Projection substrate, substrate for diffraction, spectacle-type terminal, and method for manufacturing projection substrate

Abstract

Provided is a projection substrate comprising: an incident diffraction grating on which projection light for projecting image light is incident and which guides at least a portion of the incident projection light toward a predetermined direction in the projection substrate; an emission diffraction grating which is provided at a position in a predetermined direction from the incident diffraction grating, on which the projection light guided by the incident diffraction grating is incident, and which emits, from a display surface, at least a portion of the incident projection light as image light; and a filling material which is filled in groove parts of the incident diffraction grating and the emission diffraction grating and has a refractive index smaller than that of the incident diffraction grating and the emission diffraction grating.

Description

Projection substrate, diffraction substrate, eyeglass-type terminal, and method for manufacturing projection substrate

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

[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 used a projection substrate with a diffraction grating formed on the substrate. Conventional projection substrates diffract incident light using the difference in refractive index between the material forming the diffraction grating and air, so the diffraction grating was formed so that it was in contact with an air layer. However, diffraction gratings in contact with an air layer were vulnerable to impacts, and the substrate itself could easily become distorted.

[0005] The present invention has been made in view of these points, and has as its object to prevent an air gap from being formed on both sides of a diffraction grating formed on a substrate.

[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: an incident diffraction grating onto which projection light for projecting the image light is incident and which guides at least a portion of the incident projection light toward a predetermined direction within the projection substrate; an exit diffraction grating which is provided at a position in the predetermined direction from the incident diffraction grating, onto which the projection light guided by the incident diffraction grating is incident and which emits at least a portion of the incident projection light from the display surface as the image light; and a filling material which is filled in grooves of the incident diffraction grating and the exit diffraction grating and has a refractive index smaller than that of the incident diffraction grating and the exit diffraction grating.

[0007] The filler material may include mesoporous silica having a porous structure, and may have a refractive index of less than 1.2, a visible light transmittance of more than 90%, and a haze value of less than 0.5.

[0008] The incident diffraction grating and the exit diffraction grating may be formed on a first surface of the projection substrate opposite the display surface, the exit diffraction grating allows at least a portion of the incident projection light to pass through the inside of the projection substrate and exit from the display surface, and the filling material may cover the incident diffraction grating and the exit diffraction grating.

[0009] The filling material covers the incident diffraction grating and the exit diffraction grating, and may further include a protective film for covering and protecting the surface of the filling material, and an adhesive sheet provided between the protective film and the filling material and adhering the protective film to the filling material.

[0010] The protective film may be a triacetyl cellulose film. At least one of an optical lens and an optical film having an anti-reflection film may be further provided on the surface of the protective film opposite to the pressure-sensitive adhesive sheet.

[0011] The incident diffraction grating and the exit diffraction grating are formed on the display surface of the projection substrate, the filling material covers the incident diffraction grating and the exit diffraction grating, and the filling material may be further formed on a first surface of the projection substrate opposite the display surface.

[0012] In a second aspect of the present invention, there is provided a diffraction substrate for diffracting incident light, the diffraction substrate comprising: a diffraction grating onto which the incident light is incident and which diffracts at least a portion of the incident light and outputs the light to the outside; and a filler material which is filled in grooves of the diffraction grating and has a refractive index smaller than that of the diffraction grating.

[0013] In a third aspect of the present invention, there is provided a glasses-type terminal worn by a user, the glasses-type terminal comprising: the projection substrate of the first aspect, 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, and which projects the image light onto the display surface with a surface facing the user's eye as the display surface; a frame that fixes the projection substrate; and a projection unit that is provided on the frame and irradiates the projection light onto the incident diffraction grating of the projection substrate to project the image light onto the display surface.

[0014] In a fourth aspect of the present invention, there is provided a method for manufacturing a projection substrate for projecting image light onto a display surface, the method comprising the steps of forming an incident diffraction grating and an exit diffraction grating on a first surface of a substrate, and applying a liquid agent containing a filler material having a smaller refractive index than the incident diffraction grating and the exit diffraction grating to the formed incident diffraction grating, wherein projection light for projecting the image light is incident on the incident diffraction grating and the exit diffraction grating guides at least a portion of the incident projection light toward a predetermined direction within the substrate, wherein the exit diffraction grating is provided at a position in the predetermined direction from the incident diffraction grating, and the projection light guided by the incident diffraction grating is incident on the exit diffraction grating and at least a portion of the incident projection light is output from the display surface as the image light, and the liquid agent contains mesoporous silica and a solvent as the filler material, and a solid content of the mesoporous silica is 5% or more and 20% or less.

[0015] According to the present invention, it is possible to prevent an air gap from being formed on both sides of the diffraction grating formed on the substrate.

