Projection board and eyeglass-type terminal

Abstract

This projection substrate is for causing at least a portion of incident light from a first surface to be transmitted through a second surface on the opposite side to the first surface and causing image light to be projected onto the second surface, the projection substrate comprising: an incidence region to which projection light is incident; a branching region that has a first diffraction grating that guides the incident projection light from the incidence region; and an emission region that has a second diffraction grating that emits a portion of the projection light from the second surface after a portion of the incident projection light from the branching region has been guided. In the projection substrate: the incidence region guides the projection light to the branching region; the branching region diffracts a portion of the projection light toward the emission region; the first diffraction grating has a plurality of first irregular sections made up of first projection sections and first recess sections formed in a repeating manner in a first direction in which the projection light is guided; and a first fill factor, which is the ratio of the width in the first direction of the first projection sections to a first cycle of the first irregular sections in one first division region among a plurality of first division regions, is separated by 0.5 from a first fill factor of a first division region closer to the incidence region than the one first division region.

Description

Technical Field

[0001] The present invention relates to a projection substrate and a glasses-type terminal.

Background Art

[0002] Conventionally, glasses-type devices such as head-mounted displays that display a two-dimensional image for a user to observe using an optical system including a waveguide or the like are known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a device, since the optical system is incorporated in a limited space, the optical system may become complicated. In addition, when a simple optical system is used, variations in the luminance of the image projected onto the display area may occur.

[0005] Therefore, the present invention has been made in view of these points, and an object thereof is to reduce variations in the luminance of a projection image to be observed by a user with a simple configuration.

Means for Solving the Problems

[0006] In a first embodiment of the present invention, a projection substrate for projecting image light onto a second surface while transmitting at least a portion of light incident from a first surface to a second surface opposite the first surface, comprising: an incident region into which projection light for projecting the image light is incident; a branching region having a first diffraction grating for guiding the projection light incident from the incident region; and an exiting region having a second diffraction grating for guiding a portion of the projection light incident from the branching region and then emitting a portion of the projection light from the second surface, wherein the incident region guides the incident projection light to the branching region, and the branching region The present invention provides a projection substrate in which a portion of the projected light is diffracted toward the emission region, the first diffraction grating has a plurality of first uneven portions composed of first convex portions and first concave portions formed to repeat in a first direction that guides the projected light, the branching region has a plurality of first divided regions, the first fill factor which is the ratio of the width of the first convex portion in the first direction to the first period of the first uneven portion of one first divided region is within a range that does not include a predetermined value, and the first fill factor of a first divided region closer to the incidence region than one first divided region is within a range that includes the predetermined value.

[0007] The first period of the first uneven portion of each of the plurality of first divided regions may be the same.

[0008] The depth of the first uneven portion of the first divided region is greater than the depth of the first uneven portion of the first divided region that is closer to the incident region than the first divided region, and the absolute value of the difference between the first fill factor of the first divided region and the first fill factor of the first divided region that is closer to the incident region than the first divided region may be smaller as the absolute value of the difference between the depth of the first uneven portion of the first divided region and the depth of the first uneven portion of the first divided region that is closer to the incident region than the first divided region increases.

[0009] The predetermined value is 0.5, the first fill factor of the first divided region furthest from the incident region among the plurality of first divided regions is within the range of 0.35 or less or 0.65 or more, and the first fill factor of the first divided region closer to the incident region than the first divided region may be within the range of 0.3 or more and 0.7 or less.

[0010] The second diffraction grating has a plurality of second uneven portions, each composed of a second convex portion and a second concave portion formed to repeat in a second direction that guides the projected light, and the emission region has a plurality of second divided regions, and the second fill factor, which is the ratio of the width of the second convex portion in the second direction to the second period of the second uneven portion of the second divided region of the plurality of second divided regions that is closer to the branching region than one of the second divided regions, may be within a range that includes the predetermined value.

[0011] The second period of the second uneven portion of each of the plurality of second divided regions may be the same.

[0012] The depth of the second uneven portion in the first second division region is greater than the depth of the second uneven portion in the second division region that is closer to the branch region than the first second division region. The absolute value of the difference between the second fill factor, which is the ratio of the width of the second protrusion in the second direction to the second period of the second uneven portion in the first second division region, and the second fill factor of the second division region that is closer to the branch region than the first second division region, may be smaller as the absolute value of the difference between the depth of the second uneven portion in the first second division region and the depth of the second uneven portion in the second division region that is closer to the branch region than the first second division region increases.

[0013] The predetermined value is 0.5, the second fill factor of the first second division region is within a range that does not include the predetermined value, and the second fill factor of the second division region that is closer to the branch region than the first second division region may be within a range that includes the predetermined value.

[0014] The predetermined value is 0.5, the first period of each of the plurality of first divided regions is 50 nm or more and 1 μm or less, the depth of the first uneven portion of one of the first divided regions is 50 nm or more and 800 nm or less, the first fill factor of one of the first divided regions is 0.35 or less or 0.65 or more, the depth of the first uneven portion of a first divided region closer to the incident region than one of the first divided regions is 5 nm or more and 100 nm or less, and the first fill factor of a first divided region closer to the incident region than one of the first divided regions is 0.3 or more and 0.7 or less. The second period of each of the plurality of second division regions is preferably 100 nm or more and 1 μm or less, the depth of the second uneven portion of one second division region is preferably 50 nm or more and 800 nm or less, the second fill factor of one second division region is preferably 0.35 or less or 0.65 or more, the depth of the second uneven portion of a second division region closer to the branch region than one second division region is preferably 5 nm or more and 100 nm or less, and the second fill factor of a second division region closer to the branch region than one second division region may be 0.3 or more and 0.7 or less.

