Projection apparatus

Abstract

A projection apparatus according to an embodiment of the present disclosure comprises a display device, a reflection mirror that reflects light emitted from the display device in a predetermined direction, one or a plurality of condenser lenses, and a retroreflective plate that is disposed at the focal length position of the condenser lens and reflects light incident via the reflection mirror and the condenser lens in the incidence direction.

Description

projection device

[0001] The present disclosure relates to a projection device used, for example, as a head-up display.

[0002] For example, Patent Document 1 discloses an information display device that uses a reflector having a plurality of unit areas arranged two-dimensionally on its main surface, thereby alleviating restrictions on installation locations.

[0003] International Publication No. 2018 / 061444

[0004] Meanwhile, a projection device that displays driving assistance information to a vehicle driver is required to have a wide viewing angle and to display a focused virtual image.

[0005] It is desirable to provide a projection device that can display a wide viewing angle and a focused virtual image.

[0006] A projection device according to one embodiment of the present disclosure includes a display device, a reflecting mirror that reflects light emitted from the display device in a predetermined direction, one or more focusing lenses, and a retroreflector that is positioned at the focal length of the focusing lens and reflects light that has entered through the reflecting mirror and the focusing lens in the direction of incidence.

[0007] In a projection device according to an embodiment of the present disclosure, one or more condensing lenses are disposed between the reflecting mirror and the retroreflector so that the retroreflector is positioned at a condensing distance from the reflecting mirror. This allows light condensed by the condensing lenses to be incident on the retroreflector, thereby substantially reducing the spread of the returning light emitted from the retroreflector.

[0008] FIG. 1 is a schematic diagram illustrating an example configuration of a projection device according to an embodiment of the present disclosure. FIG. 2 is a functional block diagram illustrating the configuration of the display device illustrated in FIG. 1. FIG. 3 is a schematic plan view of a retroreflector. FIG. 4 is a schematic diagram illustrating retroreflective elements constituting the retroreflector illustrated in FIG. 3. FIG. 5 is a schematic cross-sectional view illustrating the retroreflector illustrated in FIG. 3. FIG. 6 is a schematic diagram illustrating an example configuration of the projection device illustrated in FIG. 1 mounted on a vehicle. FIG. 7A is a diagram illustrating pupil positions at which a wide-angle image can be viewed. FIG. 7B is a diagram illustrating the incidence of each light shown in FIG. 7A on the human eye. FIG. 8 is a schematic diagram illustrating an example configuration of a display device in the projection device illustrated in FIG. 6. FIG. 9 is a perspective view illustrating an example configuration of a pupil duplication device. FIG. 10 is a diagram illustrating the state of light incident on the pupil duplication device illustrated in FIG. 9. FIG. 11 is a schematic diagram illustrating an example configuration of a general projection device. FIG. 12 is a schematic diagram illustrating the state of light returned from a retroreflector in a general projection device. FIG. 13 is a schematic diagram illustrating the state of light returned from a retroreflector in a general projection device in which a pupil is duplicated. Fig. 14 is a schematic diagram illustrating the state of returned light from a retroreflector in the configuration of the projection device shown in Fig. 1. Fig. 15 is a schematic diagram illustrating an example configuration of a display device according to Modification 1 of the present disclosure. Fig. 16 is a schematic diagram illustrating an example configuration of a projection device according to Modification 2 of the present disclosure. Fig. 17 is a schematic diagram illustrating an example configuration of a projection device according to Modification 3 of the present disclosure. Fig. 18 is a schematic diagram illustrating an example configuration of a projection device according to Modification 4 of the present disclosure.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description is one specific example of the present disclosure, and the present disclosure is not limited to the following aspects. Furthermore, the present disclosure is not limited to the arrangement, dimensions, dimensional ratios, etc. of each component shown in each drawing. The order of description is as follows: 1. Embodiment (Example of a projection device in which a condenser lens is arranged between a reflective mirror and a retroreflector) 2. Modifications 2-1. Modification 1 (Another example of a display device) 2-2. Modification 2 (Another example of a projection device) 2-3. Modification 3 (Another example of a projection device) 2-4. Modification 4 (Another example of a projection device)

[0010] 1 illustrates a schematic configuration of a projection device (projection device 1) according to an embodiment of the present disclosure. The projection device 1 is used in, for example, a head-up display (HUD) system that displays speed, navigation, and the like to a driver in the front seat of a vehicle and displays virtual images including driving support information and attention-grabbing information by using light reflected on the windshield.

