Projection substrate and eyeglasses-type terminal

Abstract

This projection substrate comprises: a first substrate; a first metalens on which projection light for projecting image light is incident and which guides the incident projection light into the first substrate; a first projection unit which is attached to the first metalens on the side opposite the first substrate and outputs the projection light; and a first emission diffraction grating which is provided at a position different from the position on the first substrate where the first metalens is attached, and on which the projection light guided inside the first substrate is incident, and which emits at least a part of the incident projection light as image light from a display surface.

Description

Projection board and eyeglasses-type terminal

[0001] The present invention relates to a projection substrate and a method for manufacturing an eyeglass-type terminal.

[0002] Conventionally, there are known eyeglass-type devices, head-mounted displays, and the like that display two-dimensional images for a user to observe using an optical system including a waveguide or the like (see, for example, Patent Documents 1 and 2). Also, there is known a two-dimensional diffraction grating that diffracts light in two directions (see, for example, Patent Document 3).

[0003] Japanese Patent Application Publication No. 2017-207686 International Publication No. 2023 / 047488 U.S. Patent No. 8,160,411

[0004] Such eyeglass-type devices use a projection substrate with a diffraction grating formed on the substrate. A projection light source is provided outside the projection substrate to irradiate the projection substrate with projection light for displaying an image on the display surface of the projection substrate. As a result, the optical system of the device is complex, and the volume of the optical system relative to the entire device is large.

[0005] The present invention has been made in consideration of these points, and has as its object to reduce the volume of the optical system of a device that allows a user to view a two-dimensional image.

[0006] In a first aspect of the present invention, there is provided a projection substrate for projecting image light onto a display surface, the projection substrate comprising: a first substrate; a first metalens onto which projection light for projecting the image light is incident and which guides the incident projection light inside the first substrate; a first projection unit attached to the first metalens on the side opposite to the first substrate and which outputs the projection light; and a first exit diffraction grating provided at a position on the first substrate different from the position at which the first metalens is attached, onto which the projection light guided inside the first substrate is incident and which emits at least a portion of the incident projection light from the display surface as the image light.

[0007] The first metalens may be provided on the display surface and guide the incident projection light to the first output diffraction grating, the first projection portion may be attached to an input surface of the first metalens opposite to a surface facing the display surface, and the first output diffraction grating may be formed on the display surface of the first substrate or on a surface opposite to the display surface.

[0008] The projection substrate may further include an intermediate diffraction grating that guides at least a portion of the incident projection light to the first output diffraction grating, and the first metalens may be provided on the display surface and guide the incident projection light to the intermediate diffraction grating.

[0009] The projection substrate may further include a first incident diffraction grating onto which the projection light guided by the first metalens is incident and which guides at least a portion of the incident projection light toward a predetermined direction inside the first substrate.

[0010] The first metalens is provided on the display surface and guides the incident projection light to the first output diffraction grating, the first projection portion is attached to an entrance surface of the first metalens opposite an exit surface facing the display surface, the first entrance diffraction grating is formed on the display surface of the first substrate or on a surface opposite the display surface, and the first output diffraction grating is formed on the display surface of the first substrate or on a surface opposite the display surface.

[0011] The projection substrate may further include an intermediate diffraction grating that guides at least a portion of the incident projection light to the first output diffraction grating, the first metalens is provided on the display surface and guides the incident projection light to the intermediate diffraction grating, the first projection portion is attached to an incident surface of the first metalens opposite an output surface that faces the display surface, the first input diffraction grating being formed on the display surface of the first substrate or on a surface opposite the display surface, and the first output diffraction grating being formed on the display surface of the first substrate or on a surface opposite the display surface.

[0012] A plurality of the first metalens may be provided on the first substrate, the first projection units may be attached to the plurality of first metalens, the plurality of first projection units may output the projection light of different wavelengths or the projection light of different images, and the first output diffraction grating may output light obtained by combining the plurality of projection light beams output by the plurality of first projection units as the image light from the display surface.

[0013] The projection substrate further includes a second substrate disposed to overlap the first substrate, the first substrate having the first metalens and the second metalens disposed at different positions, the first projection unit that outputs first projection light attached to an incident surface of the first metalens opposite the first substrate, the first metalens guiding the incident first projection light into the first substrate, the second projection unit that outputs second projection light attached to an incident surface of the second metalens opposite the first substrate, and the second metalens guiding the incident second projection light into the second substrate. the first projection light guided within the first substrate is incident on the first exit diffraction grating, and at least a portion of the incident first projection light is output from the display surface as the image light; and the second substrate may have a second entrance diffraction grating onto which the second projection light guided by the second metalens is incident and which guides at least a portion of the incident second projection light toward a predetermined direction within the second substrate, and a second exit diffraction grating onto which the second projection light guided within the second substrate is incident and which outputs at least a portion of the incident second projection light as the image light from the display surface.

[0014] The first substrate may further include a first incident diffraction grating onto which the first projection light guided by the first metalens is incident and which guides at least a portion of the incident first projection light toward a predetermined direction inside the first substrate.

[0015] the projection substrate further includes a third substrate disposed to overlap the first substrate and the second substrate, the first substrate having a third metalens provided at a position different from the first metalens and the second metalens, the third projection unit outputting third projection light attached to an incident surface of the third metalens opposite the first substrate, the third metalens guides the incident third projection light into the third substrate, the third substrate has a third entrance diffraction grating onto which the third projection light guided by the third metalens is incident and which guides at least a portion of the incident third projection light in a predetermined direction inside the third substrate, and a third exit diffraction grating onto which the third projection light guided inside the third substrate is incident and which emits at least a portion of the incident third projection light from the display surface as the image light, and the wavelengths of the first projection light, the second projection light, and the third projection light may correspond to wavelengths of the three primary colors of light.

[0016] In a second aspect of the present invention, there is provided a glasses-type terminal worn by a user, the glasses-type terminal being provided as at least one of a lens for the user's right eye and a lens for the user's left eye, the surface facing the user's eye being the display surface, and the image light being projected onto the display surface, the glasses-type terminal comprising: the projection substrate of the first aspect; and a frame that fixes the projection substrate.

[0017] The present invention provides an advantage in that it is possible to reduce the volume of the optical system of a device that allows a user to view a two-dimensional image.

[0018] 1 shows an example of the configuration of a conventional eyeglasses-type terminal G. FIG. 1 shows an example of the configuration of an eyeglasses-type terminal 10 according to the present embodiment. FIG. 2 shows an outline of the optical path of projection light in the eyeglasses-type terminal 10 according to the present embodiment. FIG. 3 shows an outline of the optical path of projection light in the projection substrate 100 according to the present embodiment. FIG. 4 shows an example of projection light L irradiated onto the projection substrate 100 by the projection unit 120 according to the present embodiment, and an example of image light P emitted from the projection substrate 100. FIG. 5 shows an example of the configuration of the projection substrate 100 according to the present embodiment. FIG. 6 shows a first modified example of the projection substrate 100 according to the present embodiment. FIG. 7 shows an example of the cross-sectional configuration of the projection substrate 100 according to the present embodiment. FIG. 8 shows a second modified example of the projection substrate 100 according to the present embodiment. FIG. 9 shows a third modified example of the projection substrate 100 according to the present embodiment. FIG. 10 shows a fourth modified example of the projection substrate 100 according to the present embodiment.

