Optical device, light guide plate, and image generation device

Abstract

The present disclosure relates to an optical device, a light guide plate, and an image generation device that make it possible to provide a higher-resolution image. Provided is an optical device comprising an image generation device that emits image light, and a light guide plate in which the image light is incident thereon, propagates therethrough, and is emitted therefrom to the outside, wherein: in the light guide plate, a first incidence diffraction grating that causes first image light corresponding to a first image to be diffracted and coupled to the inside of the light guide plate, a second incidence diffraction grating that causes second image light corresponding to a second image having a lower resolution than the first image to be diffracted and coupled to the inside of the light guide plate, and an emission diffraction grating that causes the first image light and the second image light both having propagated through the light guide plate to be diffracted, coupled to the outside of the light guide plate, and emitted are provided; and on a flat plate of the light guide plate, a boundary part of the second incidence diffraction grating has a portion not overlapping the region of the first incidence diffraction grating.

Description

Optical device, light guide plate, and image generating device

[0001] The present disclosure relates to an optical device, a light guide plate, and an image generating device, and more particularly to an optical device, a light guide plate, and an image generating device that are capable of providing images with higher resolution.

[0002] Conventionally, a light guide plate that projects image light onto a user's pupils has been developed to realize cross reality (XR), including augmented reality (AR). For example, Patent Literature 1 discloses a technology that presents a high-resolution image over a small field of view to the foveal region of each of the user's eyes and a low-resolution image over a large field of view to fill both eyes and the peripheral region.

[0003] Special Publication No. 2020-515895

[0004] However, the technology disclosed in Patent Document 1 does not mention the resolution when coupling image light to a light guide plate, and there is room for improvement in improving image quality.

[0005] The present disclosure has been made in light of these circumstances, and makes it possible to provide images with higher resolution.

[0006] An optical device according to one aspect of the present disclosure includes an image generation unit that emits image light, and a light guide plate onto which the image light is incident, propagates through the interior, and is emitted to the outside, wherein the light guide plate is provided with a first incident diffraction grating that receives first image light corresponding to a first image, diffracts the incident first image light, and couples the light into the interior of the light guide plate, a second incident diffraction grating that receives second image light corresponding to a second image that has a lower resolution than the first image, diffracts the incident second image light, and couples the light into the interior of the light guide plate, and an exit diffraction grating that diffracts the first image light and the second image light that have propagated through the light guide plate, and couples the light to the outside of the light guide plate for emission, and the optical device is provided with a boundary of the second incident diffraction grating on the flat surface of the light guide plate that does not overlap with a region of the first incident diffraction grating.

[0007] A light guide plate according to one aspect of the present disclosure is a light guide plate including: a first incident diffraction grating that receives first image light corresponding to a first image, diffracts the incident first image light, and couples the first image light to its interior; a second incident diffraction grating that receives second image light corresponding to a second image that has a lower resolution than the first image, diffracts the incident second image light, and couples the second image light to its interior; and an exit diffraction grating that diffracts the first image light and the second image light that have propagated inside, and couples and emits the first image light and the second image light to the outside, and the boundary of the second incident diffraction grating on a flat plate has a portion that does not overlap with the area of ​​the first incident diffraction grating.

[0008] In the optical device and light guide plate according to one aspect of the present disclosure, the first incident diffraction grating and the second incident diffraction grating are arranged on the flat plate of the light guide plate such that the boundary of the second incident diffraction grating, which diffracts second image light corresponding to the second image, which is an image having a lower resolution than the first image, and couples it into the interior of the light guide plate, has a portion that does not overlap with the region of the first incident diffraction grating, which diffracts first image light corresponding to the first image and couples it into the interior.

[0009] An image generating device according to one aspect of the present disclosure includes a first display unit that displays a first display image, which is an image included in a presentation image to be presented to a user, and a second display unit that displays a second display image, which is an image corresponding to an area of ​​the presentation image excluding the first display image; first image light corresponding to the first display image displayed on the first display unit is incident on a first incident diffraction grating arranged to couple the first image light into an interior of a light guide plate; second image light corresponding to the second display image displayed on the second display unit is incident on a second incident diffraction grating arranged to couple the second image light into an interior of the light guide plate; the first image corresponding to the first image light has a higher resolution than the second image corresponding to the second image light; and on the flat surface of the light guide plate, a boundary portion of the second incident diffraction grating has a portion that does not overlap with an area of ​​the first incident diffraction grating.

[0010] In an image generating device according to one aspect of the present disclosure, a first display image is displayed, which is an image included in a presentation image to be presented to a user; a second display image is displayed, which is an image corresponding to a region of the presentation image excluding the first display image; first image light corresponding to the first display image is incident on a first incident diffraction grating arranged to couple the first image light into an interior of a light guide plate; and second image light corresponding to the second display image is incident on a second incident diffraction grating arranged to couple the second image light into an interior of the light guide plate. The first image corresponding to the first image light has a higher resolution than the second image corresponding to the second image light. Furthermore, the first incident diffraction grating and the second incident diffraction grating are arranged on a flat plate of the light guide plate such that a boundary of the second incident diffraction grating has a portion that does not overlap with the region of the first incident diffraction grating.

[0011] The optical device and the image generating device according to one aspect of the present disclosure may be independent devices or may be internal blocks constituting a single device.

[0012] 10 is a diagram showing an example of the configuration of an embodiment of a light guide plate to which the present disclosure is applied. FIG. 11 is a diagram showing an example of the configuration of an embodiment of an optical device to which the present disclosure is applied. FIG. 12 is a diagram showing another example of the configuration of a light guide plate. FIG. 13 is a diagram showing another example of the configuration of an embodiment of an optical device to which the present disclosure is applied. FIG. 14 is a diagram showing an example of a display unit arrangement pattern in an image generating device. FIG. 15 is a diagram showing another example of the configuration of an embodiment of a light guide plate to which the present disclosure is applied. FIG. 16 is a diagram showing yet another example of the configuration of an embodiment of a light guide plate to which the present disclosure is applied. FIG. 17 is a diagram showing an example of a diffraction efficiency distribution. FIG. 18 is a diagram showing yet another example of the configuration of an embodiment of an optical device to which the present disclosure is applied. FIG. 19 is a block diagram showing an example of the functional configuration of the control device of FIG. 10. FIG. 19 is a diagram showing yet another example of the configuration of an embodiment of an optical device to which the present disclosure is applied. FIG. 19 is a diagram showing the relationship between the angle of incidence of an ICG with respect to the normal to the light guide plate and the angle of emission of an OCG. FIG. 19 is a diagram showing the overlap of the regions of an ICG for fovial and an ICG for peripheral. FIG. 19 is a diagram showing an example of the configuration of a conventional light guide plate.

