Method for manufacturing a waveguide and a head-mounted display having the waveguide

Abstract

To provide a head mount display.SOLUTION: A head mount display is disposed in front of at least one eye of a user and includes a display unit, a first waveguide, and a second waveguide. The display unit provides an image light flux. The first waveguide is positioned between the display unit and the second waveguide. The first waveguide is used to propagate the image light flux to the second waveguide and to adjust a shape of the image light flux, thereby maintaining a viewing angle and enlarging a pupil opening on a single dimension. The second waveguide is used to propagate the image light flux to at least one eye of the user and to extend a propagation path of light and provide uniform image light flux. In this way, the head mount display has a large viewing angle and can maintain viewing quality of the user.SELECTED DRAWING: Figure 1B

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical structure and an optical device having the optical structure, and particularly to a method for manufacturing a waveguide and a head-mounted display having the waveguide.

Background Art

[0002] Due to the technological progress of displays and people's demands for advanced technologies, the technologies of virtual reality and augmented reality have gradually matured. Among them, a head mounted display (HMD) is a display used to implement such technologies. The history of the development of head-mounted displays can be traced back to the 1970s in the US military. The US military used an optical projection system to project images and text messages on a display element onto the user's eyes. In recent years, as the resolution of microdisplays has become increasingly high and the size and power consumption have become increasingly small, head-mounted displays have also evolved into portable display devices. In addition to the military field, the display technology of head-mounted displays has also grown and occupies an important position in related fields such as industrial production, simulation training, 3D displays, medicine, sports, navigation, and electronic games.

[0003] However, in the optical engine design of a head-mounted display, in order to achieve the goals of a large viewing angle and a small volume, many difficulties may be faced in the design. For example, due to the conservation of étendue, when the viewing angle increases, the f-number increases and the pupil aperture decreases, which requires raising the target value of the modulation transfer function (MTF) required for the lens. Therefore, when trying to achieve an output with a large-angle viewing angle under a finite length, the reduction of the pupil aperture is a factor that needs to be considered. However, due to the reduction of the pupil aperture, it becomes more difficult to expand in the wave guide of the image light beam, and thus the brightness of the image light beam cannot be reduced. Regarding the pupil of the human eye, when irradiated with a light amount of luminance of 1000 to 2000 nits, its size is only about 2.5 millimeters, so in the case of a small pupil aperture, it becomes even more difficult to allow the image light at all angles of the image light beam to smoothly enter the human eye.

[0004] On the other hand, in the conventional geometric wave guide design, the pupil aperture of the optical engine of the head-mounted display needs to enter the wave guide. Thus, the minimum position of the light beam reduction of the pupil aperture can make the maximum number of light rays enter the wave guide at the position where it enters the main wave guide, so as to improve the efficiency and smoothly propagate the large-angle light rays that are difficult to enter the wave guide and effectively enter the main wave guide. However, under such a design, the length of the pupil aperture and the wave guide it passes through require a certain length or more. In this way, when the storage space in the head-mounted display cannot accommodate a wave guide of a certain length, it is likely to cause the loss of a large-angle image screen and a decrease in efficiency.

[0005] Note that this "Background Art" section is only for helping the understanding of the content of the present invention. Therefore, the content disclosed in this "Background Art" section may include technologies unknown to those skilled in the art. Thus, the content disclosed in this "Background Art" section does not mean that the content, or the problems to be solved by one or more embodiments of the present invention, have already been well-known to those skilled in the art before the filing of the present invention.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a head-mounted display having a large viewing angle, reducing the volume of the head-mounted display, shortening the length of the waveguide element, and being more adaptable to the contour of a human face. Thereby, the pupil aperture can be enlarged in one dimension, and a uniform image light beam can be provided.

[0007] The present invention further provides a method for manufacturing a waveguide, whereby a waveguide capable of enlarging the pupil aperture or extending the light propagation path can be easily manufactured.

[0008] Other objects and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

Means for Solving the Problems

[0009] In order to achieve one or some or all of the above-mentioned objects or other objects, according to an embodiment of the present invention, a head-mounted display is provided. The head-mounted display is disposed in front of at least one eye of a user and includes a display unit, a first wave guide, and a second wave guide. The display unit provides an image light beam. The first wave guide is located in the propagation path of the image light beam. The first wave guide includes a first plate body and a plurality of first optical microstructures. The plurality of first optical microstructures are located in the first plate body, and these first optical microstructures include a central optical microstructure and edge optical microstructures. The central optical microstructures are respectively located on both sides of the main axis of the image light beam. The edge optical microstructures are respectively located on both sides of the main axis of the image light beam, and the central optical microstructure is closer to the main axis of the image light beam than the edge optical microstructure. Among them, after the image light beam enters the first plate body through the first surface of the first plate body, a part of the image light beam passes through the central optical microstructure, and other parts of the image light beam propagate to the corresponding edge optical microstructures via the central optical microstructure respectively. After passing through the corresponding edge optical microstructures, they leave the first plate body from the second surface of the first plate body. The second wave guide is located in the propagation path of the image light beam. Among them, the first wave guide is located between the display unit and the second wave guide. The first wave guide is used to propagate the image light beam to the second wave guide and to adjust the shape of the image light beam. The second wave guide is used to propagate the image light beam to at least one eye of the user.The second waveguide includes a second plate body, a plurality of second optical microstructures, and a plurality of light guiding optical film patterns. The second plate body has a light incident surface, and the light incident surface is connected to the first surface and the second surface of the second plate body. The plurality of second optical microstructures are located within the second plate body. Among them, each second optical microstructure has an optical surface, and these optical surfaces of these second optical microstructures are respectively inclined with respect to the first surface of the second plate body. These light guiding optical film patterns are located on these optical surfaces of these second optical microstructures, and these light guiding optical film patterns allow a part of the video light beam to pass through and reflect another part of the video light beam. Among them, after the video light beam enters the second plate body via the light incident surface, a part of the video light beam passes through these light guiding optical film patterns, and after another part of the video light beam is reflected by these light guiding optical film patterns, it leaves the second plate body from the second surface of the second plate body.