[0019] <Configuration example of conventional eyeglasses-type terminal G> Fig. 1 shows a configuration example of a conventional eyeglasses-type terminal G. In this embodiment, three mutually orthogonal axes are defined as an X-axis, a Y-axis, and a Z-axis. The eyeglasses-type terminal G is, for example, a wearable device worn by a user. The eyeglasses-type terminal G projects image light onto a display area provided on a projection substrate S while allowing the user to observe a scene through the glasses. The eyeglasses-type terminal G includes projection substrates Sa and Sb, a frame 110, and projection units Ta and Tb. The projection substrates Sa and Sb are collectively referred to as the projection substrate S, and the projection units Ta and Tb are collectively referred to as the projection unit T.

[0020] The projection substrate S projects the incident projection light onto a display surface as image light. For example, the projection substrate S transmits at least a portion of the light incident from the first surface toward the user's eyes in the direction of the second surface. The projection substrate S also projects the light incident from the second surface as image light onto a display area provided on the second surface. Figure 1 shows an example in which the first and second surfaces of the projection substrate S are arranged approximately parallel to the XY plane. The projection substrate S is, for example, a glass substrate on which a diffraction grating that functions as a waveguide is formed.

[0021] The frame 110 fixes the projection substrate S. The projection unit T is provided on the frame 110 and irradiates the projection substrate S with projection light for projecting image light onto the projection substrate S. One or more such projection units T are provided on the frame 110. Fig. 1 shows an example in which a projection unit Ta for irradiating the projection substrate Sa with projection light L1 and a projection unit Tb for irradiating the projection substrate Sb with projection light L2 are provided on the frame 110.

[0022] The conventional eyeglasses-type terminal G described above is described in Patent Document 1, so a detailed description will be omitted here. In the conventional eyeglasses-type terminal G, the projection unit T and the projection substrate S are formed separately. Therefore, the projection unit T must be positioned so as not to interfere with the user, and an optical system must also be provided for the projection unit T, making it difficult to reduce the volume of the entire optical system. Furthermore, because the projection unit T is positioned within a limited space and irradiates projection light onto the projection substrate S using the optical system, it has been difficult to improve the efficiency of projecting image light onto the display surface of the projection substrate S and to improve optical characteristics such as the modulated transfer function (MTF).

[0023] Furthermore, in the manufacturing process of the eyeglasses-type terminal G, it was time-consuming to adjust the optical axis of the projection unit T and the input position of the projection light on the projection board S. Furthermore, the optical axis of the projection unit T could become misaligned due to impact, aging, or other factors. Therefore, the eyeglasses-type terminal according to this embodiment includes a projection board that integrates the projection board and the projection unit, thereby reducing the volume of the entire optical system compared to conventional eyeglasses-type terminals G and improving the above-mentioned characteristics. Such an eyeglasses-type terminal will now be described.

[0024] 2 shows an example of the configuration of the eyeglasses-type terminal 10 according to this embodiment. The eyeglasses-type terminal 10 is worn by a user, similar to the eyeglasses-type terminal G. The eyeglasses-type terminal 10 projects image light onto a display area of ​​a display surface provided on a projection board 100 while allowing the user to observe a scene through the glasses. The eyeglasses-type terminal 10 includes the projection board 100, a frame 110, and a projection unit 120.

[0025] The projection substrate 100 projects the incident projection light onto a display surface as image light. For example, the projection substrate 100 transmits at least a portion of the light incident from the first surface toward the user's eyes in the direction of the second surface. The projection substrate 100 also projects the light incident from the second surface onto a display area provided on the second surface as image light.

[0026] Here, the first surface of the projection substrate 100 is the surface that faces away from the user when the user wears the eyeglasses-type terminal 10. The second surface of the projection substrate 100 is the surface that faces the user's eyes when the user wears the eyeglasses-type terminal 10, and is the display surface for image light. Fig. 2 shows an example in which the first and second surfaces of the projection substrate 100 are arranged approximately parallel to the XY plane. The projection substrate 100 is, for example, a glass substrate on which a diffraction grating that functions as a waveguide is formed.

[0027] The frame 110 fixes the projection substrate 100. The frame 110 is provided with the projection substrate 100 as at least one of a lens for the user's right eye and a lens for the left eye. Fig. 2 shows an example in which the frame 110 is provided with a projection substrate 100a as a lens for the user's right eye and a projection substrate 100b as a lens for the left eye.

[0028] Alternatively, the frame 110 may be provided with one projection board 100 as a lens for the user's right eye or left eye. The frame 110 may also be provided with one projection board 100 as lenses for both eyes of the user. In this case, the frame 110 may have a goggle shape. The frame 110 has temples, a strap, and other components so that the user can wear the eyeglasses-type terminal 10. The frame 110 of the eyeglasses-type terminal 10 does not have a projection unit 120.

[0029] The projection unit 120 is provided on the projection substrate 100. For example, the projection unit 120 irradiates the projection substrate 100 with projection light including one wavelength, allowing the user to observe a monochromatic image. Alternatively, the projection unit 120 may irradiate the projection substrate 100 with projection light including multiple wavelengths, allowing the user to observe an image including multiple colors. A plurality of projection units 120 may be provided on the projection substrate 100.

[0030] <Optical Path of Projected Light in Glasses-Type Terminal 10> Fig. 3 shows an outline of the optical path of projected light in the glasses-type terminal 10 according to this embodiment. The projection unit 120 irradiates the projection light onto the incident diffraction grating 210 provided on the projection board 100. The projection unit 120 irradiates the projection light onto the incident diffraction grating 210 via a lens or the like. The projection unit 120 and the lens will be described later.

[0031] The input diffraction grating 210 guides the projection light within the substrate of the projection board 100. The projection board 100 then emits the projection light guided within the substrate from the output diffraction grating 230 as image light. The input diffraction grating 210 and the output diffraction grating 230 will be described later. Because the frame 110 does not have an optical system, the overall size, volume, etc. of the eyeglasses-type terminal 10 can be made smaller than that of a conventional eyeglasses-type terminal G.

[0032] <Optical Path of Projection Board 100> Figure 4 shows an outline of the optical path of projection light on the projection board 100 according to this embodiment. Figure 4 shows an example in which the projection unit 120 is omitted and the projection board 100 has an input diffraction grating 210, an intermediate diffraction grating 220, and an output diffraction grating 230. Projection light L enters the input diffraction grating 210, passes through the intermediate diffraction grating 220, and is output from the output diffraction grating 230 as image light P. As the projection light L travels away from the input diffraction grating 210, the intermediate diffraction grating 220 guides the projection light L part by part to the output diffraction grating 230.