[0013] <<First Embodiment>>

[0014] <Configuration of Light Guide Plate> FIG. 1 is a diagram showing an example of the configuration of an embodiment of a light guide plate to which the present disclosure is applied.

[0015] The light guide plate 11 is an optical plate made of glass, resin, etc. Image light is incident on the light guide plate 11, and the incident image light propagates inside the light guide plate 11 at a total reflection angle and is emitted to the outside. The light guide plate 11 is provided with ICGs 21 and 22 that couple the incident light into the inside of the light guide plate 11, and an OCG 23 that couples the light guided through a path inside the light guide plate 11 toward a user (observer) outside the light guide plate 11.

[0016] The ICGs 21 and 22 are incoupling gratings (ICGs) that diffract incident image light and couple it into the interior of the light guide plate 11. The OCG 23 is an outcoupling grating (OCG) that diffracts image light that has propagated inside the light guide plate 11 and couples it to the outside of the light guide plate 11 for emission. That is, the ICGs 21 and 22 are incident diffraction gratings arranged on the flat plate of the light guide plate 11, and the OCG 23 is an exit diffraction grating arranged on the flat plate of the light guide plate 11.

[0017] The ICG 21 is an ICG for foveal. The ICG 21 is disposed in correspondence with image light corresponding to a high-resolution image among the image light. The ICG 22 is an ICG for peripheral. The ICG 22 is disposed in correspondence with image light corresponding to a low-resolution image among the image light. In other words, when the image light of a high-resolution image and a low-resolution image having different resolutions is coupled to the light guide plate 11 with high efficiency, the image light is incident on the ICG 21 and ICG 22, which are designed for each image.

[0018] The light guide plate 11 allows the user to perceive images with different resolutions by arranging an ICG 21 for the foveal and an ICG 22 for the peripheral. Here, by arranging the ICG 21 for providing image light corresponding to a high-resolution image to the foveal, which is a part of the user's eye, and the ICG 22 for providing image light corresponding to a low-resolution image over a larger field of view, it is possible to present a high-resolution image over a small field of view in the foveal region of the user's eye and a low-resolution image over a large field of view. The fovea is a depression on the retina of the eye with the highest visual acuity.

[0019] <Configuration of Optical Device> FIG. 2 is a diagram showing a configuration example of an embodiment of an optical device to which the present disclosure is applied.

[0020] 2, the optical device 1 is composed of a light guide plate 11, an image generating device 12, and an incident angle modulation unit 13. The image generating device 12 may also include the incident angle modulation unit 13. The light guide plate 11 is provided with an ICG 21 for foveal, an ICG 22 for peripheral, and an OCG 23. In Fig. 2, parts corresponding to those in Fig. 1 are denoted by the same reference numerals, and their description will be omitted where appropriate.

[0021] The image generating device 12 generates images with different resolutions (ppd: Pixel Per Degree) and emits image light of the generated images. For example, the image generating device 12 generates a high-resolution image 31 and a low-resolution image 32, which has a lower resolution than the high-resolution image 31, and displays them on a display panel, thereby emitting image light corresponding to the generated high-resolution image 31 and low-resolution image 32. Specifically, the high-resolution image 31 is an image included in a presentation image (image frame) presented to the user 41, and the low-resolution image 32 can be an image corresponding to a region of the presentation image excluding the high-resolution image 31. The image light L1 corresponding to the high-resolution image 31 is incident on the ICG 21 via the incident angle modulation unit 13, and the image light L2 corresponding to the low-resolution image 32 is incident on the ICG 22.

[0022] The incident angle modulation unit 13 is a modulation element that modulates the incident angle of the image light L1 incident on the ICG 21. The incident angle modulation unit 13 modulates at least a portion of the image light L1 emitted from the image generation device 12 and makes the modulated light incident on the ICG 21. As a result, in the light guide plate 11, the image light L1 whose incident angle has been modulated by the incident angle modulation unit 13 is incident on the ICG 21, and the image light L2 emitted from the image generation device 12 is incident on the ICG 22. The OCG 23 emits the image light L1 and the image light L2 propagated inside the light guide plate 11 toward the eye 42 of the user 41 outside the light guide plate 11. This makes it possible to present, for example, a high-resolution image 31 over a small field of view in the fovea central region of the eye 42 and a low-resolution image 32 over a large field of view to the user 41.

[0023] Here, the incident angle modulation unit 13 can modulate the incident angle of the image light L1 relative to the ICG 21 in accordance with the line of sight of the user 41. In this case, if the image light L1 with its incident angle modulated passes through a portion of the ICG 22, a different phase is added to the light ray (beam), widening the PSF (Point Spread Function) on the retina of the eye 42 of the user 41, which may result in a loss of image quality. In the present disclosure, the light guide plate 11 is arranged so that the boundary of the ICG 22 does not overlap with the scanning area of ​​the image light L1 by the incident angle modulation unit 13. The boundary of the ICG 22 is the boundary between the area in which the diffraction grating is formed in the ICG 22 and the area on the flat surface of the light guide plate 11 where the diffraction grating is not formed. In other words, the ICG 21 and the ICG 22 are arranged so that the scanning area of ​​the image light L1 does not cross the boundary of the ICG 22.

[0024] As a result, the image light L1 scanned by the incident angle modulation unit 13 does not generate different phase delays within the beam, and a beam with a regular wavefront propagates inside the light guide plate 11, making it possible to provide the user 41 with a high-resolution image 31 corresponding to the image light L1 at a higher resolution. For example, the high-resolution image 31 can be provided as an image with a higher resolution in accordance with the line of sight of the user 41.

[0025] 3, the ICG 22 for peripheral light may be arranged in the light guide plate 11 so as to include the ICG 21 for foveal light. In FIG. 3 as well, the ICG 21 and the ICG 22 are arranged so that the boundary of the ICG 22 does not overlap with the area of ​​the ICG 21 (i.e., so as not to overlap with the scanning area of ​​the image light L1 by the incident angle modulation unit 13). If the ICG 22 is arranged so as to include the ICG 21 in this way, the boundary of the ICG 22 does not cross when the image light L1 is scanned by the incident angle modulation unit 13, and therefore a beam with a regular wavefront is propagated inside the light guide plate 11, making it possible to provide an image with higher resolution.

[0026] <<Second Embodiment>>

[0027] <Configuration of Optical Device> FIG. 4 is a diagram showing another configuration example of an embodiment of an optical device to which the present disclosure is applied.