[0011] [Configuration of Projection Device] The projection device 1 includes a display device 10, a reflecting mirror 20, a retroreflector 30, and a condenser lens 40.

[0012] Here, the display device 10 corresponds to a specific example of a "display device" in an embodiment of the present disclosure. The reflecting mirror 20 corresponds to a specific example of a "reflecting mirror" in an embodiment of the present disclosure. The retroreflector 30 corresponds to a specific example of a "retroreflector" in an embodiment of the present disclosure. The condenser lens 40 corresponds to a specific example of a "condenser lens" in an embodiment of the present disclosure.

[0013] 2 is a functional block diagram showing an example of the configuration of the display device 10. The display device 10 projects a virtual image in front of the observer 100. The display device 10 is connected to an external image supply device, such as a computer such as a PC (not shown) or various image players, via an I / F (interface), and projects the virtual image based on an image signal input to this interface.

[0014] The display device 10 includes, for example, a light source device 11, a control unit 12, a light source driving unit 13, a light modulation device 14, an image processing unit 15, a frame memory 16, a panel driving unit 17, a projection optical system driving unit 18, and a projection optical system 19.

[0015] Although not shown, the light source device 11 includes a light source driver that drives the light source and a current value setting unit that sets the current value when driving the light source. The light source driver generates a current having a current value set by the current value setting unit based on power supplied from a power supply circuit (not shown) in synchronization with a signal input from the light source drive unit 13. The generated current is supplied to each of the light sources.

[0016] The control unit 12 controls the light source driving unit 13 , the image processing unit 15 , the panel driving unit 17 and the projection optical system driving unit 18 .

[0017] The light source driving unit 13 outputs a signal for controlling the light emission timing of the light source arranged in the light source device 11. The light source driving unit 13 includes, for example, a PWM setting unit, a PWM signal generating unit, and a limiter (not shown), and controls the light source driver of the light source device 11 based on the control of the control unit 12, and PWM controls the light source to turn the light source on and off or adjust the brightness.

[0018] The light modulation device 14 modulates the light (illumination light) output from the light source device 11 based on an image signal to generate image light. The light modulation device 14 is configured to include, for example, three light valves corresponding to the respective colors of RGB (described later). Examples of the light modulation device 14 include 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 color lights modulated by the light modulation device 14 are combined by a cross dichroic prism or the like (not shown) and guided to the projection optical system 19.

[0019] The image processing unit 15 acquires an image signal input from outside and performs tasks such as determining the image size, resolution, and whether the image is a still image or a moving image. If the image is a moving image, it also determines image data attributes such as the frame rate. If the resolution of the acquired image signal differs from the display resolution of the light modulation device 14, it performs resolution conversion processing. The image processing unit 15 loads the images after each of these processes into the frame memory 16 for each frame, and outputs the image for each frame loaded in the frame memory 16 to the panel driving unit 17 as a display signal.

[0020] The panel driver 17 drives the light modulation device 14. When the panel driver 17 is driven, the light transmittance of each pixel arranged in the light modulation device 14 changes, and an image is formed.

[0021] The projection optical system driving unit 18 includes a motor that drives a lens arranged in the projection optical system 19. Under the control of the control unit 12, the projection optical system driving unit 18 drives, for example, the projection optical system 19, and performs, for example, zoom adjustment, focus adjustment, and aperture adjustment.

[0022] The projection optical system 19 includes a group of lenses for forming an image using the light modulated by the light modulation device 14 .

[0023] In addition, the display device 10 may be configured as a three-panel type projector using three liquid crystal display panels as the light modulation device 14, as well as a single-panel type time-division projector using one liquid crystal display panel.

[0024] The reflective mirror 20, for example, reflects in a predetermined direction the light emitted from the display device 10. Here, the reflective mirror 20 transmits the light emitted from the display device 10 toward the retroreflector 30, and also partially reflects the light reflected by the retroreflector 30 (returned light) toward the vicinity of the eyes of the observer 100.

[0025] The retroreflector 30 has a mechanism for returning reflected light directly to the optical axis of the incident light. The retroreflector 30 has a plurality of retroreflecting elements 31 periodically arranged in a two-dimensional array.