[0016] 1 shows an example of the configuration of the eyeglass-type terminal 10 according to the present embodiment. 2 shows an outline of the optical path of the projection light in the eyeglass-type terminal 10 according to the present embodiment. 3 shows an outline of the optical path of the projection light in the projection substrate 100 according to the present embodiment. 4 shows an example of the projection light L irradiated onto the projection substrate 100 by the projection unit 120 according to the present embodiment, and the image light P emitted from the projection substrate 100. 5 shows an example of the configuration of the projection substrate 100 according to the present embodiment. 6 shows a first modified example of the projection substrate 100 according to the present embodiment. 7 shows an example of the cross-sectional configuration of the projection substrate 100 according to the present embodiment. 8 shows a second modified example of the projection substrate 100 according to the present embodiment. 9 shows an example of the manufacturing flow of the projection substrate 100 according to the present embodiment. 10 shows an example of the configuration of the process of forming the projection substrate 100 according to the present embodiment. 11 shows a third modified example of the projection substrate 100 according to the present embodiment. 12 shows a fourth modified example of the projection substrate 100 according to the present embodiment.

[0017] <Configuration example of eyeglasses-type terminal 10> Fig. 1 shows a configuration example of an eyeglasses-type terminal 10 according to this embodiment. In this embodiment, three mutually orthogonal axes are defined as an X-axis, a Y-axis, and a Z-axis. The eyeglasses-type terminal 10 is, for example, a wearable device worn by a user. The eyeglasses-type terminal 10 projects image light onto a display area provided on a projection substrate 100 while allowing the user to observe a scene through the glasses. The eyeglasses-type terminal 10 includes the projection substrate 100, a frame 110, and a projection unit 120.

[0018] The projection substrate 100 projects 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 as image light onto a display area provided on the second surface. Here, the first surface of the projection substrate 100 is the surface facing away from the user when the user wears the eyeglass-type terminal 10. The second surface of the projection substrate 100 is the surface facing the user's eyes when the user wears the eyeglass-type terminal 10, and is the display surface for the image light. FIG. 1 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 functioning as a waveguide is formed. The projection substrate 100 will be described later.

[0019] 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. 1 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.

[0020] 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 parts that allow the user to wear the eyeglass-type terminal 10.

[0021] The projection unit 120 is provided on the frame 110 and irradiates projection light toward the projection substrate 100 to project image light onto the projection substrate 100. One or more such projection units 120 are provided on the frame 110. Fig. 1 shows an example in which a projection unit 120a for irradiating projection light L1 onto the projection substrate 100a and a projection unit 120b for irradiating projection light L2 onto the projection substrate 100b are provided on the frame 110.

[0022] The projection unit 120 may be provided at a portion of the frame 110 where the projection substrate 100 is fixed, or may be provided at a temple or the like of the frame 110. It is desirable that the projection unit 120 be provided so as to be integrated with the frame 110. 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.

[0023] 2 shows an outline of the optical path of projection light in the eyeglass-type terminal 10 according to this embodiment. The projection unit 120 irradiates the projection light onto an incident area 210 provided on the projection substrate 100. The incident area 210 guides the projection light within the substrate of the projection substrate 100. The projection substrate 100 then emits the projection light guided within the substrate from an emission area 230 as image light. The incident area 210 and the emission area 230 will be described later.

[0024] 3 shows an outline of the optical path of projection light on the projection substrate 100 according to this embodiment. The projection substrate 100 has an incident region 210, a branching region 220, and an exit region 230. Projection light L enters the incident region 210, passes through the branching region 220, and exits from the exit region 230 as image light P. The branching region 220 guides the projection light L part by part to the exit region 230 as the projection light L travels away from the incident region 210.

[0025] Similarly, as the projection light L travels away from the branching region 220, the emission region 230 also emits a portion of the projection light L as part of the image light P. In this way, the projection board 100 emits the projection light L that has entered the entrance region 210 from the emission region 230 as image light P.

[0026] <Examples of Projection Light L and Image Light P> FIG. 4 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. The projection unit 120 irradiates the projection light L, for example, toward the second surface of the projection substrate 100 located 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 created by a processor included in the projection unit 120. 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.

[0027] 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. 4, 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.

[0028] The projection unit 120, for example, irradiates the projection light L onto the entrance region 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 entrance region 210 passes through the branching region 220 and is emitted from the exit region 230 as image light P. The image light P is emitted from the exit region 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 light beams that are focused as image M2.

[0029] 4, five of the multiple ray bundles that are emitted from the circular region C of the emission region 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 as the lower right pixel of the image is designated as the first output ray bundle 30a, the ray bundle that forms an image as the upper right pixel of the image is designated as the second output ray bundle 30b, the ray bundle that forms an image as the central pixel of the image is designated as the third output ray bundle 30c, the ray bundle that forms an image as the lower left pixel of the image is designated as the fourth output ray bundle 30d, and the ray bundle that forms an image as the upper left pixel of the image is designated as the fifth output ray bundle 30e.

[0030] 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 incident region 210 to the exit region 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.