[0033] Similarly, as the projection light L travels away from the intermediate diffraction grating 220, the output diffraction grating 230 outputs a portion of the projection light L as part of the image light P. In this way, the projection substrate 100 outputs the projection light L that is incident on the input diffraction grating 210 from the output diffraction grating 230 as image light P.

[0034] <Examples of Projection Light L and Image Light P> FIG. 5 shows an example of the projection light L irradiated onto the projection substrate 100 by the projection unit 120 according to this embodiment and the image light P emitted from the projection substrate 100. FIG. 5 is an enlarged view of the projection light L, with the projection unit 120 omitted. The projection unit 120 irradiates the projection light L toward, for example, a second surface of the projection substrate 100 positioned in the Z direction. The projection light L corresponds to an image to be shown to the user. For example, when the projection light L is projected onto a screen or the like placed on a surface substantially parallel to the XY plane, an image M1 is displayed on the screen for the user to observe. The image to be shown to the user is, for example, an augmented reality (AR) image or a virtual reality (VR) image. In this way, the projection unit 120 irradiates, as the projection light L, a plurality of light rays that form an image M1 on a surface substantially parallel to the XY plane.

[0035] In this embodiment, an example will be described in which the projection unit 120 projects a substantially rectangular image M1 with the X-axis direction as the longitudinal direction on a plane substantially parallel to the XY plane. Also, in Fig. 5, five of the multiple light rays emitted by the projection unit 120 are shown as input light rays 20. For example, the light ray corresponding to the upper left pixel of the image is the first input light ray 20a, the light ray corresponding to the lower left pixel of the image is the second input light ray 20b, the light ray corresponding to the central pixel of the image is the third input light ray 20c, the light ray corresponding to the upper right pixel of the image is the fourth input light ray 20d, and the light ray corresponding to the lower right pixel of the image is the fifth input light ray 20e.

[0036] The projection unit 120, for example, irradiates the projection light L onto the input diffraction grating 210 of the projection substrate 100 so as to create an erect virtual image at infinity or at a predetermined position. The projection light incident on the input diffraction grating 210 passes through the intermediate diffraction grating 220 and is output from the output diffraction grating 230 as image light P. The image light P is output from the output diffraction grating 230 and enters the user's eye, which is a distance d away from the projection substrate 100. The image light P is then focused as image M2 on the retina of the user's eye. In this way, the image light P includes a plurality of ray bundles that are focused as image M2.

[0037] 5, five of the multiple ray bundles that are emitted from the circular region C of the output diffraction grating 230 of the projection substrate 100 and form an image at a predetermined position are shown as output ray bundles 30. For example, the ray bundle that forms an image at the lower right pixel of image M2 is designated as first output ray bundle 30a, the ray bundle that forms an image at the upper right pixel of image M2 is designated as second output ray bundle 30b, the ray bundle that forms an image at the central pixel of image M2 is designated as third output ray bundle 30c, the ray bundle that forms an image at the lower left pixel of image M2 is designated as fourth output ray bundle 30d, and the ray bundle that forms an image at the upper left pixel of image M2 is designated as fifth output ray bundle 30e.

[0038] Each ray bundle corresponds to one of the multiple input light rays 20 incident from the projection unit 120. For example, the first output ray bundle 30a corresponds to the first input light ray 20a, and includes multiple light rays generated by multiple branching and multiple diffractions of the first input light ray 20a as it travels from the input diffraction grating 210 to the output diffraction grating 230 of the projection substrate 100. Similarly, the second output ray bundle 30b corresponds to the second input light ray 20b, the third output ray bundle 30c corresponds to the third input light ray 20c, the fourth output ray bundle 30d corresponds to the fourth input light ray 20d, and the fifth output ray bundle 30e corresponds to the fifth input light ray 20e.

[0039] In other words, the image M2 formed on the retina of the user's eye by the image light P emitted from the output diffraction grating 230 corresponds to the image M1 projected by the projection light L emitted by the projection unit 120. This allows the user wearing the eyeglass-type terminal 10 to feel as if the image M2 is being projected onto the second surface of the projection board 100, superimposed on the scenery seen through the projection board 100. In other words, the output diffraction grating 230 functions as a display area that displays the image M2 corresponding to the image M1 projected by the projection light L.

[0040] 5, an example is shown in which the image M2 observed by the user is an image obtained by vertically and horizontally inverting the image M1 projected by the projection light L. Note that the image M1 projected by the projection light L may be a still image, or alternatively, may be a moving image. Next, a more specific example of the projection substrate 100 will be described.

[0041] <Configuration example of projection substrate 100> Fig. 6 shows a configuration example of the projection substrate 100 according to this embodiment. Fig. 6 shows a configuration example in which the projection unit 120 is omitted. Fig. 6 shows an example in which the first surface and the second surface of the projection substrate 100 are arranged substantially parallel to the XY plane. The projection substrate 100 is a substrate for projecting projection light onto a display surface as image light. As an example, the projection substrate 100 is a glass substrate. The projection substrate 100 has an input diffraction grating 210, an intermediate diffraction grating 220, and an output diffraction grating 230.

[0042] <Example of Incident Diffraction Grating 210> The incident diffraction grating 210 receives projection light for projecting image light and guides the incident projection light toward the intermediate diffraction grating 220. Fig. 6 shows an example in which the incident diffraction grating 210 has a circular shape on a plane substantially parallel to the XY plane, but this is not limiting. The incident diffraction grating 210 may have any shape, such as an ellipse, a polygon, or a trapezoid, as long as it can guide the projection light to the intermediate diffraction grating 220.

[0043] The incident diffraction grating 210 has a plurality of first grooves 212 formed at a first period. In other words, the plurality of first grooves 212 are arranged in the same direction on the upper surface of the projection substrate 100 with a predetermined groove width and interval, thereby functioning as a diffraction grating. The incident diffraction grating 210 is a reflective or transmissive diffraction grating, and guides projection light toward the intermediate diffraction grating 220 by reflective diffraction or transmissive diffraction. The first period of the plurality of first grooves 212 is, for example, in the range of approximately 10 nm to 10 μm.

[0044] The multiple first grooves 212 are arranged, for example, in a direction from the incident diffraction grating 210 toward the intermediate diffraction grating 220. Here, the traveling direction of the projection light from the incident diffraction grating 210 toward the intermediate diffraction grating 220 is defined as a third direction. Figure 6 shows an example in which the third direction is a direction substantially parallel to the X-axis direction, and the first grooves 212 extending in a direction substantially parallel to the Y-axis direction are arranged in the third direction. Since the projection light is incident on the incident diffraction grating 210 while converging, the incident diffraction grating 210 guides the projection light to the intermediate diffraction grating 220 so that the projection light has a divergence angle centered on the third direction within the plane of the projection substrate 100.

