Projection device

Abstract

The projection device according to an embodiment of the present disclosure includes: a display device; a reflector that reflects light emitted from the display device to a predetermined direction; and a retroreflector plate that reflects light incident thereon via the reflector at a predetermined offset angle given relative to the incident direction.

Description

Technical Field

[0001] This disclosure relates to projection devices, for example, used as head-up displays. Background Technology

[0002] For example, Patent Document 1 discloses an information display device using a reflector comprising multiple unit areas arranged two-dimensionally on a main surface, thereby aiming to reduce restrictions on the installation location.

[0003] Reference List

[0004] Patent documents

[0005] Patent Document 1: WO 2018 / 061444 Summary of the Invention

[0006] Incidentally, projection devices that display driver assistance information for vehicle drivers are required to display virtual images with a wide field of view.

[0007] The goal is to provide a projection device capable of displaying virtual images with a wide field of view.

[0008] A projection device according to one embodiment of the present disclosure includes: a display device; a reflector that reflects light output from the display device in a predetermined direction; and a retroreflector that reflects light at a predetermined offset angle relative to the incident direction, the light entering via the reflector.

[0009] In a projection device according to one embodiment of the present disclosure, light emitted from a display device is emitted in a desired direction by using a retroreflector plate that reflects light at a predetermined offset angle relative to the incident direction. According to this configuration, for example, a wide-viewing-angle virtual image can be depicted without using a large mirror optical system. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating a configuration example of a projection device according to one embodiment of the present disclosure.

[0011] Figure 2 It is shown Figure 1 The diagram shows a functional block diagram of the configuration of the display device.

[0012] Figure 3 yes Figure 1 A schematic plan view of the special retroreflector shown.

[0013] Figure 4 It is used to describe the composition Figure 3 The diagram shows the retroreflection element of a special retroreflector.

[0014] Figure 5 It is along Figure 3A cross-sectional schematic diagram of an example configuration of a special retroreflector intercepted by the I-I' line shown.

[0015] Figure 6 It is used to describe through Figure 1 The diagram illustrates how a special retroreflector reflects a beam of light.

[0016] Figure 7A It is along Figure 3 A cross-sectional schematic diagram of another example of the configuration of a special retroreflector intercepted by the I-I' line is shown in the figure.

[0017] Figure 7B It is along Figure 3 A cross-sectional schematic diagram of another example of the configuration of a special retroreflector intercepted by the I-I' line is shown in the figure.

[0018] Figure 8 It is a diagram of the incident light vector (A), the reflected light vector (B), and the difference vector (C).

[0019] Figure 9 This is a diagram showing the axial rotation amount.

[0020] Figure 10 This is a diagram showing the relationship between the tilted surface of a corner reflector, the incident light vector, and the reflected light vector.

[0021] Figure 11A It is a diagram used to describe the pupil position in a visually recognizable wide-angle image.

[0022] Figure 11B It is used to describe in Figure 11A The diagram in the middle illustrates how each ray of light enters a person's eye.

[0023] Figure 12 It is a diagram used to describe the retroreflection position at a specific retroreflector according to a comparative example.

[0024] Figure 13 It is a diagram used to describe the retroreflection position of the beam at each viewing angle at a special retroreflector according to the comparative example.

[0025] Figure 14 It is used to describe Figure 1 The diagram shows the in-plane configuration of a special retroreflector.

[0026] Figure 15A It is set in Figure 14 A perspective view of the retroreflecting element at position A shown in the diagram.

[0027] Figure 15B It is set in Figure 14 A perspective view of the retroreflective element at point B shown.

[0028] Figure 15C It is arranged in Figure 14 A perspective view of the retroreflecting element at position C shown in the diagram.

[0029] Figure 16 It is used to describe Figure 1 The diagram shows the retroreflection position of the special retroreflector.

[0030] Figure 17 It is used to describe the beam in Figure 1 The diagram shows the retroreflection position at each viewpoint on the special retroreflector shown.

[0031] Figure 18 Is Figure 1 A schematic diagram illustrating an example configuration of a display device in a projection apparatus.

[0032] Figure 19 yes Figure 1 A schematic diagram illustrating another example of the configuration of the display device in the projection device shown.

[0033] Figure 20 This is a perspective view of an example configuration of the pupil copying device.

[0034] Figure 21 This is a diagram used to describe the pupil replication mechanism in the X-axis direction.

[0035] Figure 22 It is a diagram used to describe the compensation relationship between diffraction and wavelength dispersion.

[0036] Figure 23 This is a diagram illustrating the mechanism of pupil replication in the Y-axis direction.

[0037] Figure 24 This is a diagram used to describe a special retroreflector according to a first variation of the present disclosure.

[0038] Figure 25A It is set in Figure 24 A perspective view of the retroreflective element at region A shown.

[0039] Figure 25B It is set in Figure 24 A perspective view of the retroreflective element in region B shown.

[0040] Figure 25C It is set in Figure 24 A perspective view of the retroreflective element at region C shown.

[0041] Figure 26 It is used to describe the beam in Figure 24 The diagram shows the retroreflection position at each viewpoint of the special retroreflector.

[0042] Figure 27 This is a schematic diagram used to describe a special retroreflector according to a second modification of this disclosure.

[0043] Figure 28 This is a schematic diagram used to describe a special retroreflector according to a third variation of this disclosure.

[0044] Figure 29 This is a schematic diagram illustrating an example configuration of a projection device according to a fourth variation of this disclosure.

[0045] Figure 30 This is a schematic diagram of another example of the configuration of a projection device according to the fourth variation of this disclosure.

[0046] Figure 31 This is a schematic diagram illustrating an example configuration of a projection device according to a fifth variation of this disclosure.

[0047] Figure 32 This is an illustration of an example used to describe a combination of pupil replication and pupil tracking technologies.

[0048] Figure 33 This is a schematic diagram illustrating an example configuration of the pupil replication apparatus according to the sixth variation of this disclosure.

[0049] Figure 34 It shows the entry Figure 33 A diagram illustrating the state of light in the pupil replication device shown. Detailed Implementation

[0050] Embodiments according to this disclosure will now be described in detail with reference to the accompanying drawings. The following description provides only one specific example of this disclosure and is not intended to limit the scope of the following exemplary embodiments. Furthermore, this disclosure is not limited to the arrangement, dimensions, aspect ratios, etc., of the various components shown in the drawings. It should be noted that the description will be presented in the following order.

