Display device, imaging device, display system and vehicle

Abstract

To provide a display device in which deformation of an optical member, positional deviation between the optical members and the like are difficult to occur and display quality is difficult to deteriorate.SOLUTION: A display device comprises: a display panel; a first retardation plate; a semi-transmissive mirror; a second retardation plate; and a reflective polarizing plate. The display panel emits display light. The first retardation plate is arranged facing the display panel. The second retardation plate is arranged being apart from the first retardation plate. The reflective polarizing plate is arranged facing the second retardation plate, and transmits first polarized light to reflect second polarized light. The semi-transmissive mirror is arranged between the first retardation plate and the second retardation plate, and has a reflection surface facing the second retardation plate. The first retardation plate and the second retardation plate convert the display light to the first polarized light and the second polarized light.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure 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 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The display device of the present disclosure includes a display panel that emits display light, a first retardation plate facing the display panel, a second retardation plate disposed apart from the first retardation plate, a reflective polarizing plate disposed facing the second retardation plate and transmitting a first polarization and reflecting a second polarization, and a semi-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a reflective surface facing the second retardation plate. The first retardation plate and the second retardation plate convert the display light into a first polarization and a second polarization.

[0005] Also, the display device of the present disclosure includes a display panel that emits display light, a first retardation plate that transmits the display light, a second retardation plate disposed apart from the first retardation plate, a first semi-transmissive mirror disposed between the display panel and the first retardation plate and having a first reflective surface facing the first retardation plate, 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, a polarizing plate facing the second retardation plate; The first retardation plate and the second retardation plate make the display light into a first polarization that passes through the polarizing plate and a second polarization that is less transmissive through the polarizing plate than the first polarization.

[0006] In addition, the display device of the present disclosure includes a display panel that emits display light; a first retardation plate that transmits the display light; a second retardation plate disposed apart from the first retardation plate; a first semi-transmissive mirror disposed between the display panel and the first retardation plate and having a first reflective surface facing the first retardation plate; 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 a third reflective surface facing the second retardation plate; a third semi-transmissive mirror having a fourth reflective surface facing the second retardation plate.

[0007] The imaging device of the present disclosure includes the above display device.

[0008] In addition, the display device of the present disclosure 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 has a window that transmits the light emitted from the optical system, and when looking at the window of the housing, the window, the optical system, and the display panel are arranged so as to overlap.

[0009] The vehicle of the present disclosure includes the above display device.

[0010] In addition, the display device of the present disclosure includes a display panel that emits display light, a convex lens through which the display light passes, and the optical path length from the display panel to the convex lens is smaller than the focal length of the convex lens.

[0011] In addition, the display device of the present disclosure includes a display panel that emits display light, and a convex lens through which the display light passes, and the optical path length from the display panel to the convex lens is greater than the focal length of the convex lens.

[0012] The display system of the present disclosure includes the above display device and a camera, and the display panel is communicable with the camera and displays an image captured by the camera.

[0013] The vehicle of the present disclosure includes the above display system.

Brief Description of the Drawings

[0014] The objects, features, and advantages of the present disclosure will become clearer from the following detailed description and the drawings.

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Mode for Carrying Out the Invention

[0015] Conventionally, various small display devices used in a digital room mirror disposed in a vehicle interior, a head-mounted display worn on a user's head, and the like have been proposed. The display device described in Patent Document 1 is configured to emit display light emitted from a display panel through a plurality of optical members such as a retardation plate and a reflective polarizing plate.

[0016] In the conventional display device, deformation of the optical member, misalignment between the optical members, etc. are likely to occur, and the display quality may deteriorate.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Some of the drawings used in the following description are schematic. The drawings used in the following description show the main components of the display device and the virtual image display device of the present disclosure. The display device and the virtual image display device of the present disclosure may include well-known components such as a holding member of an optical system and a housing that are not shown. In this specification, in some of the drawings, for convenience, a rectangular coordinate system XYZ is defined. The Y-axis direction is also referred to as the height direction. The Z-axis direction is also referred to as the emission direction or the depth direction.

[0018] FIGS. 1 to 39 are diagrams or graphs for explaining the display device, the imaging device, the display system, and the vehicle of the present disclosure. In FIGS. 2 to 5, 9, 15, 16, 20 to 22, 24, 30 to 32, for ease of illustration, the optical path of light incident on an optical member having light reflectivity and the optical path of light reflected by the optical member are shifted in the height direction (Y-axis direction) and shown.

[0019] As shown in FIG. 1, a display device 1 according to an embodiment of the present disclosure includes a display panel 2 and an optical system 3. The display device 1 causes a part of the display light emitted from the display panel 2 to enter the eyes of a user 22 and be visually recognized by the user 22 as an image, a picture, or a virtual image in the air. The display device 1 can cause the user 22 to visually recognize the display of the display panel 2 at a position different from the position of the display panel 2 with respect to the display light emitted from the display panel 2. In the positional embodiment of the present disclosure, the display device 1 causes the user 22 to visually recognize it as a virtual image V. The virtual image V may be formed on the farther side of the display device 1 as viewed from the user 22. The virtual image V may be an erect virtual image in which the display image displayed on the display panel 2 is enlarged. When the display device 1 includes a housing (see FIGS. 33 to 36) that houses the display panel 2 and the optical system 3, the virtual image V may be formed inside the housing or outside the housing. The virtual image V may be formed on the farther side of the display panel 2 as viewed from the user 22, or may be formed on the nearer side of the display panel 2. When the housing has a window 37 (see FIGS. 33 to 36) that transmits the display light emitted from the optical system 3, the virtual image V may be formed on the farther side of the window 37 (light transmission plate 38) as viewed from the user 22, or may be formed on the nearer side of the window. When the display device 1 has a touch panel 41 (see FIGS. 35 and 36), the virtual image V may be formed on the farther side of the touch panel 41 as viewed from the user 22, or may be formed on the nearer side of the touch panel 41.

[0020] Note that the display device 1 may be configured to allow a part of the display light emitted from the display panel 2 to enter the eyes of the user 22 and be visually recognized by the user 22 as a real image. The real image may be formed on the side closer to the user 22 than the display device 1 when viewed from the user 22. When the display device 1 includes a housing 36 (see FIGS. 33 to 36) that houses the display panel 2 and the optical system 3, the real image may be formed inside the housing 36 or outside the housing 36. The real image may be formed on the side farther from the display panel 2 or on the side closer to the display panel 2 when viewed from the user 22. When the housing 36 has a window 37 (see FIGS. 33 to 36) that transmits the display light emitted from the optical system 3, the real image may be formed 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) when viewed from the user 22. When the display device 1 has a touch panel 41 (see FIGS. 35 and 36), the real image may be formed on the side farther from the touch panel 41 or on the side closer to the touch panel 41 when viewed from the user 22.

[0021] The display panel 2 has a display surface 2a and displays a display image on the display surface 2a. In other words, the display panel 2 emits display light of the display image from the display surface 2a. The display panel 2 may 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.

[0022] The display panel 2 may be a liquid crystal panel. The liquid crystal panel may have a configuration of a known liquid crystal panel. A known liquid crystal panel may 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.

[0023] The display device 1 may include an irradiator 4 that irradiates the display panel 2 over its entire surface. The irradiator 4 is also referred to as a backlight. The irradiator 4 may be an edge-lit backlight or a direct-lit backlight. The edge-lit backlight has one or more light sources disposed on 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 and disperses it uniformly. The direct-lit 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 may be a cold cathode fluorescent lamp, a halogen lamp, a xenon lamp, etc., or may be a light emitting diode (LED), an organic light emitting diode (OLED), a semiconductor laser (LD), etc. 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 optical members whose optical characteristics have wavelength dependence, becomes easier.

[0024] The display panel 2 is not limited to a liquid crystal panel (a transmissive display panel). The display panel 2 may be a self-luminous display panel including self-luminous elements such as, for example, a light emitting diode (LED), an organic light emitting diode (OLED), a semiconductor laser (LD), etc.

[0025] The optical system 3 projects the display light emitted from the display panel 2 as a virtual image V within the visual field of the user 22. As shown in FIG. 2, the optical system 3 may be configured 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 this order in the emission direction (the positive direction of the Z-axis direction) of the display light from the display panel 2.

[0026] The first retardation plate 5 is positioned to face the display surface 2a of the display panel 2. The first retardation plate 5 is positioned at a distance from the display surface 2a in the light emission direction of the display light from the display panel 2. The second retardation plate 7 is positioned at a distance from the first retardation plate 5 in the light 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 give a phase difference of a quarter wavelength to the polarization plane (polarization plane of the electric field vibration direction) of the incident light. As a result, a part of the display light emitted from the display panel 2 can be reflected by the reflective polarizing plate 8 and made to enter the half-transmissive mirror 6.

[0027] The first retardation plate 5 and the second retardation plate 7 only need to be given the necessary phase difference to the light transmitted through the first retardation plate 5 and the second retardation plate 7 so 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 polarization obtained by passing through the first retardation plate 5 and the second retardation plate 7 is taken as the second polarization, the first retardation plate 5 and the second retardation plate 7 may not be quarter-wave plates but other retardation plates or combinations thereof as long as the second polarization is obtained. In the present disclosure, the case where the first retardation plate 5 and the second retardation plate 7 are quarter-wave plates will be described as an example.

[0028] Also, the second retardation plate 7 only needs to be given the necessary phase difference to the light transmitted through the second retardation plate 7 so that the light reflected by the reflective polarizing plate 8 and transmitted through the second retardation plate 7 reaches the reflective polarizing plate 8 again and passes through the reflective polarizing plate 8. That is, for example, when the polarization obtained by being reflected by the reflective polarizing plate 8 and transmitted through the second retardation plate 7 is taken as the first polarization, the second retardation plate 7 may not be a quarter-wave plate but another retardation plate as long as the first polarization is obtained.

[0029] As shown in FIG. 30, the first retardation plate 5 may be integrated with the display panel 2. Note that "integration" may mean that two members are arranged to be in contact with each other, or may mean that two members are joined to each other by an optically transparent adhesive such as OCA (Optically Clear Adhesive).

[0030] The semi-transmissive mirror 6 is positioned between the first retardation plate 5 and the second retardation plate 7. The semi-transmissive mirror 6 may transmit a part (e.g., approximately 50%) of the incident light and reflect the remaining part (e.g., approximately 50%). The semi-transmissive mirror 6 reflects a part of the display light reflected by the reflective polarizing plate 8 and makes it incident on the eyes of the user 22. Thereby, the user 22 can visually recognize the virtual image V. As shown in FIG. 2, the semi-transmissive mirror 6 may be a concave mirror having a concave reflective surface 6a facing the second retardation plate 7. The semi-transmissive mirror 6 may include a spherical shape, an aspherical shape, or a free-form surface shape at least in part of the reflective surface 6a.

[0031] The semi-transmissive mirror 6 is configured to include, for example, a base material and a semi-transmissive reflective layer located on the surface of the base material. The base material may have a transmittance of 100% or nearly 100% for light in the visible light band. The base material may be made of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The semi-transmissive reflective layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum, chromium, etc. The semi-transmissive reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, etc. The semi-transmissive mirror 6 may be configured to reflect light by the semi-transmissive reflective layer. The semi-transmissive reflective layer may be formed on the surface of the base material facing the second retardation plate 7.

[0032] The reflective polarizing plate 8 is positioned to face the surface of the second retardation plate 7 opposite to the surface facing the semi-transmissive mirror 6. In other words, the reflective polarizing plate 8 is positioned 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 may transmit a part of the incident light and reflect the remaining part. In this embodiment, the reflective polarizing plate 8 is configured to reflect polarized light (also referred to as P-wave polarization, second polarization) having a polarization axis perpendicular to the polarization axis of the display light and transmit polarized light (also referred to as S-wave polarization, first polarization) having a polarization axis parallel to the polarization axis of the display light. Thereby, the user 22 can visually recognize the virtual image V. As shown in FIG. 30, the reflective polarizing plate 8 may be integrated with the second retardation plate 7.

[0033] The reflective polarizing plate 8 may be, for example, a wire grid polarizer including a substrate and a plurality of metal fine wires (also referred to as a metal nanowire grid) located on the surface of the substrate. The substrate may have a transmittance of 100% or nearly 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, or the like. The metal fine wires may be composed of a metal material such as aluminum, chromium, titanium oxide, or the like. The metal fine wires may be arranged along one direction. The reflective polarizing plate 8 can transmit a light component vibrating in a direction orthogonal to the grid and can reflect a light component vibrating in a direction parallel to the grid.