[0015] In a second embodiment of the present invention, there is a glasses-type terminal worn by a user, comprising: a projection substrate as described in claim 1 or 2, which is provided as at least one of the lenses for the user's right eye and left eye, and which transmits at least a portion of the light incident from the first surface to the user's eye while projecting the image light onto the second surface; a frame for fixing the projection substrate; and a projection unit provided on the frame, which irradiates the incident area of ​​the projection substrate with the projection light for projecting the image light onto the emission area. [Effects of the Invention]

[0016] According to the present invention, it is possible to reduce variations in the brightness of the projected image light observed by the user with a simple configuration. [Brief explanation of the drawing]

[0017] [Figure 1]An example of the configuration of the glasses-type terminal 10 according to the present embodiment is shown. [Figure 2] An outline of the optical path of the projection light in the glasses-type terminal 10 according to the present embodiment is shown. [Figure 3] An outline of the optical path of the projection light in the projection substrate 100 according to the present embodiment is shown. [Figure 4] An example of the projection light irradiated by the projection unit 120 of the present embodiment onto the projection substrate 100 and the image light emitted from the projection substrate 100 is shown. [Figure 5] An example of the configuration of the projection substrate 100 according to the present embodiment is shown. [Figure 6] It is a diagram for explaining the first factor. [Figure 7] It is a diagram showing the result of simulation of the luminance of the image formed on the pupil. [Figure 8] A modified example of the glasses-type terminal 10 according to the present embodiment is shown.

Embodiments for Carrying Out the Invention

[0018] <Configuration Example of Glasses-Type Terminal 10> FIG. 1 shows an example of the configuration of the glasses-type terminal 10 according to the present embodiment. In the present embodiment, three axes orthogonal to each other are defined as the X-axis, Y-axis, and Z-axis. The glasses-type terminal 10 is, for example, a wearable device worn by a user. The glasses-type terminal 10 projects image light onto a display area provided on the projection substrate 100 while allowing the user to observe the scenery through the glasses. The glasses-type terminal 10 includes a projection substrate 100, a frame 110, and a projection unit 120.

[0019] The projection substrate 100 projects the image light onto the second surface while transmitting at least a part of the light incident from the first surface to the user's eyes. Here, the first surface of the projection substrate 100 is the surface facing away from the user when the user wears the glasses-type terminal 10. Also, the second surface of the projection substrate 100 is the surface facing the user when the user wears the glasses-type terminal 10. FIG. 1 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, for example, a substrate on which a diffraction grating functioning as a waveguide is formed on a glass substrate. The projection substrate 100 will be described later.

[0020] The frame 110 fixes the projection substrate 100. At least one of the lenses for the user's right eye and the lens for the left eye is provided with the projection substrate 100 on the frame 110. FIG. 1 shows an example in which the projection substrate 100a is provided as the lens for the user's right eye on the frame 110, and the projection substrate 100b is provided as the lens for the left eye.

[0021] Alternatively, the frame 110 may be provided with one projection substrate 100 as the lens for the user's right eye or the lens for the left eye. Also, the frame 110 may be provided with one projection substrate 100 as the lenses for both eyes of the user. In this case, the frame 110 may have the shape of goggles. The frame 110 has parts such as temples and straps so that the user can wear the glasses-type terminal 10.

[0022] The projection unit 120 is provided on the frame 110 and irradiates the projection substrate 100 with projection light for projecting the 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 the projection unit 120a for irradiating the projection substrate 100a with the projection light L1 and the projection unit 120b for irradiating the projection substrate 100b with the projection light L2 are provided on the frame 110.

[0023] The projection unit 120 may be provided on the part of the frame 110 that fixes the projection substrate 100, or it may be provided on the temple or the like of the frame 110. Preferably, the projection unit 120 is provided so as to be integrated with the frame 110. The projection unit 120 may, for example, irradiate the projection substrate 100 with projection light containing one wavelength, causing the user to observe a monochrome image. Alternatively, the projection unit 120 may irradiate the projection substrate 100 with projection light containing multiple wavelengths, causing the user to observe an image containing multiple colors.

[0024] Figure 2 shows a schematic diagram of the optical path of the projected light in the spectacle-type terminal 10 according to this embodiment. The projection unit 120 irradiates the projection light onto an incident region 210 provided on the projection substrate 100. The incident region 210 guides the projection light into the substrate of the projection substrate 100. The projection substrate 100 then emits the projected light, which has been guided within the substrate, as image light from the emission region 230. The incident region 210 and the emission region 230 will be described later.

[0025] Figure 3 shows a schematic diagram of the optical path of the projection light in the projection substrate 100 according to this embodiment. As will be described later, the projection substrate 100 has an incident region 210, a branching region 220, and an exit region 230. The projection light L is incident in the incident region 210, passes through the branching region 220, and exits as image light P from the exit region 230. The branching region 220 guides parts of the projection light L to the exit region 230 as the projection light L moves away from the incident region 210.

[0026] Similarly, the emission region 230 also emits portions of the projected light L as they travel away from the branching region 220, as part of the image light P. As a result, the projection substrate 100 emits the projected light L that was incident on the incident region 210 from the emission region 230 as image light P.

[0027] Here, consider an example where the branching region 220 guides the projected light L to the output region 230 at a constant rate throughout the entire region of the branching region 220. In this case, as the projected light L travels away from the incident region 210, the amount of light L decreases, so the intensity of the projected light L incident on the output region 230 from the branching region 220 may differ depending on the distance from the incident region 210.

[0028] Similarly, consider an example where the emission region 230 emits projection light L as image light P at a constant rate throughout its entire region. In this case, as the projection light L moves away from the branching region 220, the amount of projection light L decreases, so the intensity of the image light P emitted from the emission region 230 may vary depending on the distance from the incident region 210 and the distance from the emission region 230. For example, the brightness of the image projected by the emission region 230 may gradually decrease from the upper left pixel to the lower right pixel. The projection substrate 100 according to this embodiment reduces such variations in brightness.

