, wherein the angle formed by a first straight line connecting a first end of the image in the longitudinal direction to the center of the viewing portion and a second straight line connecting a second end of the image in the longitudinal direction to the center of the viewing portion is 70 degrees or less.

[0304] (54) The display device according to (49), wherein the image is sized so that more than half of it can be seen from the viewing portion when viewed from a distance farther than the focal position of the image.

[0305] (55) The optical system includes a semi-transparent mirror having a reflecting surface, The display device according to (49) above, wherein the optical path length from the display panel to the reflecting surface of the semi-transparent mirror is two-thirds or less of the focal length of the semi-transparent mirror.

[0306] (56) The display device according to (49), wherein the viewing portion is a window.

[0307] (57) The optical system has a semi-transparent mirror, The display device according to (49) above, wherein, in a cross-sectional view, an angle formed by two straight lines connecting both end points of the image and both end points of the semi-transparent mirror is an acute angle.

[0308] (58) The optical system has a semi-transparent mirror, The display device described in (49) above, wherein, in a cross-sectional view, the intersection of two straight lines connecting the two end points of the image and the two end points of the semi-transparent mirror is located outside the display device relative to the viewing section.

[0309] (59) The display device described in (49) above, 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.

[0310] (60) The display device according to (52) above, further comprising a shielding wall that shields an end of the semi-transparent mirror.

[0311] (61) The display device according to (60), wherein the shielding wall is positioned so as to shield the upper end, lower end, right end, and left end of the semi-transparent mirror.

[0312] (62) The display device according to (52), wherein the end of the semi-transparent mirror has a higher light absorption rate than the other parts of the semi-transparent mirror.

[0313] (63) The display device according to (49), wherein the size of the image is larger than the outer shape of the viewing surface on which the viewing portion of the housing is located, and is less than twice the size of the viewing surface.

[0314] (64) The display device according to (49), wherein the magnification of the image is less than 3 times.

[0315] (65) The visual confirmation portion is elongated in the vertical direction or the horizontal direction, the display panel displays an image; the optical system focuses the image to form an image; The display device according to (49), wherein the image is elongated along the longitudinal direction of the viewing portion.

[0316] (66) A display panel having a display surface; an optical system that focuses the display surface to form an image; Equipped with The optical system comprises: a reflective polarizer; a first retardation plate positioned between the display panel and the reflective polarizer; a second retardation plate located between the first retardation plate and the reflective polarizer; a semi-transparent mirror located between the first retardation plate and the second retardation plate and having a reflecting surface, A display device, wherein the optical path length from the display panel to the reflecting surface of the semi-transparent mirror is two-thirds or less of the focal length of the semi-transparent mirror.

[0317] (67) The display device according to (66), wherein the semi-transparent mirror is rectangular.

[0318] (68) A display panel having a display surface; an optical system that focuses the display surface to form an image; Equipped with The optical system comprises: a first retardation plate and a second retardation plate; a first semi-transparent mirror located between the display panel and the first retardation plate and having a first reflecting surface; a second semi-transparent mirror located between the first retardation plate and the second retardation plate and having a second reflecting surface, a light path length from the display panel to the first reflecting surface of the first semi-transparent mirror is equal to or less than two-thirds of a focal length of the first semi-transparent mirror;

[0319] (69) The display device according to (68), wherein the first semi-transparent mirror is rectangular.

[0320] (70) A housing having a visible portion; a display panel located within the housing that displays an image showing supplemental information; an optical system located within the housing and focusing the video to form an image; a control unit that controls the image on the display panel; Equipped with the 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, The control unit controls the video so that the supplemental information is displayed in the first area.

[0321] (71) A vehicle equipped with the display device according to any one of (49) to (70) above.

[0322] (72) A display panel for emitting display light; an optical system for forming an image of the display light, The optical system comprises: a reflective polarizer; a first retardation plate positioned between the display panel and the reflective polarizer; a second retardation plate located between the first retardation plate and the reflective polarizer; a first reflecting surface located between the first retardation plate and the second retardation plate; a first semi-transparent mirror having a larger index of collection, convergence, or the reciprocal of the focal length than other members of the optical system; Display device.

[0323] (73) The display device according to (72), wherein the first reflecting surface of the first semi-transparent mirror has a concave curved surface having a curvature greater than that of other members of the optical system.

