Display device, image recognition device, display system and vehicle

Abstract

The display device comprises a display panel, a first phase difference plate, a semi-transparent mirror, a second phase difference plate, and a reflective polarizer. The display panel emits display light. The first phase difference plate is positioned opposite the display panel. The second phase difference plate is positioned spaced apart from the first phase difference plate. The reflective polarizer is positioned opposite the second phase difference plate and transmits the first polarization to reflect the second polarization. The semi-transparent mirror is positioned between the first phase difference plate and the second phase difference plate and has a reflective surface facing the second phase difference plate. The first phase difference plate and the second phase difference plate make the display light into the first polarization and the second polarization.

Description

Technology Field

[0001] The present disclosure relates to a display device, an image recognition device, a display system, and a vehicle. Background Technology

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

[0003] Japanese Patent Publication No. 2022-63533

[0004] The display device of the present disclosure comprises a display panel that emits display light, and

[0005] A first phase difference plate facing the above-mentioned display panel, and

[0006] A second phase difference plate spaced apart from the first phase difference plate, and

[0007] A reflective polarizer disposed opposite to the second phase difference plate and transmitting the first polarization and reflecting the second polarization, and

[0008] A semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a reflective surface facing the second phase difference plate, and

[0009] The first phase difference plate and the second phase difference plate make the display light into a first polarization and a second polarization.

[0010] In addition, the display device of the present disclosure comprises a display panel that emits display light, and

[0011] A first phase difference plate that transmits the above-mentioned indicator light, and

[0012] A second phase difference plate spaced apart from the first phase difference plate, and

[0013] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0014] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate, and

[0015] A polarizing plate facing the second phase difference plate is provided,

[0016] The first phase difference plate and the second phase difference plate make the display light into a first polarization that passes through the polarizing plate and a second polarization that passes through the polarizing plate less than the first polarization.

[0017] In addition, the display device of the present disclosure comprises a display panel that emits display light, and

[0018] A first phase difference plate that transmits the above-mentioned indicator light, and

[0019] A second phase difference plate spaced apart from the first phase difference plate, and

[0020] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0021] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate, and

[0022] It is equipped with a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate.

[0023] The imaging device of the present disclosure includes the above-mentioned display device.

[0024] In addition, the display device of the present disclosure comprises a display panel, and

[0025] An optical system that projects display light emitted from the above-mentioned display panel as a virtual or real image, and

[0026] A housing that accommodates the above-mentioned display panel and the above-mentioned optical system is provided,

[0027] The above housing has a window that transmits light emitted from the optical system, and

[0028] When looking at the window of the above housing, the window, the optical system, and the display panel are arranged to overlap.

[0029] The vehicle of the present disclosure is equipped with the above-mentioned display device.

[0030] In addition, the display device of the present disclosure comprises a display panel that emits display light, and

[0031] The above-mentioned convex lens through which the indicator light is transmitted is provided,

[0032] The optical path length from the above display panel to the above convex lens is smaller than the focal length of the above convex lens.

[0033] In addition, the display device of the present disclosure comprises a display panel that emits display light, and

[0034] The above-mentioned convex lens through which the indicator light is transmitted is provided,

[0035] The optical path length from the above display panel to the above convex lens is greater than the focal length of the above convex lens.

[0036] The display system of the present disclosure comprises the above-mentioned display device, and

[0037] Equip yourself with a camera,

[0038] The above display panel can communicate with the camera and displays an image captured by the camera.

[0039] The vehicle of the present disclosure is equipped with the above-mentioned display system. Brief explanation of the drawing

[0040] The purpose, features, and advantages of the present disclosure will become more apparent from the following detailed description and drawings. FIG. 1 is a diagram schematically showing the configuration of a display device of the present disclosure. FIG. 2 is a cross-sectional view showing an example of the configuration of a key part of a display device according to one embodiment of the present disclosure. FIG. 3 is a cross-sectional view showing another example of the configuration of a key part of a display device according to one embodiment of the present disclosure. FIG. 4 is a cross-sectional view showing an example of the configuration of a key part of a display device according to another embodiment of the present disclosure. FIG. 5 is a cross-sectional view showing another example of the configuration of a key part of a display device according to another embodiment of the present disclosure. FIG. 6 is a diagram illustrating the projection of a virtual image in the display device of FIG. 4. FIG. 7 is a diagram illustrating the projection of a virtual image in the display device of FIG. 5. FIG. 8 is a drawing explaining the design of the optical system in the display device of FIG. 5. FIG. 9 is a cross-sectional view showing an example of the configuration of a key part of a display device according to another embodiment of the present disclosure. FIG. 10 is a drawing showing an example of the configuration of a imaging device according to one embodiment of the present disclosure. FIG. 11 is a drawing showing another example of the configuration of a imaging device according to one embodiment of the present disclosure. FIG. 12 is a drawing showing another example of the configuration of a imaging device according to one embodiment of the present disclosure. FIG. 13 is a top view illustrating another example of a display device. FIG. 14 is a top view illustrating another example of a display device. FIG. 15 is a cross-sectional view illustrating another example of a display device. FIG. 16 is a cross-sectional view illustrating another example of a display device. FIG. 17a is a drawing illustrating an optical system in another example of a display device. FIG. 17b is a drawing describing an optical system in another example of a display device. FIG. 17c is a drawing describing an optical system in another example of a display device. FIG. 17d is a drawing describing an optical system in another example of a display device. FIG. 18a is a drawing illustrating an optical system in another example of a display device. FIG. 18b is a drawing describing an optical system in another example of a display device. FIG. 18c is a drawing describing an optical system in another example of a display device. FIG. 18d is a drawing describing an optical system in another example of a display device. FIG. 19 is a graph illustrating an optical system in another example of a display device. FIG. 20 is a cross-sectional view illustrating another example of a display device. FIG. 21 is a cross-sectional view illustrating another example of a display device. FIG. 22 is a cross-sectional view illustrating another example of a display device. FIG. 23 is a cross-sectional view showing an example of the configuration of a second semi-transparent mirror. FIG. 24 is a cross-sectional view illustrating another example of a display device. FIG. 25 is a diagram illustrating how a virtual image is seen when a user is positioned in front of a display device. FIG. 26 is a diagram illustrating how a virtual image is seen when the user is not positioned in front of the display device. FIG. 27 is a diagram illustrating how a virtual image is seen when the display device is adjusted. FIG. 28 is a diagram illustrating how a virtual image is seen when the display device is adjusted. FIG. 29 is a flowchart explaining the control of the phase-setting device. FIG. 30 is a cross-sectional view showing another example of the configuration of a key part of a display device according to one embodiment of the present disclosure. FIG. 31 is a cross-sectional view showing another example of the configuration of a key part of a display device according to another embodiment of the present disclosure. FIG. 32 is a cross-sectional view showing another example of the configuration of a key part of a display device according to another embodiment of the present disclosure. FIG. 33 is a perspective view showing a cross-sectional view of another example of a display device according to one embodiment of the present disclosure. FIG. 34 is a cross-sectional view showing another example of a display device according to one embodiment of the present disclosure. FIG. 35 is a perspective view showing a cross-sectional view of another example of a display device according to one embodiment of the present disclosure. FIG. 36 is a cross-sectional view showing another example of a display device according to one embodiment of the present disclosure. FIG. 37 is a diagram showing the light path of the display light in the display device of FIG. 2. FIG. 38 is a cross-sectional view showing another example of the display device of FIG. 2. FIG. 39 is a drawing showing an example of the configuration of a display system and a vehicle according to one embodiment of the present disclosure. Specific details for implementing the invention

[0041] Conventionally, various small display devices have been proposed for use in digital rearview mirrors placed in the cabin of a vehicle, head-mounted displays mounted on the head of a user, etc. The display device described in Patent Document 1 is configured to emit display light emitted from a display panel through a plurality of optical members, such as a phase difference plate and a reflective polarizer.

[0042] Conventional display devices were prone to deformation of optical components and misalignment between them, which sometimes resulted in a decrease in display quality.

[0043] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Some of the drawings used in the following description may be 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 not illustrated, such as a retaining member of an optical system and a housing. In this specification, the orthogonal coordinate system XYZ is defined for convenience in some of the drawings. 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 depth direction.

[0044] FIGS. 1 to 39 are drawings or graphs for explaining the display device, imaging device, display system, and vehicle of the present disclosure. In FIGS. 2 to 5, 9, 15, 16, 20 to 22, 24, 30 to 32, in order to facilitate understanding of the drawings, the optical path of light incident on an optical member having light reflectivity and the optical path of light reflected by said optical member are shown offset in the height direction (Y-axis direction).

[0045] A display device (1) of one embodiment of the present disclosure comprises a display panel (2) and an optical system (3) as shown in FIG. 1. The display device (1) directs a portion of the display light emitted from the display panel (2) into the eyes of a user (22) to make visible to the user (22) as a formed image, an image, or an aerial image. The display device (1) may make visible to the user (22) the display of the display panel (2) at a position different from the position of the display panel (2) by the display light emitted from the display panel (2). In the position embodiment of the present disclosure, the display device (1) makes visible to the user (22) as a virtual image (V). The virtual image (V) may be formed at a side further away from the display device (1) as viewed from the user (22). The virtual image (V) may be an upright virtual image in which the display image displayed on the display panel (2) is enlarged. When the display device (1) is provided with a housing (see FIGS. 33–36) that accommodates a display panel (2) and an optical system (3), the virtual image (V) may be formed inside the housing or outside the housing. When viewed from the user (22), the virtual image (V) may be formed from a side further away from the display panel (2) or from a side closer to the display panel (2). When the housing has a window (37) (see FIGS. 33–36) that transmits the display light emitted from the optical system (3), the virtual image (V) may be formed from a side further away from the window (37) (light-transmitting plate (38)) or from a side closer to the window when viewed from the user (22). When the display device (1) has a touch panel (41) (see FIG. 35 and 36), the virtual image (V) may be formed at a side further away from the touch panel (41) or at a side closer to the touch panel (41) when viewed from the user (22).

[0046] Additionally, the display device (1) may be configured to allow a portion of the display light emitted from the display panel (2) to enter the eyes of the user (22) so that the user (22) can see it as a real image. The real image may be formed on a side closer to the display device (1) when viewed from the user (22). When the display device (1) is equipped with a housing (36) (see FIGS. 33–36) that accommodates 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 a side further away from the display panel (2) when viewed from the user (22) or on a side closer to the display panel (2). When the housing (36) has a window (37) (see FIGS. 33–36) that transmits the display light emitted from the optical system (3), the actual image may be formed from a side further away from the window (37) (light-transmitting plate (38)) as viewed from the user (22), or from a side closer to the window (37) (light-transmitting plate (38)). When the display device (1) has a touch panel (41) (see FIGS. 35, 36), the actual image may be formed from a side further away from the touch panel (41) as viewed from the user (22), or from a side closer to the touch panel (41).

[0047] 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. Below, we will describe the case where the display panel (2) emits S-wave polarized display light, but it is not limited to this.

[0048] The display panel (2) may be a liquid crystal panel. The liquid crystal panel may have the configuration of a known liquid crystal panel. The known liquid crystal panel may be, for example, an IPS (In-Plane Switching) type, an FFS (Fringe Field Switching) type, a VA (Vertical Alignment) type, an ECB (Electrically Controlled Birefringence) type, etc.

[0049] The display device (1) may include an irradiator (4) that irradiates the display panel (2) over an area. The irradiator (4) is also referred to as a backlight. The irradiator (4) may be an edge-light type backlight or a direct-light type backlight. An edge-light type backlight has one or more light sources arranged on the outer edge of the display panel (2), and guides light generated from the light sources to the entire back surface of the display panel (2) by a light guide plate to distribute it uniformly. A direct-light type backlight has multiple light sources arranged on the back side of the display panel (2), and irradiates the display panel (2) with light generated from the multiple light sources. The light source of the irradiator (4) may be a cold cathode fluorescent lamp, a halogen lamp, or a xenon lamp, and 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), in particular, the design of an optical component having wavelength-dependent optical properties becomes easier.

[0050] The display panel (2) is not limited to a liquid crystal panel (transmissive display panel). The display panel (2) may be a self-emissive display panel including, for example, a light-emitting diode (LED), an organic light-emitting diode (OLED), or a semiconductor laser (LD).

[0051] The optical system (3) projects the display light emitted from the display panel (2) as a virtual image (V) within the field of view of the user (22). As shown in FIG. 2, the optical system (3) may be configured to include a first phase difference plate (5), a semi-transparent mirror (6), a second phase difference plate (7), and a reflective polarizer (8). The first phase difference plate (5), the semi-transparent mirror (6), the second phase difference plate (7), and the reflective polarizer (8) are arranged in this order in the direction of emission of the display light from the display panel (2) (the forward direction in the Z-axis direction).

[0052] The first phase difference plate (5) is positioned opposite the display surface (2a) of the display panel (2). The first phase difference plate (5) is positioned spaced apart from the display surface (2a) in the direction of the emission of display light from the display panel (2). The second phase difference plate (7) is positioned spaced apart from the first phase difference plate (5) in the direction of the emission of display light from the display panel (2). The first phase difference plate (5) and the second phase difference plate (7) are quarter-wave plates. The first phase difference plate (5) and the second phase difference plate (7) impart a phase difference of 1 / 4 wavelength to the polarization plane (polarization plane in the direction of electric field vibration) of the incident light. By doing so, it becomes possible to reflect a portion of the display light emitted from the display panel (2) at the reflective polarizer (8) and cause it to be incident on the semi-transparent mirror (6).

[0053] The first phase difference plate (5) and the second phase difference plate (7) are provided with a necessary phase difference for the light passing through the first phase difference plate (5) and the second phase difference plate (7) so that the light passing through the first phase difference plate (5) and the second phase difference plate (7) is reflected by the reflective polarizer (8). That is, for example, when the polarization obtained by passing through the first phase difference plate (5) and the second phase difference plate (7) is called the second polarization, the first phase difference plate (5) and the second phase difference plate (7) may not be quarter-wave plates, but may be other wavelength plates or a combination thereof, once the second polarization is obtained. Furthermore, in this disclosure, the case where the first phase difference plate (5) and the second phase difference plate (7) are quarter-wave plates is described as an example.

[0054] Additionally, the second phase difference plate (7) can be provided with a necessary phase difference to the light that has passed through the second phase difference plate (7) so that when the light reflected from the reflective polarizer (8) and passed through the second phase difference plate (7) reaches the reflective polarizer (8) again, it passes through the reflective polarizer (8). That is, for example, when the polarization obtained by reflecting from the reflective polarizer (8) and passing through the second phase difference plate (7) is called the first polarization, the second phase difference plate (7) may be a different wavelength plate, not a quarter wavelength plate, when the first polarization is obtained.

[0055] The first phase difference plate (5) may be integrated with the display panel (2) as shown in FIG. 30. Also, "integration" may mean that two members are arranged to be in contact with each other, or that two members are joined together by an optically transparent adhesive such as OCA (Optically Clear Adhesive).