[0034] The display device 1 includes a controller 43. The controller 43 is connected to each component of the display device 1 and controls each component. The controller 43 may control the irradiator 4. The controller 43 may control the display image to be displayed on the display panel 2 and the irradiator 4. The controller 43 may control the irradiator 4 based on the display image to be displayed on the display panel 2. The controller 43 may include one or more processors. The processor may include a general-purpose processor configured to load a specific program and execute a specific function, and a dedicated processor specialized for a specific process. The processor may include a PLD (Programmable Logic Device). The controller 43 may be either a SoC (System-on-a-Chip) or a SiP (System In a Package) in which one or more processors cooperate. The controller 43 includes a storage unit and may store various information or a program for operating each component of the display device 1 in the storage unit. The storage unit may be composed of, for example, a semiconductor memory or the like. The storage unit may function as a work memory of the controller 43.

[0035] The optical function of the optical system 3 will be described. The display panel 2 emits display light of S-wave polarization (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 semi-transmissive mirror 6. The first circularly polarized light C1 that has passed through the semi-transmissive 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 (that is, P-wave polarization). 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 P-wave polarization and transmits the light of S-wave polarization. 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 semi-transmissive 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 (that is, S-wave polarization). The light of the fourth linearly polarized light L4 passes through the reflective polarizing plate 8 and is emitted to the outside. The amount of light (luminance) of the light emitted from the display device 1 is, for example, approximately 25% of the amount of light (luminance) of the display light emitted from the display panel 2.

[0036] The first retardation plate 5, the semi-transmissive mirror 6, the second retardation plate 7, and the reflective polarizing plate 8 are held by a holding member (not shown), and their relative positions are maintained. Air is interposed between the first retardation plate 5 and the second retardation plate 7 (that is, between the first retardation plate 5 and the semi-transmissive mirror 6 and between the semi-transmissive mirror 6 and the second retardation plate 7). Since the display device 1 is configured not to provide a member made of a resin material such as a polymer between the first retardation plate 5 and the second retardation plate 7, deformation of the semi-transmissive mirror 6 and displacement between the semi-transmissive mirror 6 and the first retardation plate 5 and the second retardation plate 7 when curing the resin material during the manufacturing process of the display device 1 can be reduced. In addition, a resin material such as a polymer has a retardation peculiar to the material, and the possibility of changing the polarization state of the light transmitted through the resin material can also be reduced. As a result, a decrease in display quality can be reduced.

[0037] Since the optical system 3 is a uniaxial (on-axis) type optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the 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 uniaxial type, distortion, uneven brightness, etc. of the virtual image V viewed by the user 22 can be reduced, and the design of the optical system 3 becomes easier.

[0038] In the display device 1, the optical path length of the light emitted from the display panel 2, transmitted through the semi-transmissive mirror 6, reflected by the reflective polarizing plate 8, and reaching the semi-transmissive mirror 6 may be smaller than the focal length of the semi-transmissive mirror 6. In this case, the user 22 can view the virtual image V. In the display device 1, the optical path length of the light emitted from the display panel 2, transmitted through the semi-transmissive mirror 6, reflected by the reflective polarizing plate 8, and reaching the semi-transmissive mirror 6 may be larger than the focal length of the semi-transmissive mirror 6. In this case, the user 22 can view a real image.

[0039] In FIG. 2, for the sake of easy illustration, 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 shifted in the height direction (Y-axis direction), and the optical path of the light incident on the semi-transmissive mirror 6 and the optical path of the light reflected by the semi-transmissive mirror 6 are shifted in the height direction (Y-axis direction) and shown. However, actually, the display light emitted from the display panel 2 propagates substantially on a single axis, as shown in FIG. 37. This also applies to the optical paths shown in FIGS. 3 to 5, 9, 15, 16, 20 to 22, 24, 30 to 32.

[0040] As shown in FIG. 38, the display device 1 may replace the first retardation plate 5, the semi-transmissive mirror 6, the second retardation plate 7, and the reflective polarizing plate 8 with a convex lens 42. The optical path length from the display panel 2 to the convex lens 42 of the display device 1 may be smaller than the focal length of the convex lens 42. In this case, the virtual image V of the user 22 can be visually recognized. The optical path length from the display panel 2 to the convex lens 42 of the display device 1 may be larger than the focal length of the convex lens 42. In this case, the real image of the user 22 can be visually recognized.

[0041] The display panel 2 may display a mixed image including a left-eye image and a right-eye image having a parallax with each other and emit the display light of the mixed image. As shown in FIG. 3, the display device 1 may include an optical element 9 located on 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 define the light ray directions of the display light of the left-eye image and the display light of the right-eye image, so that at least a part of the display light of the left-eye image reaches the left eye of the user 22 and at least a part of the display light of the right-eye image reaches the right eye of the user 22. Thereby, the display device 1 can enable the user 22 to visually recognize a stereoscopic image.

[0042] The optical element 9 only needs to be able to make a part of the display light of the mixed image reach one of the left and right eyes of the user 22 and make the other part of the display light reach the other of the left and right eyes of the user 22. For example, it may be a parallax barrier or a lenticular lens. The parallax barrier may be composed of a liquid crystal panel. The position of the optical element 9 is arbitrary inside the display device 1. The optical element 9 may be located between the display panel 2 and the first retardation plate 5, may be located at the subsequent stage of the reflective polarizing plate 8 in the emission direction of the display light, or may be located between the semi-transparent mirror 6 and the second retardation plate 7.

[0043] Next, a display device according to another embodiment of the present disclosure will be described. The display device of this embodiment has a different optical system configuration from the display device of the above embodiment, and the other configurations are the same. Therefore, for the same configurations, the same reference numerals are attached and the detailed description is omitted.

[0044] As shown in FIG. 4, the display device 1A of this embodiment includes a display panel 2 and an optical system 10. The display panel 2 has a display surface 2a and displays a display image on the display surface 2a. The optical system 10 projects the display light emitted from the display panel 2 as a virtual image V within the visual field of the user 22.

[0045] The optical system 10 includes a first semi-transparent mirror 11, a first retardation plate 12, a second semi-transparent mirror 13, a second retardation plate 14, and a polarizing plate 15. The first semi-transparent mirror 11, the first retardation plate 12, the second semi-transparent mirror 13, the second retardation plate 14, and the polarizing plate 15 are arranged in this order in the emission direction of the display light from the display panel 2.

[0046] The first retardation plate 12 is located opposite to the reflection surface 11a of the first semi-transparent mirror 11. The first retardation plate 12 is located 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 14 is located at a distance 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.

[0047] The first semi-transmissive mirror 11 is positioned between the display panel 2 and the first retardation plate 12. The first semi-transmissive mirror 11 may transmit a part of the incident light and reflect the remaining part. As shown in FIG. 4, the first semi-transmissive mirror 11 is a concave mirror having a concave reflecting surface 11a facing the first retardation plate 12. In the present embodiment, the first semi-transmissive mirror 11 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. The first semi-transmissive mirror 11 may include a spherical shape, an aspherical shape, or a free-form surface shape on at least a part of the reflecting surface 11a.

[0048] The first semi-transmissive mirror 11 may be configured to include, for example, a base material and a plurality of metal fine wires (metal nanowire grids) located on the surface of the base material. The base material may have a transmittance of 100% or nearly 100% for light in the visible light band. The base material 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 semi-transmissive mirror 11 can transmit a light component vibrating in a direction orthogonal to the grid and reflect a light component vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the base material on the side of the first retardation plate 12. In this example, the metal nanowire grid imparts the function of reflected polarization to the first semi-transmissive mirror 11, but the first semi-transmissive mirror 11 may be used as a simple half mirror, and a separate reflected polarizing plate may be provided.

[0049] The second semi-transmissive mirror 13 is positioned between the first retardation plate 12 and the second retardation plate 14. The second semi-transmissive mirror 13 may transmit a part of the incident light (for example, approximately 50%) and reflect the remaining part (for example, approximately 50%). As shown in FIG. 4, the second semi-transmissive mirror 13 may be a plane mirror positioned such that the reflecting surface 13a faces the first retardation plate 12. The second semi-transmissive mirror 13 is also referred to as a plane half mirror. As shown in FIG. 31, the second semi-transmissive mirror 13 may be integrated with the first retardation plate 12 and / or the second retardation plate 14.

[0050] The second semi-transmissive mirror 13 may be configured to include, for example, a substrate and a semi-transmissive reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or nearly 100% with respect to light in the visible light band. The substrate may be made of, for example, inorganic glass, resin material, or the like. The resin material may be, for example, acrylic resin, polycarbonate resin, or the like. The semi-transmissive reflective layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum, chromium, or the like. The semi-transmissive reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film or the like.

[0051] The polarizing plate 15 is positioned to face the surface of the second retardation plate 14 opposite to the surface facing the second semi-transmissive mirror 13. In other words, the polarizing plate 15 is located at the rear stage of the second retardation plate 14 in the emission direction of the display light from the display panel 2. The polarizing plate 15 may transmit a part of the incident light and absorb the remainder. In the present embodiment, the polarizing plate 15 is configured to transmit P-wave polarized light and absorb S-wave polarized light. As shown in FIG. 31, the polarizing plate 15 may be integrated with the second retardation plate 14.

[0052] The polarizing plate 15 may have the configuration of a known absorption type polarizing plate. The known absorption type polarizing plate may 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, or the like.

[0053] The optical function of the optical system 10 will be described. The display light of the S-wave polarization (the 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 the first circular polarization C1. The light of the first circular polarization C1 is incident on the second half-transmissive mirror 13. A part of the light of the first circular polarization C1 (for example, approximately 50%) is reflected by the second half-transmissive mirror 13 and converted into light of the second circular polarization C2. The light of the second circular polarization C2 passes through the first retardation plate 12 and is converted into light of the second linearly polarized light L2 whose polarization direction is orthogonal to the first linearly polarized light L1 (that is, P-wave polarization). The light of the second linearly polarized light L2 is reflected by the first half-transmissive mirror 11 and converted into light of the third linearly polarized light L3 whose polarization direction is orthogonal to 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 the third circular polarization C3. A part of the light of the third circular polarization C3 (for example, approximately 50%) passes through the second half-transmissive mirror 13. The light of the third circular polarization C3 that has passed through the second half-transmissive mirror 13 passes through the second retardation plate 14 and is converted into light of the fourth linearly polarized light L4 whose polarization direction is orthogonal to the first linearly polarized light L1 (that 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.

[0054] The remaining part of the light of the first circular polarization C1 (for example, approximately 50%) passes through the second half-transmissive mirror 13 and then passes through the second retardation plate 14 and is converted into light of the fifth linearly polarized light L5 whose polarization direction is parallel to the first linearly polarized light L1 (that is, S-wave polarization). Since the light of the fifth linearly polarized light L5 is absorbed by the polarizing plate 15, it is not emitted to the outside. In other words, the light of the fifth linearly polarized light L5 is light with low transmittance through the polarizing plate 15. Therefore, the light quantity (luminance) of the light emitted from the display device 1A is, for example, approximately 25% of the light quantity (luminance) of the display light emitted from the display panel 2.

[0055] In the above description, an example where the first retardation plate 12 and the second retardation plate 14 are quarter-wave plates has been described. However, if some light is absorbed by the polarizing plate 15 and the other light is transmitted through the polarizing plate 15, the first retardation plate 12 and the second retardation plate 14 may not be quarter-wave plates, but other retardation plates or combinations thereof. Also, if some light is reflected by the first semi-transmissive mirror 11 and the other light is transmitted through the first semi-transmissive mirror 11, the first retardation plate 12 and the second retardation plate 14 may not be quarter-wave plates, but other retardation plates or combinations thereof.

[0056] The first semi-transmissive mirror 11, the first retardation plate 12, the second semi-transmissive mirror 13, the second retardation plate 14, and the polarizing plate 15 are held by a holding member (not shown), whereby their relative positions are maintained. Air is interposed between the first semi-transmissive mirror 11 and the first retardation plate 12. Since the display device 1A is configured not to provide a member made of a resin material such as a polymer between the first semi-transmissive mirror 11 and the first retardation plate 12, it is possible to reduce the risk of deformation of the first semi-transmissive mirror 11 and misalignment between the first semi-transmissive mirror 11 and the first retardation plate 12 when curing the resin material during the manufacturing process of the display device 1A. As a result, it is possible to reduce a decrease in display quality.

[0057] Since the optical system 10 is a uniaxial (on-axis) optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the occupied space of the optical system 10 can be reduced, and as a result, the display device 1A can be miniaturized. Also, since the optical system 10 is of the uniaxial type, it is possible to reduce distortion, uneven brightness, etc. of the virtual image V viewed by the user 22, and the design of the optical system 10 becomes easier.

[0058] Similar to the display device 1, the display device 1A may include the optical element 9. In this case, the display device 1A can allow the user 22 to view a stereoscopic image. The optical element 9 may be located between the display panel 2 and the first semi-transmissive mirror 11, may be located downstream 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 retardation plate 12.

