Image display device

Abstract

To provide an image display device which can enhance the utilization efficiency of light.SOLUTION: An image display device comprises: a hologram light guide plate 22; and a display light generation unit which makes two type of display light with mutually-different polarization directions incident on an incident area A11 of the hologram light guide plate 22. The hologram light guide plate 22 comprises: a first emission area A22 which has a hologram 322 that forms an image with display light in a first polarization direction; a second emission area A32 which has a hologram 332 that forms an image with display light in a second polarization direction; and a distribution area A12 which has a polarization-dependent hologram 312, guides the display light in the first polarization direction in the two types of display light incident from the incident area A11 to the first emission area A22 and guides the display light in the second polarization direction to the second emission area A32.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image display device that displays an image, and is suitable for being mounted on a moving body such as a passenger car. [Background technology]

[0002] In recent years, image display devices called head-up displays have been developed and are being installed in vehicles such as passenger cars. In head-up displays installed in passenger cars, light modulated by image information is projected onto the windshield (front glass), and the reflected light is irradiated onto the driver's eyes. This allows the driver to see a virtual image in front of the windshield. For example, drive assist information such as vehicle speed, various warning markers, and an arrow indicating the direction of travel of the passenger car are displayed as virtual images.

[0003] The following Patent Document 1 describes an optical system including a light source, three beam splitters, three shutters, and three LOEs (e.g., planar waveguides). A beam from the light source is split into three beams by the three beam splitters. The three beams propagate along the three LOEs, respectively, and are emitted from the optical system. At this time, two of the three beams are selectively blocked by the shutters, and the remaining beam is emitted from the optical system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-56535 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration of Patent Document 1, two of the three beams are blocked by the shutter, which reduces the efficiency of use of light emitted from the light source.

[0006] In view of the above problem, an object of the present invention is to provide an image display device that can improve the light utilization efficiency. [Means for solving the problem]

[0007] An image display device according to a main aspect of the present invention includes a holographic light guide plate and a display light generating unit that causes multiple types of display light, each having different states in terms of predetermined optical characteristics, to enter an entrance region of the holographic light guide plate. The holographic light guide plate includes a first exit region having a hologram that forms an image of a first type of the display light, a second exit region having a hologram that forms an image of a second type of the display light, and a distribution region having a hologram depending on the optical characteristics, and that guides the first type of display light to the first exit region and the second type of display light to the second exit region, of the multiple types of display light incident from the entrance region.

[0008] In the image display device according to this aspect, when a first type of display light enters from the entrance region, the display light is guided to the first exit region by the distribution region, and when a second type of display light enters from the entrance region, the display light is guided to the second exit region by the distribution region. This improves the utilization efficiency of each type of display light. Furthermore, this distribution of display light can be achieved simply by arranging a distribution region having a hologram dependent on optical characteristics in a holographic light guide plate. This prevents the holographic light guide plate from becoming too complicated and large, thereby simplifying the image display device and reducing costs. [Effects of the Invention]

[0009] As described above, according to the present invention, it is possible to provide an image display device that can improve the light utilization efficiency.

[0010] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below. [Brief explanation of the drawings]

[0011] [Figure 1] 1(a) and 1(b) are diagrams each showing a schematic view of a usage form of an image display device according to embodiment 1. FIG. 1(c) is a diagram showing a schematic view of a configuration of the image display device according to embodiment 1. [Figure 2] FIG. 2 is a diagram schematically illustrating the configuration of a display light generating unit of the image display device and the configuration of a circuit used in the display light generating unit according to the first embodiment. [Figure 3] FIG. 3 is a perspective view schematically showing the configuration of the holographic light guide plate according to the first embodiment. [Figure 4] FIG. 4 is a plan view schematically showing the configuration of the holographic light guide plate according to the first embodiment. [Figure 5] FIG. 5 is a timing chart schematically showing the driving of the laser light source, the spatial light modulator, and the actuator of the half-wave plate according to the first embodiment. [Figure 6] FIG. 6 is a diagram schematically illustrating a near-distance image and a far-distance image of a virtual image formed in a space in front of a projection area according to the first embodiment. [Figure 7] 7(a) and 7(b) are diagrams schematically showing a close-range image of a virtual image formed in the space in front of the projection area according to the first modification. [Figure 8] 8(a) and 8(b) are diagrams schematically showing a close-range image of a virtual image formed in the space in front of the projection area according to the second modification. [Figure 9] FIG. 9 is a perspective view schematically illustrating the configuration of a holographic light guide plate according to the second embodiment. [Figure 10] FIG. 10 is a plan view schematically showing the configuration of a holographic light guide plate according to the second embodiment. [Figure 11] FIG. 11 is a timing chart schematically showing the driving of the laser light source and the spatial light modulator according to the second embodiment. [Figure 12] FIG. 12 is a diagram schematically illustrating a near-distance image and a far-distance image of a virtual image formed in a space in front of a projection area according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, mutually orthogonal X, Y, and Z axes are appropriately indicated in each drawing.

[0013] <Embodiment 1> 1(a) and 1(b) are diagrams showing a typical usage of the image display device 20. Fig. 1(a) is a schematic diagram showing the interior of the passenger car 1 seen from the side of the passenger car 1, and Fig. 1(b) is a diagram showing the front of the passenger car 1 in the direction of travel from the inside of the passenger car 1.

[0014] In this embodiment, the present invention is applied to an in-vehicle head-up display. As shown in Fig. 1(a), an image display device 20 is installed inside a dashboard 11 of a passenger car 1.

[0015] As shown in FIGS. 1(a) and 1(b), the image display device 20 projects display light modulated by a video signal onto a projection area 13 located under the windshield 12 near the driver's seat. The projected display light is reflected by the projection area 13 and irradiated onto a horizontally elongated area (eye box area) around the eyes of the driver 2. As a result, a predetermined image 30 is displayed as a virtual image in the driver's field of vision ahead. The driver 2 can see the virtual image 30 superimposed on the view ahead of the windshield 12. In other words, the image display device 20 forms the virtual image 30 in the space ahead of the projection area 13 on the windshield 12.

[0016] FIG. 1( c ) is a diagram showing a schematic configuration of the image display device 20 .

[0017] The image display device 20 includes a display light generation unit 21 and a holographic light guide plate 22. The display light generation unit 21 generates display light modulated by a video signal and emits the generated display light. The holographic light guide plate 22 propagates the display light emitted from the display light generation unit 21 and guides it to the projection area 13 on the windshield 12. The display light reflected by the windshield 12 is irradiated onto the eye 2a of the driver 2. The optical system of the display light generation unit 21 and the holographic light guide plate 22 are designed so that a virtual image 30 is displayed at a predetermined size in front of the windshield 12.