[0031] In other words, the image M2 formed on the retina of the user's eye by the image light P emitted from the emission region 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 substrate 100, superimposed on the scenery seen through the projection substrate 100. In other words, the emission region 230 functions as a display region that displays the image M2 corresponding to the image M1 projected by the projection light L.

[0032] 4, 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.

[0033] <Configuration Example of Projection Substrate 100> Fig. 5 shows a configuration example of the projection substrate 100 according to this embodiment. Fig. 5 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 incident projection light onto a display surface as image light. The projection substrate 100 is, for example, a glass substrate. The projection substrate 100 has an incident region 210, a branching region 220, and an exit region 230. Note that Fig. 5 omits the filling material formed on the surface of the projection substrate 100, the components stacked on the surface of the projection substrate 100, and the like. Such filling material and the components stacked on the surface of the projection substrate 100 will be described later.

[0034] <Example of Incident Region 210> The incident region 210 receives projection light for projecting image light and guides the incident projection light toward the branching region 220. Fig. 5 shows an example in which the incident region 210 has a circular shape on a plane substantially parallel to the XY plane, but is not limited to this. The incident region 210 may have any shape, such as an ellipse, a polygon, or a trapezoid, as long as it can guide the projection light toward the branching region 220.

[0035] The incident region 210 has an incident diffraction grating in which a plurality of first grooves 212 are 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 region 210 has a reflective or transmissive incident diffraction grating and guides projection light toward the branching region 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.

[0036] The multiple first grooves 212 are arranged, for example, in a direction from the incident region 210 toward the branching region 220. Here, the traveling direction of the projection light from the incident region 210 toward the branching region 220 is defined as a third direction. Fig. 5 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 region 210 while converging, the incident region 210 guides the projection light to the branching region 220 so that the projection light has a divergence angle centered on the third direction within the plane of the projection substrate 100.

[0037] <Example of Branching Region 220> The branching region 220 guides a portion of the projection light incident from the entrance region 210 toward the exit region 230. The branching region 220 is provided in a region through which the projection light passes, on a plane substantially parallel to the XY plane. The branching region 220 has a reflective intermediate diffraction grating, and guides the projection light toward the exit region 230 by reflective diffraction. The branching region 220 has, for example, a rectangular shape with the third direction as its longitudinal direction.

[0038] Since the projection light propagates while spreading around the third direction, it is preferable that the branching region 220 has a shape that spreads away from the entrance region 210 and away from the third direction, which is the propagation direction of the projection light passing through the entrance region 210, as it moves away from the entrance region 210. The branching region 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 branching region 220 has a trapezoidal shape. A branching region 220 of this shape can be formed corresponding to a region where the projection light propagates while spreading in the XY plane, and can efficiently guide the projection light.

[0039] The branching region 220 has an intermediate diffraction grating in which a plurality of second grooves 222 are formed at a second period. In other words, the plurality of second grooves 222 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 branching region 220 functions as, for example, a reflective intermediate diffraction grating and guides the projection light to the emission region 230.

[0040] 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 emission region 230. The second period is, for example, in the range of about 10 nm to about 10 μm.

[0041] The plurality of second grooves 222 are arranged, for example, in a predetermined direction. For example, the direction from the branching region 220 toward the emission region 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 inclined toward the fourth direction by an angle that is half the first angle with respect to the third direction. Figure 5 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 inclined toward the fourth direction by approximately 45 degrees with respect to the third direction.

[0042] The branching region 220 has a plurality of first dividing regions 224 arranged in the traveling direction of the incident projection light. The second grooves 222 formed in the plurality of first dividing regions 224 have different depths. In other words, the second grooves 222 are formed in the branching region 220 so that the proportion of the incident projection light that is guided to the emission region 230 differs for each first dividing region 224.

[0043] It is desirable that the branching region 220 has three or more first divided regions 224. In this way, the branching region 220 is divided into a plurality of first divided regions 224, and the amount of projection light guided to the emission region 230 is varied for each first divided region 224, thereby guiding projection light whose intensity varies depending on the distance from the incidence region 210 to the emission region 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.

[0044] 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 region 210 than the one first divided region 224. In this case, the rate of change in the depth of the second grooves 222 between two adjacent first divided regions 224 among the plurality of first divided regions 224 may be greater the farther away from the incident region 210.

[0045] 5, consider a branch region 220 having three first divided regions 224. Here, the first divided region 224a, which is closest to the incident region 210 among the three first divided regions 224, has a depth of the second groove 222a formed so that approximately one-quarter of the amount of incident projection light is guided to the output region 230. In this case, the remaining approximately three-quarters of the amount of projection light that is incident on the first divided region 224a closest to the incident region 210 is incident on the adjacent first divided region 224b.

[0046] The depth of the second groove 222b of the first divided region 224b second closest to the entrance region 210 is formed so that the second groove 222b guides approximately one-third of the amount of incident projection light to the exit region 230. In other words, the depth of the second groove 222b of the first divided region 224b second closest to the entrance region 210 is formed greater than the depth of the second groove 222a so that the first divided region 224b guides 4 / 3 times the amount of light to the exit region 230 compared to the first divided region 224a closest to the entrance region 210. This first divided region 224b guides approximately one-quarter of the amount of projection light incident on the first divided region 224a closest to the entrance region 210 to the exit region 230.