[0059] Next, another example of the display device 1A will be described. The display device 1A' in this example has a different configuration (shape) of the second semi-transmissive mirror from that of the above-described display device 1A, and the other configurations are the same. Therefore, for the same configurations, the same reference numerals are given and detailed descriptions are omitted.

[0060] As shown in FIG. 5, the display device 1A' in this example includes a display panel 2 and an optical system 10. The optical system 10 includes a first semi-transmissive mirror 11, a first retardation plate 12, a second semi-transmissive mirror 13', a second retardation plate 14, and a polarizing plate 15. The first semi-transmissive mirror 11, the first retardation plate 12, the second semi-transmissive mirror 13', the second retardation plate 14, and the polarizing plate 15 are arranged in this order in the emission direction of the display light from the display panel 2.

[0061] The second semi-transmissive mirror 13' has a convex reflecting surface 13'a, and the reflecting surface 13'a faces the first retardation plate 12. The second semi-transmissive mirror 13' is also referred to as a convex half mirror. The second semi-transmissive mirror 13' may transmit a part (for example, approximately 50%) of the incident light and reflect the remaining part (for example, approximately 50%).

[0062] The second semi-transmissive mirror 13' may be configured to include, for example, a substrate and a semi-transmissive reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or nearly 100% for 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 reflective layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum, chromium, etc. The semi-transmissive reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, etc.

[0063] The optical system 10 may be configured such that the focal length of the second half-transmissive mirror 13' is greater than the distance between the display panel 2 and the second half-transmissive mirror 13'. In other words, the optical system 10 may be configured such that the second half-transmissive mirror 13' projects a reduced virtual image Q' (see FIG. 7) of the object (i.e., the display surface 2a). Further, the optical system 10 may be configured such that the focal length of the first half-transmissive mirror 11 is greater than the distance between the virtual image Q' and the first half-transmissive mirror 11. In other words, the optical system 10 may be configured such that the first half-transmissive mirror 11 projects an enlarged virtual image V of the object (i.e., the virtual image Q'). In this case, it is possible to adjust the magnification and projection distance of the virtual image V while reducing the thickness of the optical system 10 in the depth direction (Z-axis direction).

[0064] 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), whereby their relative positions are maintained. Air is interposed between the first half-transmissive mirror 11 and the first retardation plate 12. Since the display device 1A' is configured not to provide a member made of a resin material such as a polymer between the first half-transmissive mirror 11 and the first retardation plate 12, it is possible to reduce the risk of deformation of the first half-transmissive mirror 11 and misalignment between the first half-transmissive mirror 11 and the first retardation plate 12 when curing the resin material during the manufacturing process of the display device 1A'. As a result, it is possible to reduce the degradation of the display quality.

[0065] Since the optical system 10 is a uniaxial (on-axis) optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the occupied space of the optical system 10 can be reduced, and as a result, the display device 1A' can be miniaturized. Further, since the optical system 10 is of the uniaxial type, it is possible to reduce distortion, uneven brightness, etc. of the virtual image V viewed by the user 22, and the design of the optical system 10 becomes easier.

[0066] The display device 1A' may include the optical element 9, and in this case, it is possible to allow the user 22 to view the stereoscopic virtual image V.

[0067] In addition, according to the display device 1A' of this example, since the optical system 10 can be thinned in the depth direction (Z-axis direction), a thin display device can be provided. Hereinafter, with reference to FIGS. 6 and 7, the thinning of the optical system 10 will be described. Note that, since the reflecting surface of the first half-transmissive mirror 11 of the display devices 1A and 1A' that reflects the display light emitted to the outside is the concave reflecting surface 11a, hereinafter, the first half-transmissive mirror 11 may be referred to as a concave mirror. Since the reflecting surface of the second half-transmissive mirror 13 of the display device 1A that reflects the display light emitted to the outside is the planar reflecting surface 13a, hereinafter, the second half-transmissive mirror 13 may be referred to as a plane mirror. Since the reflecting surface of the second half-transmissive mirror 13' of the display device 1A' that reflects the display light emitted to the outside is the convex reflecting surface 13'a, hereinafter, the second half-transmissive mirror 13' may be referred to as a convex mirror. Also, the dimension of the optical system 10 in the depth direction (Z-axis direction) may be referred to as the thickness of the optical system 10.

[0068] FIG. 6 is a diagram for explaining the projection of the virtual image V in the display device 1A. In FIG. 6, the irradiator 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. Also, 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 as f, and the distance between the concave mirror 11 and the plane mirror 13 is set as a / 2. The distance a / 2 corresponds to the thickness of the optical system 10 of the display device 1A.

[0069] The display device 1A is configured to enlarge the virtual image Q of the display surface 2a by the plane mirror 13 and project it as the virtual image V by the concave mirror 11. As shown in FIG. 6, 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 is an image obtained by magnifying the display surface 2a at the same magnification (1 time).

[0070] The virtual image distance b and the virtual image magnification m of the virtual image V are represented by the following equations (1) and (2), respectively. Note 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. b = 1 / (1 / a - 1 / f) …(1) m = b / a …(2)

[0071]

Table 1

[0072] Table 1 shows Configuration 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". Configuration Examples 1 and 2 are configured such that the virtual image distance b is 200 mm and the virtual image magnification m is 2 or 3. As shown in Table 1, when the optical system 10 includes the plane mirror 13, in order to make the virtual image distance b 200 mm and the virtual image magnification m 2, it is necessary to make the thickness a / 2 of the optical system 10 50 mm (see Configuration Example 1). In order to make the virtual image distance b 200 mm and the virtual image magnification m 3, it is necessary to make the thickness a / 2 of the optical system 10 33.5 mm (see Configuration Example 2).

[0073] FIG. 7 is a diagram for explaining the projection of the virtual image V in the display device 1A'. In FIG. 7, the irradiator 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. Further, 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 denoted as f', the focal length of the concave mirror 11 is denoted as f'', and the distance between the concave mirror 11 and the convex mirror 13' is denoted as a' / 2. The distance a' / 2 corresponds to the thickness of the optical system 10 of the display device 1A'.

[0074] The display device 1A’ is configured to magnify the virtual image Q’ of the display surface 2a by the convex mirror 13’ and project it as a virtual image V by the concave mirror 11. As shown in Fig. 7, the virtual image Q’ is located on the opposite side of the concave mirror 11 with respect to the convex mirror 13’. The distance b’ between the virtual image Q’ and the convex mirror 13’ is represented by the following formula (3). The magnification m’ of the virtual image Q’ with respect to the display surface 2a is represented by the following formula (4). As is clear from formula (3), since b’ < a’ / 2, the magnification m’ of the virtual image Q’ is less than 1. Therefore, the virtual image Q’ is a reduced virtual image of the display surface 2a. b’ = 1 / {1 / f’ + 1 / (a’ / 2)} …(3) m’ = b’ / (a’ / 2) …(4)

[0075] 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. Note 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. b’’ = 1 / {1 / (a’ / 2 + b’) - 1 / f’’} …(5) m’’ = (b’ / (a’ / 2)) × b’’ / (a’ / 2 + b’) …(6)

[0076] Table 2 shows Configuration Examples 3 and 4 of the display device 1A’. The units of the focal lengths f’ and f’’, the thickness a’ / 2, and the virtual image distance b’’ shown in Table 2 are “mm”. Similar to Configuration Examples 1 and 2, Configuration Examples 3 and 4 are configured such that the virtual image distance b’’ is 200 mm and the virtual image magnification m’’ is 2 or 3. As shown in Table 2, when the optical system 10 includes the convex mirror 13’, with the optical system 10 having a thickness a’ / 2 of 32 mm, similar to Configuration Example 1, the virtual image distance b’’ can be set to 200 mm and the virtual image magnification m’’ can be set to 2 (see Configuration Example 3). With the optical system 10 having a thickness a’ / 2 of 25.5 mm, similar to Configuration Example 2, the virtual image distance b’’ can be set to 200 mm and the virtual image magnification m’’ can be set to 3 (see Configuration Example 4). Therefore, according to the display device 1A’, the optical system 10 can be thinned, and as a result, a thin display device can be provided.

[0077]

Table 2

[0078] When the values of the virtual image distance b'', the virtual image magnification m'', and the thickness a' / 2 are given, the display device 1A' can design the optical system 10 so as to realize them.

[0079] Hereinafter, with reference to FIG. 8, the design of the optical system 10 of the display device 1A' will be described. In FIG. 8, similar to FIG. 7, the irradiator 4, the first retardation plate 12, the second retardation plate 14, and the polarizing plate 15 are omitted. Further, 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 denoted as a1, the distance between the convex mirror 13' and the virtual image Q' is denoted as b1, and the distance between the concave mirror 11 and the virtual image V is denoted as b2. Further, the magnification of the virtual image Q' with respect to the display surface 2a is denoted as m1, and the magnification of the virtual image V with respect to the virtual image Q' is denoted as m2. Furthermore, the focal length of the convex mirror 13' is denoted as f1, and the focal length of the concave mirror 11 is denoted as f2.

[0080] The magnification M of the virtual image V with respect to the display surface 2a is represented by 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 represented by the sum of the thickness a1 and the distance b1, as shown in the following formula (8). M = m1 × m2 …(7) a2 = a1 + b1 …(8)

[0081] Defining the thickness a1 of the optical system 10 as T and the virtual image distance (that is, the distance b1 between the concave mirror 11 and the virtual image V) as D, the magnification M is represented by the following formula (9). M = m1 × m2 = (b1 / a1) × (b2 / a2) = (b1 / T) × (D / a2) …(9)

[0082] As a result of substituting the following formula (10) that holds for the distance b1 between the convex mirror 13' and the virtual image Q' into formula (9), the following formula (11) is obtained. 1 / a1 = 1 / b1 + 1 / f1 …(10) M = f1×(1 + D / f2) / (T + f1) …(11)

[0083] Also, as a result of substituting the following equation (12) that holds for the distance b2 between the concave mirror 11 and the virtual image V into equation (8), the following equation (13) is obtained. 1 / a2 = 1 / b2 + 1 / f2 …(12) D×f2 / (D + f2) = T + T×f1 / (T + f1) …(13)

[0084] From equations (9) and (13), as shown in the following equations (14) and (15), the focal length f1 of the convex mirror 13’ and the focal length f2 of the concave mirror 11 are obtained. Note that A in equation (15) is represented by the following equation (16). f1 = M×T×T / (D - 2×M×T) …(14) f2 = D×A / (M - A) …(15) A = f1 / (T + f1) …(16)

[0085] As can be seen from the above calculations, when the values of the magnification M, the thickness T, and the virtual image distance D are given, the display device 1A’ can determine the focal lengths f1 and f2 (i.e., design the optical system 10) so as to realize them.

[0086] For the display devices 1A and 1A’, the optical path length of the light that is emitted from the display panel 2, passes 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 may be smaller than the focal length of the first half-transmissive mirror 11. In this case, the user 22 can visually recognize the virtual image V. For the display devices 1A and 1A’, the optical path length of the light that is emitted from the display panel 2, passes 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 may be larger than the focal length of the first half-transmissive mirror 11. In this case, the user 22 can visually recognize the real image.

[0087] Next, a display device according to still another embodiment of the present disclosure will be described. The display device of the present embodiment has a different optical system configuration from the display device of the above embodiment, and the other configurations are the same. Therefore, for the same configurations, the same reference numerals are given, and detailed descriptions thereof are omitted.

[0088] As shown in FIG. 9, the display device 1B of the present embodiment includes a display panel 2 and an optical system 16.

[0089] The optical system 16 includes a first half mirror 17, a first retardation plate 18, a second half mirror 19, a second retardation plate 20, and a third half mirror 21. The first half mirror 17, the first retardation plate 18, the second half mirror 19, the second retardation plate 20, and the third half mirror 21 are arranged in this order in the emission direction of the display light from the display panel 2.

[0090] The first retardation plate 18 is positioned to face the reflection surface 17a of the first half mirror 17. The first retardation plate 18 is positioned away from the display surface 2a in the emission direction of the display light from the display panel 2. The second retardation plate 20 is positioned away from the first retardation plate 12 in the emission direction of the display light. The first retardation plate 18 and the second retardation plate 20 are quarter-wave plates.

[0091] The first half mirror 17 is positioned between the display panel 2 and the first retardation plate 18. The first half mirror 17 may transmit a part of the incident light and reflect the remaining part. In the present embodiment, the first half mirror 17 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. As shown in FIG. 9, the first half mirror 17 may be a concave mirror having a concave reflection surface 17a facing the first retardation plate 18. The first half mirror 17 may include a spherical shape, an aspherical shape, or a free-form surface shape at least in part of the reflection surface 17a.