[0029] <An example of projected light and image light> Figure 4 shows an example of projection light L irradiated onto the projection substrate 100 by the projection unit 120 according to this embodiment, and image light P emitted by the projection substrate 100. The projection unit 120 irradiates projection light L toward, for example, the second surface of the projection substrate 100 located in the +Z direction. The projection light L corresponds to the image shown to the user. For example, if a screen or the like is installed on a surface substantially parallel to the XY plane and projection light L is projected onto it, an image M1 for the user to observe is displayed on the screen. The image shown to the user is, for example, an AR (Augmented Reality) image or a VR (Virtual Reality) image created by a processor in the projection unit 120. In this way, the projection unit 120 irradiates a plurality of light rays as projection light L that form an image M1 on a surface substantially parallel to the XY plane.

[0030] In this embodiment, an example is 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. In Figure 4, five of the multiple light rays emitted by the projection unit 120 are shown as input rays 20. For example, the light ray corresponding to the upper left pixel of the image is the first input ray 20a, the light ray corresponding to the lower left pixel of the image is the second input ray 20b, the light ray corresponding to the center pixel of the image is the third input ray 20c, the light ray corresponding to the upper right pixel of the image is the fourth input ray 20d, and the light ray corresponding to the lower right pixel of the image is the fifth input ray 20e.

[0031] The projection unit 120, for example, irradiates the incident region 210 of the projection substrate 100 with such projection light L to create an upright virtual image at infinity or a predetermined position. The projection light incident on the incident 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 incident on the user's eye, which is located at a distance d from the projection substrate 100. The image light P then forms an image M2 on the retina of the user's eye. Thus, the image light P includes multiple beams of light that form an image M2.

[0032] In Figure 4, five of the multiple ray beams irradiated from the circular region C of the emission region 230 of the projection substrate 100 and imaged at predetermined positions are shown as output ray beams 30. For example, the ray beam that images as the lower right pixel of the image is the first output ray beam 30a, the ray beam that images as the upper right pixel of the image is the second output ray beam 30b, the ray beam that images as the center pixel of the image is the third output ray beam 30c, the ray beam that images as the lower left pixel of the image is the fourth output ray beam 30d, and the ray beam that images as the upper left pixel of the image is the fifth output ray beam 30e.

[0033] Each ray beam corresponds to one of the multiple input rays 20 incident from the projection unit 120. For example, the first output ray beam 30a corresponds to the first input ray 20a and includes multiple rays generated by the first input ray 20a through multiple branching and multiple diffractions between the incident region 210 and the exit region 230 of the projection substrate 100. Similarly, the second output ray beam 30b corresponds to the second input ray 20b, the third output ray beam 30c corresponds to the third input ray 20c, the fourth output ray beam 30d corresponds to the fourth input ray 20d, and the fifth output ray beam 30e corresponds to the fifth input ray 20e.

[0034] In other words, the image M2 formed on the retina of the user's eye by the image light P emitted from the emission area 230 corresponds to the image M1 projected by the projection light L irradiated by the projection unit 120. As a result, the user wearing the glasses-type terminal 10 can perceive that the image M2 is projected onto the second surface of the projection substrate 100, superimposed on the scenery viewed through the projection substrate 100. In other words, the emission area 230 functions as a display area that displays the image M2 corresponding to the image M1 projected by the projection light L.

[0035] In Figure 4, an example is shown where the image M2 observed by the user is an image that is vertically and horizontally inverted from 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 it may be a moving image. The projection substrate 100 that emits the image light P corresponding to the incident projection light L will be described next.

[0036] <Example configuration of projection substrate 100> Figure 5 shows an example of the configuration of the projection substrate 100 according to this embodiment. Figure 3 shows an example in which the first and second surfaces of the projection substrate 100 are arranged substantially parallel to the XY plane. The projection substrate 100 is a substrate for projecting image light onto the second surface while transmitting at least a portion of the light incident from the first surface to the second surface on the opposite side of the first surface. The projection substrate 100 is, as an example, a glass substrate. The projection substrate 100 comprises an incident region 210, a branching region 220, and an output region 230.

[0037] <Example of incidence region 210> The incident region 210 receives projection light for projecting image light and guides the incident projection light toward the branching region 220. Figure 5 shows an example where the incident region 210 has a circular shape in a plane substantially parallel to the XY plane, but it is not limited to this. The incident region 210 only needs to be able to guide the projection light toward the branching region 220, and may have shapes such as an ellipse, polygon, or trapezoid.

[0038] The incident region 210 has a diffraction grating in which a plurality of first grooves 212 are formed in an IPE (Input Pupil Expander) period. In other words, the plurality of first grooves 212 function as a diffraction grating by being arranged in the same direction on the upper surface of the projection substrate 100 with predetermined groove widths and spacings. The incident region 210 has a reflective or transmissive diffraction grating and guides the projected light in the direction of the branching region 220 by reflective or transmissive diffraction.

[0039] The IPE period of the multiple first grooves 212 is, for example, in the range of about 10 nm to about 10 μm. The IPE period is preferably in the range of about 100 nm to about 1 μm. The IPE period is more preferably in the range of about 200 nm to about 800 nm. The depth of the multiple first grooves 212 is in the range of about 1 nm to about 10 μm. The depth of the multiple first grooves 212 is preferably in the range of about 50 nm to about 800 nm.

[0040] The fill factor of the multiple first grooves 212 is in the range of approximately 0.05 to 0.95. Preferably, the fill factor of the multiple first grooves 212 is in the range of approximately 0.3 to 0.7. Here, the fill factor is the value obtained by dividing the distance between two adjacent first grooves 212 by the IPE period. Note that the distance between two adjacent first grooves 212 is sometimes called the line, the width of the first grooves 212 is called the space, and the IPE period is called the pitch. In this case, the pitch is the sum of the line and the space, and the fill factor is the value obtained by dividing the line by the pitch.

