Display device, imaging device, display system, and vehicle

Abstract

A display device includes a display panel, a first phase difference plate, a semi-transmissive mirror, a second phase difference plate, and a reflective polarizing plate. The display panel emits display light. The first phase difference plate is disposed so as to face the display panel. The second phase difference plate is disposed apart from the first phase difference plate. The reflective polarizing plate is disposed so as to face the second phase difference plate, transmits the first polarized light, and reflects the second polarized light. The semi-transmitting mirror is disposed between the first phase difference plate and the second phase difference plate, and has a reflecting surface facing the second phase difference plate. The first phase difference plate and the second phase difference plate convert the display light into first polarized light and second polarized light.

Description

Technical Field

[0001] The present invention relates to a display device, an imaging device, a display system, and a vehicle. Background Art

[0002] Conventionally, for example, a display device described in Patent Document 1 has been known.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-63533 Summary of the Invention

[0006] The display device of the present invention includes:

[0007] a display panel that emits display light;

[0008] a first retardation plate that faces the display panel;

[0009] a second retardation plate that is disposed separately from the first retardation plate;

[0010] a reflective polarizing plate that is disposed to face the second retardation plate and transmits first polarized light and reflects second polarized light; and

[0011] a half mirror that is disposed between the first retardation plate and the second retardation plate and has a reflection surface that faces the second retardation plate,

[0012] the first retardation plate and the second retardation plate convert the display light into first polarized light and second polarized light.

[0013] In addition, the display device of the present invention includes:

[0014] a display panel that emits display light;

[0015] a first retardation plate that transmits the display light;

[0016] a second retardation plate that is disposed separately from the first retardation plate;

[0017] a first half mirror that is disposed between the display panel and the first retardation plate and has a first reflection surface that faces the first retardation plate;

[0018] a second half mirror that is disposed between the first retardation plate and the second retardation plate and has a second reflection surface that faces the first retardation plate; and

[0019] a polarizing plate that faces the second retardation plate,

[0020] The first retardation plate and the second retardation plate make the display light into a first polarized light that transmits through the polarizing plate and a second polarized light that is less transmissive through the polarizing plate than the first polarized light.

[0021] In addition, the display device of the present invention includes:

[0022] A display panel that emits display light;

[0023] A first retardation plate that transmits the display light;

[0024] A second retardation plate that is disposed separately from the first retardation plate;

[0025] A first semi-transmissive mirror that is disposed between the display panel and the first retardation plate and has a first reflective surface facing the first retardation plate;

[0026] A second semi-transmissive mirror that is disposed between the first retardation plate and the second retardation plate and has a second reflective surface facing the first retardation plate and a third reflective surface facing the second retardation plate; and

[0027] A third semi-transmissive mirror that has a fourth reflective surface facing the second retardation plate.

[0028] The imaging device of the present invention includes the above-mentioned display device.

[0029] In addition, the display device of the present invention includes:

[0030] A display panel;

[0031] An optical system that projects the display light emitted from the display panel as a virtual image or a real image; and

[0032] A housing that houses the display panel and the optical system,

[0033] The housing has a window that transmits the light emitted from the optical system,

[0034] The display device is configured such that the window, the optical system, and the display panel overlap when observing the window of the housing.

[0035] The vehicle of the present invention includes the above-mentioned display device.

[0036] In addition, the display device of the present invention includes:

[0037] A display panel that emits display light; and

[0038] A convex lens through which the display light transmits,

[0039] The optical path length from the display panel to the convex lens is smaller than the focal length of the convex lens.

[0040] In addition, the display device of the present invention includes:

[0041] A display panel that emits display light; and

[0042] A convex lens through which the display light is transmitted,

[0043] The optical path length from the display panel to the convex lens is larger than the focal length of the convex lens.

[0044] The display system of the present invention includes:

[0045] The above-described display device; and

[0046] A camera,

[0047] The display panel can communicate with the camera and display an image captured by the camera.

[0048] The vehicle of the present invention includes the above-described display system. Description of the Drawings

[0049] The objects, features, and advantages of the present invention will be further clarified by the following detailed description and the drawings.

[0050] Figure 1 is a diagram schematically showing the structure of the display device of the present invention.

[0051] Figure 2 is a cross-sectional view showing an example of the main part structure of the display device according to an embodiment of the present invention.

[0052] Figure 3 is a cross-sectional view showing another example of the main part structure of the display device according to an embodiment of the present invention.

[0053] Figure 4 is a cross-sectional view showing an example of the main part structure of the display device according to another embodiment of the present invention.

[0054] Figure 5 is a cross-sectional view showing another example of the main part structure of the display device according to another embodiment of the present invention.

[0055] Figure 6 is for Figure 4 the projection of the virtual image of the display device.

[0056] Figure 7 is for Figure 5 the projection of the virtual image of the display device.

[0057] Figure 8 is a diagram for explaining the design of the optical system in the display device of Figure 5 .

[0058] Figure 9 is a cross-sectional view showing an example of the main part structure of a display device according to another embodiment of the present invention.

[0059] Figure 10 is a diagram showing an example of the structure of an imaging device according to an embodiment of the present invention.

[0060] Figure 11 is a diagram showing another example of the structure of an imaging device according to an embodiment of the present invention.

[0061] Figure 12 is a diagram showing another example of the structure of an imaging device according to an embodiment of the present invention.

[0062] Figure 13 is a top view for explaining another example of the display device.

[0063] Figure 14 is a top view for explaining another example of the display device.

[0064] Figure 15 is a cross-sectional view for explaining another example of the display device.

[0065] Figure 16 is a cross-sectional view for explaining another example of the display device.

[0066] Figure 17A is a diagram for explaining the optical system in another example of the display device.

[0067] Figure 17B is a diagram for explaining the optical system in another example of the display device.

[0068] Figure 17C is a diagram for explaining the optical system in another example of the display device.

[0069] Figure 17D is a diagram for explaining the optical system in another example of the display device.

[0070] Figure 18A is a diagram for explaining the optical system in another example of the display device.

[0071] Figure 18B is a diagram for explaining the optical system in another example of the display device.

[0072] Figure 18CIt is a diagram for explaining the optical system in other examples of the display device.

[0073] Figure 18D It is a diagram for explaining the optical system in other examples of the display device.

[0074] Figure 19 It is a diagram for explaining the optical system in other examples of the display device.

[0075] Figure 20 It is a cross-sectional view for explaining other examples of the display device.

[0076] Figure 21 It is a cross-sectional view for explaining other examples of the display device.

[0077] Figure 22 It is a cross-sectional view for explaining other examples of the display device.

[0078] Figure 23 It is a cross-sectional view showing an example of the structure of the second semi-transmissive mirror.

[0079] Figure 24 It is a cross-sectional view for explaining other examples of the display device.

[0080] Figure 25 It is a diagram for explaining the presentation form of the virtual image when the user is located in front of the display device.

[0081] Figure 26 It is a diagram for explaining the presentation form of the virtual image when the user is not located in front of the display device.

[0082] Figure 27 It is a diagram for explaining the presentation form of the virtual image when the display device is adjusted.

[0083] Figure 28 It is a diagram for explaining the presentation form of the virtual image when the display device is adjusted.

[0084] Figure 29 It is a flowchart for explaining the control of the imaging device.

[0085] Figure 30 It is a cross-sectional view showing other examples of the main part structure of the display device according to an embodiment of the present invention.

[0086] Figure 31 It is a cross-sectional view showing other examples of the main part structure of the display device according to other embodiments of the present invention.

[0087] Figure 32 It is a cross-sectional view showing other examples of the main part structure of the display device according to still another other embodiment of the present invention.

[0088] Figure 33 It is a perspective view showing a cross section of another example of the display device according to the embodiment of the present invention.

[0089] Figure 34 This is a cross-sectional view showing another example of the display device according to the embodiment of the present invention.

[0090] Figure 35 It is a perspective view showing a cross section of another example of the display device according to the embodiment of the present invention.

[0091] Figure 36 This is a cross-sectional view showing another example of the display device according to the embodiment of the present invention.

[0092] Figure 37 It is shown Figure 2 A diagram of the optical path of display light in a display device.

[0093] Figure 38 It is shown Figure 2 A cross-sectional view of another example of a display device.

[0094] Figure 39 This is a diagram showing an example of the configuration of a display system and a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0095] In the past, various small display devices have been proposed for use in digital interior rearview mirrors arranged in a vehicle cabin, head-mounted displays worn on the head of a user, etc. The display device described in Patent Document 1 is configured to emit display light emitted from a display panel through multiple optical components such as a phase difference plate and a reflective polarizing plate.

[0096] In conventional display devices, deformation of optical members and positional shifts between optical members are likely to occur, and display quality may be degraded.

[0097] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The figures used in the following description are also schematic figures. The figures used in the following description illustrate the main components of the display device and the virtual image display device of the present invention. The display device and the virtual image display device of the present invention may include well-known components such as a retaining member and a housing of the optical system that are not shown in the figure. In this specification, in some of the drawings, for convenience, an orthogonal coordinate system XYZ is defined. The Y-axis direction is also called the height direction. The Z-axis direction is also called the emission direction or the depth direction.

[0098] Figures 1 to 39 It is a figure or a diagram for explaining the display device, imaging device, display system, and vehicle of the present invention. Figures 2 to 5, among 9, 15, 16, 20 - 22, 24, 30 - 32, for easy view understanding, the optical path of the light incident on the light-reflective optical member and the optical path of the light reflected by the optical member are shown offset in the height direction (Y-axis direction).

[0099] A display device 1 according to an embodiment of the present invention is provided as Figure 1 shown, and includes a display panel 2 and an optical system 3. The display device 1 causes a part of the display light emitted from the display panel 2 to be incident on the eyes of the user 22, and enables the user 22 to visually confirm it as an image formation, an image, or an aerial image. The display device 1 can enable the user 22 to visually confirm the display light emitted from the display panel 2 at a position different from the position of the display panel 2 as the display of the display panel 2. In the position embodiment of the present invention, the display device 1 enables the user 22 to visually confirm it as a virtual image V. The virtual image V can be imaged on the far side of the display device 1 when observed from the user 22. The virtual image V can be an upright virtual image obtained by magnifying the display image displayed on the display panel 2. When the display device 1 includes a housing (refer to Figures 33 to 36 ) that houses the display panel 2 and the optical system 3, the virtual image V can be imaged inside the housing or outside the housing. When observed from the user 22, the virtual image V can be imaged on the far side of the display panel 2 or on the near side of the display panel 2. When the housing has a window 37 (refer to Figures 33 to 36 ) that transmits the display light emitted from the optical system 3, when observed from the user 22, the virtual image V can be imaged on the far side of the window 37 (light transmission plate 38) or on the near side of the window. When the display device 1 has a touch panel 41 (refer to Figure 35 , 36 ), when observed from the user 22, the virtual image V can be imaged on the far side of the touch panel 41 or on the near side of the touch panel 41.

[0100] It should be noted that the display device 1 can also be configured to cause a part of the display light emitted from the display panel 2 to be incident on the eyes of the user 22, and enable the user 22 to visually confirm it as a real image. The real image can be imaged on the near side of the display device 1 when observed from the user 22. When the display device 1 includes a housing 36 (refer to Figures 33 to 36 ) that houses the display panel 2 and the optical system 3, the real image can be imaged inside the housing 36 or outside the housing 36. When observed from the user 22, the real image can be imaged on the far side of the display panel 2 or on the near side of the display panel 2. When the housing 36 has a window 37 (refer to Figures 33 to 36In the case of Figure 35 , 36 when observed from the user 22, the real image can be formed on the side farther from the window 37 (light transmission plate 38) or on the side closer to the window 37 (light transmission plate 38).

[0101] 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 the display light of the display image from the display surface 2a. The display panel 2 can be configured to emit linearly polarized display light. Hereinafter, the case where the display panel 2 emits S-wave polarized display light will be described, but it is not limited thereto.

[0102] The display panel 2 can be a liquid crystal panel. The liquid crystal panel can have a structure of a known liquid crystal panel. A known liquid crystal panel can be, for example, a liquid crystal panel of an IPS (In-Plane Switching) method, an FFS (Fringe Field Switching) method, a VA (Vertical Alignment) method, an ECB (Electrically Controlled Birefringence) method, or the like.

[0103] The display device 1 can include an irradiator 4 that irradiates the display panel 2 in a surface manner. The irradiator 4 is also called a backlight. The irradiator 4 can be a side-light type backlight or a direct-lit type backlight. The side-light type backlight has one or more light sources disposed at the outer peripheral portion of the display panel 2, and guides the light emitted from the light sources to the entire back surface of the display panel 2 by a light guide plate to be uniformly dispersed. The direct-lit type backlight has a plurality of light sources arranged on the back side of the display panel 2, and irradiates the display panel 2 with the light emitted from the plurality of light sources. The light source of the irradiator 4 can be a cold cathode fluorescent lamp, a halogen lamp, a xenon lamp, or the like, or can be a light emitting diode (LED), an organic light emitting diode (OLED), a semiconductor laser (LD), or the like. When the light source of the irradiator 4 is an LD with excellent monochromaticity, the design of the optical system 3, particularly the design of the optical member having wavelength dependence of optical characteristics, becomes easy.

[0104] The display panel 2 is not limited to a liquid crystal panel (a transmissive display panel). The display panel 2 can also be, for example, a self-luminous display panel including a self-luminous element such as a Light Emitting Diode (LED), an Organic Light Emitting Diode (OLED), or a Laser Diode (LD).

[0105] The optical system 3 projects the display light emitted from the display panel 2 as a virtual image V within the field of view of the user 22. The optical system 3 can be configured as shown Figure 2 to include a first retardation plate 5, a half mirror 6, a second retardation plate 7, and a reflective polarizing plate 8. The first retardation plate 5, the half mirror 6, the second retardation plate 7, and the reflective polarizing plate 8 are arranged in sequence in the emission direction (the positive direction of the Z-axis direction) of the display light from the display panel 2.

[0106] The first retardation plate 5 is arranged opposite to the display surface 2a of the display panel 2. The first retardation plate 5 is arranged separated from the display surface 2a in the emission direction of the display light from the display panel 2. The second retardation plate 7 is arranged separated from the first retardation plate 5 in the emission direction of the 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 (the polarization plane of the electric field vibration direction) of the incident light. Thereby, a part of the display light emitted from the display panel 2 can be reflected by the reflective polarizing plate 8 and incident on the half mirror 6.

[0107] The first retardation plate 5 and the second retardation plate 7 only need to impart a required phase difference to the light transmitted through the first retardation plate 5 and the second retardation plate 7 in such a manner that the light transmitted through the first retardation plate 5 and the second retardation plate 7 is reflected by the reflective polarizing plate 8. That is, for example, when the polarized light obtained by transmitting through the first retardation plate 5 and the second retardation plate 7 is set as the second polarized light, as long as the second polarized light can be obtained for the first retardation plate 5 and the second retardation plate 7, they may not be quarter-wave plates but other wave plates or a combination thereof. It should be noted that in the present invention, the case where the first retardation plate 5 and the second retardation plate 7 are quarter-wave plates is taken as an example for description.

[0108] In addition, the second retardation plate 7 may impart a required phase difference to the light transmitted through the second retardation plate 7 such that the light 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. That is, for example, when the polarized light obtained by reflecting by the reflective polarizing plate 8 and transmitting through the second retardation plate 7 is defined as the first polarized light, as long as the second retardation plate 7 can obtain the first polarized light, it may not be a quarter-wave plate but other wave plates.

[0109] The first retardation plate 5 may also be integrated with the display panel 2 as Figure 30 shown. It should be noted that "integration" may mean that two components are arranged in contact with each other, or may mean that two components are joined to each other using an optically transparent adhesive such as OCA (Optically Clear Adhesive).

[0110] The half mirror 6 is located between the first retardation plate 5 and the second retardation plate 7. The half mirror 6 may also transmit a part of the incident light (for example, approximately 50%) and reflect the remaining part (for example, approximately 50%). The half mirror 6 reflects a part of the display light reflected by the reflective polarizing plate 8 and enters the eyes of the user 22. Thereby, the user 22 can visually confirm the virtual image V. The half mirror 6 may be a concave mirror having a concave reflective surface 6a facing the second retardation plate 7 as Figure 2 shown. The half mirror 6 may include a spherical shape, an aspherical shape, or a free-form surface shape on at least a part of the reflective surface 6a.

[0111] The half mirror 6 is configured to include a substrate and a half-transmissive reflective layer on the surface of the substrate, for example. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be made of a resin material, a glass material, etc., for example. The resin material may be an acrylic resin, a polycarbonate resin, etc., for example. The half-transmissive reflective layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum or chromium, for example. The half-transmissive reflective layer is not limited to a metal thin film and may be an electrolyte multilayer film, etc., for example. The half mirror 6 may be a structure that reflects light using the half-transmissive reflective layer. The half-transmissive reflective layer may be formed on the surface of the substrate facing the second retardation plate 7.