[0018] FIG. 2 is a diagram schematically illustrating the configuration of the display light generating unit 21 of the image display device 20 and the configuration of a circuit used in the display light generating unit 21. As shown in FIG.

[0019] The display light generation unit 21 includes a light source 101, a temperature sensor 102, collimator lenses 103a to 103c, apertures 104a to 104c, a mirror 105, dichroic mirrors 106a and 106b, a polarizing beam splitter 107, a spatial light modulator 108, and a half-wave plate 109.

[0020] The light source 101 includes three laser light sources 101a, 101b, and 101c.

[0021] The laser light source 101a emits a laser light with a red wavelength in the range of 635 nm to 645 nm in accordance with a drive signal. The laser light source 101b emits a laser light with a green wavelength in the range of 510 nm to 530 nm in accordance with a drive signal. The laser light source 101c emits a laser light with a blue wavelength in the range of 440 nm to 460 nm in accordance with a drive signal.

[0022] In this embodiment, the light source 101 includes these three laser light sources 101a, 101b, and 101c to display a color image as the image 30. The laser light sources 101a, 101b, and 101c are, for example, semiconductor lasers. When a monochromatic image is displayed as the image 30, the light source 101 may include only one laser light source corresponding to the color of the image. Alternatively, the light source 101 may be configured to include two laser light sources with different emission wavelengths.

[0023] The laser light sources 101a, 101b, and 101c are mounted on a single circuit board 110, and a temperature sensor 102 is mounted on the circuit board 110 to detect the temperature (environmental temperature) around the installation positions of the laser light sources 101a, 101b, and 101c. The temperature sensor 102 is mounted in the vicinity of the laser light source 101a, which emits laser light with a red wavelength. In other words, the temperature sensor 102 is disposed in a position closer to the laser light source 101a than the other two laser light sources 101b and 101c. A temperature sensor may be disposed for each of the laser light sources 101a, 101b, and 101c.

[0024] The laser beams emitted from the laser light sources 101a, 101b, and 101c are converted into parallel beams by collimator lenses 103a to 103c, respectively. The laser beams transmitted through the collimator lenses 103a to 103c are shaped by apertures 104a to 104c into beams having the shape (rectangular) of the modulation region of the spatial light modulator 108. In other words, the apertures 104a to 104c constitute a beam shaping unit for aligning the beam size and beam shape of the laser beams emitted from the laser light sources 101a, 101b, and 101c, respectively.

[0025] It should be noted that, instead of the collimator lenses 103a to 103c, shaping lenses may be used that shape and collimate the laser light into a beam having the shape (rectangular) of the modulation region of the spatial light modulator 108. In this case, the apertures 104a to 104c may be omitted.

[0026] Thereafter, the optical axes of the laser beams of each color emitted from the laser light sources 101a, 101b, and 101c are aligned by a mirror 105 and two dichroic mirrors 106a and 106b. The mirror 105 almost totally reflects the red laser beam that has passed through the collimator lens 103a. The dichroic mirror 106a reflects the green laser beam that has passed through the collimator lens 103b and transmits the red laser beam reflected by the mirror 105. The dichroic mirror 106b transmits the blue laser beam that has passed through the collimator lens 103c and reflects the red laser beam and green laser beam that have passed through the dichroic mirror 106a. The mirror 105 and the two dichroic mirrors 106a and 106b are arranged to align the optical axes of the laser beams of each color emitted from the laser light sources 101a, 101b, and 101c.

[0027] The laser light sources 101a, 101b, and 101c are arranged so that the polarization direction of the laser light of each color incident on the polarizing beam splitter 107 becomes S-polarized light.

[0028] The polarizing beam splitter 107 has a polarizing surface 107a that reflects S-polarized light and transmits P-polarized light. The laser light of each color that has passed through the dichroic mirror 106b is reflected by the polarizing surface 107a of the polarizing beam splitter 107 and is guided to the spatial light modulator 108.

[0029] The spatial light modulator 108 is configured, for example, by LCOS (Liquid Crystal On Silicon). The spatial light modulator 108 modulates the light of each color reflected by the polarization surface 107a in accordance with a drive signal to generate display light that is the basis of the image 30. At this time, the rotation angle of the polarization direction of the laser light of each color is adjusted for each pixel to an angle corresponding to the luminance of the pixel. As a result, the amount of light that passes through the polarization surface 107a of the laser light of each color traveling from the spatial light modulator 108 to the polarizing beam splitter 107 is adjusted for each pixel. In this way, display light corresponding to the drawn image is generated by the P-polarized laser light of each color that passes through the polarization surface 107a.

[0030] The half-wave plate 109 changes the polarization direction of the display light incident from the polarizing beam splitter 107. The actuator 109a rotates the half-wave plate 109 around the optical axis. Specifically, the actuator 109a changes the rotation position of the half-wave plate 109 between two positions in response to a drive signal. As a result, the display light transmitted through the half-wave plate 109 is set to a first polarization direction or a second polarization direction. For example, the second polarization direction is a direction rotated 90° relative to the first polarization direction. The display light whose polarization direction has been set by the half-wave plate 109 in this way enters the holographic light guide plate 22.

[0031] Polarization-dependent holograms are formed in a plurality of regions in holographic light guide plate 22. Due to the holograms in these regions, holographic light guide plate 22 emits display light of a first polarization direction and display light of a second polarization direction, which are incident from the half-wave plate 109 side, from different emission regions. The display light emitted from holographic light guide plate 22 is irradiated onto windshield 12 (see FIGS. 1(a) to 1(c)). The configuration of holographic light guide plate 22 will be described later with reference to FIGS. 3 and 4.

[0032] The image control circuit 201 includes an arithmetic processing unit such as a CPU or FPGA, and a memory, and processes the input video signal to control the laser drive circuit 202, the display drive circuit 203, and the actuator drive circuit 204. Furthermore, based on the detection result of the temperature sensor 102, the image control circuit 201 controls the output power of the light source 101 via the laser drive circuit 202 to set the brightness of the display light so as to suppress a decrease in the brightness of the image 30 (see FIG. 1(c)).

[0033] The laser drive circuit 202 drives the laser light sources 101a, 101b, and 101c in response to a control signal input from the image control circuit 201. The display drive circuit 203 drives the spatial light modulator 108 in response to a control signal input from the image control circuit 201. The actuator drive circuit 204 drives the actuator 109a in response to a control signal input from the image control circuit 201.

[0034] Next, the configuration of the holographic light guide plate 22 will be described with reference to FIGS.