[0026] FIG. 3 is a schematic diagram showing the planar configuration of a retroreflector 30. FIG. 4 is a schematic diagram showing the configuration of multiple retroreflector elements 31 constituting the retroreflector 30. The retroreflector 31 is, for example, three plane mirrors combined at right angles to each other with their reflective surfaces facing inward, like the vertices of a cube. Specifically, as shown in FIG. 4, the retroreflector 31 has three surfaces S1, S2, and S3 combined so that they are perpendicular to each other, thereby forming triangular pyramidal recesses 31c on the inside of the three surfaces S1, S2, and S3. When viewed from directly above, the retroreflector 30, in which such retroreflector elements 31 are arranged in a two-dimensional array, has a close-packed arrangement of equilateral triangles, as shown in FIG. 3, for example. Light that reaches any of the reflective surfaces is reflected by the corner deflectors on the three surfaces and returns to the direction of incidence (retroreflected).

[0027] Figure 5 is a schematic diagram showing the cross-sectional structure of the retroreflector 30 corresponding to line II' in Figure 3. The retroreflector 30 has a pair of opposing surfaces 30S1 and 30S2. As shown in Figure 5, for example, a light ray (incident light L0) incident on each retroreflector element 31 is repeatedly specularly reflected by a reflective surface S consisting of three surfaces S1, S2, and S3 arranged at right angles to one another, and ultimately returns to the incident direction as returning light L1.

[0028] The condensing lens 40 condenses the substantially parallel light L emitted from the display device 10 and transmitted by the reflecting mirror 20 to a predetermined spot diameter and makes the light incident on the retroreflector 30. The condensing lens 40, which will be described in detail later, outputs the light L, which includes light retroreflected from the retroreflector 30 and light reflected with a spread within a certain angular range centered on the retroreflection direction, as substantially parallel light toward the reflecting mirror 20.

[0029] The condenser lens 40 is, for example, a collimator lens 41, and is arranged so as to cover the entire surface of the retroreflector 30 in a plan view (see, for example, FIG. 6). Furthermore, if one lens cannot cover the entire surface of the retroreflector 30, multiple lenses may be arranged two-dimensionally in parallel.

[0030] In the projection device 1 of this embodiment, light L emitted from a display device 10 disposed above an observer 100 is incident on a retroreflector 30 disposed below the observer 100 via a reflecting mirror 20 and a condensing lens 40. Light from each image height is incident on the retroreflector 30 before being focused as converging light, and as a result of repeated specular reflection by each retroreflecting element 31, returns to the incident direction as diverging light. The diverging light emitted from the retroreflector 30 is converted into approximately parallel light via the condensing lens 40, partially reflected by a reflecting mirror 20 disposed obliquely in front of the observer 100, and enters the vicinity of the observer's 100's eyes. As a result, a distant virtual image with a wide field of view (FOV) is displayed in front of the observer 100.

[0031] 6 shows a configuration example (projection device 1A) in which the above-described projection device 1 is mounted on a vehicle. In the projection device 1A, for example, the display device 10 is disposed outside the vehicle 50 (for example, on the roof) together with the mirror device 21, and the retroreflector 30 and the condenser lens 40 (collimator lens 41) are disposed on the dashboard 52. In the projection device 1, the mirror device 21 and the windshield 51 of the vehicle 50 correspond to a specific example of a "reflecting mirror" in one embodiment of the present disclosure.

[0032] FIG. 7A illustrates pupil positions at which a wide-angle image can be viewed. FIG. 7B illustrates the incidence of light at image heights A, B, and C shown in FIG. 7A on the eye of observer 100. Consider the conjugate points of light entering the eye of observer 100. Light emitted from image heights A, B, and C (hereinafter referred to as image heights A, B, and C) on the light modulation device 14 is emitted from the display device 10 via, for example, a polarizing beam splitter (PBS) 141 and multiple projection lenses 191A and 191B, as shown in FIG. 7A . The light emitted from image heights A, B, and C is reflected by the mirror device 21, propagates through space, and is returned to approximately the incident direction by the retroreflector 30. The returning light from the retroreflector 30 is partially reflected by the windshield 51 and heads toward the eye of observer 100. At this time, as shown in Figure 7B, the light emitted from each image height A, B, and C overlaps again at the pupil position of the observer's 100's eye, forming an image on the retina and causing the observer to view a virtual image. In other words, the position where the light overlaps is the only point (eyebox) at which the entire image can be viewed, and if the eyebox is not positioned at the pupil position of the observer's 100's eye, the image will no longer be visible. However, because the pupil position of the observer's 100 changes due to vehicle vibrations while driving and individual differences such as sitting height, it is necessary to enlarge the eyebox.