[0041] Multiple first grooves 212 are arranged, for example, in a direction from the incident region 210 toward the branching region 220. Here, the direction of propagation of projected light from the incident region 210 toward the branching region 220 is referred to as the first direction. Figure 5 shows an example in which the first direction is approximately parallel to the X-axis direction, and the first grooves 212 extending in a direction approximately parallel to the Y-axis direction are arranged in the first direction. As the projected light enters the incident region 210 while converging, the incident region 210 guides the projected light toward the branching region 220 such that it has a spreading angle centered on the first direction within the plane of the projection substrate 100.

[0042] <Example of branching region 220> The branching region 220 guides a portion of the projected light incident from the incident region 210 toward the exit region 230. The branching region 220 is located in a plane substantially parallel to the XY plane, in the region through which the projected light passes. The branching region 220 has a reflective diffraction grating and guides the projected light toward the exit region 230 by reflective diffraction. The branching region 220 has, for example, a rectangular shape with the first direction as the longitudinal direction.

[0043] Furthermore, since the projected light propagates while spreading out from the first direction, it is preferable that the branching region 220 has a shape that spreads out away from the first direction, which is the direction of propagation of the projected light, as it moves away from the incident region 210. The branching region 220 may have a shape such as a trapezoid or a sector in 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 in a region in which the projected light propagates while spreading out in the XY plane, and the projected light can be efficiently guided.

[0044] The branching region 220 has a plurality of first uneven portions formed by first convex portions and first concave portions that are repeated in a first direction. Hereinafter, the first uneven portions will be referred to as second groove portions 222. That is, the branching region 220 has a first diffraction grating in which a plurality of second groove portions 222 are formed in a first 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 spacings, and thus function as a diffraction grating. The branching region 220 functions, for example, as a reflective diffraction grating, guiding the projected light to the emission region 230.

[0045] The first period of the multiple second grooves 222 is different from the IPE period of the multiple first grooves 212. It is desirable that the first period be selected to be appropriate for guiding the projected light to the emission region 230. The first period is, for example, in the range of about 10 nm to about 10 μm. Preferably, the first period is in the range of about 50 nm to about 1 μm. More preferably, the first period is in the range of about 100 nm to about 700 nm. The depth of the multiple second grooves 222 is in the range of about 1 nm to about 10 μm. Preferably, the depth of the multiple second grooves 222 is in the range of about 5 nm to about 800 nm.

[0046] The multiple second grooves 222 are arranged in a predetermined direction, for example. For example, the direction from the branching region 220 toward the ejection region 230 is defined as the second direction, and the angle between the first direction and the second direction is defined as the first angle. In this case, the multiple second grooves 222 are formed in a direction that is inclined toward the second direction by an angle of half the first angle with respect to the first direction. Figure 5 shows an example where the second direction is approximately parallel to the Y-axis direction, the first angle is approximately 90 degrees, and the multiple second grooves 222 are arranged in a direction that is inclined toward the second direction by approximately 45 degrees with respect to the first direction.

[0047] The branching region 220 has a plurality of first division regions 224 arranged in the direction of propagation of the incident projected light. The second grooves 222 formed in the plurality of first division regions 224 each have different depths. In other words, the second grooves 222 are formed in the branching region 220 such that the proportion of the input projected light guided to the output region 230 differs for each first division region 224.

[0048] The branching region 220 preferably has three or more first division regions 224. The first period of each of the multiple second grooves 222 formed in each of the multiple first division regions 224 is, for example, all the same. In this way, the branching region 220 is divided into multiple first division regions 224, and the amount of projected light guided to the output region 230 is made different for each first division region 224, thereby guiding projected light with varying intensity depending on the distance from the incident region 210 to the output region 230, while adjusting the distribution of light intensity in the direction perpendicular to the propagation direction of the projected light to be approximately constant.

[0049] For example, the second groove 222 is formed such that the depth of the second groove 222 provided in one first divided region 224 is greater than the depth of the second groove 222 provided in a first divided region 224 that is closer to the incident region 210 than the first divided region 224. In this case, the rate of change in the depth of the second groove 222 in two adjacent first divided regions 224 among the multiple first divided regions 224 may be larger the further away from the incident region 210.

[0050] As an example, consider a branched region 220 having three first division regions 224, as shown in Figure 5. Here, the first division region 224a closest to the incident region 210 has a second groove 222 formed therein so as to guide approximately 1 / 4 of the incident projected light to the exit region 230. In this case, approximately 3 / 4 of the remaining projected light incident on the first division region 224a closest to the incident region 210 is incident on the adjacent first division region 224b.

[0051] Assume that the first divided region 224b, which is the second closest to the incident region 210, has a second groove 222 with a depth such that it guides light with approximately 1 / 3 the intensity of the incident projected light to the exit region 230. In other words, the depth of the second groove 222 in the first divided region 224b, which is the second closest to the incident region 210, is greater than the depth of the second groove 222 in the first divided region 224a, which is 4 / 3 the intensity of the light compared to the first divided region 224a, which is closest to the incident region 210, to the exit region 230. Such a first divided region 224b will guide light with approximately 1 / 4 the intensity of the projected light incident on the first divided region 224a, which is closest to the incident region 210, to the exit region 230.

[0052] Then, approximately half of the remaining light intensity of the projected light incident on the first divided region 224a, which is closest to the incident region 210, is incident on the adjacent first divided region 224c. The first divided region 224c, which is the third closest to the incident region 210, is formed with a second groove 222 depth such that it guides approximately half of the light intensity of the incident projected light to the exit region 230. In other words, the depth of the second groove 222 in the first divided region 224c, which is the third closest to the incident region 210, is formed to guide 3 / 2 times the light intensity of the first divided region 224b, which is the second closest to the incident region 210, to the exit region 230.

[0053] Furthermore, the rate of change in the depth of the second groove 222 of two adjacent first division regions 224 among the three first division regions 224 is formed to increase as it moves away from the incident region 210. The first division region 224c, which is the third closest to the incident region 210, guides light with approximately 1 / 4 the amount of light of the projected light incident on the first division region 224a, which is closest to the incident region 210, to the exit region 230. As shown in the above example, the branching region 220 can guide projected light to the exit region 230 while maintaining a nearly constant distribution of the amount of projected light guided to the exit region 230 corresponding to each first division region 224 by making the amount of projected light guided to the exit region 230 different for each first division region 224 and setting it to a predetermined value.