[0035] Fig. 3 is a perspective view schematically showing the configuration of holographic light guide plate 22. For convenience, in Fig. 3, the X, Y, and Z axis directions of holographic light guide plate 22 correspond to the left-right direction, the front-rear direction, and the up-down direction.

[0036] Holographic light guide plate 22 includes light guide path 301, one hologram 311, a pair of holograms 312, a pair of holograms 321, a pair of holograms 322, a pair of holograms 331, and a pair of holograms 332. Holographic light guide plate 22 is provided with an entrance region A11, a distribution region A12, a propagation region A21, a first exit region A22, a propagation region A31, and a second exit region A32.

[0037] The light guide 301 is made of a transparent flat glass plate. However, instead of a glass plate, the light guide 301 may be made of a transparent flat resin plate.

[0038] Hologram 311 is disposed on the lower surface of light guide 301 at the center of the front end. A pair of holograms 312 are disposed on the upper and lower surfaces of light guide 301 immediately behind hologram 311, and are disposed at the same positions relative to each other in a planar view. A pair of holograms 321 are disposed on the upper and lower surfaces of light guide 301 immediately to the left of pair of holograms 312, and are disposed at the same positions relative to each other in a planar view. A pair of holograms 322 are disposed on the upper and lower surfaces of light guide 301 immediately behind pair of holograms 321, and are disposed at the same positions relative to each other in a planar view. A pair of holograms 331 are disposed on the upper and lower surfaces of light guide 301 immediately behind pair of holograms 312, and are disposed at the same positions relative to each other in a planar view. A pair of holograms 332 are disposed on the upper and lower surfaces of light guide 301 immediately to the right of pair of holograms 331, and are disposed at the same positions relative to each other in a planar view.

[0039] Hologram 311 has a square shape. Pair of holograms 312 also have a square shape and are the same size as hologram 311. Pair of holograms 321 have a length in the short side direction (front-to-back direction) that is the same as the length of one side of hologram 312. Pair of holograms 322 have a square shape and a length of one side that is the same as the length of hologram 321 in the long side direction (left-to-right direction). Pair of holograms 331 have a length in the short side direction (left-to-right direction) that is the same as the length of one side of hologram 312, and a length in the long side direction (front-to-back direction) that is the same as the length of one side of hologram 322. Pair of holograms 332 have a square shape and are the same size as hologram 322.

[0040] The entrance region A11 includes a hologram 311 and a light guide path 301 at the position of the hologram 311. The distribution region A12 includes a pair of holograms 312 and a light guide path 301 between the pair of holograms 312. The propagation region A21 includes a pair of holograms 321 and a light guide path 301 between the pair of holograms 321. The first exit region A22 includes a pair of holograms 322 and a light guide path 301 between the pair of holograms 322. The propagation region A31 includes a pair of holograms 331 and a light guide path 301 between the pair of holograms 331. The second exit region A32 includes a pair of holograms 332 and a light guide path 301 between the pair of holograms 332. The display light from the half-wave plate 109 enters the entrance region A11 in an upward direction.

[0041] Fig. 4 is a plan view schematically showing the configuration of holographic light guide plate 22. For convenience, Fig. 4 shows polarization beam splitter 107, spatial light modulator 108, and half-wave plate 109, which are located below holographic light guide plate 22 (in the negative direction of the Z axis), as viewed in the positive direction of the X axis.

[0042] The hologram 311 is configured to diffract the display light of the first polarization direction and the display light of the second polarization direction backward, so that the incident area A11 propagates the display light incident from the half-wave plate 109 to the distribution area A12.

[0043] The pair of holograms 312 are configured so that the diffraction efficiency is highest in the first polarization direction and lowest in the second polarization direction. The diffraction direction of the pair of holograms 312 is leftward. As a result, the distribution region A12 propagates, of the display light from the entrance region A11, the display light having the first polarization direction to the propagation region A21 and the display light having the second polarization direction to the propagation region A31. The pair of holograms 312 are also configured so that the display light having the first polarization direction heading toward the propagation region A21 is diffused in the left-right direction, and the display light having the second polarization direction heading toward the propagation region A31 is diffused in the front-rear direction.

[0044] The pair of holograms 321 are configured to maximize the diffraction efficiency in the first polarization direction. The diffraction direction of the pair of holograms 321 is backward. As a result, the propagation region A21 propagates the display light in the first polarization direction from the distribution region A12 to the first exit region A22. The pair of holograms 321 are also configured to diffuse the display light in the first polarization direction heading toward the first exit region A22 in the forward and backward directions.

[0045] The pair of holograms 322 are configured so that the diffraction efficiency in the first polarization direction is maximized and the display light in the first polarization direction from the propagation region A21 is emitted from the entire first emission region A22. As a result, the first emission region A22 causes the display light in the first polarization direction from the propagation region A21 to exit from the holographic light guide plate 22 in the positive direction of the Z axis and guide it to the projection region 13 (see FIG. 1(b)).

[0046] The diffraction pattern formed on the hologram 322 has a lens effect that causes the display light emitted from the first emission region A22 to form an image at a short distance, so that the display light emitted from the first emission region A22 is irradiated onto the projection region 13 as short-distance display light, and forms an image corresponding to a short distance.

[0047] The pair of holograms 331 are configured to maximize the diffraction efficiency in the second polarization direction. The diffraction direction of the pair of holograms 331 is the rightward direction. As a result, the propagation region A31 propagates the display light in the second polarization direction from the distribution region A12 to the second exit region A32. The pair of holograms 331 are also configured to diffuse the display light in the second polarization direction heading toward the second exit region A32 in the left-right direction.

[0048] The pair of holograms 332 are configured so that the diffraction efficiency in the second polarization direction is maximized and the display light in the second polarization direction from the propagation region A31 is emitted from the entire second emission region A32. As a result, the second emission region A32 causes the display light in the second polarization direction from the propagation region A31 to exit the holographic light guide plate 22 in the positive direction of the Z axis and guide it to the projection region 13 (see FIG. 1(b)).

[0049] Furthermore, the diffraction pattern formed on the hologram 332 has a lens effect that causes the display light emitted from the second emission area A32 to form an image at a long distance, so that the display light emitted from the second emission area A32 is irradiated onto the projection area 13 as long-distance display light, and an image corresponding to a long distance is formed.

[0050] In addition, if an optical system such as a lens is further disposed between the hologram light guide plate 22 and the windshield 12, the holograms 322, 332 may be set with a diffraction pattern that, in combination with the optical action of this optical system, focuses the display light at a predetermined distance.