[0033] The eyebox can be enlarged, for example, as follows:

[0034] FIG. 8 shows an example of a display device configuration (display device 10A) that supports expansion of the eyebox of an observer 100 in the body axis direction (X-axis direction) and the direction of both eyes (Y-axis direction). The display device 10A uses, for example, a reflective liquid crystal on silicon (LCOS) or digital lighting processing (DLP) intensity modulation panel 14A to project illumination light (light L) carrying video information. The display device 10A includes, for example, the intensity modulation panel 14A, a PBS 141, a projection lens 192 consisting of multiple lenses with pupils at their exits, and a pupil duplication device 60 extending in the X-axis and Y-axis directions. A semiconductor laser (laser diode: LD) or a light-emitting diode (light-emitting diode: LED) can be used as the light source. Alternatively, an excitation light source such as a phosphor can be used.

[0035] 9 is a schematic diagram showing the planar and cross-sectional configurations of the pupil duplication device 60. The pupil duplication device 60 is a light guide plate having a pair of opposing surfaces 61S1 and 61S2. The light guide plate 61 has a total reflection region 62 in which a plurality of half mirrors 621 having a predetermined inclination (e.g., approximately 45° with respect to the body axis direction (X-axis direction) of the observer 100) are arranged in the X-axis direction, and an exit region 63 in which a plurality of half mirrors 631 extending in the X-axis direction are arranged in the Y-axis direction. An incident portion 64 is provided on a surface 61S2 of the light guide plate 61 opposite to the surface 61S1, which serves as the light exit surface.

[0036] In the pupil duplication device 60, the plurality of half mirrors 621 that constitute the total reflection region 62 correspond to a specific example of a "first half mirror group" in an embodiment of the present disclosure. The plurality of half mirrors 631 that constitute the exit region 63 correspond to a specific example of a "second half mirror group" in an embodiment of the present disclosure.

[0037] The pupil duplication device 60 is disposed at the pupil position of the projection lens 192. Light L incident on the input section 64 from the projection lens 192 propagates through the total reflection region 62 and is reflected in the Y-axis direction by each of the half mirrors 621 arranged in the X-axis direction. The light L reflected by each of the half mirrors 621 is reflected in the Z-axis direction by each of the half mirrors 631 arranged in the Y-axis direction, and is emitted from each of the surfaces 61S1, for example, as shown in FIG. 10. For example, in a light guide plate 61 having ten half mirrors 621 arranged in the X-axis direction and five half mirrors 631 arranged in the Y-axis direction as shown in FIG. 9, a single incident light ray is expanded (duplicated) into ten light rays in the total reflection region 62, and further expanded (duplicated) into 50 light rays in the output region 63 before being emitted. In other words, 50 pupils are duplicated in the X-axis and Y-axis directions.

[0038] [Functions and Effects] In the projection device 1 of this embodiment, the condenser lens 40 is arranged between the reflecting mirror 20 and the retroreflector 30 so that the retroreflector 30 is located at the focal distance position. As a result, light L condensed by the condenser lens 40 is incident on the retroreflector 30, so that even if there is an angular spread of the returned light emitted from the retroreflector 30, the returned light is converted into approximately parallel light by the condenser lens arranged at the focal distance position, and the spread of the returned light emitted from the retroreflector 30 is substantially reduced. This will be explained below.

[0039] In recent years, development has been progressing on HUD systems that display speed, navigation, etc. to the driver in the front seat of a vehicle and display virtual images including driving support information and cautionary information using light reflection on the windshield.

[0040] Generally, due to the size constraints of display devices, existing HUDs are limited to displaying only an area with a viewing angle of about 10 degrees (the central area in front). Meanwhile, in the world of computer graphics (CG), there are many examples of warning information and augmented reality (AR) information superimposed over the entire windshield. However, in reality, no device that can achieve this yet exists, and none has been installed in an actual vehicle.