[0056] A semi-transparent mirror (6) is positioned between the first phase difference plate (5) and the second phase difference plate (7). The semi-transparent mirror (6) may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remainder (e.g., approximately 50%). The semi-transparent mirror (6) reflects a portion of the display light reflected from the reflective polarizer (8) and directs it toward the eyes of the user (22). This makes it possible for the user (22) to see the virtual image (V). As shown in FIG. 2, the semi-transparent mirror (6) may be a concave mirror having a concave reflective surface (6a) facing the second phase difference plate (7). The semi-transparent mirror (6) may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface (6a).

[0057] The semi-transparent mirror (6) is configured to include, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The semi-transparent reflective layer may be a metal thin film. The metal thin film may be composed of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, etc. The semi-transparent mirror (6) may be configured to reflect light by the semi-transparent reflective layer. The semi-transparent reflective layer may be formed on the surface facing the second phase difference plate (7) in the substrate.

[0058] The reflective polarizer (8) is positioned opposite to the surface facing the semi-transparent mirror (6) in the second phase difference plate (7). In other words, the reflective polarizer (8) is positioned at the rear end of the second phase difference plate (7) in the direction of the emission of display light from the display panel (2). The reflective polarizer (8) may transmit a portion of the incident light and reflect the remainder. In this embodiment, the reflective polarizer (8) is configured to reflect polarization having a polarization axis perpendicular to the polarization axis of the display light (P-wave polarization, also called second polarization) and to transmit polarization having a polarization axis parallel to the polarization axis of the display light (S-wave polarization, also called first polarization). By doing so, it becomes possible to make the virtual image (V) visible to the user (22). The reflective polarizer (8) may be integrated with the second phase difference plate (7), as shown in FIG. 30.

[0059] The reflective polarizer (8) may be a wire grid polarizer composed of, for example, a substrate and a plurality of metal wires (also called a metal nanowire grid) positioned on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The metal wires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal wires may be installed along one direction. The reflective polarizer (8) can transmit light components vibrating in a direction orthogonal to the grid and reflect light components vibrating in a direction parallel to the grid.

[0060] The display device (1) is equipped with a controller (43). The controller (43) is connected to each component of the display device (1) and controls each component. The controller (43) may control the irradiator (4). The controller (43) may control the display image displayed on the display panel (2) and the irradiator (4). The controller (43) may control the irradiator (4) based on the display image displayed on the display panel (2). The controller (43) may be configured to include one or more processors. The processors may include a general-purpose processor configured to read a specific program and execute a specific function, and a dedicated processor specialized for a specific processing. The processors may include a PLD (Programmable Logic Device). The controller (43) may be either a System-on-a-Chip (SoC) or a System-in-a-Package (SiP) in which one or more processors cooperate. The controller (43) includes a memory unit, and the memory unit may store various information or programs for operating each component of the display device (1). The memory unit may be composed of, for example, semiconductor memory. The memory unit may function as a work memory of the controller (43).

[0061] The optical function of the optical system (3) is described. The display panel (2) emits display light of S-wave polarization (first linear polarization (L1)). The display light of the first linear polarization (L1) emitted from the display panel (2) passes through the first phase difference plate (5) and is converted into light of the first circular polarization (C1). A portion (e.g., approximately 50%) of the first circular polarization (C1) that passes through the first phase difference plate (5) passes through the semi-transparent mirror (6). The first circular polarization (C1) that passes through the semi-transparent mirror (6) passes through the second phase difference plate (7) and is converted into light of the second linear polarization (L2) whose polarization direction is orthogonal to the first linear polarization (L1) (i.e., P-wave polarization). The light of the second linear polarization (L2) is incident on the reflective polarizer (8). As described above, the reflective polarizer (8) reflects P-wave polarized light and transmits S-wave polarized light. The second linearly polarized light (L2) incident on the reflective polarizer (8) is reflected by the reflective polarizer (8) and converted into third linearly polarized light (L3). The third linearly polarized light (L3) passes through the second phase difference plate (7) and is converted into second circularly polarized light (C2). A portion (e.g., approximately 50%) of the second circularly polarized light (C2) that passes through the second phase difference plate (7) is reflected by the semi-transparent mirror (6) and converted into third circularly polarized light (C3). The light of the third circular polarization (C3) passes through the second phase difference plate (7) and is converted into the light of the fourth linear polarization (L4), which has a polarization direction parallel to the first linear polarization (L1) (i.e., S-wave polarization). The light of the fourth linear polarization (L4) passes through the reflective polarizer (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).

[0062] The first phase difference plate (5), the semi-transparent mirror (6), the second phase difference plate (7), and the reflective polarizer (8) are maintained in relative positions by being held in a holding member (not shown). Air is interposed between the first phase difference plate (5) and the second phase difference plate (7) (i.e., between the first phase difference plate (5) and the semi-transparent mirror (6) and between the semi-transparent mirror (6) and the second phase difference plate (7)). Since the display device (1) is configured not to install a member made of a resin material such as a polymer between the first phase difference plate (5) and the second phase difference plate (7), the risk of deformation of the semi-transparent mirror (6) and misalignment of the positions of the semi-transparent mirror (6), the first phase difference plate (5), and the second phase difference plate (7) when the resin material is cured during the manufacturing process of the display device (1) can be reduced. In addition, resin materials such as polymers have material-specific retardation, which can reduce the risk of changing the polarization state of light transmitted through the resin material. As a result, the degradation of the display quality can be reduced.

[0063] Since the optical system (3) is a one-axis (on-axis) type optical system in which the optical axis of the incident light and the optical axis of the outgoing light substantially coincide, the space occupied by the optical system (3) can be reduced, and as a result, the display device (1) can be miniaturized. In addition, since the optical system (3) is a one-axis type, the distortion of the virtual image (V) seen by the user (22) and the brightness deviation can be reduced, and the design of the optical system (3) becomes easier.

[0064] The light path length of the light emitted from the display panel (2), passing through the semi-transparent mirror (6), and reflected by the reflective polarizer (8) to reach the semi-transparent mirror (6) may be shorter than the focal length of the semi-transparent mirror (6). In this case, the virtual image (V) can be seen by the user (22). The light path length of the light emitted from the display panel (2), passing through the semi-transparent mirror (6), and reflected by the reflective polarizer (8) to reach the semi-transparent mirror (6) may be longer than the focal length of the semi-transparent mirror (6). In this case, the real image can be seen by the user (22).

[0065] In FIG. 2, for ease of understanding of the drawing, the optical path of light incident on the reflective polarizer (8) and the optical path of light reflected from the reflective polarizer (8) are shown offset in the height direction (Y-axis direction), and the optical path of light incident on the semi-transparent mirror (6) and the optical path of light reflected from the semi-transparent mirror (6) are shown offset in the height direction (Y-axis direction); however, in reality, the display light emitted from the display panel (2) propagates substantially along a single axis as shown in FIG. 37. This is also true for the optical paths shown in FIGs. 3–5, 9, 15, 16, 20–22, 24, and 30–32.

[0066] As shown in FIG. 38, the display device (1) may replace the first phase difference plate (5), the semi-transparent mirror (6), the second phase difference plate (7), and the reflective polarizer (8) with a convex lens (42). The display device (1) may have an optical path length from the display panel (2) to the convex lens (42) that is shorter than the focal length of the convex lens (42). In this case, the virtual image (V) of the user (22) can be seen. The display device (1) may have an optical path length from the display panel (2) to the convex lens (42) that is longer than the focal length of the convex lens (42). In this case, the real image of the user (22) can be seen.

[0067] The display panel (2) may display a mixed image including a left-eye image and a right-eye image having a parallax difference from each other, and may emit display light of the mixed image. The display device (1) may be equipped with an optical element (9) located in the light path of the display light emitted from the display panel (2), as shown in FIG. 3. The optical element (9) is configured to direct a portion of the display light of the mixed image to one side of the user's (22) left eye and right eye, and to direct another portion of the display light to the other side of the user's (22) left eye and right eye. By defining the respective light beam directions of the display light of the left-eye image and the display light of the right-eye image, the optical element (9) is configured to direct at least a portion of the display light of the left-eye image to the user's (22) left eye and at least a portion of the display light of the right-eye image to the user's (22) right eye. By doing so, the display device (1) makes it possible to make the user (22) see a three-dimensional image.

[0068] The optical element (9) may direct a portion of the display light of the mixed image to one side of the user's (22) left eye and right eye, and direct another portion of the display light to the other side of the user's (22) left eye and right eye, and may be, for example, a parallax barrier or a lenticular lens. The parallax barrier may be composed of a liquid crystal panel. The position of the optical element (9) is arbitrary within the display device (1). The optical element (9) may be located between the display panel (2) and the first phase difference plate (5), may be located at the rear end of the reflective polarizer (8) in the direction of the display light emission, or may be located between the semi-transparent mirror (6) and the second phase difference plate (7).

[0069] Next, a display device according to another embodiment of the present disclosure will be described. Since the display device of this embodiment differs from the display device of the above embodiment in the configuration of the optical system, and is otherwise identical in configuration, the same reference numerals are attached to identical components, and a detailed description is omitted.

[0070] As shown in FIG. 4, the display device (1A) of the present embodiment comprises 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 a display light emitted from the display panel (2) as a virtual image (V) within the field of view of the user (22).

[0071] The optical system (10) is configured to include a first semi-transparent mirror (11), a first phase difference plate (12), a second semi-transparent mirror (13), a second phase difference plate (14), and a polarizing plate (15). The first semi-transparent mirror (11), the first phase difference plate (12), the second semi-transparent mirror (13), the second phase difference plate (14), and the polarizing plate (15) are arranged in this order in the direction of emission of display light from the display panel (2).

[0072] The first phase difference plate (12) is positioned opposite the reflective surface (11a) of the first semi-transparent mirror (11). The first phase difference plate (12) is positioned spaced apart from the display surface (2a) in the direction of the emission of display light from the display panel (2). The second phase difference plate (14) is positioned spaced apart from the first phase difference plate (12) in the direction of the emission of display light. The first phase difference plate (12) and the second phase difference plate (14) are quarter-wave plates.

[0073] The first semi-transparent mirror (11) is located between the display panel (2) and the first phase difference plate (12). The first semi-transparent mirror (11) may transmit a portion of the incident light and reflect the remainder. As shown in FIG. 4, the first semi-transparent mirror (11) is a concave mirror having a concave reflective surface (11a) facing the first phase difference plate (12). In this embodiment, the first semi-transparent mirror (11) may be configured to transmit S-wave polarized light and reflect P-wave polarized light. The first semi-transparent mirror (11) may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface (11a).

[0074] The first semi-transparent mirror (11) may be composed, for example, of a substrate and a plurality of metal wires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal wires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal wires may be installed along one direction. The first semi-transparent mirror (11) can transmit light components vibrating in a direction orthogonal to the grid and reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the first phase difference plate (12) side of the substrate. In addition, in this example, the first semi-transparent mirror (11) is given the function of reflection polarization by a metal nanowire grid, but the first semi-transparent mirror (11) can be a simple half mirror and a separate reflection polarizer can be installed.

[0075] The second semi-transparent mirror (13) is positioned between the first phase difference plate (12) and the second phase difference plate (14). The second semi-transparent mirror (13) may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remainder (e.g., approximately 50%). The second semi-transparent mirror (13) may be a planar mirror positioned such that its reflective surface (13a) faces the first phase difference plate (12), as shown in FIG. 4. The second semi-transparent mirror (13) is also referred to as a planar half mirror. The second semi-transparent mirror (13) may be integrated with the first phase difference plate (12) and / or the second phase difference plate (14), as shown in FIG. 31.

[0076] The second semi-transparent mirror (13) may be composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be composed of, for example, inorganic glass, resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent reflective layer may be a metal thin film. The metal thin film may be composed of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, etc.

[0077] The polarizing plate (15) is positioned opposite to the surface facing the second semi-transparent mirror (13) in the second phase difference plate (14). In other words, the polarizing plate (15) is positioned at the rear end of the second phase difference plate (14) in the direction of the emission of display light from the display panel (2). The polarizing plate (15) may transmit a portion of the incident light and absorb the remainder. In this embodiment, the polarizing plate (15) is configured to transmit P-wave polarized light and absorb S-wave polarized light. As shown in FIG. 31, the polarizing plate (15) may be integrated with the second phase difference plate (14).

[0078] 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, or a dye-based polarizing plate in which a dichromatic organic dye is adsorbed and oriented on a PVA film.

[0079] The optical function of the optical system (10) is described. Display light of S-wave polarization (first linear polarization (L1)) emitted from the display panel (2) passes through the first semi-transparent mirror (11). The display light of the first linear polarization (L1) passes through the first phase difference 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 semi-transparent mirror (13). A portion of the light of the first circular polarization (C1) (e.g., approximately 50%) is reflected by the second semi-transparent mirror (13) and is converted into light of the second circular polarization (C2). The light of the second circularly polarized light (C2) passes through the first phase difference plate (12) and is converted into the light of the second linearly polarized light (L2), the polarization direction of which is orthogonal to the first linearly polarized light (L1) (i.e., P-wave polarized). The light of the second linearly polarized light (L2) is reflected by the first semi-transparent mirror (11) and is converted into the light of the third linearly polarized light (L3), the polarization direction of which is orthogonal to the first linearly polarized light (L1). The light of the third linearly polarized light (L3) passes through the first phase difference plate (12) and is converted into the light of the third circularly polarized light (C3). A portion of the light of the third circularly polarized light (C3) (e.g., approximately 50%) passes through the second semi-transparent mirror (13). The light of the third circularly polarized light (C3) that passes through the second semi-transparent mirror (13) passes through the second phase difference plate (14) and is converted into the light of the fourth linearly polarized light (L4), the polarization direction of which is orthogonal to the first linearly polarized light (L1) (i.e., P-wave polarization). The light of the fourth linearly polarized light (L4) passes through the polarizing plate (15) and is emitted to the outside.

[0080] The remainder of the light of the first circularly polarized light (C1) (e.g., approximately 50%) passes through the second semi-transparent mirror (13) and then through the second phase difference plate (14), and is converted into the light of the fifth linearly polarized light (L5), which has a polarization direction parallel to the first linearly polarized light (L1) (i.e., S-wave polarization). Since the light of the fifth linearly polarized light (L5) is absorbed by the polarizer (15), it is not emitted to the outside. In other words, the light of the fifth linearly polarized light (L5) is light that has low transmission through the polarizer (15). Therefore, the amount of light (luminance) of the light emitted from the display device (1A) is, for example, approximately 25% of the amount of light (luminance) of the display light emitted from the display panel (2).

[0081] Additionally, although the above description describes an example where the first phase difference plate (12) and the second phase difference plate (14) are quarter-wave plates, the first phase difference plate (12) and the second phase difference plate (14) may not be quarter-wave plates, but may be other wavelength plates, or a combination thereof, if some light is absorbed by the polarizing plate (15) and other light passes through the polarizing plate (15). Furthermore, the first phase difference plate (12) and the second phase difference plate (14) may not be quarter-wave plates, but may be other wavelength plates, or a combination thereof, if some light is reflected by the first semi-transparent mirror (11) and other light passes through the first semi-transparent mirror (11).