[0051] 1. Implementation method (example of a projection device using a special retroreflector plate)

[0052] 2. Variations

[0053] 2-1. First variant example (another example of a retroreflector)

[0054] 2-2. Second variation (another example of a retroreflector)

[0055] 2-3. Third variation (another example of a retroreflector)

[0056] 2-4. Fourth Variation (Another Example of a Projection Device)

[0057] 2-5. Fifth Variation (Another Example of a Projection Device)

[0058] 2-6. Sixth Variation (Another Example of a Pupil Replication Device)

[0059] <1. Implementation Method>

[0060] Figure 1 An example configuration of a projection device (projection device 1) according to one embodiment of the present disclosure is shown. Projection device 1 is used, for example, to display speed, navigation, etc., to the driver at the front seat of a vehicle. Projection device 1 is used in a head-up display (HUD) system that uses light reflection from the windshield to display virtual images including driver support information or attention information.

[0061] (Configuration of projection equipment)

[0062] The projection device 1 includes a display device 10, a reflector 20, and a special retroreflector 30. The special retroreflector 30 reflects the light entering through the reflector 20 at a predetermined offset angle relative to the incident direction.

[0063] Here, display device 10 corresponds to a specific example of a "display device" according to an exemplary embodiment of the present disclosure. Reflector 20 corresponds to a specific example of a "reflector" according to an exemplary embodiment of the present disclosure. Special retroreflector 30 corresponds to a specific example of a "retroreflector plate" according to an exemplary embodiment of the present disclosure.

[0064] Figure 2 This is a functional block diagram illustrating the configuration of display device 10. Display device 10 projects virtual images in front of observer 100. For example, display device 10 is coupled to a computer (such as a PC not shown) or an external image supply device (such as various types of image players) via an I / F (interface) and projects virtual images based on image signals input to that interface.

[0065] The display device 10 includes, for example, a light source device 11, a controller 12, a light source driver 13, a light modulation device 14, an image processing unit 15, a frame memory 16, a panel driver 17, a projection optical system driver 18, and a projection optical system 19.

[0066] Although not specifically illustrated, the light source device 11 includes a light source driver for driving the light sources and a current value setting unit for setting the current values ​​when driving the light sources. The light source driver, in sync with a signal input from the light source driving unit 13, generates a current with the current value set by the current value setting unit based on a power supply from a power supply circuit (not shown in the figures). The generated current is supplied to each light source.

[0067] The controller 12 controls the light source drive unit 13, the image processing unit 15, the panel drive unit 17, and the projection optical system drive unit 18.

[0068] The light source drive unit 13 outputs a signal for controlling the timing of light emission from the light source arranged in the light source device 11. The light source drive unit 13 includes, for example, a PWM setting unit, a PWM signal generation unit, and a limiter (not shown in the figures). Based on the control of the controller 12, the light source drive unit 13 controls the light source drive of the light source device 11, performing PWM control of the light source, thereby enabling the light source to be turned on, off, and its brightness adjusted.

[0069] The light modulation device 14 modulates the light (illumination light) output from the light source device 11 based on the image signal to generate imaging light. The light modulation device 14 may have, for example, three bulbs corresponding to each of the RGB colors described later. For example, the light modulation device 14 includes a liquid crystal display panel (panel (B)) that modulates blue light (B), a liquid crystal display panel (panel (R)) that modulates red light (R), and a liquid crystal display panel (panel (G)) that modulates green light (G). The RGB colors modulated by the light modulation device 14 are combined by orthogonal dichroic prisms (not shown in the figures) and guided to the projection optical system 19.

[0070] The image processing unit 15 acquires an externally input image signal to determine the image size, resolution, and whether the image is a still or moving image. In the case of a moving image, it also determines image data attributes such as frame rate. Furthermore, if the resolution of the acquired image signal differs from the resolution of the display of the light modulation device 14, it performs resolution conversion processing. The image processing unit 15 develops the processed images into a frame memory 16 for each frame and outputs the image of each frame developed into the frame memory 16 as a display signal to the panel driving unit 17.

[0071] The panel driving unit 17 drives the light modulation device 14. By being driven by the panel driving unit 17, the transmittance of light at each pixel in the light modulation device 14 is changed, and an image is formed.

[0072] The projection optics system drive unit 18 includes a motor that drives the lens disposed in the projection optics system 19. For example, the projection optics system drive unit 18 drives the projection optics system 19 according to the control of the controller 12 to perform, for example, zoom adjustment, focus adjustment, aperture adjustment, etc.

[0073] The projection optical system 19 includes a lens group for forming an image from light modulated by the light modulation device 14.

[0074] It should be noted that, in addition to using the three-panel type of the above-mentioned three liquid crystal display panels as the light modulation device 14, the display device 10 may also include a time-division projector of the single-panel type using one liquid crystal display panel.

[0075] The reflector 20 reflects the light output from the display device 10 in a predetermined direction. Here, the reflector 20 reflects the light output from the display device 10 toward the special retroreflector 30, and also reflects the light reflected by the special retroreflector 30 toward the eye of the observer 100 and its surroundings through partial reflection.

[0076] Figure 3 The planar configuration of the special retroreflector 30 is schematically shown.

[0077] First, a typical retroreflector will be described. A typical retroreflector has a mechanism that allows reflected light to return directly along the optical axis of the incident light. The retroreflector comprises multiple retroreflecting elements arranged in a circular pattern in a two-dimensional array. Typically, the retroreflecting elements are constructed, for example, by combining three planar mirrors at right angles to each other with vertices of a cuboid (where the reflecting surfaces face inwards), forming a concave portion with a triangular pyramid shape. When viewed from directly above, a retroreflector comprising such retroreflecting elements arranged in a two-dimensional array is configured such that regular triangles are arranged as closely as possible, such as, for example, in... Figure 3 As shown in the diagram, light reaching any reflective surface is reflected on all three surfaces of the corner reflector and returns (reflects back) in the direction of incidence.

[0078] Similar to the typical retroreflector described above, the special retroreflector 30 according to this embodiment is configured such that a plurality of retroreflective elements 31 are arranged cyclically, each retroreflective element comprising three reflective surfaces. The special retroreflector 30 differs from a typical retroreflector in that one of the three surfaces constituting the retroreflective element 31 forms an inclined surface, the inclined surface forming an angle θ with respect to a state where the angle between that one surface and another adjacent surface is at a right angle (90°). Specifically, for example, as... Figure 4 As shown, when the three mutually perpendicular surfaces are referred to as surface A S1, surface B S2, and surface C S3, the retroreflective element 31 includes three surfaces: surface A S1 and surface B S2, which are perpendicular to each other, and also, for example, surface C' S3', which is angled at θ towards the inside of the concave portion having a triangular pyramid shape. The angle θ can be greater than 0° or less than 0°. That is, surface C' S3' can be inclined towards the outside of the concave portion having a triangular pyramid shape.