[0324] (74) A display panel for emitting display light; an optical system for forming an image of the display light, The optical system comprises: a reflective polarizer; a first retardation plate positioned between the display panel and the reflective polarizer; a second retardation plate located between the first retardation plate and the reflective polarizer; a first semi-transparent plate having a first reflecting surface and positioned between the first retardation plate and the second retardation plate; and a fluoroscopic device; Except for the first semi-transparent mirror, the lens does not include any lens. Display device. (72) (75) A display panel for emitting display light; an optical system for forming an image of the display light, The optical system comprises: a reflective polarizer; a first retardation plate positioned between the display panel and the reflective polarizer; a second retardation plate located between the first retardation plate and the reflective polarizer; a first semi-transparent mirror located between the first retardation plate and the second retardation plate and having a first reflecting surface; A display device having only the first semi-transparent mirror as a member for converging the display light.

[0325] (76) The display device according to any one of (72) to (75) above, wherein air is interposed between the first retardation plate and the second retardation plate.

[0326] (77) The display device according to any one of (72) to (75) above, further comprising a third retardation plate positioned between the display panel and the reflective polarizer.

[0327] (78) The display device according to any one of (72) to (75) above, further comprising a fourth retardation plate positioned between the display panel and the reflective polarizer.

[0328] (79) The display device according to any one of (72) to (75), wherein the first retardation plate is disposed on a surface of the first semi-transparent mirror.

[0329] (80) The display device according to any one of (72) to (75), wherein the second retardation plate is disposed on a surface of the first semi-transparent mirror.

[0330] (81) A housing having a window; a display panel located within the housing for emitting display light; an optical system positioned within the housing so as to overlap with the display panel when the interior of the housing is viewed through the window, the optical system having a first semi-transparent mirror and configured to form an image from the display light; Equipped with A display device, wherein the first semi-transparent mirror has a degree of light collection, a degree of convergence, or an index represented by the reciprocal of the focal length that is greater than those of other members included in the optical system.

[0331] (82) A housing having a window; a display panel located within the housing for emitting display light; an optical system positioned within the housing so as to overlap with the display panel when the interior of the housing is viewed through the window, the optical system having a first semi-transparent mirror and configured to form an image from the display light; Equipped with A display device, wherein the optical system does not include a lens except for the first semi-transparent mirror.

[0332] (83) A housing having a window; a display panel located within the housing for emitting display light; an optical system positioned within the housing so as to overlap with the display panel when the interior of the housing is viewed through the window, the optical system having a first semi-transparent mirror and configured to form an image from the display light; Equipped with The display device, wherein the optical system has only the first semi-transparent mirror as a member for converging the display light.

[0333] (84) The display device according to any one of (72) to (83) above, wherein the first semi-transparent mirror has a Fresnel shape.

[0334] (85) The display device according to any one of (72) to (83) above, wherein the first semi-transparent mirror has a holographic optical element.

[0335] (86) The display device according to any one of (72) to (83) above, wherein the first semi-transparent mirror is a reflective polarizer.

[0336] (87) The display device according to any one of (72) to (83) above, wherein the optical system has a second semi-transparent mirror.

[0337] (88) The display device described in any one of (72) to (87) above, wherein the display light includes display light for an image for the left eye and display light for an image for the right eye, and further includes an optical element for specifying the direction of each light ray of the display light for the image for the left eye and the display light for the image for the right eye.

[0338] (89) The display device according to any one of (72) to (88) above, further comprising an illuminator for irradiating light onto a surface of the display panel opposite to a display surface for emitting the display light.

[0339] (90) The display device according to any one of (72) to (89) above, further comprising a controller having a function of controlling at least one of an image to be displayed on the display panel and the irradiator.

[0340] (91) A vehicle equipped with the display device according to any one of (72) to (90) above.

[0341] (92) The display device according to any one of (72) to (90) above, a camera; The display device is capable of communicating with the camera and displays images captured by the camera.

[0342] (93) A vehicle equipped with the display system described in (92) above.

[0343] (94) An imaging device including the display device according to any one of (72) to (90) above.

[0344] (95) A vehicle equipped with the imaging device described in (94) above.

[0345] (96) A housing having a window; a display panel located within the housing for emitting display light; an optical system located within the housing for focusing the display light into an image; Equipped with A display device wherein the longitudinal extent of the image is greater than the longitudinal extent of the window.

[0346] (97) The display device according to (96), wherein the longitudinal length of the image is greater than the length of the housing along the longitudinal direction.