[0041] For example, when a display device is placed in the dashboard area, a method called Pepper's Ghost is used to create a virtual image that appears floating over a wide area. With this method, the virtual image is only visible from the distance between the display device and the windshield, so it is not possible to display a virtual image from a distance. Therefore, conventional technology does not have a technology that can display a virtual image over a wide FOV and at a distance, and there was no technology that could realize the ideal CG world.

[0042] Fig. 11 shows an example of the configuration of a typical projection device (projection device 1000A). Typical projection device 1000A uses a light source unit located under dashboard 1012 in the front seat of a vehicle, a mirror optical system including a display panel 1013 and a concave mirror 1014 that magnify the light emitted from the unit, and a concave mirror optical system to deliver light to the eyes of a driver (observer 100). As shown in Fig. 11, divergent light reaching observer 100 gives the impression that a virtual image is floating in front of observer 100, which is conjugate with the virtual light-emitting point. However, as described above, projection device 1000A has a limit of an FOV of about 10 degrees.

[0043] 12, a projection device 1000B using a retroreflective element 1030 can be considered as a method for displaying a wide FOV virtual image in front of (distant from) the observer 100. The retroreflective element 1030 has a mechanism for returning reflected light directly to the optical axis of the incident light, but in reality, due to various factors, the reflection spreads within a certain angular range centered on the retroreflective direction.

[0044] In the projection device 1000B shown in Figure 12, light retroreflected from the retroreflector 30 (retroreflected light Lx) is partially reflected by the reflecting mirror 1020 as parallel light and enters the vicinity of the eye of the observer 100. On the other hand, light reflected with a spread within a certain angular range centered on the retroreflection direction (angularly spread light Ly) is partially reflected by the reflecting mirror 1020 as non-parallel light and enters the vicinity of the eye of the observer 100 so as to overlap with the retroreflected light Lx. At this time, the angularly spread light Ly is imaged at a retinal position of the observer 100 that is shifted from the position where the retroreflected light Lx is imaged, resulting in focus degradation.

[0045] 13 shows the schematic configuration of a projection device 1000C that combines a pupil duplication device to enlarge the eyebox. In projection device 1000C that uses a pupil duplication device of the multiple pupil duplication type like pupil duplication device 60 described above, when pupil image 1010A (an image at a certain projection distance) with a light guide plate is incident on the eye of observer 100, and angularly divergent light Ly of adjacent pupil image 1010B (an image at a different projection distance) is incident on the eye of observer 100, the original pupil image 1010A and the adjacent pupil image 1010B overlap, causing greater focus degradation.

[0046] In contrast, in this embodiment, a condensing lens 40 is disposed between the reflecting mirror 20 and the retroreflector 30, and the retroreflector 30 is positioned at the focal length of the condensing lens 40. For example, substantially parallel light L emitted from a display device 10 disposed above an observer 100 and reflected by the reflecting mirror 20 is condensed onto the retroreflector 30 by the condensing lens 40. The light L reflected by the retroreflector 30 includes retroreflected light Lx and angularly divergent light Ly, which are reflected directly toward the optical axis of the incident light. However, the retroreflected light Lx and angularly divergent light Ly are returned to substantially parallel light by the condensing lens 40, as shown in FIG. 14 . As a result, the angularly divergent light Ly partially reflected by the reflecting mirror 1020 is incident on the periphery of the observer's eye without overlapping with light rays from adjacent pupil images, for example, thereby preventing focus degradation.

[0047] As a result, it is possible to provide a projection device that has a wide viewing angle and is capable of displaying a focused virtual image.

[0048] Furthermore, in the projection device 1 of this embodiment, the condensing lens 40 is disposed between the reflecting mirror 20 and the retroreflector 30, and the retroreflector 30 is positioned at the focal length position of the condensing lens 40, so that the light L condensed by the condensing lens 40 is incident on the retroreflector 30. Therefore, compared to the projection device 1000B in which the light L that is approximately parallel is incident on the retroreflector 1030, the retroreflector can be made smaller.

[0049] Furthermore, in the projection device 1A of this embodiment shown in FIG. 6 etc., for example, as shown in FIG. 8, by arranging a pupil duplicating device 60 that duplicates the pupil in the body axis direction (X-axis direction) and in the direction of both eyes (Y-axis direction) of the observer 100 at pupil position X of the display device 10A, it is possible to expand the eyebox in which the entire image can be viewed in the body axis direction and in the direction of both eyes of the observer 100.