[0112] The reflective polarizing plate 8 is disposed to face the side opposite to the surface of the second retardation plate 7 facing the semi-transmissive mirror 6. In other words, the reflective polarizing plate 8 is located at the rear stage of the second retardation plate 7 in the emission direction of the display light from the display panel 2. The reflective polarizing plate 8 can transmit a part of the incident light and reflect the remaining part. In the present embodiment, the reflective polarizing plate 8 is configured to reflect polarized light (also referred to as P-wave polarized light, second polarized light) having a polarization axis perpendicular to the polarization axis of the display light and transmit polarized light (also referred to as S-wave polarized light, first polarized light) having a polarization axis parallel to the polarization axis of the display light. Thereby, the user 22 can visually confirm the virtual image V. The reflective polarizing plate 8 may also be integrated with the second retardation plate 7 as shown in Figure 30 shown.

[0113] The reflective polarizing plate 8 may be, for example, a wire grid polarizer configured to include a substrate and a plurality of metal fine lines (also referred to as a metal nanowire grid) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be made of, for example, a resin material, a glass material, or the like. The metal fine lines may be made of a metal material such as aluminum, chromium, titanium oxide, or the like. The metal fine lines may be arranged in one direction. The reflective polarizing plate 8 can transmit the light component vibrating in the direction orthogonal to the wire grid and can reflect the light component vibrating in the direction parallel to the wire grid.

[0114] 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 can control the illuminator 4. The controller 43 can control the display image displayed on the display panel 2 and the illuminator 4. The controller 43 can control the illuminator 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 read a specific program and execute a specific function and a dedicated processor dedicated to a specific process. The processor may include a PLD (Programmable Logic Device). The controller 43 may be any one of an SoC (System-on-a-Chip) and a SiP (System In a Package) in which one or more processors cooperate. The controller 43 may include a storage unit and store various information, a program for operating each component of the display device 1, and the like in the storage unit. The storage unit may be composed of, for example, a semiconductor memory. The storage unit may function as a working memory of the controller 43.

[0115] The optical function of the optical system 3 will be described. The display panel 2 emits display light that is S-wave polarized light (first linearly polarized light L1). The display light of the first linearly polarized light L1 emitted from the display panel 2 passes through the first retardation plate 5 and is converted into light of the first circularly polarized light C1. A part (for example, approximately 50%) of the first circularly polarized light C1 that has passed through the first retardation plate 5 passes through the half mirror 6. The first circularly polarized light C1 that has passed through the half mirror 6 passes through the second retardation plate 7 and is converted into light of the second linearly polarized light L2 whose polarization direction is orthogonal to the first linearly polarized light L1 (i.e., is P-wave polarized light). The light of the second linearly polarized light L2 is incident on the reflective polarizing plate 8. As described above, the reflective polarizing plate 8 reflects the light of the P-wave polarized light and transmits the light of the S-wave polarized light. The light of the second linearly polarized light L2 incident on the reflective polarizing plate 8 is reflected by the reflective polarizing plate 8 and is converted into light of the third linearly polarized light L3. The light of the third linearly polarized light L3 passes through the second retardation plate 7 and is converted into light of the second circularly polarized light C2. A part (for example, approximately 50%) of the light of the second circularly polarized light C2 that has passed through the second retardation plate 7 is reflected by the half mirror 6 and is converted into light of the third circularly polarized light C3. The light of the third circularly polarized light C3 passes through the second retardation plate 7 and is converted into light of the fourth linearly polarized light L4 whose polarization direction is parallel to the first linearly polarized light L1 (i.e., is S-wave polarized light). The light of the fourth linearly polarized light L4 passes through the reflective polarizing plate 8 and is emitted to the outside. The light quantity (brightness) of the light emitted from the display device 1 becomes, for example, approximately 25% of the light quantity (brightness) of the display light emitted from the display panel 2.

[0116] The first retardation plate 5, the half mirror 6, the second retardation plate 7, and the reflective polarizing plate 8 are maintained in their relative positions by being held by a holding member (not shown). Air is interposed between the first retardation plate 5 and the second retardation plate 7 (i.e., between the first retardation plate 5 and the half mirror 6 and between the half mirror 6 and the second retardation plate 7). The display device 1 has a structure in which no member made of a resin material such as a polymer is provided between the first retardation plate 5 and the second retardation plate 7. Therefore, it is possible to reduce the possibility of deformation of the half mirror 6, displacement of the positions of the half mirror 6, the first retardation plate 5, and the second retardation plate 7, etc. when the resin material is hardened during the manufacturing process of the display device 1. In addition, a resin material such as a polymer has a retardation peculiar to the material, and thus it is also possible to reduce the possibility of changing the polarization state of the light that has passed through the resin material. As a result, it is possible to reduce the degradation of the display quality.

[0117] 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 the same. Therefore, the occupied space of the optical system 3 can be reduced, and as a result, the display device 1 can be miniaturized. In addition, since the optical system 3 is of the on-axis type, the distortion, brightness unevenness, etc. of the virtual image V visually confirmed by the user 22 can be reduced, and the design of the optical system 3 becomes easier.

[0118] The display device 1 can make the optical path length of the light that exits from the display panel 2, passes through the half-transmissive mirror 6, is reflected by the reflective polarizing plate 8, and reaches the half-transmissive mirror 6 smaller than the focal length of the half-transmissive mirror 6. In this case, the user 22 can visually confirm the virtual image V. The display device 1 can make the optical path length of the light that exits from the display panel 2, passes through the half-transmissive mirror 6, is reflected by the reflective polarizing plate 8, and reaches the half-transmissive mirror 6 larger than the focal length of the half-transmissive mirror 6. In this case, the user 22 can visually confirm the real image.

[0119] In Figure 2 order to facilitate view understanding, the optical path of the light incident on the reflective polarizing plate 8 and the optical path of the light reflected by the reflective polarizing plate 8 are shown offset in the height direction (Y-axis direction), and the optical path of the light incident on the half-transmissive mirror 6 and the optical path of the light reflected by the half-transmissive mirror 6 are shown offset in the height direction (Y-axis direction). However, in reality, the display light emitted from the display panel 2 propagates substantially on one axis as Figure 37 shown. This is the same for the optical paths shown in Figures 3 to 5 , 9, 15, 16, 20~22, 24, 30~32.

[0120] The display device 1 can also replace the first retardation plate 5, the half-transmissive mirror 6, the second retardation plate 7, and the reflective polarizing plate 8 with a convex lens 42 as Figure 38 shown. The display device 1 can make the optical path length from the display panel 2 to the convex lens 42 smaller than the focal length of the convex lens 42. In this case, the user 22 can visually confirm the virtual image V. The display device 1 can make the optical path length from the display panel 2 to the convex lens 42 larger than the focal length of the convex lens 42. In this case, the user 22 can visually confirm the real image.

[0121] The display panel 2 can display a mixed image including a left-eye image and a right-eye image having parallax with each other, and emit the display light of the mixed image. The display device 1 can be as Figure 3As shown in the figure, there is an optical element 9 in the optical path of the display light emitted from the display panel 2. The optical element 9 is configured to allow a part of the display light of the mixed image to reach one of the left eye and the right eye of the user 22, and allow the other part of the display light to reach the other of the left eye and the right eye of the user 22. The optical element 9 is configured to make at least a part of the display light of the left-eye image reach the left eye of the user 22 and make at least a part of the display light of the right-eye image reach the right eye of the user 22 by specifying the light directions of the display light of the left-eye image and the display light of the right-eye image. Thereby, the display device 1 can enable the user 22 to visually recognize a stereoscopic image.

[0122] The optical element 9 only needs to allow a part of the display light of the mixed image to reach one of the left eye and the right eye of the user 22 and allow the other part of the display light to reach the other of the left eye and the right eye of the user 22. For example, it can be a parallax barrier or a lenticular lens. The parallax barrier can be composed of a liquid crystal panel. The position of the optical element 9 is arbitrary inside the display device 1. The optical element 9 can be located between the display panel 2 and the first retardation plate 5, can be located in the subsequent stage of the reflective polarizing plate 8 in the light emission direction of the display light, or can be located between the half mirror 6 and the second retardation plate 7.

[0123] Next, a display device according to another embodiment of the present invention will be described. In the display device of the present embodiment, the structure of the optical system is different from that of the display device of the above embodiment. For other structures, since they are the same structures, the same reference numerals are used for the same structures, and detailed descriptions are omitted.

[0124] The display device 1A of the present embodiment is as Figure 4 shown, and 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 the display light emitted from the display panel 2 as a virtual image V within the visual field of the user 22.

[0125] The optical system 10 is configured to include a first half mirror 11, a first retardation plate 12, a second half mirror 13, a second retardation plate 14, and a polarizing plate 15. The first half mirror 11, the first retardation plate 12, the second half mirror 13, the second retardation plate 14, and the polarizing plate 15 are arranged in sequence in the light emission direction of the display light from the display panel 2.

[0126] The first retardation plate 12 is disposed opposite to the reflecting surface 11a of the first half-transmissive mirror 11. The first retardation plate 12 is disposed separated from the display surface 2a in the emission direction of the display light from the display panel 2. The second retardation plate 14 is disposed separated from the first retardation plate 12 in the emission direction of the display light. The first retardation plate 12 and the second retardation plate 14 are quarter-wave plates.

[0127] The first half-transmissive mirror 11 is located between the display panel 2 and the first retardation plate 12. The first half-transmissive mirror 11 can transmit a part of the incident light and reflect the remaining part. As Figure 4 shown, it is a concave mirror having a concave reflecting surface 11a opposed to the first retardation plate 12. In the present embodiment, the first half-transmissive mirror 11 may be configured to transmit the light of the S-wave polarization and reflect the light of the P-wave polarization. The first half-transmissive mirror 11 may include a spherical shape, an aspherical shape, or a free-form surface shape at least in a part of the reflecting surface 11a.

[0128] The first half-transmissive mirror 11 may be configured to include, for example, a substrate and a plurality of metal fine wires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to the light in the visible light band. The substrate may be made of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal fine wires may be made of a metal material such as aluminum, chromium, titanium oxide, etc. The metal fine wires may be arranged along one direction. The first half-transmissive mirror 11 can transmit the light component vibrating in the direction orthogonal to the wire grid and can reflect the light component vibrating in the direction parallel to the wire grid. The metal nanowire grid may be formed on the surface of the substrate on the side of the first retardation plate 12. It should be noted that, in this example, the function of reflecting polarized light is given to the first half-transmissive mirror 11 by using the metal nanowire grid, but the first half-transmissive mirror 11 may be a simple half-lens, and a reflective polarizing plate may be provided separately.

[0129] The second half-transmissive mirror 13 is located between the first retardation plate 12 and the second retardation plate 14. The second half-transmissive mirror 13 can transmit a part of the incident light (for example, approximately 50%) and reflect the remaining part (for example, approximately 50%). The second half-transmissive mirror 13 may be Figure 4 a plane mirror whose reflecting surface 13a is disposed to face the first retardation plate 12 as shown. The second half-transmissive mirror 13 is also referred to as a plane half-lens. The second half-transmissive mirror 13 may also be Figure 31 integrated with the first retardation plate 12 and / or the second retardation plate 14 as shown.

[0130] The second half-transmissive mirror 13 can be configured to include a substrate and a half-transmissive reflective layer located on the surface of the substrate. The substrate can have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate can be made of, for example, inorganic glass, resin material, etc. The resin material can be, for example, acrylic resin, polycarbonate resin, etc. The half-transmissive reflective layer can be a metal thin film. The metal thin film can be made of, for example, metal materials such as aluminum and chromium. The half-transmissive reflective layer is not limited to a metal thin film, and can also be, for example, an electrolyte multilayer film, etc.

[0131] The polarizing plate 15 is disposed to face the opposite side of the surface of the second retardation plate 14 that faces the second half-transmissive mirror 13. In other words, the polarizing plate 15 is located in the rear stage of the second retardation plate 14 in the light emission direction of the display light from the display panel 2. The polarizing plate 15 can transmit a part of the incident light and absorb the remaining part. In the present embodiment, the polarizing plate 15 is configured to transmit the light of P-wave polarization and absorb the light of S-wave polarization. The polarizing plate 15 can also be integrated with the second retardation plate 14 as Figure 31 shown.

[0132] The polarizing plate 15 can have the structure of a known absorption type polarizing plate. A known absorption type polarizing plate can also be, for example, an iodine-based polarizing plate in which an iodine compound is adsorbed and oriented on a polyvinyl alcohol (PVA) film, a dye-based polarizing plate in which a dichroic organic dye is adsorbed and oriented on a PVA film, etc.

[0133] The optical function of the optical system 10 will be described. The display light of S-wave polarization (first linearly polarized light L1) emitted from the display panel 2 passes through the first half-transmissive mirror 11. The display light of the first linearly polarized light L1 passes through the first retardation plate 12 and is converted into light of a first circularly polarized light C1. The light of the first circularly polarized light C1 is incident on the second half-transmissive mirror 13. A part (for example, approximately 50%) of the light of the first circularly polarized light C1 is reflected by the second half-transmissive mirror 13 and is converted into light of a second circularly polarized light C2. The light of the second circularly polarized light C2 passes through the first retardation plate 12 and is converted into light of a second linearly polarized light L2 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., is P-wave polarization). The light of the second linearly polarized light L2 is reflected by the first half-transmissive mirror 11 and is converted into light of a third linearly polarized light L3 whose polarization direction is orthogonal to that of the first linearly polarized light L1. The light of the third linearly polarized light L3 passes through the first retardation plate 12 and is converted into light of a third circularly polarized light C3. A part (for example, approximately 50%) of the light of the third circularly polarized light C3 passes through the second half-transmissive mirror 13. The light of the third circularly polarized light C3 that has passed through the second half-transmissive mirror 13 passes through the second retardation plate 14 and is converted into light of a fourth linearly polarized light L4 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (i.e., is P-wave polarization). The light of the fourth linearly polarized light L4 passes through the polarizing plate 15 and is emitted to the outside.

[0134] The remaining part of the light of the first circularly polarized light C1 (e.g., approximately 50%) is transmitted through the second half-transmissive mirror 13, then transmitted through the second retardation plate 14, and is transformed into the light of the 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 light of the fifth linearly polarized light L5 is absorbed by the polarizing plate 15, and thus does not exit to the outside. In other words, the light of the fifth linearly polarized light L5 is the light with less transmission through the polarizing plate 15. Therefore, the amount of light (brightness) of the light exiting from the display device 1A becomes, for example, approximately 25% of the amount of light (brightness) of the display light exiting from the display panel 2.

[0135] It should be noted that in the above, an example in which the first retardation plate 12 and the second retardation plate 14 are quarter-wave plates has been described. However, for the first retardation plate 12 and the second retardation plate 14, as long as a part of the light is absorbed by the polarizing plate 15 and the other light is transmitted through the polarizing plate 15, they may not be quarter-wave plates, but other wave plates or a combination thereof. In addition, as long as a part of the light is reflected by the first half-transmissive mirror 11 and the other light is transmitted through the first half-transmissive mirror 11, the first retardation plate 12 and the second retardation plate 14 may not be quarter-wave plates, but other wave plates or a combination thereof.

[0136] The first half-transmissive mirror 11, the first retardation plate 12, the second half-transmissive mirror 13, the second retardation plate 14, and the polarizing plate 15 are held by a holding member (not shown) to maintain their relative positions. Air is interposed between the first half-transmissive mirror 11 and the first retardation plate 12. The display device 1A has a structure in which no member made of a resin material such as a polymer is provided between the first half-transmissive mirror 11 and the first retardation plate 12. Therefore, it is possible to reduce the possibility of deformation of the first half-transmissive mirror 11, positional deviation between the first half-transmissive mirror 11 and the first retardation plate 12, etc. when the resin material is hardened during the manufacturing process of the display device 1A. As a result, it is possible to reduce the degradation of the display quality.

[0137] The optical system 10 is a coaxial type optical system in which the optical axis of the incident light and the optical axis of the exiting light are substantially the same. Therefore, the occupied space of the optical system 10 can be reduced. As a result, the display device 1A can be miniaturized. In addition, since the optical system 10 is a coaxial type, it is possible to reduce the distortion and brightness unevenness of the virtual image V visually confirmed by the user 22, and the design of the optical system 10 becomes easier.