[0010] In one embodiment of the present invention, the ratio between the orthographic projection area of these light guiding optical film patterns on the second plate body and the area of the second plate body is less than 30%.

[0011] In one embodiment of the present invention, the included angle between the above-mentioned first waveguide and the second waveguide is between 90 degrees and 135 degrees.

[0012] In one embodiment of the present invention, the first optical microstructures of the above-mentioned first waveguide are arranged along a first direction, the second optical microstructures of the second waveguide are arranged along a second direction, and the first direction is perpendicular to the second direction.

[0013] In one embodiment of the present invention, each of the above-mentioned first optical microstructures has an optical surface, and the optical surfaces of the first optical microstructures respectively extend from a position close to the main axis of the video light beam and the first surface to a position away from the main axis of the video light beam and close to the second surface, and are inclined with respect to the first surface.

[0014] In one embodiment of the present invention, the above-mentioned first waveguide has a first optical region and a second optical region. The first optical region and the second optical region are respectively located on both sides of the main axis of the video light beam. The inclination direction of the optical surface of the first optical microstructure located in the first optical region and the inclination direction of the optical surface of the first optical microstructure located in the second optical region are mirror-symmetric.

[0015] In one embodiment of the present invention, the above-mentioned first waveguide has at least one optical film. The at least one optical film is located on at least one of the optical surfaces of the first optical microstructure, and the optical film allows a part of the video light beam to pass through and reflects the other part of the video light beam.

[0016] In one embodiment of the present invention, the reflectivity of at least one optical film located on the above-mentioned central optical microstructure or edge optical microstructure with respect to the video light beam is greater than the transmittance with respect to the video light beam.

[0017] In one embodiment of the present invention, the above-mentioned first optical microstructure further includes a plurality of relay optical microstructures, and there is at least one relay optical microstructure between the central optical microstructure and the edge optical microstructure. Among them, after a part of the video light beam from the central optical microstructure passes through the relay optical microstructure, it propagates to the corresponding edge optical microstructure, and the other part of the video light beam from the central optical microstructure is reflected by the relay optical microstructure and leaves the first plate body from the second surface.

[0018] In one embodiment of the present invention, the reflectivity of at least one optical film located on the above-mentioned relay optical microstructure with respect to the video light beam is smaller than the transmittance with respect to the video light beam.

[0019] In one embodiment of the present invention, the above-mentioned first plate body includes a first structural layer and a second structural layer. The first structural layer of the first plate body has a plurality of first inclined surfaces and a plurality of first connection surfaces. Among them, each first connection surface is connected to different ends of adjacent first inclined surfaces to form a first serrated structure. The second structural layer of the first plate body has a plurality of second inclined surfaces and a plurality of second connection surfaces. Among them, each second connection surface is connected to different ends of adjacent second inclined surfaces to form a second serrated structure, and the second inclined surface corresponds to the first inclined surface, and the second connection surface corresponds to the first connection surface. Thus, the first serrated structure coincides with the second serrated structure, and the second inclined surface contacts the first inclined surface to form an optical surface of the first optical microstructure.

[0020] In one embodiment of the present invention, the above-mentioned first waveguide has at least one optical film. The at least one optical film is located on at least one of the first inclined surface of the first structural layer and the second inclined surface of the second structural layer, and the optical film allows a part of the video light beam to pass through and reflects another part of the video light beam.

[0021] In one embodiment of the present invention, the minimum distance between two adjacent above-mentioned light guiding optical film patterns is smaller than the size of the user's pupil.

[0022] In one embodiment of the present invention, the ratio of the size of each above-mentioned light guiding optical film pattern to the minimum distance between two adjacent light guiding optical film patterns is between 0.6 and 0.7.

[0023] In one embodiment of the present invention, the above-mentioned second plate body includes a first structural layer and a second structural layer. The first structural layer of the second plate body has a plurality of first inclined surfaces and a plurality of first connection surfaces. Among them, each first connection surface is connected to different ends of adjacent first inclined surfaces to form a first serrated structure. The second structural layer of the second plate body has a plurality of second inclined surfaces and a plurality of second connection surfaces. Among them, each second connection surface is connected to different ends of adjacent second inclined surfaces to form a second serrated structure, and the second inclined surface corresponds to the first inclined surface, and the second connection surface corresponds to the first connection surface. Thus, the first serrated structure coincides with the second serrated structure, and the second inclined surface contacts the first inclined surface to form an optical surface of the second optical microstructure.