[0050] Next, modifications 1 to 4 of the present disclosure will be described. In the following, the same components as those in the above embodiment will be given the same reference numerals, and the description thereof will be omitted as appropriate.

[0051] 2. Modifications (2-1. Modification 1) FIG. 15 illustrates a configuration example of a display device (display device 10B) according to Modification 1 of the present disclosure.

[0052] The projection device (e.g., projection device 1) of the present disclosure uses a display device that emits substantially parallel light, but by using an infinity focus projection lens 19A configured by combining multiple lenses as the projection optical system 19, for example, as shown in Fig. 15, the degree of parallelism of the projection light for each angle of view can be improved. This makes it possible to provide a projection device that can display a wide viewing angle and a more focused virtual image.

[0053] 16 illustrates a schematic configuration of a projection device (projection device 1B) according to Modification 2 of the present disclosure. Similar to the above embodiment, projection device 1B is used in a HUD system that displays speed, navigation, and the like to a driver in the front seat of a vehicle, and displays virtual images including driving support information and cautionary information using light reflected on the windshield.

[0054] In the above embodiment, an example was shown in which the collimator lens 41 was used as the condenser lens 40, but this is not limiting. The projection device 1B of this modified example uses a Fresnel lens 42, which is thinner than the collimator lens 41, as the condenser lens 40.

[0055] In this way, in this modified example, a Fresnel lens 42 is used as the condenser lens 40, so the size of the optical system can be reduced in the direction of the lens thickness spectral axis compared to a projection device 1 that uses a collimator lens 41.

[0056] 17 shows a schematic configuration of a projection device (projection device 1C) according to Modification 3 of the present disclosure. As in the above embodiment, projection device 1C is used in a HUD system that displays speed, navigation, and the like to a driver in the front seat of a vehicle, and displays virtual images including driving support information and attention-grabbing information using light reflected on the windshield.

[0057] In the above embodiment, an example was shown in which the collimating lens 41 was used as the condensing lens 40, but this is not limiting. The projection device 1C of this modified example uses a lens array 43 with a shorter focal length than the collimating lens 41 as the condensing lens 40.

[0058] In this way, in this modified example, a lens array 43 is used as the focusing lens 40, so the size of the optical system can be reduced in the focal length spectral axis direction compared to a projection device 1 that uses a collimating lens 41.

[0059] 18 illustrates a schematic configuration of a projection device (projection device 1D) according to Modification 4 of the present disclosure. Similar to the above-described embodiment, projection device 1D is used in a HUD system that displays speed, navigation, and the like to a driver in the front seat of a vehicle, and displays virtual images including driving support information and attention-grabbing information using light reflected on the windshield.

[0060] In the above embodiment, an example was shown in which a collimator lens 41 was used as the condenser lens 40, but the present invention is not limited to this. A projection device 1D of this modified example uses a concave mirror 44 as the condenser lens 40.

[0061] In this way, in this modified example, a concave mirror 44 is used as the focusing lens 40, so that the length of the optical system can be reduced by partially folding back the linear optical system compared to, for example, a projection device 1 that uses a collimating lens 41.

[0062] Although the present disclosure has been described above with reference to the embodiment and modifications 1 to 4, various modifications are possible without being limited to the above-described embodiment, etc. For example, the arrangement and number of components of the optical system exemplified in the above-described embodiment, etc. are merely examples, and it is not necessary to include all of the components, and other components may also be included.

[0063] For example, in the above-described embodiments, examples have been given in which a projection type display device is used as the display device, but the present invention is not limited to this, and for example, a flat panel display can also be used.

[0064] The effects described in this specification are merely examples and are not limited to those described, and other effects may also be obtained.