[0347] (98) A housing having a window; a display panel located within the housing for emitting display light; an optical system located within the housing for forming an image from the display light; the image has a visible area that is visible from the window when a user stands still and looks at the window, and an invisible area that is not visible from the window; Display device.

[0348] (99) The display device according to any one of (96) to (98) above, further comprising a mechanism capable of changing the size or position of the image.

[0349] (100) A controller for controlling the display of the display panel is further provided. The display device according to any one of (96) to (99) above, wherein the controller is capable of changing the size or display position of the image.

[0350] (101) The display device according to (100), wherein the controller changes the size or display position of the image based on user information.

[0351] (102) When a user stands still and looks at the window, the image has a first area located on the right side of the window and a second area located on the left side 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.

[0352] (103) When a user stands still and looks at the window, the image has a first area located on the right side of the window and a second area located on the left side of the window, The display device according to (101), wherein the controller controls the display device so as to reduce a difference between the left-right width of the first region and the left-right width of the second region.

[0353] (104) A vehicle equipped with the display device according to any one of (96) to (103) above.

[0354] (105) The display device according to any one of (96) to (103) above, a camera capable of communicating with the display device, The display panel displays an image captured by the camera.

[0355] (106) A vehicle equipped with the display system described in (105) above.

[0356] (107) A display panel for emitting display light; an optical system for forming an image of the display light, the optical system having a pair of semi-transparent mirrors each having a reflective surface; Display device.

[0357] (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 reflecting surface of the second semi-transparent mirror diverges light incident on and reflected from the first semi-transparent mirror, the reflecting surface of the first semi-transparent mirror converges light incident from the second semi-transparent mirror side and reflected therefrom; The display device described above.

[0358] (109) The display device according to (108), wherein the reflecting surface of the first semi-transparent mirror has a concave curved surface.

[0359] (110) The display device according to (108), wherein the reflecting surface of the second semi-transparent mirror has a convex curved surface.

[0360] (111) The display device according to any one of the above (107) to (110), wherein at least one of the pair of semi-transparent mirrors has a Fresnel shape.

[0361] (112) The display device according to any one of the above (107) to (110), wherein at least one of the pair of semi-transparent mirrors is a holographic optical element.

[0362] (113) The display device according to any one of the above (107) to (110), wherein at least one of the pair of semi-transparent mirrors is a reflective polarizer.

[0363] (114) The display device according to any one of (107) to (113) above, wherein the optical system further includes a first retardation plate positioned between the pair of semi-transparent mirrors.

[0364] (115) The display device described in any one of (107) to (113) above, wherein the optical system further includes a polarizing plate positioned to sandwich the pair of semi-transparent mirrors between the polarizing plate and the display panel, and a second retardation plate positioned between the polarizing plate and the pair of semi-transparent mirrors.

[0365] (116) The display device according to (115) above, wherein the optical system further includes a third retardation plate positioned between the display panel and the polarizing plate.

[0366] (117) The display device according to (116), wherein the optical system further includes a fourth retardation plate positioned between the display panel and the polarizing plate.

[0367] (118) A housing having a window and accommodating the display panel and the optical system is further provided. The display device according to any one of (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 through the window.

[0368] (119) The display device according to any one of (107) to (118) above, wherein the display light includes display light for an image for the left eye and display light for an image for the right eye, and further includes an optical element that specifies the direction of each light ray of the display light for the image for the left eye and the display light for the image for the right eye.

[0369] (120) The display device according to any one of (107) to (119) above, further comprising an illuminator for irradiating light onto a surface of the display panel opposite to a display surface for emitting the display light.

[0370] (121) The display device according to any one of (107) to (120) above, further comprising a controller having a function of controlling at least one of an image to be displayed on the display panel and the irradiator.

[0371] (122) A vehicle equipped with the display device according to any one of (107) to (121) above.

[0372] (123) The display device according to any one of (107) to (121) above, a camera capable of communicating with the display device, The display panel displays an image captured by the camera.

[0373] (124) A vehicle equipped with the display system described in (123) above.

[0374] (125) An imaging device including the display device according to any one of (107) to (121) above.