[0082] The first semi-transparent mirror (11), the first phase difference plate (12), the second semi-transparent mirror (13), the second phase difference plate (14), and the polarizing plate (15) are maintained in relative positions by being held in a holding member (not shown). Air is interposed between the first semi-transparent mirror (11) and the first phase difference plate (12). Since the display device (1A) is configured not to install a member made of a resin material such as a polymer between the first semi-transparent mirror (11) and the first phase difference plate (12), the risk of deformation of the first semi-transparent mirror (11) and misalignment of the first semi-transparent mirror (11) and the first phase difference plate (12) occurring when the resin material is cured during the manufacturing process of the display device (1A) can be reduced. As a result, the deterioration of the display quality can be reduced.

[0083] Since the optical system (10) is a one-axis (on-axis) type optical system in which the optical axis of the incident light and the optical axis of the outgoing light substantially coincide, the space occupied by the optical system (10) can be reduced, and as a result, the display device (1A) can be miniaturized. In addition, since the optical system (10) is a one-axis type, the distortion of the virtual image (V) seen by the user (22) and the brightness deviation can be reduced, and the design of the optical system (10) becomes easier.

[0084] The display device (1A) may be equipped with an optical element (9), just like the display device (1). In this case, the display device (1A) can make it possible for the user (22) to see a three-dimensional image. The optical element (9) may be located between the display panel (2) and the first semi-transparent mirror (11), may be located at the rear end of the polarizer (15) in the direction of the emission of the display light, or may be located between the first semi-transparent mirror (11) and the first phase difference plate (12).

[0085] Next, another example of a display device (1A) will be described. The display device (1A') of this example differs from the display device (1A) described above in that the configuration (shape) of the second semi-transparent mirror is different, but otherwise the configuration is the same. Therefore, the same reference numerals are attached to the identical configurations, and a detailed description is omitted.

[0086] As shown in FIG. 5, the display device (1A') of the present example comprises a display panel (2) and an optical system (10). The optical system (10) is configured to include a first semi-transparent mirror (11), a first phase difference plate (12), a second semi-transparent mirror (13'), a second phase difference plate (14), and a polarizing plate (15). The first semi-transparent mirror (11), the first phase difference plate (12), the second semi-transparent mirror (13'), the second phase difference plate (14), and the polarizing plate (15) are arranged in this order in the direction of emission of display light from the display panel (2).

[0087] The second semi-transparent mirror (13') has a convex reflective surface (13'a), and the reflective surface (13'a) faces the first phase difference plate (12). The second semi-transparent mirror (13') is also referred to as a convex half mirror. The second semi-transparent mirror (13') may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remainder (e.g., approximately 50%).

[0088] The second semi-transparent mirror (13') may be composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be composed of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, a polycarbonate resin, etc. The semi-transparent reflective layer may be a metal thin film. The metal thin film may be composed of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, etc.

[0089] The optical system (10) may be configured such that the focal length of the second semi-transparent mirror (13') is greater than the distance between the display panel (2) and the second semi-transparent mirror (13'). In other words, the optical system (10) may be configured such that the second semi-transparent mirror (13') projects a reduced virtual image (Q') (see FIG. 7) of an object (i.e., the display surface (2a)). Additionally, the optical system (10) may be configured such that the focal length of the first semi-transparent mirror (11) is greater than the distance between the virtual image (Q') and the first semi-transparent mirror (11). In other words, the optical system (10) may be configured such that the first semi-transparent mirror (11) projects an enlarged virtual image (V) of an object (i.e., the virtual image (Q')). In this case, it is possible to adjust the magnification ratio and projection distance of the virtual image (V) while reducing the thickness of the optical system (10) in the depth direction (Z-axis direction).

[0090] The first semi-transparent mirror (11), the first phase difference plate (12), the second semi-transparent mirror (13'), the second phase difference plate (14), and the polarizing plate (15) are maintained in relative positions by being held in a holding member (not shown). Air is interposed between the first semi-transparent mirror (11) and the first phase difference plate (12). Since the display device (1A') is configured not to install a member made of a resin material such as a polymer between the first semi-transparent mirror (11) and the first phase difference plate (12), the risk of deformation of the first semi-transparent mirror (11) and misalignment of the first semi-transparent mirror (11) and the first phase difference plate (12) occurring when the resin material is cured during the manufacturing process of the display device (1A') can be reduced. As a result, the deterioration of the display quality can be reduced.

[0091] Since the optical system (10) is a one-axis (on-axis) type optical system in which the optical axis of the incident light and the optical axis of the outgoing light substantially coincide, the space occupied by the optical system (10) can be reduced, and as a result, the display device (1A') can be miniaturized. In addition, since the optical system (10) is a one-axis type, the distortion of the virtual image (V) seen by the user (22) and the brightness deviation can be reduced, and the design of the optical system (10) becomes easier.

[0092] The display device (1A') may be equipped with an optical element (9), and in this case, it is possible to make the user (22) see a three-dimensional virtual image (V).

[0093] In addition, according to the display device (1A') of the present example, the optical system (10) can be made thin in the depth direction (Z-axis direction), so a thin display device can be provided. Below, with reference to FIGS. 6 and 7, the thinning of the optical system (10) will be explained. Also, since the first semi-transparent mirror (11) of the display device (1A, 1A') has a reflective surface (11a) that reflects the display light emitted outwardly and has a concave shape, the first semi-transparent mirror (11) may be referred to as a concave mirror below. Since the second semi-transparent mirror (13) of the display device (1A) has a reflective surface (13a) that reflects the display light emitted outwardly and has a flat shape, the second semi-transparent mirror (13) may be referred to as a flat mirror below. Since the second semi-transparent mirror (13') of the display device (1A') has a reflective surface (13'a) that reflects the display light emitted outwardly, the second semi-transparent mirror (13') may be referred to as a convex mirror below. Additionally, 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).

[0094] FIG. 6 is a diagram illustrating the projection of a virtual image (V) in a display device (1A). In FIG. 6, the irradiator (4) and optical members (first phase difference plate (12), second phase difference plate (14), and polarizer (15)) that do not contribute to the projection distance (virtual image distance) and magnification ratio of the virtual image (V) are omitted. Additionally, the concave mirror (11) is positioned so as to be in contact with the display panel (2) so that the distance between the display panel (2) and the concave mirror (11) can be considered as "0". In the following description, the focal length of the concave mirror (11) is denoted as f, and the distance between the concave mirror (11) and the flat 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).

[0095] The display device (1A) is configured to project a virtual image (Q) of a display surface (2a) formed by a flat mirror (13) by enlarging it with a concave mirror (11) and projecting it as a virtual image (V). As shown in FIG. 6, the virtual image (Q) is located on the opposite side of the concave mirror (11) with respect to the flat mirror (13), and the distance from the flat mirror (13) is a / 2. The virtual image (Q) becomes an image of the display surface (2a) magnified by an equal magnification (1x).

[0096] The virtual image distance b and virtual image magnification m of the virtual image (V) are each expressed by the following equations (1) and (2). Also, the virtual image distance b is the distance between the virtual image (V) and the concave mirror (11), and the virtual image magnification m is the magnification ratio of the virtual image (V) with respect to the display surface (2a).

[0097] b=1 / (1 / a-1 / f) … (1)

[0098] m=b / a … (2)

[0099]

[0100] Table 1 shows configuration examples 1 and 2 of a display device (1A). The units of the focal length f, thickness a / 2, and 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 a 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), and 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).

[0101] FIG. 7 is a diagram illustrating the projection of a virtual image (V) in a display device (1A'). In FIG. 7, the irradiator (4) and optical members (first phase difference plate (12), second phase difference plate (14), and polarizer (15)) that do not contribute to the projection distance (virtual image distance) and magnification ratio of the virtual image (V) are omitted. Additionally, the concave mirror (11) is positioned so as to be in contact with the display panel (2) so that the distance between the display panel (2) and the concave mirror (11) can be considered as "0". In the following description, the focal length of the convex mirror (13') is denoted as f', the focal length of the concave mirror (11) as f'', and the distance between the concave mirror (11) and the convex mirror (13') as a' / 2. The distance a' / 2 corresponds to the thickness of the optical system (10) of the display device (1A').

[0102] The display device (1A') is configured to magnify the virtual image (Q') of the display surface (2a) formed by the convex mirror (13') using the concave mirror (11) and project it as a virtual image (V). As shown in FIG. 7, the virtual image (Q') is located on the opposite side of the concave mirror (11) with respect to the convex mirror (13'). The distance b' between the virtual image (Q') and the convex mirror (13') is expressed by the following equation (3). The magnification ratio m' of the virtual image (Q') with respect to the display surface (2a) is expressed by the following equation (4). As is evident from equation (3), b' <a' / 2이기 때문에, 허상(Q')의 확대 배율 m'는 1 미만이 된다. 따라서, 허상(Q')은 표시면(2a)의 축소 허상이다.

[0103] b'=1 / {1 / f'+1 / (a' / 2)} … (3)

[0104] m'=b' / (a' / 2) … (4)

[0105] The virtual image distance b'' and virtual image magnification m'' of the virtual image (V) are respectively represented by the following equations (5) and (6). Also, the virtual image distance b'' is the distance between the virtual image (V) and the concave mirror (11), and the virtual image magnification m'' is the magnification ratio of the virtual image (V) with respect to the display surface (2a).

[0106] b''=1 / {1 / (a' / 2+b')-1 / f''} … (5)

[0107] m''=(b' / (a' / 2))×b'' / (a' / 2+b') … (6)

[0108] Table 2 shows configuration examples 3 and 4 of a display device (1A'). The units of the focal lengths f', f'', thickness a' / 2, and virtual image distance b'' shown in Table 2 are "mm". 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, just like configuration examples 1 and 2. As shown in Table 2, when the optical system (10) includes a convex mirror (13'), the optical system (10) having a thickness a' / 2 of 32 mm can make the virtual image distance b'' 200 mm and the virtual image magnification m'' 2, just like in Configuration Example 1 (see Configuration Example 3), and the optical system (10) having a thickness a' / 2 of 25.5 mm can make the virtual image distance b'' 200 mm and the virtual image magnification m'' 3, just like in Configuration Example 2 (see Configuration Example 4). Accordingly, the optical system (10) can be made thin according to the display device (1A'), and as a result, a thin display device can be provided.

[0109]

[0110] The display device (1A') can design an optical system (10) to realize the virtual image distance b'', virtual image magnification m'', and thickness a' / 2, respectively, when each value is given.

[0111] Hereinafter, with reference to FIG. 8, the design of the optical system (10) of the display device (1A') will be described. In FIG. 8, as in FIG. 7, the irradiator (4), the first phase difference plate (12), the second phase difference plate (14), and the polarizer (15) are omitted. Additionally, the concave mirror (11) is positioned to be in contact with the display panel (2) so that the distance between the display panel (2) and the concave mirror (11) can be considered as "0". In the following description, the thickness of the optical system (10) 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. Furthermore, the magnification ratio of the virtual image (Q') relative to the display surface (2a) is denoted as m1, and the magnification ratio of the virtual image (V) relative to the virtual image (Q') is denoted as m2. In addition, 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.

[0112] The magnification ratio M of the virtual image (V) for the display surface (2a) is expressed as the product of the magnification ratio m1 and the magnification ratio m2, as shown in the following equation (7). Additionally, the distance a2 between the concave mirror (11) and the virtual image (Q') is expressed as the sum of the thickness a1 and the distance b1, as shown in the following equation (8).

[0113] M=m1×m2 … (7)

[0114] a2=a1+b1 … (8)

[0115] If the thickness a1 of the optical system (10) is defined as T and the virtual image distance (i.e., the distance b1 between the concave mirror (11) and the virtual image (V)) is defined as D, the magnification ratio M is expressed by the following equation (9).

[0116] M=m1×m2

[0117] =(b1 / a1)×(b2 / a2)

[0118] =(b1 / T)×(D / a2) … (9)

[0119] As a result of substituting the following equation (10), which holds true for the distance b1 between the convex mirror (13') and the virtual image (Q'), into equation (9), the following equation (11) is obtained.

[0120] 1 / a1=1 / b1+1 / f1 … (10)

[0121] M=f1×(1+D / f2) / (T+f1) … (11)

[0122] In addition, the following equation (12), which is established with respect to the distance b2 between the concave mirror (11) and the virtual image (V), is substituted into equation (8), and the following equation (13) is obtained.

[0123] 1 / a²=1 / b²+1 / f² … (12)

[0124] D×f2 / (D+f2)=T+T×f1 / (T+f1) … (13)

[0125] From equations (9) and (13), the focal length f1 of the convex mirror (13') and the focal length f2 of the concave mirror (11) are obtained as shown in the following equations (14) and (15). Also, A in equation (15) is represented by the following equation (16).

[0126] f1=M×T×T / (D-2×M×T) … (14)

[0127] f2=D×A / (MA) … (15)

[0128] A=f1 / (T+f1) … (16)

[0129] As can be seen from the above calculation, the display device (1A') can determine focal lengths f1 and f2 (i.e., design the optical system (10)) to realize them when the values ​​of the magnification ratio M, thickness T, and virtual image distance D are given, respectively.

[0130] The light path length of the light emitted from the display panel (2), passing through the first semi-transparent mirror (11), and reflected by the second semi-transparent mirror (13, 13') to reach the first semi-transparent mirror (11) may be shorter than the focal length of the first semi-transparent mirror (11). In this case, the virtual image (V) can be seen by the user (22). The light path length of the light emitted from the display panel (2), passing through the first semi-transparent mirror (11), and reflected by the second semi-transparent mirror (13, 13') to reach the first semi-transparent mirror (11) may be longer than the focal length of the first semi-transparent mirror (11). In this case, the real image can be seen by the user (22).

[0131] Next, a display device according to another embodiment of the present disclosure will be described. Since the display device of this embodiment differs from the display device of the above embodiment in the configuration of the optical system, but otherwise has the same configuration, the same reference numerals are attached to the same components, and a detailed description is omitted.

[0132] The display device (1B) of the present embodiment is equipped with a display panel (2) and an optical system (16), as shown in FIG. 9.

[0133] The optical system (16) includes a first semi-transparent mirror (17), a first phase difference plate (18), a second semi-transparent mirror (19), a second phase difference plate (20), and a third semi-transparent mirror (21). The first semi-transparent mirror (17), the first phase difference plate (18), the second semi-transparent mirror (19), the second phase difference plate (20), and the third semi-transparent mirror (21) are arranged in this order in the direction of emission of display light from the display panel (2).

[0134] The first phase difference plate (18) is positioned opposite the reflective surface (17a) of the first semi-transparent mirror (17). The first phase difference plate (18) is positioned spaced apart from the display surface (2a) in the direction of the emission of display light from the display panel (2). The second phase difference plate (20) is positioned spaced apart from the first phase difference plate (12) in the direction of the emission of display light. The first phase difference plate (18) and the second phase difference plate (20) are quarter-wave plates.

[0135] The first semi-transparent mirror (17) is positioned between the display panel (2) and the first phase difference plate (18). The first semi-transparent mirror (17) may transmit a portion of the incident light and reflect the remainder. In this embodiment, the first semi-transparent mirror (17) may be configured to transmit S-wave polarized light and reflect P-wave polarized light. As shown in FIG. 9, the first semi-transparent mirror (17) may be a concave mirror having a concave reflective surface (17a) facing the first phase difference plate (18). The first semi-transparent mirror (17) may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the reflective surface (17a).