[0047] The remaining approximately half of the amount of projection light that is incident on the first divided region 224a that is closest to the incident region 210 is incident on the adjacent first divided region 224c. The first divided region 224c that is third closest to the incident region 210 has a depth of the second groove 222c formed so as to guide approximately half of the amount of incident projection light to the output region 230. In other words, the depth of the second groove 222c of the first divided region 224c that is third closest to the incident region 210 is formed greater than the depth of the second groove 222b so as to guide 3 / 2 times the amount of light to the output region 230 compared to the first divided region 224b that is second closest to the incident region 210.

[0048] Furthermore, the rate of change in the depth of the second groove portions 222 of two adjacent first divided regions 224 out of the three first divided regions 224 is formed so that the rate of change increases the farther away from the incident region 210. The first divided region 224c, which is third closest to the incident region 210, guides to the output region 230 approximately one-fourth the amount of projection light that was incident on the first divided region 224a, which is closest to the incident region 210. As in the above example, by varying the amount of projection light guided to the output region 230 for each first divided region 224 to a predetermined value, it can be seen that the branch region 220 can guide the projection light to the output region 230 while maintaining a substantially constant distribution of the amount of projection light guided to the output region 230 corresponding to each first divided region 224.

[0049] <Example of Emission Region 230> The emission region 230 guides at least a portion of the projection light incident from the branch region 220 and emits it as image light from the second surface of the projection substrate 100. Fig. 5 shows an example in which the emission region 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 emission region 230 only needs to be able to guide the projection light and emit it as image light, and may have a shape such as a rectangle, square, or trapezoid with its longitudinal direction in the Y-axis direction.

[0050] The emission region 230 has an emission 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 a predetermined groove width and interval, thereby functioning as a diffraction grating. The emission region 230 has a reflective or transmissive emission diffraction grating and guides image light toward the user's eyes by reflective diffraction or transmissive diffraction.

[0051] The third period of the plurality of third groove portions 232 provided in the emission region 230 is different from the second period of the plurality of second groove portions 222 in the branch region 220. The third period of the plurality of third groove portions 232 in the emission region 230 may be the same as the first period of the plurality of first groove portions 212 in the incidence region 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 occurring 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.

[0052] The plurality of third grooves 232 are arranged, for example, in a fourth direction from the branching region 220 toward the emission region 230. Fig. 5 shows an example in which the third grooves 232 extending in the third direction are arranged in the fourth direction.

[0053] Like the branching region 220, the emission region 230 has a plurality of second division regions 234 arranged in the traveling direction of the projection light incident from the branching region 220. The third groove portions 232 formed in the plurality of second division regions 234 have different depths. In other words, the third groove portions 232 are formed in the emission region 230 so that the proportion of light that is emitted as image light out of the input projection light differs for each second division region 234.

[0054] It is desirable that the emission region 230 has two or more second divide regions 234. For example, the depth of the third groove portion 232 provided in one second divide region 234 is formed to be greater than the depth of the third groove portion 232 provided in a second divide region 234 that is closer to the branch region 220 than the one second divide region 234. Furthermore, when the emission region 230 has three or more second divide regions 234, the rate of change in the depth of the third groove portion 232 of two adjacent second divide regions 234 may be greater the farther away from the branch region 220.

[0055] As described above, the emission region 230 is divided into a plurality of second divided regions 234, and the amount of light emitted as image light is made different for each second divided region 234. As a result, like the plurality of first divided regions 224 of the branch region 220, the emission region 230 can guide the projection light as image light, and can adjust the distribution of the amount of light across the entire image to be approximately constant when the observer observes the image light as an image.

[0056] As described above, the projection substrate 100 according to this embodiment branches the projection light incident on the entrance region 210 into different proportions for each of the plurality of first divided regions 224 of the branch region 220, and then emits the projection light as image light from the exit region 230. This allows the projection substrate 100 to reduce variations in the brightness of the projected image observed by the user. Furthermore, the projection substrate 100 can further reduce variations in the brightness of the image by emitting image light at different proportions for each of the plurality of second divided regions 234 in the exit region 230 as well.

[0057] Such a projection substrate 100 can be realized by forming a diffraction grating corresponding to the incident region 210, the branching region 220, and the exit region 230 on the front or back surface of a glass substrate or the like. The grooves forming the diffraction grating are made of, for example, resist, resin, or the like.