[0092] The first semi-transmissive mirror 17 is configured to include, for example, a base material and a plurality of metal fine wires (metal nanowire grids) located on the surface of the base material. The base material may have a transmittance of 100% or nearly 100% with respect to light in the visible light band. The base material 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 semi-transmissive mirror 17 can transmit the light component vibrating in the direction orthogonal to the grid and can reflect the light component vibrating in the direction parallel to the grid. The metal nanowire grid may be formed on the surface of the base material facing the first retardation plate 18. In this example, the metal nanowire grid imparts the function of reflection polarization to the first semi-transmissive mirror 11. However, the first semi-transmissive mirror 11 may be used as a mere half mirror, and a reflection polarizing plate may be provided separately.

[0093] 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 may transmit a part of the incident light (for example, approximately 50%) and reflect the remaining part (for example, approximately 50%). As shown in FIG. 9, the second semi-transmissive mirror 19 may be a plane mirror having a reflection surface 19a facing the first retardation plate 18 and a reflection surface 19b facing the second retardation plate 20. The second semi-transmissive mirror 19 is also referred to as a plane half mirror. As shown in FIG. 32, the second semi-transmissive mirror 19 may be integrated with the first retardation plate 18 and / or the second retardation plate 20.

[0094] 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 nearly 100% with respect to light in the visible light band. The substrate may be made of, for example, inorganic glass, resin material, or the like. The resin material may be, for example, acrylic resin, polycarbonate resin, or the like. The semi-transmissive layer may be a metal thin film. The metal thin film may be made of a metal material such as aluminum, chromium, or the like. The semi-transmissive layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film or the like. The first retardation plate 18 and the second retardation plate 20 may be fixed to the second semi-transmissive mirror 19 by an optically transparent adhesive such as OCA (Optically Clear Adhesive). The adhesive may be a material with a small retardation.

[0095] The third semi-transmissive mirror 21 is positioned to face the surface of the second retardation plate 20 opposite to the surface facing the second semi-transmissive mirror 19. The third semi-transmissive mirror 21 is located at the rear stage of the second retardation plate 20 in the emission direction of the display light from the display panel 2. The third semi-transmissive mirror 21 may transmit a part of the incident light and reflect the remainder. In the present embodiment, the third semi-transmissive mirror 21 may be configured to reflect light with S-wave polarization and transmit light with P-wave polarization. As shown in FIG. 9, the third semi-transmissive mirror 21 may be a concave mirror having a concave reflective surface 21a facing the second retardation plate 20. The third semi-transmissive mirror 21 may include at least a part of the reflective surface 21a having a spherical shape, an aspherical shape, or a free-form surface shape.

[0096] The third semi-transmissive mirror 21 is 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 nearly 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 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 third semi-transmissive mirror 21 can transmit the light component vibrating in the direction orthogonal to the grid and can reflect the light component vibrating in the direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate facing the second retardation plate 20. In this example, the metal nanowire grid imparts the function of reflection polarization to the third semi-transmissive mirror 21. However, the third semi-transmissive mirror 21 may be used as a mere half mirror, and a reflection polarizing plate may be provided separately.

[0097] 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 may travel along the path P1 or the path P2 and be emitted to the outside. First, the light traveling along the path P1 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 17. The light of the first linearly polarized light L1 passes through the first retardation plate 18 and is converted 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 converted 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 converted 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, P-wave polarization). The light of the second linearly polarized light L2 is reflected by the first half-transmissive mirror 17 and converted 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, P-wave polarization). The third linearly polarized light L3 passes through the first retardation plate 18 and is converted 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 converted 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, P-wave polarization). The light of the fourth linearly polarized light L4 passes through the third half-transmissive mirror 21 and is emitted to the outside.

[0098] Next, the light traveling along path P2 will be described. The remaining part (e.g., approximately 50%) of the light of the first circular polarization C1 incident on the second semi-transmissive mirror 19 passes through the second semi-transmissive mirror 19. The light of the first circular polarization C1 that has passed through the second semi-transmissive mirror 19 passes through the second retardation plate 20 and is converted into light of the fifth linearly polarized light L5 whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarization). The light of the fifth linearly polarized light L5 is reflected by the third semi-transmissive mirror 21 and is converted into light of the sixth linearly polarized light L6 whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarization). The light of the sixth linearly polarized light L6 passes through the second retardation plate 20 and is converted into light of the fourth circular polarization C4. The light of the fourth circular polarization C4 is incident on the second semi-transmissive mirror 19. A part (e.g., approximately 50%) of the light of the fourth circular polarization C4 is reflected by the second semi-transmissive mirror 19 and is converted into light of the fifth circular polarization C5. The light of the fifth circular polarization C5 passes through the second retardation plate 20 and is converted into light of the seventh linearly polarized light L7 whose polarization direction is orthogonal to the first linearly polarized light L1 (i.e., P-wave polarization). The light of the seventh linearly polarized light L7 passes through the third semi-transmissive mirror 21 and is emitted to the outside.

[0099] As described above, in the display device 1B, the display light emitted from the display panel 2 travels along path P1 or path P2 and is emitted to the outside. As a result, the amount of light (luminance) of the light emitted from the display device 1B becomes, for example, approximately 50% of the amount of light (luminance) of the display light emitted from the display panel 2. The display device 1B can improve the light utilization efficiency and can improve the luminance of the light emitted to the outside.

[0100] Note 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, if some light is reflected by the first semi-transmissive mirror 17 and the other light passes through the first semi-transmissive mirror 17, the first retardation plate 18 and the second retardation plate 20 may not be quarter-wave plates but other retardation plates or combinations thereof. Also, if some light is reflected by the third semi-transmissive mirror 21 and the other light passes through the third semi-transmissive mirror 21, the first retardation plate 18 and the second retardation plate 20 may not be quarter-wave plates but other retardation plates or combinations thereof.

[0101] The first semi-transmissive mirror 17, the first retardation plate 18, the second semi-transmissive mirror 19, the second retardation plate 20, and the third semi-transmissive mirror 21 are held by a holding member (not shown), whereby their relative positions to each other are maintained. Air is interposed between the first semi-transmissive mirror 17 and the first retardation plate 18, and between the third semi-transmissive mirror 21 and the second retardation plate 20. Since the display device 1B is configured not to provide a member made of a resin material such as a polymer between the first semi-transmissive mirror 17 and the first retardation plate 18, and between the third semi-transmissive mirror 21 and the second retardation plate 20, it is possible to reduce the risk of deformation of the first semi-transmissive mirror 11, misalignment between the first semi-transmissive mirror 11 and the first retardation plate 12, etc. As a result, it is possible to reduce the degradation of display quality.

[0102] Since the optical system 16 is a uniaxial (on-axis) optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the occupied space of the optical system 16 can be reduced, and as a result, the display device 1B can be miniaturized. Further, since the optical system 16 is a uniaxial type, it is possible to reduce distortion, uneven brightness, etc. of the virtual image V viewed by the user 22, and the design of the optical system 16 becomes easier.

[0103] The display device 1B may be configured such that the focal length of the first semi-transmissive mirror 17 is equal to the focal length of the third semi-transmissive mirror 21, and the second semi-transmissive mirror 19 is a plane mirror. In this case, in the imaging device including the display device 1B, since 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 substantially coincide, the display quality can be improved.

[0104] The display device 1B is configured such that the optical path length of the light emitted from the display panel 2, passing through the first half-transmissive mirror 17, being reflected by the second half-transmissive mirror 19, and reaching the first half-transmissive mirror 17 is smaller than the focal length of the first half-transmissive mirror 17, and the optical path length of the light emitted from the display panel 2, passing through the first half-transmissive mirror 17, passing through the second half-transmissive mirror 19, and reaching the third half-transmissive mirror 21 may be smaller than the focal length of the first half-transmissive mirror 17. In this case, the user 22 can visually recognize the virtual image V. The display device 1B is configured such that the optical path length of the light emitted from the display panel 2, passing through the first half-transmissive mirror 17, being reflected by the second half-transmissive mirror 19, and reaching the first half-transmissive mirror 17 is larger than the focal length of the first half-transmissive mirror 17, and the optical path length of the light emitted from the display panel 2, passing through the first half-transmissive mirror 17, passing through the second half-transmissive mirror 19, and reaching the third half-transmissive mirror 21 may be larger than the focal length of the first half-transmissive mirror 17. In this case, the user 22 can visually recognize a real image.

[0105] Next, an imaging device according to an embodiment of the present disclosure will be described. The imaging device 100 of this embodiment includes display devices 1, 1A, 1A', and 1B. The imaging device 100 causes the user 22 to visually recognize the display light emitted from the display panel 2 as a virtual image V. Since the imaging device 100 includes the display devices 1, 1A, 1A', and 1B, a compact imaging device can be realized, and the user 22 can visually recognize 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 may cause the user 22 to visually recognize the display light emitted from the display panel 2 as a real image.

[0106] As shown in FIG. 10, the imaging device 100 may be mounted on the moving body 23. The moving body 23 may be a vehicle. FIG. 10 shows the case where the vehicle is a passenger car, but the vehicle is not limited to a passenger car and may be an automobile such as a truck, a bus, and a trolley bus. The positions of the display devices 1, 1A, 1A', 1B are arbitrary inside the moving body 23. The display devices 1, 1A, 1A', 1B may be located on the dashboard (instrument panel), inside the dashboard, on the ceiling of the passenger compartment, on the A-pillar, etc. A part of the configuration of the imaging device 100 may be shared with other devices and components provided in the moving body 23.

[0107] As shown in FIG. 10, the imaging device 100 may include a camera 102 that images the rear view of the moving body 23. The camera 102 may include, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging device 100 and the camera 102 are connected by 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 a CAN (Control Area Network).

[0108] 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 cause the user 22 (the driver of the moving body 23) to visually recognize the rear view of the moving body 23 as a virtual image V imaged on the side farther from the imaging device 100. As a result, the user 22 can visually recognize the rear view of the moving body 23 without significantly changing the fixation distance (fixation point) during driving of the moving body 23, so that the virtual image V is easier to visually recognize and the driving safety can be improved. In addition, since the imaging device 100 is a small imaging device, even if it is arranged in the driver's cab of the moving body 23, it does not occupy a large volume in the driver's cab and is unlikely to interfere with driving. The imaging device 100 mounted on the moving body 23 and configured to cause the user 22 to visually recognize the rear view of the moving body 23 as the virtual image V is also referred to as a digital rearview mirror.

[0109] The imaging device 100 may include the display devices 1, 1A, 1A', 1B with the optical element 9 (see FIG. 3). The imaging device 100 may be configured such that the display panel 2 displays a mixed image including a left-eye image and a right-eye image having parallax with respect to each other, emits display light of the left-eye image and display light of the right-eye image, and 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 recognized by the user 22 as a stereoscopic virtual image V.

[0110] As shown in FIG. 11, the imaging device 100 may include a reflective optical element 101. The imaging device 100 may be configured such that the display devices 1, 1A, 1A', 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 may also use the windshield 24 of the moving body 23 as the reflective optical element 101.

[0111] The imaging device 100 may be applied to a digital side mirror. In this case, as shown in FIG. 12, the imaging device 100 may include a display device 1, 1A, 1A’, 1B (hereinafter also referred to as the left display device 1L) located on the A-pillar on the left side of the moving body 23, a camera 102 that images the rear left side of the moving body 23 (hereinafter also referred to as the left camera 102L), a display device 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 that images the rear right side of the moving body 23 (hereinafter also referred to as the right camera 102R). The left display device 1L may allow the user 22 to visually recognize an image of the rear left side of the moving body 23 captured by the left camera 102L as a virtual image V (hereinafter also referred to as virtual image V2). The right display device 1R may allow the user 22 to visually recognize an image of the rear right side of the moving body 23 captured by the right camera 102R as a virtual image V (hereinafter also referred to as virtual image V3). Note that the image may be a moving image (also referred to as video) or a still image. The left camera 102L may be located at a position similar to that of the left door mirror, and the right camera 102R may be located at a position similar to that of the right door mirror.

[0112] The imaging device 100 may be configured such that the distances between the eyes (or eye boxes) of the user 22 and the virtual images V2 and V3 are substantially the same. In this case, the user 22 can check the situations on the rear left side and the rear right side of the moving body 23 without significantly changing the fixation distance (the distance between the eyes of the user 22 and the fixation point on which the user 22 is fixating). Therefore, the driving safety can be improved. Note that the eye box means a region in the real space where the eyes of the user 22 are assumed to exist.

[0113] The imaging device 100 may be configured such that the distances between the eyes (or eye boxes) of the user 22 and the virtual images V1 to V3 are substantially the same. In this case, the user 22 can check the situations directly behind, on the rear left side, and on the rear right side of the moving body 23 without significantly changing the fixation distance. Therefore, the driving safety can be improved.

