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

Abstract

Provided is a display device (1) comprising: a display panel (2) having a display surface (2a) that emits display light; and a reflection member (6) having a display-side surface (surface on the opposite side from 6a) that is located on the display surface side of the display panel, and a reflection surface (6a) that is located on the opposite surface from the display-side surface. In the display device, the reflection member (6) is disposed with the reflection surface (6a) being inclined with respect to the optical axis of the display light, reducing the visibility of incident images formed by external light as a reflected inverted image, and display quality is improved.

Description

Display device, moving body, display system, and display panel housing device

[0001] The present disclosure relates to a display device, a moving body, a display system, and a display panel housing device.

[0002] Conventionally, various small display devices used for a digital room mirror disposed in a vehicle interior, a head-mounted display worn on a user's head, and the like have been proposed. For example, Patent Document 1 discloses a display device that emits display light emitted from a display panel through a plurality of optical members such as a retardation plate, a concave mirror, and a reflective polarizing plate.

[0003] Japanese Patent Application Laid-Open Publication "JP-A-2022-63533"

[0004] The display device of the present disclosure includes a display panel having a display surface that emits display light, a display side surface located on the display surface side of the display panel, and a reflection member having a reflection surface located on the opposite side of the display side surface, and the reflection member is disposed in a posture in which the reflection surface is inclined with respect to the optical axis of the display light.

[0005] This is a diagram schematically showing the configuration of one embodiment of the display device of the present disclosure. This is a cross-sectional view showing the configuration of the display device in an exploded view. This is a cross-sectional view showing the configuration of the display device. This is a diagram for explaining the principle of generating a virtual image of the display light by the display device. This is a plan view of the semi-transparent mirror viewed from above. This is a diagram showing one embodiment of the display device according to the present disclosure. This is a front view showing the state in which a reflected inverted image is displayed on the display device. This is an optical path diagram of the display light. This is a diagram for explaining the generation position of the background real image. This is a diagram for explaining the generation position of the background real image. This is a diagram showing the configuration of the display device used in the simulation of the display position of the reflected inverted image by the display device when viewed directly from the semi-transparent mirror. This is a diagram showing the size of the imaging region of the virtual image. This is a diagram showing the configuration of the display device used in the simulation. This is a diagram showing the background image panel used in the simulation. This is a diagram showing the display image used in the simulation. This is a diagram showing the display state when the display panel of the display device used in the simulation is viewed directly from the display panel. This is a diagram showing the display state of the display panel when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 6°. This is a diagram showing the display state of the display panel when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -6°. This figure shows the display state of the virtual image when the semi-transparent mirror of the display device used in the simulation is facing directly without tilting. This figure shows the display state of the virtual image when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 6°. This figure shows the display state of the virtual image when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -6°. This figure shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is facing directly without tilting. This figure shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 3°. This figure shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -3°. This figure shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is facing directly without tilting. This figure shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted at an inclination angle θ = 6°.This figure shows the display state of a simulated image when the semi-transparent mirror of the display device used in the simulation is tilted at an inclination angle θ = -6°. This is a cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure. This is a front view of the display device of Figure 19. This is a front view showing another modified example of the display device of the embodiments of Figures 19 and 20. This is a cross-sectional view showing an exploded view of the configuration of another embodiment of the display device of the present disclosure figure showing the interior of a vehicle equipped with a display device.

[0006] Conventional display devices have a concave mirror, which means that when ambient light enters the concave mirror, an inverted image of the user or other object is superimposed as a reflected image on the upright image of the displayed light, resulting in a decrease in display quality.

[0007] The display device and vehicle of this disclosure can reduce reflected inverted images caused by incident ambient light and improve display quality.

[0008] Embodiments of the present disclosure will be described below with reference to the drawings. The figures used in the following description are schematic, and the dimensional ratios, etc., shown in the drawings do not necessarily correspond to those of reality. The figures used in the following description show the main components of the display device of the present disclosure. The display device of the present disclosure may include well-known components not shown, such as optical system holders and housings. In this specification, in some drawings, a Cartesian coordinate system XYZ is defined for convenience. The X-axis direction is also referred to as the left-right direction. The Y-axis direction is also referred to as the height direction. The Z-axis direction is also referred to as the output direction or depth direction.

[0009] Figure 1 is a schematic diagram showing the configuration of one embodiment of the display device of the present disclosure. The display device 1 of this embodiment comprises a display panel 2 and an optical system 3. The optical system 3 forms a virtual image V of the display light emitted from the display panel 2 within the field of view of the user 22. The optical system 3 may also be configured to form a real image of the display light within the field of view of the user 22. The display device 1 causes a portion of the display light emitted from the display panel 2 to enter the left eye 22L and right eye 22R of the user 22, allowing the user 22 to view it as an image, picture, or aerial image. The display device 1 can allow the user 22 to view the display of the display panel 2 at a position different from the position of the display panel 2. In the positional embodiment of the present disclosure, the display device 1 allows the user 22 to view it as a virtual image V. The virtual image V may be formed at a distance from the display panel 2 (negative direction in the Z-axis direction) or at a distance from the display panel 2 (positive direction in the Z-axis direction) within the field of view of the user 22. The virtual image V may be an upright virtual image which is an enlarged version of the image displayed on the display panel 2. The real image may be formed at a distance from the display panel 2 (negative direction in the Z-axis direction) or at a distance from the display panel 2 (positive direction in the Z-axis direction) as viewed from the user 11. The display device 1 of one embodiment of this disclosure may be a non-mountable device for the user 22. That is, it may not be mounted on the user 22 but may be fixed to the environment. The display device 1 may be fixed to, for example, a wall, column or ceiling. The display device 1 may also be fixed to the interior of a vehicle. The display device 1 may be mounted on the user 22. When mounted on the user 22, the display device 1 may have a mounting part (not shown) so that the window 37 is fixed at the position of the user 22's eyes.

[0010] Figure 2A is a cross-sectional view showing the configuration of the display device in an exploded state, Figure 2B is a cross-sectional view showing the configuration of the display device, and Figure 3 is a diagram for explaining the principle of generating a virtual image of display light by the display device. In Figure 3, the irradiator 4, the first phase difference plate, and the second phase difference plate are omitted for ease of illustration. The display device 1 may include a display panel 2 having a display surface 2a that emits linearly polarized display light, an irradiator 4 located behind the display panel 2, a first phase difference plate located on the side of the display surface 2a of the display panel 2, a second phase difference plate positioned at a distance Z from the first phase difference plate in the emission direction, a semi-transparent mirror 6 which is a first reflective member having a reflective surface 6a located on the side of the second phase difference plate, opposite to the display panel 2 and the irradiator 4 relative to the first phase difference plate, and on the side of the second phase difference plate, and a reflective polarizing plate 8 located on the side of the second phase difference plate opposite to the side of the semi-transparent mirror 6. The side of the semi-transparent mirror 6 opposite to the reflective surface 6a (the side located on the display surface 2a side of the display panel 2) corresponds to the display side.

[0011] In this embodiment, we will describe the case in which a first quarter-wave plate 5 is used as the first phase difference plate and a second quarter-wave plate 7 is used as the second phase difference plate. These irradiator 4, display panel 2, first quarter-wave plate 5, semi-transparent mirror 6, second quarter-wave plate 7, and reflective polarizer 8 are arranged in this order in the direction Z of the emission direction of the display light from the display panel 2. The optical system 3 is composed of the aforementioned first quarter-wave plate 5, semi-transparent mirror 6, second quarter-wave plate 7, and reflective polarizer 8.

[0012] The first quarter-wave plate 5 may be integrated with the display panel 2. Integration means that the display panel 2 and the first quarter-wave plate 5 are arranged to be in contact with each other, and they may be joined together with an optically transparent adhesive such as OCA (Optically Clear Adhesive).

[0013] The semi-transparent mirror 6 is positioned between the first quarter-wave plate 5 and the second quarter-wave plate 7, and may be arranged in a predetermined orientation that reflects the inverted image of ambient light incident on the display device 1 other than the display light, away from the imaging region of the virtual image V of the display light. The predetermined orientation may be, for example, set so that the semi-transparent mirror 6 is angularly displaced from the frontal position by a predetermined inclination angle θ to one side around a first axis L10 perpendicular to the optical axis L0 of the display surface 2a, or it may be set to a forward-tilted position. The frontal position is the state in which the semi-transparent mirror 6 is positioned so that the optical axis of the reflective surface 6a of the semi-transparent mirror 6 coincides with or is parallel to the optical axis L0 of the display surface 2a. The predetermined inclination angle θ may be 5° or more and less than 90°. Alternatively, the predetermined inclination angle θ may be 2° or more and less than 90°, 2° or more and 15° or less, 6° or more and 12° or less, or 8° or more and 10° or less. When the semi-transparent mirror 6 is tilted at a predetermined angle θ with respect to the optical axis L0, the focal point Om of the semi-transparent mirror 6 may be located below the optical axis L0. Light incident perpendicularly to the reflective surface 6a of the semi-transparent mirror 6 is directed toward the focal point Om. Light emitted from the focal point Om is incident on the reflective surface 6a and then travels perpendicularly to the reflective surface 6a. The display light of the display panel 2 generates a mirror image (virtual image) V5 by specular reflection by the reflective polarizer 8. This mirror image V5 passes through the tilted semi-transparent mirror 6 and is imaged in the imaging region of the virtual image V. In this way, when the semi-transparent mirror 6 is positioned in the forward-tilting position which is the predetermined position described above, it has a reflective surface 6a that reflects the inverted image of the reflected ambient light away from the imaging region of the virtual image of the display light.

[0014] The predetermined orientation of the semi-transparent mirror 6 is not limited to the forward tilt orientation described above. In other embodiments, the semi-transparent mirror 6 may be tilted backward by a predetermined inclination angle θ, where it is angularly displaced by a predetermined inclination angle θ to the opposite side from the aforementioned side, around a first axis L10 perpendicular to the optical axis L0. In this case, when the semi-transparent mirror 6 is tilted at a predetermined inclination angle θ with respect to the optical axis L0, the focal point Om of the semi-transparent mirror 6 may be located above the optical axis L0. Furthermore, in other embodiments, the predetermined orientation of the semi-transparent mirror 6 may be a rightward tilt orientation, which is a first tilt orientation where the semi-transparent mirror 6 is angularly displaced by a predetermined inclination angle θ to one side, around a second axis L12 perpendicular to the optical axis L0 and the first axis L10, as shown by the dashed line 61 in the plan view of Figure 4 as seen from above. Furthermore, in other embodiments, the predetermined orientation of the semi-transparent mirror 6 may be a left-tilted orientation, which is a second tilted orientation in which the semi-transparent mirror 6 is angularly displaced by a predetermined tilt angle θ from the frontal position to the opposite side to the aforementioned side, around a second axis L12 perpendicular to the optical axis L0 and the first axis L10, as shown by the dashed line 62 in Figure 4.