[0138] The display device 1A may be provided with the optical element 9 in the same manner as the display device 1. In this case, the display device 1A can enable the user 22 to visually confirm the stereoscopic image. The optical element 9 may be located between the display panel 2 and the first semi-transmissive mirror 11, may be located at the rear stage of the polarizing plate 15 in the emission direction of the display light, or may be located between the first semi-transmissive mirror 11 and the first phase difference plate 12.

[0139] Next, other examples of the display device 1A will be described. In the display device 1A' of this example, the structure (shape) of the second semi-transmissive mirror is different from that of the above-described display device 1A. For other structures, since they are the same structures, the same reference numerals are assigned to the same structures, and detailed descriptions are omitted.

[0140] The display device 1A' of this example is as Figure 5 shown and includes a display panel 2 and an optical system 10. The optical system 10 is configured to include a first semi-transmissive mirror 11, a first phase difference plate 12, a second semi-transmissive mirror 13', a second phase difference plate 14, and a polarizing plate 15. The first semi-transmissive mirror 11, the first phase difference plate 12, the second semi-transmissive mirror 13', the second phase difference plate 14, and the polarizing plate 15 are arranged in sequence in the emission direction of the display light from the display panel 2.

[0141] The second semi-transmissive mirror 13' has a convex reflecting surface 13'a, and the reflecting surface 13'a faces the first phase difference plate 12. The second semi-transmissive mirror 13' is also referred to as a convex semi-lens. The second semi-transmissive mirror 13' can transmit a part of the incident light (for example, approximately 50%) and reflect the remaining part (for example, approximately 50%).

[0142] The second semi-transmissive mirror 13' may be configured to include, for example, a substrate and a semi-transmissive reflection layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be made of, for example, inorganic glass, resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transmissive reflection layer may be a metal thin film. The metal thin film may be made of, for example, metal materials such as aluminum and chromium. The semi-transmissive reflection layer is not limited to a metal thin film, and may also be, for example, an electrolyte multilayer film, etc.

[0143] The optical system 10 may be configured such that the focal length of the second semi-transmissive mirror 13' is larger than the distance between the display panel 2 and the second semi-transmissive mirror 13'. In other words, the optical system 10 may be configured to project a reduced virtual image Q' of the object (i.e., the display surface 2a) by the second semi-transmissive mirror 13' (refer to Figure 7). Further, the optical system 10 can be configured such that the focal length of the first half mirror 11 is larger than the distance between the virtual image Q' and the first half mirror 11. In other words, the optical system 10 can be configured to project an enlarged virtual image V of the object (i.e., the virtual image Q') onto the first half mirror 11. In this case, it is possible to adjust the magnification and the projection distance of the virtual image V while reducing the thickness of the optical system 10 in the depth direction (Z-axis direction).

[0144] The first half mirror 11, the first retardation plate 12, the second half mirror 13', the second retardation plate 14, and the polarizing plate 15 are held in a holding member (not shown) to maintain their relative positions. Air is interposed between the first half mirror 11 and the first retardation plate 12. Since the display device 1A' is configured such that no member made of a resin material such as a polymer is provided between the first half mirror 11 and the first retardation plate 12, it is possible to reduce the possibility of deformation of the first half mirror 11 and positional deviation between the first half mirror 11 and the first retardation plate 12 when the resin material is hardened during the manufacturing process of the display device 1A'. As a result, it is possible to reduce the degradation of the display quality.

[0145] Since the optical system 10 is a single-axis (coaxial) optical system in which the optical axis of the incident light substantially coincides with the optical axis of the emitted light, it is possible to reduce the occupied space of the optical system 10. As a result, it is possible to miniaturize the display device 1A'. In addition, since the optical system 10 is a single-axis type, it is possible to reduce the distortion and brightness unevenness of the virtual image V visually confirmed by the user 22, and the design of the optical system 10 becomes easier.

[0146] The display device 1A' may also include an optical element 9. In this case, the user 22 can visually confirm the stereoscopic virtual image V.

[0147] In addition, according to the display device 1A' of this example, it is possible to make the optical system 10 thinner in the depth direction (Z-axis direction), and thus it is possible to provide a thin display device. Hereinafter, with reference to Figure 6 、 7The thinning of the optical system 10 will be described. It should be noted that, since the reflecting surface of the first half-transmissive mirror 11 of the display devices 1A and 1A' that reflects and emits the display light to the outside is a concave reflecting surface 11a, hereinafter, the first half-transmissive mirror 11 may sometimes be referred to as a concave mirror. The reflecting surface of the second half-transmissive mirror 13 of the display device 1A that reflects and emits the display light to the outside is a planar reflecting surface 13a, and thus, hereinafter, the second half-transmissive mirror 13 may sometimes be referred to as a plane mirror. The reflecting surface of the second half-transmissive mirror 13' of the display device 1A' that reflects and emits the display light to the outside is a convex reflecting surface 13'a, and thus, hereinafter, the second half-transmissive mirror 13' may sometimes be referred to as a convex mirror. In addition, the dimension of the optical system 10 in the depth direction (Z-axis direction) may sometimes be referred to as the thickness of the optical system 10.

[0148] Figure 6 FIG. is for explaining the projection of the virtual image V in the display device 1A. In Figure 6 , the illuminator 4 and the optical members (the first retardation plate 12, the second retardation plate 14, and the polarizing plate 15) that do not contribute to the projection distance (virtual image distance) and magnification of the virtual image V are omitted. In addition, the concave mirror 11 is arranged in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be regarded as "0". In the following description, the focal length of the concave mirror 11 is set to f, and the distance between the concave mirror 11 and the plane mirror 13 is set to a / 2. The distance a / 2 corresponds to the thickness of the optical system 10 of the display device 1A.

[0149] The display device 1A is configured to magnify the virtual image Q of the display surface 2a formed by the plane mirror 13 using the concave mirror 11 and project it as the virtual image V. As Figure 6 shown, the virtual image Q is located on the opposite side of the concave mirror 11 with respect to the plane mirror 13, and the distance from the plane mirror 13 is a / 2. The virtual image Q becomes an image that magnifies the display surface 2a equally (1 time).

[0150] The virtual image distance b and the virtual image magnification m of the virtual image V are respectively represented by the following equations (1) and (2). It should be noted that 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.

[0151] b = 1 / (1 / a - 1 / f) (1)

[0152] m = b / a (2)

[0153]

Table 1

[0154]

[0155] Table 1 shows Structural Examples 1 and 2 of the display device 1A. The units of the focal length f, the thickness a / 2, and the virtual image distance b shown in Table 1 are "mm". Structural Examples 1 and 2 are configured such that the virtual image distance b is set to 200 mm and the virtual image magnification m is set to 2 or 3. As shown in Table 1, when the optical system 10 includes the plane mirror 13, in order to set the virtual image distance b to 200 mm and the virtual image magnification m to 2, it is necessary to set the thickness a / 2 of the optical system 10 to 50 mm (see Structural Example 1), and in order to set the virtual image distance b to 200 mm and the virtual image magnification m to 3, it is necessary to set the thickness a / 2 of the optical system 10 to 33.5 mm (see Structural Example 2).

[0156] Figure 7 This is a diagram for explaining the projection of the virtual image V in the display device 1A'. In Figure 7 it, the illuminator 4 and the optical members (the first retardation plate 12, the second retardation plate 14, and the polarizing plate 15) that do not contribute to the projection distance (virtual image distance) and magnification of the virtual image V are omitted. In addition, the concave mirror 11 is arranged in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be regarded as "0". In the following description, the focal length of the convex mirror 13' is set to f', the focal length of the concave mirror 11 is set to f'', and the distance between the concave mirror 11 and the convex mirror 13' is set to a' / 2. The distance a' / 2 corresponds to the thickness of the optical system 10 of the display device 1A'.

[0157] The display device 1A' is configured to magnify the virtual image Q' of the display surface 2a formed by the convex mirror 13' using the concave mirror 11 and project it as the virtual image V. As Figure 7 shown, 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' of the virtual image Q' from 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). From formula (3), it is clear that b' < a' / 2, so 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.

[0158] b' = 1 / {1 / f' + 1 / (a' / 2)} (3)

[0159] m' = b' / (a' / 2) (4)

[0160] 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. It should be noted that 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.

[0161] b’’ = 1 / {1 / (a’ / 2 + b’) - 1 / f’’} (5)

[0162] m’’ = (b’ / (a’ / 2)) × b’’ / (a’ / 2 + b’) (6)

[0163] Table 2 shows Structural Examples 3 and 4 of the display device 1A’. The units of the focal lengths f’, f’’, the thickness a’ / 2, and the virtual image distance b’’ shown in Table 2 are “mm”. Similar to Structural Examples 1 and 2, Structural Examples 3 and 4 are configured such that the virtual image distance b’’ is set to 200 mm and the virtual image magnification m’’ is set to 2 or 3. As shown in Table 2, when the optical system 10 includes the convex mirror 13’, with the optical system 10 having a thickness a’ / 2 of 32 mm, the virtual image distance b’’ can be set to 200 mm and the virtual image magnification m’’ can be set to 2, similar to Structural Example 1 (see Structural Example 3). With the optical system 10 having a thickness a’ / 2 of 25.5 mm, the virtual image distance b’’ can be set to 200 mm and the virtual image magnification m’’ can be set to 3, similar to Structural Example 2 (see Structural 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.

[0164]

Table 2

[0165]

[0166] The display device 1A’ can design the optical system 10 to achieve the values of the virtual image distance b’’, the virtual image magnification m’’, and the thickness a’ / 2 when each of them is given.

[0167] Hereinafter, with reference to Figure 8 the design of the optical system 10 of the display device 1A’ will be described. In Figure 8 it, similar to Figure 7 the illuminator 4, the first retardation plate 12, the second retardation plate 14, and the polarizing plate 15 are omitted. In addition, the concave mirror 11 is arranged in contact with the display panel 2 so that the distance between the display panel 2 and the concave mirror 11 can be regarded as “0”. In the following description, the thickness of the optical system 10 is set as a1, the distance between the convex mirror 13’ and the virtual image Q’ is set as b1, and the distance between the concave mirror 11 and the virtual image V is set as b2. In addition, the magnification of the virtual image Q’ with respect to the display surface 2a is set as m1, and the magnification of the virtual image V with respect to the virtual image Q’ is set as m2. And the focal length of the convex mirror 13’ is set as f1, and the focal length of the concave mirror 11 is set as f2.

[0168] The magnification M of the virtual image V with respect to the display surface 2a is expressed as the product of the magnification m1 and the magnification m2 as shown in the following formula (7). Further, 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 formula (8).

[0169] M = m1 × m2 (7)

[0170] a2 = a1 + b1 (8)

[0171] When the thickness a1 of the optical system 10 is defined as T and the virtual image distance (i.e., 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 formula (9).

[0172] M = m1 × m2

[0173] = (b1 / a1) × (b2 / a2)

[0174] = (b1 / T) × (D / a2) (9)

[0175] Substituting the following formula (10) that holds for the distance b1 between the convex mirror 13' and the virtual image Q' into formula (9) results in the following formula (11).

[0176] 1 / a1 = 1 / b1 + 1 / f1 (10)

[0177] M = f1 × (1 + D / f2) / (T + f1) (11)

[0178] Further, substituting the following formula (12) that holds for the distance b2 between the concave mirror 11 and the virtual image V into formula (8) results in the following formula (13).

[0179] 1 / a2 = 1 / b2 + 1 / f2 (12)

[0180] D × f2 / (D + f2) = T + T × f1 / (T + f1) (13)

[0181] Based on formula (9) and formula (13), the focal length f1 of the convex mirror 13' and the focal length f2 of the concave mirror 11 are obtained as shown in the following formula (14) and formula (15). It should be noted that A in formula (15) is expressed by the following formula (16).

[0182] f1 = M × T × T / (D - 2 × M × T) (14)

[0183] f2 = D × A / (M - A) (15)

[0184] A = f1 / (T + f1) (16)

[0185] As can be seen from the above calculations, when the display device 1A' is given the values of the magnification ratio M, the thickness T, and the virtual image distance D respectively, it can determine the focal lengths f1 and f2 (i.e., design the optical system 10) to achieve them.

[0186] The display devices 1A and 1A' can make the optical path length of the light that exits from the display panel 2, transmits through the first half-transmissive mirror 11, is reflected by the second half-transmissive mirrors 13 and 13', and reaches the first half-transmissive mirror 11 smaller than the focal length of the first half-transmissive mirror 11. In this case, the user 22 can visually confirm the virtual image V. The display devices 1A and 1A' can make the optical path length of the light that exits from the display panel 2, transmits through the first half-transmissive mirror 11, is reflected by the second half-transmissive mirrors 13 and 13', and reaches the first half-transmissive mirror 11 larger than the focal length of the first half-transmissive mirror 11. In this case, the user 22 can visually confirm the real image.

[0187] Next, a display device according to another embodiment of the present invention will be described. The display device of this embodiment has a different optical system structure from the display device of the above embodiment. For other structures, since they are the same, the same reference numerals are assigned to the same structures, and detailed descriptions are omitted.

[0188] The display device 1B of this embodiment is as Figure 9 shown and includes a display panel 2 and an optical system 16.

[0189] The optical system 16 includes a first half-transmissive mirror 17, a first retardation plate 18, a second half-transmissive mirror 19, a second retardation plate 20, and a third half-transmissive mirror 21. The first half-transmissive mirror 17, the first retardation plate 18, the second half-transmissive mirror 19, the second retardation plate 20, and the third half-transmissive mirror 21 are arranged in sequence in the emission direction of the display light from the display panel 2.

[0190] The first retardation plate 18 is arranged opposite to the reflection surface 17a of the first half-transmissive mirror 17. The first retardation plate 18 is arranged at a distance from the display surface 2a in the emission direction of the display light from the display panel 2. The second retardation plate 20 is arranged at a distance 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.

[0191] The first half-transmissive mirror 17 is located between the display panel 2 and the first retardation plate 18. The first half-transmissive mirror 17 can transmit a part of the incident light and reflect the remaining part. In this embodiment, the first half-transmissive mirror 17 can also be configured to transmit the S-wave polarized light and reflect the P-wave polarized light. The first half-transmissive mirror 17 can also be as Figure 9As shown, it is a concave mirror having a concave reflecting surface 17a opposed to the first retardation plate 18. The first semi-transmissive mirror 17 may include a spherical shape, an aspherical shape, or a free-form surface shape in at least a part of the reflecting surface 17a.

[0192] The first semi-transmissive mirror 17 is configured to include, for example, a substrate and a plurality of metal thin wires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be made of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal thin wires may be made of metal materials such as aluminum, chromium, titanium oxide, etc. The metal thin wires may be arranged in one direction. The first semi-transmissive mirror 17 can transmit the light component vibrating in the direction orthogonal to the wire grid and can reflect the light component vibrating in the direction parallel to the wire grid. The metal nanowire grid may be formed on the surface of the substrate opposed to the first retardation plate 18. It should be noted that in this example, the first semi-transmissive mirror 11 is given the function of reflecting polarized light by using the metal nanowire grid, but the first semi-transmissive mirror 11 may also be set as a simple semi-lens, and a reflective polarizing plate may be provided separately.

[0193] The second semi-transmissive mirror 19 is located between the first retardation plate 18 and the second retardation plate 20. The second semi-transmissive mirror 13 can transmit a part (e.g., approximately 50%) of the incident light and reflect the remaining part (e.g., approximately 50%). The second semi-transmissive mirror 19 may be Figure 9 As shown, it is a plane mirror having a reflecting surface 19a opposed to the first retardation plate 18 and a reflecting surface 19b opposed to the second retardation plate 20. The second semi-transmissive mirror 19 is also called a plane semi-lens. The second semi-transmissive mirror 19 may also be Figure 32 As shown, integrated with the first retardation plate 18 and / or the second retardation plate 20.

[0194] The second semi-transmissive mirror 19 may be configured to include, for example, a substrate and a semi-transmissive layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The semi-transmissive layer may be a metal thin film. The metal thin film may be made of metal materials such as aluminum, chromium, etc. The semi-transmissive layer is not limited to the metal thin film, and may also be, for example, an electrolyte multilayer film, etc. The first retardation plate 18 and the second retardation plate 20 may be fixed to the second semi-transmissive mirror 19 by using an optically transparent adhesive such as OCA (Optically Clear Adhesive). The adhesive may also be a material with a small retardation.

[0195] The third half-transmissive mirror 21 is disposed to face the side opposite to the surface of the second retardation plate 20 that faces the second half-transmissive mirror 19. The third half-transmissive mirror 21 is located in the rear stage of the second retardation plate 20 in the emission direction of the display light from the display panel 2. The third half-transmissive mirror 21 can transmit a part of the incident light and reflect the remaining part. In the present embodiment, the third half-transmissive mirror 21 may also be configured to reflect the light of the S-wave polarization and transmit the light of the P-wave polarization. The third half-transmissive mirror 21 can be, as Figure 9 shown, a concave mirror having a concave reflecting surface 21a facing the second retardation plate 20. The third half-transmissive mirror 21 may include a spherical shape, an aspherical shape, or a free-form surface shape at at least a part of the reflecting surface 21a.