[0058] It is possible to simplify the optical system by using a two-dimensional diffraction grating that functions as the branching region 220 and the exit region 230. FIG. 6 shows a first modified example of the projection substrate 100 according to this embodiment. The projection substrate 100 of the first modified example shows an example in which a two-dimensional diffraction grating is used. The projection substrate 100 has an entrance region 210 and a two-dimensional diffraction grating 240. Projection light L is incident on the entrance region 210 and exits from the two-dimensional diffraction grating 240 as image light P. In other words, the two-dimensional diffraction grating 240 functions as the branching region 220 and the exit region 230 described in FIG. 2. The two-dimensional diffraction grating 240 is known, so a detailed description thereof will be omitted here.

[0059] The above-described projection substrate 100 can be used to configure the eyeglasses-type terminal 10, etc. However, conventionally, it has been difficult to manufacture the substrates used in the eyeglasses-type terminal 10, etc. A diffraction grating formed on a conventional substrate diffracts incident light by utilizing the difference in refractive index between the material forming the diffraction grating and air.

[0060] Therefore, since the diffraction grating is formed in contact with an air layer, it is vulnerable to impacts and the substrate itself is prone to distortion. Furthermore, vacuum bonding processes and the like cannot be used in the process of forming conventional substrates that are in contact with an air layer. Furthermore, conventional substrates are prone to contamination by foreign matter such as water droplets. To protect such substrates, a complex structure, such as a layer structure to protect the diffraction grating on top of the air layer, was required. Therefore, the projection substrate 100 of this embodiment has a simple structure, is resistant to impacts, is resistant to distortion, can be subjected to vacuum bonding processes and the like, and reduces the intrusion of foreign matter such as water droplets. Such a projection substrate 100 is now described.

[0061] <Example of Cross-Sectional Configuration of Projection Substrate 100> Fig. 7 shows an example of the cross-sectional configuration of the projection substrate 100 according to this embodiment. Fig. 7 shows an example in which an input diffraction grating 310 and an output diffraction grating 320 are formed on the first surface 301 of the projection substrate 100. In other words, an input region 210 and an output region 230 are formed on the first surface 301 of the projection substrate 100. The projection substrate 100 further includes a filler material 330.

[0062] When the projection substrate 100 shown in Fig. 7 is the projection substrate 100 described in Fig. 5, an intermediate diffraction grating (branching region 220) is further formed on the first surface 301 of the projection substrate 100, but the intermediate diffraction grating is not shown in Fig. 7. When the projection substrate 100 shown in Fig. 7 is the projection substrate 100 described in Fig. 6, the exit diffraction grating 320 is a two-dimensional diffraction grating 240, and functions as the branching region 220 and the exit region 230.

[0063] As described above, the input diffraction grating 310 receives projection light for projecting image light and guides at least a portion of the incident projection light toward a predetermined direction within the projection substrate 100. For example, in the case of the projection substrate 100 described in Fig. 5, the input diffraction grating 310 guides the projection light incident toward the intermediate diffraction grating. In addition, in the case of the projection substrate 100 described in Fig. 6, the input diffraction grating 310 guides the projection light incident toward the output diffraction grating 320.

[0064] The output diffraction grating 320 is disposed at a position in a predetermined direction from the input diffraction grating 310, and receives the projection light guided by the input diffraction grating 310. The output diffraction grating 320 outputs at least a portion of the incident projection light as image light from the display surface. For example, in the case of the projection board 100 described in Fig. 5, the output diffraction grating 320 outputs the projection light incident from the intermediate diffraction grating as image light from the display surface. In addition, in the case of the projection board 100 described in Fig. 6, the output diffraction grating 320 outputs the projection light incident from the input diffraction grating 310 as image light from the display surface.

[0065] 7, the second surface 302 of the projection substrate 100 opposite to the first surface 301 is the display surface. Projection light is incident on the incident diffraction grating 310 from the second surface 302 of the projection substrate 100.

[0066] Filling material 330 fills the grooves of input diffraction grating 310 and output diffraction grating 320. Filling material 330 is a material having a smaller refractive index than input diffraction grating 310 and output diffraction grating 320. Filling material 330 includes, for example, mesoporous silica with a porous structure.

[0067] Mesoporous silica has a porous structure with multiple pores. Furthermore, since mesoporous silica is a spherical material with a diameter of approximately 20 nm, many gaps are formed between the spherical material when it is formed into a film. Since the pores and gaps of such mesoporous silica are filled with air, which has a refractive index of 1, the refractive index of a film formed from mesoporous silica is close to that of air, which is 1. Furthermore, even when mesoporous silica is formed into a film with a thickness similar to that of the grooves of a diffraction grating, there are few areas that block visible light, so the transmittance of visible light and the haze value are also close to those of air.

[0068] The filler material 330 containing such mesoporous silica has, for example, a refractive index of less than 1.2, a visible light transmittance of more than 90%, and a haze value of less than 0.5. Such filler material 330 has properties similar to those of air with respect to visible light. Therefore, even when the grooves of the input diffraction grating 310 and the output diffraction grating 320 are filled with filler material 330, the input diffraction grating 310 and the output diffraction grating 320 can diffract and guide incident light in the same way as when the grooves are not filled with filler material 330.