[0051] FIG. 5 is a timing chart that schematically shows the driving of the laser light sources 101a, 101b, and 101c, the spatial light modulator 108, and the actuator 109a of the half-wave plate 109. In FIG.

[0052] The image control circuit 201 alternately sets a short distance display period T1 in which short distance display light is emitted from the first emission region A22 and a long distance display period T2 in which long distance display light is emitted from the second emission region A32.

[0053] During the near-distance display period T1, the image control circuit 201 controls the actuator 109a via the actuator drive circuit 204 to set the half-wave plate 109 to a first position. The first position is a position where the display light transmitted through the half-wave plate 109 has a first polarization direction. During the near-distance display period T1, the image control circuit 201 controls the laser light sources 101a, 101b, and 101c via the laser drive circuit 202 to emit red laser light during period T11, green laser light during period T12, and blue laser light during period T13. The image control circuit 201 controls the spatial light modulator 108 via the display drive circuit 203 to modulate the red laser light, green laser light, and blue laser light, respectively, during periods T11, T12, and T13.

[0054] As a result, during the near-distance display period T1, display light based on red laser light in the first polarization direction, display light based on green laser light in the first polarization direction, and display light based on blue laser light in the first polarization direction form one frame of a near-distance image corresponding to the near distance.

[0055] During the long-distance display period T2, the image control circuit 201 controls the actuator 109a via the actuator drive circuit 204 to set the half-wave plate 109 to a second position. The second position is a position where the display light transmitted through the half-wave plate 109 has a second polarization direction. During the long-distance display period T2, the image control circuit 201 controls the laser light sources 101a, 101b, and 101c via the laser drive circuit 202 to emit red laser light in period T21, green laser light in period T22, and blue laser light in period T23. The image control circuit 201 controls the spatial light modulator 108 via the display drive circuit 203 to emit red laser light in period T21, green laser light in period T22, and blue laser light in period T23. light , modulating the green laser light and the blue laser light.

[0056] As a result, during the long distance display period T2, the display light based on the red laser light in the second polarization direction, the display light based on the green laser light in the second polarization direction, and the display light based on the blue laser light in the second polarization direction form one frame of a long distance image corresponding to the long distance.

[0057] FIG. 6 is a diagram schematically showing a near-distance image 401 and a far-distance image 402 of a virtual image formed in the space in front of the projection area 13. As shown in FIG.

[0058] Close-up image 401 and long-distance image 402 are displayed as virtual images at positions farther from projection area 13 as viewed by driver 2. Close-up image 401 displays the speed of passenger vehicle 1 at a position close to projection area 13. Long-distance image 402 displays the next direction in which passenger vehicle 1 should travel, aligned with the surface of the road at a position farther from projection area 13. This allows driver 2 to check the speed and direction of travel while keeping his or her eyes fixed on the road conditions ahead, without having to look down to look at the speedometer display or car navigation system display installed inside dashboard 11.

[0059] <Effects of the First Embodiment> According to this embodiment, the following effects are achieved.

[0060] The display light generation unit 21 causes two types of display light having different polarization directions to enter the entrance region A11 of the holographic light guide plate 22. The first exit region A22 has a hologram 322 that forms an image of the display light in the first polarization direction (first type), and the second exit region A32 has a hologram 332 that forms an image of the display light in the second polarization direction (second type). The distribution region A12 has a polarization-dependent hologram 312, and guides the display light in the first polarization direction (first type) of the two types of display light incident from the entrance region A11 to the first exit region A22 and the display light in the second polarization direction (second type) to the second exit region A32.

[0061] According to this configuration, when display light having a first polarization direction enters from the entrance region A11, the display light is guided by the distribution region A12 to the first exit region A22, and when display light having a second polarization direction enters from the entrance region A11, the display light is guided by the distribution region A12 to the second exit region A32. This improves the utilization efficiency of the display light of each polarization direction. When the utilization efficiency of the display light is improved, the output to the light source 101 can be reduced, thereby reducing heat generation, deterioration, power consumption, etc. of the laser light sources 101a, 101b, and 101c.

[0062] Moreover, such distribution of display light can be achieved simply by arranging distribution region A12 having polarization-dependent hologram 312 in holographic light guide plate 22. This prevents holographic light guide plate 22 from becoming too complicated and large, thereby simplifying image display device 20 and reducing costs.

[0063] The first type of display light generated in the display light generation unit 21 has a first polarization direction, and the second type of display light generated in the display light generation unit 21 has a second polarization direction. With this configuration, the difference in the polarization direction of the display light can be utilized to smoothly guide the two types of display light to the first exit region A22 and the second exit region A32, respectively.

[0064] The display light generation unit 21 includes a half-wave plate 109 (optical element) for switching the polarization direction of the display light from the polarizing beam splitter 107 between the first polarization direction and the second polarization direction. This configuration makes it possible to generate two types of display light having different polarization directions with a simple configuration.

[0065] The half-wave plate 109 includes an actuator 109a that rotates the half-wave plate 109 around the optical axis. With this configuration, two types of display light having different polarization directions can be easily generated by rotating the half-wave plate 109 around the optical axis using the actuator 109a.

[0066] Hologram 312 in distribution area A12 is configured to have the highest diffraction efficiency in the first polarization direction and the lowest diffraction efficiency in the second polarization direction. This configuration allows display light in the first polarization direction and display light in the second polarization direction to be efficiently guided to first exit area A22 and second exit area A32, respectively.

[0067] Hologram 322 in first exit region A22 is configured to have the highest diffraction efficiency in the first polarization direction, and hologram 332 in second exit region A32 is configured to have the highest diffraction efficiency in the second polarization direction. With this configuration, display light in the first polarization direction and display light in the second polarization direction can be efficiently emitted from first exit region A22 and second exit region A32, respectively.

[0068] The first and second emission regions A22 and A32 focus the display light of the first polarization direction and the display light of the second polarization direction at different positions. This configuration allows multiple types of images to be displayed. Furthermore, by setting the holograms of the first and second emission regions A22 and A32 so that the distances to the image-focusing positions of the display lights are different, multiple types of images with different viewing distances can be displayed. This allows the speed of the passenger vehicle 1 to be clearly displayed using the close-distance image 401, and the direction of travel along the road to be clearly displayed using the long-distance image 402.

[0069] <Change example 1> In the first embodiment, the holograms 322, 332 of the first and second emission regions A22, A32 are configured to focus the display light at positions at different viewing distances, but they may be configured to focus the display light at positions at the same viewing distance. For example, the second emission region A32 may have a diffraction effect that focuses the display light at a short distance, similar to the first emission region A22.