[0028] 4, the optical device 1 is composed of a light guide plate 11, an image generating device 12, an incident angle modulation unit 13, an optical system 14, and an optical system 15. The image generating device 12 may include the incident angle modulation unit 13, or may include the incident angle modulation unit 13, the optical system 14, and the optical system 15. The light guide plate 11 is provided with an ICG 21 for foveal, an ICG 22 for peripheral, and an OCG 23. In FIG. 4, parts corresponding to those in FIG. 2 etc. are assigned the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0029] The image generating device 12 generates an image with a predetermined resolution, displays it on a display panel, and emits image light of the generated image. The optical system 14 is composed of a lens having a first optical magnification, etc. The optical system 14 is disposed on an optical path between the image generating device 12 and the incident angle modulation unit 13, and optically enlarges or reduces the image light L1 (or an image corresponding to the image light L1) emitted from the image generating device 12. For example, the optical system 14 optically enlarges an image corresponding to the image light L1 using a lens having the first optical magnification, and causes the image light L1 corresponding to the enlarged image to enter the incident angle modulation unit 13. The incident angle modulation unit 13 modulates the incident angle of the image light L1 incident via the optical system 14, and causes the image light L1 to enter the ICG 21 on the flat plate of the light guide plate 11.

[0030] The optical system 15 is composed of a lens having a second optical magnification, etc. The optical system 15 is disposed on the optical path between the image generating device 12 and the ICG 22 on the flat plate of the light guide plate 11, and optically enlarges or reduces the image light L2 (or the image corresponding to it) emitted from the image generating device 12. The second optical magnification is an optical magnification different from the first optical magnification. For example, the second optical magnification can be an optical magnification higher than the first optical magnification. For example, the optical system 15 optically enlarges the image corresponding to the image light L2 using a lens having the second optical magnification, and causes the image light L2 corresponding to the enlarged image to enter the ICG 22.

[0031] In this way, by providing the image generating device 12 with the optical systems 14 and 15 having different optical magnifications, images with different resolutions can be formed from the image light emitted from the image generating device 12, and the image light can be incident on the ICG 21 and the ICG 22. Here, the image light L1 corresponding to the high-resolution image can be incident on the ICG 21 via the incident angle modulation unit 13, and the image light L2 corresponding to the low-resolution image can be incident on the ICG 22. This makes it possible to present, for example, a high-resolution image over a small field of view in the foveal region of the eye 42 of the user 41, and a low-resolution image over a large field of view.

[0032] 4 , the optical systems 14 and 15 can optically enlarge an image corresponding to the image light incident on the ICG 21 and ICG 22, so that when an image is displayed on a display panel in the image generating device 12, there are no limitations imposed by the resolution or size of the display panel. Also, in FIG. 4 , the ICG 21 and ICG 22 are arranged on the flat plate of the light guide plate 11 so that the boundary portion of the ICG 22 does not overlap with the scanning area of ​​the image light L1 scanned by the incident angle modulation unit 13. Therefore, the image light L1 scanned by the incident angle modulation unit 13 does not cross the boundary portion of the ICG 22, so that a beam with a regular wavefront is propagated inside the light guide plate 11, and a higher resolution image can be provided.

[0033] <Display Unit Arrangement Pattern> Fig. 5 is a diagram showing an example of a display unit arrangement pattern in the image generation device 12. The image generation device 12 has one or more display panels. At least one of the display panels of the image generation device 12 can be configured as a self-luminous display panel.

[0034] Fig. 5 shows the arrangement of the display units in a plan view when the image generating device 12 is viewed from the image light output surface side. Fig. 5 shows five display unit arrangement patterns, A to E in Fig. 5. The display unit 51 is a display unit that displays a display image corresponding to the image light L1 incident on the foveal ICG 21. The display unit 52 is a display unit that displays a display image corresponding to the image light L2 incident on the peripheral ICG 22. The display units 51 and 52 can be provided by one or more display panels.

[0035] 5A to 5C show examples in which the areas of the display unit 51 and the display unit 52 are arranged side by side in a plan view. FIG. 5A shows a case in which the areas of the display unit 51 and the display unit 52 are approximately the same size. FIG. 5B shows a case in which the area of ​​the display unit 51 is smaller than the area of ​​the display unit 52. FIG. 5C shows a case in which the area of ​​the display unit 51 is larger than the area of ​​the display unit 52. For example, when the image generating device 12 of FIG. 2 is viewed in a plan view, if it has the display unit 51 and the display unit 52, the arrangement pattern may be any of the arrangement patterns of FIG. 5A to 5C. For example, in FIGS. 5A to 5C, the display unit 51 and the display unit 52 can be provided by different display panels (two display panels having different resolutions).

[0036] 5D and 5E show examples where one display unit is arranged within the area of ​​the other display unit. D in Fig. 5D shows a case where the area of ​​display unit 51 exists within the area of ​​display unit 52. E in Fig. 5E shows a case where the area of ​​display unit 52 exists within the area of ​​display unit 51. For example, when the image generating device 12 in Fig. 4 is viewed in plan, if it has display units 51 and 52, the arrangement pattern may be one of the arrangement patterns D and E in Fig. 5. For example, in Figs. 5D and 5E, the display units 51 and 52 can be provided by the same display panel.

[0037] In this way, in the image generating device 12, the display units 51 and 52 can be arranged in various arrangement patterns, and the image light L1 from the display unit 51 is incident on the ICG 21, and the image light L2 from the display unit 52 is incident on the ICG 22, so that the image light L1 and the image light L2 corresponding to two images with different resolutions (a high-resolution image and a low-resolution image) can be coupled within the light guide plate 11. This allows the user to view an image (presented image) optically synthesized by the light guide plate 11.

[0038] In the image generation device 12, the display images displayed on the display units 51 and 52 can be, for example, the following images. That is, the image generation device 12 performs image processing on a presentation image (image frame) to be presented to the user, and clips (cuts out) an image (a part of the image) of a region corresponding to the user's line of sight from the presentation image, and sets the clipped image as the first display image to be displayed on the display unit 51. The image generation device 12 also sets an image corresponding to a region of the presentation image excluding the first display image as the second display image to be displayed on the display unit 52. For example, the first display image may correspond to a high-resolution image and the second display image may correspond to a low-resolution image, but the first display image may be an image with a higher resolution than the second display image, or the first display image and the second display image may be images with a predetermined resolution and optically enlarged by the optical systems 14 and 15. In short, it is sufficient that the image corresponding to the image light L1 incident on the foveal ICG 21 is a high-resolution image, and the image corresponding to the image light L2 incident on the peripheral ICG 22 is a low-resolution image, and the configuration of the display panel (e.g., number of panels, panel resolution (number of pixels), panel size and arrangement, etc.), image processing unit, optical components, etc., can be configured as desired.