[0015] Furthermore, the predetermined orientation of the semi-transparent mirror 6 is not limited to the forward tilt, backward tilt, right tilt, and left tilt orientations described above. For example, the predetermined orientation of the semi-transparent mirror 6 may be a forward tilt or a backward tilt and also a right tilt or left tilt. Alternatively, the predetermined orientation of the semi-transparent mirror 6 may be an orientation in which it is linearly moved in a direction perpendicular to the optical axis L0. The orientation in which it is linearly moved in a direction perpendicular to the optical axis L0 is not limited to a specific position, as long as the virtual image of the display light is displayed in the imaging region and the reflected inverted image is excluded outside the imaging region of the virtual image.

[0016] The display panel 2 has a display surface 2a, on which a display image is displayed. In other words, the display panel 2 emits display light of the display image from the display surface 2a. The display panel 2 is configured to emit linearly polarized display light. The following description will focus on, but is not limited to, the case in which the display panel 2 emits S-wave polarized display light. For example, if the display panel 2 emits P-wave polarized display light, then S-wave polarization in the following description may be read as P-wave polarization, and P-wave polarization may be read as S-wave polarization.

[0017] The display panel 2 may be a liquid crystal panel. The display panel 2 may be a known liquid crystal panel. Examples of known liquid crystal panels include IPS (In-Plane Switching), FFS (Fringe Field Switching), VA (Vertical Alignment), and ECB (Electrically Controlled Birefringence) liquid crystal panels. The display panel 2 may include a liquid crystal layer, two glass substrates arranged so as to sandwich the liquid crystal layer, and a color filter. The display panel 2 is not limited to a liquid crystal panel and may be a MEMS (Micro Electro Mechanical Systems) shutter type display panel. In the following description, the display panel 2 will be assumed to be a liquid crystal panel. The liquid crystal panel may have the configuration of a known liquid crystal panel. Examples of known liquid crystal panels include IPS (In-Plane Switching), FFS (Fringe Field Switching), VA (Vertical Alignment), and ECB (Electrically Controlled Birefringence) liquid crystal panels.

[0018] The display device 1 may include an irradiator 4 that illuminates the display panel 2 in a planar manner. The irradiator 4 is also called a backlight. The irradiator 4 may be an edge-lit backlight or a direct-lit backlight. An edge-lit backlight has one or more light sources arranged on the outer periphery of the display panel 2, and is configured to guide the light emitted from the light sources to the entire back surface of the display panel 2 uniformly by a light guide plate. A direct-lit backlight has a plurality of point light sources arranged on the back side of the display panel 2, and illuminates the display panel 2 with light emitted from the plurality of point light sources. The light source of the irradiator 4 may be a cold cathode fluorescent lamp, a halogen lamp, or a xenon lamp, and the point light source 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 optical components whose optical properties are wavelength-dependent, becomes easier. The irradiator 4 includes a backlight control unit. The backlight control unit may be configured to perform local dimming control by switching multiple light sources between an illuminated state and a non-illuminated state depending on the image displayed on the display panel 2.

[0019] The display panel 2 is not limited to a liquid crystal panel (transmissive display panel). The display panel 2 may be a self-emissive display panel that includes self-emissive elements such as a light-emitting diode (LED), an organic light-emitting diode (OLED), or a semiconductor laser (LD).

[0020] The first quarter-wave plate 5 may be located on the side of the display surface 2a of the display panel 2. The first quarter-wave plate 5 may be located at a distance from the display surface 2a in the direction Z of emission of display light from the display panel 2. The second quarter-wave plate 7 may be located at a distance from the first quarter-wave plate 5 in the direction Z of emission of display light from the display panel 2. The first quarter-wave plate 5 and the second quarter-wave plate 7 may emit light with a phase difference of π / 2 (= λ / 4) between the two vertical polarization components of the incident light.

[0021] The semi-transparent mirror 6 may be positioned between the first quarter-wave plate 5 and the second quarter-wave plate 7. The semi-transparent mirror 6 may transmit a portion of the incident light (for example, approximately 50%) and reflect the remainder (for example, approximately 50%). The transmittance and reflectance of light incident on the semi-transparent mirror 6 are not limited to 50%. The semi-transparent mirror 6 may have a function to collect or focus light. Specifically, the semi-transparent mirror 6 may have a function to collect or focus light that has been incident on and reflected from the semi-transparent mirror 6. The semi-transparent mirror 6 may be a concave mirror having a concave reflective surface 6a, as shown in Figures 2A and 2B. The reflective surface 6a of the semi-transparent mirror 6 may be positioned on the side of the second quarter-wave 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. The semi-transparent mirror 6 may focus or concentrate light more effectively than other components of the optical system 3. In other words, the semi-transparent mirror 6 may have a larger degree of focusing, convergence, or an index expressed as the reciprocal of the focal length than other components of the optical system 3. The reflective surface 6a of the semi-transparent mirror 6 may have a greater curvature than other components of the optical system 3. The optical system 3 may have only the semi-transparent mirror 6 as a component with a focusing or converging function. Furthermore, the semi-transparent mirror 6 may be composed of a holographic optical element (HOE), or its surface shape may have a Fresnel shape.

[0022] The reflective surface 6a of the semi-transparent mirror 6 may have an optical center OC. The optical center OC may be the vertex of the curvature of the reflective surface 6a. If the reflective surface 6a is a freeform surface (XY polynomial surface) defined by the following equations (1) and (2), the optical center OC may be the origin of the freeform surface (x=y=z=0). The XY polynomial surface is expanded into polynomials up to the 10th order that are added to the reference conic surface. In equations (1) and (2), the sum of m and n is 10 or less. In equation (1), z is the sag of a plane parallel to the z axis (optical axis), c is the vertex curvature, and r is the radial distance (i.e., r ２ = x ２ +y ２ ) where k is the conic constant, C ｊ is a monomial x ｍ y ｎ This is the coefficient.

[0023] The reflective surface 6a may be aspherical in shape. In other words, it may be defined by a quadratic surface such as a paraboloid, ellipsoid, or hyperboloid. If the reflective surface 6a is defined by a quadratic surface, the optical center OC of the reflective surface 6a may be a vertex of the quadratic surface.

[0024] Next, we will discuss the curvature. The semi-reflecting mirror 6 has a curvature S31a. The curvature S31a will be explained below with reference to Figure 2A.

[0025] Figure 2A schematically shows a cross-section of the semi-transparent mirror 6 obtained by cutting it through the optical center OC of the reflective surface 6a with a cutting plane along the optical axis of the reflective surface 6a. The cutting plane along the optical axis may be parallel to the YZ plane. As shown in Figure 2A, the tangent plane of the reflective surface 6a at the optical center OC is defined as the tangent plane T. Points E1 and E2 are located at both ends of the reflective surface 6a, and point H1 is the intersection of the perpendicular line drawn from point E1 to the tangent plane T and the tangent plane T. Point H2 is the intersection of the perpendicular line drawn from point E2 to the tangent plane T and the tangent plane T. Furthermore, the distance between the optical center OC and point H1 is defined as L1, the distance between the optical center OC and point H2 is defined as L2, the distance between point E1 and point H1 is defined as D1, and the distance between point E2 and point H2 is defined as D2. In this case, the curvature S31a is defined by D1 / L1. In other words, it is the curvature of the portion above the optical center OC. The curvature S31a is also called the upper curvature.

[0026] In this embodiment, when the portion of the semi-transparent mirror 6 closer to the display panel 2 is designated as the first portion 161, with respect to the optical center OC of the semi-transparent mirror 6, and the portion of the semi-transparent mirror 6 other than the first portion 161 is designated as the second portion 162, the curvature S31a of the second portion 162 may be greater than the curvature of the first portion 161.

[0027] In another embodiment, the portion of the first portion 161 closer to the optical center OC may be designated as the third portion 163, and the portion further from the optical center OC than the third portion 163 may be designated as the fourth portion 164. In this configuration, the curvature S31a of the fourth portion 164 may be greater than the curvature of the third portion 163.

[0028] The semi-transparent mirror 6 is composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) that are semi-transparent reflective layers 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 metal nanowires. The metal nanowires may be composed of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a thin metal film, but 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 mirror 6 can transmit light components vibrating in a direction orthogonal to the metal nanowire grid and can reflect light components vibrating in a direction parallel to the metal nanowire grid.

[0029] The reflective polarizer 8 may be located on the side of the second quarter-wave plate 7 opposite to the side of the semi-transparent mirror 6. In other words, the reflective polarizer 8 may be located downstream of the second quarter-wave plate 7 in the direction Z of the light emission direction of 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 may be configured to reflect polarized light having a polarization axis perpendicular to the polarization axis of the display light (also called P-wave polarization or second polarization) and transmit polarized light having a polarization axis parallel to the polarization axis of the display light (also called S-wave polarization or first polarization). In this case, the positional relationship between the first quarter-wave plate 5 and the second quarter-wave plate 7 may be defined such that when the first quarter-wave plate 5 and the second quarter-wave plate 7 are viewed along the Z-axis direction, the retard axis of the second quarter-wave plate 7 and the retard axis of the first quarter-wave plate 5 are parallel. Furthermore, for example, the reflective polarizer 8 may be configured to transmit polarized light having a polarization axis perpendicular to the polarization axis of the display light (also called P-wave polarized light or first polarization) and to reflect polarized light having a polarization axis parallel to the polarization axis of the display light (also called S-wave polarized light or second polarization). In this case, the positional relationship between the first quarter-wave plate 5 and the second quarter-wave plate 7 may be defined such that when the first quarter-wave plate 5 and the second quarter-wave plate 7 are viewed along the Z-axis, the lagging axis of the second quarter-wave plate 7 is perpendicular to the lagging axis of the first quarter-wave plate 5. The reflective polarizer 8 may have a function to diverge the light that is incident on the second semi-transparent mirror 131 and reflected. The reflective polarizer 8 may have a function to collect or focus the light that is incident on the second semi-transparent mirror 131 and reflected. The reflective polarizing plate 8 may be flat, or it may have a concave shape facing the display panel 2, or it may have a convex shape facing the display panel 2. Furthermore, the reflective polarizing plate 8 may be composed of a holographic optical element (HOE), or its surface shape may have a Fresnel shape.

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

[0031] The display device 1 includes a controller. The controller is connected to and controls each component of the display device 1. The controller may include one or more processors. The processors may include application-specific integrated circuits (ASICs). They may include general-purpose processors configured to load specific programs and execute specific functions, and dedicated processors specialized for specific processing. The processors may include programmable logic devices (PLDs). The controller 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 includes a memory unit, which may store various information or programs for operating each component of the display device 1. The memory unit may be composed of, for example, semiconductor memory. The memory unit may function as the controller's work memory.