[0070] FIG. 7(a) is a diagram schematically showing a close-distance virtual image 411 formed in the space in front of the projection area 13 according to the first modification.

[0071] In Modification 1, similar to Embodiment 1, a close-up image 411 indicating the speed of the passenger vehicle 1 is displayed based on the close-up display light emitted from the first emission area A22. However, in Modification 1, the process of generating the close-up image 411 is also executed during the long-distance display period T2 in Fig. 5. As a result, the display shown in Fig. 7(a) is basically performed.

[0072] FIG. 7(b) is a diagram schematically showing a virtual close-distance image 412 formed in the space in front of the projection area 13 according to the first modification.

[0073] In Modification 1, image control circuit 201 determines whether or not the speed of passenger car 1 has exceeded the speed limit (for example, whether or not the speed is 80 km / h or greater) based on a speed signal from passenger car 1. If the speed of passenger car 1 has exceeded the speed limit, image control circuit 201 displays close-up image 412 indicating the speed of passenger car 1 based on close-up display light emitted from second emission area A32, instead of displaying close-up image 411. In Modification 1, hologram 332 in second emission area A32 has a diffraction effect that causes display light to form an image at a close distance, similar to first emission area A22, so close-up images 411 and 412 are images formed at the same close distance. Furthermore, hologram 332 in second emission area A32 is configured so that close-up image 412 is larger than close-up image 411.

[0074] According to Modification 1, similarly to Embodiment 1, the driver 2 can normally always check the speed of the passenger vehicle 1 using the close-up image 411. Furthermore, when the driver 2 is speeding, the driver 2 can check the speed of the passenger vehicle 1 on a large display using the close-up image 412, so that the driver can be sure that the driver is speeding.

[0075] Note that close-up image 412 does not necessarily have to display a specific speed, but may instead display a statement or an icon indicating that the speed limit has been exceeded. Close-up image 412 may also be displayed in a color suitable for displaying a warning, such as solid red. Close-up image 412 does not necessarily have to be displayed in the same position as close-up image 411, but may also be displayed in a position different from close-up image 411.

[0076] <Change example 2> In the first modified example, close-up image 411 is displayed under normal circumstances, and close-up image 412 is displayed instead of close-up image 411 when speeding, but two close-up images may be displayed simultaneously when certain conditions are met.

[0077] 8(a) is a diagram schematically illustrating a virtual close-up image 421 formed in the space in front of the projection area 13 according to Modification Example 2. In Modification Example 2, a close-up image 421 similar to the close-up image 411 of Modification Example 1 is always displayed.

[0078] FIG. 8(b) shows a second modified example. , throw 4 is a diagram showing a schematic diagram of close-distance virtual images 421 and 422 formed in the space in front of the projection area 13.

[0079] In the second modification, the image control circuit 201 determines whether or not a predetermined condition is satisfied based on various signals from the passenger vehicle 1. Examples of the predetermined condition include detection of drowsiness in the driver 2 from an image captured by an in-vehicle camera or the like, or the duration of driving the passenger vehicle 1 exceeding a predetermined time. When drowsiness in the driver 2 is detected or when the duration of driving the passenger vehicle 1 exceeds the predetermined time, the image control circuit 201 displays, in addition to the close-up image 421, a close-up image 422 indicating that the predetermined condition is satisfied.

[0080] 8(b), a message encouraging the driver to take a rest is displayed as close-up image 422 when drowsiness of driver 2 is detected. In Modification Example 2, second emission area A32 is configured so that close-up image 422 is approximately the same size as close-up image 421.

[0081] According to the second modification, the driver 2 can always check the speed of the passenger vehicle 1 using the close-up image 421. Furthermore, when a predetermined condition is met, such as when drowsiness is detected or when the driving duration exceeds a predetermined time, the driver 2 can confirm that the predetermined condition has been met using the close-up image 422, which can be useful for safe driving.

[0082] <Embodiment 2> In the first embodiment, the display light having a first polarization direction is emitted from the first emission region A22, and the display light having a second polarization direction is emitted from the second emission region A32, depending on the polarization direction of the display light. In contrast, in the second embodiment, the display light of red laser light is emitted from the first emission region A52, the display light of green laser light is emitted from the second emission region A62, and the display light of blue laser light is emitted from the third emission region A72, depending on the wavelength of the display light. In the holographic light guide plate 22 of the second embodiment, wavelength-dependent holograms are formed in a plurality of regions.

[0083] FIG. 9 is a perspective view schematically showing the configuration of a holographic light guide plate 22 according to the second embodiment.

[0084] Holographic light guide plate 22 of embodiment 2 includes light guide path 501, one hologram 511, a pair of holograms 512, a pair of holograms 513, a pair of holograms 521, a pair of holograms 522, a pair of holograms 531, a pair of holograms 532, a pair of holograms 541, and a pair of holograms 542. Holographic light guide plate 22 is provided with an entrance region A41, a distribution region A42, a distribution region A43, a propagation region A51, a first exit region A52, a propagation region A61, a second exit region A62, a propagation region A71, and a third exit region A72.

[0085] The light guide 501 is made of a transparent, flat glass plate. However, the light guide 501 may be made of a transparent, flat resin plate instead of a glass plate.

[0086] Hologram 511 is placed on the lower surface near the front end and in the center of light guide path 501. A pair of holograms 512 are placed on the upper and lower surfaces of light guide path 501 adjacent to and behind hologram 511, and are placed at the same positions as each other in a plan view. A pair of holograms 513 are placed on the upper and lower surfaces of light guide path 501 adjacent to and behind hologram 512, and are placed at the same positions as each other in a plan view.

[0087] The pair of holograms 521 are disposed on the upper and lower surfaces of the light guide 501 to the left of the pair of holograms 512, and are disposed at the same positions as each other in a planar view. The pair of holograms 522 are disposed on the upper and lower surfaces of the light guide 501 in front of the pair of holograms 521, and are disposed at the same positions as each other in a planar view. The pair of holograms 531 are disposed on the upper and lower surfaces of the light guide 501 behind the pair of holograms 513, and are disposed at the same positions as each other in a planar view. The pair of holograms 532 are disposed on the upper and lower surfaces of the light guide 501 to the right of the pair of holograms 531, and are disposed at the same positions as each other in a planar view. The pair of holograms 541 are disposed on the upper and lower surfaces of the light guide 501 to the left of the pair of holograms 513, and are disposed at the same positions as each other in a planar view. The pair of holograms 542 are disposed on the upper and lower surfaces of the light guide 501 adjacent to the rear of the pair of holograms 541, and are disposed at the same positions as each other in a plan view.