[0039] <<Third Embodiment>>

[0040] <Configuration of Light Guide Plate> Fig. 6 is a diagram showing another configuration example of an embodiment of a light guide plate to which the present disclosure is applied. Fig. 6 shows a configuration in which two light guide plates, light guide plate 11-1 and light guide plate 11-2, are provided. Light guide plate 11-1 and light guide plate 11-2 are installed at a predetermined distance from each other. Light guide plate 11-1 and light guide plate 11-2 have different thicknesses. For example, light guide plate 11-1 is thinner than light guide plate 11-2.

[0041] The light guide plate 11-1 is provided with an ICG 22-1 that is an ICG for peripheral use and an OCG 23-1 that is an OCG for peripheral use. The light guide plate 11-2 is provided with an ICG 21-2 that is an ICG for foveal use and an OCG 23-2 that is an OCG for foveal use.

[0042] Image light L1 emitted from the image generating device 12 passes through the light guide plate 11-1 and is incident on the ICG 21-2 of the light guide plate 11-2 by scanning with the incident angle modulation unit 13, and is coupled into the interior of the light guide plate 11-2. Image light L2 emitted from the image generating device 12 is incident on the ICG 22-1 of the light guide plate 11-1 and is coupled into the interior of the light guide plate 11-1. The light guided inside the light guide plate 11-2 is coupled toward the user outside the light guide plate 11 by the OCG 23-2, and the light diffracted inside the light guide plate 11-1 is coupled toward the user outside the light guide plate 11 by the OCG 23-1.

[0043] 6, when the ICG 22-1 arranged on the light guide plate 11-1 and the ICG 21-2 arranged on the light guide plate 11-2 are viewed on the same plane, the ICG 22-1 and the ICG 21-2 are arranged so that the boundary of the ICG 22-1 does not overlap with the scanning area (area within the ICG 21-2) of the image light L1 scanned by the incident angle modulation unit 13. Therefore, the image light L1 scanned by the incident angle modulation unit 13 does not cross the boundary of the ICG 22-1, and a beam with a regular wavefront is propagated inside the light guide plate 11-2, making it possible to provide an image with higher resolution.

[0044] Although FIG. 6 shows a configuration with two light guide plates, three or more light guide plates may be provided. That is, at least two or more light guide plates may be provided, and each light guide plate may be provided with at least one ICG, including an ICG for fovial and an ICG for peripheral. Furthermore, at least one of the two or more light guide plates may have a different thickness. For example, the area of ​​the ICG for fovial is expected to be larger than the area of ​​the ICG for peripheral. However, since the optimal thickness and arrangement may differ depending on each ICG, a different light guide plate may be used for each ICG.

[0045] <<Fourth Embodiment>>

[0046] <Configuration of Light Guide Plate> Fig. 7 is a diagram showing yet another configuration example of an embodiment of a light guide plate to which the present disclosure is applied. Fig. 7 shows a configuration in which the ICG 21, ICG 22, and OCG 23 arranged on the light guide plate 11 have different diffraction efficiency distributions.

[0047] 7A shows a configuration in which the foveal ICG 21 has regions with different diffraction efficiencies in at least a portion of its area. In FIG. 7A, the diffraction efficiency distribution is represented by a pattern within the ICG 21 region. For example, within the ICG 21 region, the diffraction efficiency increases as the region approaches the black region, and decreases as the region moves away from the black region. The ICG 21 can diffract the image light L1 incident via the incident angle modulation unit 13 into the light guide plate 11 by using the regions with different diffraction efficiencies (diffraction gratings formed therein).

[0048] 7B shows a configuration in which the peripheral ICG 22 has regions with different diffraction efficiencies in at least a portion of its area. In FIG. 7B, the diffraction efficiency distribution is represented by a pattern within the region of the ICG 22. The ICG 22 can diffract the incident image light L2 into the interior of the light guide plate 11 by the regions with different diffraction efficiencies (the diffraction gratings formed in the regions).

[0049] 7C shows a configuration in which the OCG 23 has regions with different diffraction efficiencies in at least a portion of its area. In FIG. 7C, the diffraction efficiency distribution is represented by a pattern within the region of the OCG 23. The OCG 23 diffracts light guided through a path inside the light guide plate 11 by (the diffraction grating formed in) the regions with different diffraction efficiencies, and emits the light to the outside of the light guide plate 11.

[0050] Here, with reference to Figures 8 and 9, an example of a configuration in which the diffraction efficiency distributions of the ICG 21, ICG 22, and OCG 23 are different will be described. In Figure 8, a cross-sectional view of the diffraction gratings 61-1, 61-2, and 61-3 is shown in Figure 8A, and a top cross-sectional view is shown in Figure 8B. As shown in Figure 8, the diffraction gratings 61-1, 61-2, and 61-3 have different diffraction grating shapes, and when the diffraction grating shapes are different, the diffraction efficiency distributions will be different. In other words, in Figure 8, T represents the period of the diffraction grating, and generally, when the diffraction grating shapes are different and the refractive index distribution within the period is different, the diffraction efficiency distributions will be different. Furthermore, although FIG. 8 illustrates an example of the period (T) of the diffraction grating on the xy plane, in the present disclosure, the periodicity of T is not limited by the xy plane. For example, as long as the vector (diffraction vector) of the diffraction grating described below is in a closed state (A in FIG. 13), there is no limit to the number and shape (including periodicity) of the diffraction gratings formed on the light guide plate.

[0051] The difference in diffraction efficiency distribution can be investigated, for example, using the following method. That is, as shown in FIG. 9 , a measuring device measures the zeroth-order diffracted light when the diffraction grating 61 diffracts light from a measurement light source. In this measurement, the difference in diffraction efficiency distribution can be investigated by analyzing the wavelength and angle dependence of the diffracted light. For example, the graph in FIG. 9 , with the horizontal axis representing wavelength and the vertical axis representing zeroth-order diffraction efficiency, shows that the zeroth-order diffraction efficiency for each wavelength of diffracted light is different between diffraction efficiency distribution A and diffraction efficiency distribution B. In this way, the diffraction efficiency distribution indicates the dependence of the diffraction efficiency on wavelength and incident angle.

[0052] In the optical device 1, by configuring the ICG 21, ICG 22, and OCG 23 arranged on the light guide plate 11 to have different diffraction efficiency distributions, it is possible to provide an image with uniform brightness and reduced color unevenness as the image presented to the user. Note that while Fig. 7 shows a configuration in which the regions of ICG 21, ICG 22, and OCG 23 have different diffraction efficiency distributions, it is sufficient that at least one of the regions has a different diffraction efficiency distribution, such as a configuration in which the regions of ICG 21, ICG 22, and OCG 23 each have a different diffraction efficiency distribution.