[0024] In one embodiment of the present invention, the above-described second waveguide has a first optical region and a second optical region. Among them, the first optical region is located between the light incident surface and the second optical region, and the first serrated structure, the second serrated structure, and the second optical microstructure are located within the second optical region. The second waveguide further includes a light guiding film. The light guiding film is located on the light guiding surface inside the second waveguide. The light guiding surface is located within the first optical region and is parallel to the first surface. Among them, the light guiding film allows some of the video light beams to pass through and reflects other portions of the video light beams. Moreover, the video light beams that have passed through the light guiding film propagate in the second waveguide in a total reflection manner.

[0025] In one embodiment of the present invention, the first structural layer of the above-described second waveguide further has a first plane, and the second structural layer further has a second plane. The second plane contacts the first plane to form a light guiding surface.

[0026] In order to achieve one or some or all of the above-mentioned purposes or other purposes, according to one embodiment of the present invention, a method for manufacturing a waveguide of a head-mounted display is provided. Among them, the waveguide is used to propagate video light beams, and the method for manufacturing the waveguide includes the following steps. That is, a first structural layer is provided. Among them, the first structural layer has a plurality of first inclined surfaces and a plurality of first connection surfaces. Among them, each first connection surface is connected to different ends of adjacent first inclined surfaces to form a first serrated structure. A second structural layer is provided. Among them, the second structural layer has a plurality of second inclined surfaces and a plurality of second connection surfaces. Among them, each second connection surface is connected to different ends of adjacent second inclined surfaces to form a second serrated structure. At least one optical film is formed on at least one first inclined surface of the first structural layer or at least one second inclined surface of the second structural layer. Among them, the at least one optical film allows some of the video light beams to pass through and reflects other portions of the video light beams. The first structural layer and the second structural layer are joined. Among them, the second inclined surface corresponds to the first inclined surface, and the second connection surface corresponds to the first connection surface. Thereby, the first serrated structure coincides with the second serrated structure, and the second inclined surface contacts the first inclined surface to form a plurality of optical surfaces of a plurality of optical microstructures.

[0027] In one embodiment of the present invention, the above-described waveguide is a first waveguide, the first structural layer and the second structural layer form a first plate body of the first waveguide after joining, the optical microstructure is a plurality of first optical microstructures, the first waveguide has a first optical region and a second optical region, the first optical region and the second optical region are respectively located on both sides of the main axis of the video light beam, and the inclination direction of the optical surface of the first optical microstructure located in the first optical region and the inclination direction of the optical surface of the first optical microstructure in the second optical region are mirror-symmetric.

[0028] In one embodiment of the present invention, the above-described first optical microstructure includes two central optical microstructures and two edge optical microstructures. The central optical microstructures are respectively located on both sides of the main axis of the video light beam. The edge optical microstructures are respectively located on both sides of the main axis of the video light beam, and the central optical microstructure is closer to the main axis of the video light beam than the edge optical microstructure. Among them, after the video light beam enters the first plate body via the first surface, a part of the video light beam passes through the central optical microstructure, and the other part of the video light beam propagates to the corresponding edge optical microstructure via the central optical microstructure, and then leaves the first plate body after passing through the corresponding edge optical microstructure.

[0029] In an embodiment of the present invention, the above-mentioned waveguide is a second waveguide. After the first structural layer and the second structural layer are joined, they form the second plate body of the second waveguide. The optical microstructure is a plurality of second optical microstructures, and the method for forming at least one optical film includes the following steps. That is, a mask is provided, and the mask has a plurality of through holes. The mask is overlapped with the first structural layer or the second structural layer, and the projection plane of the through hole on the first structural layer or the second structural layer is overlapped with at least one first inclined surface of the first structural layer or at least one second inclined surface of the second structural layer. Through the plurality of through holes of the mask, a plurality of light guiding optical film patterns of at least one optical film are formed on at least one first inclined surface of the first structural layer or at least one second inclined surface of the second structural layer. Among them, after the video light beam enters the second plate body through the light incident surface, a part of the video light beam passes through the light guiding optical film pattern, and the other part of the video light beam is reflected by the light guiding optical film pattern and then leaves the second plate body. Also, the ratio between the orthographic projection area of the light guiding optical film pattern on the second plate body and the area of the second plate body is less than 30%.

[0030] In an embodiment of the present invention, the above-mentioned mask has a flat plate structure or a serrated structure. When the mask has a serrated structure, the serrated structure coincides with the first serrated structure or the second serrated structure, and the through holes of the mask penetrate through a plurality of inclined surfaces of the serrated structure. The inclined surfaces of the serrated structure correspond to at least one first inclined surface of the first structural layer or at least one second inclined surface of the second structural layer.

[0031] In one embodiment of the present invention, the above-described second waveguide has a first optical region and a second optical region. Among them, the first optical region is located between the light incident surface and the second optical region, and the first structural layer further has a first plane, and the second structural layer further has a second plane. The first plane and the second plane are located within the first optical region. The first serrated structure, the second serrated structure, and the second optical microstructure are located within the second optical region. And the method for manufacturing the waveguide further includes the following steps. That is, a light guiding film is formed on the first plane or the second plane. Among them, the light guiding film allows a part of the video light beam to pass through and reflects the other part of the video light beam. After the first structural layer and the second structural layer are joined, the first plane contacts the second plane to form a light guiding surface, and the video light beam passing through the light guiding film on the light guiding surface propagates in the second waveguide in a total reflection manner.