[0114] The imaging device 100 may be applied to the cluster 29 in the dashboard of the moving body 23 (see FIG. 12). In this case, the display devices 1, 1A, 1A', 1B may cause the user 22 to visually recognize an image indicating information related to driving, such as vehicle speed, engine rotation speed, remaining fuel amount, etc., as a virtual image V (hereinafter also referred to as virtual image V4).

[0115] The imaging device 100 may be applied to the CID (Center Information Display) 30 (see FIG. 12). In this case, the display devices 1, 1A, 1A', 1B are arranged in the center cluster of the moving body 23, and may cause the user 22 to visually recognize an image indicating information related to navigation, in-vehicle environment (for example, settings of an air conditioner, an audio device, etc.) as a virtual image V (hereinafter also referred to as virtual image V5).

[0116] The imaging device 100 may be configured such that the distances between the eyes (or the eye boxes) of the user 22 and the respective virtual images V4 and V5 are substantially the same. In this case, the user 22 can check information related to the operation 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.

[0117] The imaging device 100 may be configured such that the distances between the eyes (or the eye boxes) of the user 22 and the respective virtual images V1 to V5 are substantially the same. In this case, the user 22 can check the directly rear, left rear, and right rear of the moving body 23 without significantly changing the fixation distance, and can also check information related to the operation of the moving body 23, navigation, in-vehicle environment, etc. Therefore, the driving safety can be improved.

[0118] The imaging device 100 may be applied to the PID (Passenger Information Display) 31 (see FIG. 12). In this case, the display devices 1, 1A, 1A', 1B are arranged near the passenger seat in the dashboard, and may cause the passenger to visually recognize an image showing the video of entertainment content and the video showing information related to an audio device, an air conditioner, etc. as a virtual image V.

[0119] The imaging device 100 may be applied to an RSE (Rear Seat Entertainment) system 32 (see FIG. 10). In this case, the display devices 1, 1A, 1A', 1B are arranged on the back surface of the front seat, and the video of entertainment content and the video showing information about the audio device, air conditioner, etc. may be visually recognized as a virtual image V by the passengers sitting in the rear seats of the moving body 23.

[0120] The display devices 1, 1A, 1A', 1B may include a drive unit that adjusts the relative positions among the display panel 2, the semi-transparent mirror 6, the first semi-transparent mirrors 11, 17, and the second semi-transparent mirrors 13, 13', 21 in the depth direction. The image data of the display image displayed on the display panel 2 may include depth information representing the depth (distance in the depth direction) from the reference position. The reference position may be, for example, the position of the display panel 2. The virtual image display device 100 may be configured to adjust the distances among the display panel 2, the semi-transparent mirror 6, the first semi-transparent mirrors 11, 17, and the second semi-transparent mirrors 13, 13', 21 based on the depth information included in the image data, and change the imaging position of the virtual image V in the depth direction. The drive unit may be composed of, for example, an electric slider, an electric cylinder, etc. The drive unit may also be configured such that the user 22 can manually adjust the relative positions among the display panel 2, the semi-transparent mirror 6, the first semi-transparent mirrors 11, 17, and the second semi-transparent mirrors 13, 13', 21.

[0121] Hereinafter, other examples of the display device of the present disclosure will be described.

[0122] First, other examples of the display devices 1, 1A, 1A', 1B will be described. FIGS. 13 and 14 are top views showing other examples of the display device of the present disclosure. In FIGS. 13 and 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 described as an example, but the same applies to the display devices 1A, 1A', 1B.

[0123] The display device 1 may form part of an imaging device 100 (digital room mirror). In a normal room mirror, i.e., a room mirror using a mirror, the image viewed by the user's left eye (also referred to as the left-eye image) and the image viewed by the right eye (also referred to as the right-eye image) are different, and the user, through the cognitive function of the brain, recognizes the left-eye image and the right-eye image as the image viewed by both eyes.

[0124] The display device 1 may be configured such that the virtual image projected within the visual field of the user 22 has a binocular visible region (virtual image V in FIGS. 13 and 14) visible to the user 22's left eye 22L and right eye 22R, a left-eye visible region VLa visible only to the left eye 22L, and a right-eye visible region VRa visible only to the right eye 22R. In other words, when the virtual image viewed by the left eye 22L is the left-eye virtual image VL and the virtual image viewed by the right eye 22R is the right-eye virtual image VR, the left-eye virtual image VL may have a left-eye visible region VLa visible only to the left eye 22L, and the right-eye virtual image VR may have a right-eye visible region VRa visible only to the right eye 22R. Within the visual field 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. Also, as shown in FIG. 13, the display device 1 may be configured such that the right end 6R of the semi-transmissive mirror 6 visible to 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 visible to 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.

[0125] According to such a configuration, similar to the left-eye image and the right-eye image in a normal room mirror, the range observed by the user 22 through the left-eye virtual image VL and the range observed by the user 22 through the right-eye virtual image VR are different. Therefore, the user 22 can, 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 viewed by both eyes 22L and 22R, similar to the case of using a normal room mirror. Therefore, the possibility of causing discomfort to the user 22 can be reduced.

[0126] The display device 1 may be such that the size of the reflecting surface on the display surface 2a side in the reflective polarizing plate 8 is 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. Further, the display device 1 may be configured such that a virtual image (hereinafter also referred to as a display surface virtual image) VD when the image of the entire display surface 2a is projected within the visual field of the user 22 includes the left-eye virtual image VL and the right-eye virtual image VR. In this case, a region R that appears in the visual fields of the left eye 22L and the right eye 22R when the head of the user 22 moves, that is, a peeking region R that can be peeked into with the left eye 22L or the right eye 22R can be formed. As a result, the user 22 can visually recognize the left-eye virtual image VL and the right-eye virtual image VR that change according to the movement of the head, similar to the case of using a normal room mirror. Therefore, the possibility of causing discomfort to the user 22 can be reduced. The size (dimension) of the peeking region R can be controlled, for example, by controlling the size of the display surface 2a, the magnification of the virtual image, and the like.

[0127] It is also possible to control the size of the peeking region R by controlling the image display region (the region where the image is actually displayed) A on the display surface 2a. When the image display region A is enlarged, the peeking region R can be enlarged. When the image display region A is reduced, the peeking region R can be reduced. When the image display region A becomes smaller than a predetermined threshold region, the peeking region R disappears, and the left-eye virtual image VL and the right-eye virtual image VR can be made the same virtual image.

[0128] 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 peeking-in region R can also be controlled by the size of the opening 28. As shown in FIG. 14, by appropriately designing the size of the opening 28, a left-eye virtual image VL including a region where the right eye 22R cannot be visually recognized, and a right-eye virtual image VR including a region where the left eye 22L cannot be visually recognized can be formed. Also, by appropriately designing the size of the opening 28, the peeking-in region R can be formed and the size of the peeking-in region R can be controlled. When controlling the size of the peeking-in region R by the opening 28, the size of the semi-transmissive mirror 6 only needs to be such that it can project an image of the entire display surface 2a into the field of view of the user 22, which facilitates the design of the optical system 3.

[0129] 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 visually recognized by both the left eye 22L and the right eye 22R, a left-eye visible region visually recognized only by the left eye 22L, and a right-eye visible region visually recognized only by the right eye 22R. In this case, the possibility of causing discomfort to the user 22 can be reduced. In the display devices 1A and 1A', the right end visible to the user 22 in the first semi-transmissive mirror 11 may be located on the straight line connecting the left eye 22L and the right end of the left-eye virtual image, and the left end visible to the user 22 in the first semi-transmissive mirror 11 may be 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 visible to the user 22 in the first semi-transmissive mirror 17 and the third semi-transmissive mirror 21 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 visible to the user 22 in the first semi-transmissive mirror 17 and the third semi-transmissive mirror 21 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 peeking-in region R. The display devices 1A, 1A', and 1B may be configured such that the size of the peeking-in region R is controlled by the image display region A, or may be configured such that the size of the peeking-in region R is controlled by the opening 28 of the housing 27.

[0130] Next, other examples of the display devices 1, 1A, and 1A' will be described. FIGS. 15 and 16 are cross-sectional views for explaining other examples of the display device, FIGS. 17A to 17D and 18A to 18D are diagrams for explaining the optical system in other examples of the display device, and FIG. 19 is a graph for explaining the optical system in other examples of the display device. Hereinafter, the display device 1 will be described as an example, but the same applies to the display devices 1A and 1A'.

[0131] 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 is configured not to be emitted from the display device 1 (see FIGS. 2 and 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 front-side polarizing plate of the display panel 2 (liquid crystal panel) and the transmission axis of the reflective polarizing plate 8 are orthogonal (in a cross Nicol arrangement). As a result, as shown in FIGS. 2 and 3, the light of the second linearly polarized light L2 is not emitted from the display device 1, and the light of the fourth linearly polarized light L4 is emitted from the display device 1. In other words, the user 22 does not directly view the display panel 2, but views the reflected image reflected by the semi-transmissive mirror 6 as a virtual image V.

[0132] When the user 22 is not located in front of the display device 1, the cross Nicol arrangement of the transmission axis of the front-side polarizing plate of the display panel 2 and the transmission axis of the reflective polarizing plate 8 is disrupted, and a part of the light of the second linearly polarized light L2 may pass through the reflective polarizing plate 8. As a result, the user 22 may be able to view both the real image of directly viewing the display panel 2 and the virtual image V reflected by the semi-transmissive mirror 6, and the display quality of the display device 1 may deteriorate.

[0133] As shown in FIGS. 15 and 16, the display device 1 in this example has a third retardation plate 25 positioned between the display panel 2 and the reflective polarizing plate 8. Thereby, even when the user 22 is not positioned in front of the display device 1, the relative angle between the transmission axis of the front polarizing plate of the display panel 2 and the transmission axis of the reflective polarizing plate 8 can be made closer to the cross-Nicol arrangement, and a decrease in the display quality of the display device 1 can be reduced. The third retardation plate 25 may be a 1 / 2 wavelength plate (half-wave plate), a 1 / 4 wavelength plate, a 1 / 8 wavelength plate, a 1 / 16 wavelength plate, etc., or may be a wavelength plate that imparts other retardations. The optical axis of the third retardation plate 25 may be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizing plate 8.

[0134] The display device 1 in this example may further have a fourth retardation plate 26 positioned between the display panel 2 and the reflective polarizing plate 8. In this case, even when the user 22 is not positioned in front of the display device 1, the relative angle between the transmission axis of the front polarizing plate of the display panel 2 and the transmission axis of the reflective polarizing plate 8 can be made closer to the cross-Nicol arrangement by the cross-Nicol arrangement, and a decrease in the display quality of the display device 1 can be further reduced. The fourth retardation plate 26 may be a 1 / 2 wavelength plate (half-wave plate), a 1 / 4 wavelength plate, a 1 / 8 wavelength plate, a 1 / 16 wavelength plate, etc., or may be a wavelength plate that imparts other retardations. The optical axis of the fourth retardation plate 26 may be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizing plate 8.

[0135] The third retardation plate 25 and the fourth retardation plate 26 only need to be positioned between the display panel 2 and the reflective polarizing plate 8, and their positions are arbitrary. When no other optical element is positioned between the third retardation plate 25 and the fourth retardation plate 26, the third retardation plate 25 and the fourth retardation plate 26 may be in contact with each other. In this case, the thickness in the depth direction of the optical system 3 can be reduced.

[0136] The third retardation plate 25 and the fourth retardation plate 26 may be such that one is a quarter-wave plate and the other is a half-wave plate. In this case, the degradation of the display quality of the display device 1 can be effectively reduced. The third retardation plate 25 and the fourth retardation plate 26 may both be half-wave plates. In this case, the degradation of the display quality of the display device 1 can be more effectively reduced.

[0137] FIGS. 17A, 17B, 17C, and 17D are Poincaré spheres showing the optical functions (effects on the polarization state of light) of the third retardation plate 25 and the fourth retardation plate 26 when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates. FIGS. 17A and 17B are diagrams for explaining the optical function of the third retardation plate 25, and FIGS. 17C and 17D are diagrams for explaining the optical function of the fourth retardation plate 26. FIGS. 17A and 17C show views of the Poincaré sphere seen from the north pole (S3 axis direction), and FIGS. 17B and 17D show views of the Poincaré sphere seen from the side (S1 axis direction). In FIGS. 17A, 17B, 17C, and 17D, S LCD represents the polarization state of the light immediately after it exits the display panel 2. S 25 represents the polarization state of the light that has passed through the third retardation plate 25, and S 26 represents the polarization state of the light that has passed through the fourth retardation plate 26. S 26 can be said to represent the polarization state of the light immediately before it enters the reflective polarizing plate 8. S RP represents the polarization state of the light that passes through the reflective polarizing plate 8 with a substantially 100% transmittance, and S AP is S RP is the antipodal point (the point symmetric with respect to the center of the Poincaré sphere). S 26 is located at S AP or is located in the vicinity of S AP the possibility that the light emitted from the display panel 2 and passing through the third retardation plate 25 and the fourth retardation plate 26 passes through the reflective polarizing plate 8 can be reduced. As a result, the possibility that the user 22 visually recognizes the real image directly viewed from the display panel 2 can be reduced, and the degradation of the display quality of the display device 1 can be reduced.