[0032] The optical function of the optical system 3 will be explained with reference to Figures 2A and 2B. The display panel 2 emits display light that is S-wave polarized (first linearly polarized light L1). The display light of the first linearly polarized light L1 emitted from the display panel 2 passes through the first quarter-wave plate 5 and is converted into light that is first circularly polarized C1. A portion of the first circularly polarized light C1 that has passed through the first quarter-wave plate 5 (for example, about 50%) passes through the semi-transparent mirror 6. The first circularly polarized light C1 that has passed through the semi-transparent mirror 6 passes through the second quarter-wave plate 7 and is converted into light that is second linearly polarized L2, whose polarization direction is perpendicular to that of the first linearly polarized light L1 (i.e., it is P-wave polarized). The light of the second linearly polarized light L2 is incident on the reflective polarizer 8. As described above, the reflective polarizer 8 may reflect P-wave polarized light and transmit 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 is transmitted through the second quarter-wave plate 7 and converted into second circularly polarized light C2. A portion of the second circularly polarized light C2 that has been transmitted through the second quarter-wave plate 7 (for example, about 50%) is reflected by the semi-transparent mirror 6 and converted into third circularly polarized light C3. The third circularly polarized light C3 is transmitted through the second quarter-wave plate 7 and converted into fourth linearly polarized light L4 whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized). The fourth linearly polarized light L4 is transmitted through the reflective polarizer 8 and emitted to the outside. The amount of light emitted from the display device 1 is, for example, about 25% of the amount of display light emitted from the display panel 2.

[0033] Another optical function of the optical system 3 will now be described. The display panel 2 emits display light of first linear polarization L1. The display light of first linear polarization L1 emitted from the display panel 2 passes through the first quarter-wave plate 5 and is converted into light of first circular polarization C1. A portion of the first circular polarization C1 that has passed through the first quarter-wave plate 5 (for example, approximately 50%) passes through the semi-transparent mirror 6. The first circular polarization C1 that has passed through the semi-transparent mirror 6 passes through the second quarter-wave plate 7 and is converted into light of second linear polarization L2, whose polarization direction is parallel to that of the first linear polarization L1. The light of second linear polarization L2 is incident on the reflective polarizer 8. The light of second linear polarization L2 that has been incident on the reflective polarizer 8 is reflected by the reflective polarizer 8 and converted into light of third linear polarization L3. The light of third linear polarization L3 is transmitted through the second quarter-wave plate 7 and is converted into light of second circular polarization C2. A portion of the light of the second circularly polarized light C2 that has passed through the second quarter-wave plate 7 (for example, about 50%) is reflected by the semi-transparent mirror 6 and converted into light of the third circularly polarized light C3. The light of the third circularly polarized light C3 passes through the second quarter-wave plate and is converted into light of the fourth linearly polarized light L4, whose polarization direction is perpendicular to that of the first linearly polarized light L1. The light of the fourth linearly polarized light L4 passes through the reflective polarizer 8 and is emitted to the outside. The amount of light (luminance) emitted from the display device 1 is, for example, about 25% of the amount of light (luminance) of the display light emitted from the display panel 2.

[0034] In one embodiment of the present disclosure, the first to third linearly polarized elements L1 to L3 described above may be S-wave polarized elements, and the fourth linearly polarized element L4 may be P-wave polarized elements.

[0035] The display device 1 of this embodiment may have a configuration in which the display panel 2 and the first quarter-wave plate 5 are in surface contact and the second quarter-wave plate 7 and the reflective polarizing plate 8 are in surface contact, as shown in Figure 2B, or the display panel 2 and the first quarter-wave plate 5 may be bonded together with a light-transmitting adhesive and the second quarter-wave plate 7 and the reflective polarizing plate 8 may be bonded together with a light-transmitting adhesive.

[0036] The first quarter-wave plate 5 and the second quarter-wave plate 7 should be configured to provide the necessary phase difference to the display light transmitted through them, such that the light transmitted through them is reflected by the reflective polarizer 8. In other words, the first quarter-wave plate 5 and the second quarter-wave plate 7 provide a phase difference of 1 / 4 wavelength to the polarization plane (the polarization plane in the direction of electric field vibration) of the incident light. This allows a portion of the display light emitted from the display panel 2 to be reflected by the reflective polarizer 8 and incident on the semi-transparent mirror 6. Furthermore, the first and second phase difference plates should be configured to provide a phase difference such that the light transmitted through them is reflected by the reflective polarizer 8. Such phase difference plates are not limited to quarter-wave plates; other wavelength plates may also be used. In other words, the first phase difference plate and the second phase difference plate may be other wave plates or a combination thereof, rather than quarter-wave plates, as long as the second polarization is obtained by passing through the first and second phase difference plates. Furthermore, the second phase difference plate only needs to be able to provide the necessary phase difference to the light that has passed through the second phase difference plate so that the light that has been reflected by the reflective polarizing plate 8 and passed through the second phase difference plate passes through the reflective polarizing plate 8 again when it reaches the reflective polarizing plate 8. In other words, for example, when the polarization obtained by reflecting by the reflective polarizing plate 8 and passing through the second phase difference plate is taken as the first polarization, the second phase difference plate may be other wave plates rather than quarter-wave plates, as long as the first polarization is obtained. In this disclosure, the case in which the first phase difference plate and the second phase difference plate 7 are quarter-wave plates will be explained as an example. Furthermore, the first phase difference plate and the second phase difference plate may be film-like members.

[0037] Figure 5 shows one embodiment of the display device according to the present disclosure. The display device of this embodiment will now be described. The display device 100 of this embodiment includes the display device 1 described above. The display device 100 causes the user 22 to view the display light emitted from the display panel 2 as a virtual image V. Since the display device 100 includes the display device 1, a compact display device can be realized, and the user 22 can view a virtual image V with improved display quality and the elimination of reflected inverted images. In particular, when the display device 100 includes the display device 1, a thin display device can be realized.

[0038] The display device 100 may be mounted on the mobile body 23, as shown in Figure 5. The mobile body 23 may be a vehicle, aircraft, or ship. Figure 5 shows the case where the vehicle is a passenger car, but the vehicle is not limited to a passenger car and may be a truck, bus, trolleybus or other large vehicle, or a motorcycle. The position of the display device 100 is arbitrary within the mobile body 23. The display device 100 may be mounted as side mirrors 100L, 100R at both ends of the instrument panel 103, as shown in Figure 23 described later, or as a digital rearview mirror 100A on the ceiling 104 of the passenger compartment, or it may be mounted in the dashboard, on the A-pillar, etc. The display device 100 may share some of its components with other devices and parts provided by the mobile body 23.

[0039] As an example of this disclosure, a display system may be configured comprising a display device 100 and a camera 102 that captures the scenery around a moving object 23. Here, the scenery around the moving object 23 may be at least one of the front, rear, side, above, and below the moving object 23. The camera 102 may include, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The display device 100 and the camera 102 are connected by wired communication and / or wireless communication. If the moving object 23 is a vehicle, the display device 1 and the camera 102 may be connected via a vehicle network such as a CAN (Control Area Network).

[0040] The display device 100 may be configured to display at least a part of the captured image captured by the camera 102 on the display panel 2. In this case, the display device 100 can allow the user 22 (the driver of the moving body 23) to visually recognize the rear view of the moving body 23 as a virtual image V formed in front of the display device 100. As a result, since the reflected inverted image is removed from the virtual image V, the user 22 can clearly visually recognize the rear view of the moving body 23 while driving the moving body 23. Therefore, it becomes easier to visually recognize the virtual image V, and the driving safety can be improved. Further, since the display device 100 is a small display device, even if it is disposed in the driver's cab of the moving body 23, it does not occupy a large volume in the driver's cab and is unlikely to interfere with driving. The display device 100 mounted on the moving body 23 and configured to allow the user 22 to visually recognize the rear view of the moving body 23 as the virtual image V can constitute the side mirrors 一百L, 100R and the digital room mirror 100A described above.

[0041] The display device 100 may include a reflective optical element 101. The display device 100 may be configured such that the display device 1 emits display light toward the reflective optical element 101, and the reflective optical element 101 allows a part of the display light to reach the eyes of the user 22. When the display device 100 is mounted on the moving body 23, the display device 100 may also use the windshield 24 of the moving body 23 as the reflective optical element 101.

[0042] FIG. 6 is a front view showing a state in which a reflected inverted image is displayed on the display device, and FIG. 7 is an optical path diagram of the display light. When the semi-transparent mirror 6 is not tilted at a predetermined posture, that is, a predetermined tilt angle θ, the user 22 visually recognizes, as shown in FIG. 6, for example, a virtual image V in which a reflected inverted image V1 in which a part 22a of the face of the user 22 is inverted vertically is overlapped. It is considered that such a reflected inverted image V1 is visually recognized for the following reason. The light incident perpendicularly to the reflecting surface 6a of the semi-transparent mirror 6 travels toward the focal point Om. The light emitted from the focal point Om is reflected by the reflecting surface 6a of the semi-transparent mirror 6 and then travels perpendicularly to the reflecting surface 6a. Therefore, a part 22a of the face of the user 22, which is the background position, generates a reflected inverted image V1 as an inverted real image (intermediate image) by the semi-transparent mirror 6.

[0043] FIG. 8 is a diagram for explaining the generation position of the background real image. When a reflected inverted image V1 is generated as an inverted real image (intermediate image) on the optical axis L0 of the display surface 2a of the display panel 2 by the semi-transmissive mirror 6, a mirror image V2 is generated as an intermediate image behind the semi-transmissive mirror 6 by the reflective polarizing plate 8.

[0044] FIG. 9 is a diagram for explaining the generation position of the background real image. The light incident perpendicularly to the reflecting surface 6a of the semi-transmissive mirror 6 travels toward the focal point Om of the semi-transmissive mirror 6. The light incident on the reflecting surface 6a of the semi-transmissive mirror 6 is reflected by the reflecting surface 6a of the semi-transmissive mirror 6 and then travels perpendicularly to the semi-transmissive mirror 6. Therefore, a mirror image V3 is generated as an intermediate image by the reflective polarizing plate 8, and a real image of a reduced image V4 is generated by the mirror image V3 and the semi-transmissive mirror 6.