[0032] As described above, the embodiment of the present invention has at least one of the following advantages or effects. That is, in the embodiment of the present invention, due to the arrangement of the first waveguide, the video light beam can propagate to the second waveguide, and the shape of the light can be adjusted to maintain the viewing angle. Also, the pupil aperture can be enlarged in a single dimension. Due to the arrangement of the second waveguide, the propagation path of the video light beam can be extended and has good uniformity. In this way, the head-mounted display has a large viewing angle and can provide good viewing quality.

[0033] To make the above features and advantages of the present invention more obvious, the following will be described in detail by way of examples with reference to the accompanying drawings.

Brief Description of the Drawings

[0034]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 4A

Figure 4B

Figure 4C

Best Mode for Carrying Out the Invention

[0035] The above-mentioned and other technical contents, features, functions, and effects of the present invention will become clear from the following detailed description of the preferred embodiments based on the attached drawings. Note that the terms regarding the directions mentioned in the following embodiments, such as up, down, left, right, front, back, etc., are only the directions of the attached drawings. Therefore, the terms of the directions used are only for explaining the present invention and are not for limiting the present invention.

[0036] FIG. 1A is a top view when a user wears a head-mounted display according to an embodiment of the present invention. FIG. 1B is a diagram showing the architecture of the head-mounted display of FIG. 1A. Referring to FIGS. 1A and 1B. In this embodiment, the head-mounted display 300 is disposed in front of at least one eye EY of the user, and includes an illumination system 310, a display unit 320, and a waveguide element WG including a first waveguide 100 and a second waveguide 200. The display unit 320 provides an image light beam IB. In this embodiment, the display unit 320 includes, for example, a Digital Micromirror Device (DMD), which is used to convert the illumination light beam (first illumination light beam) from the illumination system 310 into the image light beam IB. In one embodiment, the display unit 320 includes, for example, an LCoS (Liquid Crystal On Silicon) display device, but the present invention is not limited to the type of the display unit 320. The display unit 320 may further include a prism, which is used to propagate the illumination light beam.

[0037] Specifically, as shown in FIGS. 1A and 1B, after leaving the display unit 320, the image light beam IB propagates to the waveguide element WG via the lens module LS and converges at the stop ST.

[0038] In this embodiment, the first waveguide 100 is located between the display unit 320 and the second waveguide 200. The first waveguide 100 is used to propagate the image light beam IB to the second waveguide 200 and to adjust the shape of the image light beam IB. The second waveguide 200 is used to propagate the image light beam IB to at least one eye EY of the user.

[0039] In this embodiment, the stop ST is located outside the display unit 320. In the propagation path of the video light beam IB, the display unit 320 is located between the illumination system 310 and the stop ST. The stop ST is located in one of the first waveguide 100, the second waveguide 200, or the connection point between the first waveguide 100 and the second waveguide 200. The stop ST is the position having the minimum cross-sectional area of the light beam reduction of the video light beam IB. For example, in this embodiment, the minimum cross-sectional area of the light beam reduction of the video light beam IB is defined as the pupil aperture, and the shape of the pupil aperture is, for example, circular. However, in this embodiment, the shape and size of the pupil aperture at the stop ST are merely illustrative, and the present invention is not limited thereto.

[0040] In this embodiment, the video light beam IB can be converged on the stop ST and, after passing through the stop ST, diverge and propagate via the waveguide element WG. In this embodiment, the waveguide element WG has a light inlet end located on the first waveguide 100 and a light outlet end located on the second waveguide 200. The light inlet end is used to receive the video light beam IB. The video light beam IB can propagate to the user's eyes by the propagation of the waveguide element WG and the emission from the light outlet end.

[0041] As shown in FIGS. 1A and 1B, in this embodiment, the waveguide element WG formed by the combination of the first waveguide 100 and the second waveguide 200 has an edge-type waveguide architecture. In this embodiment, the included angle θ between the first waveguide 100 and the second waveguide 200 is set as an obtuse angle and is between 90 degrees and 135 degrees. In this way, the stop ST of the head-mounted display is located within the waveguide element WG, and the maximum number of image light beams can enter the waveguide element WG, so that the efficiency can be improved, and the large-angle image light beams that are difficult to enter the waveguide element WG can be smoothly propagated and effectively enter therein. The length from the required lens module LS to the stop ST can also be shortened to within 8 millimeters. Compared with the conventional head-mounted display, when having the same optical structure (i.e., the illumination system 310 and the display unit 320), the length from the lens module LS to the stop ST in the conventional head-mounted display is about 11 millimeters. As can be seen, the waveguide element WG formed by the combination of the first waveguide 100 and the second waveguide 200 in this embodiment can reduce the size, is easy to be installed in the head-mounted display, and can reduce the risk of the loss of the large-angle image screen and the decrease in efficiency.