[0045] <Example of intermediate diffraction grating 220> The intermediate diffraction grating 220 guides a portion of the projection light incident from the input diffraction grating 210 toward the output diffraction grating 230. The intermediate diffraction grating 220 is provided in a region through which the projection light passes, on a plane substantially parallel to the XY plane. The intermediate diffraction grating 220 is a reflective or transmissive diffraction grating, and guides the projection light toward the output diffraction grating 230 by reflective diffraction or transmissive diffraction. The intermediate diffraction grating 220 has, for example, a rectangular shape with the third direction as its longitudinal direction.

[0046] Since the projection light propagates while spreading around the third direction, it is preferable that the intermediate diffraction grating 220 has a shape that spreads away from the incident diffraction grating 210 as it moves away from the incident diffraction grating 210 and away from the third direction, which is the direction of propagation of the projection light passing through the incident diffraction grating 210. The intermediate diffraction grating 220 has, for example, a trapezoidal, fan-shaped, or other shape on a plane substantially parallel to the XY plane. Figure 5 shows an example in which the intermediate diffraction grating 220 has a trapezoidal shape. An intermediate diffraction grating 220 of this shape can be formed to correspond to the region where the projection light propagates while spreading in the XY plane, and can efficiently guide the projection light.

[0047] The intermediate diffraction grating 220 has a plurality of second groove portions 222 formed at a second period. In other words, the plurality of second groove portions 222 are arranged in the same direction on the upper surface of the projection substrate 100 with predetermined groove widths and intervals, thereby functioning as a diffraction grating.

[0048] The second period of the plurality of second groove portions 222 is different from the first period of the plurality of first groove portions 212. It is desirable to select an appropriate second period for guiding the projection light to the output diffraction grating 230. The second period is, for example, in the range of about 10 nm to about 10 μm.

[0049] The plurality of second grooves 222 are arranged, for example, in a predetermined direction. For example, the direction from the intermediate diffraction grating 220 toward the output diffraction grating 230 is defined as the fourth direction, and the angle between the third direction and the fourth direction is defined as the first angle. In this case, the plurality of second grooves 222 are formed in a direction tilted in the fourth direction by an angle that is half the first angle with respect to the third direction. Figure 6 shows an example in which the fourth direction is substantially parallel to the Y-axis direction, the first angle is substantially 90 degrees, and the plurality of second grooves 222 are arranged in a direction tilted in the fourth direction by approximately 45 degrees with respect to the third direction.

[0050] The intermediate diffraction grating 220 has a plurality of first divided regions 224 arranged in the direction of propagation of the incident projection light. The second grooves 222 formed in the plurality of first divided regions 224 have different depths. In other words, the second grooves 222 are formed in the intermediate diffraction grating 220 so that the proportion of light that is guided to the output diffraction grating 230 out of the incident projection light differs for each first divided region 224.

[0051] It is desirable that the intermediate diffraction grating 220 have three or more first divided regions 224. In this way, the intermediate diffraction grating 220 is divided into a plurality of first divided regions 224, and the amount of projection light guided to the output diffraction grating 230 is varied for each first divided region 224, thereby guiding projection light whose intensity varies depending on the distance from the input diffraction grating 210 to the output diffraction grating 230, while adjusting the distribution of the light amount in the direction perpendicular to the traveling direction of the projection light to be approximately constant.

[0052] For example, the second grooves 222 are formed so that the depth of the second grooves 222 provided in one first divided region 224 is greater than the depth of the second grooves 222 provided in a first divided region 224 that is closer to the incident diffraction grating 210 than the one first divided region 224. In this case, the rate of change in the depth of the second grooves 222 of two adjacent first divided regions 224 among the multiple first divided regions 224 may be greater the farther away from the incident diffraction grating 210.

[0053] 6, consider an intermediate diffraction grating 220 having three first divided regions 224. Here, of the three first divided regions 224, the first divided region 224a closest to the incident diffraction grating 210 is formed to a depth that allows the second grooves 222a to guide approximately one-quarter of the amount of projection light incident thereon to the output diffraction grating 230. In this case, the remaining approximately three-quarters of the amount of projection light incident on the first divided region 224a closest to the incident diffraction grating 210 is incident on the adjacent first divided region 224b.

[0054] The first divided region 224b, which is second closest to the incident diffraction grating 210, is formed to a depth that enables the second grooves 222b to guide approximately one-third of the amount of incident projection light to the output diffraction grating 230. In other words, the depth of the second grooves 222b of the first divided region 224b, which is second closest to the incident diffraction grating 210, is formed to be greater than the depth of the second grooves 222a so that the second divided region 224b guides 4 / 3 times the amount of light to the output diffraction grating 230 compared to the first divided region 224a closest to the incident diffraction grating 210. This first divided region 224b guides approximately one-quarter of the amount of light of the projection light that is incident on the first divided region 224a closest to the incident diffraction grating 210 to the output diffraction grating 230.

[0055] The remaining approximately half of the amount of projection light that is incident on the first divided region 224a closest to the incident diffraction grating 210 is incident on the adjacent first divided region 224c. The first divided region 224c that is third closest to the incident diffraction grating 210 is formed to a depth that enables the second grooves 222c to guide approximately half of the amount of incident projection light to the output diffraction grating 230. In other words, the depth of the second grooves 222c of the first divided region 224c that is third closest to the incident diffraction grating 210 is formed to be greater than the depth of the second grooves 222b so that the second divided region 224c guides 3 / 2 times the amount of light to the output diffraction grating 230 compared to the first divided region 224b that is second closest to the incident diffraction grating 210.

[0056] Furthermore, the second grooves 222 are formed such that the rate of change in the depth of the second grooves 222 between two adjacent first divided regions 224 out of the three first divided regions 224 increases the further away from the incident diffraction grating 210. The first divided region 224c, which is third closest to the incident diffraction grating 210, guides to the output diffraction grating 230 approximately one-quarter of the amount of projection light that was incident on the first divided region 224a, which is closest to the incident diffraction grating 210. As in the above example, by varying the amount of projection light that the intermediate diffraction grating 220 guides to the output diffraction grating 230 to a predetermined value for each first divided region 224, it can be seen that the amount of projection light that the intermediate diffraction grating 220 guides to the output diffraction grating 230 corresponding to each first divided region 224 has a substantially constant distribution.

[0057] <Example of Exit Diffraction Grating 230> The exit diffraction grating 230 guides at least a portion of the projection light incident from the intermediate diffraction grating 220 and emits it as image light from the second surface of the projection substrate 100. Fig. 6 shows an example in which the exit diffraction grating 230 has a rectangular shape with its longitudinal direction in the X-axis direction on a plane approximately parallel to the XY plane, but this is not limiting. The exit diffraction grating 230 may have any shape, such as a rectangle, square, or trapezoid with its longitudinal direction in the Y-axis direction, as long as it can guide the projection light and emit it as image light.