[0136] The first semi-transparent mirror (17) is configured to include, for example, a substrate and a plurality of metal wires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal wires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal wires may be installed along one direction. The first semi-transparent mirror (17) can transmit light components vibrating in a direction orthogonal to the grid and reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on a surface facing the first phase difference plate (18) in the substrate. In addition, in this example, the first semi-transparent mirror (11) is given the function of reflection polarization by a metal nanowire grid, but the first semi-transparent mirror (11) can be a simple half mirror and a separate reflection polarizer can be installed.

[0137] The second semi-transparent mirror (19) is positioned between the first phase difference plate (18) and the second phase difference plate (20). The second semi-transparent mirror (13) may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remainder (e.g., approximately 50%). The second semi-transparent mirror (19) may be a planar mirror having a reflective surface (19a) facing the first phase difference plate (18) and a reflective surface (19b) facing the second phase difference plate (20), as shown in FIG. 9. The second semi-transparent mirror (19) is also referred to as a planar half mirror. The second semi-transparent mirror (19) may be integrated with the first phase difference plate (18) and / or the second phase difference plate (20), as shown in FIG. 32.

[0138] The second semi-transparent mirror (19) may be composed of, for example, a substrate and a semi-transparent layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% with respect to light in the visible light band. The substrate may be composed of, for example, inorganic glass, resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent layer may be a metal thin film. The metal thin film may be composed of, for example, a metal material such as aluminum, chromium, etc. The semi-transparent layer is not limited to a metal thin film and may be, for example, a dielectric multilayer film, etc. The first phase difference plate (18) and the second phase difference plate (20) may be fixed to the second semi-transparent mirror (19) by an optically transparent adhesive such as OCA (Optically Clear Adhesive). The adhesive may be a material with low retardation.

[0139] The third semi-transparent mirror (21) is positioned opposite to the surface of the second phase difference plate (20) that is opposite to the surface of the second semi-transparent mirror (19). The third semi-transparent mirror (21) is positioned at the rear end of the second phase difference plate (20) in the direction of the emission of display light from the display panel (2). The third semi-transparent mirror (21) may transmit a portion of the incident light and reflect the remainder. In this embodiment, the third semi-transparent mirror (21) may be configured to reflect S-wave polarized light and transmit P-wave polarized light. As shown in FIG. 9, the third semi-transparent mirror (21) may be a concave mirror having a concave reflective surface (21a) that is opposite to the second phase difference plate (20). The third semi-transparent mirror (21) may include a spherical shape, an aspherical shape, or a free-form shape on at least a portion of the reflective surface (21a).

[0140] The third semi-transparent mirror (21) is configured to include, for example, a substrate and a plurality of metal wires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal wires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal wires may be installed along one direction. The third semi-transparent mirror (21) can transmit light components vibrating in a direction orthogonal to the grid and reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on a surface facing the second phase difference plate (20) in the substrate. In addition, in this example, the third semi-transparent mirror (21) is given the function of reflection polarization by means of a metal nanowire grid, but the third semi-transparent mirror (21) can be made into a simple half mirror and a separate reflection polarizer can be installed.

[0141] The optical function of the optical system (16) is described. In the display device (1B), the display light emitted from the display panel (2) travels along path (P1) or path (P2) and may be emitted outward. First, the light traveling along path (P1) is described. The display light of S-wave polarization (first linear polarization (L1)) emitted from the display panel (2) passes through the first semi-transparent mirror (17). The light of the first linear polarization (L1) passes through the first phase difference plate (18) and is converted into light of the first circular polarization (C1). The light of the first circular polarization (C1) is incident on the second semi-transparent mirror (19). A portion of the light of the first circular polarization (C1) (e.g., approximately 50%) is reflected by the second semi-transparent mirror (19) and converted into light of the second circular polarization (C2). The light of the second circularly polarized light (C2) passes through the first phase difference plate (18) and is converted into the light of the second linearly polarized light (L2), the polarization direction of which is orthogonal to the first linearly polarized light (L1) (i.e., P-wave polarized). The light of the second linearly polarized light (L2) is reflected by the first semi-transparent mirror (17) and is converted into the light of the third linearly polarized light (L3), the polarization direction of which is orthogonal to the first linearly polarized light (L1) (i.e., P-wave polarized). The third linearly polarized light (L3) passes through the first phase difference 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 semi-transparent mirror (19). A portion (e.g., approximately 50%) of the light of the third circularly polarized light (C3) passes through the second semi-transparent mirror (19). The light of the third circularly polarized light (C3) that passes through the second semi-transparent mirror (19) passes through the second phase difference plate (20) and is converted into the light of the fourth linearly polarized light (L4), the polarization direction of which is orthogonal to the first linearly polarized light (L1) (i.e., P-wave polarization). The light of the fourth linearly polarized light (L4) passes through the third semi-transparent mirror (21) and is emitted to the outside.

[0142] Next, the light traveling along path (P2) is described. The remainder (e.g., approximately 50%) of the first circularly polarized light (C1) incident on the second semi-transparent mirror (19) passes through the second semi-transparent mirror (19). The first circularly polarized light (C1) that passes through the second semi-transparent mirror (19) passes through the second phase difference plate (20) and is converted into fifth linearly polarized light (L5) whose polarization direction is parallel to the first linearly polarized light (L1) (i.e., S-wave polarized). The fifth linearly polarized light (L5) is reflected by the third semi-transparent mirror (21) and is converted into sixth linearly polarized light (L6) whose polarization direction is parallel to the first linearly polarized light (L1) (i.e., S-wave polarized). The light of the sixth linear polarization (L6) passes through the second phase difference plate (20) and is converted into the light of the fourth circular polarization (C4). The light of the fourth circular polarization (C4) is incident on the second semi-transparent mirror (19). A portion of the light of the fourth circular polarization (C4) (e.g., approximately 50%) is reflected by the second semi-transparent mirror (19) and converted into the light of the fifth circular polarization (C5). The light of the fifth circular polarization (C5) passes through the second phase difference plate (20) and is converted into the light of the seventh linear polarization (L7), the polarization direction of which is orthogonal to the first linear polarization (L1) (i.e., P-wave polarization). The light of the seventh linear polarization (L7) passes through the third semi-transparent mirror (21) and is emitted to the outside.

[0143] 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 outward. As a result, the amount of light (luminance) of the light emitted from the display device (1B) is, for example, approximately 50% of the amount of light (luminance) of the display light emitted from the display panel (2). The display device (1B) can increase the light utilization efficiency and improve the luminance of the light emitted outward.

[0144] Additionally, although the above description describes an example where the first phase difference plate (18) and the second phase difference plate (20) are quarter-wave plates, if some light is reflected by the first semi-transparent mirror (17) and other light passes through the first semi-transparent mirror (17), the first phase difference plate (18) and the second phase difference plate (20) may not be quarter-wave plates, but may be other wave plates or a combination thereof. Furthermore, if some light is reflected by the third semi-transparent mirror (21) and other light passes through the third semi-transparent mirror (21), the first phase difference plate (18) and the second phase difference plate (20) may not be quarter-wave plates, but may be other wave plates or a combination thereof.

[0145] The first semi-transparent mirror (17), the first phase difference plate (18), the second semi-transparent mirror (19), the second phase difference plate (20), and the third semi-transparent mirror (21) are maintained in relative positions to each other by being maintained in a maintaining member (not shown). Air is interposed between the first semi-transparent mirror (17) and the first phase difference plate (18), and between the third semi-transparent mirror (21) and the second phase difference plate (20). Since the display device (1B) is configured such that no member made of a resin material such as a polymer is installed between the first semi-transparent mirror (17) and the first phase difference plate (18) and between the third semi-transparent mirror (21) and the second phase difference plate (20), the risk of deformation of the first semi-transparent mirror (11) and misalignment of the first semi-transparent mirror (11) and the first phase difference plate (12) can be reduced. As a result, the deterioration of the display quality can be reduced.

[0146] Since the optical system (16) is a one-axis (on-axis) type optical system in which the optical axis of the incident light and the optical axis of the outgoing light substantially coincide, the space occupied by the optical system (16) can be reduced, and as a result, the display device (1B) can be miniaturized. In addition, since the optical system (16) is a one-axis type, the distortion and brightness deviation of the virtual image (V) seen by the user (22) can be reduced, and the design of the optical system (16) becomes easier.

[0147] The display device (1B) may be configured such that the focal length of the first semi-transparent mirror (17) and the focal length of the third semi-transparent mirror (21) are the same, and the second semi-transparent mirror (19) is a flat mirror. In this case, in an imaging device including the display device (1B), the virtual image formed by light traveling along path (P1) and the virtual image formed by light traveling along path (P2) substantially coincide, so the quality of the display can be improved.

[0148] The display device (1B) may have a light path length that is emitted from the display panel (2), passes through the first semi-transparent mirror (17), is reflected by the second semi-transparent mirror (19), and reaches the first semi-transparent mirror (17), which is smaller than the focal length of the first semi-transparent mirror (17), and may also have a light path length that is emitted from the display panel (2), passes through the first semi-transparent mirror (17), passes through the second semi-transparent mirror (19), and reaches the third semi-transparent mirror (21), which is smaller than the focal length of the first semi-transparent mirror (17). In this case, the virtual image (V) can be made visible to the user (22). The display device (1B) is emitted from the display panel (2), passes through the first semi-transparent mirror (17), is reflected by the second semi-transparent mirror (19), and the optical path length of the light reaching the first semi-transparent mirror (17) is greater than the focal length of the first semi-transparent mirror (17). Additionally, the optical path length of the light emitted from the display panel (2), passes through the first semi-transparent mirror (17) and the second semi-transparent mirror (19), and reaches the third semi-transparent mirror (21) may also be greater than the focal length of the first semi-transparent mirror (17). In this case, the actual image can be seen by the user (22).

[0149] Next, an imaging device according to one embodiment of the present disclosure will be described. The imaging device (100) of the present embodiment is equipped with display devices (1, 1A, 1A', 1B). The imaging device (100) makes display light emitted from a display panel (2) visible to a user (22) as a virtual image (V). Since the imaging device (100) includes display devices (1, 1A, 1A', 1B), a compact imaging device can be realized, and a virtual image (V) with improved display quality can be made visible to the user (22). In particular, if the imaging device (100) includes a display device (1A'), a thin imaging device can be realized. The imaging device (100) may make display light emitted from a display panel (2) visible to the user (22) as a real image.

[0150] As shown in FIG. 10, the image capturing device (100) may be mounted on a moving body (23). The moving body (23) may be a vehicle. FIG. 10 shows a case where the vehicle is a passenger car, but the vehicle is not limited to a passenger car and may be a vehicle such as a truck, bus, or trolleybus. The position of the display device (1, 1A, 1A', 1B) is arbitrary within the moving body (23). The display device (1, 1A, 1A', 1B) may be located on the dashboard (instrument panel), inside the dashboard, on the ceiling of the cabin, on the A-pillar, etc. The image capturing device (100) may have a part of its configuration combined with other devices or parts provided by the moving body (23).

[0151] As shown in FIG. 10, the imaging device (100) may be equipped with a camera (102) that captures the rear view of the moving body (23). The camera (102) may include, for example, a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary Metal Oxide Semiconductor) imaging element. The imaging device (100) and the camera (102) are connected via wired communication and / or wireless communication. If 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).

[0152] The imaging device (100) may be configured to display at least a portion of the captured image captured by the camera (102) on a display panel (2). In this case, the imaging device (100) can make the rear view of the moving body (23) visible to the user (22) (driver of the moving body (23) as a virtual image (V) formed on a side further away from the imaging device (100). As a result, the user (22) can see the rear view of the moving body (23) without significantly changing the viewing distance (viewing point) while driving the moving body (23), making it easier to see the virtual image (V), thereby improving driving safety. In addition, since the imaging device (100) is a compact imaging device, it does not occupy a large volume within the driver's cabin of the moving body (23) even when placed inside the driver's cabin, making it difficult to interfere with driving. An imaging device (100) mounted on a moving body (23) and configured to allow a user (22) to see the rear view of the moving body (23) as a virtual image (V) is also called a digital room mirror.

[0153] The imaging device (100) may have a display device (1, 1A, 1A', 1B) equipped with an optical element (9) (see FIG. 3). The imaging device (100) may be configured such that a display panel (2) displays a mixed image including a left-eye image and a right-eye image having a parallax with each other, emits a display light of the left-eye image and a 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 made visible to the user (22) as a stereoscopic virtual image (V).

[0154] As shown in FIG. 11, the imaging device (100) may be equipped with a reflective optical element (101). The imaging device (100) may be configured such that a display device (1, 1A, 1A', 1B) emits display light toward the reflective optical element (101), and the reflective optical element (101) causes a portion of the display light to reach the eyes of the user (22). When the imaging device (100) is mounted on a mobile body (23), the imaging device (100) may use the windshield (24) of the mobile body (23) as the reflective optical element (101).

[0155] The imaging device (100) may be applied to a digital side mirror. In this case, the imaging device (100) may be equipped with a display device (1, 1A, 1A', 1B) located on the left A-pillar of the moving body (23) as shown in FIG. 12 (hereinafter also referred to as the left display device (1L)), a camera (102) that captures the left rear of the moving body (23) (hereinafter also referred to as the left camera (102L)), a display device (1, 1A, 1A', 1B) located on the right A-pillar of the moving body (23) (hereinafter also referred to as the right display device (1R)), and a camera (102) that captures the right rear of the moving body (23) (hereinafter also referred to as the right camera (102R)). The left display device (1L) may display to the user (22) an image of the left rear of the moving object (23) captured by the left camera (102L) as a virtual image (V) (hereinafter also referred to as a virtual image (V2)). The right display device (1R) may display to the user (22) an image of the right rear of the moving object (23) captured by the right camera (102R) as a virtual image (V) (hereinafter also referred to as a virtual image (V3)). Also, the image may be a moving image (also referred to as a video) or a still image. The left camera (102L) may be located in the same position as the left door mirror, and the right camera (102R) may be located in the same position as the right door mirror.

[0156] The imaging device (100) may be configured such that the distance between the user's (22) eye (or eye box) and the virtual images (V2, V3) respectively roughly coincides with each other. In this case, the user (22) can check the situation on the left rear and right rear of the moving body (23) without significantly changing the viewing distance (the distance between the user's (22) eye and the viewing point the user (22) is looking at). Thus, driving safety can be improved. Also, the eye box refers to an area in actual space where the user's (22) eye is assumed to exist.

[0157] The imaging device (100) may be configured such that the distance between the user's (22) eye (or eye box) and the virtual images (V1 to V3) each roughly coincides with one another. In this case, the user (22) can check the situation immediately behind, to the left rear, and to the right rear of the moving object (23) without significantly changing the viewing distance. Thus, driving safety can be improved.

[0158] The image device (100) may be applied to a cluster (29) within the dashboard of a moving body (23) (see FIG. 12). In this case, the display device (1, 1A, 1A', 1B) may display an image showing driving information such as vehicle speed, engine rotation speed, and fuel level to the user (22) as a virtual image (V) (hereinafter also referred to as a virtual image (V4)).

[0159] The image device (100) may be applied to a Center Information Display (CID) (30) (see FIG. 12). In this case, the display device (1, 1A, 1A', 1B) is placed in the center cluster of the moving body (23), and an image showing information regarding navigation, the in-vehicle environment (e.g., settings of the air conditioning system, audio system, etc.) may be made visible to the user (22) as a virtual image (V) (hereinafter also referred to as a virtual image (V5)).