[0053] <<Fifth Embodiment>>

[0054] <Configuration of Optical Device> FIG. 10 is a diagram showing yet another configuration example of an embodiment of an optical device to which the present disclosure is applied.

[0055] 10 , the optical device 1 is composed of a light guide plate 11, an image generating device 12, an incident angle modulation unit 13, a control device 71, and a line of sight detection device 72. The image generating device 12 may include the incident angle modulation unit 13. The light guide plate 11 is provided with an ICG 21 for foveal, an ICG 22 for peripheral, and an OCG 23. In FIG. 10 , parts corresponding to those in FIG. 2 and the like are denoted by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0056] The control device 71 is composed of a processor such as a CPU (Central Processing Unit). The control device 71 controls the operation of each part of the optical device 1. The gaze detection device 72 is composed of a camera, an image processing circuit, etc. The gaze detection device 72 is disposed in a position where it can detect the movement of the eye 42 of the user 41. The gaze detection device 72 detects the gaze of the user 41 and outputs the detection data to the control device 71. The gaze detection method can be a known technique, such as a method of detecting a gaze vector of the place where the user 41 is looking with the eye 42.

[0057] The control device 71 controls the image light emitted from the image generation device 12 based on the detection data input from the line-of-sight detection device 72. The image generation device 12 generates an image and emits image light of the generated image in accordance with the control from the control device 71. The incident angle modulation unit 13 modulates the incident angle of the image light L1 incident on the ICG 21 of the light guide plate 11 in accordance with the control from the control device 71.

[0058] Fig. 11 is a block diagram showing an example of the functional configuration of the control device 71 in Fig. 10. In Fig. 11, the control device 71 is composed of a gaze detection unit 81, a fovial region determination unit 82, a peripheral region determination unit 83, a fovial display control unit 84, a peripheral display control unit 85, and an incident angle control unit 86.

[0059] The gaze detection unit 81 detects the gaze of the user 41 based on detection data input from the gaze detection device 72. Gaze information regarding the gaze of the user 41 is output to the foveal region determination unit 82 and the peripheral region determination unit 83. Note that the gaze information does not necessarily have to be acquired based on detection data from the gaze detection device 72, but may also be acquired by processing by the gaze detection unit 81. For example, the gaze detection unit 81 may acquire the gaze information by acquiring image data obtained by the gaze detection device 72 photographing the user 41, and then performing image processing on the acquired image data to detect a gaze vector.

[0060] The fovial region determination unit 82 determines a fovial region corresponding to the image light incident on the ICG 21 based on the gaze information input from the gaze detection unit 81. The peripheral region determination unit 83 determines a peripheral region corresponding to the image light incident on the ICG 22 based on the gaze information input from the gaze detection unit 81. For example, in a presentation image (image frame) presented to a user, a region corresponding to the user's gaze direction can be determined as the fovial region, and a region corresponding to the region excluding the fovial region can be determined as the peripheral region. Fovial region information related to the fovial region is output to a fovial display control unit 84 and an incident angle control unit 86. Peripheral region information related to the peripheral region is output to a peripheral display control unit 85.

[0061] The fovial display control unit 84 controls the display of an image by the image generation device 12 based on the fovial region information input from the fovial region determination unit 82. The peripheral display control unit 85 controls the display of an image by the image generation device 12 based on the peripheral region information input from the peripheral region determination unit 83. For example, as shown in FIG. 5 , when the image generation device 12 has a display unit 51 and a display unit 52, the following control is performed. That is, the fovial display control unit 84 controls the display unit 51 to display a display image corresponding to the image light L1 incident on the fovial ICG 21 based on the fovial region information. Furthermore, the peripheral display control unit 85 controls the display unit 52 to display a display image corresponding to the image light L2 incident on the peripheral ICG 22 based on the peripheral region information.

[0062] The incident angle control unit 86 controls the scanning by the incident angle modulation unit 13 based on the foveal area information input from the foveal area determination unit 82, and controls the incident angle of the image light L1 incident on the foveal ICG 21.

[0063] In this way, by providing the control device 71 and the line-of-sight detection device 72, the optical device 1 can present a high-resolution image 31 over a small field of view corresponding to the line-of-sight direction of the user 41, and a low-resolution image 32 over a large field of view when presenting an image to the user 41. In addition, in Fig. 10, the boundary portion of the ICG 22 on the flat plate of the light guide plate 11 does not overlap with the scanning area of ​​the image light L1 by the incident angle modulation unit 13, so that a beam with a regular wavefront is propagated inside the light guide plate 11, and an image with higher resolution can be provided.

[0064] 10 shows a configuration corresponding to that of Fig. 2, but a configuration corresponding to that of Fig. 4 may also be used in which optical systems 14 and 15 are provided. The optical system 14 and the optical system 15 may be provided in the optical device 1, or may be provided in the image generating device 12.

[0065] <<Application Examples>>

[0066] <Configuration without an incident angle modulation unit> Fig. 12 is a diagram showing yet another configuration example of an embodiment of an optical device to which the present disclosure is applied. In Fig. 12, Fig. 12A and Fig. 12B show a configuration in which image light L1 corresponding to high-resolution images with different angles of view is incident on the ICG 21 of the light guide plate 11 without providing an incident angle modulation unit 13. In Fig. 12A and Fig. 12B, parts corresponding to those in Fig. 4 are assigned the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0067] 12A and 12B, the optical device 1 is composed of a light guide plate 11, an image generating device 12, an optical system 14, and an optical system 15. The image generating device 12 may also include the optical system 14 and the optical system 15. The light guide plate 11 is provided with an ICG 21 for foveal, an ICG 22 for peripheral, and an OCG 23. Here, for example, as shown in FIG. 5, when the image generating device 12 has a display unit 51 and a display unit 52, the following control is performed.

[0068] That is, the display unit 51 of the image generating device 12 changes the fovial display range position, which is a position corresponding to the range in which a display image corresponding to the high-resolution image 31 is displayed. The display unit 52 of the image generating device 12 also changes the peripheral display range position, which is a position corresponding to the range in which a display image corresponding to the low-resolution image 32 is displayed, excluding the fovial display range position. For example, comparing FIG. 12A with FIG. 12B, the fovial display range position changes over time from the lower right to the upper left in accordance with the line of sight of the user 41, and the peripheral display range position also changes accordingly. For ease of explanation, the peripheral display range position relative to the fovial display range position and the fovial display range position relative to the peripheral display range position are each represented by a black area on the image generating device 12 side.