[0058] The output diffraction grating 230 is a diffraction grating in which a plurality of third groove portions 232 are formed at a third period. In other words, the plurality of third groove portions 232 are arranged in the same direction on the upper surface of the projection substrate 100 with predetermined groove widths and intervals, thereby functioning as a diffraction grating. The output diffraction grating 230 is a reflective or transmissive diffraction grating, and guides image light toward the user's eyes by reflective diffraction or transmissive diffraction.

[0059] The third period of the plurality of third grooves 232 provided in the output diffraction grating 230 is different from the second period of the plurality of second grooves 222 in the intermediate diffraction grating 220. The third period of the plurality of third grooves 232 in the output diffraction grating 230 may be the same as the first period of the plurality of first grooves 212 in the input diffraction grating 210. In this way, by substantially matching the periods of the diffraction gratings provided in the region where the projection light enters and the region where the image light exits, distortions and the like that occur in the image observed by the user can be reduced. The third period is, for example, in the range of approximately 10 nm to 10 μm.

[0060] The multiple third groove portions 232 are arranged, for example, in a fourth direction from the intermediate diffraction grating 220 toward the output diffraction grating 230. Fig. 6 shows an example in which the third groove portions 232 extending in the third direction are arranged in the fourth direction.

[0061] Like the intermediate diffraction grating 220, the output diffraction grating 230 has a plurality of second divided regions 234 arranged in the traveling direction of the projection light incident from the intermediate diffraction grating 220. The third grooves 232 formed in the plurality of second divided regions 234 have different depths. In other words, in the output diffraction grating 230, the third grooves 232 are formed so that the proportion of light that is output as image light out of the input projection light differs for each second divided region 234.

[0062] The output diffraction grating 230 desirably has two or more second divided regions 234. For example, the depth of the third grooves 232 provided in one second divided region 234 is greater than the depth of the third grooves 232 provided in a second divided region 234 that is closer to the intermediate diffraction grating 220 than one second divided region 234. Furthermore, when the output diffraction grating 230 has three or more second divided regions 234, the rate of change in the depth of the third grooves 232 between two adjacent second divided regions 234 may increase as the distance from the intermediate diffraction grating 220 increases.

[0063] As described above, output diffraction grating 230 is divided into a plurality of second divided regions 234, and the amount of light output as image light is made different for each second divided region 234. As a result, output diffraction grating 230, like the plurality of first divided regions 224 of intermediate diffraction grating 220, can guide projection light as image light, while adjusting the distribution of the light amount of the entire image to be approximately constant when an observer observes the image light as an image.

[0064] As described above, the projection substrate 100 according to this embodiment branches the projection light incident on the input diffraction grating 210 into different projection light beams for each of the plurality of first division regions 224 of the intermediate diffraction grating 220, and then outputs the branched projection light as image light from the output diffraction grating 230. This allows the projection substrate 100 to reduce variations in brightness of the projected image observed by the user. Furthermore, the projection substrate 100 can further reduce variations in brightness of the image by outputting image light beams for each of the plurality of second division regions 234 of the output diffraction grating 230.

[0065] Such a projection substrate 100 can be realized by forming diffraction gratings corresponding to the incident diffraction grating 210, the intermediate diffraction grating 220, and the exit diffraction grating 230 on the front or back surface of a glass substrate or the like. The grooves forming the diffraction gratings are made of, for example, resist, resin, or the like. For example, resist, resin, or the like is applied to the surface of the glass substrate. Next, a master mold is pressed against the applied resist, resin, or the like. Then, the resist, resin, or the like is hardened and the master mold is removed, thereby forming the grooves.

[0066] It is possible to simplify the optical system by using a two-dimensional diffraction grating that functions as the intermediate diffraction grating 220 and the exit diffraction grating 230. FIG. 7 shows a first modified example of the projection board 100 according to this embodiment. The projection board 100 of the first modified example shows an example in which a two-dimensional diffraction grating is used. The projection board 100 has an entrance diffraction grating 210 and a two-dimensional diffraction grating 240. The projection light L is incident on the entrance diffraction grating 210 and exits from the two-dimensional diffraction grating 240 as image light P.

[0067] In other words, the two-dimensional diffraction grating 240 functions as the intermediate diffraction grating 220 and the exit diffraction grating 230 described in Figures 4 to 6. Since the two-dimensional diffraction grating 240 is known, a detailed description thereof will be omitted here. The eyeglass-type terminal 10 and the like can be configured using the projection board 100 described above. Next, the projection unit 120 provided on the projection board 100 will be described.

[0068] 8 shows an example of the cross-sectional configuration of the projection substrate 100 according to this embodiment. The projection substrate 100 includes a first substrate 310, a first metalens 341, a first projection unit 351, a first input diffraction grating 361, and a first output diffraction grating 371.

[0069] The first substrate 310 is a substrate that transmits visible light. Fig. 8 shows an example in which the first surface 311 of the first substrate 310 is a display surface. In other words, the first surface 311 of the first substrate 310 has a display area onto which image light is projected.

[0070] Projection light for projecting image light from first projection unit 351 is incident on first metalens 341. First metalens 341 guides the incident projection light into first substrate 310. First metalens 341 is provided, for example, on first surface 311 of first substrate 310. Here, the surface of first metalens 341 onto which the projection light is incident is referred to as the incident surface, and the surface from which the projection light exits is referred to as the exit surface. The incident surface of first metalens 341 is the surface of first metalens 341 opposite to the surface facing the display surface of first substrate 310. The exit surface of first metalens 341 is the surface of first metalens 341 that faces first substrate 310.

[0071] First metalens 341 is a lens composed of a nanometer-scale artificial structure, and is formed to a thickness of several hundred nanometers or more and several micrometers or less. Because metalenses are known lenses, a detailed description of first metalens 341 will be omitted here. Figure 8 shows an example in which first metalens 341 guides projection light toward first incident diffraction grating 361.

[0072] The first projection unit 351 is attached to the incident surface of the first metalens 341 opposite to the surface facing the display surface, and outputs projection light. The first projection unit 351 is, for example, a micro LED panel. The micro LED panel is a panel formed by arranging miniaturized LEDs, and outputs a monochrome or color image. Since the micro LED panel is a known technology, a detailed description thereof will be omitted here. The first projection unit 351 may also be a liquid crystal panel or an organic EL panel.

[0073] The first projection unit 351 outputs projection light for allowing a user to observe a monochrome or color image. Note that a circuit for supplying power, a video signal, and the like to the first projection unit 351 in order for the first projection unit 351 to output the projection light is provided in the frame 110 of the eyeglass-type terminal 10.

[0074] By attaching the exit surface that outputs the projection light of first projection unit 351 formed from such a thin film to the entrance surface of first metalens 341 formed from a thin film, the projection light can be efficiently guided to first entrance diffraction grating 361. Furthermore, because first projection unit 351 and first metalens 341 can be formed small and thin, when projection substrate 100 is attached to eyeglasses-type terminal 10, first metalens 341 and first projection unit 351 can be provided in a position that does not obstruct the user's field of vision.