[0088] Hologram 511 has a square shape. Pair of holograms 512 and 513 also have a square shape and are the same size as hologram 511. Pair of holograms 521 have a length in the short side direction (front-to-back direction) that is the same as the length of one side of hologram 512. Pair of holograms 522 have a square shape and a length of one side that is the same as the length of hologram 521 in the long side direction (left-to-right direction). Pair of holograms 531 have a length in the short side direction (left-to-right direction) that is the same as the length of one side of hologram 513, and a length in the long side direction (front-to-back direction) that is the same as the length of one side of hologram 522. Pair of holograms 532 have a square shape and are the same size as hologram 522. Pair of holograms 541 have a length in the short side direction ( Front and rear The length of the longitudinal direction ( left and right The length of the pair of holograms 542 (in the direction) is the same as the length of one side of hologram 522. The pair of holograms 542 has a square shape and the same size as hologram 522.

[0089] The entrance area A41 includes a hologram 511 and a light guide path 501 at the position of the hologram 511. The distribution area A42 includes a pair of holograms 512 and a light guide path 501 between the pair of holograms 512. The distribution area A43 includes a pair of holograms 513 and a light guide path 501 between the pair of holograms 513.

[0090] The propagation region A51 includes a pair of holograms 521 and a light guide path 501 between the pair of holograms 521. The first exit region A52 includes a pair of holograms 522 and a light guide path 501 between the pair of holograms 522. The propagation region A61 includes a pair of holograms 531 and a light guide path 501 between the pair of holograms 531. The second exit region A62 includes a pair of holograms 532 and a light guide path 501 between the pair of holograms 532. The propagation region A71 includes a pair of holograms 541 and a light guide path 501 between the pair of holograms 541. The third exit region A72 includes a pair of holograms 542 and a light guide path 501 between the pair of holograms 542.

[0091] In the second embodiment, the half-wave plate 109 is omitted compared to the first embodiment. The display light from the polarizing beam splitter 107 is incident on the incident area A41 in the upward direction.

[0092] Fig. 10 is a plan view schematically illustrating the configuration of holographic light guide plate 22 according to embodiment 2. For convenience, Fig. 10 illustrates polarization beam splitter 107 and spatial light modulator 108 located below holographic light guide plate 22 (in the negative Z-axis direction) as viewed in the positive X-axis direction.

[0093] In the second embodiment, the display lights of red wavelength, green wavelength, and blue wavelength (red laser light, green laser light, and blue laser light) transmitted through the polarized beam splitter 107 are incident on the incident area A. 41 The light is incident on the hologram light guide plate 22 from the bottom surface of the hologram 511 in the positive Z-axis direction, ie, upward.

[0094] The hologram 511 is configured to diffract the red, green, and blue wavelength display light backward, thereby allowing the incident area A41 to propagate the display light incident from the polarizing beam splitter 107 to the distribution area A42.

[0095] The pair of holograms 512 is configured to have the highest diffraction efficiency for the red wavelength and the lowest diffraction efficiency for the green and blue wavelengths. The diffraction direction of the pair of holograms 512 is to the left. As a result, the distribution region A42 propagates, of the display light from the entrance region A41, the display light with a red wavelength to the propagation region A51 and the display light with a green and blue wavelengths to the distribution region A43. The pair of holograms 512 is also configured to diffuse the display light with a red wavelength heading toward the propagation region A51 in the left-right direction.

[0096] The pair of holograms 521 are configured to have the highest diffraction efficiency in the red wavelength. The diffraction direction of the pair of holograms 521 is forward. As a result, the propagation region A51 propagates the red wavelength display light from the distribution region A42 to the first exit region A52. The pair of holograms 521 are also configured to diffuse the red wavelength display light traveling toward the first exit region A52 in the forward and backward directions.

[0097] The pair of holograms 522 are configured so that the diffraction efficiency in the red wavelength is maximized and the display light of the red wavelength from the propagation region A51 is emitted from the entire first emission region A52. As a result, the first emission region A52 causes the display light of the red wavelength from the propagation region A51 to exit from the holographic light guide plate 22 in the positive direction of the Z axis and guide it to the projection region 13 (see FIG. 1(b)).

[0098] The diffraction pattern formed on the hologram 522 has a lens effect that causes the display light emitted from the first emission region A52 to form an image at a short distance, so that the display light emitted from the first emission region A52 is irradiated onto the projection region 13 as short-distance display light and forms an image corresponding to a short distance.

[0099] The pair of holograms 513 is configured to have the highest diffraction efficiency for blue wavelengths and the lowest diffraction efficiency for green wavelengths. The diffraction direction of the pair of holograms 513 is to the left. As a result, the distribution region A43 propagates, of the display light from the entrance region A41, the display light with a blue wavelength to the propagation region A71 and the display light with a green wavelength to the propagation region A61. The pair of holograms 513 is also configured to diffuse the display light with a blue wavelength heading toward the propagation region A71 in the left-right direction.

[0100] The pair of holograms 531 are configured to maximize the diffraction efficiency for the green wavelength. The diffraction direction of the pair of holograms 531 is to the right. As a result, the propagation region A61 propagates the green wavelength display light from the distribution region A43 to the second exit region A62. The pair of holograms 531 are also configured to diffuse the green wavelength display light heading toward the second exit region A62 in the left-right direction.

[0101] The pair of holograms 532 are configured so that the diffraction efficiency in the green wavelength is maximized and the display light of the green wavelength from the propagation region A61 is emitted from the entire second emission region A62. As a result, the second emission region A62 causes the display light of the green wavelength from the propagation region A61 to exit from the holographic light guide plate 22 in the positive direction of the Z axis and guide it to the projection region 13 (see FIG. 1(b)).

[0102] Furthermore, the diffraction pattern formed on the hologram 532 has a lens effect that causes the display light emitted from the second emission region A62 to form an image at a long distance, whereby the display light emitted from the second emission region A62 is irradiated onto the projection region 13 as long-distance display light, forming an image corresponding to a long distance.

[0103] The pair of holograms 541 are configured to maximize the diffraction efficiency for blue wavelengths. The diffraction direction of the pair of holograms 541 is backward. As a result, the propagation region A71 propagates the display light of blue wavelengths from the distribution region A43 to the third exit region A72. The pair of holograms 541 are also configured to diffuse the display light of blue wavelengths traveling toward the third exit region A72 in the forward and backward directions.

[0104] The pair of holograms 542 are configured so that the diffraction efficiency in the blue wavelength region is maximized and the display light of the blue wavelength from the propagation region A71 is emitted from the entire third emission region A72. As a result, the third emission region A72 causes the display light of the blue wavelength from the propagation region A71 to exit from the holographic light guide plate 22 in the positive direction of the Z axis and guide it to the projection region 13 (see FIG. 1(b)).