[0069] Of the image light L1 and image light L2 emitted from the image generating device 12, the image light L1 is incident on the ICG 21 via the optical system 14, and the image light L2 is incident on the ICG 22 via the optical system 15. At this time, in the display unit 51 of the image generating device 12, the foveal display range position is changed over time (changing from the lower right to the upper left position in Figures 12A and 12B), so that the image light L1 corresponding to the high-resolution image 31 with a different angle of view can be incident on the ICG 21 of the light guide plate 11.

[0070] In this way, in the optical device 1, by the image generating device 12 changing the foveal display range position over time, it is possible to make the high-resolution image (the image light L1) incident on the ICG 21 at different angles of view even without the incident angle modulation unit 13. As a result, when presenting an image to the user 41, it is possible to present the high-resolution image 31 over a small field of view according to the line of sight of the user 41, and the low-resolution image 32 over a large field of view. Also, in Figure 12, on the flat surface of the light guide plate 11, the boundary of the ICG 22 does not overlap with the area of ​​the ICG 21, so a beam with a regular wavefront is propagated inside the light guide plate 11, making it possible to provide an image with higher resolution.

[0071] <Incoming and outgoing angles of ICG and OCG> Fig. 13 is a diagram illustrating the relationship between the incoming angle of the ICG and the outgoing angle of the OCG with respect to the normal to the light guide plate 11. In Fig. 13, cross-sectional views of the light guide plate 11 are shown in Fig. 13A and Fig. 13B. In addition, the direction of the image light is indicated by solid and dashed arrows.

[0072] In A of Fig. 13, the diffraction grating vectors of the ICG 21, ICG 22, and OCG 23 arranged on the light guide plate 11 are closed, and the incident angle of the ICG and the exit angle of the OCG are the same for all wavelengths with respect to the normal to the light guide plate 11. On the other hand, in B of Fig. 13, the diffraction grating vectors of the ICG 21, ICG 22, and OCG 23 arranged on the light guide plate 11 are not closed. When the diffraction grating vector is not closed, the exit angle of the OCG 23 differs for each wavelength, and one piece of angle information spreads on the retina of the user's eyeball (because the image is blurred), resulting in a deterioration in image resolution (B1 in the figure).

[0073] 13A, the ICG 21, ICG 22, and OCG 23 arranged in the light guide plate 11 are configured so that the vectors of the diffraction gratings are closed, and the incident angle of the ICG and the exit angle of the OCG are the same (almost the same) for all wavelengths, thereby achieving a more suitable resolution without degrading the image resolution (A1 in the figure). That is, in the light guide plate 11, the OCG 23 can diffract the image light that has been diffracted by the ICG 21 and ICG 22 and guided inside the light guide plate 11 to the outside of the light guide plate 11 in a conjugate symmetric relationship.

[0074] <Overlapping of ICG Regions> Figure 14 is a diagram explaining the overlap of the regions of the foveal ICG 21 and the peripheral ICG 22. In Figure 14, examples of arrangements in which the regions of the ICG 21 and the ICG 22 partially overlap are shown in Figures 14A and 14B, respectively. In Figures 14A and 14B, a top view is shown in the upper row, and a side view is shown in the lower row.

[0075] As shown in the top view of Fig. 14A, when a part of the area of ​​ICG 22 overlaps with the area of ​​ICG 21, when the area in ICG 21 that is actually illuminated by image light L1 (i.e., the area that is actually used) is shown as a circular use area 91 indicated by a dashed line, the area of ​​ICG 21 and the use area 91 are the same area. In this case, as shown in the side view of Fig. 14A, the area of ​​ICG 22 overlaps with the use area 91 of ICG 21.

[0076] On the other hand, as shown in the top view of Fig. 14B, even if a part of the area of ​​ICG 22 overlaps with the area of ​​ICG 21, when the area of ​​use 91 is different and smaller than the area of ​​ICG 21, the area of ​​ICG 22 does not overlap with the area of ​​use 91 of ICG 21, as shown in the side view of Fig. 14B. In the present disclosure, even if the ICGs appear to overlap when viewed from above, it is sufficient that the area of ​​the ICG 22 for peripheral use is not included in the area actually used in the ICG 21 for foveal use, and a configuration such as that shown in Fig. 14B can be adopted.

[0077] In the present disclosure, the relationship between the ICG 21 for foveal and the ICG 22 for peripheral, which are disposed on the flat plate of the light guide plate 11, is such that the boundary of the ICG 22 has a portion that does not overlap with the area of ​​the ICG 21. The boundary here is the boundary between the area in which the diffraction grating is formed in the ICG 22 and the area on the flat plate of the light guide plate 11 where the diffraction grating is not formed. For example, on the flat plate of the light guide plate 11, the ICG 22 can be disposed so that its boundary does not overlap with the scanning area (area within the ICG 21) of the image light L1 scanned by the incident angle modulation unit 13. In other words, the same effect can be obtained not only when the areas of the ICG 21 and the ICG 22 do not overlap at all, but also when there is an overlapping area.

[0078] <Configuration of Wearable Device> The optical device 1 can be applied to wearable devices such as AR glasses and OST (Optical See-Through) glasses. Fig. 15 is a diagram showing a configuration example of an embodiment of a wearable device to which the present disclosure is applied. Fig. 15 shows a schematic diagram of the wearable device as viewed from above.

[0079] In FIG. 15, the wearable device 101 includes a frame 111 worn on the user's head and an optical device 1 (see FIG. 2, etc.) attached to the frame 111. The optical device 1 has a light guide plate 11 and an image generation device 12. The incident angle modulation unit 13 is included in the image generation device 12. In a configuration including optical systems 14 and 15, it can be included in the image generation device 12. In FIG. 15, the wearable device 101 is a binocular type including two optical devices 1. However, it may also be a monocular type including one optical device 1. Light from the image generation device 12 propagates through the semi-transmissive (see-through) light guide plate 11 by total reflection and is emitted toward the user's eye (pupil).

[0080] The frame 111 is composed of a front section 112 positioned in front of the user, two temple sections 113 rotatably attached to both ends of the front section 112 via hinges, and end sections 114 attached to the tips of each temple section 113. The end sections 114 are also called ear tips, earmuffs, or ear pads. Wiring (such as signal lines and power lines) extending from the image generating device 12 passes through the temple sections 113 and end sections 114, extends from the tips of the end sections 114 to the outside, and is connected to the control device 71 (see, e.g., FIG. 10 ). A headphone section 115 is connected to the wiring (headphone wiring) extending from the image generating device 12. A gaze detection device 72 (see, e.g., FIG. 10 ) can be attached to a predetermined region (such as the central region) of the front section 112 using an appropriate attachment member, as needed. Detection data from the gaze detection device 72 is sent to the control device 71 via wiring extending from the gaze detection device 72.