[0075] The first incident diffraction grating 361 and the first exit diffraction grating 371 are formed on the second surface 312 of the first substrate 310, opposite the first surface 311 (display surface). Here, the projection substrate 100 shown in FIG. 8 illustrates a configuration example that does not have an intermediate diffraction grating, similar to the projection substrate 100 of the first modified example shown in FIG. 7 . In other words, the first incident diffraction grating 361 functions as the incident diffraction grating 210 described above. Furthermore, the first exit diffraction grating 371 is a two-dimensional diffraction grating 240, and functions as the intermediate diffraction grating 220 and the exit diffraction grating 230. The operations of the first incident diffraction grating 361 and the first exit diffraction grating 371 are similar to those of the incident diffraction grating 210, the intermediate diffraction grating 220, and the exit diffraction grating 230, and therefore will not be described here.

[0076] The first input diffraction grating 361 receives the projection light guided by the first metalens 341 and guides at least a portion of the incident projection light toward the first output diffraction grating 371 on the first substrate 310. The first input diffraction grating 361 is provided with grooves that can diffract the projection light in accordance with the wavelength of the projection light output by the first projection unit 351. It goes without saying that if the intermediate diffraction grating 220 is formed on the projection substrate 100, the first input diffraction grating 361 guides the projection light toward the intermediate diffraction grating 220.

[0077] First exit diffraction grating 371 is provided at a position on first substrate 310 that is different from the position at which first metalens 341 is attached. First exit diffraction grating 371 is formed, for example, on the surface of first substrate 310 opposite to the display surface. Alternatively, first exit diffraction grating 371 may be formed on the display surface of first substrate 310.

[0078] The first exit diffraction grating 371 receives the projection light guided from the first entrance diffraction grating 361 inside the first substrate 310 and emits at least a portion of the incident projection light from the display surface as image light. The first exit diffraction grating 371 is provided with grooves that diffract the projection light in accordance with the wavelength of the projection light output by the first projector 351.

[0079] As described above, the projection substrate 100 according to this embodiment includes the first metalens 341 and the first projection unit 351, and therefore the projection light output by the first projection unit 351 can be projected onto the display surface as image light without the need to place an optical system or the like outside the projection substrate 100. Therefore, the eyeglass-type terminal 10 using the projection substrate 100 can reduce the volume of the optical system and can also reduce the weight of the terminal.

[0080] Furthermore, first metalens 341 can receive the projection light output by first projection unit 351 at the closest position, thereby improving the efficiency of projecting image light onto the display surface of projection substrate 100 and improving optical characteristics such as the modulated transfer function (MTF). Furthermore, in the process of manufacturing projection substrate 100, first projection unit 351 can be attached to first metalens 341, eliminating the need for adjusting the optical axis using another optical system or the like.

[0081] Therefore, it is possible to easily manufacture a uniform projection substrate 100, thereby reducing the manufacturing costs of the eyeglass-type terminal 10 and the projection substrate 100. Furthermore, if the first projection unit 351 and the first metalens 341 are fixed, it is possible to reduce misalignment of the optical axis due to impact, aging, or the like, and even if the optical axis does misalign, the amount of misalignment of the optical axis can be reduced.

[0082] In the above description of the projection substrate 100 according to the present embodiment, an example has been described in which the first metalens 341 and the first projection unit 351 are provided on the first substrate 310, but the present invention is not limited to this. The projection substrate 100 may include, for example, a plurality of first metalenses 341 and a plurality of first projection units 351. Such a projection substrate 100 will now be described.

[0083] <Second Modification of Projection Board 100> Figure 9 shows a second modification of the projection board 100 according to the present embodiment. In the projection board 100 of the second modification, components that operate substantially the same as those of the projection board 100 according to the present embodiment shown in Figure 8 are designated by the same reference numerals, and duplicated explanations will be omitted. The projection board 100 of the second modification includes two first metalenses 341, two first projection units 351, and two first incident diffraction gratings 361.

[0084] In this way, a plurality of first metalenses 341 may be provided on the first substrate. In this case, the first projection unit 351 is attached to each of the plurality of first metalenses 341. The two first metalenses 341 may be formed to have substantially the same shape. In this case, a common master mold may be used to form the first metalenses 341. The two first projection units 351 may, for example, output projection light of different wavelengths or projection light of different images. The two first projection units 351 may output projection light of substantially the same image.

[0085] The two first input diffraction gratings 361 receive the projection light guided by the corresponding first metalenses 341, and each guides at least a portion of the incident projection light toward the first output diffraction grating 371 on the first substrate 310. The two first input diffraction gratings 361 may be formed to have substantially the same shape. In this case, a common master mold can be used to form the first input diffraction gratings 361. The two first input diffraction gratings 361 guide the projection light to, for example, substantially the same region on the first output diffraction grating 371.

[0086] As a result, the first exit diffraction grating 371 can emit light obtained by combining the two projection light beams output by the two first projection units 351 as image light from approximately the same display area on the display surface. When the two projection light beams contain light beams of different wavelengths, the first exit diffraction grating 371 can emit mixed-color image light. In this case, for example, the wavelengths of the projection light beams output by the two first projection units 351 are set so that the first exit diffraction grating 371 can emit color or full-color image light.

[0087] The two projection lights may output substantially the same projection light. In this case, for example, if one of the first projection units 351 fails, the other first projection unit 351 can be used to continue displaying substantially the same image light on the display surface. In this case, the eyeglass-type terminal 10 may be provided with a switch or the like for switching between the two first projection units 351.

[0088] Alternatively, one first input diffraction grating 361 may guide at least a portion of the projection light to a region of the first output diffraction grating 371 that is different from the region of the first input diffraction grating 361 that is guided by the other first input diffraction grating 361. This allows the first output diffraction grating 371 to display at least a portion of one of the two image lights based on the two projection lights in a region that is different from the region that displays the other image light. In other words, the first output diffraction grating 371 can emit image light with a larger area than the display region of the image light when only one projection light is emitted.

[0089] 9 shows an example in which the projection substrate 100 of the second modified example includes two sets of the first metalens 341, the first projection unit 351, and the first incident diffraction grating 361, but is not limited to this. The projection substrate 100 of the second modified example may include three or more sets of the first metalens 341, the first projection unit 351, and the first incident diffraction grating 361.

[0090] In the above description of the projection substrate 100 according to the present embodiment, an example has been described in which the first metalens 341 guides the projection light to the first input diffraction grating 361, but the present invention is not limited to this. The first metalens 341 may also guide the projection light toward the first output diffraction grating 371. Such a projection substrate 100 will now be described.

[0091] 10 shows a third modified example of the projection board 100 according to the present embodiment. In the projection board 100 of the third modified example, parts that operate in substantially the same manner as the projection board 100 according to the present embodiment shown in FIGS. 8 and 9 are designated by the same reference numerals, and redundant explanations will be omitted.