[0054] The branching region 220 may further have a first reflection region 226, which is one of the first division regions 224, at the position furthest from the incident region 210. Figure 5 shows an example in which the branching region 220 has three first division regions 224 and a first reflection region 226. The first reflection region 226 reflects at least a portion of the light that has passed through the multiple first division regions 224 back to the multiple first division regions 224. The first reflection region 226 has a second groove 222 that is deeper than the depth of the second groove 222 of the adjacent first division region 224.

[0055] For example, it is desirable that the depth of the second groove 222 of the first reflection region 226 be approximately three times or more the depth of the largest second groove 222 among the multiple first division regions 224. More preferably, the depth of the second groove 222 of the first reflection region 226 be approximately ten times or more the depth of the largest second groove 222 among the multiple first division regions 224. The second grooves 222 of the first reflection region 226 may be arranged in a first direction.

[0056] Because the branching region 220 has such a first reflection region 226, the multiple first division regions 224 guide at least a portion of the light reflected by the first reflection region 226 to the output region 230. As a result, the branching region 220 can guide more projected light to the output region 230. The depth of the second groove 222 of the multiple first division regions 224 may be determined so that the amount of projected light guided by each first division region 224 to the output region 230, including the light reflected by the first reflection region 226, is approximately constant.

[0057] The widths of the protrusions and recesses of each of the multiple first divided regions 224 are formed such that the first fill factor is a predetermined value. The first fill factor is the ratio of the width of the first protrusion in the first direction to the first period of the second groove 222 of one of the first divided regions 224.

[0058] Figure 6 is a diagram illustrating the first fill factor. Multiple second grooves 222 are formed on the glass substrate 112. Line 240 is the width of the first protrusion 222a of the second groove 222. Space 242 is the width of the first recess 222b of the second groove 222. Pitch 244 is the sum of line 240 and space 242, and is the length of the first period. The first fill factor is the value obtained by dividing line 240 by pitch 244. The length 248 from the first recess 222b to the glass substrate 112 is in the range of 10 nm to 500 nm. Preferably, the length 248 is in the range of 30 nm to 200 nm. Depth 246 is the depth of the second groove 222.

[0059] The first fill factor of the first reflection region 226, which is one of the first divided regions 224, is within a range that does not include a predetermined value. The predetermined value is, for example, 0.5. Specifically, the first fill factor of the first reflection region 226 is within a range of 0.35 or less, or 0.65 or more, excluding the predetermined value of 0.5. The first fill factor of the first divided region 224 that is closer to the incident region 210 than the first reflection region 226 is within a range that includes the predetermined value of 0.5. Specifically, the first fill factors of the first divided region 224a, the first divided region 224b, and the first divided region 224c are within a range of 0.3 or more and 0.7 or less.

[0060] The difference between the first fill factor of the first reflection region 226 and the first fill factor of the first divided region 224c, which is closer to the incident region 210 than the first reflection region 226, is smaller as the absolute value of the difference between the depth of the second groove 222 of the first reflection region 226 and the depth of the second groove 222 of the first divided region 224c increases. For example, if the difference between the depth of the second groove 222 of the first reflection region 226 and the depth of the second groove 222 of the first divided region 224c is 180 nm, then the difference between the first fill factor of the first reflection region 226 and the first fill factor of the first divided region 224c, which is closer to the incident region 210 than the first reflection region 226, is 0.35. On the other hand, if the difference between the depth of the second groove 222 in the first reflection region 226 and the depth of the second groove 222 in the first divided region 224c is 680 nm, then the difference between the first fill factor of the first reflection region 226 and the first fill factor of the first divided region 224c, which is closer to the incident region 210 than the first reflection region 226, is 0.30.

[0061] <Example of an ejection region 230> The emission region 230 guides at least a portion of the projected light incident from the branching region 220 and emits it as image light from the second surface of the projection substrate 100. Figure 5 shows an example in which the emission region 230 has a rectangular shape with the X-axis direction as its longitudinal direction in a plane substantially parallel to the XY plane, but it is not limited to this. The emission region 230 only needs to be able to guide the projected light and emit it as image light, and may have shapes such as a rectangle, square, or trapezoid with the Y-axis direction as its longitudinal direction.

[0062] The emission region 230 has a plurality of third grooves 232, which are a plurality of second convex and concave portions formed to repeat in a second direction. In other words, the emission region 230 has a second diffraction grating in which the plurality of third grooves 232 are formed in a second period. To put it another way, the plurality of third grooves 232 are arranged in the same direction on the upper surface of the projection substrate 100 with predetermined groove widths and spacings, thereby functioning as a diffraction grating. The emission region 230 has a reflective or transmissive diffraction grating, and directs image light toward the user's eye by reflective or transmissive diffraction.

[0063] The second period of the multiple third grooves 232 provided in the emission region 230 is different from the first period of the multiple second grooves 222 in the branch region 220. The second period of the multiple third grooves 232 in the emission region 230 may also be the same as the IPE period of the multiple first grooves 212 in the incidence region 210. By matching the periods of the diffraction gratings provided in the incidence region 210 into which the projection light is incident and the emission region 230 into which the image light is emitted, distortions and other issues that occur in the image observed by the user can be reduced.

[0064] The second period is formed in a range of approximately 10 nm to 10 μm. Preferably, the second period is formed in a range of approximately 100 nm to 1 μm. More preferably, the second period is formed in a range of approximately 200 nm to 800 nm. The depth of the multiple third grooves 232 is formed in a range of approximately 1 nm to 10 μm. Preferably, the depth of the multiple third grooves 232 is formed in a range of approximately 5 nm to 800 nm.