[0045] FIG. 10 is a diagram showing the configuration of a simulated display device used in the simulation of the display position of the reflected inverted image by the display device when viewed facing the semi-transmissive mirror, and FIG. 11 is a diagram showing the size of the virtual image formation region. In order to confirm the display positions of the display virtual image and the reflected inverted image when the semi-transmissive mirror 6 is tilted forward, a simulation was performed using a simulated display device 1A that simulated the display device 1. The simulated display device 1A used in the simulation includes a display panel 2A that emits linearly polarized display light, a reflective polarizing plate 8A that is located on the side of the display surface 2Aa of the display panel 2A, transmits polarized light having a polarization axis parallel to the polarization axis of the display light, and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light, and a semi-transmissive mirror 6A that is disposed between the display panel 2A and the reflective polarizing plate 8A and has a reflecting surface 6Aa located on the side of the reflective polarizing plate 8A. The display surface 2Aa of the display panel 2A is 4.1 inches. With the original image of the reflected inverted image displayed at 8.2 inches on the display surface 2Aa, the virtual image and the reflected inverted image were observed from a position at a distance B = 500 mm in the direction of the optical axis L0 from the semi-transmissive mirror 6A. The display original image of the reflected inverted image was assumed to be the size of a human face, and a background simulation panel 50 with X = ½0 mm, Y1 = 150 mm, and Y2 = 120 mm was used. Also, on the display panel 2A, the semi-transmissive mirror 6A was set in a state where the tilt angle θ was tilted forward by 6°.

[0046] Figure 12 shows the configuration of the simulated display device used in the simulation, Figure 13 shows the background image panel used in the simulation, and Figure 14 shows the display image used in the simulation. A simulation using the simulated display device 1A was performed to confirm the conditions under which the reflected inverted image can be excluded from the imaging region of the display light. The simulated display device 1A used in the simulation comprises a display panel 2A that simulates the display panel 2, a semi-transparent mirror 6A that simulates the semi-transparent mirror 6, and a reflective polarizing plate 8A that simulates the reflective polarizing plate 8.

[0047] Figure 14 shows a background image. As described above, the simulated display device 1A displayed the background image 51 shown in Figure 14 on the display panel 2A.

[0048] Figure 15A shows the display state when the display panel of the simulated display device used in the simulation is facing directly, Figure 15B shows the display state of the display panel when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 6°, and Figure 15C shows the display state of the display panel when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -6°. Figure 16A shows the display state of the virtual image when the semi-transparent mirror of the simulated display device used in the simulation is facing directly without tilting, Figure 16B shows the display state of the virtual image when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 6°, and Figure 16C shows the display state of the virtual image when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -6°.

[0049] When the semi-transparent mirror 6 was positioned in a straight, untilted position, the entire background image 51 was visible, as shown in Figure 15A. When the semi-transparent mirror 6 was positioned in a forward-tilted position at an inclination angle θ = 3°, the background image 51 moved to the upper region and the reflected inverted image 52 moved to the lower region, as shown in Figure 15B. Furthermore, when the semi-transparent mirror 6 was positioned in a backward-tilted position at an inclination angle θ = -3°, the background image 51 was displayed in the upper and central regions, and the reflected inverted image 52 was displayed in a narrow area of ​​the lower region, as shown in Figure 15C.

[0050] The image V50 of the background simulation panel 50 was displayed in the approximate center of the display area, as shown in Figure 16A, when the semi-transparent mirror 6 was positioned upright without tilting; when the semi-transparent mirror 6 was positioned tilted forward at an inclination angle θ = 3°, it was displayed in the upper area, as shown in Figure 16B; and when the semi-transparent mirror 6 was positioned tilted backward at an inclination angle θ = -3°, it was displayed in the lower area, as shown in Figure 16C.

[0051] Figure 17A shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is facing directly without tilting, Figure 17B shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 3°, and Figure 17C shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -3°. Figure 18A shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is facing directly without tilting, Figure 18B shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted forward at an inclination angle θ = 6°, and Figure 18C shows the display state of the simulated image when the semi-transparent mirror of the display device used in the simulation is tilted backward at an inclination angle θ = -6°.

[0052] When the semi-transparent mirror 6 is positioned directly in front, as shown in Figures 17A and 18A, the reflected inverted image V20 of ambient light cannot be separated from the virtual image V10 of the display light and are displayed superimposed. However, when the semi-transparent mirror 6 is tilted at an angle θ = 3°, as shown in Figure 17B, the reflected inverted image V20 of ambient light moves downward relative to the virtual image V10 of the display light. Furthermore, when the semi-transparent mirror 6 is tilted backward at an angle θ = -3°, as shown in Figure 16C, the reflected inverted image V20 of ambient light moves upward relative to the virtual image V10 of the display light. Furthermore, when the semi-transparent mirror 6 is positioned directly opposite the display light, as shown in Figure 18A, the reflected inverted image V20 of ambient light is superimposed on the virtual image V10 of the display light. However, when the semi-transparent mirror 6 is tilted forward at an inclination angle θ = 6°, as shown in Figure 18B, the reflected inverted image V20 of ambient light moves further upward relative to the virtual image V of the display light. When the semi-transparent mirror 6 is tilted backward at an inclination angle θ = -6°, as shown in Figure 18C, the reflected inverted image V20 of ambient light moves downward relative to the virtual image V10 of the display light. Therefore, by selecting an inclination angle θ of the semi-transparent mirror such that the reflected inverted image V20 of ambient light is excluded from the imaging region of the virtual image of the display light, the perception of the incident ambient light as a reflected inverted image can be reduced, thereby improving the display quality.

[0053] Figure 19 is a cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure, and Figure 20 is a front view of the display device of Figure 19. In Figure 19, the display unit 4, the first phase difference plate, and the second phase difference plate shown in Figure 2 are omitted. In this embodiment, the display device 1B is tilted to a second tilt angle θ1, and a light shield 30 is provided to remove at least a portion of the reflected inverted image that cannot be eliminated by the tilt of the semi-transparent mirror 6, and the other configurations are the same as those of the display device 1. That is, the display device 1B includes a display panel 2 that emits linearly polarized display light, a first quarter-wave plate 5 as a first phase difference plate located on the display surface 2Aa side of the display panel 2, a second quarter-wave plate 7 as a second phase difference plate located at a distance from the first quarter-wave plate 5, a reflective polarizing plate 8 located on the side of the second quarter-wave plate 7 opposite to the display panel 2, which transmits polarized light having a polarization axis parallel to the polarization axis of the display light and reflects polarized light having a polarization axis perpendicular to the polarization axis of the display light, a semi-transparent mirror 6 positioned between the first quarter-wave plate 5 and the second quarter-wave plate 7 and having a reflective surface 6a located on the side of the second quarter-wave plate 7, and arranged in a position tilted from a direct position at a second predetermined angle θ1, and a light shield 30 interposed in the incident path of external light to the reflective surface 6a of the semi-transparent mirror 6 that forms a reflected inverted image other than a virtual image of the display light. The orientation of the semi-transparent mirror 6 may be, for example, a forward tilt, a backward tilt, a rightward tilt, or a leftward tilt. The second predetermined angle θ1 may be the same as the predetermined angle θ described above, or it may be smaller than the predetermined angle θ.

[0054] In this embodiment, the light shield 30 may be arranged to cover at least a portion of the peripheral region of the surface of the reflective polarizing plate 8 opposite to the surface located on the side of the semi-transparent mirror 6, and may be located on at least a portion of the peripheral regions 8A1, 8A2, 8A3, 8A4 of the surface 8A of the reflective polarizing plate 8 downstream in the direction of light emission from the display panel 2 when viewed from the right in Figure 19. The peripheral regions 8A1, 8A2, 8A3, 8A4 may be, for example, the regions that overlap with the upper end, lower end, left end, and right end of the reflective polarizing plate 8 when viewed from the right in Figure 19. For example, when the posture of the semi-transparent mirror 6 is tilted forward or backward, the light shield 30 may be located on the peripheral region 8A1 or 8A2. For example, when the posture of the semi-transparent mirror 6 is tilted to the right or to the left, the light shield 30 may be located on the peripheral region 8A3 or 8A4. The material of the light-shielding body 30 can be any material that can block external light, for example, a black synthetic resin light-shielding plate. With such a light-shielding plate 30, at least a portion of the external light that cannot be removed even when the semi-transparent mirror 6 is tilted to the second tilt angle θ1 can be blocked by the light-shielding body 30, thereby reducing the occurrence of a reflected inverted image.

[0055] Figure 21 is a front view showing another modification of the display device shown in Figures 19 and 20. In the embodiments shown in Figures 19 and 20, the light-shielding body 30 is provided around the entire circumference of the peripheral regions 8A1, 8A2, 8A3, and 8A4 of the reflective polarizing plate 8. However, in other modifications, as shown in Figure 21, the light-shielding body 30a may be provided to shield only the area where the virtual image V10 of the display light is displayed and the reflected inverted image V20 is blocked, for example, the upper peripheral region 8A1 of the reflective polarizing plate as seen from the user 22. In yet another modification, the aforementioned light-shielding bodies 30 and 30a may be provided between the semi-transparent mirror 6 and the reflective polarizing plate 8.

[0056] In other embodiments of this disclosure, when the semi-transparent mirror 6 is positioned directly opposite the optical axis of the reflective surface 6a on the optical axis L0, the light-shielding area of ​​the aforementioned light-shielding body 30a can be enlarged to a position where no inverted reflected images are produced. In this case, since the semi-transparent mirror 6 is positioned directly opposite the optical axis, the dimensions of the display device 1B in the direction of the optical axis L0 can be reduced compared to when it is in an inclined position, and the display device 1B can be miniaturized.

[0057] Figure 22A is an exploded cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure, and Figure 22B is a cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure. The display device 1C of this embodiment comprises a display panel 2 and an optical system 10. The optical system 10 forms a virtual image V of the display light emitted from the display panel 2 within the field of view of the user 22. The optical system 10 may also be configured to form a real image of the display light within the field of view of the user 22. The optical system 10 may include a first semi-transparent mirror 11 which is a first reflective member, a first phase difference plate, a second semi-transparent mirror 13 which is a second reflective member, a second phase difference plate, and a polarizing plate 15. In this embodiment, the case in which a first quarter-wave plate 12 is used as the first phase difference plate and a second quarter-wave plate 14 is used as the second phase difference plate will be described. The first semi-transparent mirror 11, the first quarter-wave plate 12, the second semi-transparent mirror 13, the second quarter-wave 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.

[0058] The first quarter-wave plate 12 may be located on the side of the first reflective surface 11a of the first semi-transparent mirror 11. The first quarter-wave plate 12 may be located away from the display surface 2a in the direction of emission of display light from the display panel 2. The second quarter-wave plate 14 may be located away from the first quarter-wave plate 12 in the direction of emission of display light. At least one of the first semi-transparent mirror 11 and the second semi-transparent mirror 13 may be arranged in a predetermined orientation in which at least one of the first reflective surface 11a and the second reflective surface 13a is tilted from the frontal position by a predetermined tilt angle θ in the direction of reflecting the inverted image due to ambient light outside the imaging region of the virtual image V of the display light. The tilt angles of the first semi-transparent mirror 11 and the second semi-transparent mirror 13 may be the same or different. The tilt angle of the first semi-transparent mirror 11 may be greater than the tilt angle of the second semi-transparent mirror 13. The inclination angle of the first semi-transparent mirror 11 may be smaller than the inclination angle of the second semi-transparent mirror 13.