[0079] Figure 5 Schematic illustration along Figure 3An example of the cross-sectional configuration of the special retroreflector 30, shown by line I-I'. The special retroreflector 30 includes a pair of surfaces 30S1 and 30S2 opposite to each other. A plurality of recesses (each having a triangular pyramid shape of a retroreflector element of each of the plurality of retroreflector elements 31 constituting the special retroreflector 30) are arranged most closely on the side of surface 30S1. As described above, one of the three surfaces (surface A S1, surface B S2, and surface C' S3') constituting the retroreflector element 31 (surface C' S3') forms an inclined surface that is inclined at an angle θ, forming a right angle (90°) with another adjacent surface. The inclined surfaces (surface C' S3') of the plurality of individual retroreflector elements 31 are adjacent to each other, for example, in the Z-axis direction, which is the direction of travel of the vehicle 40 in the YZ plane, for example, as Figure 3 and Figure 5 As shown.

[0080] Figure 6 The diagram schematically illustrates the reflection pattern of the light beam entering the special retroreflector 30. For example... Figure 6 As shown, four beams output from the emission position X at different angles along the Z-axis enter different positions of a special retroreflector 30 (e.g., four retroreflection elements 31 arranged along the Z-axis). Each beam entering one of the four retroreflection elements 31 along the Z-axis is reflected in a direction different from the incident direction, having a predetermined offset angle relative to the incident direction. For example, at retroreflection elements 31 adjacent to each other along the Z-axis, the polarities of the tilt angles of adjacent tilted surfaces (surface S3' C') are positive (+) and negative (-), and are different from each other. As for the return position, the returned light from each retroreflection element 31 returns to the same focusing position (reflection position X').

[0081] Figure 7A and Figure 7B Schematic illustration along Figure 3 Another example of the cross-sectional configuration of the special retroreflector 30 intercepted by the I-I' line is shown in the diagram. Figure 5 In the cross-sectional view shown, due to the inclination, a plane is formed between adjacent inclined surfaces (C'surface S3') along the Z-axis direction. When light enters this plane between adjacent inclined surfaces (C'surface S3') along the Z-axis direction, the incoming light is reflected in an undesirable direction. Therefore, the adjacent inclined surfaces (C'surface S3') can also be configured to extend adjacently towards the side of surface 30S1, which becomes the entry surface, or they can be configured to increase the depth of the recess towards the side of surface 30S2, which is opposite to the entry surface. When the adjacent inclined surfaces (C'surface S3') both extend towards the side of surface 30S1, the adjacent inclined surfaces (C'surface S3') are constructed to protrude from surface 30S1, such as... Figure 7AAs shown. When the groove depth increases such that adjacent inclined surfaces (C' surface S3') are adjacent to each other, as in... Figure 7B As shown, surface 30S2' is newly formed at a location deeper than surface 30S2, and a flat entry surface (surface 30S2) can be obtained.

[0082] The tilted surface (C' surface) constituting the retroreflection element 31 is defined, for example, by a beam vector in the following manner.

[0083] θ satisfies the following equation (1), wherein, among the three surfaces (surface A S1, surface B S2 and surface C') constituting the retroreflector 31, two surfaces (surface A and surface B) are in contact with each other at right angles, and the angle formed by the remaining surface (surface C') and the other surfaces has an angle of inclination of θ from the state where the remaining surface (surface C') and the other surfaces are at right angles (90°).

[0084] [Mathematical Expression 1]

[0085] At this time, k pro. and k' TGT pro. Equations (2) and (3) are defined by the component of the rotation axis m perpendicular to the inclined surface (surface C'). Equations (2) and (3) represent the components from k' TGT Subtract the vector with components parallel to the rotation axis m from the middle, and denote k' TGT pro. Perpendicular to the rotation axis m. It also shows that for the incident light vector -k, the vector with a component parallel to the rotation axis m is subtracted, and -k... pro Perpendicular to the axis of rotation m (see) Figure 8 (A) to (C) in the middle.

[0086] [Mathematical Expression 2]

[0087] (m: rotation axis vector of the inclined surface, k: incident light vector, and k') TGT (Reflected light vector)

[0088] Here, equation (4) below restricts k and k'. TGT Δk and m, where k is the vector in the direction of the incident light from the light source toward the corner reflector, and k' TGTIt is the vector of the direction of the reflected light returned by the corner reflector, with an offset toward the human eye, and m is the axis of rotation of the inclined surface (surface C'), and is the unit vector perpendicular to the differential vector Δk and the normal vector nc of the surface (surface C) before the inclined surface tilts (see...). Figure 9 and Figure 10 ).

[0089] [Mathematical Expression 3]

[0090] (nc: normal vector of the inclined surface, and Δk: in the case of retroreflection on a corner reflector, the reflected light vector (-k) and k') TGT (difference between)

[0091] Here, nc and Δk in equation (4) are defined by equation (5).

[0092] [Mathematical Expression 4]

[0093] Based on the relationships defined by the various expressions in equations (1) to (5) above, including the retroreflection element 31 of the tilted surface (C' surface) obtained by rotating the surface (C surface) before tilting it about the rotation axis m by θ, the incident light, represented as vector k, is reflected in vector k'. TGT The effect of reflection in the direction of the object.

[0094] In the projection device 1 according to this embodiment, a reflector 20, tilted and positioned in front of the observer 100, causes light output from a display device 10 positioned above the observer 100 to be reflected toward a special retroreflector 30 positioned below the observer 100. Light from each image height enters the special retroreflector 30 as converging light before image formation and undergoes repeated specular reflection at each retroreflector element 31. This imparts a predetermined offset angle to the light, and the light is reflected as diverging light in a direction different from the incident direction. The diverging light output from the special retroreflector 30 is partially reflected by the reflector 20 and enters the observer 100's eye and surrounding environment. This allows a distant virtual image with a wide field of view (FOV) to be displayed in front of the observer 100.

[0095] [Installation example on a vehicle]

[0096] In projection device 1, for example, display device 10 is installed on the ceiling inside the vehicle. Additionally, a special retroreflector 30 is installed at the dashboard 42. Furthermore, the windshield 41 also serves as a reflector 20 (see, for example, see...). Figure 11A ).

[0097] Figure 11AIt is a diagram used to describe the pupil position in a visually recognizable wide-angle image. Figure 11B It is used to describe in Figure 11A The diagram shows each ray of light entering the eye of observer 100. Let's consider the conjugate points of the light entering the eye of observer 100. For example, as shown... Figure 11A As shown, light output from the respective image heights A, B, and C of the light modulation device 14 is output from the display device 10 via a polarizing beam splitter (PBS) 141 and multiple projection lenses 191A and 191B. The light output from individual image heights A, B, and C is reflected by the windshield 41 and travels in space. Then, a special retroreflector 30 imparts a predetermined offset angle to the light, and the light is reflected in a direction different from the incident direction. The light reflected from the special retroreflector 30 (return light) is partially reflected by the windshield 41 and travels towards the eye of the observer 100. At this time, as... Figure 11B As shown, light output from individual image heights A, B, and C is superimposed again at the pupil position of observer 100's eye to form an image on the retina, thus enabling visual recognition of the virtual image. In other words, the location of the light superposition is the only point (eyebox) where the entire image can be visually recognized. When the eyebox is outside the pupil position of observer 100's eye, it is impossible to visually recognize it.