[0196] The third half-transmissive mirror 21 is configured to include, for example, a substrate and a plurality of metal thin wires (metal nanowire grid) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to the light in the visible light band. The substrate may be made of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal thin wires may be made of a metal material such as aluminum, chromium, titanium oxide, etc. The metal thin wires may be arranged in one direction. The third half-transmissive mirror 21 can transmit the light component vibrating in the direction orthogonal to the wire grid and can reflect the light component vibrating in the direction parallel to the wire grid. The metal nanowire grid may be formed on the surface of the substrate that faces the second retardation plate 20. It should be noted that, in this example, the function of reflecting polarized light is given to the third half-transmissive mirror 21 by using the metal nanowire grid, but the third half-transmissive mirror 21 may also be a simple half-lens, and a reflective polarizing plate may be provided separately.

[0197] The optical function of the optical system 16 will be described. In the display device 1B, the display light emitted from the display panel 2 can travel along path P1 or path P2 and be emitted to the outside. First, the light traveling along path P1 will be described. The display light of the S-wave polarized light (the first linearly polarized light L1) emitted from the display panel 2 passes through the first half-transmissive mirror 17. The light of the first linearly polarized light L1 passes through the first retardation plate 18 and is transformed into the light of the first circularly polarized light C1. The light of the first circularly polarized light C1 is incident on the second half-transmissive mirror 19. A part (for example, approximately 50%) of the light of the first circularly polarized light C1 is reflected by the second half-transmissive mirror 19 and is transformed into the light of the second circularly polarized light C2. The light of the second circularly polarized light C2 passes through the first retardation plate 18 and is transformed into the light of the second linearly polarized light L2 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (that is, it is P-wave polarized light). The light of the second linearly polarized light L2 is reflected by the first half-transmissive mirror 17 and is transformed into the light of the third linearly polarized light L3 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (that is, it is P-wave polarized light). The third linearly polarized light L3 passes through the first retardation plate 18 and is transformed into the light of the third circularly polarized light C3. The light of the third circularly polarized light C3 is incident on the second half-transmissive mirror 19. A part (for example, approximately 50%) of the light of the third circularly polarized light C3 passes through the second half-transmissive mirror 19. The light of the third circularly polarized light C3 that has passed through the second half-transmissive mirror 19 passes through the second retardation plate 20 and is transformed into the light of the fourth linearly polarized light L4 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (that is, it is P-wave polarized light). The light of the fourth linearly polarized light L4 passes through the third half-transmissive mirror 21 and is emitted to the outside.

[0198] Next, the light traveling along path P2 will be described. The remaining part (for example, approximately 50%) of the light of the first circularly polarized light C1 incident on the second half-transmissive mirror 19 passes through the second half-transmissive mirror 19. The light of the first circularly polarized light C1 that has passed through the second half-transmissive mirror 19 passes through the second retardation plate 20 and is transformed into the light of the fifth linearly polarized light L5 whose polarization direction is parallel to that of the first linearly polarized light L1 (that is, it is S-wave polarized light). The light of the fifth linearly polarized light L5 is reflected by the third half-transmissive mirror 21 and is transformed into the light of the sixth linearly polarized light L6 whose polarization direction is parallel to that of the first linearly polarized light L1 (that is, it is S-wave polarized light). The light of the sixth linearly polarized light L6 passes through the second retardation plate 20 and is transformed into the light of the fourth circularly polarized light C4. The light of the fourth circularly polarized light C4 is incident on the second half-transmissive mirror 19. A part (for example, approximately 50%) of the light of the fourth circularly polarized light C4 is reflected by the second half-transmissive mirror 19 and is transformed into the light of the fifth circularly polarized light C5. The light of the fifth circularly polarized light C5 passes through the second retardation plate 20 and is transformed into the light of the seventh linearly polarized light L7 whose polarization direction is orthogonal to that of the first linearly polarized light L1 (that is, it is P-wave polarized light). The light of the seventh linearly polarized light L7 passes through the third half-transmissive mirror 21 and is emitted to the outside.

[0199] As described above, in the display device 1B, the display light emitted from the display panel 2 travels along the path P1 or the 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 becomes, 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 improve the light utilization efficiency and can increase the brightness of the light emitted to the outside.

[0200] It should be noted that in the above, an example in which the first retardation plate 18 and the second retardation plate 20 are quarter-wave plates has been described. However, for the first retardation plate 18 and the second retardation plate 20, as long as a part of the light is reflected by the first half-transmissive mirror 17 and the other light is transmitted through the first half-transmissive mirror 17, they may not be quarter-wave plates but other wave plates or a combination thereof. In addition, for the first retardation plate 18 and the second retardation plate 20, as long as a part of the light is reflected by the third half-transmissive mirror 21 and the other light is transmitted through the third half-transmissive mirror 21, they may not be quarter-wave plates but other wave plates or a combination thereof.

[0201] The first half-transmissive mirror 17, the first retardation plate 18, the second half-transmissive mirror 19, the second retardation plate 20, and the third half-transmissive mirror 21 maintain their relative positions by being held by a holding member (not shown). Air is interposed between the first half-transmissive mirror 17 and the first retardation plate 18 and between the third half-transmissive mirror 21 and the second retardation plate 20. Since the display device 1B has a structure in which no member made of a resin material such as a polymer is provided between the first half-transmissive mirror 17 and the first retardation plate 18 and between the third half-transmissive mirror 21 and the second retardation plate 20, the possibility of deformation of the first half-transmissive mirror 11, positional deviation between the first half-transmissive mirror 11 and the first retardation plate 12, etc. can be reduced. As a result, a decrease in display quality can be reduced.

[0202] Since the optical system 16 is a coaxial type optical system in which the optical axis of the incident light and the optical axis of the emitted light are substantially the same, the occupied space of the optical system 16 can be reduced. As a result, the display device 1B can be miniaturized. In addition, since the optical system 16 is a coaxial type, the distortion, brightness unevenness, etc. of the virtual image V visually confirmed by the user 22 can be reduced, and the design of the optical system 16 becomes easy.

[0203] The display device 1B may have a structure in which the focal length of the first half-transmissive mirror 17 is equal to the focal length of the third half-transmissive mirror 21 and the second half-transmissive mirror 19 is a plane mirror. In this case, in the imaging device including the display device 1B, the virtual image formed by the light traveling along the path P1 and the virtual image formed by the light traveling along the path P2 are substantially the same. Therefore, the display quality can be improved.

[0204] The display device 1B can make the optical path length of the light emitted from the display panel 2, transmitted through the first half mirror 17, reflected by the second half mirror 19, and reaching the first half mirror 17 smaller than the focal length of the first half mirror 17, and make the optical path length of the light emitted from the display panel 2, transmitted through the first half mirror 17, transmitted through the second half mirror 19, and reaching the third half mirror 21 smaller than the focal length of the first half mirror 17. In this case, the user 22 can visually confirm the virtual image V. The display device 1B can also make the optical path length of the light emitted from the display panel 2, transmitted through the first half mirror 17, reflected by the second half mirror 19, and reaching the first half mirror 17 larger than the focal length of the first half mirror 17, and make the optical path length of the light emitted from the display panel 2, transmitted through the first half mirror 17, transmitted through the second half mirror 19, and reaching the third half mirror 21 larger than the focal length of the first half mirror 17. In this case, the user 22 can visually confirm the real image.

[0205] Next, an imaging device according to an embodiment of the present invention will be described. The imaging device 100 of this embodiment includes display devices 1, 1A, 1A', and 1B. The imaging device 100 makes the user 22 visually confirm the display light emitted from the display panel 2 as the virtual image V. Since the imaging device 100 includes the display devices 1, 1A, 1A', and 1B, a compact imaging device can be realized. In addition, the user 22 can visually confirm the 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 can also make the user 22 visually confirm the display light emitted from the display panel 2 as the real image.

[0206] The imaging device 100 can be mounted on the moving body 23 as Figure 10 shown. The moving body 23 can be a vehicle. Figure 10 The case where the vehicle is a passenger car is shown, but the vehicle is not limited to a passenger car and can be a motor vehicle such as a truck, a bus, and a trolleybus. The positions of the display devices 1, 1A, 1A', and 1B are arbitrary inside the moving body 23. The display devices 1, 1A, 1A', and 1B can be located on the front bulkhead (instrument panel), inside the front bulkhead, the ceiling of the passenger compartment, the A-pillar, etc. The imaging device 100 can use a part of its structure as other devices and components provided in the moving body 23.

[0207] The imaging device 100 can be as Figure 10A camera 102 that captures the rear view of the moving body 23 as shown. The camera 102 may include, for example, a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary Metal Oxide Semiconductor) imaging element. The imaging device 100 is connected to the camera 102 through wired communication and / or wireless communication. When the moving body 23 is a vehicle, the imaging device 100 and the camera 102 may be connected via a vehicle network such as CAN (Control Area Network).

[0208] The imaging device 100 may be configured to display at least a part of the captured image captured by the camera 102 on the display panel 2. In this case, the imaging device 100 can visually confirm the rear view of the moving body 23 as a virtual image V imaged on the side farther from the imaging device 100 by the user 22 (the driver of the moving body 23). As a result, the user 22 can visually confirm the rear view of the moving body 23 without significantly changing the viewing distance (fixation point) during the driving of the moving body 23. Therefore, it is easy to visually confirm the virtual image V, and the driving safety can be improved. In addition, since the imaging device 100 is a small-sized imaging device, even if it is arranged in the cab of the moving body 23, it will not occupy a large volume in the cab and is unlikely to interfere with driving. The imaging device 100 mounted on the moving body 23 and configured to visually confirm the rear view of the moving body 23 as a virtual image V by the user 22 is also called a digital in-vehicle rearview mirror.

[0209] The display devices 1, 1A, 1A', 1B of the imaging device 100 may include an optical element 9 (see Figure 3 ). The imaging device 100 may be configured to display a mixed image including a left-eye image and a right-eye image having parallax with each other on the display panel 2, and emit the display light of the left-eye image and the display light of the right-eye image. The optical element 9 causes the display light of the left-eye image to reach the left eye of the user 22 and the display light of the right-eye image to reach the right eye of the user 22. In this case, the display light of the left-eye image and the display light of the right-eye image emitted from the display panel 2 can be visually confirmed by the user 22 as a stereoscopic virtual image V.

[0210] The imaging device 100 may be as Figure 11It is equipped with a reflective optical element 101 as shown. The imaging device 100 can be configured such that the display devices 1, 1A, 1A', 1B emit display light toward the reflective optical element 101, and the reflective optical element 101 causes a part of the display light to reach the eyes of the user 22. When the imaging device 100 is mounted on the moving body 23, the imaging device 100 can use the windshield 24 of the moving body 23 as the reflective optical element 101.

[0211] The imaging device 100 can also be applied to a digital side mirror. In this case, the imaging device 100 can be as Figure 12 shown, and include display devices 1, 1A, 1A', 1B (hereinafter also referred to as the left display device 1L) located on the A-pillar on the left side of the moving body 23, a camera 102 (hereinafter also referred to as the left camera 102L) that captures the left rear of the moving body 23, display devices 1, 1A, 1A', 1B (hereinafter also referred to as the right display device 1R) located on the A-pillar on the right side of the moving body 23, and a camera 102 (hereinafter also referred to as the right camera 102R) that captures the right rear of the moving body 23. The left display device 1L can visually confirm an image of the left rear of the moving body 23 captured by the left camera 102L as a virtual image V (hereinafter also referred to as the virtual image V2) for the user 22. The right display device 1R can visually confirm an image of the right rear of the moving body 23 captured by the right camera 102R as a virtual image V (hereinafter also referred to as the virtual image V3) for the user 22. It should be noted that the image can be a moving image (also referred to as a video) or a still image. The left camera 102L can be located at the same position as the left door mirror, and the right camera 102R can be located at the same position as the right door mirror.

[0212] The imaging device 100 can also be structured such that the distances between the eyes (or eye box) of the user 22 and the virtual images V2 and V3 are substantially the same. In this case, the user 22 can confirm the conditions of the left rear and the right rear of the moving body 23 without significantly changing the fixation distance (the distance between the eyes of the user 22 and the fixation point that the user 22 is looking at). Therefore, driving safety can be improved. It should be noted that the eye box refers to the region in the actual space where the eyes of the user 22 are assumed to exist.

[0213] The imaging device 100 can be structured such that the distances between the eyes (or eye box) of the user 22 and the virtual images V1 to V3 are substantially the same. In this case, the user 22 can confirm the conditions of the directly rear, the left rear, and the right rear of the moving body 23 without significantly changing the fixation distance. Therefore, driving safety can be improved.

[0214] The imaging device 100 can also be applied to a cluster 29 within the front bulkhead of the moving body 23 (refer to Figure 12 ). In this case, the display devices 1, 1A, 1A', 1B can also visually confirm for the user 22 an image representing information related to driving, such as vehicle speed, engine rotational speed, fuel level, etc., as a virtual image V (hereinafter, also referred to as virtual image V4).

[0215] The imaging device 100 can also be applied to a CID (Center Information Display) 30 (refer to Figure 12 ). In this case, the display devices 1, 1A, 1A', 1B can be arranged in the center cluster of the moving body 23 and visually confirm for the user 22 an image representing information related to navigation, in-vehicle environment (such as settings of an air conditioning device, an audio device, etc.), etc., as a virtual image V (hereinafter, also referred to as virtual image V5).

[0216] The imaging device 100 can also be structured such that the distances between the eyes (or eye movement range) of the user 22 and the virtual images V4 and V5 are substantially the same. In this case, the user 22 can confirm information related to the driving of the moving body 23 and information related to navigation, in-vehicle environment, etc. without significantly changing the fixation distance. Therefore, the driving safety can be improved.

[0217] The imaging device 100 can be structured such that the distances between the eyes (or eye movement range) of the user 22 and the virtual images V1 to V5 are substantially the same. In this case, the user 22 can confirm the directly rear, left rear, and right rear of the moving body 23 without significantly changing the fixation distance, and can also confirm information related to the driving, navigation, in-vehicle environment, etc. of the moving body 23. Therefore, the driving safety can be improved.

[0218] The imaging device 100 can also be applied to a PID (Passenger Information Display) 31 (refer to Figure 12 ). In this case, the display devices 1, 1A, 1A', 1B can be arranged near the front passenger seat in the front bulkhead and visually confirm for the co-passengers an image of an entertainment item and an image representing information related to an audio device, an air conditioning device, etc., as a virtual image V.

[0219] The imaging device 100 can also be applied to an RSE (Rear Seat Entertainment) system 32 (refer to Figure 10). In this case, the display devices 1, 1A, 1A', 1B can be arranged on the back of the front seats, and the entertainment item images and the images representing information related to the audio device, air conditioning device, etc. are presented as virtual images V for the passengers sitting in the rear seats of the moving body 23 to visually confirm.

[0220] The display devices 1, 1A, 1A', 1B can be provided with a drive unit for adjusting the relative positions between the display panel 2, the semi-transmissive mirror 6, the first semi-transmissive mirrors 11, 17, and the second semi-transmissive mirrors 13, 13', 21 in the depth direction. The image data of the display image displayed on the display panel 2 can include depth information indicating the depth (distance in the depth direction) from the reference position. The reference position can be, for example, the position of the display panel 2. The virtual image display device 100 can be configured to adjust the distances between the display panel 2, the semi-transmissive mirror 6, the first semi-transmissive mirrors 11, 17, and the second semi-transmissive mirrors 13, 13', 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 can be composed of, for example, an electric slider, an electric actuator, etc. The drive unit can also be configured such that the user 22 can manually adjust the relative positions between the display panel 2, the semi-transmissive mirror 6, the first semi-transmissive mirrors 11, 17, and the second semi-transmissive mirrors 13, 13', 21.

[0221] Hereinafter, other examples of the display device of the present invention will be described.

[0222] First, other examples of the display devices 1, 1A, 1A', 1B will be described. Figure 13 、 14 is a top view showing other examples of the display device of the present invention. It should be noted that in Figure 13 、 14 the first retardation plate 5, the second retardation plate 7, and the optical element 9 are omitted. Hereinafter, the display device 1 will be taken as an example for description, but the same applies to the display devices 1A, 1A', 1B.

[0223] The display device 1 can form a part of the imaging device 100 (digital in-vehicle rearview mirror). In a normal in-vehicle rearview mirror, that is, an in-vehicle rearview mirror using a mirror, the image visually confirmed by the user's left eye (also called the left-eye image) is different from the image visually confirmed by the right eye (also called the right-eye image), and the user recognizes the left-eye image and the right-eye image as a mirror image visually confirmed by both eyes through the cognitive function of the brain.