[0092] First metalens 341 guides the incident projection light toward first exit diffraction grating 371 inside first substrate 310. In other words, first metalens 341 also has the function of first entrance diffraction grating 361. As described above, first metalens 341 can be formed of a nanometer-scale artificial structure, and therefore, by appropriately designing the shape, arrangement, period, etc. of the artificial structure, it can be configured as a lens that collects and guides the projection light toward first exit diffraction grating 371.

[0093] As described above, in the projection substrate 100 of the third modified example, the first metalens 341 has the function of guiding incident projection light toward the first exit diffraction grating 371. This means that the projection substrate 100 of the third modified example does not need to have the first entrance diffraction grating 361. This makes it possible to further simplify the projection substrate 100, and also to omit the step of manufacturing the first entrance diffraction grating 361 from the manufacturing process.

[0094] 10 shows an example in which the projection substrate 100 of the third modified example includes two pairs of first metalenses 341 and first projection units 351, but is not limited to this. The projection substrate 100 of the third modified example may include one pair of first metalenses 341 and first projection units 351, or alternatively, may include three or more pairs of first metalenses 341 and first projection units 351.

[0095] In the above embodiment, the projection substrate 100 has been described as having each component formed on a single first substrate 310. However, the present invention is not limited to this. The projection substrate 100 may include multiple substrates. Such a projection substrate 100 will now be described.

[0096] <Fourth Modification of Projection Board 100> Figure 11 shows a fourth modification of the projection board 100 according to the present embodiment. In the projection board 100 of the fourth modification, components that operate substantially the same as those of the projection board 100 according to the present embodiment shown in Figures 8 and 9 are designated by the same reference numerals, and duplicated explanations will be omitted. The projection board 100 of the fourth modification further includes a second board 320 and a third board 330.

[0097] The first substrate 310 is provided with a plurality of first metalenses 341, a plurality of first projection portions 351, a first entrance diffraction grating 361, and a first exit diffraction grating 371. Figure 11 shows an example in which the plurality of first metalenses 341 are formed as a first metalense 341, a second metalense 342, and a third metalense 343. The first metalense 341, the second metalense 342, and the third metalense 343 are provided at different positions on the display surface of the first substrate 310.

[0098] 11 also shows an example in which the multiple first projection units 351 include a first projection unit 351, a second projection unit 352, and a third projection unit 353. The first projection unit 351 is attached to the incident surface of the first metalens 341 opposite to the first substrate 310, and outputs a first projection light. The second projection unit 352 is attached to the incident surface of the second metalens 342 opposite to the first substrate 310, and outputs a second projection light. The third projection unit 353 is attached to the incident surface of the third metalens 343 opposite to the first substrate 310, and outputs a third projection light.

[0099] First metalens 341 guides the incident first projection light into the inside of first substrate 310. First input diffraction grating 361 receives the first projection light guided by first metalens 341, and guides at least a portion of the incident first projection light toward first output diffraction grating 371 inside first substrate 310. First output diffraction grating 371 receives the first projection light guided inside first substrate 310, and emits at least a portion of the incident first projection light from the display surface as image light.

[0100] Second metalens 342 guides the second projection light incident from second projection unit 352 into the interior of second substrate 320. Third metalens 343 guides the third projection light incident from third projection unit 353 into the interior of third substrate 330.

[0101] The second substrate 320 is disposed so as to overlap the first substrate 310. The second substrate 320 is provided with a second entrance diffraction grating 362 and a second exit diffraction grating 372. Fig. 11 shows an example in which the second entrance diffraction grating 362 and the second exit diffraction grating 372 are provided on the surface of the second substrate 320 opposite to the first substrate 310. Note that at least one of the second entrance diffraction grating 362 and the second exit diffraction grating 372 may be provided on the surface of the second substrate 320 facing the first substrate 310.

[0102] The second input diffraction grating 362 receives the second projection light guided by the second metalens 342 of the first substrate 310 and guides at least a portion of the incident second projection light toward the second output diffraction grating 372 inside the second substrate 320. The second input diffraction grating 362 may have a shape similar to that of the first input diffraction grating 361. In this case, a common master mold can be used to form the first input diffraction grating 361 and the second input diffraction grating 362. It goes without saying that if the second substrate 320 has the intermediate diffraction grating 220, the second input diffraction grating 362 guides the second projection light toward the intermediate diffraction grating 220.

[0103] The second output diffraction grating 372 receives the second projection light guided inside the second substrate 320 and outputs at least a portion of the incident second projection light as image light to the first output diffraction grating 371 of the first substrate 310. This allows the second output diffraction grating 372 to emit image light based on the second projection light from the display surface of the first substrate 310 via the first output diffraction grating 371. The second output diffraction grating 372 may have the same shape as the first output diffraction grating 371. In this case, a common master mold can be used to form the first output diffraction grating 371 and the second output diffraction grating 372.

[0104] The third substrate 330 is disposed so as to overlap the first substrate 310 and the second substrate 320. The third substrate 330 is provided with a third entrance diffraction grating 363 and a third exit diffraction grating 373. Fig. 11 shows an example in which the third entrance diffraction grating 363 and the third exit diffraction grating 373 are provided on the surface of the third substrate 330 opposite to the first substrate 310. Note that at least one of the third entrance diffraction grating 363 and the third exit diffraction grating 373 may be provided on the surface of the third substrate 330 facing the first substrate 310.

[0105] The third input diffraction grating 363 receives the third projection light guided by the third metalens 343 of the first substrate 310 and guides at least a portion of the incident third projection light toward the third output diffraction grating 373 inside the third substrate 330. The third input diffraction grating 363 may have a shape similar to that of the first input diffraction grating 361. In this case, a common master mold can be used to form the first input diffraction grating 361 and the third input diffraction grating 363. It goes without saying that if the third substrate 330 has the intermediate diffraction grating 220, the third input diffraction grating 363 guides the third projection light toward the intermediate diffraction grating 220.

[0106] The third output diffraction grating 373 receives the third projection light guided inside the third substrate 330 and outputs at least a portion of the incident third projection light as image light to the first output diffraction grating 371 of the first substrate 310. This allows the third output diffraction grating 373 to emit image light based on the third projection light from the display surface of the first substrate 310 via the first output diffraction grating 371. The third output diffraction grating 373 may have the same shape as the first output diffraction grating 371. In this case, a common master mold can be used to form the first output diffraction grating 371 and the third output diffraction grating 373.

[0107] As a result, the first output diffraction grating 371 of the first substrate 310 can output image light that is a combination of the first projection light, the second projection light, and the third projection light. Here, the wavelengths of the first projection light, the second projection light, and the third projection light preferably correspond to the wavelengths of the three primary colors of light. This allows the projection substrate 100 to output color or full-color image light.