[0042] In addition, the waveguide element WG formed by the combination of the first waveguide 100 and the second waveguide 200 in this embodiment can further conform its structure to the contour of the user's head, so the length of the waveguide element WG can be shortened. Specifically, when the first waveguide 100 is perpendicular to the second waveguide 200, a gap may occur between the waveguide element WG and the user's face, so the required length of the waveguide element WG has to be longer. However, as shown in FIG. 1A, in this embodiment, the included angle between the first waveguide 100 and the second waveguide 200 is between 90 degrees and 135 degrees. In this way, since it can conform to the contour of the user's head, the gap between the waveguide element WG and the user's face can be reduced as much as possible, and the required length of the waveguide element WG can be further shortened. As a result, the image light beam IB can enter the user's eyes faster, has a relatively less tendency to spread, and can expand the visible angle of the eyes.

[0043] Hereinafter, with reference to FIGS. 2A to 3E, the structures of the first waveguide 100 and the second waveguide 200 will be described in more detail respectively.

[0044] FIG. 2A is a perspective view of the first waveguide in FIG. 1B. FIG. 2B is an exploded view of the first waveguide in FIG. 2A. FIG. 2C is a side view of the first waveguide in FIG. 2A. FIG. 2D is an optical path diagram of the first waveguide in FIG. 2A. As shown in FIGS. 2A to 2C, in this embodiment, the first waveguide 100 includes a first plate body 110 and a plurality of first optical microstructures 120. The first plate body 110 has a first surface 111S and a second surface 112S. The plurality of first optical microstructures 120 are located in the first plate body 110. The first optical microstructure 120 includes two central optical microstructures 121, a plurality of relay optical microstructures 122, and two edge optical microstructures 123. The two central optical microstructures 121 are respectively located on both sides of the main axis O of the video light beam IB. The two edge optical microstructures 123 are respectively located on both sides of the main axis O of the video light beam IB, and the two central optical microstructures 121 are closer to the main axis O of the video light beam IB than the two edge optical microstructures 123. In addition, there is at least one relay optical microstructure 122 between the central optical microstructure 121 and the edge optical microstructure 123.

[0045] Furthermore, as shown in FIGS. 2A to 2C, in this embodiment, each first optical microstructure 120 has an optical surface 110OS, and the optical surface 110OS of the first optical microstructure 120 extends along the direction from near the main axis O of the video light beam IB to away from the main axis O of the video light beam IB, and is inclined with respect to the first surface 111S. In addition, in this embodiment, the first waveguide 100 has a first optical region 101R and a second optical region 102R. The first optical region 101R and the second optical region 102R are respectively located on both sides of the main axis O of the video light beam IB, and the inclination direction of the optical surface 110OS of the first optical microstructure 120 located in the first optical region 101R and the inclination direction of the optical surface 110OS of the first optical microstructure 120 in the second optical region 102R are mirror-symmetrical.

[0046] Furthermore, as shown in FIG. 2C, the first waveguide 100 has at least one optical film 110F, and at least one optical film 110F is located on at least one of the optical surfaces 110OS of the first optical microstructure 120, and the optical film 110F is used to allow a part of the video light beam IB to pass through and reflect another part of the video light beam IB. For example, the first waveguide 100 is fabricated in the following steps. First, as shown in FIG. 2B, a first structural layer 111 and a second structural layer 112 are provided, where the first structural layer 111 has a plurality of first inclined surfaces 111IS and a plurality of first connection surfaces 111LS, and the second structural layer 112 also has a plurality of second inclined surfaces 112IS and a plurality of second connection surfaces 112LS. Each first connection surface 111LS of the first structural layer 111 is connected to different ends of adjacent first inclined surfaces 111IS to form a first serrated structure 111ZS, and each second connection surface 112LS of the second structural layer 112 is connected to different ends of adjacent second inclined surfaces 112IS to form a second serrated structure 112ZS. Also, at least one optical film 110F is formed on at least one of the first inclined surfaces 111IS of the first structural layer 111 or at least one of the second inclined surfaces 112IS of the second structural layer 112. In other words, at least one optical film 110F is located on at least one of the first inclined surfaces 111IS of the first structural layer 111 and the second inclined surfaces 112IS of the second structural layer 112.

[0047] Subsequently, the first structural layer 111 and the second structural layer 112 are joined, where the second inclined surface 112IS corresponds to the first inclined surface 111IS, and the second connection surface 112LS corresponds to the first connection surface 111LS. As a result, the first serrated structure 111ZS coincides with the second serrated structure 112ZS, and the second inclined surface 112IS contacts the first inclined surface 111IS to form a plurality of optical surfaces 110OS of a plurality of optical microstructures. In this way, the first structural layer 111 and the second structural layer 112 can form the first plate body 110 of the first waveguide 100 after being joined.

[0048] As such, as shown in FIG. 2D, after the image light beam IB enters the first plate body 110 via the first surface 111S, a part of the image light beam IB passes through the two central optical microstructures 121, and the other part of the image light beam IB propagates to the corresponding edge optical microstructures 123 via the central optical microstructures 121. Further, a part of the image light beam IB from the central optical microstructure 121 passes through the relay optical microstructure 122 and then propagates to the corresponding edge optical microstructure 123, and the other part of the image light beam IB from the central optical microstructure 121 is reflected by the relay optical microstructure 122 and can leave the first plate body 110 from the second surface 112S. The image light beam IB that is not reflected by the relay optical microstructure 122 and does not leave the first plate body 110 continues to propagate in the first plate body 110, and after passing through the corresponding edge optical microstructure 123, it can leave the first plate body 110 from the second surface 112S. As can be seen from FIG. 2D, the image light beam IB can form a mirror image centered on the main axis O and be emitted in parallel to leave the first plate body 110.