[0224] The display device 1 can be configured such that the virtual image projected within the field of view of the user 22 has a binocular visible area visually confirmed by the user 22's left eye 22L and right eye 22R ( Figure 13 、 14a virtual image V), a left-eye visible region VLa that can only be visually confirmed by the left eye 22L, and a right-eye visible region VRa that can only be visually confirmed by the right eye 22R. In other words, it can be that when the virtual image visually confirmed by the left eye 22L is set as the left-eye virtual image VL and the virtual image visually confirmed by the right eye 22R is set as the right-eye virtual image VR, the left-eye virtual image VL has a left-eye visible region VLa that can only be visually confirmed by the left eye 22L, and the right-eye virtual image VR has a right-eye visible region VRa that can only be visually confirmed by the right eye 22R. Within the field of view of the user 22, the left-eye visible region VLa is located to the right of the binocular visible region, and the right-eye visible region VRa is located to the left of the binocular visible region. In addition, the display device 1 can be as Figure 13 shown, the right end 6R of the semi-transmissive mirror 6 that can be visually confirmed by the user 22 is located on the 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-transmissive mirror 6 that can be visually confirmed by the user 22 is located on the straight line connecting the right eye 22R and the left end VRL of the right-eye virtual image VR.

[0225] According to such a structure, similar to the left-eye image and the right-eye image in a normal in-vehicle rearview mirror, the range observed by the user 22 through the left-eye virtual image VL is different from the range observed by the user 22 through the right-eye virtual image VR. Therefore, the user 22 can, in the same way as when using a normal in-vehicle rearview mirror, through the cognitive function of the brain, recognize the left-eye virtual image VL and the right-eye virtual image VR as the virtual image V visually confirmed by both eyes 22L and 22R. Therefore, the possibility of causing discomfort to the user 22 can be reduced.

[0226] The size of the reflection surface on the display surface 2a side of the reflective polarizing plate 8 of the display device 1 can be equal to or larger than the size of the display surface 2a. In this case, the reflective polarizing plate 8 can reflect the image of the entire display surface 2a toward the semi-transmissive mirror 6. In addition, the display device 1 can be configured such that the virtual image (hereinafter, also referred to as the display surface virtual image) VD when the image of the entire display surface 2a is projected within the field of view of the user 22 includes the left-eye virtual image VL and the right-eye virtual image VR. In this case, it is possible to form a region R that appears in the fields of view of the left eye 22L and the right eye 22R when the head of the user 22 moves, that is, a glimpse region R that can be glimpsed by the left eye 22L or the right eye 22R. As a result, the user 22 can, in the same way as when using a normal in-vehicle rearview mirror, visually confirm the left-eye virtual image VL and the right-eye virtual image VR that change corresponding to the movement of the head. Therefore, the possibility of causing discomfort to the user 22 can be reduced. The size (dimension) of the glimpse region R can be controlled, for example, by controlling the size of the display surface 2a, the magnification of the virtual image, etc.

[0227] It is also possible to control the size of the peeping region R by controlling the image display region A (the region where the image is actually displayed) in the display surface 2a. When the image display region A is increased, the peeping region R can be enlarged. When the image display region A is decreased, the peeping region R can be reduced. When the image display region A is smaller than a specified threshold region, the peeping region R disappears, and the left-eye virtual image VL and the right-eye virtual image VR can be made the same virtual image.

[0228] 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 of 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 peeping region R can also be controlled by the size of the opening 28. As Figure 14 shown, by appropriately designing the size of the opening 28, it is possible to form a left-eye virtual image VL including a region that cannot be visually confirmed by the right eye 22R and a right-eye virtual image VR including a region that cannot be visually confirmed by the left eye 22L. In addition, by appropriately designing the size of the opening 28, it is possible to form the peeping region R and control the size of the peeping region R. In the case of controlling the size of the peeping region R by the opening 28, the size of the half-transmissive mirror 6 may be such that the image of the entire display surface 2a can be projected onto the field of view of the user 22, so the design of the optical system 3 becomes easier.

[0229] The same applies to the display devices 1A, 1A', and 1B. The display devices 1A, 1A', and 1B may be configured such that the virtual image projected within the field of view of the user 22 has a binocular visible region that can be visually confirmed by the left eye 22L and the right eye 22R, a left-eye visible region that can be visually confirmed only by the left eye 22L, and a right-eye visible region that can be visually confirmed only by the right eye 22R. In this case, the possibility of causing discomfort to the user 22 can be reduced. The display devices 1A, 1A' may be configured such that the right end of the first half-transmissive mirror 11 that can be visually confirmed by the user 22 is located on the straight line connecting the left eye 22L and the right end of the left-eye virtual image, and the left end of the first half-transmissive mirror 11 that can be visually confirmed by the user 22 is located on the straight line connecting the right eye 22R and the left end of the right-eye virtual image. The display device 1B may be configured such that the right end of the first half-transmissive mirror 17 and the third half-transmissive mirror 21 that can be visually confirmed by the user 22 is located on the straight line connecting the left eye 22L and the right end of the left-eye virtual image, and the left end of the first half-transmissive mirror 17 and the third half-transmissive mirror 21 that can be visually confirmed by the user 22 is located on the straight line connecting the right eye 22R and the left end of the right-eye virtual image. The display devices 1A, 1A', and 1B may be configured to have a peeping region R. The display devices 1A, 1A', and 1B may be structured to control the size of the peeping region R through the image display region A, or may be structured to control the size of the peeping region R through the opening 28 of the housing 27.

[0230] Next, other examples of the display devices 1, 1A, and 1A' will be described. Figure 15 , 16 is a cross-sectional view for explaining other examples of the display device, Figures 17A to 17D 18A to 18D are diagrams for explaining the optical system in other examples of the display device, Figure 19 is a diagram for explaining the optical system in other examples of the display device. Hereinafter, the display device 1 will be taken as an example for explanation, but the same applies to the display devices 1A and 1A'.

[0231] The display device 1 is configured such that when the user 22 is located in front of the display device 1, the light of the second linearly polarized light L2 is reflected by the reflective polarizing plate 8 and does not exit from the display device 1 (refer to Figure 2 , 3 ). In other words, the display device 1 is configured such that when viewed from the front of the display device 1, the transmission axis of the polarizing plate on the front side (user 22 side) of the display panel 2 (liquid crystal panel) is orthogonal to the transmission axis of the reflective polarizing plate 8 (in a crossed Nicol configuration). Thus, as shown in Figure 2 , 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 visually confirm the display panel 2, but visually confirms the reflected image reflected by the half mirror 6 as a virtual image V.

[0232] When the user 22 is not located in front of the display device 1, the crossed Nicol configuration of the transmission axis of the polarizing plate on the front side of the display panel 2 and the transmission axis of the reflective polarizing plate 8 is disrupted, and sometimes a part of the light of the second linearly polarized light L2 is transmitted through the reflective polarizing plate 8. As a result, sometimes the user 22 can visually confirm both the real image when directly viewing the display panel 2 and the virtual image V reflected by the half mirror 6, and the display quality of the display device 1 is reduced.

[0233] The display device 1 in this example has a third retardation plate 25 located between the display panel 2 and the reflective polarizing plate 8 as shown in Figure 15 , 16 . Thus, even when the user 22 is not located in front of the display device 1, it is possible to make the relative angle between the transmission axis of the polarizing plate on the front side of the display panel 2 and the transmission axis of the reflective polarizing plate 8 close to the crossed Nicol configuration, and it is possible to reduce the reduction in the display quality of the display device 1. The third retardation plate 25 can be a 1 / 2 wave plate (half wave plate), 1 / 4 wave plate, 1 / 8 wave plate, 1 / 16 wave plate, etc., or a wave plate that imparts other phase differences. The optical axis of the third retardation plate 25 can be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizing plate 8.

[0234] The display device 1 in this example can be asFigure 15 , 16 As shown, there is also a fourth retardation plate 26 located between the display panel 2 and the reflective polarizing plate 8. In this case, even when the user 22 is not located directly in front of the display device 1, the relative angle between the transmission axis of the front polarizing plate of the display panel 2 and the transmission axis of the reflective polarizing plate 8 can be made closer to the crossed Nicol configuration, and the degradation of the display quality of the display device 1 can be further reduced. The fourth retardation plate 26 can be a 1 / 2 wave plate (half wave plate), a 1 / 4 wave plate, a 1 / 8 wave plate, a 1 / 16 wave plate, etc., or a wave plate that gives other phase differences. The optical axis of the fourth retardation plate 26 can be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizing plate 8.

[0235] It is sufficient that the third retardation plate 25 and the fourth retardation plate 26 are located between the display panel 2 and the reflective polarizing plate 8, and their positions are arbitrary. When no other optical elements are arranged between the third retardation plate 25 and the fourth retardation plate 26, the third retardation plate 25 and the fourth retardation plate 26 can be in contact with each other. In this case, the thickness in the depth direction of the optical system 3 can be reduced.

[0236] One of the third retardation plate 25 and the fourth retardation plate 26 can be a 1 / 4 wave plate and the other can be a half wave plate. In this case, the degradation of the display quality of the display device 1 can be effectively reduced. Both the third retardation plate 25 and the fourth retardation plate 26 can be half wave plates. In this case, the degradation of the display quality of the display device 1 can be more effectively reduced.

[0237] Figure 17A , 17B , 17C, 17D are Poincaré spheres showing the optical functions (the influence on the polarization state of light) of the third retardation plate 25 and the fourth retardation plate 26 when they are half wave plates. Figure 17A , 17B is a diagram for explaining the optical function of the third retardation plate 25, Figure 17C , 17D is a diagram for explaining the optical function of the fourth retardation plate 26. Figure 17A , 17C shows a diagram when observing the Poincaré sphere from the north pole (S3 axis direction), Figure 17B , 17D shows a diagram when observing the Poincaré sphere from the side (S1 axis direction). In Figure 17A , 17B , 17C, 17D, S LCD shows the polarization state of the light just after it exits from the display panel 2. S 25 shows the polarization state of the light that has passed through the third retardation plate 25, S 26Shows the polarization state of the light that has passed through the fourth retardation plate 26. S 26 It can be said that it shows the polarization state of the light immediately before it enters the reflective polarizing plate 8. S RP Shows the polarization state of the light that transmits through the reflective polarizing plate 8 with a substantially 100% transmittance. S AP Is S RP The antipodal point (the point symmetric about the center of the Poincaré sphere). At S 26 Located at S AP Or located at S AP In the vicinity of, it is possible to reduce the possibility that the light that exits the display panel 2 and has passed through the third retardation plate 25 and the fourth retardation plate 26 transmits through the reflective polarizing plate 8. As a result, it is possible to reduce the possibility that the user 22 visually confirms the real image when directly viewing the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0238] As Figure 17C , 17D Shown, when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates, S 26 Substantially located at S AP . Therefore, it is possible to reduce the possibility that the user 22 visually confirms the real image when directly viewing the display panel 2, and it is possible to reduce the degradation of the display quality of the display device 1.

[0239] Figure 18A , 18B 18C, 18D show the Poincaré sphere of 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. Figure 18A , 18B Is a diagram illustrating the optical function of the third retardation plate 25. Figure 18C , 18D Is a diagram illustrating the optical function of the fourth retardation plate 26. Figure 18A , 18C Shows a diagram when observing the Poincaré sphere from the north pole (S3 axis direction). Figure 18B , 18D Shows a diagram when observing the Poincaré sphere from the side (S1 axis direction). S LCD , S 25 , S 26 , S RP And S AP Are as described above.

[0240] As Figure 18C , 18D Shown, when the third retardation plate 25 is a quarter-wave plate and the fourth retardation plate 26 is a half-wave plate, S 26 Located at S APNearby. Therefore, the possibility of visually recognizing a real image when the user 22 views the direct-view display panel 2 can be reduced, and the degradation of the display quality of the display device 1 can be reduced.

[0241] Figure 19 is a graph showing the relationship between the light transmittance of an optical system in which a third retardation plate 25 and a fourth retardation plate 26 are inserted between polarizing plates 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. Figure 19 Shows the results obtained by simulation. The incident light is green light with a wavelength λ of 550 nm. The polarizing plate PP1, the third retardation plate 25, the fourth retardation plate 26, and the polarizing plate PP2 are arranged in this order in the traveling direction of the incident light. The polarizing plate PP1 is a polarizing plate that simulates the front-side polarizing plate of the display panel 2, and the polarizing plate PP2 is a polarizing plate that simulates the reflective polarizing plate 8.

[0242] Figure 19 The solid line in the graph of shows the transmittance when the retardation of the fourth retardation plate 26 is fixed at 0 nm and the retardation of the third retardation plate 25 is changed, and becomes minimum when the retardation of the third retardation plate 25 is about 275 nm (half of the wavelength λ of the incident light). Figure 19 The dashed line in the graph of shows the transmittance when the retardation of the third retardation plate 25 is fixed at 270 nm and the retardation of the fourth retardation plate 26 is changed, and becomes minimum when the retardation of the fourth retardation plate 26 is about 275 nm (half of the wavelength of the incident light).

[0243] According to Figure 19 the simulation results shown in the graph, it can be seen that in the case where the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates, the display device 1 can effectively reduce the possibility of visually recognizing a real image when the user 22 views the direct-view display panel 2, and can effectively reduce the degradation of the display quality of the display device 1. In addition, it can be seen that even when the retardation of the fourth retardation plate 26 is fixed at 0 nm (that is, in the case where only the third retardation plate 25 is provided), if the third retardation plate 25 gives a non-zero retardation larger than 0 nm to the light incident on the third retardation plate 25, the display device 1 can effectively reduce the possibility of visually recognizing a real image when the user 22 views the direct-view display panel 2, and can effectively reduce the degradation of the display quality of the display device 1.

[0244] The same applies to the display devices 1A and 1A'. The display devices 1A and 1A' may have a third retardation plate 25 located between the display panel 2 and the polarizing plate 15. In this case, the possibility of the user 22 visually confirming the real image when directly viewing the display panel 2 can be reduced, and the degradation of the display quality of the display devices 1A and 1A' can be reduced. The display devices 1A and 1A' may further have a fourth retardation plate 26 located between the display panel 2 and the polarizing plate 15. In this case, the possibility of the user 22 visually confirming the real image when directly viewing the display panel 2 can be further reduced, and the degradation of the display quality of the display devices 1A and 1A' can be further reduced. The third retardation plate 25 and the fourth retardation plate 26 may be a 1 / 2 wave plate (half-wave plate), a 1 / 4 wave plate, a 1 / 8 wave plate, a 1 / 16 wave plate, etc., or may be a wave plate that gives other phase differences. One of the third retardation plate 25 and the fourth retardation plate 26 may be a 1 / 4 wave plate and the other may be a half-wave plate. In this case, the degradation of the display quality of the display device 1 can be effectively reduced. Both the third retardation plate 25 and the fourth retardation plate 26 may be half-wave plates. In this case, the degradation of the display quality of the display device 1 can be more effectively reduced. The third retardation plate 25 and the fourth retardation plate 26 only need to be located between the display panel 2 and the polarizing plate 15, and their positions are arbitrary.

[0245] Next, other examples of the display devices 1, 1A, 1A', and 1B will be described. Figure 20 It is a cross-sectional view showing another example of the display device 1A'. Figure 21 It is a cross-sectional view showing another example of the display device 1A.

[0246] The second half-transmissive mirror 13' of the display device 1A' may also be configured to include a holographic optical element (HOE). In this case, as Figure 20 shown, the optical function of the second half-transmissive mirror 13' can be realized by a flat optical element, and the thickness of the second half-transmissive mirror 13' in the depth direction (Z-axis direction) can be reduced. As a result, the display device 1A' can be miniaturized in the depth direction. And since the second half-transmissive mirror 13' is a flat optical element, the distance between the second half-transmissive mirror 13' and the second retardation plate 14 can be reduced, or the second half-transmissive mirror 13' and the second retardation plate 14 can be brought into contact with each other, so that the display device 1A' can be further miniaturized in the depth direction.

[0247] The first half-transmissive mirror 11 of the display device 1A' may also be configured to include a HOE. In this case, as Figure 20As shown, the optical function of the first half-transmissive mirror 11 can be realized by using a flat optical element, and the thickness of the first half-transmissive mirror 11 in the depth direction can be reduced. As a result, the display device 1A' can be miniaturized in the depth direction. Moreover, since the first half-transmissive mirror 11 is a flat optical element, the distance between the first half-transmissive mirror 11 and the display panel 2 can be reduced, or the first half-transmissive mirror 11 can be in contact with the display panel 2, so that the display device 1A' can be further miniaturized in the depth direction.