[0065] Multiple third grooves 232 are arranged, for example, in a second direction from the branching region 220 to the ejection region 230. Figure 5 shows an example in which third grooves 232 extending in the first direction are arranged in the second direction.

[0066] The emission region 230, like the branching region 220, has a plurality of second division regions 234 arranged in the direction of propagation of the projected light incident from the branching region 220. The third grooves 232 formed in the plurality of second division regions 234 each have different depths. In other words, the third grooves 232 are formed in the emission region 230 such that the proportion of the input projected light emitted as image light differs for each second division region 234.

[0067] It is desirable that the ejection region 230 has two or more second division regions 234. For example, the depth of the third groove 232 provided in one second division region 234 is greater than the depth of the third groove 232 provided in a second division region 234 that is closer to the branch region 220 than the first second division region 234. Also, if the ejection region 230 has three or more second division regions 234, the rate of change in the depth of the third groove 232 in two adjacent second division regions 234 may increase as it moves further away from the branch region 220. Note that each of the second periods of the multiple third grooves 232 is, for example, all the same.

[0068] As described above, the emission region 230 is divided into multiple second division regions 234, and the amount of light emitted as image light is made different for each second division region 234. In this way, the emission region 230, like the multiple first division regions 224 of the branching region 220, guides the projected light as image light, and when an observer observes the image light as an image, the distribution of light intensity of the entire image can be adjusted to be approximately constant.

[0069] The emission region 230 may further have a second reflection region 236, which is one of the second division regions 224, at the position furthest from the branching region 220. Figure 5 shows an example in which the emission region 230 has two second division regions 234 and a second reflection region 236. The second reflection region 236 reflects at least a portion of the light that has passed through the multiple second division regions 234 back to the multiple second division regions 234. The second reflection region 236 has a third groove 232 that is deeper than the depth of the third groove 232 of the adjacent second division region 234.

[0070] For example, it is desirable that the depth of the third groove 232 of the second reflection region 236 be approximately three times or more the depth of the largest third groove 232 among the multiple second division regions 234. More preferably, the depth of the third groove 232 of the second reflection region 236 is approximately ten times or more the depth of the largest third groove 232 among the multiple second division regions 234.

[0071] Because the emission region 230 has such a second reflection region 236, the multiple second division regions 234 emit at least a portion of the light reflected by the second reflection region 236 as image light from the second surface of the projection substrate 100. As a result, the emission region 230, like the branching region 220, can emit more projected light as image light. The depth of the third groove 232 of the multiple second division regions 234 may be determined so that the amount of light emitted as image light by each second division region 234, including the light reflected by the second reflection region 236, is approximately constant.

[0072] The widths of the protrusions and recesses of each of the multiple second division regions 234 are formed such that the second fill factor is a predetermined value. The second fill factor is the ratio of the width of the second protrusion in the second direction to the second period of the third groove 232.

[0073] The second fill factors of the second division region 234a, the second division region 234b, and the second division region 234c are within a range that includes a predetermined value. The predetermined value is, for example, 0.5. Specifically, the second fill factors of the second division region 234a, the second division region 234b, and the second division region 234c are within a range of 0.3 to 0.7, including the predetermined value of 0.5.

[0074] The second fill factor of the second reflection region 236 is within a range that does not include the predetermined value of 0.5. For example, the second fill factor of the second reflection region 236 is 0.35 or less or 0.65 or more, but is not limited to these values.

[0075] Furthermore, the absolute value of the difference between the second fill factor of the second reflection region 236 and the second fill factor of the second division region 234 is smaller as the absolute value of the difference between the depth of the third groove 232 of the second reflection region 236 and the depth of the third groove 232 of the second division region 234 increases. For example, if the difference between the depth of the third groove 232 of the second reflection region 236 and the depth of the third groove 232 of the second division region 234 is 70 nm, then the difference between the second fill factor of the second reflection region 236 and the second fill factor of the second division region 234, which is closer to the branch region 220 than the second reflection region 236, is 0.1. On the other hand, if the difference between the depth of the third groove 232 in the second reflection region 236 and the depth of the third groove 232 in the second division region 234 is 470 nm, then the difference between the second fill factor of the second reflection region 236 and the second fill factor of the second division region 234, which is closer to the branch region 220 than the second reflection region 236, is 0.00.

[0076] Figure 7 shows the results of a simulation of the brightness of an image formed by the pupil. The vertical and horizontal axes in Figure 7 indicate the pixel positions. Figure 7 shows the results of a simulation of the brightness of an image under multiple conditions with different first fill factors in the first reflection region 226.

[0077] We will now explain the conditions for the first reflection region 226 other than the first fill factor. The depth of the first groove 212 in the incident region 210 is between 100 nm and 200 nm. The length of the IPE period is between 350 nm and 450 nm.

[0078] The depth of the second groove 222 in the first divided regions 224a, 224b, and 224c is 5 nm or more and 100 nm or less. The first period of the first divided regions 224a, 224b, and 224c is 200 nm or more and 300 nm or less. The depth of the second groove 222 in the first reflection region 226 is 100 nm or more and 700 nm or less. The first period of the second groove 222 in the first reflection region 226 is 200 nm or more and 300 nm or less.

[0079] The depth of the third groove 232 in the second divided region 234 is between 5 nm and 100 nm. The first period of the third groove 232 in the second divided region 234 is between 350 nm and 450 nm.

[0080] The depth of the third groove 232 in the second reflection region 236 is between 100 nm and 700 nm. The first period of the third groove 232 in the second reflection region 236 is between 350 nm and 450 nm. The thickness of the glass substrate 112 is 0.4 mm. The length 248 from the first recess 222b to the glass substrate 112 is 100 nm.

[0081] Figure 7(a) shows the simulation results when the first fill factor of the first reflection region 226 is 0.4. Figure 7(b) shows the simulation results when the first fill factor of the first reflection region 226 is 0.5. Figure 7(c) shows the simulation results when the first fill factor of the first reflection region 226 is 0.6. Figure 7(d) shows the simulation results when the first fill factor of the first reflection region 226 is 0.85.