[0059] The first semi-transparent mirror 11 may be positioned between the display panel 2 and the first quarter-wave plate 12. The first semi-transparent mirror 11 may transmit a portion of the incident light and reflect the remainder. The first semi-transparent mirror 11 may have a function of focusing or converging light. Specifically, the first semi-transparent mirror 11 may have a function of focusing or converging light that is incident on and reflected by the first semi-transparent mirror 11. The first semi-transparent mirror 11 may be a concave mirror having a concave first reflective surface 11a, as shown in Figure 5. The first reflective surface 11a of the first semi-transparent mirror 11 may be positioned on the side of the first quarter-wave plate 12. The first semi-transparent mirror 11 may focus or converge light more effectively than other members of the optical system 10. In other words, the first semi-transparent mirror 11 may have a larger focusing degree, converging degree, or index expressed as the reciprocal of the focal length than other members of the optical system 10. The reflective surface 11a of the first semi-transparent mirror 11 may have a greater curvature than other members of the optical system 10. The optical system 10 may have only the first semi-transparent mirror 11 as a member having a light-gathering or focusing function. The first semi-transparent mirror 11 may also be composed of a holographic optical element (HOE), or its surface shape may have a Fresnel shape. In this embodiment, the first semi-transparent mirror 11 may be configured to transmit polarized light having a polarization axis parallel to the polarization axis of the display light and to reflect polarized light having a polarization axis perpendicular to the polarization axis of the display light. The first semi-transparent mirror 11 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. Alternatively, the first semi-transparent mirror 11 may be configured to reflect S-wave polarized light and transmit P-wave polarized light. At least a portion of the first reflective surface 11a of the first semi-transparent mirror 11 may include a spherical shape, an aspherical shape, or a free-form surface shape.

[0060] In the display device 1C of this embodiment, as shown in Figure 22B, the first quarter-wave plate 12, the second semi-transparent mirror 13, the second quarter-wave plate 14, and the polarizing plate 15 may be in surface contact with each other, or the first quarter-wave plate 12, the second semi-transparent mirror 13, the second quarter-wave plate 14, and the polarizing plate 15 may be bonded to each other with a light-transmitting adhesive.

[0061] The first semi-transparent mirror 11 may be composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal nanowires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The first semi-transparent mirror 11 can transmit light components vibrating in a direction perpendicular to the grid and can reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate on the side of the first phase difference plate 12. In this example, the metal nanowire grid is used to impart a reflective polarization function to the first semi-transparent mirror 11, but the first semi-transparent mirror 11 may be used as a simple half-mirror and a separate reflective polarizing plate may be provided.

[0062] The second semi-transparent mirror 13 may be positioned between the first quarter-wave plate 12 and the second quarter-wave plate 14. The second semi-transparent mirror 13 may transmit a portion of the incident light (for example, approximately 50%) and reflect the remainder (for example, approximately 50%). The transmittance and reflectance of the light incident on the second semi-transparent mirror 13 are not limited to 50%. The second semi-transparent mirror 13 may be positioned on the opposite side of the first semi-transparent mirror 11 from the first quarter-wave plate 12, and more specifically, as shown in Figure 5, the second reflective surface 13a may be positioned on the side of the first quarter-wave plate 12. The second semi-transparent mirror 13 may be a plane mirror. The second semi-transparent mirror 13 is also called a plane half-mirror.

[0063] The second semi-transparent mirror 13 may be composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent reflective layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film, etc.

[0064] The polarizing plate 15 may be located on the side of the second quarter-wave plate 14 opposite to the side of the second semi-transparent mirror 13. In other words, the polarizing plate 15 is located downstream of the second quarter-wave plate 14 in the direction of emission of display light from the display panel 2. The polarizing plate 15 may transmit a portion of the incident light and absorb or reflect the remainder. In this embodiment, the polarizing plate 15 may be configured to transmit P-wave polarized light and absorb S-wave polarized light. The polarizing plate 15 may be configured to absorb or reflect polarized light having a polarization axis parallel to the polarization axis of the display light (for example, S-wave polarized light, also called third polarization) and transmit polarized light having a polarization axis perpendicular to the polarization axis of the display light (for example, P-wave polarized light, also called fourth polarization). In this case, the positional relationship between the first quarter-wave plate 12 and the second quarter-wave plate 14 may be defined such that, when viewed along the Z-axis, the retard axis of the second quarter-wave plate 14 is perpendicular to the retard axis of the first quarter-wave plate 12. Furthermore, the polarizing plate 15 may be configured to absorb or reflect polarized light having a polarization axis perpendicular to the polarization axis of the displayed light, and to transmit polarized light having a polarization axis parallel to the polarization axis of the displayed light. In this case, the positional relationship between the first quarter-wave plate 12 and the second quarter-wave plate 14 may be defined such that, when viewed along the Z-axis, the retard axis of the second quarter-wave plate 14 is parallel to the retard axis of the first quarter-wave plate 12.

[0065] The polarizing plate 15 may have the configuration of a known absorption polarizing plate. Known absorption polarizing plates may be, for example, an iodine-based polarizing plate in which an iodine compound is adsorbed and oriented on a polyvinyl alcohol (PVA) film, or a dye-based polarizing plate in which a dichroic organic dye is adsorbed and oriented on a PVA film. Alternatively, the polarizing plate 15 may have the configuration of a reflective polarizing plate.

[0066] The optical function of the optical system 10 will now be described. The display light, which is S-wave polarized (first linearly polarized) light emitted from the display panel 2, passes through the first semi-transparent mirror 11. The display light of the first linearly polarized L1 passes through the first quarter-wave plate 12 and is converted into light of the first circularly polarized C1. The light of the first circularly polarized C1 is incident on the second semi-transparent mirror 13. A portion of the light of the first circularly polarized C1 (for example, approximately 50%) is reflected by the second semi-transparent mirror 13 and converted into light of the second circularly polarized C2. The light of the second circularly polarized C2 passes through the first quarter-wave plate 12 and is converted into light of the second linearly polarized L2, whose polarization direction is perpendicular to that of the first linearly polarized L1 (i.e., it is P-wave polarized). The light of the second linearly polarized L2 is reflected by the first semi-transparent mirror 11 and is converted into light of the third linearly polarized L3, whose polarization direction is perpendicular to that of the first linearly polarized L1. The third linearly polarized light L3 passes through the first quarter-wave plate 12 and is converted into the third circularly polarized light C3. A portion of the third circularly polarized light C3 (for example, approximately 50%) passes through the second semi-transparent mirror 13. The third circularly polarized light C3 that has passed through the second semi-transparent mirror 13 passes through the second quarter-wave plate 14 and is converted into the fourth linearly polarized light L4, whose polarization direction is perpendicular to the first linearly polarized light L1 (i.e., it is P-wave polarized). The fourth linearly polarized light L4 passes through the polarizer plate 15 and is emitted to the outside.

[0067] The remaining portion of the light from the first circularly polarized light C1 (for example, about 50%) passes through the second semi-transparent mirror 13, then through the second quarter-wave plate 14, and is converted into fifth linearly polarized light L5, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized light). The fifth linearly polarized light L5 is absorbed or reflected by the polarizer 15 and is therefore not emitted to the outside. In other words, the fifth linearly polarized light L5 is light that is not transmitted through the polarizer 15. Therefore, the amount of light (luminance) emitted from the display device 1A is, for example, about 25% of the amount of display light (luminance) emitted from the display panel 2.

[0068] The first quarter-wave plate 12 and the second quarter-wave plate 14 only need to be given the necessary phase difference to the display light transmitted through the first quarter-wave plate 12 and the second quarter-wave plate 14 so that the light transmitted through the first quarter-wave plate 12 and the second quarter-wave plate 14 is reflected by the first semi-reflecting mirror 11 and the second semi-reflecting mirror 13. For example, a phase difference of 1 / 4 wavelength is given to the polarization plane (polarization plane in the direction of electric field oscillation) of the incident light. As a result, a portion of the display light emitted from the display panel 2 can be reflected by the first semi-transparent mirror 11 and the second semi-transparent mirror 13 and transmitted through the second semi-transparent mirror 13. In the above example, the first and second phase difference plates are described as quarter-wave plates. However, the first and second phase difference plates may be other wave plates or combinations thereof, as long as some of the light is absorbed or reflected by the polarizer 15 and other light is transmitted through the polarizer 15. For example, the first and second phase difference plates should be designed to provide the necessary phase difference to the light transmitted through the first and second phase difference plates without being reflected by the second semi-transparent mirror 13, so that some of the light transmitted through the first and second phase difference plates without being reflected by the second semi-transparent mirror 13 is absorbed or reflected by the polarizer 15. That is, for example, if the polarization obtained by transmitting light through the first and second phase difference plates without being reflected by the second semi-transparent mirror 13 is defined as the third polarization, the first and second phase difference plates may be other wave plates or combinations thereof, as long as the third polarization is obtained. This disclosure will explain using the case where the first phase difference plate and the second phase difference plate are quarter-wave plates as an example. Furthermore, the first phase difference plate and the second phase difference plate only need to be able to provide the necessary phase difference to the light that is reflected by the second semi-transparent mirror 13 and the first semi-transparent mirror 11 and transmitted through the first phase difference plate and the second phase difference plate, so that the light that is reflected by the second semi-transparent mirror 13 and the first semi-transparent mirror 11 and transmitted through the first phase difference plate and the second phase difference plate is transmitted through the polarizing plate 15. That is, for example, if the polarization obtained by reflecting by the second semi-transparent mirror 13 and the first semi-transparent mirror 11 and transmitted through the first phase difference plate and the second phase difference plate is the fourth polarization, the first phase difference plate and the second phase difference plate may be other wavelength plates instead of quarter-wave plates, as long as the fourth polarization is obtained.Furthermore, the first and second phase difference plates may be other wave plates or combinations thereof, rather than quarter-wave plates, as long as some of the light is reflected by the first semi-transparent mirror 11 and the other light is transmitted through the first semi-transparent mirror 11. The first phase difference plate only needs to be able to provide the necessary phase difference to the light transmitted through the first phase difference plate so that the light transmitted through the first phase difference plate, reflected by the second semi-transparent mirror 13, and then transmitted through the first phase difference plate again is reflected by the first semi-transparent mirror 11. That is, for example, if the polarization obtained by transmitting light through the first phase difference plate, reflected by the second semi-transparent mirror 13, and then transmitted through the first phase difference plate again is taken as the fifth polarization, then the first phase difference plate and the fifth polarization can be other wave plates rather than quarter-wave plates, as long as they can be obtained. Also, the first and second phase difference plates may be film-like members.