[0248] When the first half-transmissive mirror 11 does not have polarization selectivity, the amount of light emitted from the display device 1A' decreases, and the brightness of the virtual image V visually confirmed by the user 22 decreases. Therefore, the first half-transmissive mirror 11 including the HOE can be configured to have polarization selectivity. For example, the first half-transmissive mirror 11 including the HOE can be formed with a plurality of metal thin lines (metal nanowire grids) that achieve polarization selectivity for transmitting S-wave polarized light and reflecting P-wave polarized light on the surface facing the display panel 2 or the surface facing the first retardation plate 12. In this case, the decrease in the brightness of the virtual image V visually confirmed by the user 22 can be reduced.

[0249] The first half-transmissive mirror 11 of the display device 1A can be configured to include the HOE. In this case, as Figure 21 shown, the optical function of the first half-transmissive mirror 11 can be realized by using a flat optical element, and the thickness of the first half-transmissive mirror 11 in the depth direction can be reduced. As a result, the display device 1A can be miniaturized in the depth direction. Moreover, since the first half-transmissive mirror 11 is a flat optical element, the distance between the first half-transmissive mirror 11 and the display panel 2 can be reduced, or the first half-transmissive mirror 11 can be in contact with the display panel 2, so that the display device 1A can be further miniaturized in the depth direction. The first half-transmissive mirror 11 including the HOE can have polarization selectivity. For example, the first half-transmissive mirror 11 including the HOE can be formed with a plurality of metal thin lines that achieve polarization selectivity for transmitting S-wave polarized light and reflecting P-wave polarized light on the surface facing the display panel 2 or the surface facing the first retardation plate 12. In this case, the decrease in the brightness of the virtual image V visually confirmed by the user 22 can be reduced.

[0250] The half-transmissive mirror 6 of the display device 1 can be configured to include a HOE. In this case, the optical function of the half-transmissive mirror 6 can be realized by using a flat optical element, and the thickness of the half-transmissive mirror 6 in the depth direction can be reduced. As a result, the display device 1 can be miniaturized in the depth direction. Further, since the half-transmissive mirror 6 is a flat optical element, the distance between the half-transmissive mirror 6 and the first retardation plate 5 can be reduced, or the half-transmissive mirror 6 and the first retardation plate 5 can be brought into contact with each other, so that the display device 1 can be further miniaturized in the depth direction.

[0251] The first half-transmissive mirror 17 of the display device 1B can be configured to include a HOE. In this case, the optical function of the first half-transmissive mirror 17 can be realized by using a flat optical element, and the thickness of the first half-transmissive mirror 17 in the depth direction can be reduced. As a result, the display device 1B can be miniaturized in the depth direction. Further, since the first half-transmissive mirror 17 is a flat optical element, the distance between the first half-transmissive mirror 17 and the display panel 2 can be reduced, or the first half-transmissive mirror 17 and the display panel 2 can be brought into contact with each other, so that the display device 1B can be further miniaturized in the depth direction. The first half-transmissive mirror 17 including a HOE can have polarization selectivity. For example, the first half-transmissive mirror 17 including a HOE can be formed with a plurality of metal thin lines on the surface facing the display panel 2 or the surface facing the first retardation plate 18 to realize polarization selectivity for transmitting the light of S-wave polarization and reflecting the light of P-wave polarization. In this case, the reduction in the brightness of the virtual image V visually recognized by the user 22 can be reduced.

[0252] The third half-transmissive mirror 21 of the display device 1B can also be configured to include a HOE. In this case, the optical function of the third half-transmissive mirror 21 can be realized by using a flat optical element, and the thickness of the third half-transmissive mirror 21 in the depth direction can be reduced. As a result, the display device 1B can be miniaturized in the depth direction. The third half-transmissive mirror 21 including a HOE can have polarization selectivity. For example, the third half-transmissive mirror 21 including a HOE can be formed with a plurality of metal thin lines on the surface facing the second retardation plate 20 or the surface on the side opposite to the surface facing the second retardation plate 20 to realize polarization selectivity for reflecting the light of S-wave polarization and transmitting the light of P-wave polarization. In this case, the reduction in the quality of the virtual image V visually recognized by the user 22 can be reduced, and further, the reduction in the brightness of the virtual image V can be reduced.

[0253] A holographic optical element can be configured, for example, to have an interference fringe pattern to diffract incident light in a specified direction.

[0254] The display device 1A' can also be configured such that the second half-transmissive mirror 13' includes a Fresnel lens. In this case, as Figure 22As shown, the optical function of the second half-transmissive mirror 13' can be realized by using a substantially flat optical element with a reduced thickness (dimension in the depth direction) compared to a convex half-lens, and the thickness of the second half-transmissive mirror 13' in the depth direction can be reduced. As a result, the display device 1A' can be miniaturized in the depth direction. Further, since the second half-transmissive mirror 13' is substantially flat, the distance between the second half-transmissive mirror 13' and the second retardation plate 14 can be reduced, or the second half-transmissive mirror 13' and the second retardation plate 14 can be made to contact each other, so that the display device 1A' can be further miniaturized in the depth direction. The second half-transmissive mirror 13' including a Fresnel lens is also referred to as a Fresnel half-lens 13'.

[0255] The Fresnel half-lens 13' can be configured as including: Figure 23 as shown, a Fresnel lens (Fresnel convex lens) 33 having a planar first surface 33a facing the second retardation plate 14 and a Fresnel-shaped second surface 33b facing the first retardation plate 12; and a half-transmissive reflective layer 34 located on the second surface 33b. The Fresnel shape has concentric circular 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 can be a curved surface or a flat surface. The half-transmissive reflective layer 34 can be located on the inclined surface of the Fresnel shape. The half-transmissive reflective layer 34 can transmit a part (e.g., approximately 50%) of the incident light and reflect the remaining part (e.g., approximately 50%). The half-transmissive reflective layer 34 can be a metal thin film. The metal thin film can be made of a metal material such as aluminum or chromium, for example. The metal thin film can be formed by a vapor deposition method such as CVD (Chemical Vapor Deposition) method or PVD (Physical Vapor Deposition) method, for example.

[0256] The Fresnel half-lens 13' has an optical function as a lens and an optical function as a half-lens. The optical function as a lens (e.g., focal length, etc.) is determined by the curvature and inclination angle of the inclined surface, the refractive index of the material constituting the Fresnel lens 33, etc. The optical function as a half-lens (e.g., focal length, transmittance, etc.) is determined by the curvature and inclination angle of the inclined surface, the transmittance of the half-transmissive reflective layer 34, etc.

[0257] The Fresnel half-lens 13' can also flatten the surface facing the second retardation plate 14 by using a transparent material layer formed on the second surface 33b of the Fresnel lens 33. The transparent material layer can be made of a material having substantially the same refractive index as the material constituting the Fresnel lens 33. The transparent material layer can be made of the same material as the material constituting the Fresnel lens 33.

[0258] The display device 1A' may also be configured such that the first semi-transmissive mirror 11 includes a Fresnel lens. In this case, as Figure 22 shown, the thickness of the first semi-transmissive mirror 11 can be reduced. As a result, the display device 1A' can be miniaturized in the depth direction. Also, since the first semi-transmissive mirror 11 including the Fresnel lens is substantially flat, the distance between the first semi-transmissive mirror 11 and the display panel 2 can be reduced, or the first semi-transmissive mirror 11 and the display panel 2 can be brought into contact with each other. Therefore, the display device 1A' can be further miniaturized in the depth direction. The first semi-transmissive mirror 11 including the Fresnel lens is also referred to as a Fresnel half mirror 11. The Fresnel half mirror 11 may have the same structure as the Fresnel half mirror 13'. The Fresnel half mirror 11 may also be configured to include a Fresnel concave lens.

[0259] When the first semi-transmissive mirror 11 is replaced with a Fresnel half mirror 11 that does not have polarization selectivity, the amount of light emitted from the display device 1A' decreases, and the brightness of the virtual image V visually confirmed by the user 22 decreases. Therefore, the Fresnel half mirror 11 may be configured to have polarization selectivity. For example, the Fresnel half mirror 11 may be formed with a plurality of metal thin lines (metal nanowire gratings) that achieve polarization selectivity for transmitting S-wave polarized light and reflecting P-wave polarized light on the surface facing the display panel 2 or the surface facing the first retardation plate 12. Thereby, the decrease in the brightness of the virtual image V visually confirmed by the user 22 can be reduced.

[0260] The first semi-transmissive mirror 11 of the display device 1A may be configured to include a Fresnel lens as Figure 23 shown. In this case, the thickness of the first semi-transmissive mirror 11 can be reduced. As a result, the display device 1A can be miniaturized in the depth direction. Also, since the first semi-transmissive mirror 11 including the Fresnel lens is substantially flat, the distance between the first semi-transmissive mirror 11 and the display panel 2 can be reduced, or the first semi-transmissive mirror 11 and the display panel 2 can be brought into contact with each other. Therefore, the display device 1A can be further miniaturized in the depth direction. The first semi-transmissive mirror 11 including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transmissive mirror 11 including the Fresnel lens may be formed with a plurality of metal thin lines that achieve polarization selectivity for transmitting S-wave polarized light and reflecting P-wave polarized light on the surface facing the display panel 2 or the surface facing the first retardation plate 12. In this case, the decrease in the brightness of the virtual image V visually confirmed by the user 22 can be reduced.

[0261] The semi-transparent mirror 6 of the display device 1 may also be configured to include a Fresnel lens. In this case, the thickness of the semi-transparent mirror 6 can be reduced, and as a result, the display device 1 can be miniaturized in the depth direction. In addition, since the semi-transparent mirror 6 including the Fresnel lens is substantially flat, the distance between the semi-transparent mirror 6 and the first phase difference plate 5 can be reduced, or the semi-transparent mirror 6 and the first phase difference plate 5 can be brought into contact with each other, so that the display device 1 can be further miniaturized in the depth direction.

[0262] The first semi-transmissive mirror 17 of the display device 1B can be configured to include a Fresnel lens. In this case, the thickness of the first semi-transmissive mirror 17 can be reduced, and as a result, the display device 1B can be miniaturized in the depth direction. In addition, since the first semi-transmissive mirror 17 including the Fresnel lens is substantially flat, the distance between the first semi-transmissive mirror 17 and the display panel 2 can be reduced, or the first semi-transmissive mirror 17 and the display panel 2 can be brought into contact with each other, so that the display device 1B can be further miniaturized in the depth direction. The first semi-transmissive mirror 17 including the Fresnel lens can be configured to have polarization selectivity. For example, the first semi-transmissive mirror 17 including the Fresnel lens can be formed with a plurality of metal fine wires on the surface opposite to the display panel 2 or the surface opposite to the first phase difference plate 18, which realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the reduction in brightness of the virtual image V visually recognized by the user 22 can be reduced.

[0263] The third semi-transparent mirror 21 of the display device 1B may also be configured to include a Fresnel lens. In this case, the thickness of the third semi-transparent mirror 21 can be reduced, and as a result, the display device 1B can be miniaturized in the depth direction. The third semi-transparent mirror 21 including the Fresnel lens may be configured to have polarization selectivity. For example, the third semi-transparent mirror 21 including the Fresnel lens may be formed with a plurality of metal fine wires on the surface opposite to the second phase difference plate 20 or on the surface opposite to the surface opposite to the second phase difference plate 20, which realize polarization selectivity for reflecting S-wave polarized light and transmitting P-wave polarized light. In this case, the quality reduction of the virtual image V visually recognized by the user 22 can be reduced, and the brightness reduction of the virtual image V can be reduced.

[0264] Next, the control of the viewing area in the imaging device 100 (display device 1, 1A, 1A', 1B) will be described. In the following description, the imaging device 100 is set as a digital interior rearview mirror (refer to Figure 10). The imaging device 100 is provided with an angle sensor that detects the orientation of the display devices 1, 1A, 1A', 1B with respect to a specified direction fixed to the moving body 23. The specified direction can be, for example, the vehicle length direction of the moving body 23, but is not limited thereto. The angle sensor can be a 3-axis angle sensor capable of detecting the orientation (roll, pitch, yaw) of the display devices 1, 1A, 1A', 1B. The moving body 23 is provided with a DMS (Driver Monitoring System), and the imaging device 100 can communicate with the DMS and can control the DMS. The DMS can photograph the face of the user 22 seated in the driver's seat of the moving body 23, perform face authentication of the user 22, and can determine whether the user 22 is a known user. A known user can refer to a user for whom information such as features for face authentication, the position of the eyes during driving, and the orientation of the face (also referred to as user information) is stored in the storage unit of the controller 43 and / or the storage unit of the DMS.

[0265] When the user 22 is located in front of the display devices 1, 1A, 1A', 1B, the size of the left viewing area PL is substantially the same as the size of the right viewing area PR (see Figure 25 ), so the user 22 can visually confirm the virtual image V that changes corresponding to the movement of the head in the same way as when using a normal in-vehicle rearview mirror. When the user 22 is not located in front of the display devices 1, 1A, 1A', 1B, the size of the left viewing area PL is not the same as the size of the right viewing area PR (see Figure 26 ), and the user 22 cannot visually confirm the virtual image V that changes corresponding to the movement of the head in the same way as when using a normal in-vehicle rearview mirror, and may feel a sense of discomfort.

[0266] Refer to Figure 29 The flowchart shown below explains the control of the imaging device 100 by the controller 43. In the flowchart, "step" is abbreviated as "S", and in the diagram, [Yes] represents "positive" in the judgment control (computer flag = 1), and [No] represents "negative" (computer flag = 0).

[0267] Figure 29 The flowchart, for example, starts when the user 22 is seated in the driver's seat of the moving body 23 and starts the engine of the moving body 23.

[0268] In [S1], the DMS is controlled in such a way as to confirm the user 22 seated in the driver's seat of the moving body 23 (user confirmation).

[0269] In [S2], the DMS is controlled in such a way that face authentication of the user 22 sitting in the driver's seat is performed to determine whether the user 22 is a known user. If the user 22 is a known user [Yes] in [S2], it proceeds to [S3]. If the user 22 is not a known user [No] in [S2], it proceeds to [S7].

[0270] In [S3], user information of the user 22 (information such as the position of the eyes and the orientation of the face during driving) is obtained from the DMS.

[0271] In [S4], based on the user information obtained in [S3], the display devices 1, 1A, 1A', 1B are adjusted. The adjustment of the display devices 1, 1A, 1A', 1B may include changing the display area of the display image in the display surface 2a of the display panel 2 according to the orientation of the display devices 1, 1A, 1A', 1B, the position of the eyes of the user 22, the orientation of the face, etc. The change of the display area can be as Figure 27 shown by setting a part of the display surface 2a as a non-display area 2b where no image is displayed. By Figure 27 changing the display area of the display image in the display surface 2a as shown, even when the user 22 is not located directly in front of the display devices 1, 1A, 1A', 1B, it is possible to make the size of the left viewing area PL and the size of the right viewing area PR substantially the same. As a result, the possibility that the user 22 feels a sense of discomfort can be reduced.

[0272] The adjustment of the display devices 1, 1A, 1A', 1B may include sliding (parallel moving) at least one of the reflective polarizing plate 8, the semi-transmissive mirror 6, and the display panel 2 in a direction orthogonal to the emission direction of the display light from the display panel 2 according to the orientation of the display devices 1, 1A, 1A', 1B, the position of the eyes of the user 22, the orientation of the face, etc. By sliding at least one of the reflective polarizing plate 8, the semi-transmissive mirror 6, and the display panel 2, as Figure 28 shown, it is possible to make the size of the left viewing area PL and the size of the right viewing area PR substantially the same. As a result, the possibility that the user 22 feels a sense of discomfort can be reduced. In addition, when sliding at least one of the reflective polarizing plate 8, the semi-transmissive mirror 6, and the display panel 2, it is possible to reduce the case where the sizes of the left viewing area PL and the right viewing area PR are smaller compared to the case where the user 22 is located directly in front of the display devices 1, 1A, 1A', 1B.

[0273] In [S5], the controller 43 receives an instruction from the user 22 regarding whether readjustment of the display devices 1, 1A, 1A', 1B is required. The imaging device 100 may be configured such that the user 22 can indicate an intention for readjustment by operating a button or the like provided on the steering wheel. The imaging device 100 may also be configured such that the user 22 can swing the imaging device 100 and change the orientation of the imaging device 100 to indicate an intention for readjustment. The change in the orientation of the imaging device 100 can be detected using a three-axis angle sensor of the imaging device 100. It should be noted that the controller 43 may determine that readjustment is not required if no instruction is received from the user 22 within a specified time from the start of receiving the instruction from the user 22. The specified time may be, for example, about 3 to 10 seconds, but is not limited thereto.