[0098] Figure 12 This is a diagram illustrating the retroreflection position of a light beam at a special retroreflector 300, which includes multiple retroreflection elements 31 with uniformly tilted surfaces. When the emission position X and the various incident positions A, B, and C of the light emitted from emission position X onto the specific reflector 300 are defined in a three-dimensional Cartesian coordinate system, the angle formed by the tilted surface and the light beam, having a Y-coordinate different from that of the emission position X, deviates from the angle formed by the tilted surface and the light beam, having a Y-coordinate different from that of the emission position X. This deviation manifests as a shift in the retroreflection position X'.

[0099] Figure 13 This is a diagram used to describe the retroreflection positions of the light beam at each viewing angle at the special retroreflector 300, which includes a plurality of retroreflection elements 31 with uniformly inclined surfaces. To enable the observer 100 to visually recognize a virtual image with a wide viewing angle, a retroreflection plate extending in the vehicle's travel direction and lateral direction is positioned in front of the observer 100. When using the special retroreflector 300 positioned in front of the observer 100, the eyebox positions of the individual light beams output from the display device 10 and entering the special retroreflector 300 at individual positions A, B, and C are as follows: Figure 13 As shown, the differences are as follows. Therefore, there is no optimal point for visually identifying the entire image, and only a portion of the entire image can be visually identified.

[0100] Figure 14The in-plane configuration of the special retroreflector 30 according to this embodiment is shown. Figure 15A , 15B Correspondingly shown are retroreflective elements 31A, 31B, and 31C, which are correspondingly positioned in... Figure 14 The individual locations A, B, and C are shown in the diagram. For example, the special retroreflector 30 is configured such that among the plurality of retroreflecting elements 31 arranged in a plane, the angle formed by the inclined surface (surface S3' C') and surfaces S1 and S2 perpendicular to each other from the angle between them is... Figure 14 The left end of the special retroreflector 30 shown in the image continuously changes direction towards the right end.

[0101] For example, the retroreflective element 31B located at position B is configured such that surface S3' of C' forms an inclined surface at an angle θ and substantially parallel to surface C, as in Figure 15B As shown, position B is substantially located at the midpoint of the longitudinal direction of the special retroreflector 30. The retroreflecting elements 31A and 31C, respectively arranged at positions A and C, are substantially symmetrical in the left-right direction, with position B inserted between these positions having a shape symmetrical to each other in the left-right direction. Specifically, the retroreflecting element 31A located at position A is configured such that... Figure 15B The surface S3' shown in the figure forms an inclined surface rotated to the right by a predetermined angle, such as Figure 15A As shown. The retroreflector element 31C located at position C is configured such that... Figure 15B The surface S3' shown in the figure forms an inclined surface rotated to the left by a predetermined angle, as... Figure 15C As shown. In this way, a special retroreflector 30 is used, wherein the angle formed by the inclined surface (surface S3') with surfaces S1 and S2 is optimized according to, for example, the position in the plane, and the angle formed by the inclined surface with a beam having a Y-coordinate different from the emission position X entering the incident position C is equal to the angle formed by the inclined surface with a beam having the same Y-coordinate as the emission position X entering the incident positions A and B. Figure 16 As shown, this causes the light to focus at a single point. In other words, the eyebox positions of the individual beams output from the display device 10 and entering the special retroreflector 30 are superimposed, as shown... Figure 17 As shown in the diagram. Thus, the optimal visually recognizable point for the entire image is established at a given point.

[0102] As described above, the light output from the individual image heights A, B, and C of the light modulation device 14 is superimposed again at the pupil position of the observer 100's eye. This allows the light output from individual image heights A, B, and C to be formed into an image on the retina, thereby enabling the visual recognition of virtual images. However, due to vehicle vibrations during driving or changes between individuals (such as seat height), the pupil position of the observer 100's eye changes. Therefore, it is necessary to amplify the superimposed light and ensure that the entire image is a visually recognizable point (eyebox).

[0103] For example, the eye box can be expanded in the following way.

[0104] Figure 18 An example configuration of a display device (display device 10A) designed to extend the eyebox in the body axis direction (X-axis direction) of observer 100 is shown. Display device 10A uses an intensity modulation panel 14A of, for example, a reflective liquid crystal type (LCOS) or digital illumination processing (DLP) type, and emits illumination light (light L) loaded with image information. For example, display device 10A includes an intensity modulation panel 14A, a PBS 141, a projection lens 192 including multiple lenses including a pupil at the output port, and a light guide panel 51 extending in the X-axis direction. The light source can be a semiconductor laser (laser diode: LD) or a light-emitting diode (light-emitting diode: LED). Alternatively, an excitation light source such as a phosphor can be used.

[0105] For example, the light guide panel 51 is a so-called holographic light guide panel, which includes a reflective film 52 on one of a pair of opposing surfaces, and holographic optical elements (HOEs) 53A and 53B on the other surface. The light guide panel 51 is positioned at the pupil position X of the projection lens 192. HOE 53A is used to propagate incident light in the light guide panel 51 and is positioned at the pupil position X. HOE 53B is used to extract light from the light guide panel 51 and is positioned at one or more locations after propagation. According to this structure, multiple pupils X1, X2, X3 are replicated in the X-axis direction.

[0106] Figure 19Another example of a display device configuration (display device 10B) designed to extend the eyebox in the body axis direction (X-axis direction) of observer 100 is shown. For example, display device 10B emits illumination light loaded with image information to phase modulation panel 14B. Display device 10B includes, for example, phase modulation panel 14B, relay lens 193 including multiple lenses, and light guide panel 51 extending in the X-axis direction. Display device 10B uses diffraction by phase modulation, therefore, LD is preferably used as the light source. Display device 10B uses main diffracted light L1 with phase information modulated in phase modulation panel 14B. Zero-order reflected light L0 is removed as unwanted light using black wall 142.

[0107] In display device 10B, the pupil position X is on the surface of phase modulation panel 14B. Therefore, the primary diffracted light L1 is relayed by relay lens 193 so that the pupil conjugate image enters the light guide panel 51. Similar to display device 10A, a HOE 53A located at the pupil conjugate position Xc is used to guide the primary diffracted light L1 entering the light guide panel 51, causing it to travel within the light guide panel 51. After traveling, the primary diffracted light is extracted from HOE 53B located at one or more positions. Based on this structure, multiple pupils X1, X2, and X3 are replicated in the X-axis direction.