[0069] As described above, the grooves of the input diffraction grating 310 and the output diffraction grating 320 are filled with the filler material 330, making them less susceptible to damage by impact and less susceptible to the intrusion of foreign matter such as water droplets. The filler material 330 functions to reinforce the input diffraction grating 310 and the output diffraction grating 320, making the projection substrate 100 less susceptible to distortion. Furthermore, because the input diffraction grating 310 and the output diffraction grating 320 do not need to be in contact with an air layer, a vacuum bonding process or the like can be used in the manufacturing process of the projection substrate 100.

[0070] The filler material 330 may fill only the grooves of the input diffraction grating 310 and the output diffraction grating 320, or alternatively, as shown in FIG. 7 , the filler material 330 may be deposited over the entire first surface 301 of the projection substrate 100. In this case, it is desirable that the filler material 330 be deposited to a thickness equal to or greater than a predetermined thickness on the input diffraction grating 310 and the output diffraction grating 320. The predetermined thickness is, for example, about five times the width of the grooves of the input diffraction grating 310 or the output diffraction grating 320. The predetermined thickness is desirably about ten times the width of the grooves of the input diffraction grating 310 or the output diffraction grating 320.

[0071] The incident diffraction grating 310 and the exit diffraction grating 320 are formed on the first surface 301, which is the opposite side to the display surface (second surface 302) of the projection substrate 100. Projection light that passes through the inside of the projection substrate 100 from the second surface 302 is incident on the incident diffraction grating 310. It is desirable that the incident diffraction grating 310 be able to diffract all of the incident projection light, but some of the light may leak from the first surface 301 to the outside of the projection substrate 100. In this embodiment, this leaked light is called leakage light.

[0072] Such leakage light may enter the eyes of a person facing the user and cause discomfort. However, when the filler material 330 is layered to a thickness equal to or greater than a predetermined thickness on the incident diffraction grating 310, the filler material 330 reinforces the incident diffraction grating 310 while dispersing and reducing the leakage light from the incident diffraction grating 310 within the filler material 330.

[0073] Similarly, the output diffraction grating 320 causes at least a portion of the incident projection light to pass through the inside of the projection substrate 100 and exit from the display surface. It is desirable for the output diffraction grating 320 to be able to diffract all of the incident projection light, but some of the light may leak as leakage light from the first surface 301 to the outside of the projection substrate 100. In this case as well, by stacking the filler material 330 to a thickness equal to or greater than a predetermined thickness on the output diffraction grating 320, the filler material 330 can reinforce the output diffraction grating 320 while dispersing and reducing the leakage light from the output diffraction grating 320 inside the filler material 330.

[0074] As described above, by covering the input diffraction grating 310 and the output diffraction grating 320 with the filler material 330, the filler material 330 can reduce leakage light while reinforcing the input diffraction grating 310 and the output diffraction grating 320. The projection substrate 100 can output incident projection light as image light without the input diffraction grating 310 and the output diffraction grating 320 being in contact with an air layer, and can protect the input diffraction grating 310 and the output diffraction grating 320 without a complex configuration. Next, the projection substrate 100, which has the function of protecting the filler material 330, will be described.

[0075] <Second Modification of Projection Board 100> Figure 8 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 in substantially the same manner as those of the projection board 100 according to the present embodiment shown in Figure 7 are designated by the same reference numerals, and redundant explanations will be omitted. The projection board 100 of the second modification further includes a protective film 340 and an adhesive sheet 350.

[0076] 7 , the filler material 330 covers the input diffraction grating 310 and the output diffraction grating 320. The protective film 340 covers and protects the surface of the filler material 330. The protective film 340 is, for example, a triacetyl cellulose (TAC) film. The adhesive sheet 350 is provided between the protective film 340 and the filler material 330 and bonds the protective film 340 to the filler material 330. The adhesive sheet 350 is, for example, a film-like optical adhesive called OCA (Optical Clear Adhesive).

[0077] In the projection substrate 100 of the second modified example described above, the protective film 340 is attached to the filling material 330 with an adhesive sheet 350. The filling material 330 has a weak cohesive force, which may weaken the film strength. In such cases, the protective film 340 can protect the filling material 330.

[0078] Furthermore, since the surface of the first surface 301 of the projection substrate 100 can be strengthened by the protective film 340, an optical member can be further provided on the surface of the protective film 340 opposite the adhesive sheet 350. The projection substrate 100 may further include, for example, an optical lens on the surface of the protective film 340. One example of the optical lens is a prescription lens for correcting the user's eyes. Alternatively or in addition to this, the projection substrate 100 may further include an optical film having an anti-reflection film.

[0079] As described above, the projection substrate 100 of the second modification allows a diffraction grating to be easily formed on the substrate, and also allows optical elements to be easily attached. Therefore, the eyeglass-type terminal 10 using this projection substrate 100 can project image light onto the display surface and also have various other functions. Next, a method for manufacturing this projection substrate 100 will be described.