[0105] The diffraction pattern formed on the hologram 542 has a lens effect that causes the display light emitted from the third emission region A72 to form an image at a short distance, so that the display light emitted from the third emission region A72 is irradiated onto the projection region 13 as short-distance display light and forms an image corresponding to a short distance.

[0106] In addition, if an optical system such as a lens is further disposed between the hologram light guide plate 22 and the windshield 12, the holograms 522, 532, and 542 may be set with a diffraction pattern that, in combination with the optical action of this optical system, focuses the display light at a predetermined distance.

[0107] FIG. 11 is a timing chart that schematically shows the driving of the laser light sources 101a, 101b, and 101c and the spatial light modulator .

[0108] The image control circuit 201 repeatedly sets, in this order, a red display period T1 in which display light of a red wavelength is emitted from the first emission area A52, a green display period T2 in which display light of a green wavelength is emitted from the second emission area A62, and a blue display period T3 in which display light of a blue wavelength is emitted from the third emission area A72.

[0109] During the red display period T1, the image control circuit 201 controls the laser light source 101a via the laser drive circuit 202 to emit red laser light during period T11. The image control circuit 201 controls the spatial light modulator 108 via the display drive circuit 203 to modulate the red laser light during period T11. As a result, the display light with a red wavelength forms an image for one frame during the red display period T1.

[0110] During the green display period T2, the image control circuit 201 controls the laser light source 101b via the laser drive circuit 202 to emit green laser light during period T12. The image control circuit 201 controls the spatial light modulator 108 via the display drive circuit 203 to modulate the green laser light during period T12. As a result, the display light with a green wavelength forms an image for one frame during the green display period T2.

[0111] During the blue display period T3, the image control circuit 201 controls the laser light source 101c via the laser drive circuit 202 to emit blue laser light during period T13. The image control circuit 201 controls the spatial light modulator 108 via the display drive circuit 203 to modulate the blue laser light during period T13. As a result, the display light with a blue wavelength forms an image for one frame during the blue display period T3.

[0112] FIG. 12 is a diagram schematically showing near-distance images 431 and 433 and a far-distance image 432 of virtual images formed in the space in front of the projection area 13. In FIG.

[0113] As in the first embodiment, close-distance images 431, 433 and long-distance image 432 are displayed as virtual images at positions farther from projection area 13 as viewed from driver 2. Close-distance images 431, 433 each display the speed of passenger vehicle 1 and the current date and time at positions close to projection area 13. Long-distance image 432 displays the next direction in which passenger vehicle 1 should travel, aligned along the surface of the road at a position farther from projection area 13. This allows driver 2 to check the speed, direction of travel, and date and time while keeping his or her eyes fixed on the road conditions ahead, without having to look down to look at the speedometer display or the car navigation system display installed inside dashboard 11, as in the first embodiment.

[0114] <Effects of the Second Embodiment> According to this embodiment, the following effects are achieved.

[0115] The display light generating unit 21 causes three types of display light having different wavelengths to enter the entrance region A41 of the holographic light guide plate 22. The first exit region A52 has a hologram 522 that forms an image of the red wavelength display light, the second exit region A62 has a hologram 532 that forms an image of the green wavelength display light, and the third exit region A72 has a hologram 542 that forms an image of the blue wavelength display light. The distribution region A42 has a wavelength-dependent hologram 512 and guides the red wavelength display light of the three types of display light incident from the entrance region A41 to the first exit region A52. The distribution region A43 has a wavelength-dependent hologram 513 and guides the green wavelength display light of the three types of display light incident from the entrance region A41 to the second exit region A62 and the blue wavelength display light to the third exit region A72.

[0116] According to this configuration, when display light of a red wavelength enters from the entrance region A41, the display light is guided to the first exit region A52 by the distribution region A42, when display light of a green wavelength enters from the entrance region A41, the display light is guided to the second exit region A62 by the distribution region A43, and when display light of a blue wavelength enters from the entrance region A41, the display light is guided to the third exit region A72 by the distribution region A43. Therefore, as in the first embodiment, the utilization efficiency of each type of display light can be improved. When the utilization efficiency of the display light is improved, the output to the light source 101 can be suppressed, thereby suppressing heat generation, deterioration, power consumption, etc. of the laser light sources 101a, 101b, and 101c.

[0117] Moreover, such distribution of display light can be achieved simply by arranging distribution regions A42 and A43, each having holograms 512 and 513 that depend on optical characteristics, in holographic light guide plate 22. This prevents holographic light guide plate 22 from becoming too complicated and large, thereby simplifying image display device 20 and reducing costs.

[0118] The first type of display light generated in the display light generation unit 21 has a red wavelength, the second type of display light generated in the display light generation unit 21 has a green wavelength, and the third type of display light generated in the display light generation unit 21 has a blue wavelength. With this configuration, by utilizing the differences in the wavelengths of the display lights, the three types of display light can be smoothly guided to the first emission region A52, the second emission region A62, and the third emission region A72, respectively.

[0119] Hologram 512 in distribution area A42 is configured to have the highest diffraction efficiency for red wavelengths and the lowest diffraction efficiency for green and blue wavelengths. Hologram 513 in distribution area A43 is configured to have the highest diffraction efficiency for blue wavelengths and the lowest diffraction efficiency for green wavelengths. With this configuration, display light of red wavelengths, display light of green wavelengths, and display light of blue wavelengths can be efficiently guided to first exit area A52, second exit area A62, and third exit area A72, respectively.

[0120] Hologram 522 in first exit region A52 is configured to have the highest diffraction efficiency in red wavelengths, hologram 532 in second exit region A62 is configured to have the highest diffraction efficiency in green wavelengths, and hologram 542 in third exit region A72 is configured to have the highest diffraction efficiency in blue wavelengths. With this configuration, display light of red wavelengths, display light of green wavelengths, and display light of blue wavelengths can be efficiently emitted from first exit region A52, second exit region A62, and third exit region A72, respectively.

[0121] <Other change examples> In the second embodiment, the display light generating unit 21 generates display light in three wavelength bands, but may generate display light in two wavelength bands. In this case, the holographic light guide plate 22 is provided with only one distribution region having a wavelength-dependent hologram so that the display light in the two wavelength bands can be distributed to the corresponding emission regions.

[0122] In the above-mentioned embodiments 1 and 2 and modified examples 1 and 2, the information displayed based on the display light emitted from the holographic light guide plate 22 is not limited to the speed, direction of travel, information indicating that a predetermined condition has been met, and date and time, and may be changed as appropriate.