[0069] Figure 23A is an exploded cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure, and Figure 23B is a cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure. The display device 1D of this embodiment comprises a display panel 2 and an optical system 10. The optical system 10 forms a virtual image V of the display light emitted from the display panel 2 within the field of view of the user 22. The optical system 10 may also be configured to form a real image of the display light within the field of view of the user 22. The optical system 10 may include a first semi-transparent mirror 11 which is a first reflective member, a first phase difference plate, a second semi-transparent mirror 131 which is a second reflective member, a second phase difference plate, and a polarizing plate 15. In this embodiment, the case in which a first quarter-wave plate 12 is used as the first phase difference plate and a second quarter-wave plate 14 is used as the second phase difference plate will be described. The first semi-transparent mirror 11, the first quarter-wave plate 12, the second semi-transparent mirror 131, the second quarter-wave 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. At least one of the first semi-transparent mirror 11 and the second semi-transparent mirror 131 may be positioned in a predetermined orientation in which at least one of the first reflective surface 11a and the second reflective surface 131a is tilted from the frontal position at a predetermined tilt angle θ with respect to the optical axis L0 of the display surface 2a, in a direction that reflects the reflected inverted image due to ambient light outside the imaging region of the virtual image of the display light. The tilt angles of the first semi-transparent mirror 11 and the second semi-transparent mirror 131 may be the same or different. The tilt angle of the first semi-transparent mirror 11 may be greater than the tilt angle of the second semi-transparent mirror 131. The tilt angle of the first semi-transparent mirror 11 may be smaller than the tilt angle of the second semi-transparent mirror 131.

[0070] As shown in Figure 23B, the display device 1D of this embodiment may have a configuration in which the first quarter-wave plate 12, the second semi-transparent mirror 131, the second quarter-wave plate 14, and the polarizing plate 15 are in surface contact with each other, or the first quarter-wave plate 12, the second semi-transparent mirror 131, the second quarter-wave plate 14, and the polarizing plate 15 are bonded to each other with a light-transmitting adhesive.

[0071] The second semi-transparent mirror 131 may have a function to diverge the light that is incident on and reflected by the second semi-transparent mirror 131. The second semi-transparent mirror 131 may have a convex reflective surface 131a, and the reflective surface 131a may be located on the side of the first quarter-wave plate 12. The second semi-transparent mirror 131 is also called a convex half-mirror. The second semi-transparent mirror 131 may transmit a portion of the incident light (for example, approximately 50%) and reflect the remainder (for example, approximately 50%). The second semi-transparent mirror 131 may have a function to collect or focus the light that is incident on and reflected by the second semi-transparent mirror 131. Specifically, the second semi-transparent mirror 13 may have a concave shape located on the display panel 2 side. Furthermore, the second semi-transparent mirror 131 may be composed of a holographic optical element (HOE), or its surface shape may have a Fresnel shape.

[0072] The second semi-transparent mirror 131 may be composed of, for example, a substrate and a semi-transparent reflective layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent reflective layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent reflective layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film, etc.

[0073] The optical system 10 may be configured such that the focal length of the second semi-transparent mirror 131 is greater than the distance between the display panel 2 and the second semi-transparent mirror 131. In other words, the optical system 10 may be configured such that the second semi-transparent mirror 131 forms a reduced mirror image V5 (see Figure 3) of the object (i.e., the display surface 2a). Furthermore, the optical system 10 may be configured such that the focal length of the first semi-transparent mirror 11 is greater than the distance between the mirror image V5 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 forms an enlarged virtual image V of the object (i.e., the mirror image V5). In this case, it becomes possible to adjust the magnification ratio and projection distance (virtual image distance) of the virtual image V while reducing the thickness of the optical system 10 in the depth direction (Z-axis direction).

[0074] The first semi-transparent mirror 11, the first quarter-wave plate 12, the second semi-transparent mirror 131, the second quarter-wave plate 14, and the polarizing plate 15 are held by a holding member (not shown) to maintain their relative positions. Air is interposed between the first semi-transparent mirror 11 and the first quarter-wave plate 12. Since the display device 1D does not have a member made of a resin material such as polymer between the first semi-transparent mirror 11 and the first quarter-wave plate 12, the risk of deformation of the first semi-transparent mirror 11 when the resin material is cured during the manufacturing process of the display device 1D, and misalignment between the first semi-transparent mirror 11 and the first quarter-wave plate 12 can be reduced. As a result, a decrease in display quality can be reduced.

[0075] Since the optical system 10 is an on-axis type optical system in which the optical axis of the incident light and the optical axis of the emitted light substantially coincide, the space occupied by the optical system 10 can be reduced, and as a result, the display device 1D can be miniaturized. In addition, because the optical system 10 is on-axis, distortion and brightness unevenness of the virtual image V seen by the user 22 can be reduced, and the design of the optical system 10 is simplified.

[0076] Figure 24A is an exploded cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure, and Figure 24B is a cross-sectional view showing the configuration of another embodiment of the display device of the present disclosure. The display device 1E of this embodiment includes a display panel 2 and an optical system 16. The optical system 16 forms a virtual image V of the display light emitted from the display panel 2 within the field of view of the user 22. The optical system 16 may also be configured to form a real image of the display light within the field of view of the user 22. The optical system 16 may include a first semi-transparent mirror 17 which is a first reflective member, a first phase difference plate, a second semi-transparent mirror 19, a second phase difference plate, and a third semi-transparent mirror 21 which is a second reflective member. In this embodiment, a case in which a first quarter-wave plate 18 is used as the first phase difference plate and a second quarter-wave plate 20 is used as the second phase difference plate will be described. The first semi-transparent mirror 17, the first quarter-wave plate 18, the second semi-transparent mirror 19, the second quarter-wave 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. At least one of the first semi-transparent mirror 17, the second semi-transparent mirror 19, and the third semi-transparent mirror 21 is positioned in a predetermined orientation in which at least one of the first reflective surface 17a, the second reflective surface 19a, the third reflective surface 19b, and the fourth reflective surface 21a is tilted from a frontal position at a predetermined inclination angle θ with respect to the optical axis L0 of the display surface 2a, in a direction that reflects the reflected inverted image due to ambient light outside the imaging region of the virtual image of the display light.

[0077] As shown in Figure 24B, the display device 1E of this embodiment may be configured such that the first quarter-wave plate 18, the second semi-transparent mirror 19, and the second quarter-wave plate 20 are in surface contact with each other, or the first quarter-wave plate 18, the second semi-transparent mirror 19, and the second quarter-wave plate 20 are bonded to each other with a light-transmitting adhesive.

[0078] The first quarter-wave plate 18 is located on the side of the first reflective surface 17a of the first semi-transparent mirror 17. The first quarter-wave plate 18 is located away from the display surface 2a in the direction of emission of display light from the display panel 2. The second quarter-wave plate 20 is located away from the first quarter-wave plate 12 in the direction of emission of display light.

[0079] The first semi-transparent mirror 17 may be positioned between the display panel 2 and the first quarter-wave 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. Alternatively, the first semi-transparent mirror 17 may be configured to reflect S-wave polarized light and transmit P-wave polarized light. As shown in Figure 9, the first semi-transparent mirror 17 may be a concave mirror having a concave first reflective surface 17a located on the side of the first quarter-wave plate 18. At least a portion of the first reflective surface 17a of the first semi-transparent mirror 17 may include a spherical shape, an aspherical shape, or a free-form surface shape.

[0080] The first semi-transparent mirror 17 is composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal nanowires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The first semi-transparent mirror 17 can transmit light components vibrating in a direction perpendicular to the grid and can reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate located on the side of the first phase difference plate 18. In this example, the metal nanowire grid provides the first semi-transparent mirror 11 with a reflective polarization function, but the first semi-transparent mirror 11 may be used as a simple half-mirror and a separate reflective polarizer may be provided.

[0081] The second semi-transparent mirror 19 may be positioned between the first quarter-wave plate 18 and the second quarter-wave plate 20. The second semi-transparent mirror 13 may transmit a portion of the incident light (for example, approximately 50%) and reflect the remainder (for example, approximately 50%). The second semi-transparent mirror 19 may be a plane mirror having a second reflective surface 19a located on the side of the first quarter-wave plate 18 and a third reflective surface 19b located on the side of the second quarter-wave plate 20, as shown in Figure 9. The second semi-transparent mirror 19 is also called a plane half-mirror.

[0082] The second semi-transparent mirror 19 may be composed of, for example, a substrate and a semi-transparent layer located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be made of, for example, inorganic glass, a resin material, etc. The resin material may be, for example, acrylic resin, polycarbonate resin, etc. The semi-transparent layer may be a thin metal film. The thin metal film may be made of, for example, a metal material such as aluminum or chromium. The semi-transparent layer is not limited to a thin metal film, and may be, for example, a dielectric multilayer film. The first quarter-wave plate 18 and the second quarter-wave plate 20 may be fixed to the second semi-transparent mirror 19 with an optically transparent adhesive such as OCA (Optically Clear Adhesive). The adhesive may be a material with low retardation.

[0083] The third semi-transparent mirror 21 may be located on the side of the second quarter-wave plate 20 opposite to the side of the second semi-transparent mirror 19. The third semi-transparent mirror 21 may be located downstream of the second quarter-wave plate 20 in the direction of emission of display light from the display panel 2. The third semi-transparent mirror 21 may transmit a portion of the incident light and reflect the remainder. In this embodiment, the third semi-transparent mirror 21 may be configured to reflect S-wave polarized light and transmit P-wave polarized light. Alternatively, the third semi-transparent mirror 21 may be configured to transmit S-wave polarized light and reflect P-wave polarized light. The third semi-transparent mirror 21 may be a concave mirror having a concave fourth reflective surface 21a located on the side of the second quarter-wave plate 20, as shown in Figure 9. The third semi-transparent mirror 21 may include a spherical shape, an aspherical shape, or a free-form shape in at least a portion of the fourth reflective surface 21a.

[0084] The third semi-transparent mirror 21 is composed of, for example, a substrate and a plurality of metal nanowires (metal nanowire grids) located on the surface of the substrate. The substrate may have a transmittance of 100% or close to 100% for light in the visible light band. The substrate may be composed of, for example, a resin material, a glass material, etc. The resin material may be, for example, an acrylic resin, a polycarbonate resin, etc. The metal nanowires may be composed of, for example, a metal material such as aluminum, chromium, or titanium oxide. The metal nanowires may be arranged along one direction. The third semi-transparent mirror 21 can transmit light components vibrating in a direction perpendicular to the grid and can reflect light components vibrating in a direction parallel to the grid. The metal nanowire grid may be formed on the surface of the substrate located on the side of the second phase difference plate 20. In this example, the metal nanowire grid is used to impart a reflective polarization function to the third semi-transparent mirror 21, but the third semi-transparent mirror 21 may be used as a simple half-mirror and a separate reflective polarizer may be provided.