[0080] <Example of Manufacturing Flow of Projection Substrate 100> Fig. 9 shows an example of a manufacturing flow of the projection substrate 100 according to this embodiment. Fig. 10 shows an example of the configuration of a process for forming the projection substrate 100 according to this embodiment. First, an input diffraction grating 310 and an output diffraction grating 320 are formed on a first surface 301 of a substrate 300 (S11). The input diffraction grating 310 and the output diffraction grating 320 may be formed by a known method, and detailed description thereof will be omitted here.

[0081] 10A shows an example in which an input diffraction grating 310 and an output diffraction grating 320 are formed on a first surface 301 of a substrate 300 according to this embodiment. An intermediate diffraction grating may also be formed on the first surface 301 of the substrate 300. The output diffraction grating 320 may also be a two-dimensional diffraction grating. When multiple diffraction gratings are formed on the same surface, the process for forming the multiple diffraction gratings can be shared, allowing multiple diffraction gratings to be formed efficiently.

[0082] Next, a liquid containing a filler material with a refractive index smaller than that of the substrate 300 is applied to the formed input diffraction grating 310 and output diffraction grating 320 (S12). The liquid contains mesoporous silica as a filler material and a solvent. The solvent is, for example, one liquid or a mixture of multiple liquids selected from the group consisting of ethanol, methyl ethyl ketone, isobutanol, methanol, and water.

[0083] The liquid is formulated so that the solid content of mesoporous silica is 5% or more and 20% or less. The viscosity of the liquid is preferably adjusted to approximately 20 mPa·s. This liquid is applied to the first surface 301 of the substrate 300 using, for example, a spin coater. The spin coater applies the liquid at, for example, approximately 1000 rpm. By using this liquid, the liquid can be filled into the gaps in the grooves of the input diffraction grating 310 and the output diffraction grating 320.

[0084] Next, the applied liquid agent is dried to form filler material 330 that fills the grooves of incident diffraction grating 310 and exit diffraction grating 320 and has a smaller refractive index than incident diffraction grating 310 and exit diffraction grating 320 (S13). Fig. 10(B) shows an example in which filler material 330 is formed on incident diffraction grating 310 and exit diffraction grating 320 formed on substrate 300 according to this embodiment.

[0085] Next, a protective film 340 is attached to the formed filler material 330 using an adhesive sheet 350 (S14). In this manner, the projection substrate 100 can be formed. Fig. 10(C) shows an example in which the projection substrate 100 is formed by attaching the protective film 340 to the substrate 300 according to this embodiment. According to the above operational flow, a diffraction grating for projecting image light onto the display surface of the substrate 300 can be easily formed.

[0086] In the above description of the projection substrate 100 according to the present embodiment, the input diffraction grating 310 and the output diffraction grating 320 are formed on the first surface 301 of the projection substrate 100, but the present invention is not limited to this. For example, at least one of the input diffraction grating 310 and the output diffraction grating 320 may be formed on the second surface 302 of the projection substrate 100.

[0087] 11 shows a third modified example of the projection substrate 100 according to the present embodiment. The projection substrate 100 of the third modified example shows an example in which an output diffraction grating 320 is formed on the second surface 302 of the projection substrate 100. Also, this shows an example in which a filler material 330 is formed so as to cover the first surface 301 and the second surface 302 of the projection substrate 100.

[0088] Alternatively, the exit grating 320 may be formed on the first surface 301 of the projection substrate 100, and the entrance grating 310 may be formed on the second surface 302 of the projection substrate 100. Alternatively, the intermediate grating may be formed on the second surface 302 of the projection substrate 100.

[0089] 12 shows a fourth modified example of the projection substrate 100 according to the present embodiment. The projection substrate 100 of the fourth modified example shows an example in which an input diffraction grating 310 and an output diffraction grating 320 are formed on the second surface 302 of the projection substrate 100. Also shown is an example in which a filler material 330 is formed so as to cover the first surface 301 and the second surface 302 of the projection substrate 100. Although no diffraction grating is formed on the first surface 301 of the projection substrate 100, by laminating the filler material 330, it is possible to reduce leakage light output from the first surface 301 of the projection substrate 100.

[0090] In the above-described third and fourth modified projection substrates 100, examples have been described in which the filler material 330 is formed on the first surface 301 and the second surface 302 of the projection substrate 100. The third and fourth modified projection substrates 100 may further include a protective film 340 and an adhesive sheet 350 for protecting the filler material 330 on the first surface 301 and / or the second surface 302.

[0091] In the projection board 100 according to the present embodiment, an example has been described in which projection light incident on the second surface 302 from the outside is incident on the incident diffraction grating 310. However, the present invention is not limited to this. Alternatively, projection light incident on the first surface 301 from the outside may be incident on the incident diffraction grating 310.

[0092] In the above embodiment, the projection substrate 100 has been described as an example of a substrate on which a diffraction grating is formed so that no air gap is formed on either side of the diffraction grating, but the present invention is not limited to this. When one or more diffraction gratings are formed on a substrate, the diffraction grating can be reinforced by using the filler material 330 according to this embodiment.