[0138] As shown in FIGS. 17C and 17D, when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates, S 26 is substantially located at S AP . Therefore, the possibility that the user 22 visually recognizes the real image directly viewing the display panel 2 can be reduced, and the degradation of the display quality of the display device 1 can be reduced.

[0139] FIGS. 18A, 18B, 18C, and 18D are Poincare spheres showing the optical functions of the third retardation plate 25 and the fourth retardation plate 26 when the third retardation plate 25 is a quarter-wave plate and the fourth retardation plate 26 is a half-wave plate. FIGS. 18A and 18B are diagrams for explaining the optical function of the third retardation plate 25, and FIGS. 18C and 18D are diagrams for explaining the optical function of the fourth retardation plate 26. FIGS. 18A and 18C show views of the Poincare sphere seen from the north pole (S3 axis direction), and FIGS. 18B and 18D show views of the Poincare sphere seen from the side (S1 axis direction). S LCD , S 25 , S 26 , S RP and S AP are as described above.

[0140] As shown in FIGS. 18C and 18D, when the third retardation plate 25 is a quarter-wave plate and the fourth retardation plate 26 is a half-wave plate, S 26 is located near S AP . Therefore, the possibility that the user 22 visually recognizes the real image directly viewing the display panel 2 can be reduced, and the degradation of the display quality of the display device 1 can be reduced.

[0141] Figure 19 is a graph showing the relationship between the light transmittance of an optical system formed by inserting a third retardation plate 25 and a fourth retardation plate 26 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 mimics the front polarizing plate of the display panel 2, and the polarizing plate PP2 mimics the reflective polarizing plate 8.

[0142] The solid line in the graph of Figure 19 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. The transmittance is minimized when the retardation of the third retardation plate 25 is about 275 nm (half of the wavelength λ of the incident light). The dashed line in the graph of Figure 19 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. The transmittance is minimized when the retardation of the fourth retardation plate 26 is about 275 nm (half of the wavelength of the incident light).

[0143] From the simulation results shown in the graph of Figure 19, it can be seen that when the third retardation plate 25 and the fourth retardation plate 26 are half-wave plates, the display device 1 can effectively reduce the risk of the user 22 visually recognizing the real image when directly viewing the display panel 2, and can effectively reduce the degradation of the display quality of the display device 1. Also, even when the retardation of the fourth retardation plate 26 is fixed at 0 nm (i.e., when only the third retardation plate 25 is present), if the third retardation plate 25 can impart a retardation greater than 0 nm (i.e., non-zero) to the light incident on the third retardation plate 25, it can be seen that the display device 1 can effectively reduce the risk of the user 22 visually recognizing the real image when directly viewing the display panel 2, and can effectively reduce the degradation of the display quality of the display device 1.

[0144] The same applies to the display devices 1A and 1A'. The display devices 1A and 1A' may have a third retardation plate 25 positioned between the display panel 2 and the polarizing plate 15. In this case, the possibility that the user 22 visually recognizes the real image directly viewed on 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 positioned between the display panel 2 and the polarizing plate 15. In this case, the possibility that the user 22 visually recognizes the real image directly viewed on 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 wavelength plate (half-wave plate), a 1 / 4 wavelength plate, a 1 / 8 wavelength plate, a 1 / 16 wavelength plate, etc., or may be a wavelength plate that imparts other retardations. One of the third retardation plate 25 and the fourth retardation plate 26 may be a 1 / 4 wavelength 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 positioned between the display panel 2 and the polarizing plate 15, and their positions are arbitrary.

[0145] Next, other examples of the display devices 1, 1A, 1A', and 1B will be described. FIG. 20 is a cross-sectional view showing another example of the display device 1A', and FIG. 21 is a cross-sectional view showing another example of the display device 1A.

[0146] The second semi-transmissive mirror 13' of the display device 1A' may be configured to include a holographic optical element (HOE). In this case, as shown in FIG. 20, the optical function of the second semi-transmissive mirror 13' can be realized by a flat optical element, and the thickness of the second semi-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. Further, since the second semi-transmissive mirror 13' is a flat optical element, the distance between the second semi-transmissive mirror 13' and the second retardation plate 14 can be reduced, or the second semi-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.

[0147] The first semi-transmissive mirror 11 of the display device 1A' may be configured to include an HOE. In this case, as shown in FIG. 20, the optical function of the first semi-transmissive mirror 11 can be realized by a flat optical element, and the thickness of the first semi-transmissive mirror 11 in the depth direction can be reduced. As a result, the display device 1A' can be miniaturized in the depth direction. Further, since the first semi-transmissive mirror 11 is a flat optical element, 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, so that the display device 1A' can be further miniaturized in the depth direction.

[0148] When the first semi-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 viewed by the user 22 decreases. Therefore, the first semi-transmissive mirror 11 including an HOE may be configured to have polarization selectivity. For example, the first semi-transmissive mirror 11 including an HOE may have a plurality of metal fine wires (metal nanowire grids) formed on the surface facing the display panel 2 or the surface facing the first retardation plate 12 to realize polarization selectivity of transmitting S-wave polarized light and reflecting P-wave polarized light. In this case, a decrease in the brightness of the virtual image V viewed by the user 22 can be reduced.

[0149] The first half-transmissive mirror 11 of the display device 1A may be configured to include a HOE. In this case, as shown in FIG. 21, the optical function of the first half-transmissive mirror 11 can be realized by 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. Further, 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 and the display panel 2 can be brought into contact with each other, so that the display device 1A can be further miniaturized in the depth direction. The first half-transmissive mirror 11 including a HOE may have polarization selectivity. For example, the first half-transmissive mirror 11 including a HOE may be formed with a plurality of metal fine lines that realize 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, it is possible to reduce the luminance reduction of the virtual image V viewed by the user 22.

[0150] The half-transmissive mirror 6 of the display device 1 may be configured to include a HOE. In this case, the optical function of the half-transmissive mirror 6 can be realized by 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.

[0151] The first semi-transmissive mirror 17 of the display device 1B may be configured to include a HOE. In this case, the optical function of the first semi-transmissive mirror 17 can be realized by a flat optical element, and the thickness of the first semi-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 semi-transmissive mirror 17 is a flat optical element, 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 a HOE may have polarization selectivity. For example, the first semi-transmissive mirror 17 including a HOE may be formed with a plurality of metal fine lines that realize 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 18. In this case, it is possible to reduce the luminance reduction of the virtual image V viewed by the user 22.

[0152] The third semi-transmissive mirror 21 of the display device 1B may be configured to include a HOE. In this case, the optical function of the third semi-transmissive mirror 21 can be realized by a flat optical element, and the thickness of the third semi-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 semi-transmissive mirror 21 including a HOE may have polarization selectivity. For example, the third semi-transmissive mirror 21 including a HOE may be formed with a plurality of metal fine lines that realize polarization selectivity for reflecting S-wave polarized light and transmitting P-wave polarized light on the surface facing the second retardation plate 20 or the surface opposite to the surface facing the second retardation plate 20. In this case, it is possible to reduce the deterioration of the quality of the virtual image V viewed by the user 22, and it is also possible to reduce the luminance reduction of the virtual image V.

[0153] The holographic optical element may, for example, have an interference fringe pattern and be configured to diffract incident light in a predetermined direction.

[0154] The display device 1A' may be configured such that the second semi-transmissive mirror 13' includes a Fresnel lens. In this case, as shown in FIG. 22, the optical function of the second semi-transmissive mirror 13' can be realized by a substantially flat optical element having a thickness (dimension in the depth direction) reduced compared to a convex half mirror, and the thickness of the second semi-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 semi-transmissive mirror 13' is substantially flat, the distance between the second semi-transmissive mirror 13' and the second retardation plate 14 can be reduced, or the second semi-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. The second semi-transmissive mirror 13' including a Fresnel lens is also referred to as a Fresnel half mirror.

[0155] As shown in FIG. 23, the Fresnel half mirror 13' may include a Fresnel lens (Fresnel convex lens) 33 having a planar first surface 33a facing the second retardation plate 14 and a Fresnel-shaped second surface 33b facing the first retardation plate 12, and a semi-transmissive reflection layer 34 located on the second surface 33b. The Fresnel shape has concentric grooves centered on a reference point 33c. The grooves include a plane substantially perpendicular to the first surface 33a and an inclined surface inclined with respect to the first surface 33a. The inclined surface may be a curved surface or a flat surface. The semi-transmissive reflection layer 34 may be located on the inclined surface of the Fresnel shape. The semi-transmissive reflection layer 34 may transmit a part (e.g., approximately 50%) of the incident light and reflect the remaining part (e.g., approximately 50%). The semi-transmissive reflection layer 34 may be a metal thin film. The metal thin film may be made of a metal material such as aluminum or chromium. The metal thin film may be formed by a deposition method such as CVD (Chemical Vapor Deposition) method or PVD (Physical Vapor Deposition) method.

[0156] The Fresnel half mirror 13’ has an optical function as a lens and an optical function as a half mirror. The optical function as a lens (such as 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 mirror (such as focal length, transmittance, etc.) is determined by the curvature and inclination angle of the inclined surface, the transmittance of the semi-transmissive reflection layer 34, etc.

[0157] The surface of the Fresnel half mirror 13’ facing the second retardation plate 14 may be flattened by a transparent material layer formed on the second surface 33b of the Fresnel lens 33. The transparent material layer may be composed of a material having substantially the same refractive index as the material constituting the Fresnel lens 33. The transparent material layer may be composed of the same material as the material constituting the Fresnel lens 33.

[0158] The display device 1A’ may be configured such that the first semi-transmissive mirror 11 includes a Fresnel lens. In this case, as shown in FIG. 22, the thickness of the first semi-transmissive mirror 11 can be reduced, and as a result, the display device 1A’ can be miniaturized in the depth direction. Further, 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, so that 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 configuration as the Fresnel half mirror 13’. The Fresnel half mirror 11 may be configured to include a Fresnel concave lens.

[0159] When the first semi-transmissive mirror 11 is replaced with a Fresnel half mirror 11 having no polarization selectivity, the amount of light emitted from the display device 1A' decreases, and the luminance of the virtual image V viewed 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 have a plurality of metal fine wires (metal nanowire grids) formed on the surface facing the display panel 2 or the surface facing the first retardation plate 12, which realizes the polarization selectivity of transmitting the light of S-wave polarization and reflecting the light of P-wave polarization. Thereby, the decrease in the luminance of the virtual image V viewed by the user 22 can be reduced.

[0160] As shown in FIG. 23, the first semi-transmissive mirror 11 of the display device 1A may include a Fresnel lens. In this case, the thickness of the first semi-transmissive mirror 11 can be reduced, and as a result, the display device 1A can be miniaturized in the depth direction. Further, 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, so that 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 have a plurality of metal fine wires formed on the surface facing the display panel 2 or the surface facing the first retardation plate 12, which realizes the polarization selectivity of transmitting the light of S-wave polarization and reflecting the light of P-wave polarization. In this case, the decrease in the luminance of the virtual image V viewed by the user 22 can be reduced.

[0161] The semi-transmissive mirror 6 of the display device 1 may include a Fresnel lens. In this case, the thickness of the semi-transmissive mirror 6 can be reduced, and as a result, the display device 1 can be miniaturized in the depth direction. Further, since the semi-transmissive mirror 6 including the Fresnel lens is substantially flat, the distance between the semi-transmissive mirror 6 and the first retardation plate 5 can be reduced, or the semi-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.

[0162] The first half-transmissive mirror 17 of the display device 1B may be configured to include a Fresnel lens. In this case, the thickness of the first half-transmissive mirror 17 can be reduced, and as a result, the display device 1B can be miniaturized in the depth direction. Further, since the first half-transmissive mirror 17 including the Fresnel lens is substantially flat, 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 the Fresnel lens may be configured to have polarization selectivity. For example, the first half-transmissive mirror 17 including the Fresnel lens may be formed with a plurality of metal fine lines that realize polarization selectivity of 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 18. In this case, a reduction in the brightness of the virtual image V viewed by the user 22 can be reduced.