[0160] The imaging device (100) may be configured such that the distance between the user's (22) eye (or eye box) and the virtual images (V4, V5) respectively roughly coincides with each other. In this case, the user (22) can check information regarding the operation of the moving object (23), as well as information regarding navigation and the in-vehicle environment, without significantly changing the viewing distance. Therefore, driving safety can be improved.

[0161] The imaging device (100) may be configured such that the distance between the user's (22) eye (or eye box) and the virtual images (V1 to V5) is approximately the same. In this case, the user (22) can check the immediate rear, left rear, and right rear of the moving object (23) without significantly changing the viewing distance, and can also check information regarding the driving, navigation, and in-vehicle environment of the moving object (23). Therefore, driving safety can be improved.

[0162] The image device (100) may be applied to a Passenger Information Display (PID) (31) (see FIG. 12). In this case, the display device (1, 1A, 1A', 1B) may be placed near the passenger seat on the dashboard, and may display images of entertainment content and information regarding audio devices, air conditioning devices, etc., as virtual images (V) to the passenger.

[0163] The image device (100) may be applied to a Rear Seat Entertainment (RSE) system (32) (see FIG. 10). In this case, the display device (1, 1A, 1A', 1B) is placed on the back of the front seat and may display an image showing information regarding entertainment content, audio devices, air conditioning devices, etc., as a virtual image (V) to a passenger seated in the rear seat of the vehicle (23).

[0164] The display device (1, 1A, 1A', 1B) may be equipped with a driving unit that adjusts the relative position between the display panel (2), the semi-transparent mirror (6), the first semi-transparent mirror (11, 17), and the second semi-transparent mirror (13, 13', 21) in the depth direction. The image data of the display image displayed on the display panel (2) may include depth information indicating the depth (distance in the depth direction) from a reference position. The reference position may be, for example, the position of the display panel (2). The virtual image display device (100) may be configured to adjust the distance between the display panel (2), the semi-transparent mirror (6), the first semi-transparent mirror (11, 17), and the second semi-transparent mirror (13, 13', 21) based on the depth information included in the image data, and to change the image formation position of the virtual image (V) in the depth direction. The driving unit may be composed of, for example, an electric slider, an electric cylinder, etc. The driving unit may be configured so that the user (22) can manually adjust the relative positions between the display panel (2), the semi-transparent mirror (6), the first semi-transparent mirror (11, 17) and the second semi-transparent mirror (13, 13', 21).

[0165] Hereinafter, another example of the display device of the present disclosure will be described.

[0166] First, another example of a display device (1, 1A, 1A', 1B) will be described. FIGS. 13 and 14 are top views showing another example of a display device of the present disclosure. Also, in FIGS. 13 and 14, the first phase difference plate (5), the second phase difference plate (7), and the optical element (9) are omitted. Below, the display device (1) will be described as an example, but the same applies to the display devices (1A, 1A', 1B).

[0167] The display device (1) may constitute part of the image forming device (100) (digital room mirror). In a conventional room mirror, that is, a room mirror using a mirror, the image seen by the user's left eye (also called the left eye mirror image) and the image seen by the right eye (also called the right eye mirror image) are different, and the user perceives the left eye mirror image and the right eye mirror image as mirror images seen by both eyes through the cognitive function of the brain.

[0168] The display device (1) may be configured such that the virtual image projected within the field of view of the user (22) has a binocular visible area (virtual image (V) in FIG. 13 and 14) visible to both eyes (22L) and right eye (22R) of the user (22), a left eye visible area (VLa) visible only to the left eye (22L), and a right eye visible area (VRa) visible only to the right eye (22R). In other words, when the virtual image visible to the left eye (22L) is called the left eye virtual image (VL) and the virtual image visible to the right eye (22R) is called the right eye virtual image (VR), the left eye virtual image (VL) may have a left eye visible area (VLa) visible only to the left eye (22L), and the right eye virtual image (VR) may have a right eye visible area (VRa) visible only to the right eye (22R). In the field of view of the user (22), the left eye visible area (VLa) is located to the right of the binocular visible area, and the right eye visible area (VRa) is located to the left of the binocular visible area. Additionally, as shown in FIG. 13, the display device (1) may be configured such that the right end (6R) visible to the user (22) in the semi-transparent mirror (6) is located on a straight line connecting the left eye (22L) and the right end (VLR) of the left eye virtual image (VL), and the left end (6L) visible to the user (22) in the semi-transparent mirror (6) is located on a straight line connecting the right eye (22R) and the left end (VRL) of the right eye virtual image (VR).

[0169] According to this configuration, just like the left eye mirror and right eye mirror in a standard rearview mirror, the range that the user (22) observes through the left eye virtual image (VL) and the range that the user (22) observes through the right eye virtual image (VR) are different. Therefore, just as when using a standard rearview mirror, the user (22) can perceive the left eye virtual image (VL) and the right eye virtual image (VR) as virtual images (V) that both eyes (22L, 22R) see through the cognitive function of the brain. Thus, the risk of causing a sense of unease to the user (22) can be reduced.

[0170] In the display device (1), the size of the reflective surface on the display surface (2a) side of the reflective polarizer (8) may be greater than or equal to the size of the display surface (2a). In this case, the reflective polarizer (8) may reflect the entire image of the display surface (2a) toward the semi-transparent mirror (6). Additionally, the display device (1) may be configured such that the virtual image (hereinafter also referred to as the display surface virtual image) (VD) when the entire image of the display surface (2a) is projected into the field of view of the user (22) includes a left eye virtual image (VL) and a right eye virtual image (VR). In this case, when the head part of the user (22) moves, an area (R) that appears in the field of view of the left eye (22L) and the right eye (22R) can be formed, that is, a peeping area (R) that can be peeked at with the left eye (22L) or the right eye (22R). As a result, the user (22) can see the left eye virtual image (VL) and the right eye virtual image (VR) that change according to the movement of the head part, just as when using a normal rearview mirror. Therefore, the risk of causing discomfort to the user (22) can be reduced. The size (dimensions) of the peeping area (R) can be controlled by controlling, for example, the size of the display surface (2a) and the magnification ratio of the virtual image.

[0171] It is also possible to control the size of the peeping area (R) by controlling the image display area (the area where the image is actually displayed) (A) on the display surface (2a). If the image display area (A) is made larger, the peeping area (R) can be expanded. If the image display area (A) is made smaller, the peeping area (R) can be reduced. If the image display area (A) becomes smaller than a predetermined threshold area, the peeping area (R) disappears, and the left eye virtual image (VL) and the right eye virtual image (VR) can be made into the same virtual image.

[0172] 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). It is also possible to control the size of the peeping area (R) 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 an area that the right eye (22R) cannot see, and a right-eye virtual image (VR) including an area that the left eye (22L) cannot see can be formed. In addition, by appropriately designing the size of the opening (28), a peeping area (R) can be formed, and the size of the peeping area (R) can be controlled. When the size of the peeping area (R) is controlled by the opening (28), the size of the semi-transparent mirror (6) can be such that the image of the entire display surface (2a) is projected into the user's (22) field of view, thus making the design of the optical system (3) easier.

[0173] The same applies to the display device (1A, 1A', 1B). The display device (1A, 1A', 1B) may be configured such that the virtual image projected within the field of view of the user (22) has a bilateral visible area visible to both the left eye (22L) and the right eye (22R), a left-eye visible area visible only to the left eye (22L), and a right-eye visible area visible only to the right eye (22R). In this case, the risk of causing a sense of unease to the user (22) can be reduced. The display device (1A, 1A') may be configured such that the right end visible to the user (22) in the first semi-transparent mirror (11) is located on a straight line connecting the left eye (22L) and the right end of the left-eye virtual image, and the left end visible to the user (22) in the first semi-transparent mirror (11) is located on a 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-transparent mirror (17) and the third semi-transparent mirror (21) is located on a straight line connecting the left eye (22L) and the right end of the virtual image of the left eye, and the left end visible to the user (22) in the first semi-transparent mirror (17) and the third semi-transparent mirror (21) is located on a straight line connecting the right eye (22R) and the left end of the virtual image of the right eye. The display device (1A, 1A', 1B) may be configured to have a peeping area (R). The display device (1A, 1A', 1B) may be configured such that the size of the peeping area (R) is controlled by the image display area (A), or the size of the peeping area (R) is controlled by the opening (28) of the housing (27).

[0174] Next, other examples of display devices (1, 1A, 1A') will be described. FIGS. 15 and 16 are cross-sectional views describing other examples of display devices, FIGS. 17a to 17d and 18a to 18d are drawings describing optical systems in other examples of display devices, and FIG. 19 is a graph describing optical systems in other examples of display devices. Below, display device (1) will be described as an example, but the same applies to display devices (1A, 1A').

[0175] The display device (1) is configured so that when a user (22) is positioned in front of the display device (1), light of the second linear polarization (L2) is reflected by the reflective polarizer (8) and does not exit from the display device (1) (see FIGS. 2 and 3). In other words, the display device (1) is configured so that when viewed from the front of the display device (1), the transmission axis of the polarizer on the front side (user (22) side) of the display panel (2) (liquid crystal panel) and the transmission axis of the reflective polarizer (8) are orthogonal (in a cross-Nicole arrangement). As a result, as shown in FIGS. 2 and 3, light of the second linear polarization (L2) is not exited from the display device (1), and light of the fourth linear polarization (L4) is exited from the display device (1). In other words, the user (22) does not directly see the display panel (2), but sees the reflected image reflected by the semi-transparent mirror (6) as a virtual image (V).

[0176] When the user (22) is not positioned in front of the display device (1), the cross-Nicole arrangement of the transmission axis of the front polarizer of the display panel (2) and the transmission axis of the reflection polarizer (8) is disrupted, and some of the light of the second linear polarization (L2) passes through the reflection polarizer (8). As a result, the user (22) can see both the real image of the display panel (2) and the virtual image (V) reflected by the semi-transparent mirror (6), and the display quality of the display device (1) may be degraded.

[0177] As shown in FIGS. 15 and 16, the display device (1) of the present example has a third phase difference plate (25) located between the display panel (2) and the reflective polarizer (8). By doing so, even when the user (22) is not located in front of the display device (1), the relative angle between the transmission axis of the polarizer in front of the display panel (2) and the transmission axis of the reflective polarizer (8) can be made close to a cross-Nicole arrangement, and the deterioration of the display quality of the display device (1) can be reduced. The third phase difference 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 any other wavelength plate that imparts a phase difference. The optical axis of the third phase difference plate (25) may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer (8).

[0178] As shown in FIGS. 15 and 16, the display device (1) of the present example may further have a fourth phase difference plate (26) located between the display panel (2) and the reflective polarizer (8). In this case, even if the user (22) is not located in front of the display device (1), the relative angle between the transmission axis of the polarizer in front of the display panel (2) and the transmission axis of the reflective polarizer (8) can be brought closer by cross-Nicole arrangement, and the deterioration of the display quality of the display device (1) can be further reduced. The fourth phase difference 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 any other wavelength plate that imparts a phase difference. The optical axis of the fourth phase difference plate (26) may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer (8).

[0179] The third phase difference plate (25) and the fourth phase difference plate (26) may be positioned between the display panel (2) and the reflective polarizer (8), and their positions are arbitrary. If no other optical element is positioned between the third phase difference plate (25) and the fourth phase difference plate (26), the third phase difference plate (25) and the fourth phase difference plate (26) may be in contact with each other. In this case, the thickness in the depth direction of the optical system (3) can be reduced.

[0180] One of the third phase difference plate (25) and the fourth phase difference plate (26) may be a quarter-wave plate and the other half-wave plate. In this case, the deterioration of the display quality of the display device (1) can be effectively reduced. Both of the third phase difference plate (25) and the fourth phase difference plate (26) may be half-wave plates. In this case, the deterioration of the display quality of the display device (1) can be reduced more effectively.

[0181] FIGS. 17a, 17b, 17c, and 17d are Poincaré spheres showing the optical functions (influence on the polarization state of light) of the third phase difference plate (25) and the fourth phase difference plate (26) when the third phase difference plate (25) and the fourth phase difference plate (26) are half-wave plates. FIGS. 17a and 17b are drawings explaining the optical functions of the third phase difference plate (25), and FIGS. 17c and 17d are drawings explaining the optical functions of the fourth phase difference plate (26). FIGS. 17a and 17c show the Poincaré sphere viewed from the North Pole (S3 axis direction), and FIGS. 17b and 17d show the Poincaré sphere viewed from the side (S1 axis direction). In FIGS. 17a, 17b, 17c, and 17d, S LCD represents the polarization state of light immediately after the display panel (2) is emitted. S 25 represents the polarization state of the light that has passed through the third phase difference plate (25), and S 26 represents the polarization state of the light that has passed through the fourth phase difference plate (26). S 26It can be said that it represents the polarization state of light immediately before it is incident on the reflective polarizer (8). S RP represents the polarization state of light that transmits the reflective polarizer (8) with substantially 100% transmittance, and S AP is S RP It is the antipodal point (the point symmetric with respect to the center of the Poincaré sphere). S 26 This S AP Located at or S AP When located in the vicinity of, the display panel (2) is emitted, thereby reducing the risk that light passing through the third phase difference plate (25) and the fourth phase difference plate (26) will pass through the reflective polarizer (8). As a result, the risk of the user (22) seeing the actual image of the display panel (2) directly can be reduced, and the deterioration of the display quality of the display device (1) can be reduced.

[0182] As shown in FIG. 17c and 17d, when the third phase difference plate (25) and the fourth phase difference plate (26) are half-wave plates, S 26 is practically S AP It is located at. Therefore, the risk of the user (22) seeing the actual state of the display panel (2) can be reduced, and the deterioration of the display quality of the display device (1) can be reduced.

[0183] FIGS. 18a, 18b, 18c, and 18d are Poincaré spheres showing the optical functions of the third phase difference plate (25) and the fourth phase difference plate (26) when the third phase difference plate (25) is a quarter-wave plate and the fourth phase difference plate (26) is a half-wave plate. FIGS. 18a and 18b are drawings explaining the optical function of the third phase difference plate (25), and FIGS. 18c and 18d are drawings explaining the optical function of the fourth phase difference plate (26). FIGS. 18a and 18c show the Poincaré sphere viewed from the North Pole (S3 axis direction), and FIGS. 18b and 18d show the Poincaré sphere viewed from the side (S1 axis direction). S LCD , S 25 , S26 , S RP and S AP It is as described above.

[0184] As shown in FIG. 18c and 18d, when the third phase difference plate (25) is a quarter-wave plate and the fourth phase difference plate (26) is a half-wave plate, S 26 Eun S AP It is located in the vicinity of. Therefore, the risk of the user (22) seeing the actual state of the display panel (2) can be reduced, and the deterioration of the display quality of the display device (1) can be reduced.