[0085] The optical function of the optical system 16 will now be described. In the display device 1B, the display light emitted from the display panel 2 may travel along path P1 or path P2 and be emitted to the outside. First, the light traveling along path P1 will be described. The S-wave polarized (first linearly polarized L1) display light emitted from the display panel 2 passes through the first semi-transparent mirror 17. The light of the first linearly polarized L1 passes through the first quarter-wave plate 18 and is converted into light of the first circularly polarized C1. The light of the first circularly polarized C1 is incident on the second semi-transparent mirror 19. A portion of the light of the first circularly polarized C1 (for example, approximately 50%) is reflected by the second semi-transparent mirror 19 and converted into light of the second circularly polarized C2. The light of the second circularly polarized C2 passes through the first quarter-wave plate 18 and is converted into light of the second linearly polarized L2, whose polarization direction is perpendicular to that of the first linearly polarized L1 (i.e., P-wave polarized). The light of the second linear polarization L2 is reflected by the first semi-transparent mirror 17 and converted into light of the third linear polarization L3, whose polarization direction is perpendicular to that of the first linear polarization L1 (i.e., it is P-wave polarized). The third linear polarization L3 is transmitted through the first quarter-wave plate 18 and converted into light of the third circular polarization C3. The light of the third circular polarization C3 is incident on the second semi-transparent mirror 19. A portion of the light of the third circular polarization C3 (for example, approximately 50%) is transmitted through the second semi-transparent mirror 19. The light of the third circular polarization C3 that has been transmitted through the second semi-transparent mirror 19 is transmitted through the second quarter-wave plate 20 and converted into light of the fourth linear polarization L4, whose polarization direction is perpendicular to that of the first linear polarization L1 (i.e., it is P-wave polarized). The light of the fourth linear polarization L4 is transmitted through the third semi-transparent mirror 21 and emitted to the outside.

[0086] Next, we will describe the light traveling along path P2. The remainder (for example, approximately 50%) of the first circularly polarized light C1 incident on the second semi-transparent mirror 19 passes through the second semi-transparent mirror 19. The first circularly polarized light C1 that has passed through the second semi-transparent mirror 19 passes through the second quarter-wave plate 20 and is converted into fifth linearly polarized light L5, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized light). The fifth linearly polarized light L5 is reflected by the third semi-transparent mirror 21 and is converted into sixth linearly polarized light L6, whose polarization direction is parallel to the first linearly polarized light L1 (i.e., S-wave polarized light). The sixth linearly polarized light L6 passes through the second quarter-wave plate 20 and is converted into fourth circularly polarized light C4. The fourth circularly polarized light C4 is incident on the second semi-transparent mirror 19. A portion of the light from the fourth circularly polarized light C4 (for example, approximately 50%) is reflected by the second semi-transparent mirror 19 and converted into the fifth circularly polarized light C5. The fifth circularly polarized light C5 passes through the second quarter-wave plate 20 and is converted into the seventh linearly polarized light L7, whose polarization direction is perpendicular to the first linearly polarized light L1 (i.e., it is P-wave polarized). The seventh linearly polarized light L7 passes through the third semi-transparent mirror 21 and is emitted to the outside.

[0087] At least one of the first semi-transparent mirror 17, the second semi-transparent mirror 19, and the third semi-transparent mirror 21 is positioned in a predetermined orientation such that at least one of its first reflective surface 17a, second reflective surface 19a, third reflective surface 19b, and fourth reflective surface 21a is oriented in a direction that reflects the inverted image reflected by ambient light away from the imaging region of the virtual image of the display light.

[0088] The first quarter-wave plate 18 and the second quarter-wave plate 20 are designed to provide the necessary phase difference to the display light transmitted through them, such that the light transmitted through them is reflected by the first semi-transparent mirror 17, the second semi-transparent mirror 19, and the third semi-transparent mirror 21. For example, a phase difference of 1 / 4 wavelength is given to the polarization plane (the polarization plane in the direction of electric field oscillation) of the incident light. This allows a portion of the display light emitted from the display panel 2 to be reflected by the first semi-transparent mirror 17 and the second semi-transparent mirror 19, transmitted through the second semi-transparent mirror 19, reflected again by the third semi-transparent mirror 21, and transmitted through the third semi-transparent mirror 21. Furthermore, the first and second phase difference plates can be configured such that light transmitted through the first and second phase difference plates is reflected by the first and second semi-transparent mirrors 17 and 19, transmitted through the second semi-transparent mirror 19, and then reflected and transmitted again by the third semi-transparent mirror 21, thereby providing a phase difference. Such phase difference plates are not limited to quarter-wave plates, but may be other wave plates or combinations thereof.

[0089] As described above, in the display device 1B, the display light emitted from the display panel 2 travels along path P1 or path P2 and is emitted to the outside. As a result, the amount of light emitted from the display device 1B is, for example, approximately 50% of the amount of display light emitted from the display panel 2. The display device 1B can improve light utilization efficiency and increase the brightness of the light emitted to the outside.

[0090] Figure 25 shows the interior of a vehicle equipped with a display device. As previously mentioned, the display devices 1, 1B to 1E may be implemented as side mirrors 100L and 100R on both the left and right sides of the instrument panel 103 of the mobile body 23, or as a digital rearview mirror 100A on the ceiling 104 of the passenger compartment. The side mirrors 100L and 100R are electronic side mirrors that display images of the rear view captured by the camera 102. These side mirrors 100L and 100R and the digital rearview mirror 100A do not display a reflected inverted image of the user 22, etc., but only a virtual image of the display light of the display panel 2, so the user 22 can recognize a virtual image with high display quality and excellent visibility. Furthermore, the display devices 1, 1B to 1E of this disclosure are not limited to the aforementioned side mirrors 100L, 100R and digital rearview mirror 100A, but can also be applied to the cluster 105, CID (Center Information Display) 106, PID (Passenger Information Display) 107, and can even be applied to RSE (Rear Seat Entertainment) for rear-seat passengers.

[0091] In yet another embodiment of this disclosure, the display device 1 may be configured as shown in Figure 2, comprising a display panel 2, an irradiator 4, an optical system 3, and a housing 36 that houses the display panel 2, the irradiator 4, and the optical system 3. The housing 36 may have a viewing section that allows the inside of the housing 36 to be seen from the outside of the housing 36. The housing 36 may have a viewing section that allows the inside of the housing 36 to be seen from the outside of the housing 36. The housing 36 has a window (opening) 37 that transmits light emitted from the optical system 3. The window (opening) 37 may function as a viewing section. The display device 1 may be arranged such that the window 37 and the display panel 2 overlap when the window 37 of the housing 36 is viewed. The housing 36 may have a member that allows the inside of the housing 36 located in the window (opening) 37 to be seen from the outside of the housing 36. The housing 36 may have a member that allows the inside of the housing 36 located in the window (opening) 37 to be seen from the outside of the housing 36. The housing 36 may have a light-transmitting plate positioned in the window 37 (opening). The light-transmitting plate may transmit light emitted from the optical system 3. The light-transmitting plate may at least partially block the window (opening) 37. The light-transmitting plate may be made of, for example, glass, resin, etc. A component (e.g., a light-transmitting plate) positioned in the window (opening) 37 that makes the inside of the housing 36 visible from the outside of the housing 36 may function as a viewing component. A component (e.g., a light-transmitting plate) positioned in the window (opening) 37 that makes the inside of the housing 36 visible from the outside of the housing 36 may function as a viewing component. Furthermore, the display device 1 may be positioned such that the window 37 and the optical system 3 overlap when the window 37 of the housing 36 is viewed. The virtual image V may be formed inside the housing 36 or outside the housing. The virtual image V may be formed on the side farther from the display panel 2 or on the side closer to the display panel 2, as viewed from the user 22. The virtual image V may be formed on the side farther from the window 37 as seen by the user 22, or on the side closer to the window.

[0092] The display device 1 may be configured to direct the display light emitted from the display panel 2 into the eyes of the user 22, allowing the user 22 to perceive it as a real image. The real image may be formed closer to the user 22 than the display device 1. The real image may be formed inside the housing 36 or outside the housing 36. The real image may be formed further away from the user 22 than the display panel 2 or closer to the display panel 2. The real image may be formed further away from the user 22 than the window 37 or closer to the window 37. When the image is formed inside the housing, the optical systems 3, 10, and 16 are capable of forming the image so that it can be viewed through the window. In other words, the image can be viewed by looking through the window. To put it another way, the image cannot be viewed without the window.

[0093] In the other embodiments of the display devices 1B, 1C, 1D, and 1E, the display panel 2, illuminator 4, and optical systems 3, 10, and 16 may be housed in the housing 36, just as in the display device 1 described above.

[0094] Although embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments described above.

[0095] For example, the above describes a display device equipped with a display panel, but is not limited to this. For example, this disclosure may describe a device without a display panel that is equipped with an optical system. For example, the housing of a display device may be equipped with a display panel mounting section. The display panel mounting section may be capable of mounting a display panel. The display panel mounting section may be located on a part of the wall surface of the housing, on the inside of the housing, or inside the housing. In this case, the display panel may be located on the inside of the housing or inside the housing. Also, the display panel mounting section may be located on the outside of the housing or outside the housing. That is, the display panel may be located on the outside of the housing or outside the housing. In this case, the housing may have an opening in which a part of the wall surface is cut out. The display panel mounting section may be positioned relative to the housing such that display light emitted from the display panel installed in the display panel mounting section is guided to the inside of the housing through the opening. The display panel mounting section may be positioned relative to the housing such that display light emitted from the display panel installed in the display panel mounting section is guided to the inside of the housing through the opening. The display panel mounting section may be connected to the outer wall of the housing, or it may be connected to the outer wall of the housing in such a way that it closes at least a part of the opening. A light-transmitting member may be placed in the opening, and this member may be, for example, glass or resin. For example, Figure 2A shows a display device in which a display panel is installed in the display panel mounting section, but it may also be a device in which a display panel is not installed in the display panel mounting section. In this case, the device may be a display panel housing device having a housing that includes a viewing section, an optical system, and a display panel mounting section on which a display panel can be installed. The display panel housing device may also realize the configuration of the display device of each embodiment described above. That is, the position of the display panel mounting section of the display panel housing device may be defined so that when a display panel is installed in the display panel mounting section, it becomes the configuration of each embodiment described above. Furthermore, the housing of the display panel housing device may have an opening, and the display panel may be insertable through the opening.In this case, the display panel housing may have the same configuration as the display device, except that the housing has an opening and the display panel can be inserted from the outside or from the outside.

[0096] For example, referring to Figure 2A, a display device 1 that lacks a display panel 2 can be interpreted as a display panel housing device of the present disclosure. In other words, the display device 1 can be interpreted as comprising a display panel 2 and a display panel housing device of the present disclosure.