[0081] The wearable device 101 can be applied to various types of head mounted displays (HMDs) as well as AR glasses and OST glasses. The images presented to the user are not limited to augmented reality (AR) images, but may include images presented to the user to realize cross reality (XR) including virtual reality (VR), mixed reality (MR), and the like.

[0082] <<Effects>>

[0083] In the present disclosure, a boundary portion of the peripheral ICG 22 disposed on the flat surface of the light guide plate 11 has a portion that does not overlap with the region of the ICG 21 (for example, the boundary portion of the ICG 22 does not overlap with the scanning region of the image light L1), thereby providing a higher resolution image. For comparison, the configuration of a conventional light guide plate is shown in FIG. 16 . As shown in FIG. 16A , if the peripheral ICG 22 is disposed within the region of the foveal ICG 21 in the light guide plate 11, the image light from the incident angle modulation unit 13 will cross the boundary portion of the ICG 22, resulting in scattering and diffraction, and degrading image quality. The same is true when the region of the foveal ICG 21 and the region of the peripheral ICG 22 partially overlap, as shown in FIG. 16B , and the region of the ICG 21 is the scanning region.

[0084] When coupling images in the foveal and peripheral regions with different resolutions to a light guide plate with high efficiency, it is assumed that image light is incident on an ICG designed for each region. In this case, when the image light in the foveal region is angle-modulated to match the user's line of sight, if the image light passes through a portion of the ICG in the peripheral region, a different phase is added to the beam, causing the PSF on the user's retina to widen and image quality to be impaired. To solve this problem, the present disclosure, for example, by ensuring that the boundary of the ICG 22 does not overlap with the scanning region of the image light L1 (the region within the ICG 21), the image light L1 scanned by the incident angle modulation unit 13 does not generate different phase delays in the beam, and a beam with a regular wavefront propagates within the light guide plate 11, thereby providing the user with a higher-resolution image.

[0085] In the above description, the regions of ICG 21 and ICG 22 (regions where diffraction gratings are formed) arranged on the flat plate of light guide plate 11 are circular in shape, but other shapes may be adopted as long as the boundary of ICG 22 has a portion that does not overlap with the region of ICG 21. Furthermore, since the region within ICG 21 is the scanning region, it is expected that the region of ICG 21 will be larger than the region of ICG 22, but the present disclosure is also applicable even when the region of ICG 22 is larger than the region of ICG 21. Furthermore, the shape of OCG 23 is not limited to a trapezoid, and other shapes may be adopted.

[0086] In the above description, the image generating device 12 may be configured to include the incident angle modulation unit 13, the optical system 14, and the optical system 15. However, the incident angle modulation unit 13, the optical system 14, and the optical system 15 may be provided in the same housing as components such as the display panel of the image generating device 12, or may be provided in another housing or externally. It is not necessary to provide both the optical system 14 and the optical system 15, and only one of the optical systems may be provided. In this specification, an image may be considered as a video (video) consisting of multiple image frames, and the term "image" may be read as "video."

[0087] It should be noted that the embodiments of the present disclosure are not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, the effects described in this specification are merely examples and are not intended to be limiting, and other effects may also be obtained.

[0088] The present disclosure can also be configured as follows.

[0089] (1) An optical device comprising: an image generating unit that emits image light; and a light guide plate into which the image light is incident, propagates inside, and is emitted to the outside, wherein the light guide plate is provided with: a first incident diffraction grating that receives first image light corresponding to a first image, diffracts the incident first image light, and couples the light into the inside of the light guide plate; a second incident diffraction grating that receives second image light corresponding to a second image that has a lower resolution than the first image, diffracts the incident second image light, and couples the light into the inside of the light guide plate; and an exit diffraction grating that diffracts the first image light and the second image light that have propagated inside the light guide plate, and couples the light to the outside of the light guide plate; and wherein, on the flat surface of the light guide plate, a boundary of the second incident diffraction grating has a portion that does not overlap with a region of the first incident diffraction grating. (2) The optical device according to (1), wherein the image generation unit includes an incident angle modulation unit that modulates the incident angle of at least a part of the first image light and makes the first image light incident on the first incident diffraction grating, and the second incident diffraction grating is disposed so that the boundary portion does not overlap with a scanning area of ​​the first image light by the incident angle modulation unit. (3) The optical device according to (1) or (2), wherein the image generation unit includes: a first optical system that has a first optical magnification and optically enlarges or reduces the first image according to the first image light incident on the first incident diffraction grating, and a second optical system that has a second optical magnification different from the first optical magnification and optically enlarges or reduces the second image according to the second image light incident on the second incident diffraction grating. (4) The optical device according to any one of (1) to (3), wherein the image generation unit has: a first display unit that displays a first display image according to the first image light incident on the first incident diffraction grating; and a second display unit that displays a second display image according to the second image light incident on the second incident diffraction grating. (5) The optical device according to (4), wherein the image generation unit has one or more display panels, and the first display unit and the second display unit are provided by the display panels.(6) The optical device according to (5), wherein at least one of the display panels is configured as a self-luminous display panel. (7) The optical device according to any of (4) to (6), wherein the first display image is an image included in a presentation image presented to a user, and the second display image is an image corresponding to a region of the presentation image excluding the first display image. (8) The optical device according to any of (1) to (3), wherein the light guide plate is configured from a first light guide plate having at least the first incident diffraction grating disposed thereon, and a second light guide plate having at least the second incident diffraction grating disposed thereon. (9) The optical device according to (8), wherein the first light guide plate has a first thickness, and the second light guide plate has a second thickness different from the first thickness. (10) The optical device according to any of (1) to (9), wherein the first incident diffraction grating has regions having different diffraction efficiencies in at least a portion thereof. (11) The optical device according to any one of (1) to (10), wherein the second incident diffraction grating has regions with different diffraction efficiencies in at least a portion of its area. (12) The optical device according to any one of (1) to (11), wherein the output diffraction grating has regions with different diffraction efficiencies in at least a portion of its area. (13) The optical device according to (1), further comprising: a gaze detection unit that detects a user's gaze; and a control unit that controls the image light output from the image generation unit based on gaze information related to the detected user's gaze. (14) The optical device according to (13), wherein the control unit controls the first image to be presented in the user's gaze direction based on the gaze information. (15) The optical device according to (1), wherein the boundary portion is a boundary between a region in which a diffraction grating is formed in the second incident diffraction grating and a region on the flat plate of the light guide plate in which a diffraction grating is not formed. (16) The optical device according to (1), wherein the angles of incidence of the first incident diffraction grating and the second incident diffraction grating and the angle of emergence of the emergence diffraction grating are substantially the same with respect to a normal to the light guide plate.(17) A light guide plate comprising: a first incident diffraction grating that receives first image light corresponding to a first image, diffracts the incident first image light, and couples the first image light to its interior; a second incident diffraction grating that receives second image light corresponding to a second image having a lower resolution than the first image, diffracts the incident second image light, and couples the second image light to its interior; and an exit diffraction grating that diffracts the first image light and the second image light that have propagated inside, and couples the first image light and the second image light to the outside for output; and on a flat plate, a boundary of the second incident diffraction grating has a portion that does not overlap with a region of the first incident diffraction grating. (18) An image generating device comprising: a first display unit that displays a first display image, which is an image included in a presentation image to be presented to a user; and a second display unit that displays a second display image, which is an image corresponding to an area of ​​the presentation image excluding the first display image; first image light corresponding to the first display image displayed on the first display unit is incident on a first incident diffraction grating arranged to couple the first image light into an interior of a light guide plate; second image light corresponding to the second display image displayed on the second display unit is incident on a second incident diffraction grating arranged to couple the second image light into an interior of the light guide plate; a first image corresponding to the first image light has a higher resolution than a second image corresponding to the second image light; and on a flat plate of the light guide plate, a boundary of the second incident diffraction grating has a portion that does not overlap with an area of ​​the first incident diffraction grating.