[0049] Specifically, in this embodiment, the optical films 110F located on different optical microstructures may have different reflectivity designs according to different reflection / transmission needs. For example, in this embodiment, the reflectivity of at least one optical film 110F located on the above-mentioned two central optical microstructures 121 or edge optical microstructures 123 with respect to the video light beam IB is greater than the transmittance with respect to the video light beam IB, and the reflectivity of at least one optical film 110F located on the above-mentioned relay optical microstructure 122 with respect to the video light beam IB is smaller than the transmittance with respect to the video light beam IB. In this way, the central optical microstructure 121 having high reflection characteristics can effectively reflect the video light beam IB and extend its propagation path backward. The relay optical microstructure 122 having high transmittance characteristics can extend the propagation path of the video light beam IB backward and further reflect the video light beam IB to be emitted from the first plate body 110. The edge optical microstructure 123 having high reflection characteristics can effectively emit the video light beam IB from the first plate body 110. In this way, as shown in FIGS. 1B and 2C, the video light beam IB leaving the first plate body 110 of the first waveguide 100 can propagate into the second waveguide 200, whereby the pupil aperture of the video light beam IB propagating into the second waveguide 200 can be effectively enlarged.

[0050] In addition, the image light beam IB can further expand its pupil aperture by the optical film 110F. Therefore, the characteristics of the optical film 110F can also affect the uniformity of the entire pupil aperture, for example, the uniformity of luminance and color. Furthermore, when the uniformity of the pupil aperture is different, it can also affect the uniformity of the color dots entering the pupil. This is because the illumination light beam for forming the image light beam IB is emitted from the light-emitting element of the illumination system 310, and due to the different distributions of the color light emitted from the light-emitting element of the illumination system 310, the uniformity of the pupil apertures of different color lights can have different uniformities under different colors. For example, when the distributions of the pupil apertures of red light, green light, and blue light are different, the color uniformity is poor, but when the uniformities of the pupil apertures of red light, green light, and blue light are exactly the same, the uniformity of the color dots can be significantly improved. Therefore, in this embodiment, the optical film 110F may perform a combination of reflectance / transmittance according to the conditions of color light of different wavelengths. In this way, when it is determined that the characteristics of the optical film 110F and the uniformity of the pupil apertures of different color lights are all in an ideal state, the distribution of the color dots output from the display unit 320 approaches the distribution of the color dots visible to the pupil of the human eye, so the viewing quality can be improved.

[0051] Also, in FIG. 2C, the number of the optical films 110F is shown by taking 10 optical films located on different optical microstructures as an example, but the present invention is not limited thereto, and the number of the optical films 110F can also change depending on the different optical machines. However, in any case, there is at least one or more optical films.

[0052] FIG. 3A is an exploded view of the second waveguide in FIG. 1B. FIG. 3B is a diagram showing the fabrication of the mask of the second waveguide in FIG. 3A. FIG. 3C is a front view showing the accuracy of the mask of the second waveguide in FIG. 3A. FIG. 3D is a bottom view of the mask in FIG. 3C. FIG. 3E is a front view of the second waveguide in FIG. 1B. As shown in FIGS. 3A to 3E, in this embodiment, the second waveguide 200 includes a second plate body 210, a plurality of second optical microstructures 220, and a plurality of light guiding optical film patterns 210FP. The second plate body 210 has a first surface 211S, a second surface 212S, and a light incident surface connected to the second surface 112S. The plurality of second optical microstructures 220 are located in the second plate body 210. Among them, each second optical microstructure 220 has at least one optical surface 210OS, and the optical surface 210OS of the second optical microstructure 220 is inclined with respect to the first surface 211S respectively.

[0053] Furthermore, as shown in FIGS. 3A and 3B, the plurality of light guiding optical film patterns 210FP are located on the optical surface 210OS of the second optical microstructure 220, and the light guiding optical film pattern 210FP is used to allow a part of the video light beam IB to pass through and reflect the other part of the video light beam IB. For example, the second waveguide 200 is fabricated in the following steps. First, a first structural layer 211 and a second structural layer 212 are provided. Among them, the first structural layer 211 has a plurality of first inclined surfaces 211IS and a plurality of first connection surfaces 211LS, and the second structural layer 212 also has a plurality of second inclined surfaces 212IS and a plurality of second connection surfaces 212LS. Each first connection surface 211LS is connected to different ends of adjacent first inclined surfaces 211IS to form a first serrated structure 211ZS, and each second connection surface 212LS is connected to different ends of adjacent second inclined surfaces 212IS to form a second serrated structure 212ZS.

[0054] At least one first inclined surface 211IS of the first structural layer 211 or at least one second inclined surface 212IS of the second structural layer 212 is formed with at least one optical film 210F, and the method of forming at least one optical film 210F includes the following steps. Provide a mask OM, and the mask OM has a plurality of through holes TH. For example, as shown in FIG. 3B, the mask OM may be a flat plate structure PS.