[0097] The inventions described in this disclosure have been explained above based on the drawings and embodiments. However, the inventions described in this disclosure are not limited to the embodiments described above. That is, the inventions described in this disclosure can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described in this disclosure. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure.

[0098] The display device according to this disclosure can reduce reflected inverted images caused by incident ambient light and improve display quality.

[0099] This disclosure can be implemented in the following configuration.

[0100] (1) A display device comprising: a display panel having a display surface that emits display light; a display side of the display panel located on the side of the display surface; and a reflective member having a reflective surface located on the opposite side of the display side, wherein the reflective member is arranged in a position in which the reflective surface is inclined with respect to the optical axis of the display light.

[0101] (2) The display device according to configuration (1), wherein the posture is a forward-tilted posture obtained by angular displacement from the frontal position around a first axis perpendicular to the optical axis of the display light.

[0102] (3) The display device according to configuration (1), wherein the orientation is a backward tilted orientation obtained by angular displacement from the frontal position around a first axis perpendicular to the optical axis of the display light.

[0103] (4) The display device according to configuration (1), wherein the orientation is an inclined orientation obtained by angularly displacing the display light from a frontal position around a second axis perpendicular to the optical axis of the display light and a first axis perpendicular to the optical axis.

[0104] (5) The display device according to any one of the above configurations (1) to (4), wherein the angle of inclination is 5° or more and 7° or less.

[0105] (6) The display device according to configuration (1) above, wherein, with respect to the optical center of the reflective member, the portion of the reflective member closer to the display panel is designated as the first portion, and the portion of the reflective member other than the first portion is designated as the second portion, the curvature of the second portion is greater than the curvature of the first portion.

[0106] (7) The display device according to configuration (6), wherein, of the second portion, the portion closer to the optical center is designated as the third portion, and the portion further from the optical center than the third portion is designated as the fourth portion, the curvature of the fourth portion is greater than the curvature of the third portion.

[0107] (8) The display device according to configuration (1), further comprising a light-shielding body interposed in the incident path of ambient light that forms a reflected inverted image.

[0108] (9) The display device according to configuration (1) above, comprising: a first phase difference plate located on the side of the display surface of the display panel; a second phase difference plate located on the opposite side of the display panel from the first phase difference plate; a semitransparent mirror having a reflective surface disposed between the first phase difference plate and the second phase difference plate and located on the side of the second phase difference plate; and a reflective polarizer located on the side of the second phase difference plate that transmits first polarized light and reflects second polarized light, wherein the first phase difference plate and the second phase difference plate make the display light first polarized and second polarized.

[0109] (10) The display device according to configuration (1), comprising: a first phase difference plate located on the side of the display surface of the display panel; a second phase difference plate located on the opposite side of the display panel from the first phase difference plate; a first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface located on the side of the first phase difference plate; a second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate and having a second reflective surface located on the side of the first phase difference plate; and a polarizing plate located on the opposite side of the display panel from the second phase difference plate and on the side of the second phase difference plate, wherein the first phase difference plate and the second phase difference plate convert the display light into a first polarization that is transmitted through the polarizing plate and a second polarization that is transmitted less through the polarizing plate than the first polarization, and the first semi-transparent mirror and the second semi-transparent mirror are arranged in a position in which the first reflective surface and the second reflective surface are inclined with respect to the optical axis of the display light.

[0110] (11) The display device according to configuration (1) above, comprising: a first phase difference plate that transmits the display light; a second phase difference plate located on the opposite side of the first phase difference plate from the display panel; a first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface located on the side of the first phase difference plate; a second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate and having a second reflective surface located on the side of the first phase difference plate and a third reflective surface located on the side of the second phase difference plate; and a third semi-transparent mirror located on the opposite side of the second phase difference plate from the display panel and having a fourth reflective surface located on the side of the second phase difference plate, wherein the first semi-transparent mirror, the second semi-transparent mirror, and the third semi-transparent mirror are arranged in a position in which the first reflective surface, the second reflective surface, the third reflective surface, and the fourth reflective surface are inclined with respect to the optical axis of the display light.

[0111] (12) A display device comprising: a display panel having a display surface that emits display light; an optical system that forms an image of the display light emitted from the display panel; and a housing that houses the display panel and the optical system, wherein the optical system has at least one reflective member having a reflective surface; the housing has a viewing section that transmits light emitted from the optical system; the housing is arranged such that the viewing section, the optical system, and the display panel overlap when the viewing section of the housing is viewed; and the reflective member is arranged in a position in which the reflective surface is inclined with respect to the optical axis of the display light.

[0112] (13) The display device according to the above configuration (12), wherein the normal direction of the reflective member is different from the normal direction of the viewing portion.

[0113] (14) The display device according to any one of the above configurations (1) to (13), further comprising an irradiator that irradiates light onto the side of the display panel opposite to the display surface.

[0114] (16) A mobile body equipped with the display device described in any one of the above configurations (1) to (14).

[0115] (17) A display system comprising a display device according to any one of the above configurations (1) to (14), and a camera capable of communicating with the display device, wherein the display panel displays an image captured by the camera.

[0116] (18) A mobile body comprising the display system described in the above configuration (17).

[0117] (19) A display panel housing device comprising: a display panel mounting section capable of installing a display panel having a display surface that emits display light; a display side located on the side of the display surface of the display panel; and a reflective member having a reflective surface located on the opposite side from the display side, wherein the reflective member is arranged in a position in which the reflective surface is inclined with respect to the optical axis of the display light.

[0118] Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the gist of this disclosure. It goes without saying that all or part of each of the above embodiments can be combined as appropriate and in a non-contradictory manner.

[0119] 1, 1B, 1C, 1D, 1E Display device 2 Display panel 2a Display surface 4 Irradiator 5, 12, 18 First quarter-wave plate 6 Semi-transparent mirror 6a Reflecting surface 7, 14, 20 Second quarter-wave plate 8 Reflective polarizer 11 First semi-transparent mirror 22 User 22L Left eye 22R Right eye 23 Moving body 24 Windshield 30 Light shield 100 Display device 101 Reflective optical element 102 Camera

Claims

1. A display device comprising: a display panel having a display surface that emits display light; a display side of the display panel located on the side of the display surface; and a reflective member having a reflective surface located on the opposite side of the display side, wherein the reflective member is arranged in a position in which the reflective surface is inclined with respect to the optical axis of the display light.

2. The display device according to claim 1, wherein the posture is a forward-tilted posture that is angularly displaced from a frontal position around a first axis perpendicular to the optical axis of the display light.

3. The display device according to claim 1, wherein the posture is a backward tilt posture obtained by angularly displacing the frontal position around a first axis perpendicular to the optical axis of the display light.

4. The display device according to claim 1, wherein the orientation is an inclined orientation obtained by angularly displacing the display light from a frontal position around a second axis perpendicular to the optical axis of the display light and a first axis perpendicular to the optical axis.

5. The display device according to any one of claims 1 to 4, wherein the angle of inclination is 5° or more and 7° or less.

6. The display device according to claim 1, wherein, with respect to the optical center of the reflective member, the portion of the reflective member closer to the display panel is designated as the first portion, and the portion of the reflective member other than the first portion is designated as the second portion, the curvature of the second portion is greater than the curvature of the first portion.

7. The display device according to claim 6, wherein, of the second portion, the portion closer to the optical center is designated as the third portion, and the portion further from the optical center than the third portion is designated as the fourth portion, the curvature of the fourth portion is greater than the curvature of the third portion.

8. The display device according to claim 1, comprising a light-shielding body interposed in the incident path of ambient light that forms a reflected inverted image.

9. The display device according to claim 1, comprising: a first phase difference plate located on the side of the display surface of the display panel; a second phase difference plate located on the opposite side of the display panel from the first phase difference plate; a semi-transparent mirror having a reflective surface disposed between the first phase difference plate and the second phase difference plate and located on the side of the second phase difference plate; and a reflective polarizer located on the side of the second phase difference plate that transmits first polarized light and reflects second polarized light, wherein the first phase difference plate and the second phase difference plate make the display light first polarized and second polarized.

10. The display device according to claim 1, comprising: a first phase difference plate located on the side of the display surface of the display panel; a second phase difference plate located on the opposite side of the display panel from the first phase difference plate; a first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface located on the side of the first phase difference plate; a second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate and having a second reflective surface located on the side of the first phase difference plate; and a polarizing plate located on the opposite side of the display panel from the second phase difference plate and on the side of the second phase difference plate, wherein the first phase difference plate and the second phase difference plate convert the display light into a first polarization that is transmitted through the polarizing plate and a second polarization that is transmitted less through the polarizing plate than the first polarization, and the first semi-transparent mirror and the second semi-transparent mirror are arranged in a position in which the first reflective surface and the second reflective surface are inclined with respect to the optical axis of the display light.

11. The display device according to claim 1, comprising: a first phase difference plate that transmits the display light; a second phase difference plate located on the opposite side of the first phase difference plate from the display panel; a first semi-transparent mirror disposed between the display panel and the first phase difference plate and having a first reflective surface located on the side of the first phase difference plate; a second semi-transparent mirror disposed between the first phase difference plate and the second phase difference plate and having a second reflective surface located on the side of the first phase difference plate and a third reflective surface located on the side of the second phase difference plate; and a third semi-transparent mirror located on the opposite side of the second phase difference plate from the display panel and on the side of the second phase difference plate, wherein the first semi-transparent mirror, the second semi-transparent mirror, and the third semi-transparent mirror are arranged in a position in which the first reflective surface, the second reflective surface, the third reflective surface, and the fourth reflective surface are inclined with respect to the optical axis of the display light.

12. A display device comprising: a display panel having a display surface that emits display light; an optical system that forms an image of the display light emitted from the display panel; and a housing that houses the display panel and the optical system, wherein the optical system has at least one reflective member having a reflective surface; the housing has a viewing section that transmits light emitted from the optical system; the housing is arranged such that the viewing section, the optical system, and the display panel overlap when the viewing section of the housing is viewed; and the reflective member is arranged in a position in which the reflective surface is inclined with respect to the optical axis of the display light.

13. The display device according to claim 12, wherein the normal direction of the reflective member is different from the normal direction of the viewing portion.

14. The display device according to any one of claims 1 to 13, further comprising an irradiator for irradiating light onto the surface of the display panel opposite to the display surface.

15. A mobile body comprising the display device described in any one of claims 1 to 14.

16. A display system comprising a display device according to any one of claims 1 to 14, and a camera capable of communicating with the display device, wherein the display panel displays an image captured by the camera.

17. A mobile body comprising the display system described in claim 16.

18. A display panel housing device comprising: a display panel mounting section capable of installing a display panel having a display surface that emits display light; a display side located on the side of the display surface of the display panel; and a reflective member having a reflective surface located on the opposite side from the display side, wherein the reflective member is arranged in a position in which the reflective surface is inclined with respect to the optical axis of the display light.

Images