[0274] In the case where readjustment [Yes] of the display devices 1, 1A, 1A', 1B is required in [S5], the process proceeds to [S6]. In the case where readjustment [No] of the display devices 1, 1A, 1A', 1B is not required in [S5], this flowchart ends. It should be noted that in [S5], in the case where readjustment [Yes] of the display devices 1, 1A, 1A', 1B is required, the process proceeds to [S7].

[0275] In [S6], the controller 43 controls the DMS in a manner to detect user information of the user 22 (information such as the position of the eyes and the orientation of the face during driving), and obtains the user information of the user 22 from the DMS.

[0276] In [S7], based on the user information obtained in [S6], adjustment of the display devices 1, 1A, 1A', 1B is performed. The adjustment of the display devices 1, 1A, 1A', 1B may be the same as the adjustment of the display devices 1, 1A, 1A', 1B in [S4].

[0277] In [S8], an instruction from the user 22 regarding whether readjustment of the display devices 1, 1A, 1A', 1B is required is received. The reception of the instruction from the user 22 may be the same as in [S5]. In the case where readjustment [Yes] of the display devices 1, 1A, 1A', 1B is required in [S8], the process returns to [S6]. In the case where readjustment [No] of the display devices 1, 1A, 1A', 1B is not required in [S8], the process proceeds to [S9]. It should be noted that in the case where readjustment [Yes] of the display devices 1, 1A, 1A', 1B is required in [S8], the process may also return to [S7].

[0278] In [S9], the controller 43 stores information related to the user information of the user 22 and the adjustment of the display devices 1, 1A, 1A', 1B in the storage unit of the controller 43 and / or the storage unit of the DMS, and this flowchart ends.

[0279] According to Figure 29 the flowchart, it is possible to efficiently control the viewing area in the digital rearview mirror inside the vehicle, and it is possible to reduce the possibility that the user 22 feels discomfort. It should be noted that Figure 29 the flowchart can also be applied when the imaging device 100 constitutes a digital side rearview mirror.

[0280] Other examples of the display devices 1, 1A, 1A', 1B will be described. For the same structures as the display devices 1, 1A, 1A', 1B, the same reference numerals are assigned, and detailed descriptions thereof are omitted. The display device 1C in this example is provided with a display panel 2, an optical system 35, and a housing 36 as Figure 33 shown.

[0281] The display panel 2 has a display surface 2a and displays a display image on the display surface 2a. The optical system 35 projects the display light emitted from the display panel 2 as a virtual image V in the field of view of the user 22. The optical system 35 may be the optical system 3 (refer to Figure 2 , 3 , 30), or may be the optical system 10 (refer to Figure 4 , 5 , 31), or may be the optical system 16 (refer to Figure 9 , 32 ). Figures 33 to 36 Shows the case where the optical system 35 is the optical system 3 as Figure 30 shown.

[0282] The housing 36 houses the display panel 2 and the optical system 35. The housing 36 may hold the display panel 2 and the optical system 35. When the display device 1C includes the irradiator 4, the housing 36 may house the irradiator 4 and hold the irradiator 4. The housing 36 has a window (opening) 37 through which the light emitted from the optical system 35 is transmitted. The display device 1C may be arranged such that the window 37 overlaps with the display panel 2 when observing the window 37 of the housing 36. In addition, the display device 1C may be arranged such that the window 37 overlaps with the optical system 35 when observing the window 37 of the housing 36. In addition, the display device 1C may be arranged such that the display panel 2 overlaps with the optical system 35 when observing the window 37 of the housing 36. In this case, the occupied space of the display device 1C can be reduced, and as a result, the display device 1C can be miniaturized. In addition, in the display device 1C, the display light emitted from the display panel 2 substantially propagates on one axis and forms an image as the virtual image V. Therefore, it is possible to reduce the distortion, uneven brightness, etc. of the virtual image V visually confirmed by the user 22, and the design of the optical system 35 becomes easy.

[0283] The housing 36 may be as Figure 33 ,34 As shown, it has a light-transmitting plate 38 disposed on the window 37. The light-transmitting plate 38 can transmit the light emitted from the optical system 35. The light-transmitting plate 38 at least partially blocks the window 37. The light-transmitting plate 38 can be made of, for example, glass, resin, etc.

[0284] The optical system 35 (optical system 3) can have a third retardation plate 25 and a fourth retardation plate 26. The third retardation plate 25 can be located on the surface of the second retardation plate 7 facing the semi-transmissive mirror 6. The fourth retardation plate 26 can be located on the surface of the third retardation plate 25 facing the semi-transmissive mirror 6. Thus, even when the user 22 is not located in front of the display device 1C, the relative angle between the transmission axis of the front polarizing plate of the display panel 2 and the transmission axis of the reflective polarizing plate 8 can be made close to the cross-Nicol configuration, and the reduction in the display quality of the display device 1C can be reduced. The third retardation plate 25 and the fourth retardation plate 26 can be a 1 / 2 wave plate (half-wave plate), but are not limited thereto. The third retardation plate 25 and the fourth retardation plate 26 can also be a 1 / 4 wave plate, a 1 / 8 wave plate, a 1 / 16 wave plate, etc., or a wave plate that gives other phase differences. The third retardation plate 25 and the fourth retardation plate 26 can be wave plates that give the same phase difference or wave plates that give different phase differences. The optical axis of the third retardation plate 25 can also be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizing plate 8.

[0285] The optical system 35 (optical system 3) can have an anti-reflection structure film 39 located on the surface of the first retardation plate 5 facing the semi-transmissive mirror 6. The anti-reflection structure film 39 can attenuate the reflected light of the light incident from the semi-transmissive mirror 6 side. Thus, the situation where unnecessary light, external interference light, etc. are reflected by the first retardation plate 5 and then exit from the display device 1C and enter the eyes of the user 22 can be reduced.

[0286] The optical system 35 (optical system 3) can have an anti-reflection structure film 40 located on the surface of the fourth retardation plate 26 facing the semi-transmissive mirror 6. Thus, the situation where unnecessary light, external interference light, etc. are reflected by the fourth retardation plate 26 and then exit from the display device 1C and enter the eyes of the user 22 can be reduced.

[0287] The reflective polarizing plate 8, the second retardation plate 7, the third retardation plate 25, the fourth retardation plate 26, and the anti-reflection structure film 40 can be integrated with the light-transmitting plate 38. Thus, the display device 1C can be thinned in the depth direction (Z-axis direction). In addition, the deformation of the reflective polarizing plate 8, the second retardation plate 7, the third retardation plate 25, the fourth retardation plate 26, the anti-reflection structure film 40, and the light-transmitting plate 38 can be reduced.

[0288] The display device 1C may have a touch panel 41. The touch panel 41 may also at least partially block the window 37. The touch panel 41 may be mounted on the housing 36 as shown in Figure 35 , 36 . The touch panel 41 may be mounted on the housing 36 in such a manner as to cover the window 37 in which the light transmissive plate 38 is disposed, as shown in Figure 35 , 36 . The touch panel 41 may cover the light transmissive plate 38. The touch panel 41 is communicably connected to the controller 43 via a wired or wireless communication line. Thus, the user 22 can operate the display device 1C by means of the touch panel 41. The touch panel 41 may be a known touch panel.

[0289] The display system 200 of the present invention will be described. The display system 200 includes display devices 1, 1A, 1A', 1B, 1C and a camera 201 as shown in Figure 39 . The display panels 2 of the display devices 1, 1A, 1A', 1B, 1C can communicate with the camera 201 and display the images captured by the camera 201. The display panel 2 and the camera 201 may be connected, for example, via a wired, wireless, CAN (Controller Area Network), or the like.

[0290] The moving body (vehicle) 23 of the present invention includes the display system 200. The display devices 1, 1A, 1A', 1B, 1C are small display devices and do not occupy a large volume in the cab of the vehicle 23 even when disposed therein, and are unlikely to interfere with driving. Therefore, the user 22 can appropriately visually confirm the virtual image V or the real image. The display system 200 can be applied to the digital interior rearview mirror of the vehicle 23, and can also be applied to the digital side mirrors 1L, 1R (see Figure 12 ). The display system 200 can also be applied to the assembly 29, CID (Center Information Display) 30, PID (Passenger Information Display) 31, RSE (Rear Seat Entertainment) system 32, etc. within the dash panel of the vehicle 23 (see Figure 10 , 12 ).

[0291] According to the present invention, it is possible to reduce the degradation of the display quality of the small display device and improve the light utilization efficiency. In addition, according to the present invention, it is possible to provide a small imaging device that enables the user to visually confirm the virtual image well.

[0292] As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and various changes, improvements, etc. can be made without departing from the gist of the present invention. Embodiments obtained by appropriately combining technical means separately disclosed in different embodiments are also included in the technical scope of the present invention. For example, the functions included in each structural part, etc. can be reconfigured in a logically consistent manner, and multiple structural parts, etc. can be combined into one or divided. That is, it should be noted that those skilled in the art can easily make various deformations or corrections based on the present invention. In addition, it should be noted that these changes, deformations, or corrections are included in the scope of the present invention.

[0293] The display device of the present invention can be implemented by the following solutions (1) to (48).

[0294] (1) A display device, wherein,

[0295] The display device includes:

[0296] A display panel that emits display light that is linearly polarized light;

[0297] A first retardation plate that faces the display panel;

[0298] A second retardation plate that is disposed separately from the first retardation plate;

[0299] A reflective polarizer 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; and

[0300] A half mirror that is disposed between the first retardation plate and the second retardation plate and has a reflection surface facing the second retardation plate,

[0301] The first retardation plate and the second retardation plate are quarter-wave plates.

[0302] (1') A display device, wherein,

[0303] The display device includes:

[0304] A display panel that emits display light;

[0305] A first retardation plate that faces the display panel;

[0306] A second retardation plate that is disposed separately from the first retardation plate;

[0307] A reflective polarizer that is disposed opposite to the second retardation plate and transmits first polarized light and reflects second polarized light; and

[0308] A semi-transmissive mirror, which is disposed between the first retardation plate and the second retardation plate and has a reflective surface facing the second retardation plate,

[0309] The first retardation plate and the second retardation plate make the display light into the first polarized light and the second polarized light.

[0310] (2)The display device according to the above (1), wherein,

[0311] Air is interposed between the first retardation plate and the second retardation plate.

[0312] (3)The display device according to the above (1) or (2), wherein,

[0313] The display device includes a third retardation plate disposed between the display panel and the reflective polarizing plate.

[0314] (4)The display device according to the above (3), wherein,

[0315] The display device includes a fourth retardation plate disposed between the display panel and the reflective polarizing plate.

[0316] (5)The display device according to the above (4), wherein,

[0317] One of the third retardation plate and the fourth retardation plate is a quarter-wave plate, and the other of the third retardation plate and the fourth retardation plate is a half-wave plate.

[0318] (6)The display device according to the above (4), wherein,

[0319] The third retardation plate and the fourth retardation plate are half-wave plates.

[0320] (7)The display device according to any one of the above (1) to (6), wherein,

[0321] The reflective surface of the semi-transmissive mirror is concave.

[0322] (8)The display device according to any one of the above (1) to (6), wherein,

[0323] The semi-transmissive mirror is a flat optical element composed of a holographic optical element.

[0324] (9)The display device according to any one of the above (1) to (6), wherein,

[0325] The semi-transmissive mirror includes a Fresnel lens.

[0326] The display device according to (8) or (9) above, wherein,

[0327] The semi-transmissive mirror is integrated with the first retardation plate and / or the second retardation plate.

[0328] (11) A display device, wherein,

[0329] The display device includes:

[0330] A display panel that emits display light that is linearly polarized light;

[0331] A first retardation plate that faces the display panel;

[0332] A second retardation plate that is arranged separately from the first retardation plate;

[0333] A first semi-transmissive mirror that is arranged between the display panel and the first retardation plate and has a first reflection surface that faces the first retardation plate;

[0334] A second semi-transmissive mirror that is arranged between the first retardation plate and the second retardation plate and has a second reflection surface that faces the first retardation plate; and

[0335] A polarizing plate that faces the second retardation plate,

[0336] The first retardation plate and the second retardation plate are quarter-wave plates.

[0337] (11') A display device, wherein,

[0338] The display device includes:

[0339] A display panel that emits display light;

[0340] A first retardation plate that faces the display panel;

[0341] A second retardation plate that is arranged separately from the first retardation plate;

[0342] A first semi-transmissive mirror that is arranged between the display panel and the first retardation plate and has a first reflection surface that faces the first retardation plate;

[0343] A second semi-transmissive mirror that is arranged between the first retardation plate and the second retardation plate and has a second reflection surface that faces the first retardation plate; and

[0344] A polarizing plate that faces the second retardation plate,

[0345] The first retardation plate and the second retardation plate make the display light into a first polarized light that transmits through the polarizing plate and a second polarized light that is less transmissive through the polarizing plate than the first polarized light.

[0346] (12)The display device according to the above (11), wherein,

[0347] The second reflecting surface is a convex surface protruding toward the first retardation plate side.

[0348] (13)The display device according to the above (11) or (12), wherein,

[0349] Air is interposed between the first half-transmissive mirror and the first retardation plate.

[0350] (14)The display device according to any one of the above (11) to (13), wherein,

[0351] The display device includes a third retardation plate disposed between the display panel and the polarizing plate.

[0352] (15)The display device according to the above (14), wherein,

[0353] The display device includes a fourth retardation plate disposed between the display panel and the polarizing plate.

[0354] (16)The display device according to the above (15), wherein,

[0355] One of the third retardation plate and the fourth retardation plate is a quarter-wave plate, and the other of the third retardation plate and the fourth retardation plate is a half-wave plate.

[0356] (17)The display device according to the above (15), wherein,

[0357] The third retardation plate and the fourth retardation plate are half-wave plates.

[0358] (18)The display device according to any one of the above (11) to (17), wherein,

[0359] The first reflecting surface is concave.

[0360] (19)The display device according to any one of the above (11) to (17), wherein,

[0361] The first half-transmissive mirror and the second half-transmissive mirror are flat optical elements made of holographic optical elements.

[0362] The display device according to any one of (11) to (17) above, wherein,

[0363] The first semi-transmissive mirror and the second semi-transmissive mirror include Fresnel lenses.

[0364] The display device according to (19) or (20) above, wherein,

[0365] The first semi-transmissive mirror is integrated with the display panel and / or the first retardation plate.

[0366] The display device according to (19) or (20) above, wherein,

[0367] The second semi-transmissive mirror is integrated with the first retardation plate and / or the second retardation plate.

[0368] A display device, wherein,

[0369] The display device includes:

[0370] A display panel that emits display light that is linearly polarized light;

[0371] A first retardation plate that faces the display panel;

[0372] A second retardation plate that is disposed separately from the first retardation plate;

[0373] A first semi-transmissive mirror that is disposed between the display panel and the first retardation plate and has a first reflective surface that faces the first retardation plate;

[0374] A second semi-transmissive mirror that is disposed between the first retardation plate and the second retardation plate and has a second reflective surface that faces the first retardation plate and a third reflective surface that faces the second retardation plate; and

[0375] A third semi-transmissive mirror that has a fourth reflective surface that faces the second retardation plate,

[0376] The first retardation plate and the second retardation plate are quarter-wave plates.

[0377] A display device, wherein,

[0378] The display device includes:

[0379] A display panel that emits display light;

[0380] A first retardation plate that transmits the display light;

[0381] A second retardation plate, which is disposed separately from the first retardation plate;

[0382] A first semi-transmissive mirror, which is disposed between the display panel and the first retardation plate and has a first reflective surface facing the first retardation plate;

[0383] A second semi-transmissive mirror, which is disposed between the first retardation plate and the second retardation plate and has a second reflective surface facing the first retardation plate and a third reflective surface facing the second retardation plate; and

[0384] A third semi-transmissive mirror, which has a fourth reflective surface facing the second retardation plate.

[0385] (24)The display device according to (23) above, wherein,

[0386] Air is interposed between the first semi-transmissive mirror and the first retardation plate and between the third semi-transmissive mirror and the second retardation plate.

[0387] (25)The display device according to (23) or (24) above, wherein,

[0388] The first reflective surface and the fourth reflective surface are concave.

[0389] (26)The display device according to (23) or (24) above, wherein,

[0390] The first semi-transmissive mirror and the third semi-transmissive mirror are flat optical elements made of holographic optical elements.

[0391] (27)The display device according to (23) or (24) above, wherein,

[0392] The first semi-transmissive mirror and the third semi-transmissive mirror include Fresnel lenses.

[0393] (28)The display device according to (26) or (27) above, wherein,

[0394] The first semi-transmissive mirror is integrated with the display panel and / or the first retardation plate.