[0055] Furthermore, as shown in FIG. 3B, in this embodiment, the mask OM is superimposed on the first structural layer 211 or the second structural layer 212, and the projection surface of the through hole TH on the first structural layer 211 or the second structural layer 212 is made to be superimposed on at least one first inclined surface 211IS of the first structural layer 211 or at least one second inclined surface 212IS of the second structural layer 212. In this way, a plurality of light guiding optical film patterns 210FP of at least one optical film 210F can also be formed on at least one first inclined surface 211IS of the first structural layer 211 or at least one second inclined surface 212IS of the second structural layer 212 by the plurality of through holes TH of the mask OM shown in FIGS. 3C and 3D. It should be noted that the present invention is not limited thereto. Also, in another embodiment, the mask OM may be a toothed structure (as shown in FIGS. 3C and 3D).

[0056] Furthermore, as shown in FIGS. 3C and 3D, when the mask OM has a serrated structure, the serrated structure coincides with the first serrated structure 211ZS or the second serrated structure 212ZS, and the through holes TH of the mask OM penetrate through a plurality of inclined surfaces of the serrated structure. The inclined surfaces of the serrated structure correspond to at least one first inclined surface 211IS of the first structural layer 211 or at least one second inclined surface 212IS of the second structural layer 212. Subsequently, the mask OM shown in FIGS. 3C and 3D is superimposed on the first structural layer 211 or the second structural layer 212, and the projection surface of the through hole TH on the first structural layer 211 or the second structural layer 212 is made to superimpose on at least one first inclined surface 211IS of the first structural layer 211 or at least one second inclined surface 212IS of the second structural layer 212. In this way, a plurality of light guiding optical film patterns 210FP of at least one optical film 210F can also be formed on at least one first inclined surface 211IS of the first structural layer 211 or at least one second inclined surface 212IS of the second structural layer 212 by the plurality of through holes TH of the mask OM as shown in FIGS. 3C and 3D.

[0057] Subsequently, the first structural layer 211 and the second structural layer 212 are joined. Among them, the second inclined surface 212IS corresponds to the first inclined surface 211IS, and the second connection surface 212LS corresponds to the first connection surface 211LS. Thereby, the first serrated structure 211ZS coincides with the second serrated structure 212ZS, and the second inclined surface 212IS contacts the first inclined surface 211IS to form a plurality of optical surfaces 210OS of the plurality of optical microstructures. In this way, the first structural layer 211 and the second structural layer 212 can form the second plate body 210 of the second waveguide 200 after joining. Among them, the optical microstructure is a plurality of second optical microstructures 220, and a plurality of light guiding optical film patterns 210FP of at least one optical film 210F are formed on the optical surface 210OS.

[0058] For example, in this embodiment, the first optical microstructure 120 of the first waveguide 100 is arranged along the first direction D1, the second optical microstructure 220 of the second waveguide 200 is arranged along the second direction D2, and the first direction D1 is perpendicular to the second direction D2. In this way, since the arrangement methods of the optical microstructures in the first waveguide 100 and the second waveguide 200 are different, the functions of the second waveguide 200 and the first waveguide 100 are also different. The function of the first waveguide 100 is mainly to propagate the video light beam IB to the second waveguide 200 and effectively expand the pupil aperture of the video light beam IB coupled to the second waveguide 200. The function of the second waveguide 200 is mainly to propagate the video light beam IB to the user's eyes and provide a relatively large viewing angle. Therefore, the light guiding optical film pattern 210FP of the second waveguide 200 is further designed with a circular contour, and the sizes of the light guiding optical film patterns 210FP are inconsistent with each other, and there may be a gap between them. Thereby, the video light beam IB of the first waveguide 100 can propagate farther in the second waveguide 200, and the large-angle video light beam IB can be effectively controlled to be reflected by the light guiding optical film pattern 210FP of the second waveguide 200 and finally enter the eye EY, so that an optical system of the head-mounted display 300 with a large viewing angle can be formed.

[0059] More specifically, the distance between the light guiding optical film patterns 210FP needs to be defined according to the size of the pupil of the human eye, thereby avoiding the user feeling that the light guiding optical film patterns 210FP are too dense and enabling a good visual experience. For example, in this embodiment, the minimum distance between two adjacent light guiding optical film patterns 210FP is less than or equal to the size of the user's pupil. For example, the minimum distance between two adjacent light guiding optical film patterns 210FP is about 0.5 times the size of the user's pupil.

[0060] On the other hand, the user's perception of the density of the light guiding optical film pattern 210FP seen under different pupil sizes is different. When the pupil of the human eye enlarges, more light rays can be received, and the density perception brought by the light guiding optical film pattern 210FP is significantly reduced. Therefore, in the design process, by controlling the size of the light guiding optical film pattern 210FP, the harsh density perception brought by the light guiding optical film pattern 210FP can be avoided. The ratio between the size of each light guiding optical film pattern 210FP and the minimum distance between two adjacent light guiding optical film patterns 210FP is between 0.6 and 0.7, among which the ratio between the size of each light guiding optical film pattern 210FP and the minimum distance between two adjacent light guiding optical film patterns 210FP is preferably 0.6. For example, in this embodiment, under the condition that the minimum distance between two adjacent light guiding optical film patterns 210FP is 1.5 millimeters, the size of the light guiding optical film pattern 210FP may be controlled to be 1.1 millimeters or less, and in this way, a better visual perception can be provided to the user.