[0185] FIG. 19 is a graph showing the relationship between the light transmittance of an optical system formed by inserting a third phase difference plate (25) and a fourth phase difference plate (26) between polarizers (PP1, PP2) whose transmission axes are orthogonal to each other, and the phase difference between the third phase difference plate (25) and the fourth phase difference plate (26). FIG. 19 shows the results obtained by simulation. The incident light was green light with a wavelength (λ) of 550 nm. The polarizer (PP1), the third phase difference plate (25), the fourth phase difference plate (26), and the polarizer (PP2) are arranged in this order in the direction of propagation of the incident light. The polarizer (PP1) is modeled after the polarizer on the front side of the display panel (2), and the polarizer (PP2) is modeled after the reflective polarizer (8).

[0186] The solid line in the graph of FIG. 19 represents the transmittance when the phase difference of the fourth phase difference plate (26) is fixed at 0 nm and the phase difference of the third phase difference plate (25) is varied, and it is minimized when the phase difference of the third phase difference plate (25) is about 275 nm (half the wavelength (λ) of the incident light). The dashed line in the graph of FIG. 19 represents the transmittance when the phase difference of the third phase difference plate (25) is fixed at 270 nm and the phase difference of the fourth phase difference plate (26) is varied, and it is minimized when the phase difference of the fourth phase difference plate (26) is about 275 nm (half the wavelength of the incident light).

[0187] From the simulation results shown in the graph of FIG. 19, it can be seen that when the third phase difference plate (25) and the fourth phase difference plate (26) are half-wave plates, the display device (1) can effectively reduce the risk of the user (22) seeing the actual image directly facing the display panel (2) and effectively reduce the deterioration of the display quality of the display device (1). In addition, it can be seen that even when the phase difference of the fourth phase difference plate (26) is fixed at 0 nm (i.e., when only the third phase difference plate (25) is present), if the third phase difference plate (25) can impart a phase difference greater than 0 nm (i.e., non-zero) to the light incident on the third phase difference plate (25), the risk of the user (22) seeing the actual image directly facing the display panel (2) can be effectively reduced and the deterioration of the display quality of the display device (1) can be effectively reduced.

[0188] The same applies to the display device (1A, 1A'). The display device (1A, 1A') may have a third phase difference plate (25) located between the display panel (2) and the polarizing plate (15). In this case, the risk of the user (22) seeing the actual image directly facing the display panel (2) can be reduced, and the deterioration of the display quality of the display device (1A, 1A') can be reduced. The display device (1A, 1A') may further have a fourth phase difference plate (26) located between the display panel (2) and the polarizing plate (15). In this case, the risk of the user (22) seeing the actual image directly facing the display panel (2) can be further reduced, and the deterioration of the display quality of the display device (1A, 1A') can be further reduced. The third phase difference plate (25) and the fourth phase difference plate (26) may be a 1 / 2 wavelength plate (half wavelength plate), a 1 / 4 wavelength plate, a 1 / 8 wavelength plate, a 1 / 16 wavelength plate, etc., or any other wavelength plate that imparts a phase difference. One of the third phase difference plate (25) and the fourth phase difference plate (26) may be a 1 / 4 wavelength plate and the other may be a half wavelength plate. In this case, the deterioration of the display quality of the display device (1) can be effectively reduced. Both of the third phase difference plate (25) and the fourth phase difference plate (26) may be half wavelength plates. In this case, the deterioration of the display quality of the display device (1) can be reduced even more effectively. The third phase difference plate (25) and the fourth phase difference plate (26) may be located between the display panel (2) and the polarizing plate (15), and their positions are arbitrary.

[0189] Next, other examples of display devices (1, 1A, 1A', 1B) are described. FIG. 20 is a cross-sectional view showing another example of a display device (1A'), and FIG. 21 is a cross-sectional view showing another example of a display device (1A).

[0190] The second semi-transparent 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-transparent mirror (13') can be realized by a flat-plate optical element, and the thickness of the second semi-transparent mirror (13') in the depth direction (Z-axis direction) can be reduced. As a result, the display device (1A') can be made smaller in the depth direction. In addition, since the second semi-transparent mirror (13') is a flat-plate optical element, the distance between the second semi-transparent mirror (13') and the second phase difference plate (14) can be reduced, or the second semi-transparent mirror (13') and the second phase difference plate (14) can be brought into contact with each other, making it possible to make the display device (1A') even smaller in the depth direction.

[0191] The first semi-transparent mirror (11) of the display device (1A') may be configured to include a HOE. In this case, as shown in FIG. 20, the optical function of the first semi-transparent mirror (11) can be realized by a flat-panel optical element, and the thickness of the first semi-transparent mirror (11) in the depth direction can be reduced. As a result, the display device (1A') can be made smaller in the depth direction. In addition, since the first semi-transparent mirror (11) is a flat-panel optical element, the distance between the first semi-transparent mirror (11) and the display panel (2) can be reduced, or the first semi-transparent mirror (11) and the display panel (2) can be brought into contact with each other, making it possible to make the display device (1A') even smaller in the depth direction.

[0192] If the first semi-transparent mirror (11) does not have polarization selectivity, the amount of light emitted from the display device (1A') decreases, and the brightness of the virtual image (V) seen by the user (22) decreases. Therefore, the first semi-transparent mirror (11) including the HOE may be configured to have polarization selectivity. For example, the first semi-transparent mirror (11) including the HOE may have a plurality of metal wires (metal nanowire grid) formed on the surface facing the display panel (2) or the surface facing the first phase difference plate (12) to realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the decrease in brightness of the virtual image (V) seen by the user (22) can be reduced.

[0193] The first semi-transparent 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 semi-transparent mirror (11) can be realized by a flat-panel optical element, and the thickness of the first semi-transparent mirror (11) in the depth direction can be reduced. As a result, the display device (1A) can be miniaturized in the depth direction. In addition, since the first semi-transparent mirror (11) is a flat-panel optical element, the distance between the first semi-transparent mirror (11) and the display panel (2) can be reduced, or the first semi-transparent mirror (11) and the display panel (2) can be brought into contact with each other, making it possible to further miniaturize the display device (1A) in the depth direction. The first semi-transparent mirror (11) including the HOE may have polarization selectivity. For example, the first semi-transparent mirror (11) including the HOE may have a plurality of metal wires formed on the surface facing the display panel (2) or the surface facing the first phase difference plate (12) to realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the decrease in brightness of the virtual image (V) seen by the user (22) can be reduced.

[0194] The semi-transparent mirror (6) of the display device (1) may be configured to include a HOE. In this case, the optical function of the semi-transparent mirror (6) can be realized by a flat-panel optical element, and the thickness of the semi-transparent mirror (6) in the depth direction can be reduced. As a result, the display device (1) can be made smaller in the depth direction. In addition, since the semi-transparent mirror (6) is a flat-panel optical element, the distance between the semi-transparent mirror (6) and the first phase difference plate (5) can be reduced, or the semi-transparent mirror (6) and the first phase difference plate (5) can be brought into contact with each other, making it possible to make the display device (1) even smaller in the depth direction.

[0195] The first semi-transparent mirror (17) of the display device (1B) may be configured to include a HOE. In this case, the optical function of the first semi-transparent mirror (17) can be realized by a flat-panel optical element, and the thickness of the first semi-transparent mirror (17) in the depth direction can be reduced. As a result, the display device (1B) can be made smaller in the depth direction. In addition, since the first semi-transparent mirror (17) is a flat-panel optical element, the distance between the first semi-transparent mirror (17) and the display panel (2) can be reduced, or the first semi-transparent mirror (17) and the display panel (2) can be brought into contact with each other, making it possible to make the display device (1B) even smaller in the depth direction. The first semi-transparent mirror (17) including the HOE may have polarization selectivity. For example, the first semi-transparent mirror (17) including the HOE may have a plurality of metal wires formed on the surface facing the display panel (2) or the surface facing the first phase difference plate (18) to realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the decrease in brightness of the virtual image (V) seen by the user (22) can be reduced.

[0196] The third semi-transparent mirror (21) of the display device (1B) may be configured to include a HOE. In this case, the optical function of the third semi-transparent mirror (21) can be realized by a flat optical element, and the thickness of the third semi-transparent mirror (21) in the depth direction can be reduced. As a result, it becomes possible to miniaturize the display device (1B) in the depth direction. The third semi-transparent mirror (21) including the HOE may have polarization selectivity. For example, the third semi-transparent mirror (21) including the HOE may have a plurality of metal wires formed on the surface facing the second phase difference plate (20) or on the surface opposite to the surface facing the second phase difference plate (20) to realize polarization selectivity that reflects S-wave polarized light and transmits P-wave polarized light. In this case, the deterioration of the quality of the virtual image (V) recognized by the user (22) can be reduced, and the deterioration of the brightness of the virtual image (V) can also be reduced.

[0197] A holographic optical element may have, for example, an interference pattern and be configured to diffract incident light in a predetermined direction.

[0198] The display device (1A') may be configured such that the second semi-transparent mirror (13') includes a Fresnel lens. In this case, as shown in FIG. 22, the optical function of the second semi-transparent mirror (13') can be realized by an optical element with a roughly flat shape that has a reduced thickness (dimension in the depth direction) compared to a convex half mirror, and the thickness of the second semi-transparent mirror (13') in the depth direction can be reduced. As a result, the display device (1A') can be made smaller in the depth direction. In addition, since the second semi-transparent mirror (13') is in a roughly flat shape, the distance between the second semi-transparent mirror (13') and the second phase difference plate (14) can be reduced, or the second semi-transparent mirror (13') and the second phase difference plate (14) can be brought into contact with each other, making it possible to make the display device (1A') even smaller in the depth direction. The second semi-transparent mirror (13') containing a Fresnel lens is also called a Fresnel half mirror (13').

[0199] As shown in FIG. 23, the Fresnel half mirror (13') may be configured to include a Fresnel lens (Fresnel convex lens) (33) having a first plane (33a) facing the second phase difference plate (14) and a second Fresnel-shaped plane (33b) facing the first phase difference plate (12), and a semi-transparent reflective layer (34) located on the second plane (33b). The Fresnel shape has concentric grooves centered on a reference point (33c). The grooves include a plane approximately perpendicular to the first plane (33a) and an inclined plane inclined with respect to the first plane (33a). The inclined plane may be a curved plane or a flat plane. The semi-transparent reflective layer (34) may be located on the Fresnel-shaped inclined plane. The semi-transparent reflective layer (34) may transmit a portion (e.g., approximately 50%) of the incident light and reflect the remainder (e.g., approximately 50%). The semi-transparent reflective layer (34) may be a metal thin film. The metal thin film may be composed of a metal material such as aluminum or chromium. The metal thin film may be formed by a deposition method such as the CVD (Chemical Vapor Deposition) method or the PVD (Physical Vapor Deposition) method.

[0200] 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 (e.g., focal length, etc.) is determined by the curvature and angle of inclination of the inclined surface, the refractive index of the material constituting the Fresnel lens (33), etc. The optical function as a half mirror (e.g., focal length, transmittance, etc.) is determined by the curvature and angle of inclination of the inclined surface, the transmittance of the semi-transparent reflective layer (34), etc.

[0201] The Fresnel half mirror (13') may have a surface facing the second phase difference plate (14) flattened by a transparent material layer formed on the second surface (33b) of the Fresnel lens (33). The transparent material layer may be composed of a material having approximately 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).

[0202] The display device (1A') may be configured such that the first semi-transparent mirror (11) includes a Fresnel lens. In this case, as shown in FIG. 22, the thickness of the first semi-transparent mirror (11) can be reduced, and as a result, the display device (1A') can be made smaller in the depth direction. Additionally, since the first semi-transparent mirror (11) including the Fresnel lens is approximately flat in shape, the distance between the first semi-transparent mirror (11) and the display panel (2) can be reduced, or the first semi-transparent mirror (11) and the display panel (2) can be brought into contact with each other, making it possible to make the display device (1A') even smaller in the depth direction. The first semi-transparent mirror (11) including the Fresnel lens is also 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.

[0203] When the first semi-transparent mirror (11) is replaced with a Fresnel half mirror (11) that does not have polarization selectivity, the amount of light emitted from the display device (1A') is reduced, and the brightness of the virtual image (V) seen by the user (22) is reduced. 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 wires (metal nanowire grid) formed on the surface facing the display panel (2) or the surface facing the first phase difference plate (12) to realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. By doing so, the reduction in brightness of the virtual image (V) seen by the user (22) can be reduced.

[0204] The first semi-transparent mirror (11) of the display device (1A) may be configured to include a Fresnel lens, as shown in FIG. 23. In this case, the thickness of the first semi-transparent mirror (11) can be reduced, and as a result, the display device (1A) can be made smaller in the depth direction. In addition, since the first semi-transparent mirror (11) including the Fresnel lens is approximately flat in shape, the distance between the first semi-transparent mirror (11) and the display panel (2) can be reduced, or the first semi-transparent mirror (11) and the display panel (2) can be brought into contact with each other, making it possible to make the display device (1A) even smaller in the depth direction. The first semi-transparent mirror (11) including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transparent mirror (11) including a Fresnel lens may have a plurality of metal wires formed on the surface facing the display panel (2) or the surface facing the first phase difference plate (12) to realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the decrease in brightness of the virtual image (V) seen by the user (22) can be reduced.

[0205] The semi-transparent mirror (6) of the display device (1) may be configured to include a Fresnel lens. In this case, the thickness of the semi-transparent mirror (6) can be reduced, and as a result, the display device (1) can be made smaller in the depth direction. In addition, since the semi-transparent mirror (6) including the Fresnel lens is approximately flat in shape, the distance between the semi-transparent mirror (6) and the first phase difference plate (5) can be reduced, or the semi-transparent mirror (6) and the first phase difference plate (5) can be brought into contact with each other, making it possible to make the display device (1) even smaller in the depth direction.

[0206] The first semi-transparent mirror (17) of the display device (1B) may be configured to include a Fresnel lens. In this case, the thickness of the first semi-transparent mirror (17) can be reduced, and as a result, the display device (1B) can be made smaller in the depth direction. Additionally, since the first semi-transparent mirror (17) including the Fresnel lens is approximately flat in shape, the distance between the first semi-transparent mirror (17) and the display panel (2) can be reduced, or the first semi-transparent mirror (17) and the display panel (2) can be brought into contact with each other, making it possible to make the display device (1B) even smaller in the depth direction. The first semi-transparent mirror (17) including the Fresnel lens may be configured to have polarization selectivity. For example, the first semi-transparent mirror (17), which includes a Fresnel lens, may have a plurality of metal wires formed on the surface facing the display panel (2) or the surface facing the first phase difference plate (18) to realize polarization selectivity that transmits S-wave polarized light and reflects P-wave polarized light. In this case, the decrease in brightness of the virtual image (V) seen by the user (22) can be reduced.

[0207] The third semi-transparent mirror (21) of the display device (1B) may be configured to include a Fresnel lens. In this case, the thickness of the third semi-transparent mirror (21) can be reduced, and as a result, the display device (1B) can be miniaturized in the depth direction. The third semi-transparent mirror (21) including the Fresnel lens may be configured to have polarization selectivity. For example, the third semi-transparent mirror (21) including the Fresnel lens may have a plurality of metal wires formed on the surface facing the second phase difference plate (20) or on the surface opposite to the surface facing the second phase difference plate (20) to realize polarization selectivity that reflects S-wave polarized light and transmits P-wave polarized light. In this case, the deterioration of the quality of the virtual image (V) seen by the user (22) can be reduced, and the deterioration of the brightness of the virtual image (V) can also be reduced.