[0163] The third half-transmissive mirror 21 of the display device 1B may be configured to include a Fresnel lens. In this case, the thickness of the third half-transmissive mirror 21 can be reduced, and as a result, the display device 1B can be miniaturized in the depth direction. The third half-transmissive mirror 21 including the Fresnel lens may be configured to have polarization selectivity. For example, the third half-transmissive mirror 21 including the Fresnel lens may be formed with a plurality of metal fine lines that realize polarization selectivity of reflecting S-wave polarized light and transmitting P-wave polarized light on the surface facing the second retardation plate 20 or the surface opposite to the surface facing the second retardation plate 20. In this case, a reduction in the quality of the virtual image V viewed by the user 22 can be reduced, and a reduction in the brightness of the virtual image V can also be reduced.

[0164] Hereinafter, the control of the peeping area in the imaging device 100 (display devices 1, 1A, 1A', 1B) will be described. In the following description, it is assumed that the imaging device 100 is a digital rearview mirror (see FIG. 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 predetermined direction fixed to the moving body 23. The predetermined direction may be, for example, the vehicle length direction of the moving body 23, but is not limited thereto. The angle sensor may be a three-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 it is assumed that the imaging device 100 can communicate with the DMS and control the DMS. The DMS can image the face of the user 22 sitting in the driver's seat of the moving body 23, perform face authentication of the user 22, and determine whether the user 22 is a known user. A known user may mean a user in whom information such as features used 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.

[0165] When the user 22 is located in front of the display devices 1, 1A, 1A', 1B, since the sizes of the left peeping area PL and the right peeping area PR are substantially the same (see FIG. 25), the user 22 can visually recognize the virtual image V that changes according to the movement of the head, similar to when using a normal rearview mirror. When the user 22 is not located in front of the display devices 1, 1A, 1A', 1B, the sizes of the left peeping area PL and the right peeping area PR do not match (see FIG. 26), and the user 22 cannot visually recognize the virtual image V that changes according to the movement of the head, similar to when using a normal rearview mirror, and may feel discomfort.

[0166] Referring to the flowchart shown in FIG. 29, the control of the imaging device 100 by the controller 43 will be described. In the flowchart, "step" is abbreviated as "S", and in the chart, "positive" (computer flag = 1) in the determination control is represented by [Yes], and "negative" (computer flag = 0 zero) is represented by [No].

[0167] The flowchart of FIG. 29 starts, for example, when the user 22 sits in the driver's seat of the moving body 23 and starts the engine of the moving body 23.

[0168] In [S1], the DMS is controlled to confirm the user 22 sitting in the driver's seat of the moving body 23 (user confirmation).

[0169] In [S2], the DMS is controlled to perform a face authentication of the user 22 sitting in the driver's seat and determine whether the user 22 is a known user. In [S2], if the user 22 is a known user [Yes], the process proceeds to [S3]. In [S2], if the user 22 is not a known user [No], the process proceeds to [S7].

[0170] In [S3], user information of the user 22 (information such as the position of the eyes and the direction of the face during driving) is acquired from the DMS.

[0171] In [S4], based on the user information acquired 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 on 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. As shown in FIG. 27, the change of the display area may be to make a part of the display surface 2a a non-display area 2b where no image is displayed. As shown in FIG. 27, by changing the display area of the display image on the display surface 2a, even when the user 22 is not positioned in front of the display devices 1, 1A, 1A', 1B, the size of the left peeking-in area PL and the size of the right peeking-in area PR can be made substantially the same, and as a result, the possibility that the user 22 feels discomfort can be reduced.

[0172] The adjustment of the display devices 1, 1A, 1A', 1B may include sliding (translating) 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 shown in FIG. 28, the size of the left peeking-in area PL and the size of the right peeking-in area PR can be made substantially the same, and as a result, the possibility that the user 22 feels discomfort can be reduced. Also, 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 reduction in the sizes of the left peeking-in area PL and the right peeking-in area PR compared to the case where the user 22 is positioned in front of the display devices 1, 1A, 1A', 1B.

[0173] In [S5], the controller 43 receives an instruction from the user 22 as to whether readjustment of the display devices 1, 1A, 1A', 1B is necessary. The imaging device 100 may be configured such that the user 22 can instruct that readjustment is necessary 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 instruct that readjustment is necessary by swinging the imaging device 100 and varying the orientation of the imaging device 100. The variation in the orientation of the imaging device 100 may be detected by a three-axis angle sensor of the imaging device 100. Note that if no instruction is received from the user 22 within a predetermined time after the controller 43 starts receiving the instruction from the user 22, the controller 43 may determine that readjustment is not necessary. The predetermined time may be, for example, about 3 to 10 seconds, but is not limited thereto.

[0174] In [S5], if readjustment of the display devices 1, 1A, 1A', 1B is necessary [Yes], the process proceeds to [S6]. In [S5], if readjustment of the display devices 1, 1A, 1A', 1B is not necessary [No], this flowchart ends. Note that in [S5], if readjustment of the display devices 1, 1A, 1A', 1B is necessary [Yes], the process may proceed to [S7].

[0175] In [S6], the controller 43 controls the DMS to detect the user information (information such as the position of the eyes and the orientation of the face during driving) of the user 22, and acquires the user information of the user 22 from the DMS.

[0176] In [S7], based on the user information acquired in [S6], the display devices 1, 1A, 1A', 1B are adjusted. 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].

[0177] In [S8], an instruction from the user 22 regarding whether readjustment of the display devices 1, 1A, 1A', 1B is necessary is received. The reception of the instruction from the user 22 may be the same as in [S5]. In [S8], if readjustment of the display devices 1, 1A, 1A', 1B is necessary [Yes], the process returns to [S6]. In [S8], if readjustment of the display devices 1, 1A, 1A', 1B is not necessary [No], the process proceeds to [S9]. Note that in [S8], if readjustment of the display devices 1, 1A, 1A', 1B is necessary [Yes], the process may also return to [S7].

[0178] In [S9], the controller 43 stores the user information of the user 22 and information regarding 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 ends this flowchart.

[0179] According to the flowchart of FIG. 29, the peeping area in the digital rearview mirror can be efficiently controlled, and the possibility that the user 22 feels discomfort can be reduced. Note that the flowchart of FIG. 29 can also be applied when the imaging device 100 constitutes a digital side mirror.

[0180] Another example of the display devices 1, 1A, 1A', 1B will be described. For configurations similar to those of the display devices 1, 1A, 1A', 1B, the same reference numerals are given, and detailed descriptions are omitted. As shown in FIG. 33, the display device 1C in this example includes a display panel 2, an optical system 35, and a housing 36.

[0181] 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 into the visual field of the user 22. The optical system 35 may be the optical system 3 (see FIGS. 2, 3, 30), the optical system 10 (see FIGS. 4, 5, 31), or the optical system 16 (see FIGS. 9, 32). FIGS. 33 to 36 show the case where the optical system 35 is the optical system 3 shown in FIG. 30.

[0182] 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 that transmits the light emitted from the optical system 35. The display device 1C may be arranged such that the window 37 and the display panel 2 overlap when the window 37 of the housing 36 is viewed. Also, the display device 1C may be arranged such that the window 37 and the optical system 35 overlap when the window 37 of the housing 36 is viewed. Also, the display device 1C may be arranged such that the display panel 2 and the optical system 35 overlap when the window 37 of the housing 36 is viewed. 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. Also, in the display device 1C, the display light emitted from the display panel 2 propagates substantially on a single axis and forms an image as the virtual image V. For this reason, it is possible to reduce the distortion, uneven brightness, etc. of the virtual image V viewed by the user 22, and the design of the optical system 35 becomes easy.

[0183] As shown in FIGS. 33 and 34, the housing 36 may have a light transmissive plate 38 disposed in the window 37. The light transmissive plate 38 may transmit the light emitted from the optical system 35. The light transmissive plate 38 at least partially closes the window 37. The light transmissive plate 38 may be made of, for example, glass, resin, or the like.

[0184] The optical system 35 (optical system 3) may include a third retardation plate 25 and a fourth retardation plate 26. The third retardation plate 25 may be located on the surface facing the semi-transmissive mirror 6 of the second retardation plate 7. The fourth retardation plate 26 may be located on the surface facing the semi-transmissive mirror 6 of the third retardation plate 25. Thereby, even when the user 22 is not positioned 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 closer to the cross Nicol arrangement, and a decrease in the display quality of the display device 1C can be reduced. The third retardation plate 25 and the fourth retardation plate 26 may be a 1 / 2 wavelength plate (half wavelength plate), but are not limited thereto. The third retardation plate 25 and the fourth retardation plate 26 may be a 1 / 4 wavelength plate, a 1 / 8 wavelength plate, a 1 / 16 wavelength plate, etc., or may be a wavelength plate that imparts other retardations. The third retardation plate 25 and the fourth retardation plate 26 may be wavelength plates that impart the same retardation, or may be wavelength plates that impart different retardations. The optical axis of the third retardation plate 25 may be substantially parallel or substantially perpendicular to the transmission axis of the reflective polarizing plate 8.

[0185] The optical system 35 (optical system 3) may include a moth-eye structure film 39 located on the surface facing the semi-transmissive mirror 6 of the first retardation plate 5. The moth-eye structure film 39 can attenuate the reflected light of the light incident from the semi-transmissive mirror 6 side. Thereby, it is possible to reduce the incidence of unnecessary light, disturbance light, etc. on the user's 22 eyes after being reflected by the first retardation plate 5 and then emitted from the display device 1C.

[0186] The optical system 35 (optical system 3) may include a moth-eye structure film 40 located on the surface facing the semi-transmissive mirror 6 of the fourth retardation plate 26. Thereby, it is possible to reduce the incidence of unnecessary light, disturbance light, etc. on the user's 22 eyes after being reflected by the fourth retardation plate 26 and then emitted from the display device 1C.

[0187] The reflective polarizing plate 8, the second retardation plate 7, the third retardation plate 25, the fourth retardation plate 26, and the moth-eye structure film 40 may be integrated with the light transmission plate 38. Thereby, the display device 1C can be thinned in the depth direction (Z-axis direction). Further, deformation of the reflective polarizing plate 8, the second retardation plate 7, the third retardation plate 25, the fourth retardation plate 26, the moth-eye structure film 40, and the light transmission plate 38 can be reduced.

[0188] The display device 1C may have a touch panel 41. The touch panel 41 may at least partially block the window 37. As shown in FIGS. 35 and 36, the touch panel 41 may be attached to the housing 36. As shown in FIGS. 35 and 36, the touch panel 41 may be attached to the housing 36 so as to cover the window 37 in which the light transmission plate 38 is disposed. The touch panel 41 may cover the light transmission plate 38. The touch panel 41 is communicably connected to the controller 43 via a wired or wireless communication line. Thereby, the user 22 can operate the display device 1C via the touch panel 41. The touch panel 41 may be a known touch panel.

[0189] The display system 200 of the present disclosure will be described. As shown in FIG. 39, the display system 200 includes display devices 1, 1A, 1A', 1B, 1C and a camera 201. The display panel 2 of the display devices 1, 1A, 1A', 1B, 1C is communicable with the camera 201 and displays an image captured by the camera 201. The display panel 2 and the camera 201 may be connected via, for example, wired, wireless, CAN (Controller Area Network), or the like.

[0190] The mobile body (vehicle) 23 of the present disclosure includes a display system 200. The display devices 1, 1A, 1A', 1B, 1C are small-sized display devices, which can be arranged in the driver's cab of the vehicle 23 without occupying a large volume in the driver's cab and are unlikely to interfere with driving. Therefore, the user 22 can appropriately visually recognize the virtual image V or the real image. The display system 200 may be applied to the digital rearview mirror of the vehicle 23, or may be applied to the digital side mirrors 1L, 1R (see FIG. 12). The display system 200 may be applied to the cluster 29, CID (Center Information Display) 30, PID (Passenger Information Display) 31, RSE (Rear Seat Entertainment) system 32, etc. (see FIGS. 10 and 12) in the dashboard of the vehicle 23.

[0191] According to the present disclosure, it is possible to reduce a decrease in display quality in a small-sized display device and improve light utilization efficiency. Further, according to the present disclosure, it is possible to provide a small-sized imaging device that allows a user to favorably visually recognize a virtual image.

[0192] As described above, the embodiments of the present disclosure have been described in detail. However, the present disclosure is not limited to the above-described embodiments, and various changes, improvements, etc. are possible without departing from the gist of the present disclosure. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. For example, functions etc. included in each component etc. can be rearranged so as not to be logically contradictory, and a plurality of components etc. can be combined into one or divided. That is, it should be noted that those skilled in the art can easily make various modifications or corrections based on the present disclosure. Also, note that these changes, modifications, or corrections are included in the scope of the present disclosure.

[0193] The display device of the present disclosure can be implemented in the following aspects (1) to (48).

[0194] (1) A display panel that emits linearly polarized display light, a first retardation plate facing the display panel; a second retardation plate disposed apart from the first retardation plate; a reflective polarizing plate that transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light; a semi-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a reflective surface facing the second retardation plate; and a display device, wherein the first retardation plate and the second retardation plate are quarter-wave plates.