[0082] The dark areas in Figure 7 indicate low brightness. As shown in Figure 7, the further the first fill factor of the first reflection region 226 deviates from 0.5, the less variation there is in the overall brightness of the image, and the more constant the brightness becomes. In this way, brightness unevenness can be reduced by forming the second groove 222 and the third groove 232 so that the fill factors of the diffraction gratings in the branching region 220 and the emission region 230 are appropriate values.

[0083] As described above, the projection substrate 100 according to this embodiment branches the projection light incident on the incident region 210 into multiple first division regions 224 of the branching region 220 at different rates, and emits it as image light from the emission 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 image brightness by emitting image light at different rates for multiple second division regions 234 in the emission region 230.

[0084] Such a projection substrate 100 can be realized by forming diffraction gratings corresponding to an incident region 210, a branching region 220, and an exit region 230 on a first or second surface of a glass substrate or the like. The grooves in which the diffraction gratings are formed are, for example, resist, resin, etc. Therefore, the projection substrate 100 according to this embodiment is a substrate that can be easily produced by forming grooves of predetermined period and depth in each region without incorporating a complex optical system.

[0085] <Other examples of eyeglass-type terminals 10> An example of a spectacle-type terminal 10 has already been described in which the projection substrate 100 is provided on the frame 110 and the projection unit 120 irradiates the incident area 210 of the projection substrate 100 with projection light, but the invention is not limited to this example. For example, multiple projection substrates 100 may be fixed to the frame 110 of the spectacle-type terminal 10. Such a spectacle-type terminal 10 will be described next.

[0086] Figure 8 shows a modified example of the eyeglass-type terminal 10 according to this embodiment. In the modified eyeglass-type terminal 10, components that are substantially the same as those in the eyeglass-type terminal 10 according to this embodiment shown in Figure 1 are given the same reference numerals, and their descriptions are omitted. The appearance of the modified eyeglass-type terminal 10 may be almost the same as that of the eyeglass-type terminal 10 shown in Figure 1.

[0087] In the modified spectacle-type terminal 10, multiple projection substrates 100 are fixed to the frame 110. In this case, the multiple projection substrates 100 are fixed to the frame 110 such that at least a portion of the emission regions 230 provided on each of the multiple projection substrates 100 overlap in a plan view substantially parallel to the XY plane. Figure 8 shows an example in which three projection substrates 100R, projection substrate 100G, and projection substrate 100B are fixed to the frame 110 of the spectacle-type terminal 10, and the emission regions 230R, emission region 230G, and emission region 230B of the three projection substrates 100 overlap in a plan view in the XY plane.

[0088] The projection unit 120 irradiates each of the incident regions 210 provided on each of the multiple projection substrates 100 with projection light of a different wavelength. As a result, the emission regions 230 provided on each of the multiple projection substrates 100 emit image light corresponding to the projection light irradiated from the projection unit 120 onto the multiple incident regions 210, from the second surface of each of the multiple projection substrates 100 towards the user's eye.

[0089] A user wearing such glasses-type terminal 10 will observe an image in which image light of different wavelengths is superimposed, thus enabling them to observe an image with mixed colors. Figure 8 shows an example in which the projection unit 120 irradiates the incident regions 210 of three projection substrates 100 with three projection lights corresponding to the three primary colors of RGB (red, green, and blue) that form the image. The three projection substrates 100 then emit the three superimposed image lights corresponding to the three primary colors of RGB towards the user's eyes. As a result, the user can, for example, observe two images. n An image with multiple colors can be observed, where n is a positive integer such as 4, 8, 16, 24, etc.

[0090] Although the present invention has been described above using embodiments, 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 its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and 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 combinations are combined with the effects of the original embodiments. [Explanation of Symbols]

[0091] 10. Glasses-type terminal 20 Input Rays 30 Output ray beam 100 Projection board 110 frames 112 Glass substrate 120 Projection section 210 Incidence area 212 First groove 220 branching region 222 Second trench section 222a First protrusion 222b First recess 224 1st divided area 226 1st reflection area 230 Output area 232 Third groove 234 Second divided area 236 2nd reflection area

Claims

1. A projection substrate for projecting image light onto a second surface while transmitting at least a portion of the light incident from the first surface to the second surface opposite the first surface, An incident region into which projection light for projecting the aforementioned image light is incident, A branching region having a first diffraction grating that guides the projected light incident from the incident region, An emission region having a second diffraction grating that guides a portion of the projected light incident from the branching region and then emits a portion of the projected light from the second surface, Equipped with, The incident region guides the incident projected light to the branching region. The branching region diffracts a portion of the projected light toward the emission region. The first diffraction grating has a plurality of first convex and concave portions, each consisting of a first convex portion and a first concave portion formed to repeat in a first direction that guides the projected light. The branch region has a plurality of first division regions, The first fill factor, which is the ratio of the width of the first protrusion in the first direction to the first period of the first uneven portion of one first divided region, is within a range that does not include the predetermined value of 0.5, and the first fill factor of the first divided region that is closer to the incident region than the first first divided region is within a range that includes the predetermined value of 0.

5. The depth of the first uneven portion of the first divided region is greater than the depth of the first uneven portion of the first divided region that is closer to the incident region than the first divided region. The absolute value of the difference between the first fill factor of the first divided region and the first fill factor of the first divided region closer to the incident region than the first divided region is smaller as the absolute value of the difference between the depth of the first uneven portion of the first divided region and the depth of the first uneven portion of the first divided region closer to the incident region than the first divided region is larger. The first fill factor of the first divided region furthest from the incident region among the plurality of first divided regions is in the range of 0.35 or less or 0.65 or more, and the first fill factor of the first divided region closer to the incident region than the first divided region is in the range of 0.3 or more and 0.7 or less. projection board.