[0065] The present technology can also be configured as follows. According to the present technology configured as follows, light focused by a focusing lens is incident on the retroreflector. Therefore, even if there is angular spread of the returned light emitted from the retroreflector, the light is converted into approximately parallel light by the focusing lens arranged at the focal length position, and the spread of the returned light emitted from the retroreflector 30 is substantially reduced. Therefore, it is possible to provide a projection device capable of displaying a wide FOV and a focused virtual image. (1) A projection device comprising: a display device; a reflecting mirror that reflects light emitted from the display device in a predetermined direction; one or more focusing lenses; and a retroreflector arranged at the focal length position of the focusing lens and reflecting the light incident via the reflecting mirror and the focusing lens in the incident direction. (2) The projection device described in (1) above, in which the focusing lens is arranged between the reflecting mirror and the retroreflector. (3) The projection device according to (1) or (2), wherein the X-axis direction is the body axis direction of a human and the Y-axis direction is the direction of both eyes, and further comprises a pupil duplicating device that duplicates a pupil conjugate point in at least one of the Y-axis direction and the X-axis direction. (4) The projection device according to (3), wherein the pupil duplicating device is disposed between the display device and the reflecting mirror. (5) The projection device according to (3) or (4), wherein the pupil duplicating device is a light guide plate configured with a first half mirror group including a plurality of half mirrors arranged in the X-axis direction and a second half mirror group including a plurality of half mirrors arranged in the Y-axis direction. (6) The projection device according to any one of (1) to (5), wherein the condensing lens is a Fresnel lens. (7) The projection device according to any one of (1) to (5), wherein the condensing lens is a lens array. (8) The projection device according to any one of (1) to (5), wherein the condensing lens is a concave mirror. (9) The projection device according to any one of (1) to (8), wherein the display device emits substantially parallel light. (10) The projection device according to any one of (1) to (8), wherein the display device includes an infinity focus projection lens.(11) The projection device according to any one of (1) to (10), further comprising a transparent plate arranged on the optical path of the light emitted from the display device. (12) The projection device according to (11), wherein the reflecting mirror is the transparent plate, and the display device, the condensing lens, and the retroreflector are arranged on one side of the reflecting mirror. (13) The projection device according to (12), wherein the transparent plate is the windshield of a vehicle, and the display device, the condensing lens, and the retroreflector are arranged inside the vehicle. (14) The projection device according to any one of (11) to (13), wherein the display device and the reflecting mirror are arranged on one side of the transparent plate, and the condensing lens and the retroreflector are arranged on the other side of the transparent plate. (15) The projection device according to (14), wherein the transparent plate is the windshield of a vehicle, and the display device and the reflecting mirror are arranged outside the vehicle, and the condensing lens and the retroreflector are arranged inside the vehicle.

[0066] This application claims priority based on Japanese Patent Application No. 2024-031600, filed on March 1, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0067] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. A projection device comprising: a display device; a reflecting mirror that reflects light emitted from the display device in a predetermined direction; one or more condensing lenses; and a retroreflector that is positioned at the focal length of the condensing lenses and reflects the light that has entered through the reflecting mirror and the condensing lenses in the direction of incidence.

2. The projection device according to claim 1, wherein the condenser lens is disposed between the reflecting mirror and the retroreflector.

3. The projection device according to claim 1, further comprising a pupil duplicating device that duplicates a pupil conjugate point in at least one of the Y-axis direction and the X-axis direction, with the X-axis direction being the direction of the human body axis and the Y-axis direction being the direction of both eyes.

4. The projection device according to claim 3, wherein the pupil replicating device is disposed between the display device and the reflecting mirror.

5. The projection device according to claim 3, wherein the pupil duplication device is a light guide plate composed of a first half mirror group including a plurality of half mirrors arranged in the X-axis direction, and a second half mirror group including a plurality of half mirrors arranged in the Y-axis direction.

6. The projection device of claim 1, wherein the condenser lens is a Fresnel lens.

7. The projection device of claim 1, wherein the condenser lens is a lens array.

8. The projection device of claim 1, wherein the condenser lens is a concave mirror.

9. The projection device according to claim 1, wherein the display device emits substantially parallel light.

10. The projection device of claim 1, wherein the display device includes an infinity focus projection lens.

11. The projection device according to claim 1, further comprising a transparent plate disposed on the optical path of the light emitted from the display device.

12. The projection device according to claim 11, wherein the reflecting mirror is the transparent plate, and the display device, the condensing lens, and the retroreflector are arranged on one surface side of the reflecting mirror.

13. The projection device according to claim 12, wherein the transparent plate is a windshield of a vehicle, and the display device, the condensing lens, and the retroreflector are disposed inside the vehicle.

14. The projection device according to claim 11, wherein the display device and the reflecting mirror are disposed on one side of the transparent plate, and the condenser lens and the retroreflector are disposed on the other side of the transparent plate.

15. The projection device according to claim 14, wherein the transparent plate is a windshield of a vehicle, the display device and the reflecting mirror are disposed outside the vehicle, and the condensing lens and the retroreflector are disposed inside the vehicle.

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