[0108] Figure 20 An example configuration of a pupil replication device designed to expand the eyebox in both the body axis direction (X-axis direction) and the binocular direction (Y-axis direction) of observer 100 is shown. The expansion of the eyebox in both the body axis direction (X-axis direction) and the binocular direction (Y-axis direction) of observer 100 can be achieved by combining a light guide panel 51 extending in the X-axis direction and a transmittance adjustment prism 54 disposed on HOE 53B and extending in the Y-axis direction.

[0109] Figure 21 The mechanism for pupil replication in the X-axis direction using light guide plate 51 is shown. Figure 22 The compensation relationship between diffraction and wavelength dispersion is shown. For light L entering the light guide panel 51, the amount of wavelength dispersion is compensated by internal and external HOE 53A and 53B.

[0110] Figure 23The mechanism for pupil replication in the Y-axis direction by means of transmittance adjusting prism 54 is shown. The transmittance adjusting prism 54 is configured to have multiple prisms with adjusted transmittance arranged in one axial direction. For example, seven prisms 541, 542, 543, 544, 545, 546 and 547 are arranged in the Y-axis direction. In the transmittance adjusting prism, n prisms arranged in one axis have stepped transmittance adjustment. By setting the reflectivity of the first stage prism to (N-1) / N and setting the reflectivity of each prism in the second stage and thereafter to 1 / (N-n+1), the amount of light output from each surface is equal to each other. For example, when the amount of incident light incident on the transmittance adjusting prism is set to P and N-stage prisms are set, the amount of light output from the surface of the nth prism is expressed by the following equation (6).

[0111] [Mathematical Expression 5]

[0112] By setting appropriate values ​​for these parameters, the amount of light output from each prism 541, 542, 543, 544, 545, 546, and 547 can be made uniform. This allows for visual recognition of an image with constant intensity at any location within the eye box.

[0113] [Work and Results]

[0114] The projection device 1 according to this embodiment is configured such that light output from the display device 10 is output in a desired direction by using a special retroreflector 30 that reflects light at a predetermined offset angle relative to the incident direction. According to this configuration, for example, a wide-viewing-angle virtual image can be depicted without using a large mirror optical system. This will be described below.

[0115] In recent years, HUD systems have been developed. These systems display information such as speed and navigation from the front seats towards the driver, and use light reflection from the windshield to display virtual images that include driver support and attention-grabbing information.

[0116] Typically, due to limitations in the size of the display unit, the display area of ​​existing HUDs is limited to an area of ​​approximately 10 degrees of field of view (the front center area). Furthermore, in the world of computer graphics (CG), there are many instances where advisory information or augmented reality (AR) information is overlaid and displayed across the entire windshield. However, no actual device implements this, and no actual vehicle is equipped with this technology.

[0117] For example, when a display device is arranged in the dashboard area, there exists a system that allows virtual images to be viewed in a floating manner over a wide range using Pepper's ghosting method. Using this system, virtual images can be viewed only within a distance range from the display device to the windshield; therefore, it is impossible to display virtual images at a distance. Consequently, in the prior art, there is no technology for displaying distant virtual images with a wide field of view (FOV), and no technology exists for depicting an ideal CG world.

[0118] In contrast, in this embodiment, by using a special retroreflector 30 that reflects light at a predetermined offset angle relative to the incident direction, light output from the display device 10 and incident via the reflector 20 is directed in a desired direction. Light from each image height enters the special retroreflector 30 as converging light before forming an image, and is reflected as diverging light from the incident direction in different directions. The diverging light output from the special retroreflector 30 is partially reflected by the reflector 20 and enters the eye of the observer 100 and its surrounding environment. With this configuration, a virtual image with a wide field of view (FOV) is drawn in front of the observer 100.

[0119] This enables the provision of projection devices 1 that can display virtual images with a wide field of view (FOV).

[0120] Furthermore, in this embodiment, the special retroreflector 30 is configured such that the angle formed by the mutually perpendicular inclined surfaces (surface S3' C') with surfaces S1 and S2 A and B among the plurality of retroreflective elements 31 arranged in a plane continuously varies, for example, in a direction perpendicular to the driving direction of the vehicle 40. With this configuration, light from the entire field of view output from the display device 10 is focused at or around the eye of the observer 100. This makes it possible to visually recognize the entire virtual image with a wide field of view.

[0121] Next, first to sixth modifications according to this disclosure will be described. In the following description, the same reference numerals are used to denote the same components as in the embodiments described above, and their descriptions are omitted where appropriate.

[0122] <2. Variations>

[0123] (2-1. First variation)

[0124] Figure 24 The in-plane configuration of the special retroreflector (special retroreflector 30A) used to describe the first variation of the present disclosure. Figure 25A , Figure 25B and Figure 25C The diagram shows the arrangement of the two structures respectively. Figure 24 Retroreflecting elements 31D, 31E, and 31F in regions D, E, and F shown.

[0125] The above embodiments provide an example in which, among a plurality of retroreflective elements 31 arranged in a plane, the angle formed by the inclined surfaces (C' surface S3') perpendicular to each other with surface A S1 and surface B S2 varies continuously, for example, in a direction perpendicular to the vehicle's direction of travel. However, this is not limiting.

[0126] According to this variation, the special retroreflector 30A is configured such that the interior of the plane is divided, for example, from... Figure 24 The special retroreflector 30 shown in the figure has three regions (region D, region E and region F) from the left end to the right end, and the angle formed by the inclined surface (surface S3' C') and the mutually perpendicular surfaces S1 and S2 A and B varies according to the region.

[0127] For example, a plurality of retroreflecting elements 31E are arranged in region E, substantially at the midpoint of the longitudinal direction of the special retroreflector 30, and these plurality of retroreflecting elements are configured such that surface S3' of C' forms an inclined surface at an angle θ and substantially parallel to surface C, such as Figure 25B As shown in the diagram, multiple retroreflective elements 31D and multiple retroreflective elements 31F, respectively arranged on the right and left sides of regions D and F, have a shape symmetrical to each other in the left-right direction, with region E interposed between these regions. Specifically, the retroreflective elements 31D disposed in region D are configured such that... Figure 25B The surface S3' shown in the figure forms an inclined surface rotated to the right by a predetermined angle, such as Figure 25A As shown. The retroreflector element 31F arranged in region F is configured such that... Figure 25B The surface S3' shown in the figure forms an inclined surface rotated to the left by a predetermined angle, as... Figure 25C As shown in the image.

[0128] In this way, using the special retroreflector 30A according to this modification, the interior of the plane is divided into, for example, multiple regions in a direction perpendicular to the vehicle's direction of travel, and the angle formed by the inclined surface (surface S3' C') and the mutually perpendicular surfaces A S1 and B S2 of the retroreflector 31 varies according to the region. With this configuration, although the eyeboxes of each beam output from the display device 10 and entering the special retroreflector 30A at various positions A, B, and C are as follows... Figure 26 The area shown is a unit displacement, but there are some partially overlapping areas. Therefore, by positioning the observer 100's eye in the overlapping area, the entire virtual image with a wide field of view can be visually identified.