2. A projection substrate for projecting image light onto a second surface while transmitting at least a portion of the light incident from the first surface to the second surface opposite the first surface, An incident region into which projection light for projecting the aforementioned image light is incident, A branching region having a first diffraction grating that guides the projected light incident from the incident region, An emission region having a second diffraction grating that guides a portion of the projected light incident from the branching region and then emits a portion of the projected light from the second surface, Equipped with, The incident region guides the incident projected light to the branching region. The branching region diffracts a portion of the projected light toward the emission region. The first diffraction grating has a plurality of first convex and concave portions, each consisting of a first convex portion and a first concave portion formed to repeat in a first direction that guides the projected light. The branch region has a plurality of first division regions, The first fill factor, which is the ratio of the width of the first protrusion in the first direction to the first period of the first uneven portion of one first divided region, is within a range that does not include the predetermined value of 0.5, and the first fill factor of the first divided region that is closer to the incident region than the first first divided region is within a range that includes the predetermined value of 0.

5. The depth of the first uneven portion of the first divided region is greater than the depth of the first uneven portion of the first divided region that is closer to the incident region than the first divided region. The absolute value of the difference between the first fill factor of the first divided region and the first fill factor of the first divided region closer to the incident region than the first divided region is smaller as the absolute value of the difference between the depth of the first uneven portion of the first divided region and the depth of the first uneven portion of the first divided region closer to the incident region than the first divided region is larger. The second diffraction grating has a plurality of second convex and concave portions, each consisting of a second convex portion and a second concave portion formed to repeat in a second direction that guides the projected light. The ejection region has a plurality of second divided regions, The second fill factor, which is the ratio of the width of the second protrusion in the second direction to the second period of the second convexity of the second division region in the second division region that is closer to the branch region than one of the multiple second division regions, is within the range of 0.3 or more and 0.7 or less. The second fill factor of the first second division region is within the range of 0.35 or less or 0.65 or more. projection board.

3. A projection substrate for projecting image light onto a second surface while transmitting at least a portion of the light incident from the first surface to the second surface opposite the first surface, An incident region into which projection light for projecting the aforementioned image light is incident, A branching region having a first diffraction grating that guides the projected light incident from the incident region, An emission region having a second diffraction grating that guides a portion of the projected light incident from the branching region and then emits a portion of the projected light from the second surface, Equipped with, The incident region guides the incident projected light to the branching region. The branching region diffracts a portion of the projected light toward the emission region. The first diffraction grating has a plurality of first convex and concave portions, each consisting of a first convex portion and a first concave portion formed to repeat in a first direction that guides the projected light. The branch region has a plurality of first division regions, The first fill factor, which is the ratio of the width of the first protrusion in the first direction to the first period of the first uneven portion of one first divided region, is within a range that does not include the predetermined value of 0.5, and the first fill factor of the first divided region that is closer to the incident region than the first first divided region is within a range that includes the predetermined value of 0.

5. The depth of the first uneven portion of the first divided region is greater than the depth of the first uneven portion of the first divided region that is closer to the incident region than the first divided region. The absolute value of the difference between the first fill factor of the first divided region and the first fill factor of the first divided region closer to the incident region than the first divided region is smaller as the absolute value of the difference between the depth of the first uneven portion of the first divided region and the depth of the first uneven portion of the first divided region closer to the incident region than the first divided region is larger. The second diffraction grating has a plurality of second convex and concave portions, each consisting of a second convex portion and a second concave portion formed to repeat in a second direction that guides the projected light. The ejection region has a plurality of second divided regions, The second fill factor, which is the ratio of the width of the second protrusion in the second direction to the second period of the second uneven portion of the second division region that is closer to the branch region than one of the plurality of second division regions, is within the range including the predetermined value of 0.

5. The first period of each of the plurality of first divided regions is 50 nm or more and 1 μm or less. The depth of the first uneven portion of the first divided region is 50 nm or more and 800 nm or less. The first fill factor of the first division region is 0.35 or less or 0.65 or more. The depth of the first uneven portion of the first divided region that is closer to the incident region than the first divided region is 5 nm or more and 100 nm or less. The first fill factor of the first division region that is closer to the incident region than the first division region is 0.3 or more and 0.7 or less. The second period of each of the plurality of second divided regions is 100 nm or more and 1 μm or less. The depth of the second uneven portion of the second divided region is 50 nm or more and 800 nm or less. The second fill factor of the first second division region is 0.35 or less or 0.65 or more. The depth of the second uneven portion in the second division region that is closer to the branch region than the first second division region is 5 nm or more and 100 nm or less. The second fill factor of the second division region that is closer to the branch region than the first second division region is 0.3 or more and 0.7 or less. projection board.

4. The first period of each of the multiple first divided regions is the same. A projection substrate according to any one of claims 1 to 3.

5. The second period of the second uneven portion of each of the plurality of second divided regions is the same. The projection substrate according to claim 2 or 3.

6. The depth of the second uneven portion in the first second divided region is greater than the depth of the second uneven portion in the second divided region that is closer to the branch region than the first second divided region. The absolute value of the difference between the second fill factor, which is the ratio of the width of the second protrusion in the second direction to the second period of the second uneven portion of the first second divided region, and the second fill factor of the second divided region closer to the branch region than the first second divided region, is smaller as the absolute value of the difference between the depth of the second uneven portion of the first second divided region and the depth of the second uneven portion of the second divided region closer to the branch region than the first second divided region increases. The projection substrate according to claim 2 or 3.

7. A glasses-type terminal worn by the user, The projection substrate according to any one of claims 1 to 3 is provided as at least one of the lens for the user's right eye and the lens for the user's left eye, and transmits at least a portion of the light incident from the first surface to the user's eye while projecting the image light onto the second surface, The frame that secures the projection substrate, The frame is provided with a projection unit that irradiates the incident region of the projection substrate with the projection light for projecting the image light onto the emission region. A glasses-type terminal equipped with this feature.

Images