[0375] (126) A vehicle equipped with the imaging device described above. [Explanation of symbols]

[0376] 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 Department of Optics 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 box 37 Windows 38 Light transmission plate 39,40 Moth-eye structure film 41 Touch Panel 42 Convex Lens 43 Controller 100 Imaging device 101 Reflective optical elements 102 Camera 200 Display System 201 Camera 401 1st area 402 Second area 403 Center of the Illusion 404 Normal to the center of the virtual image 405 User Center 406 The part of the second area located above and below the first area 407 The part of the second area located to the side of the first area 408 1st end 409 Center of the window 410 1st straight line 411 2nd end 412 Second straight line 413 and 414 End points of the virtual image 415 and 416 End points of semi-transparent mirror 417 and 418 Two lines connecting the two end points of the virtual image and the two end points of the semi-transparent mirror, respectively 419 Intersection of two lines connecting the two end points of the virtual image and the two end points of the semi-transparent mirror 420 End of semi-transparent mirror 421 Shielding Wall 422 Visibility Surface 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 semitransparent mirror focus L6 Longitudinal length of the semi-transparent mirror L37 Length along the longitudinal direction of the window Lf6 semi-transparent mirror focal length V428 Virtual Image V429 Virtual Image WL Longitudinal direction of the window

Claims

1. A display panel having a display surface; an optical system for imaging the display surface to form a virtual image, The optical system comprises: a first semi-transparent mirror having a reflective surface with a function of reflective polarization; a second semi-transparent mirror located on the opposite side of the display panel from the first semi-transparent mirror; a first retardation plate located between the first semi-transparent mirror and the second semi-transparent mirror; A non-wearable display device for the user.

2. The optical system comprises: a second retardation plate located on the opposite side of the second semi-transparent mirror from the first retardation plate; 2. The display device according to claim 1, further comprising: a polarizing plate located on the opposite side of said second half-mirror with respect to said second retardation plate.

3. A display device as described in Claim 1, wherein the optical system images only the light reflected by the second semi-transparent mirror and the first semi-transparent mirror out of the display light emitted by the display panel.

4. A housing having a visual recognition section, the optical system and the display panel are located within the housing; The display device according to claim 1 , wherein the display panel has a planar display surface that faces the viewing portion.

5. A display device as described in claim 1, wherein the reflective surface of the first semi-transparent mirror has the function of reflecting and converging light toward the opposite side to the display panel, and the index of the first semi-transparent mirror expressed as the reciprocal of the concentration, convergence or focal length is greater than that of other components of the optical system.

6. A display device as described in claim 2, wherein the optical system has a third phase difference plate positioned between the display panel and the first phase difference plate or between the second phase difference plate and the polarizing plate, and arranged so that its optical axis is approximately parallel to or approximately perpendicular to the transmission axis of the polarizing plate.

7. A display device as described in claim 2, wherein the optical system has a fourth phase difference plate positioned between the display panel and the first phase difference plate or between the second phase difference plate and the polarizing plate, and arranged so that its optical axis is approximately parallel to or approximately perpendicular to the transmission axis of the polarizing plate.

8. A display device as described in claim 1, wherein at least one of the first semi-transparent mirror and the second semi-transparent mirror has a Fresnel shape.

9. A display device as described in claim 1, wherein at least one of the first semi-transparent mirror and the second semi-transparent mirror is a holographic optical element.

10. A display device as described in claim 1, wherein the first semi-transparent mirror is a reflective polarizer.

11. A display device as described in claim 1, wherein the display light emitted by the display panel includes display light for an image for the left eye and display light for an image for the right eye, and further includes an optical element for specifying the direction of each light ray of the display light for the image for the left eye and the display light for the image for the right eye.

12. A display device as described in claim 1, comprising an illuminator for irradiating light onto the surface of the display panel opposite the display surface.

13. A display device as described in claim 12, comprising a controller having the function of controlling at least one of the image to be displayed on the display panel and the illuminator.

14. A display device as described in claim 1, fixed to the interior of a vehicle.

15. A mobile object equipped with a display device according to any one of claims 1 to 14.

16. A display device according to claim 1; a camera capable of communicating with the display device, The display panel displays an image captured by the camera.

17. A mobile object equipped with the display system described in claim 16.

18. A display panel installation section capable of installing a display panel having a display surface; an optical system for imaging the display surface to form a virtual image, The optical system comprises: a first semi-transparent mirror having a reflective surface with a function of reflective polarization; a second semi-transparent mirror located on the opposite side of the display panel installation section with respect to the first semi-transparent mirror, A display panel housing device that is not wearable by the user.

Images