[0129] (2-2. Second variation)

[0130] Figure 27 A schematic configuration of a special retroreflector (special retroreflector 30B) according to a second variation of this disclosure is shown.

[0131] The above embodiments provide an example in which, among a plurality of retroreflecting elements 31 arranged in a plane, the angle formed by the mutually perpendicular inclined surfaces (C' surface S3') with surfaces A S1 and B S2 varies continuously, for example, in a direction perpendicular to the vehicle's direction of travel. However, this is not limiting. The special retroreflector 30B according to this variation is a special retroreflector comprising a plurality of retroreflecting elements having uniformly inclined surfaces, and differs from the special retroreflector 30 according to the above embodiments in that the special retroreflector 30B is curved in the YZ plane direction.

[0132] For example, the special reflector 30B is configured such that the special reflector 300 is positioned in a direction perpendicular to the vehicle's direction of travel (e.g., Figure 27 The two ends of the special retroreflector 300 (shown in the Y-axis direction) are bent toward the Z-axis direction, which serves as the observer's side, and the special retroreflector 300 includes a plurality of retroreflecting elements having the aforementioned uniformly inclined surfaces. With this configuration, the inclined surfaces (C' surface S3') of the retroreflecting elements are configured to rotate approximately to the middle in the longitudinal direction of the special retroreflector 30B. Similar to the special retroreflector 30 according to the above embodiment, the retroreflecting elements are arranged at both ends in a direction perpendicular to the vehicle's direction of travel.

[0133] Thus, according to the special retroreflector 30B of this modification, the special retroreflector, comprising a plurality of retroreflecting elements having uniformly inclined surfaces, is configured such that both ends of the special retroreflector in a direction perpendicular to the vehicle's travel direction are bent toward the Z-axis direction, which serves as the observer's side. Even with this structure, the same effect as the embodiment described above can be obtained.

[0134] (2-3. Third variation)

[0135] Figure 28 A schematic configuration of a special retroreflector (special retroreflector 30C) according to a third variation of this disclosure is shown.

[0136] The above embodiments provide an example in which, among a plurality of retroreflecting elements 31 arranged in a plane, the angle formed by the mutually perpendicular inclined surfaces (C' surface S3') with surface A S1 and surface B S2 varies continuously, for example, in a direction perpendicular to the vehicle's direction of travel. However, this is not limiting. The special retroreflector 30C according to this variation is a special retroreflector comprising a plurality of retroreflecting elements having uniformly inclined surfaces, and differs from the special retroreflector 30 according to the above embodiments in that it provides a bend toward the X-axis direction.

[0137] For example, the special retroreflector 30C is directed towards the vehicle's ceiling or tires (e.g., Figure 28The X-axis direction shown in the diagram) bends the special retroreflector 300 in a direction perpendicular to the vehicle's direction of travel (e.g., the direction shown in the diagram). Figure 28 The special retroreflector 300 is formed at two ends in the Y-axis direction shown in the diagram, and includes a plurality of retroreflecting elements having the aforementioned uniformly inclined surfaces. With this configuration, the inclined surfaces (C' surface S3') of the retroreflecting elements are configured to rotate approximately towards the center in the longitudinal direction of the special retroreflector 30C. Similar to the special retroreflector 30 according to the above embodiment, the retroreflecting elements are arranged at two end sides in a direction perpendicular to the vehicle's travel direction.

[0138] Thus, according to the special retroreflector 30C of this modification, the special retroreflector, comprising a plurality of retroreflecting elements having uniformly inclined surfaces, is configured such that the two ends of the special retroreflector in a direction perpendicular to the vehicle's direction of travel are bent toward the vehicle's ceiling or tires. Even with this structure, the same effect as the embodiment described above can be obtained.

[0139] (2-4. Fourth variation)

[0140] Figure 29 An example of the configuration of a projection device according to a fourth variation of this disclosure is shown (projection device 1A).

[0141] The above embodiments provide an example of a method for using pupil replication to expand the eyebox in the body axis direction (X-axis direction) of the observer 100. Conversely, the projection device 1A according to this modification is configured such that the reflector device 21 is offset in the vehicle's travel direction (Z-axis direction) so that the eyebox follows in the body axis direction (X-axis direction) of the observer 100.

[0142] Similar to the projection device 1 according to the above embodiment, the projection device 1A includes a display device 10 installed on the ceiling inside the vehicle, a windshield 41, and a special retroreflector 30 installed on the dashboard 42. The projection device 1A further includes a detection camera 55 for detecting the position of the observer 100's eyes, and a rotary motor 56 for offsetting the reflector device 21 in the direction of travel (Z-axis direction).

[0143] Here, the detection camera 55 corresponds to a specific example of a "pupil position detection camera" according to an exemplary embodiment of the present disclosure. The rotary motor 56 corresponds to a specific example of a "first drive unit" according to an exemplary embodiment of the present disclosure.

[0144] In projection device 1A, the position (height) information of the observer 100's eye is identified by detection camera 55. After calculating the offset of the eyebox in the X-axis direction, the eyebox is tracked based on the pupil tracking output. For example, as... Figure 29As shown, when the reflector device 21 moves back and forth in the vehicle's direction of travel (Z-axis direction), the incident position of the light output from the display device 10 entering the special retroreflector 30 and the incident position of the returned light output from the special retroreflector 30 entering the windshield 41 are correspondingly offset in the vehicle's direction of travel (Z-axis direction). With this configuration, the eye box follows the observer 100 in the body axis direction (X-axis direction).

[0145] In addition, such as Figure 30 As shown, the projection device 1A can move the position of the special retroreflector 30A in the direction of the observer 100's main axis (X-axis direction), instead of moving the reflector device 21 in the direction of travel (Z-axis direction). By using this method, the eye box can be made to follow.

[0146] Thus, in this modified example, by moving the reflector device 21 in the vehicle's direction of travel (Z-axis direction), or by moving the position of the special retroreflector 30A in the main axis direction (X-axis direction), the eye box is made to follow the observer 100 in the main axis direction (X-axis direction). Using this configuration, the eye box can also be substantially enlarged, as in the embodiment described above. Therefore, changes in the pupil position of the observer 100's eyes caused by vehicle vibrations or individual variations (such as seat height) during driving can be addressed.

[0147] (2-5. Fifth variation)

[0148] Figure 31 An example of the configuration of a projection device (projection device 1B) according to a fifth variation of this disclosure is shown.