[0093] For example, instead of the projection substrate 100, a diffraction substrate on which a single diffraction grating is formed may include the filler material 330. The diffraction substrate is a substrate for diffracting incident light. The diffraction grating receives incident light, diffracts at least a portion of the incident light, and emits the light to the outside of the substrate. Such a diffraction grating may be formed, for example, on a glass substrate or the like using a resist, resin, or the like. In this case, if the diffraction grating is formed so as to be in contact with an air layer, as in the above-mentioned input diffraction grating 310 and output region 230, it may become vulnerable to impacts and the substrate itself may be easily distorted.

[0094] Therefore, by forming a filler material 330 in the grooves of such a diffraction grating, it is possible to make it less likely to break when subjected to an impact and also to reinforce the substrate, making it less likely to distort. Furthermore, by forming the filler material 330 so as to cover the diffraction grating, it is possible to disperse and reduce stray light components generated by the diffraction grating.

[0095] 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.

[0096] REFERENCE SIGNS LIST 10 Glasses-type terminal 20 Input light beam 30 Output light beam bundle 100 Projection substrate 110 Frame 120 Projection section 210 Incident area 212 First groove section 220 Branching area 222 Second groove section 224 First division area 230 Exit area 232 Third groove section 234 Second division area 240 Two-dimensional diffraction grating 300 Substrate 301 First surface 302 Second surface 310 Incident diffraction grating 320 Exit diffraction grating 330 Filling material 340 Protective film 350 Adhesive sheet

Claims

1. A projection substrate for projecting image light onto a display surface, comprising: an input diffraction grating onto which projection light for projecting the image light is incident and which guides at least a portion of the incident projection light in a predetermined direction within the projection substrate; an output diffraction grating which is provided at a position in the predetermined direction from the input diffraction grating, onto which the projection light guided by the input diffraction grating is incident and which emits at least a portion of the incident projection light from the display surface as the image light; and a filler material which is filled in grooves of the input diffraction grating and the output diffraction grating and has a refractive index smaller than that of the input diffraction grating and the output diffraction grating.

2. The projection substrate according to claim 1, wherein the filling material comprises mesoporous silica having a porous structure.

3. The projection substrate according to claim 1, wherein the filler material has a refractive index of less than 1.2, a visible light transmittance of more than 90%, and a haze value of less than 0.

5.

4. The projection board according to claim 1, wherein the incident diffraction grating and the exit diffraction grating are formed on a first surface of the projection board opposite the display surface, the exit diffraction grating causes at least a portion of the incident projection light to pass through the inside of the projection board and exit from the display surface, and the filling material covers the incident diffraction grating and the exit diffraction grating.

5. The projection substrate according to claim 1, wherein the filling material covers the input diffraction grating and the output diffraction grating, and further comprises: a protective film for covering and protecting the surface of the filling material; and an adhesive sheet provided between the protective film and the filling material and for bonding the protective film to the filling material.

6. The projection substrate according to claim 5, wherein the protective film is a triacetyl cellulose film.

7. The projection board according to claim 5, further comprising at least one of an optical lens and an optical film having an anti-reflection film on the surface of the protective film opposite to the adhesive sheet.

8. The projection substrate of claim 1, wherein the input diffraction grating and the output diffraction grating are formed on the display surface of the projection substrate, the filler material covers the input diffraction grating and the output diffraction grating, and the filler material is further formed on a first surface of the projection substrate opposite the display surface.

9. A diffraction substrate for diffracting incident light, comprising: a diffraction grating onto which the incident light is incident and which diffracts at least a portion of the incident light and outputs the light to the outside; and a filler material which fills grooves of the diffraction grating and has a refractive index smaller than that of the diffraction grating.

10. A glasses-type terminal worn by a user, comprising: a projection substrate according to any one of claims 1 to 8, 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, and which projects the image light onto the display surface with a surface facing the user's eye as the display surface; a frame that fixes the projection substrate; and a projection unit that is provided on the frame and irradiates the projection light onto the incident diffraction grating of the projection substrate to project the image light onto the display surface.

11. A method for manufacturing a projection substrate for projecting image light onto a display surface, comprising the steps of: forming an incident diffraction grating and an exit diffraction grating on a first surface of a substrate; and applying a liquid agent containing a filler material having a smaller refractive index than the incident diffraction grating and the exit diffraction grating to the formed incident diffraction grating and the exit diffraction grating, wherein projection light for projecting the image light is incident on the incident diffraction grating, and the exit diffraction grating is provided at a position in the predetermined direction from the incident diffraction grating, and the projection light guided by the incident diffraction grating is incident on the exit diffraction grating, and at least a portion of the incident projection light is output from the display surface as the image light, and the liquid agent contains mesoporous silica and a solvent as the filler material, and the solid content of the mesoporous silica is 5% or more and 20% or less.

Images