[0123] In the above-mentioned embodiments 1 and 2 and modified examples 1 and 2, the lens effect of the hologram of the emission area that emits near-distance display light may be set so that the emission area emits far-distance display light, and the lens effect of the hologram of the emission area that emits far-distance display light may be set so that the emission area emits near-distance display light.

[0124] In the above-described first embodiment and modified examples 1 and 2, half-wave plate 109 is used to generate display light of the first polarization direction and display light of the second polarization direction, but instead, a light source and optical system for generating display light of the first polarization direction and a light source and optical system for generating display light of the second polarization direction may be provided separately, and these two display lights may be combined by a polarizing beam splitter and incident on holographic light guide plate 22. Also, in the above-described second embodiment, a light source and optical system for generating display light of a red wavelength, a light source and optical system for generating display light of a green wavelength, and a light source and optical system for generating display light of a blue wavelength may be provided separately.

[0125] In the above-described first embodiment and first and second modifications, in order to set the polarization direction of the display light from the polarizing beam splitter 107, other optical elements such as a liquid crystal panel may be used instead of the half-wave plate 109 and the actuator 109a.

[0126] In the first embodiment and the first and second modifications, the entrance region A11 is provided on the lower surface of the light guide 301, and the first and second exit regions A22 and A32 are provided on the upper surface of the light guide 301. However, the entrance region A11, the first and second exit regions A22 and A32 may be provided on either the upper or lower surface of the light guide 301. Similarly, in the second embodiment, the entrance region A41, the first and second exit regions A52, the second and third exit regions A62 and A72 may be provided on either the upper or lower surface of the light guide 501.

[0127] In the above-described embodiments 1 and 2 and modified examples 1 and 2, the spatial light modulator 108 reflects the light emitted from the light source 101 to generate display light corresponding to the image, but it may also transmit the light emitted from the light source 101 to generate light corresponding to the image.

[0128] In the above-described first embodiment and modified examples 1 and 2, the polarization direction of the display light that passes through half-wave plate 109 and enters holographic light guide plate 22 may be changed from the first polarization direction or the second polarization direction by adjusting the rotational position of half-wave plate 109. In this case, the polarization direction is shifted from the polarization direction with the highest diffraction efficiency in the hologram of holographic light guide plate 22, so that the amount of display light emitted from holographic light guide plate 22 can be reduced. This allows the brightness of the image formed in front of projection area 13 to be changed.

[0129] In the above-described first and second embodiments and modified examples 1 and 2, examples have been shown in which the present invention is applied to a head-up display mounted on a passenger car 1, but the present invention is not limited to vehicle-mounted displays and can also be applied to other types of image display devices.

[0130] Furthermore, the configurations of the image display device 20 and the display light generation unit 21 are not limited to those shown in FIG. 1(c) and FIG. 2, but can be changed as appropriate.

[0131] The embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical idea defined in the claims. [Explanation of symbols]

[0132] 20 Image display device 21 Display light generation section 22 Holographic light guide plate 312, 322, 332 Hologram 512, 513, 522, 532, 542 Holograms 109 1 / 2 wave plate (optical element) 109a Actuator A11 Incidence area A12 Distribution area A22 First emission area A32 Second exit area A41 Incidence area A42, A43 distribution area A52 First exit area (second exit area) A62 Second exit area (first exit area) A72 Third exit area (first exit area, second exit area)

Claims

1. a holographic light guide plate; a display light generating unit that causes a plurality of types of display light, each having a different state in terms of predetermined optical characteristics, to enter an entrance area of ​​the holographic light guide plate, The holographic light guide plate is a first emission region having a hologram that forms an image of the first type of display light; a second emission region having a hologram that forms an image with the second type of display light; a distribution region having a hologram depending on the optical characteristics, the distribution region guiding the first type of display light to the first exit region and the second type of display light to the second exit region among the plurality of types of display light incident from the entrance region, the optical property is a polarization direction of display light, the first type of display light has a first polarization direction, and the second type of display light has a second polarization direction different from the first polarization direction; The hologram in the distribution area is configured to have the highest diffraction efficiency in the first polarization direction and the lowest diffraction efficiency in the second polarization direction. An image display device characterized by:

2. 2. The image display device according to claim 1, the display light generation unit includes an optical element for switching the polarization direction of the display light between the first polarization direction and the second polarization direction; An image display device characterized by:

3. 3. The image display device according to claim 2, the optical element is a half-wave plate, and an actuator is provided to rotate the half-wave plate around an optical axis. An image display device characterized by:

4. A holographic light guide plate; a display light generating unit that causes a plurality of types of display light, each having a different state in terms of predetermined optical characteristics, to enter an entrance area of ​​the holographic light guide plate, The holographic light guide plate is a first emission region having a hologram that forms an image of the first type of display light; a second emission region having a hologram that forms an image with the second type of display light; a distribution region having a hologram depending on the optical characteristics, the distribution region guiding the first type of display light to the first exit region and the second type of display light to the second exit region among the plurality of types of display light incident from the entrance region, the optical property is a polarization direction of display light, the first type of display light has a first polarization direction, and the second type of display light has a second polarization direction different from the first polarization direction; The hologram in the first exit area is configured to have the highest diffraction efficiency in the first polarization direction, and the hologram in the second exit area is configured to have the highest diffraction efficiency in the second polarization direction. An image display device characterized by:

5. A holographic light guide plate; a display light generating unit that causes a plurality of types of display light, each having a different state in terms of predetermined optical characteristics, to enter an entrance area of ​​the holographic light guide plate, The holographic light guide plate is a first emission region having a hologram that forms an image of the first type of display light; a second emission region having a hologram that forms an image with the second type of display light; a distribution region having a hologram depending on the optical characteristics, the distribution region guiding the first type of display light to the first exit region and the second type of display light to the second exit region among the plurality of types of display light incident from the entrance region, the optical characteristic is a wavelength of display light, the first type of display light has a first wavelength, and the second type of display light has a second wavelength different from the first wavelength; The hologram in the distribution area is configured to have the highest diffraction efficiency at the first wavelength and the lowest diffraction efficiency at the second wavelength. An image display device characterized by:

6. 6. The image display device according to claim 5, The hologram in the first exit area is configured to have the highest diffraction efficiency at the first wavelength, and the hologram in the second exit area is configured to have the highest diffraction efficiency at the second wavelength. An image display device characterized by:

7. 7. The image display device according to claim 1, the first emission region and the second emission region form images of the first type of display light and the second type of display light at positions different from each other; An image display device characterized by:

Images