[0149] The above embodiments provide an example of a method for using pupil replication to unfold an eye box in the binocular direction (Y-axis direction) of observer 100. Conversely, the projection device 1B according to this modification is configured such that by moving the display device 10 in the binocular direction (Y-axis direction) of observer 100, the eye box follows the binocular direction (Y-axis direction) of observer 100.

[0150] Similar to the projection device 1 according to the above embodiment, the projection device 1B includes a display device 10 installed on the ceiling inside the vehicle, a windshield 41, and a special retroreflector 30 installed on the dashboard 42. The projection device 1B further includes a detection camera 55 for detecting the position of the observer 100's eyes, and a rotary motor 57 for offsetting the display device 10 in the direction of the observer 100's two eyes (Y-axis direction).

[0151] Here, the detection camera 55 corresponds to a specific example of a "pupil position detection camera" according to an exemplary embodiment of the present disclosure. The rotary motor 57 corresponds to a specific example of a "second drive unit" according to an exemplary embodiment of the present disclosure.

[0152] In this way, through this variation, by moving the display device 10 in the direction of the observer 100's eyes (Y-axis direction), the eye box follows the direction of the observer 100's eyes (Y-axis direction). Using such a configuration, the eye box can also be substantially enlarged, as in the embodiment described above. Therefore, changes in the pupil position of the observer 100's eyes caused by vehicle vibrations or individual variations (such as seat height) during driving can be addressed.

[0153] It should be noted that by combining the projection device 1B according to this modification with the fourth modification and, for example, moving the reflector device 21 in the vehicle's travel direction (Z-axis direction), the eye box can be made to further follow the observer 100 in the body axis direction (X-axis direction). Furthermore, in the projection device 1B according to this modification, for example, as... Figure 32 As shown, by using a light guide panel 51 extending in the binocular direction (Y-axis direction), the pupil can be replicated in the Y-axis direction. With this configuration, the eye box extends towards the observer 100's body axis (X-axis direction) and towards both eyes (Y-axis direction). This enables the realization of a compact projection device that can be installed in a vehicle.

[0154] (2-6. Sixth variation)

[0155] Figure 33 An example of the configuration of the pupil copying apparatus (pupil copying apparatus 60) according to the sixth variation of this disclosure is shown. (Except in...) Figure 20 In addition to the pupil replication device shown in the figure, by using in Figure 33 The pupil replication device 60 shown can also expand the eye box in the direction of the observer 100’s body axis (X-axis direction) and in the direction of the two eyes (Y-axis direction).

[0156] Figure 33The planar and cross-sectional configurations of the pupil replication device 60 are schematically shown. The pupil replication device 60 is a light guide panel having a pair of surfaces 61S1 and 61S2 facing each other. For example, the light guide panel 61 includes a total internal reflection region 62 comprising a plurality of prisms 621 arranged along the X-axis direction, and also includes an output region 63 comprising a plurality of prisms 631 extending along the X-axis direction and arranged along the Y-axis direction. The prisms 621 include reflective surfaces tilted in a predetermined direction (e.g., a reflective surface tilted at approximately 45° relative to the body axis direction (X-axis direction) of the observer 100). An incident portion 64 is disposed at surface 61S2, located on the side opposite to surface 61S1, which serves as the light output surface of the light guide panel 61.

[0157] A pupil replication device 60 is positioned at the pupil location of the projection lens 192. Light L incident from the projection lens 192 onto the incident portion 64 passes through the total internal reflection region 62 and is reflected along the Y-axis direction by prisms 621 arranged along the X-axis. The light L reflected by each prism 621 is reflected along the Z-axis direction by each prism 631 arranged in the Y-axis direction and output from the surface 61S1, as shown below. Figure 34 As shown. For example, using a light guide panel 61 in which 10 prisms 621 are arranged in the X-axis direction and 5 prisms 631 are arranged in the Y-axis direction, an incident beam is expanded (replicated) into 10 beams in the total internal reflection region 62, and further expanded (replicated) into 50 beams for output in the output region 63, as shown. Figure 33 As shown. That is, 50 pupils are replicated in the X-axis and Y-axis directions.

[0158] These are descriptions of the embodiments and the first to sixth variations. However, this disclosure is not limited to the embodiments described above, and various variations are possible. For example, the arrangement and number of components of the optical system given as examples in the embodiments described above are merely examples. It is not necessary to provide all the components. Furthermore, other components may be provided.

[0159] It should be noted that the effects described in this specification are merely illustrative and are not limited to those described. Other effects are also possible.

[0160] This technology can be configured as follows. Utilizing this technology with the following configuration, output is made in a desired direction by using a retroreflector plate that reflects the light relative to the incident direction and applies a predetermined offset angle. Therefore, for example, virtual images with a wide field of view can be drawn without using a large mirror optical system. This makes it possible to provide projection devices that can display virtual images with a wide FOV. [1]

[0162] A projection device, comprising: Display device; A reflector that reflects light emitted from a display device in a predetermined direction; and A retroreflector plate reflects light at a predetermined offset angle relative to the incident direction, and the light enters through a reflector. [2]

[0164] According to the projection device described above [1], wherein, The retroreflector plate includes a main surface, in which multiple retroreflecting elements are arranged in a two-dimensional array. Each of the multiple retroreflective elements comprises a surface adjacent to each other and multiple other surfaces. Multiple other surfaces are in contact with each other at a 90° angle, and One surface and multiple other surfaces are in contact with each other at an angle greater than or less than 90°. [3]

[0166] According to the projection device described in [1] or [2] above, wherein, The retroreflector plate includes a main surface, and multiple retroreflective elements are arranged in a two-dimensional array on the main surface. Multiple retroreflective elements each have a triangular pyramid shape comprising three surfaces. [4]

[0168] According to the projection device described above [3], wherein, Each of the multiple retroreflective elements comprises three surfaces: The first and second surfaces are in contact with each other at right angles; and The third surface is an inclined surface that is tilted at an angle θ from the third' surface, which is in contact with the first and second surfaces at right angles respectively. [5]

[0170] According to the projection device described above [4], wherein, Angle θ satisfies the following equation (1), and k pro and k' TGT pro Defined by the following equations (2) and (3), [Mathematical Expression 1]

[0171] (m: rotation axis vector of the inclined surface, k: incident light vector, and k') TGT (Reflected light vector). [6]

[0173] According to the projection device described above [4] or [5], the angle θ of the inclined surface varies depending on the position of the main surface. [7]

[0175] According to the projection device described above [4] or [5], wherein, The main surface comprises multiple areas, and The angle θ of the inclined surface varies depending on the region. [8]

[0177] According to any one of the projection devices in [4] to [7] above, wherein, The corresponding tilted surfaces of multiple retroreflective elements have equal angles θ to each other, and The retroreflector plate bends inward toward the plane of the main surface. [9]

[0179] According to any one of the projection devices in [4] to [7] above, wherein, When the X-axis is set to the human body axis, the Y-axis to the direction of both eyes, and the Z-axis to be perpendicular to both the X and Y axes, the main surface of the retroreflector plate is approximately aligned with the YZ plane. The two ends of the main surface in the Y-axis direction are along the X-axis direction.