[0108] Furthermore, at least a portion of the display area for the image light based on the first projection light emitted by the first output diffraction grating 371 may be different from the display area for the image light based on the second projection light emitted by the second output diffraction grating 372. Alternatively, or in addition, at least a portion of the display area for the image light based on the first projection light emitted by the first output diffraction grating 371 may be different from the display area for the image light based on the third projection light emitted by the third output diffraction grating 373. This allows the projection substrate 100 to display image light over a wider display area.

[0109] In the above-described projection substrate 100 of the fourth modified example, an example has been described in which the first substrate 310 has the first incident diffraction grating 361, but the present invention is not limited to this. As in the projection substrate 100 of the third modified example shown in FIG. 10 , the first metalens 341 may also have the function of the first incident diffraction grating 361. In this case, the projection substrate 100 can omit the first incident diffraction grating 361.

[0110] Furthermore, a metalens may be provided on the second substrate 320 instead of the second incident diffraction grating 362. Similarly, a metalens may be provided on the third substrate 330 instead of the third incident diffraction grating 363.

[0111] In the above fourth modified example of the projection substrate 100, an example in which the projection substrate 100 has three substrates has been described, but the present invention is not limited to this. The projection substrate 100 may have two substrates, or alternatively, may have four or more substrates.

[0112] In the above embodiment of the projection substrate 100, an example has been described in which the metalens and projection unit are provided on the first surface 311 (display surface) of the projection substrate 100, but the present invention is not limited to this. The metalens and projection unit may also be provided on the second surface 312 of the projection substrate 100. In this case, if an incident diffraction grating is formed, it goes without saying that the incident diffraction grating is provided on the first surface 311 of the projection substrate 100.

[0113] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments.

[0114] 10 Eyeglass-type terminal 20 Input light beam 30 Output light beam bundle 100 Projection substrate 110 Frame 120 Projection unit 210 Input diffraction grating 212 First groove portion 220 Intermediate diffraction grating 222 Second groove portion 224 First division area 230 Output diffraction grating 232 Third groove portion 234 Second division area 240 Two-dimensional diffraction grating 310 First substrate 311 First surface 312 Second surface 320 Second substrate 330 Third substrate 341 First metalens 342 Second metalens 343 Third metalens 351 First projection unit 352 Second projection unit 353 Third projection unit 361 First input diffraction grating 362 Second input diffraction grating 363 Third input diffraction grating 371 First output diffraction grating 372 Second output diffraction grating 373 Third exit diffraction grating

Claims

1. A projection substrate for projecting image light onto a display surface, comprising: a first substrate; a first metalens onto which projection light for projecting the image light is incident and which guides the incident projection light inside the first substrate; a first projection unit attached to the first metalens on the side opposite the first substrate and which outputs the projection light; and a first exit diffraction grating provided at a position on the first substrate different from the position at which the first metalens is attached, onto which the projection light guided inside the first substrate is incident and which emits at least a portion of the incident projection light from the display surface as the image light.

2. The projection substrate described in claim 1, wherein the first metalens is provided on the display surface and guides the incident projection light to the first output diffraction grating, the first projection unit is attached to an input surface of the first metalens opposite to the surface facing the display surface, and the first output diffraction grating is formed on the display surface of the first substrate or on the surface opposite to the display surface.

3. The projection board according to claim 1, further comprising an intermediate diffraction grating that guides at least a portion of the incident projection light to the first output diffraction grating, wherein the first metalens is provided on the display surface and guides the incident projection light to the intermediate diffraction grating.

4. The projection substrate according to claim 1, further comprising a first incident diffraction grating onto which the projection light guided by the first metalens is incident and which guides at least a portion of the incident projection light toward a predetermined direction inside the first substrate.

5. The projection board described in claim 4, wherein the first metalens is provided on the display surface and guides the incident projection light to the first exit diffraction grating, the first projection unit is attached to an entrance surface of the first metalens opposite an exit surface facing the display surface, the first entrance diffraction grating is formed on the display surface of the first substrate or on the surface opposite the display surface, and the first exit diffraction grating is formed on the display surface of the first substrate or on the surface opposite the display surface.

6. The projection board according to claim 4, further comprising an intermediate diffraction grating that guides at least a portion of the incident projection light to the first exit diffraction grating, wherein the first metalens is provided on the display surface and guides the incident projection light to the intermediate diffraction grating, the first projection portion is attached to an entrance surface of the first metalens opposite an exit surface that faces the display surface, the first entrance diffraction grating is formed on the display surface of the first substrate or on the surface opposite the display surface, and the first exit diffraction grating is formed on the display surface of the first substrate or on the surface opposite the display surface.

7. The projection substrate described in claim 1, wherein a plurality of the first metalenses are provided on the first substrate, the first projection units are respectively attached to the plurality of first metalenses, the plurality of first projection units output the projection light of different wavelengths or the projection light of different images, and the first output diffraction grating outputs light obtained by combining the plurality of projection light beams output by the plurality of first projection units as the image light from the display surface.

8. The device further comprises a second substrate disposed to overlap the first substrate, the first substrate having the first metalens and second metalens disposed at different positions, the first projection unit that outputs first projection light attached to an incident surface of the first metalens opposite the first substrate, the first metalens guiding the incident first projection light into the first substrate, the second projection unit that outputs second projection light attached to an incident surface of the second metalens opposite the first substrate, the second metalens guiding the incident second projection light into the second substrate, the first exit diffraction grating receiving the first projection light guided within the first substrate and outputting at least a portion of the incident first projection light from the display surface as the image light, and the second substrate having: a second entrance diffraction grating receiving the second projection light guided by the second metalens and guiding at least a portion of the incident second projection light in a predetermined direction within the second substrate; a second exit diffraction grating into which the second projection light guided inside the second substrate is incident and which emits at least a portion of the incident second projection light from the display surface as the image light.

9. The projection substrate of claim 8, wherein the first substrate further comprises a first incident diffraction grating onto which the first projection light guided by the first metalens is incident and which guides at least a portion of the incident first projection light toward a predetermined direction inside the first substrate.

10. The projection substrate according to claim 8, further comprising a third substrate arranged to overlap the first substrate and the second substrate, wherein the first substrate has a third metalens provided at a position different from the first metalens and the second metalens, wherein a third projection unit that outputs third projection light is attached to an incident surface of the third metalens opposite the first substrate, and the third metalens guides the incident third projection light into the third substrate, and wherein the third substrate has: a third incident diffraction grating onto which the third projection light guided by the third metalens is incident and which guides at least a portion of the incident third projection light toward a predetermined direction inside the third substrate, and a third exit diffraction grating onto which the third projection light guided inside the third substrate is incident and which emits at least a portion of the incident third projection light from the display surface as the image light, and wherein the wavelengths of the first projection light, the second projection light, and the third projection light correspond to the wavelengths of the three primary colors of light.

11. A glasses-type terminal worn by a user, comprising: the projection board according to any one of claims 1 to 10, which is provided as at least one of a lens for the user's right eye and a lens for the user's left eye, the surface facing the user's eye being the display surface onto which the image light is projected; and a frame that fixes the projection board.

Images