[0090] 1 Optical device, 11 Light guide plate, 11-1, 11-2 Light guide plate, 12 Image generating device, 13 Incident angle modulation unit, 21 ICG, 21-2 ICG, 22 ICG, 22-1 ICG, 23 OCG, 23-1, 23-2 OCG, 51 Display unit, 52 Display unit, 71 Control device, 72 Gaze detection device, 81 Gaze detection unit, 82 Fovial area determination unit, 83 Peripheral area determination unit, 84 Fovial display control unit, 85 Peripheral display control unit, 86 Incident angle control unit, 101 Wearable device, 111 Frame, 112 Front unit, 113 Temple unit, 114 End unit, 115 Headphone unit

Claims

1. An optical device comprising: an image generating unit that emits image light; and a light guide plate into which the image light is incident, propagates inside, and emitted to the outside, wherein the light guide plate is provided with: a first incident diffraction grating that receives first image light corresponding to a first image, diffracts the first image light incident and couples it into the inside of the light guide plate; a second incident diffraction grating that receives second image light corresponding to a second image which is an image having a lower resolution than the first image, diffracts the second image light incident and couples it into the inside of the light guide plate; and an exit diffraction grating that diffracts the first image light and the second image light which have propagated inside the light guide plate, and couples and emits them to the outside of the light guide plate, wherein on the flat surface of the light guide plate, a boundary of the second incident diffraction grating has a portion which does not overlap with an area of ​​the first incident diffraction grating.

2. The optical device according to claim 1, wherein the image generating section has an incident angle modulation section which modulates the incident angle of at least a portion of the first image light and causes it to enter the first incident diffraction grating, and the second incident diffraction grating is disposed so that the boundary section does not overlap with the scanning area of ​​the first image light by the incident angle modulation section.

3. The optical device according to claim 1, wherein the image generating section comprises: a first optical system having a first optical magnification, which optically enlarges or reduces the first image in response to the first image light incident on the first incident diffraction grating; and a second optical system having a second optical magnification different from the first optical magnification, which optically enlarges or reduces the second image in response to the second image light incident on the second incident diffraction grating.

4. The optical device according to claim 1, wherein the image generating section has: a first display section that displays a first display image corresponding to the first image light incident on the first incident diffraction grating; and a second display section that displays a second display image corresponding to the second image light incident on the second incident diffraction grating.

5. The optical device according to claim 4, wherein the image generating section has one or more display panels, and the first display section and the second display section are provided by the display panels.

6. The optical device according to claim 5, wherein at least one of the display panels is a self-luminous display panel.

7. The optical device of claim 4, wherein the first display image is an image included in a presentation image presented to a user, and the second display image is an image corresponding to an area of ​​the presentation image excluding the first display image.

8. The optical device according to claim 1, wherein the light guide plate comprises: a first light guide plate having at least the first incident diffraction grating arranged thereon; and a second light guide plate having at least the second incident diffraction grating arranged thereon.

9. The optical device according to claim 8, wherein the first light guide plate has a first thickness, and the second light guide plate has a second thickness different from the first thickness.

10. The optical device according to claim 1, wherein the first input diffraction grating has regions with different diffraction efficiencies in at least some areas.

11. The optical device according to claim 1, wherein the second input diffraction grating has regions with different diffraction efficiencies in at least some areas.

12. The optical device according to claim 1, wherein the exit diffraction grating has regions with different diffraction efficiencies in at least some areas.

13. The optical device of claim 1, further comprising: a gaze detection unit that detects a user's gaze; and a control unit that controls the image light emitted from the image generation unit based on gaze information regarding the detected user's gaze.

14. The optical device according to claim 13, wherein the control unit controls the first image to be presented in the line of sight of the user based on the line of sight information.

15. The optical device according to claim 1, wherein the boundary portion is a boundary between an area in which a diffraction grating is formed in the second incident diffraction grating and an area on the flat plate of the light guide plate in which a diffraction grating is not formed.

16. The optical device according to claim 1, wherein the angles of incidence of the first entrance diffraction grating and the second entrance diffraction grating and the exit angle of the exit diffraction grating are substantially the same with respect to a normal to the light guide plate.

17. A light guide plate comprising: a first incident diffraction grating which receives first image light corresponding to a first image, diffracts the first image light incident thereon, and couples it to the inside; a second incident diffraction grating which receives second image light corresponding to a second image which is an image having a lower resolution than the first image, diffracts the second image light incident thereon, and couples it to the inside; and an exit diffraction grating which diffracts the first image light and the second image light which have propagated inside, and couples them to the outside and outputs them, wherein, on a flat plate, a boundary portion of the second incident diffraction grating has a portion which does not overlap with an area of ​​the first incident diffraction grating.

18. An image generating device comprising: a first display unit that displays a first display image, which is an image included in a presentation image to be presented to a user; and a second display unit that displays a second display image, which is an image corresponding to an area of ​​the presentation image excluding the first display image; a first image light corresponding to the first display image displayed on the first display unit is incident on a first incident diffraction grating arranged to couple the first image light into an interior of a light guide plate; a second image light corresponding to the second display image displayed on the second display unit is incident on a second incident diffraction grating arranged to couple the second image light into an interior of the light guide plate; a first image corresponding to the first image light has a higher resolution than a second image corresponding to the second image light; and on the flat surface of the light guide plate, a boundary portion of the second incident diffraction grating has a portion that does not overlap with an area of ​​the first incident diffraction grating.

Images