[10]

[0181] According to any one of the projection devices in [1] to [9] above, wherein, The X-axis direction is set as the human body axis. The Y-axis direction is set to the direction of both eyes, and The projection device also includes a pupil copying device, which is disposed between the display device and the reflector. The pupil copying device copies the pupil conjugate point in the Y-axis direction, the X-axis direction, or both directions.

[11]

[0183] The projection device according to the above

[10] also includes: a light guide panel extending in either the Y-axis direction or the X-axis direction as a pupil replication device, the light guide panel including a surface provided with holographic optical elements.

[12]

[0185] The projection device according to the above

[11] also includes: a transmittance adjustment prism, which extends as a pupil copying device in another direction between the Y-axis and X-axis directions, and the transmittance adjustment prism is disposed on one surface side of the light guide panel.

[13]

[0187] According to any one of the projection devices in [1] to

[12] above, wherein, The X-axis direction is set to the human body axis. The Y-axis direction is set to the direction of both eyes, and The projection device also includes a pupil tracking device, which is set between the display device and the reflector. The pupil tracking device moves the visual recognition area in the X-axis or Y-axis direction according to the position of the person's pupil.

[14]

[0189] The projection device according to the above

[13] also includes: a first drive unit, which acts as a pupil tracking device to move the reflector in the Z-axis direction.

[15]

[0191] The projection device according to the above

[13] or

[14] further includes: a second drive unit, which acts as a pupil tracking device to move the display device in the Y-axis direction.

[16]

[0193] According to any one of [1] to

[15] above, the projection device includes: Intensity modulation panel; and The projection lens includes a pupil at the output port.

[17]

[0195] According to any one of

[10] to

[16] above, the projection device includes: Phase modulation panel; and The relay lens guides the light to the pupil replication device.

[18]

[0197] According to any one of the projection devices in [1] to

[17] above, wherein, A reflector is a vehicle's windshield, and The display device and reflector are located inside the vehicle.

[19]

[0199] The projection device according to any one of [1] to

[18] above further includes: a pupil position detection camera for detecting the position of a person's pupil.

[0200] This application claims the benefit of Japanese priority patent application JP2024-032405, filed with the Japan Patent Office on March 4, 2024, the entire contents of which are incorporated herein by reference.

[0201] Those skilled in the art can make various modifications, combinations, sub-combinations and alterations based on design requirements and other factors, and it should be understood that they are within the scope of the appended claims or their equivalents.

Claims

1. A projection device, comprising: Display device; A reflector that reflects light emitted from the display device in a predetermined direction; as well as A retroreflector plate reflects light at a predetermined offset angle relative to the incident direction, the light entering via the reflector.

2. The projection device according to claim 1, wherein, The retroreflecting plate includes a main surface, in which multiple retroreflecting elements are arranged in a two-dimensional array. Each of the plurality of retroreflective elements includes a surface adjacent to each other and a plurality of other surfaces. The plurality of other surfaces are in contact with each other at a 90° angle, and The one surface and the plurality of other surfaces are in contact with each other at an angle greater than or less than 90°.

3. The projection device according to claim 1, wherein, The retroreflection plate includes a main surface, and multiple retroreflection elements are arranged in a two-dimensional array on the main surface. The plurality of retroreflective elements each have a triangular pyramid shape comprising three surfaces.

4. The projection device according to claim 3, wherein, Each of the plurality of retroreflective elements comprises, as the three surfaces, the following: The first and second surfaces are in contact with each other at right angles; as well as The third surface is an inclined surface that is tilted at an angle θ from the third' surface, which is in contact with the first surface and the second surface at right angles respectively.

5. The projection device according to claim 4, wherein, The angle θ satisfies the following equation (1), and k pro and k' TGT pro Defined by the following equations (2) and (3), [Mathematical Expression 1] (m: rotation axis vector of the inclined surface, k: incident light vector, and k') TGT (Reflected light vector).

6. The projection device according to claim 4, wherein, The angle θ of the inclined surface varies depending on the position of the main surface.

7. The projection device according to claim 4, wherein, The main surface includes multiple regions, and The angle θ of the inclined surface varies depending on the plurality of regions.

8. The projection device according to claim 4, wherein, The respective tilted surfaces of the plurality of retroreflective elements have equal angles θ to each other, and The retroreflector plate is bent inward toward the plane of the main surface.

9. The projection device according to claim 4, wherein, When the X-axis is set as the human body axis, the Y-axis as the direction of both eyes, and the Z-axis as the direction perpendicular to the X-axis and Y-axis, the main surface of the retroreflective plate is approximately aligned with the YZ plane. The main surface has two ends along the X-axis direction in the Y-axis direction.

10. The projection device according to claim 1, wherein, The X-axis direction is set as the human body axis. The Y-axis direction is set to the direction of both eyes, and The projection device further includes a pupil copying device disposed between the display device and the reflector, wherein the pupil copying device copies the pupil conjugate point in the Y-axis direction, the X-axis direction, or both directions.

11. The projection device according to claim 10, further comprising: A light guide panel extends as the pupil replication device in either the Y-axis direction or the X-axis direction, and the light guide panel includes a surface on which a holographic optical element is disposed.

12. The projection device according to claim 11, further comprising: A transmittance adjustment prism, which extends as the pupil replication device in another direction between the Y-axis and the X-axis, is disposed on one side of a surface of the light guide panel.

13. The projection device according to claim 1, wherein, The X-axis direction is set to the human body axis. The Y-axis direction is set to the direction of both eyes, and The projection device further includes a pupil tracking device, which is disposed between the display device and the reflector. The pupil tracking device moves the visual recognition area in the X-axis direction or the Y-axis direction according to the position of the person's pupil.

14. The projection device according to claim 13, further comprising: The first drive unit, acting as the pupil tracking device, moves the reflector in the Z-axis direction.

15. The projection device according to claim 13, further comprising: The second drive unit, acting as the pupil tracking device, moves the display device in the Y-axis direction.

16. The projection device according to claim 1, wherein, The display device includes: Intensity modulation panel; and The projection lens includes a pupil at the output port.

17. The projection device according to claim 10, wherein, The display device includes: Phase modulation panel; and A relay lens guides light to the pupil replication device.

18. The projection device according to claim 1, wherein, The reflector is the vehicle's windshield, and The display device and the retroreflector are installed inside the vehicle.

19. The projection device according to claim 1, further comprising: A pupil position detection camera detects the position of a person's pupil.

Images