[0208] Hereinafter, control of the viewing area in the imaging device (100) (display device (1, 1A, 1A', 1B)) will be described. In the following description, the imaging device (100) is assumed to be a digital rearview mirror (see FIG. 10). The imaging device (100) is equipped with an angle sensor that detects the direction of the display device (1, 1A, 1A', 1B) in a predetermined direction fixed to the moving body (23). The predetermined direction may be, for example, the direction of the vehicle length of the moving body (23), but is not limited thereto. The angle sensor may be a 3-axis angle sensor capable of detecting the direction (roll, pitch, yaw) of the display device (1, 1A, 1A', 1B). The moving body (23) is equipped with a Driver Monitoring System (DMS), and the imaging device (100) is capable of communicating with the DMS and controlling the DMS. The DMS is of the moving body (23). It is possible to capture the face of a user (22) sitting in the driver's seat and perform face authentication of the user (22), and also determine whether the user (22) is a known user. A known user may refer to a user whose information (also called user information) such as features used for face authentication, eye position while driving, and face direction is stored in the memory of the controller (43) and / or the memory of the DMS.

[0209] When the user (22) is positioned in front of the display device (1, 1A, 1A', 1B), the size of the left peeping area (PL) and the size of the right peeping area (PR) are roughly the same (see FIG. 25), so the user (22) can see the virtual image (V) that changes with the movement of the head unit, just as when using a normal rearview mirror. When the user (22) is not positioned in front of the display device (1, 1A, 1A', 1B), the size of the left peeping area (PL) and the size of the right peeping area (PR) are not the same (see FIG. 26), so the user (22) cannot see the virtual image (V) that changes with the movement of the head unit, just as when using a normal rearview mirror, and there is a risk of feeling a sense of unease.

[0210] With reference to the flowchart shown in FIG. 29, the control of the image-detection device (100) by the controller (43) will be explained. In the flowchart, the "step" is abbreviated as "S", and within the chart, "Yes" (computer flag=1) in the judgment control is indicated as [Yes], and "No" (computer flag=0 zero) is indicated as [No].

[0211] The flowchart of FIG. 29 begins, for example, when a user (22) sits in the driver's seat of a moving body (23) and starts the engine of the moving body (23).

[0212] [S1] In this case, the DMS is controlled to verify the user (22) who is sitting in the driver's seat of the moving body (23).

[0213] In [S2], the DMS is controlled to perform facial authentication of the user (22) seated in the driver's seat and to 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].

[0214] [S3] In this case, user information of the user (22) (information such as the position of the eyes and the direction of the face while driving) is obtained from the DMS.

[0215] In [S4], adjustment of the display device (1, 1A, 1A', 1B) is performed based on user information obtained in [S3]. The adjustment of the display device (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 direction of the display device (1, 1A, 1A', 1B), the position of the user's (22) eyes, the direction of the face, etc. The change of the display area may be made by making a part of the display surface (2a) into a non-display area (2b) that does not display an image, as shown in FIG. 27. As shown in FIG. 27, by changing the display area of ​​the display image on the display surface (2a), the size of the left peeking area (PL) and the size of the right peeking area (PR) can be roughly matched even when the user (22) is not positioned in front of the display device (1, 1A, 1A', 1B), and as a result, the risk of the user (22) feeling uncomfortable can be reduced.

[0216] Adjustment of the display device (1, 1A, 1A', 1B) may include sliding (translating in parallel) at least one of the reflective polarizer (8), the semi-transparent mirror (6), and the display panel (2) in a direction perpendicular to the direction of the emission of display light from the display panel (2), depending on the direction of the display device (1, 1A, 1A', 1B), the position of the user's (22) eyes, the direction of the face, etc. By sliding at least one of the reflective polarizer (8), the semi-transparent mirror (6), and the display panel (2), the size of the left peeping area (PL) and the size of the right peeping area (PR) can be roughly matched as shown in FIG. 28, and as a result, the risk of the user (22) feeling uncomfortable can be reduced. In addition, when at least one of the reflective polarizer (8), the semi-transparent mirror (6), and the display panel (2) is slid, the size of the left peeking area (PL) and the right peeking area (PR) can be reduced compared to when the user (22) is positioned in front of the display device (1, 1A, 1A', 1B).

[0217] In [S5], the controller (43) receives instructions from the user (22) regarding whether readjustment of the display device (1, 1A, 1A', 1B) is required. The image capture device (100) may be configured so that the user (22) can indicate that readjustment is required by operating a button installed on the steering wheel, etc. The image capture device (100) may also be configured so that the user (22) can indicate that readjustment is required by shaking the image capture device (100) and changing the direction of the image capture device (100). The change in the direction of the image capture device (100) may be detected by the 3-axis angle sensor of the image capture device (100). In addition, if the controller (43) does not receive instructions from the user (22) within a predetermined time after starting to receive instructions from the user (22), it may determine that readjustment is not required. The predetermined time may be, for example, about 3 to 10 seconds, but is not limited to this.

[0218] In [S5], if [Yes] it is necessary to readjust the display device (1, 1A, 1A', 1B), proceed to [S6]. In [S5], if [No] it is not necessary to readjust the display device (1, 1A, 1A', 1B), terminate this flowchart. Also, in [S5], if [Yes] it is necessary to readjust the display device (1, 1A, 1A', 1B), proceed to [S7].

[0219] [S6] In this case, the controller (43) controls the DMS to detect user information of the user (22) (information such as the position of the eyes and the direction of the face while driving), and also obtains user information of the user (22) from the DMS.

[0220] In [S7], adjustment of the display device (1, 1A, 1A', 1B) is performed based on user information obtained in [S6]. The adjustment of the display device (1, 1A, 1A', 1B) may be the same as the adjustment of the display device (1, 1A, 1A', 1B) in [S4].

[0221] In [S8], the user (22) receives instructions regarding whether readjustment of the display device (1, 1A, 1A', 1B) is required. The reception of the user's (22) instructions may be the same as in [S5]. In [S8], if [Yes] indicates that readjustment of the display device (1, 1A, 1A', 1B) is required, return to [S6]. In [S8], if [No] indicates that readjustment of the display device (1, 1A, 1A', 1B) is not required, proceed to [S9]. Also, in [S8], if [Yes] indicates that readjustment of the display device (1, 1A, 1A', 1B) is required, return to [S7].

[0222] [S9] In this case, the controller (43) stores user information of the user (22) and information regarding the adjustment of the display device (1, 1A, 1A', 1B) in the memory of the controller (43) and / or the memory of the DMS, and terminates the flowchart.

[0223] According to the flowchart of FIG. 29, the peeping area in the digital rearview mirror can be efficiently controlled, and the risk of the user (22) feeling uncomfortable can be reduced. In addition, the flowchart of FIG. 29 can also be applied when the imaging device (100) is configured as a digital side mirror.

[0224] Another example of a display device (1, 1A, 1A', 1B) is described. The same reference numerals are attached to components identical to those of the display device (1, 1A, 1A', 1B), and detailed descriptions are omitted. The display device (1C) of this example comprises a display panel (2), an optical system (35), and a housing (36), as shown in FIG. 33.

[0225] 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 field of view of the user (22). The optical system (35) may be an optical system (3) (see FIGS. 2, 3, 30), an optical system (10) (see FIGS. 4, 5, 31), or an 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.

[0226] The housing (36) accommodates the display panel (2) and the optical system (35). The housing (36) may hold the display panel (2) and the optical system (35). If the display device (1C) includes an irradiator (4), the housing (36) may accommodate the irradiator (4) and hold the irradiator (4). The housing (36) has a window (opening) (37) that transmits light emitted from the optical system (35). The display device (1C) may be arranged so that the window (37) and the display panel (2) overlap when viewed through the window (37) of the housing (36). Additionally, the display device (1C) may be arranged so that the window (37) and the optical system (35) overlap when viewed through the window (37) of the housing (36). Additionally, the display device (1C) may be arranged such that the display panel (2) and the optical system (35) overlap when viewed through the window (37) of the housing (36). In this case, the occupied space of the display device (1C) can be reduced, and as a result, the display device (1C) can be miniaturized. Furthermore, in the display device (1C), the display light emitted from the display panel (2) propagates substantially along a single axis and forms an image as a virtual image (V). Because of this, the distortion and brightness deviation of the virtual image (V) seen by the user (22) can be reduced, and the design of the optical system (35) becomes easier.

[0227] As shown in FIGS. 33 and 34, the housing (36) may have a light-transmitting plate (38) placed in the window (37). The light-transmitting plate (38) may transmit light emitted from the optical system (35). The light-transmitting plate (38) blocks the window (37) at least partially. The light-transmitting plate (38) may be composed of, for example, glass, resin, etc.

[0228] The optical system (35) (optical system (3)) may have a third phase difference plate (25) and a fourth phase difference plate (26). The third phase difference plate (25) may be located on a surface facing the semi-transparent mirror (6) of the second phase difference plate (7). The fourth phase difference plate (26) may be located on a surface facing the semi-transparent mirror (6) of the third phase difference plate (25). By doing so, even when the user (22) is not located in front of the display device (1C), the relative angle between the transmission axis of the front polarizer of the display panel (2) and the transmission axis of the reflection polarizer (8) can be made close to a cross-Nicole arrangement, and the deterioration of the display quality of the display device (1C) can be reduced. The third phase difference plate (25) and the fourth phase difference plate (26) may be half-wave plates (half-wave plates), but are not limited to this. The third phase difference plate (25) and the fourth phase difference plate (26) may be a quarter-wave plate, a quarter-wave plate, a quarter-wave plate, etc., or any other wave plate that imparts a phase difference. The third phase difference plate (25) and the fourth phase difference plate (26) may be wave plates that impart the same phase difference or wave plates that impart different phase differences. The optical axis of the third phase difference plate (25) may be approximately parallel or approximately perpendicular to the transmission axis of the reflective polarizer (8).

[0229] The optical system (35) (optical system (3)) may have a moth-eye structure film (39) located on the surface facing the semi-transparent mirror (6) of the first phase difference plate (5). The moth-eye structure film (39) can attenuate the reflected light of light incident from the semi-transparent mirror (6) side. By doing so, the amount of unwanted light and disturbance light that is reflected by the first phase difference plate (5) and then emitted from the display device (1C) and incident on the eyes of the user (22) can be reduced.

[0230] The optical system (35) (optical system (3)) may have a moth eye structure film (40) located on the surface facing the semi-transparent mirror (6) of the fourth phase difference plate (26). By doing so, unwanted light and disturbance light, etc., can be reduced from being emitted from the display device (1C) after being reflected by the fourth phase difference plate (26) and entering the eyes of the user (22).

[0231] The reflective polarizer (8), the second phase difference plate (7), the third phase difference plate (25), the fourth phase difference plate (26), and the moth eye structure film (40), and the light-transmitting plate (38) may be integrated. By doing so, the display device (1C) can be made thinner in the depth direction (Z-axis direction). In addition, deformation of the reflective polarizer (8), the second phase difference plate (7), the third phase difference plate (25), the fourth phase difference plate (26), the moth eye structure film (40), and the light-transmitting plate (38) can be reduced.

[0232] The display device (1C) may have a touch panel (41). The touch panel (41) may block at least partially the window (37). The touch panel (41) may be attached to the housing (36) as shown in FIGS. 35 and 36. The touch panel (41) may be attached to the housing (36) to cover the window (37) in which the light-transmitting plate (38) is placed, as shown in FIGS. 35 and 36. The touch panel (41) may cover the light-transmitting plate (38). The touch panel (41) is connected to communicate with the controller (43) via a wired or wireless communication line. By doing so, the user (22) can operate the display device (1C) through the touch panel (41). The touch panel (41) may be a known touch panel.

[0233] The display system (200) of the present disclosure will be described. As shown in FIG. 39, the display system (200) comprises a display device (1, 1A, 1A', 1B, 1C) and a camera (201). A display panel (2) of the display device (1, 1A, 1A', 1B, 1C) can communicate with the camera (201) and displays an image captured by the camera (201). The display panel (2) and the camera (201) may be connected, for example, via a wired, wireless, or CAN (Controller Area Network).

[0234] The vehicle (23) of the present disclosure is equipped with a display system (200). The display device (1, 1A, 1A', 1B, 1C) is a small display device and does not occupy a large volume within the driver's cabin of the vehicle (23) even when placed therein, so it does not interfere with driving. Therefore, the user (22) can properly see a virtual image (V) or a real image. The display system (200) may be applied to the digital rearview mirror of the vehicle (23) or to the digital side mirror (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 FIG. 10 and 12) within the dashboard of the vehicle (23).

[0235] According to the present disclosure, it is possible to reduce the degradation of display quality in a compact display device and to improve light utilization efficiency. Furthermore, according to the present disclosure, a compact imaging device capable of clearly showing a virtual image to a user can be provided.

[0236] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments described above. Various modifications and improvements are possible within the scope of the essence of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in each other embodiments are also included within the technical scope of the invention according to the present disclosure. For example, functions included in each component, etc., can be rearranged so as not to be logically contradictory, and multiple components, etc., can be combined into one or divided. That is, those skilled in the art should note that it is easy to make various modifications or variations based on the present disclosure. Furthermore, it should be noted that such modifications, variations, or variations are included within the scope of the present disclosure.

[0237] The display device of the present disclosure can be implemented in the following forms (1) to (48).

[0238] (1) A display panel that emits linearly polarized display light, and

[0239] A first phase difference plate facing the above-mentioned display panel, and

[0240] A second phase difference plate spaced apart from the first phase difference plate, and

[0241] A reflective polarizer that transmits polarization having a polarization axis parallel to the polarization axis of the display light and reflects polarization having a polarization axis perpendicular to the polarization axis of the display light,

[0242] A semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a reflective surface facing the second phase difference plate, and

[0243] A display device in which the first phase difference plate and the second phase difference plate are quarter-wave plates.

[0244] (1') A display panel that emits a display light, and

[0245] A first phase difference plate facing the above-mentioned display panel, and

[0246] A second phase difference plate spaced apart from the first phase difference plate, and

[0247] A reflective polarizer disposed opposite to the second phase difference plate and transmitting the first polarization and reflecting the second polarization, and

[0248] A semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a reflective surface facing the second phase difference plate, and

[0249] The first phase difference plate and the second phase difference plate are a display device that makes the display light into the first polarization and the second polarization.

[0250] (2) A display device described in (1) in which air is interposed between the first phase difference plate and the second phase difference plate.

[0251] (3) A display device described in (1) or (2) having a third phase difference plate disposed between the display panel and the reflective polarizer.

[0252] (4) A display device described in (3) having a fourth phase difference plate disposed between the display panel and the reflective polarizer.

[0253] (5) The display device described in (4), wherein one of the third phase difference plate and the fourth phase difference plate is a quarter-wave plate and the other is a half-wave plate.

[0254] (6) The third phase difference plate and the fourth phase difference plate are half-wave plates, which is the display device described in (4).

[0255] (7) A display device described in any one of (1) to (6) wherein the reflective surface of the above semi-transparent mirror is concave.

[0256] (8) The above-mentioned semi-transparent mirror is a flat-panel optical element composed of a holographic optical element, and is a display device described in any one of (1) to (6).