[0195] (1´) a display panel that emits display light; a first retardation plate facing the display panel; a second retardation plate disposed apart from the first retardation plate; a reflective polarizing plate disposed to face the second retardation plate and transmitting a first polarization and reflecting a second polarization; 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; and a display device, wherein the first retardation plate and the second retardation plate convert the display light into the first polarization and the second polarization.

[0196] (2) The display device according to (1) above, wherein air is interposed between the first retardation plate and the second retardation plate.

[0197] (3) The display device according to (1) or (2) above, further comprising a third retardation plate disposed between the display panel and the reflective polarizing plate.

[0198] (4) The display device according to (3) above, further comprising a fourth retardation plate disposed between the display panel and the reflective polarizing plate.

[0199] (5) The display device according to (4) above, wherein one of the third retardation plate and the fourth retardation plate is a quarter-wave plate and the other is a half-wave plate.

[0200] (6) The third retardation plate and the fourth retardation plate are half-wave plates, and the display device according to (4) above.

[0201] (7) The reflecting surface of the semi-transmissive mirror is concave, and the display device according to any one of (1) to (6) above.

[0202] (8) The semi-transmissive mirror is a flat optical element composed of a holographic optical element, and the display device according to any one of (1) to (6) above.

[0203] (9) The semi-transmissive mirror includes a Fresnel lens, and the display device according to any one of (1) to (6) above.

[0204] (10) The semi-transmissive mirror is integrated with the first retardation plate and / or the second retardation plate, and the display device according to (8) or (9) above.

[0205] (11) A display panel that emits linearly polarized display light, A first retardation plate facing the display panel, A second retardation plate disposed at a distance from the first retardation plate, A first semi-transmissive mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate, A second semi-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a second reflecting surface facing the first retardation plate, A polarizing plate facing the second retardation plate, and The first retardation plate and the second retardation plate are quarter-wave plates, and the display device.

[0206] (11´) A display panel that emits display light, A first retardation plate facing the display panel, A second retardation plate disposed at a distance from the first retardation plate, A first semi-transmissive mirror disposed between the display panel and the first retardation plate and having a first reflecting surface facing the first retardation plate, A second half-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a second reflecting surface facing the first retardation plate; A polarizing plate facing the second retardation plate, and The first retardation plate and the second retardation plate are configured to make the display light into a first polarization that passes through the polarizing plate and a second polarization that is less transmissive through the polarizing plate than the first polarization. A display device.

[0207] (12) The second reflecting surface is a convex surface protruding toward the first retardation plate side. The display device according to (11) above.

[0208] (13) Air is interposed between the first half-transmissive mirror and the first retardation plate. The display device according to (11) or (12) above.

[0209] (14) A third retardation plate disposed between the display panel and the polarizing plate. The display device according to any one of (11) to (13) above.

[0210] (15) A fourth retardation plate disposed between the display panel and the polarizing plate. The display device according to (14) above.

[0211] (16) One of the third retardation plate and the fourth retardation plate is a quarter-wave plate, and the other is a half-wave plate. The display device according to (15) above.

[0212] (17) The third retardation plate and the fourth retardation plate are half-wave plates. The display device according to (15) above.

[0213] (18) The first reflecting surface is concave. The display device according to any one of (11) to (17) above.

[0214] (19) The first half-transmissive mirror and the second half-transmissive mirror are flat optical elements composed of holographic optical elements. The display device according to any one of (11) to (17) above.

[0215] (20) The first semi-transmissive mirror and the second semi-transmissive mirror include a Fresnel lens, and the display device according to any one of (11) to (17) above.

[0216] (21) The first semi-transmissive mirror is integrated with the display panel and / or the first retardation plate, and the display device according to (19) or (20) above.

[0217] (22) The second semi-transmissive mirror is integrated with the first retardation plate and / or the second retardation plate, and the display device according to (19) or (20) above.

[0218] (23) A display panel that emits linearly polarized display light, A first retardation plate facing the display panel, A second retardation plate disposed at a distance from the first retardation plate, 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, 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 a third reflective surface facing the second retardation plate, A third semi-transmissive mirror having a fourth reflective surface facing the second retardation plate, and the display device includes, The first retardation plate and the second retardation plate are quarter-wave plates, and the display device.

[0219] (23´) A display panel that emits display light, A first retardation plate that transmits the display light, A second retardation plate disposed at a distance from the first retardation plate, 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, 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 a third reflective surface facing the second retardation plate, A display device including a third semi-transmissive mirror having a fourth reflecting surface facing the second retardation plate.

[0220] (24) The display device according to (23) above, 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.

[0221] (25) The display device according to (23) or (24) above, wherein the first reflecting surface and the fourth reflecting surface are concave.

[0222] (26) The display device according to (23) or (24) above, wherein the first semi-transmissive mirror and the third semi-transmissive mirror are flat optical elements composed of holographic optical elements.

[0223] (27) The display device according to (23) or (24) above, wherein the first semi-transmissive mirror and the third semi-transmissive mirror include Fresnel lenses.

[0224] (28) The display device according to (26) or (27) above, wherein the first semi-transmissive mirror is integrated with the display panel and / or the first retardation plate.

[0225] (29) The display device according to any one of (26) to (28) above, wherein the second semi-transmissive mirror is integrated with the second retardation plate.

[0226] (30) The display light includes display light for a left-eye image and display light for a right-eye image, The display device according to any one of (1) to (29) above, further including an optical element that defines the respective light-ray directions of the display light for the left-eye image and the display light for the right-eye image.

[0227] (31) An imaging device including the display device according to any one of (1) to (30) above.

[0228] (32) The imaging device according to (31) above, wherein a virtual image projected within the user's field of view includes a binocular visible region visible to both the user's left and right eyes, a left-eye visible region visible only to the left eye, and a right-eye visible region visible only to the right eye.

[0229] (33) 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 has 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 the window of the housing is viewed.

[0230] (34) The display device according to (33) above, wherein the housing has a light transmission plate disposed on the window.

[0231] (35) The display device according to (34) above, further comprising a touch panel attached to the housing so as to cover the light transmission plate.

[0232] (36) The display device according to any one of (1) to (30) and (33) to (35) above, further comprising an irradiator that irradiates light onto a surface of the display panel opposite to the display surface.

[0233] (37) The display device according to any one of (1) to (30) and (33) to (36) above, further comprising a controller having a function of controlling at least one of an image displayed on the display panel and the irradiator.

[0234] (38) A vehicle comprising the display device according to (37) above.

[0235] (39) A display panel that emits linearly polarized display light, a first retardation plate facing the display panel, a second retardation plate disposed at a distance from the first retardation plate, A reflective polarizing plate that transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light; A half-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a reflective surface facing the second retardation plate; The first retardation plate and the second retardation plate are quarter-wave plates; A display device, wherein an optical path length of light that is emitted from the display panel, transmitted through the half-transmissive mirror, reflected by the reflective polarizing plate, and reaches the half-transmissive mirror is smaller than a focal length of the half-transmissive mirror.

[0236] (40) A display panel that emits linearly polarized display light; A first retardation plate facing the display panel; A second retardation plate disposed at a distance from the first retardation plate; A reflective polarizing plate that transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light; A half-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a reflective surface facing the second retardation plate; The first retardation plate and the second retardation plate are quarter-wave plates; A display device, wherein an optical path length of light that is emitted from the display panel, transmitted through the half-transmissive mirror, reflected by the reflective polarizing plate, and reaches the half-transmissive mirror is larger than a focal length of the half-transmissive mirror.

[0237] (41) A display panel that emits linearly polarized display light; A first retardation plate that transmits the display light; A second retardation plate disposed at a distance from the first retardation plate; A first half-transmissive mirror disposed between the display panel and the first retardation plate and having a first reflective surface facing the first retardation plate; A second half-transmissive mirror disposed between the first retardation plate and the second retardation plate and having a second reflective surface facing the first retardation plate; A polarizing plate facing the second retardation plate; The first retardation plate and the second retardation plate are quarter-wave plates, A display device, wherein an optical path length of light that is emitted from the display panel, passes through the first semi-transmissive mirror, is reflected by the second semi-transmissive mirror, and reaches the first semi-transmissive mirror is smaller than a focal length of the first semi-transmissive mirror.

[0238] (42) A display panel that emits linearly polarized display light, A first retardation plate that transmits the display light, A second retardation plate that is disposed at a distance 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 reflective 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 reflective surface facing the first retardation plate, A polarizing plate facing the second retardation plate, The first retardation plate and the second retardation plate are quarter-wave plates, A display device, wherein an optical path length of light that is emitted from the display panel, passes through the first semi-transmissive mirror, is reflected by the second semi-transmissive mirror, and reaches the first semi-transmissive mirror is larger than a focal length of the first semi-transmissive mirror.

[0239] (43) A display panel that emits linearly polarized display light, A first retardation plate that transmits the display light, A second retardation plate that is disposed at a distance 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 reflective 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 reflective surface facing the first retardation plate and a third reflective surface facing the second retardation plate, A third semi-transmissive mirror that has a fourth reflective surface facing the second retardation plate, The first retardation plate and the second retardation plate are quarter-wave plates, Light that is emitted from the display panel, passes through the first semi-transmissive mirror, is reflected by the second semi-transmissive mirror, and reaches the first semi-transmissive mirror has an optical path length that is less than the focal length of the first semi-transmissive mirror, and light that is emitted from the display panel, passes through the first semi-transmissive mirror, passes through the second semi-transmissive mirror, and reaches the third semi-transmissive mirror has an optical path length that is less than the focal length of the first semi-transmissive mirror. A display device.

[0240] (44) A display panel that emits linearly polarized display light, A first retardation plate that transmits the display light, A second retardation plate that is disposed at a distance 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 reflective 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 reflective surface facing the first retardation plate and a third reflective surface facing the second retardation plate, A third semi-transmissive mirror that has a fourth reflective surface facing the second retardation plate, The first retardation plate and the second retardation plate are quarter-wave plates, Light that is emitted from the display panel, passes through the first semi-transmissive mirror, is reflected by the second semi-transmissive mirror, and reaches the first semi-transmissive mirror has an optical path length that is greater than the focal length of the first semi-transmissive mirror, and light that is emitted from the display panel, passes through the first semi-transmissive mirror, passes through the second semi-transmissive mirror, and reaches the third semi-transmissive mirror has an optical path length that is greater than the focal length of the first semi-transmissive mirror. A display device.

[0241] (45) A display panel that emits display light, A convex lens that transmits the display light, A display device in which the optical path length from the display panel to the convex lens is less than the focal length of the convex lens.

[0242] (46) A display panel that emits display light, A convex lens that transmits the display light, A display device in which the optical path length from the display panel to the convex lens is greater than the focal length of the convex lens.

[0243] (47) A display device according to any one of (1) to (30), (33) to (37), and (39) to (46), and a camera, A display system in which the display panel is capable of communicating with the camera and displays an image captured by the camera.

[0244] (48) A vehicle including the display system according to (47).

Explanation of reference numerals

[0245] 1, 1A, 1A’, 1B Display device 2 Display panel 2a Display surface 3 Optical system 4 Illuminator 5 First retardation plate 6 Half mirror 6a Reflective surface 7 Second retardation plate 8 Reflective polarizing plate 9 Optical element 10 Optical system 11 First half mirror 11a Reflective surface 12 First retardation plate 13, 13’ Second half mirror 13a, 13’a Reflective surface 14 Second retardation plate 15 Polarizing plate 16 Optical system 17 First half mirror 17a Reflective surface 18 First retardation plate 19 Second half mirror 19a Reflective surface 19b Reflective surface 20 Second retardation plate 21 Third half mirror 21a Reflective surface 22 User 22L Left eye 22R Right eye 23 Moving body 24 Windshield 25 Third phase difference plate 26 Fourth phase difference plate 27 Housing 28 Opening 29 Cluster 30 CID 31 PID 32 RSE 33 Fresnel lens 33a First surface 33b Second surface 33c Reference point 34 Semi-transmissive reflective layer 35 Optical system 36 Housing 37 Window 38 Light transmission plate 39,40 Mosquito-eye structure film 41 Touch panel 42 Convex lens 43 Controller 100 Imaging device 101 Reflective optical element 102 Camera 200 Display system 201 Camera

Claims

[Claim 1] A display panel that emits display light; a first retardation plate facing the display panel; a second retardation plate disposed apart from the first retardation plate; a reflective polarizing plate disposed opposite the second retardation plate and transmitting the first polarized light and reflecting the second polarized light; a semi-transmitting mirror disposed between the first retardation plate and the second retardation plate and having a reflecting surface facing the second retardation plate, The first retardation plate and the second retardation plate convert the display light into a first polarization and a second polarization.

Images