[0395] (29)The display device according to any one of (26) to (28) above, wherein,

[0396] The second semi-transmissive mirror is integrated with the second retardation plate.

[0397] (30)The display device according to any one of (1) to (29) above, wherein,

[0398] The display light includes the display light for the left-eye image and the display light for the right-eye image.

[0399] The display device further includes an optical element that defines the light directions of the display light for the left-eye image and the display light for the right-eye image.

[0400] (31) An imaging device, wherein,

[0401] The imaging device includes the display device according to any one of (1) to (30) above.

[0402] (32) The imaging device according to (31) above, wherein,

[0403] The virtual image projected within the user's field of view includes a binocular visible area visually confirmed by both the user's left eye and right eye, a left-eye visible area visually confirmed only by the left eye, and a right-eye visible area visually confirmed only by the right eye.

[0404] (33) A display device, wherein,

[0405] The display device includes:

[0406] A display panel;

[0407] An optical system that projects the display light emitted from the display panel as a virtual image or a real image; and

[0408] A housing that houses the display panel and the optical system,

[0409] The housing has a window that transmits the light emitted from the optical system,

[0410] The display device is arranged such that the window, the optical system, and the display panel overlap when observing the window of the housing.

[0411] (34) The display device according to (33) above, wherein,

[0412] The housing has a light-transmitting plate disposed on the window.

[0413] (35) The display device according to (34) above, wherein,

[0414] The display device includes a touch panel mounted on the housing so as to cover the light-transmitting plate.

[0415] (36) The display device according to any one of (1) to (30) and (33) to (35) above, wherein,

[0416] The display device includes an irradiator that irradiates light onto the surface of the display panel opposite to the display surface.

[0417] (37) The display device according to the above (1) to (30) and (33) to (36), wherein

[0418] The display device includes a controller having a function of controlling at least one of the image displayed on the display panel and the irradiator.

[0419] (38) A vehicle, wherein

[0420] The vehicle includes the display device according to the above (37).

[0421] (39) A display device, wherein

[0422] The display device has:

[0423] A display panel that emits display light that is linearly polarized light;

[0424] A first retardation plate that faces the display panel;

[0425] A second retardation plate that is disposed separately from the first retardation plate;

[0426] 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; and

[0427] A half mirror that is disposed between the first retardation plate and the second retardation plate and has a reflective surface facing the second retardation plate,

[0428] The first retardation plate and the second retardation plate are quarter-wave plates,

[0429] The optical path length of the light that exits from the display panel, transmits through the half mirror, is reflected by the reflective polarizing plate, and reaches the half mirror is smaller than the focal length of the half mirror.

[0430] (40) A display device, wherein

[0431] The display device has:

[0432] A display panel that emits display light that is linearly polarized light;

[0433] A first retardation plate that faces the display panel;

[0434] A second retardation plate that is disposed separately from the first retardation plate;

[0435] 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; and

[0436] A semi-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a reflective surface facing the second retardation plate,

[0437] The first retardation plate and the second retardation plate are quarter-wave plates,

[0438] The optical path length of the light that exits the display panel, transmits through the semi-transmissive mirror, is reflected by the reflective polarizing plate, and reaches the semi-transmissive mirror is greater than the focal length of the semi-transmissive mirror.

[0439] (41) A display device, wherein,

[0440] The display device includes:

[0441] A display panel that emits display light that is linearly polarized light;

[0442] A first retardation plate that transmits the display light;

[0443] A second retardation plate disposed separately from the first retardation plate;

[0444] A first semi-transmissive mirror disposed between the display panel and the first retardation plate and having a first reflective surface facing the first retardation plate;

[0445] A second semi-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a second reflective surface facing the first retardation plate; and

[0446] A polarizing plate facing the second retardation plate,

[0447] The first retardation plate and the second retardation plate are quarter-wave plates,

[0448] The optical path length of the light that exits the display panel, transmits through the first semi-transmissive mirror, is reflected by the second semi-transmissive mirror, and reaches the first semi-transmissive mirror is smaller than the focal length of the first semi-transmissive mirror.

[0449] (42) A display device, wherein,

[0450] The display device includes:

[0451] A display panel that emits display light that is linearly polarized light;

[0452] A first retardation plate that transmits the display light;

[0453] A second retardation plate, which is disposed separately from the first retardation plate;

[0454] A first semi-transmissive mirror, which is disposed between the display panel and the first retardation plate and has a first reflective surface opposed to the first retardation plate;

[0455] A second semi-transmissive mirror, which is disposed between the first retardation plate and the second retardation plate and has a second reflective surface opposed to the first retardation plate; and

[0456] A polarizing plate, which is opposed to the second retardation plate,

[0457] The first retardation plate and the second retardation plate are quarter-wave plates,

[0458] The optical path length of the light that exits from the display panel, transmits through the first semi-transmissive mirror, is reflected by the second semi-transmissive mirror, and reaches the first semi-transmissive mirror is greater than the focal length of the first semi-transmissive mirror.

[0459] (43) A display device, wherein,

[0460] The display device includes:

[0461] A display panel, which emits display light that is linearly polarized light;

[0462] A first retardation plate, which transmits the display light;

[0463] A second retardation plate, which is disposed separately from the first retardation plate;

[0464] A first semi-transmissive mirror, which is disposed between the display panel and the first retardation plate and has a first reflective surface opposed to the first retardation plate;

[0465] A second semi-transmissive mirror, which is disposed between the first retardation plate and the second retardation plate and has a second reflective surface opposed to the first retardation plate and a third reflective surface opposed to the second retardation plate; and

[0466] A third semi-transmissive mirror, which has a fourth reflective surface opposed to the second retardation plate,

[0467] The first retardation plate and the second retardation plate are quarter-wave plates,

[0468] The optical path length of the light that exits from the display panel, transmits through the first half-transmissive mirror, is reflected by the second half-transmissive mirror, and reaches the first half-transmissive mirror is smaller than the focal length of the first half-transmissive mirror, and the optical path length of the light that exits from the display panel, transmits through the first half-transmissive mirror, transmits through the second half-transmissive mirror, and reaches the third half-transmissive mirror is smaller than the focal length of the first half-transmissive mirror.

[0469] (44) A display device, wherein,

[0470] The display device includes:

[0471] A display panel that emits display light that is linearly polarized;

[0472] A first retardation plate that transmits the display light;

[0473] A second retardation plate that is disposed separately from the first retardation plate;

[0474] A first half-transmissive mirror that is disposed between the display panel and the first retardation plate and has a first reflective surface facing the first retardation plate;

[0475] A second half-transmissive mirror that is disposed between the first retardation plate and the second retardation plate and has a second reflective surface facing the first retardation plate and a third reflective surface facing the second retardation plate; and

[0476] A third half-transmissive mirror that has a fourth reflective surface facing the second retardation plate,

[0477] The first retardation plate and the second retardation plate are quarter-wave plates,

[0478] The optical path length of the light that exits from the display panel, transmits through the first half-transmissive mirror, is reflected by the second half-transmissive mirror, and reaches the first half-transmissive mirror is larger than the focal length of the first half-transmissive mirror, and the optical path length of the light that exits from the display panel, transmits through the first half-transmissive mirror, transmits through the second half-transmissive mirror, and reaches the third half-transmissive mirror is larger than the focal length of the first half-transmissive mirror.

[0479] (45) A display device, wherein,

[0480] The display device includes:

[0481] A display panel that emits display light; and

[0482] A convex lens through which the display light transmits,

[0483] The optical path length from the display panel to the convex lens is smaller than the focal length of the convex lens.

[0484] (46) A display device, wherein,

[0485] The display device includes:

[0486] A display panel that emits display light; and

[0487] A convex lens through which the display light is transmitted,

[0488] The optical path length from the display panel to the convex lens is greater than the focal length of the convex lens.

[0489] (47) A display system, wherein,

[0490] The display system includes:

[0491] The display device according to any one of the above (1) to (30), (33) to (37), and (39) to (46); and

[0492] A camera,

[0493] The display panel can communicate with the camera and display an image captured by the camera.

[0494] (48) A vehicle, wherein,

[0495] The vehicle includes the display system according to the above (47).

[0496] Explanation of reference numerals

[0497] 1, 1A, 1A’, 1B Display device

[0498] 2 Display panel

[0499] 2a Display surface

[0500] 3 Optical system

[0501] 4 Illuminator

[0502] 5 First retardation plate

[0503] 6 Half mirror

[0504] 6a Reflective surface

[0505] 7 Second retardation plate

[0506] 8 Reflective polarizer

[0507] 9 Optical element

[0508] 10 Optical system

[0509] 11 First half mirror

[0510] 11a Reflecting surface

[0511] 12 First retardation plate

[0512] 13, 13’ Second half-transmissive mirror

[0513] 13a, 13’a Reflecting surface

[0514] 14 Second retardation plate

[0515] 15 Polarizing plate

[0516] 16 Optical system

[0517] 17 First half-transmissive mirror

[0518] 17a Reflecting surface

[0519] 18 First retardation plate

[0520] 19 Second half-transmissive mirror

[0521] 19a Reflecting surface

[0522] 19b Reflecting surface

[0523] 20 Second retardation plate

[0524] 21 Third half-transmissive mirror

[0525] 21a Reflecting surface

[0526] 22 User

[0527] 22L Left eye

[0528] 22R Right eye

[0529] 23 Moving body

[0530] 24 Windshield

[0531] 25 Third retardation plate

[0532] 26 Fourth retardation plate

[0533] 27 Housing

[0534] 28 Opening

[0535] 29 Assembly

[0536] 30 CID

[0537] 31 PID

[0538] 32 RSE

[0539] 33 Fresnel lens

[0540] 33a First side

[0541] 33b Second side

[0542] 33c Reference point

[0543] 34 Semi-transmissive reflection layer

[0544] 35 Optical system

[0545] 36 Housing

[0546] 37 Window

[0547] 38 Light transmission plate

[0548] 39, 40 Moth-eye structure film

[0549] 41 Touch panel

[0550] 42 Convex lens

[0551] 43 Controller

[0552] 100 Imaging device

[0553] 101 Reflective optical element

[0554] 102 Camera

[0555] 200 Display system

[0556] 201 Camera.

Claims

1. A display device, wherein, the display device includes: a display panel that emits display light; a first retardation plate that faces the display panel; a second retardation plate that is disposed separately from the first retardation plate; a reflective polarizing plate that is disposed to face the second retardation plate and transmits first polarized light and reflects second polarized light; and a half - mirror that is disposed between the first retardation plate and the second retardation plate and has a reflective surface facing the second retardation plate, the first retardation plate and the second retardation plate make the display light into first polarized light and second polarized light.

2. The display device according to claim 1, wherein, air is interposed between the first retardation plate and the second retardation plate.

3. The display device according to claim 1 or 2, wherein, the display device has a third retardation plate disposed between the display panel and the reflective polarizing plate.

4. The display device according to claim 3, wherein, the display device has a fourth retardation plate disposed between the display panel and the reflective polarizing plate.

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

6. The display device according to claim 4, wherein, the third retardation plate and the fourth retardation plate are half - wave plates.

7. The display device according to any one of claims 1 to 6, wherein, the reflective surface of the half - mirror is concave.

8. The display device according to any one of claims 1 to 6, wherein, the half - mirror is a flat optical element composed of a holographic optical element.

9. The display device according to any one of claims 1 to 6, wherein, the half - mirror includes a Fresnel lens.

10. The display device according to claim 8 or 9, wherein, the half - mirror is integrated with the first retardation plate and / or the second retardation plate.

11. A display device, wherein, the display device includes: a display panel that emits display light; a first retardation plate that transmits the display light; a second retardation plate that is disposed separately from the first retardation plate; a first half - mirror that is disposed between the display panel and the first retardation plate and has a first reflective surface facing the first retardation plate; a second half - mirror that is disposed between the first retardation plate and the second retardation plate and has a second reflective surface facing the first retardation plate; and a polarizing plate that faces the second retardation plate, the first retardation plate and the second retardation plate make the display light into first polarized light that transmits through the polarizing plate and second polarized light that has less transmission through the polarizing plate compared with the first polarized light.

12. The display device according to claim 11, wherein, the second reflective surface is a convex surface protruding toward the first retardation plate side.

13. The display device according to claim 11 or 12, wherein air is interposed between the first semi-transmissive mirror and the first retardation plate.

14. The display device according to any one of claims 11 to 13, wherein the display device includes a third retardation plate disposed between the display panel and the polarizing plate.

15. The display device according to claim 14, wherein the display device includes a fourth retardation plate disposed between the display panel and the polarizing plate.

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

17. The display device according to claim 15, wherein the third retardation plate and the fourth retardation plate are half-wave plates.

18. The display device according to any one of claims 11 to 17, wherein the first reflecting surface is concave.

19. The display device according to any one of claims 11 to 17, wherein the first semi-transmissive mirror and the second semi-transmissive mirror are flat optical elements formed of holographic optical elements.

20. The display device according to any one of claims 11 to 17, wherein the first semi-transmissive mirror and the second semi-transmissive mirror include Fresnel lenses.

21. The display device according to claim 19 or 20, wherein the first semi-transmissive mirror is integrated with the display panel and / or the first retardation plate.

22. The display device according to claim 19 or 20, wherein the second semi-transmissive mirror is integrated with the first retardation plate and / or the second retardation plate.

23. A display device, wherein the display device includes: a display panel that emits display light; a first retardation plate that transmits the display light; a second retardation plate that is disposed separately from the first retardation plate; a first semi-transmissive mirror that is disposed between the display panel and the first retardation plate and has a first reflecting surface facing the first retardation plate; a second semi-transmissive mirror that is disposed between the first retardation plate and the second retardation plate and has a second reflecting surface facing the first retardation plate and a third reflecting surface facing the second retardation plate; and a third semi-transmissive mirror that has a fourth reflecting surface facing the second retardation plate.

24. The display device according to claim 23, wherein air is interposed between the first semi-transmissive mirror and the first retardation plate and between the third semi-transmissive mirror and the second retardation plate.

25. The display device according to claim 23 or 24, wherein the first reflecting surface and the fourth reflecting surface are concave.

26. The display device according to claim 23 or 24, wherein at least one of the first semi-transmissive mirror and the third semi-transmissive mirror is a flat optical element formed of a holographic optical element.

27. The display device according to claim 23 or 24, wherein The first half-transmissive mirror and the third half-transmissive mirror include Fresnel lenses.

28. The display device according to claim 26 or 27, wherein the first half-transmissive mirror is integrated with the display panel and / or the first retardation plate.

29. The display device according to claims 26 to 28, wherein the second half-transmissive mirror is integrated with the second retardation plate.

30. The display device according to any one of claims 1 to 29, wherein the display light includes display light for a left-eye image and display light for a right-eye image, and the display device further includes an optical element that defines the light directions of the display light for the left-eye image and the display light for the right-eye image.

31. An imaging device, wherein the imaging device includes the display device according to any one of claims 1 to 30.

32. The imaging device according to claim 31, wherein the virtual image projected within the field of view of the user includes a binocular visible region visually confirmed by both the user's left eye and right eye, a left-eye visible region visually confirmed only by the left eye, and a right-eye visible region visually confirmed only by the right eye.

33. A display device, wherein the display device includes: a display panel; an optical system that projects the display light emitted from the display panel as a virtual image or a real image; and a housing that houses the display panel and the optical system, the housing having a window that transmits the light emitted from the optical system, and the display device is arranged such that the window, the optical system, and the display panel overlap when observing the window of the housing.

34. The display device according to claim 33, wherein the housing has a light-transmitting plate disposed on the window.

35. The display device according to claim 34, wherein the display device includes a touch panel mounted on the housing.

36. The display device according to any one of claims 1 to 30 and 33 to 35, wherein the display device includes an illuminator that irradiates light onto the surface of the display panel opposite to the display surface.

37. The display device according to any one of claims 1 to 30 and 33 to 36, wherein the display device includes a controller having a function of controlling at least one of the image displayed on the display panel and the illuminator.

38. A vehicle, wherein the vehicle includes the display device according to claim 37.

39. A display device, wherein the display device includes: a display panel that emits display light; and a convex lens through which the display light is transmitted, and the optical path length from the display panel to the convex lens is smaller than the focal length of the convex lens.

40. A display device, wherein the display device includes: a display panel that emits display light; and a convex lens through which the display light is transmitted, and the optical path length from the display panel to the convex lens is larger than the focal length of the convex lens.

41. A display system, wherein the display system includes: A display device according to any one of claims 1 to 30, 33 to 37, 39, and 40; and a camera, wherein the display panel is capable of communicating with the camera and displaying an image captured by the camera.

42. A vehicle, wherein the vehicle includes the display system according to claim 41.

Images