[0257] (9) The above-mentioned semi-transparent mirror is a display device described in any one of (1) to (6) including a Fresnel lens.

[0258] (10) The above semi-transparent mirror is a display device described in (8) or (9) that is integrated with the above first phase difference plate and / or the above second phase difference plate.

[0259] (11) A display panel that emits linearly polarized display light, and

[0260] A first phase difference plate facing the above-mentioned display panel, and

[0261] A second phase difference plate spaced apart from the first phase difference plate, and

[0262] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0263] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate, and

[0264] A polarizing plate facing the second phase difference plate is provided,

[0265] A display device in which the first phase difference plate and the second phase difference plate are quarter-wave plates.

[0266] (11') A display panel that emits a display light, and

[0267] A first phase difference plate facing the above-mentioned display panel, and

[0268] A second phase difference plate spaced apart from the first phase difference plate, and

[0269] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0270] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate, and

[0271] A polarizing plate facing the second phase difference plate is provided,

[0272] A display device in which the first phase difference plate and the second phase difference plate make the display light into a first polarization that transmits the polarizing plate and a second polarization that transmits less through the polarizing plate than the first polarization.

[0273] (12) The second reflective surface is a convex surface protruding toward the first phase difference plate side, and is a display device described in (11).

[0274] (13) A display device described in (11) or (12) in which air is interposed between the first semi-transparent mirror and the first phase difference plate.

[0275] (14) A display device described in any one of (11) to (13) having a third phase difference plate disposed between the display panel and the polarizing plate.

[0276] (15) A display device described in (14) having a fourth phase difference plate disposed between the display panel and the polarizer.

[0277] (16) The display device described in (15), wherein one of the third phase difference plate and the fourth phase difference plate is a quarter-wave plate and the other is a half-wave plate.

[0278] (17) The third phase difference plate and the fourth phase difference plate are half-wave plates, which is the display device described in (15).

[0279] (18) A display device described in any one of (11) to (17) having a concave shape, wherein the first reflective surface is a concave shape.

[0280] (19) The first semi-transparent mirror and the second semi-transparent mirror are flat optical elements composed of holographic optical elements, and the display device described in any one of (11) to (17).

[0281] (20) The first semi-transparent mirror and the second semi-transparent mirror are a display device described in any one of (11) to (17) including a Fresnel lens.

[0282] (21) The first translucent mirror is a display device described in (19) or (20) that is integrated with the display panel and / or the first phase difference plate.

[0283] (22) The second translucent mirror is a display device described in (19) or (20) that is integrated with the first phase difference plate and / or the second phase difference plate.

[0284] (23) A display panel that emits linearly polarized display light, and

[0285] A first phase difference plate facing the above-mentioned display panel, and

[0286] A second phase difference plate spaced apart from the first phase difference plate, and

[0287] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0288] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate, and

[0289] It is equipped with a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate, and

[0290] A display device in which the first phase difference plate and the second phase difference plate are quarter-wave plates.

[0291] (23') A display panel that emits a display light, and

[0292] A first phase difference plate that transmits the above-mentioned indicator light, and

[0293] A second phase difference plate spaced apart from the first phase difference plate, and

[0294] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0295] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate, and

[0296] A display device having a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate.

[0297] (24) A display device described in (23) in which air is interposed between the first semi-transparent mirror and the first phase difference plate, and between the third semi-transparent mirror and the second phase difference plate.

[0298] (25) The first reflective surface and the fourth reflective surface are concave in the display device described in (23) or (24).

[0299] (26) The first semi-transparent mirror and the third semi-transparent mirror are flat optical elements composed of holographic optical elements, and are the display devices described in (23) or (24).

[0300] (27) The first semi-transparent mirror and the third semi-transparent mirror are a display device described in (23) or (24) that includes a Fresnel lens.

[0301] (28) The first translucent mirror is a display device described in (26) or (27) that is integrated with the display panel and / or the first phase difference plate.

[0302] (29) The second semi-transparent mirror is a display device described in any one of (26) to (28) that is integrated with the second phase difference plate.

[0303] (30) The above display light includes a display light for the left eye image and a display light for the right eye image, and

[0304] A display device described in any one of (1) to (29) further comprising an optical element that defines the direction of each light beam of the display light of the image for the left eye and the display light of the image for the right eye.

[0305] (31) A device for forming an image that includes a display device described in any one of (1) to (30) above.

[0306] (32) A visualization device described in (31) that includes a binocular visible area in which a virtual image projected within the user’s field of vision is visible to both the user’s left and right eyes, a left eye visible area in which the image is visible only to the left eye, and a right eye visible area in which the image is visible only to the right eye.

[0307] (33) Display panel and,

[0308] An optical system that projects display light emitted from the above-mentioned display panel as a virtual or real image, and

[0309] A housing that accommodates the above-mentioned display panel and the above-mentioned optical system is provided,

[0310] The above housing has a window that transmits light emitted from the optical system, and

[0311] A display device in which, when looking at the window of the housing, the window, the optical system, and the display panel are arranged to overlap.

[0312] (34) The above housing is a display device described in (33) having a light-transmitting plate placed in the window.

[0313] (35) A display device described in (34) having a touch panel attached to the housing to cover the light-transmitting plate.

[0314] (36) A display device described in any one of (1) to (30) and (33) to (35) having an irradiator that irradiates light to the side opposite to the display surface of the display panel.

[0315] (37) A display device described in (1) to (30) and (33) to (36) having a controller having the function of controlling at least one of the image displayed on the display panel and the irradiator.

[0316] (38) A vehicle having the display device described in (37) above.

[0317] (39) A display panel that emits linearly polarized display light, and

[0318] A first phase difference plate facing the above-mentioned display panel, and

[0319] A second phase difference plate spaced apart from the first phase difference plate, and

[0320] A reflective polarizer that transmits polarization having a polarization axis parallel to the polarization axis of the display light and reflects polarization having a polarization axis perpendicular to the polarization axis of the display light,

[0321] A semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a reflective surface facing the second phase difference plate,

[0322] The first phase difference plate and the second phase difference plate are quarter-wave plates, and

[0323] A display device in which the optical path length of light emitted from the above display panel, transmitted through the above semi-transparent mirror, reflected by the above reflective polarizer, and reaching the above semi-transparent mirror is smaller than the focal length of the above semi-transparent mirror.

[0324] (40) A display panel that emits linearly polarized display light, and

[0325] A first phase difference plate facing the above-mentioned display panel, and

[0326] A second phase difference plate spaced apart from the first phase difference plate, and

[0327] A reflective polarizer that transmits polarization having a polarization axis parallel to the polarization axis of the display light and reflects polarization having a polarization axis perpendicular to the polarization axis of the display light,

[0328] A semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a reflective surface facing the second phase difference plate,

[0329] The first phase difference plate and the second phase difference plate are quarter-wave plates, and

[0330] A display device in which the optical path length of light emitted from the above display panel, transmitted through the above semi-transparent mirror, reflected from the above reflective polarizer, and reaching the above semi-transparent mirror is greater than the focal length of the above semi-transparent mirror.

[0331] (41) A display panel that emits linearly polarized display light, and

[0332] A first phase difference plate that transmits the above-mentioned indicator light, and

[0333] A second phase difference plate spaced apart from the first phase difference plate, and

[0334] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0335] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate, and

[0336] A polarizing plate facing the second phase difference plate is provided,

[0337] The first phase difference plate and the second phase difference plate are quarter-wave plates, and

[0338] A display device in which the optical path length of light emitted from the above display panel, transmitted through the first semi-transparent mirror, reflected from the second semi-transparent mirror, and reaching the first semi-transparent mirror is smaller than the focal length of the first semi-transparent mirror.

[0339] (42) A display panel that emits linearly polarized display light, and

[0340] A first phase difference plate that transmits the above-mentioned indicator light, and

[0341] A second phase difference plate spaced apart from the first phase difference plate, and

[0342] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0343] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate, and

[0344] A polarizing plate facing the second phase difference plate is provided,

[0345] The first phase difference plate and the second phase difference plate are quarter-wave plates, and

[0346] A display device in which the optical path length of light emitted from the above display panel, transmitted through the first semi-transparent mirror, reflected from the second semi-transparent mirror, and reaching the first semi-transparent mirror is greater than the focal length of the first semi-transparent mirror.

[0347] (43) A display panel that emits linearly polarized display light, and

[0348] A first phase difference plate that transmits the above-mentioned indicator light, and

[0349] A second phase difference plate spaced apart from the first phase difference plate, and

[0350] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0351] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate, and

[0352] It is equipped with a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate, and

[0353] The first phase difference plate and the second phase difference plate are quarter-wave plates, and

[0354] A display device in which the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror and reflected from the second semi-transparent mirror to reach the first semi-transparent mirror is smaller than the focal length of the first semi-transparent mirror, and also the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror and passing through the second semi-transparent mirror to reach the third semi-transparent mirror is smaller than the focal length of the first semi-transparent mirror.

[0355] (44) A display panel that emits linearly polarized display light, and

[0356] A first phase difference plate that transmits the above-mentioned indicator light, and

[0357] A second phase difference plate spaced apart from the first phase difference plate, and

[0358] A first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface facing the first phase difference plate, and

[0359] A second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate, having a second reflective surface facing the first phase difference plate and a third reflective surface facing the second phase difference plate, and

[0360] It is equipped with a third semi-transparent mirror having a fourth reflective surface facing the second phase difference plate, and

[0361] The first phase difference plate and the second phase difference plate are quarter-wave plates, and

[0362] A display device in which the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror and reflected from the second semi-transparent mirror to reach the first semi-transparent mirror is greater than the focal length of the first semi-transparent mirror, and also the optical path length of light emitted from the display panel, passing through the first semi-transparent mirror and passing through the second semi-transparent mirror to reach the third semi-transparent mirror is greater than the focal length of the first semi-transparent mirror.

[0363] (45) A display panel that emits a display light, and

[0364] The above-mentioned convex lens through which the indicator light is transmitted is provided,

[0365] A display device in which the optical path length from the display panel to the convex lens is smaller than the focal length of the convex lens.

[0366] (46) A display panel that emits a display light, and

[0367] The above-mentioned convex lens through which the indicator light is transmitted is provided,

[0368] 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.

[0369] (47) A display device described in any one of (1) to (30), (33) to (37), and (39) to (46) above, and

[0370] Equip yourself with a camera,

[0371] The above display panel is capable of communicating with the camera and is a display system that displays an image captured by the camera.

[0372] (48) A vehicle equipped with the display system described in (47) above. Explanation of the symbols

[0373] 1, 1A, 1A', 1B; display device 2; Display panel 2a; display surface 3; Optical system 4; Investigator 5; 1st phase difference plate 6; Semi-transparent mirror 6a; reflective surface 7; 2nd phase difference plate 8; Reflective polarizer 9; Optical element 10; Optical system 11; First semi-transparent mirror 11a; reflective surface 12; 1st phase difference plate 13, 13'; second semi-transparent mirror 13a, 13'a; reflective surface 14; 2nd phase difference plate 15; polarizer 16; Optical system 17; First semi-transparent mirror 17a; reflective surface 18; 1st phase difference plate 19; Second semi-transparent mirror 19a; reflective surface 19b; reflective surface 20; 2nd phase difference plate 21; Third semi-transparent mirror 21a; reflective surface 22; user 22L; left eye 22R; Right eye 23; mobile body 24; Windshield 25; 3rd phase difference plate 26; 4th phase difference plate 27; Housing 28; opening 29; cluster 30; CID 31; PID 32; RSE 33; Fresnel lens 33a; 1st side 33b; 2nd side 33c; reference point 34; Semi-transparent reflective layer 35; Optical system 36; Housing 37; Genesis 38; Light-transmitting plate 39, 40; Morse 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 emitting display light; a first phase difference plate; a second phase difference plate spaced apart from the first phase difference plate; a semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate and having a reflective surface capable of reflecting light toward the second phase difference plate; a reflective polarizer disposed on the opposite side of the first phase difference plate with respect to the second phase difference plate and transmitting a first linear polarization and reflecting a second linear polarization; and a third phase difference plate disposed between the second phase difference plate and the reflective polarizer, disposed such that the optical axis is parallel or perpendicular to the transmission axis of the reflective polarizer, and configured to reduce the transmission of the second linear polarization by the reflective polarizer when viewed from a position other than the front, wherein the first phase difference plate and the second phase difference plate make the display light the second linear polarization, and the second phase difference plate A display device that converts the second linear polarization reflected by the reflective polarizer into the first linear polarization until the second linear polarization is reflected by the semi-transparent mirror and incident on the reflective polarizer again. Claim 2 A display device according to claim 1, wherein air is interposed between the first phase difference plate and the second phase difference plate. Claim 3 A display device according to claim 1, wherein the display panel has a polarizing plate, the reflective polarizing plate is positioned such that its transmission axis is parallel or perpendicular to the transmission axis of the polarizing plate, and a fourth phase difference plate is positioned between the display panel and the first phase difference plate and is positioned such that its optical axis is parallel or perpendicular to the transmission axis of the reflective polarizing plate. Claim 4 In claim 1, the display device wherein the third phase difference plate is a quarter-wave plate. Claim 5 In claim 3, the display device wherein the fourth phase difference plate is a quarter-wave plate. Claim 6 In claim 1, the third phase difference plate is a half-wave plate, and the display device. Claim 7 In claim 3, the fourth phase difference plate is a half-wave plate, which is a display device. Claim 8 A display device according to claim 1, wherein the reflective surface of the semi-transparent mirror is in a concave shape. Claim 9 In claim 1, the semi-transparent mirror is a display device in which the semi-transparent mirror is a flat optical element composed of a holographic optical element. Claim 10 In claim 1, the semi-transparent mirror is a display device comprising a Fresnel lens. Claim 11 In claim 1, the semi-transparent mirror is a display device integrated with the first phase difference plate and / or the second phase difference plate. Claim 12 A display device according to claim 1, wherein the display light includes a display light for a left eye image and a display light for a right eye image, and further includes an optical element that defines the direction of each light beam of the display light for the left eye image and the display light for the right eye image. Claim 13 An imaging device comprising a display device described in claim 1. Claim 14 A display device according to claim 1, comprising an irradiator that irradiates light to a surface opposite to the display surface of the display panel that emits the display light. Claim 15 A display device according to claim 14, comprising a controller having a function to control at least one of an image displayed on the display panel and the illuminator. Claim 16 A vehicle equipped with a display device described in Clause 15. Claim 17 A vehicle equipped with a display device described in claim 1. Claim 18 A display system comprising a display device described in claim 1 and a camera, wherein the display panel is capable of communicating with the camera and displays an image captured by the camera. Claim 19 A vehicle equipped with the display system described in Clause 18. Claim 20 A vehicle equipped with a imaging device as described in Clause 13. Claim 21 delete Claim 22 delete Claim 23 delete Claim 24 delete Claim 25 delete Claim 26 delete Claim 27 delete Claim 28 delete Claim 29 delete Claim 30 delete Claim 31 delete Claim 32 delete Claim 33 delete Claim 34 delete Claim 35 delete Claim 36 delete Claim 37 delete Claim 38 delete Claim 39 delete Claim 40 delete Claim 41 delete Claim 42 delete

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