[0061] In this way, the video light beam IB from the first waveguide 100 enters the second plate body 210 via the light incident surface. After that, a part of the video light beam IB passes through the light guiding optical film pattern 210FP, and the other part of the video light beam IB can leave the second plate body 210 from the second surface 212S after being reflected by the light guiding optical film pattern 210FP. More specifically, in this embodiment, the ratio between the orthographic projection area of the light guiding optical film pattern 210FP on the second plate body 210 and the area of the second plate body 210 is less than 30%, whereby a better transmission field of view can be obtained. For example, the area of the light guiding optical film pattern 210FP is about 20% of the area of the second plate body 210, and the light guiding optical film pattern 210FP has a transmittance of about 50%. Therefore, the transmission field of view of the entire optical system of the head-mounted display 300 is improved to about 90%, and a good transmission field of view can be achieved.

[0062] FIG. 4A is an optical path diagram of the head-mounted display of FIG. 1A. FIG. 4B is a brightness simulation data diagram of the video light beam appearing on the head-mounted display of FIG. 1A. FIG. 4C is a brightness simulation data diagram of the video light beam appearing on the head-mounted display without the light guide film in the comparative example. Further, as shown in FIG. 4A, in this embodiment, the second waveguide 200 has a first optical region 201R and a second optical region 202R, wherein the first optical region 201R is located between the light incident surface and the second optical region 202R, and the first sawtooth structure 211ZS, the second sawtooth structure 212ZS and the second optical microstructure 220 are located within the second optical region 202R, and the second waveguide 200 further includes a light guide film GF. The light guide film GF is located on the light guiding surface GS inside the second waveguide 200, the light guiding surface GS is located within the first optical region 201R, and is parallel to the first surface 211S.

[0063] Furthermore, the fabrication of the light guide film GF can be carried out together when forming a plurality of light guiding optical film patterns 210FP of at least one optical film 210F. For example, in this embodiment, the first structural layer 211 of the second waveguide 200 further has a first plane 211PS, the second structural layer 212 further has a second plane 212PS, and while forming a plurality of light guiding optical film patterns 210FP of at least one optical film 210F, the light guide film GF is also formed on the first plane or the second plane. Subsequently, after the joining of the first structural layer 211 and the second structural layer 212, the second plane can contact the first plane to form the light guiding surface GS, and the light guide film GF can be formed thereon.

[0064] Specifically, as shown in FIG. 4A, the light guide film GF allows a part of the video light beam IB to pass through and reflects the other part of the video light beam IB, and the video light beam IB propagates in the second waveguide 200 in a total reflection manner by the light guide film GF. In this way, the uniformity of the video light beam IB entering the second waveguide 200 can be further improved.

[0065] Furthermore, as shown in FIG. 4B, when the light guide film GF is disposed, the light guide film GF can effectively increase the density of the video light beam IB. Also, when the light guide film GF is located inside the second waveguide 200 and the light guide film GF is plated on the outer surface of the second waveguide 200, its uniformity can be significantly increased and its optical efficiency can be maintained. In this way, in the head-mounted display 300, the video screen represented by the video light beam IB propagated to the user's eyes by the second waveguide 200 has good uniformity and it is difficult for defects to occur on the screen. On the contrary, as shown in FIG. 4C, when the light guide film GF is not disposed, in the head-mounted display 300, the uniformity of the video light beam IB propagated to the user's eyes by the second waveguide 200 is significantly reduced. Therefore, in the video light beam IB entering the user's eyes, there is no light in some regions. Thus, the video screen visible to the user's eyes has defects and is incomplete, which may affect the viewing quality.

[0066] The present invention has been disclosed as above based on the foregoing preferred embodiments. However, the foregoing preferred embodiments are not for limiting the present invention. Those skilled in the art can make minor changes and refinements to the present invention without departing from the technical idea and scope of the present invention. Therefore, the protection scope of the present invention is based on what is defined in the appended claims. Also, any embodiment or claims of the present invention do not need to achieve all the objects or advantages or features disclosed in the present invention. Also, a part of the abstract and the title of the invention are only for assisting in literature search and do not limit the technical scope of the present invention. Also, the terms such as "first" and "second" mentioned in this specification or claims are only for naming an element or for distinguishing other embodiments or scopes, and are not for limiting the upper or lower limits in terms of the number of elements.

Explanation of Reference Numerals

[0067] 100: First waveguide 101R: First optical region 102R: Second optical region 110 First plate body 110F: Optical film 110OS: Optical surface 111: First structural layer 111IS: First inclined surface 111LS: First connection surface 111S: First surface 111ZS: First serrated structure 112: Second structural layer 112IS: Second inclined surface 112LS: Second connection surface 112S: Second surface 112ZS: Second serrated structure 120: First optical microstructure 121: Central optical microstructure 122: Relay optical microstructure 123: Edge optical microstructure 200: Second waveguide 201R: First optical region 202R: Second optical region 210: Second plate body 210F: Optical film 210FP: Optical film pattern for light guiding 210OS: Optical surface 211: First structural layer 211IS: First inclined surface 211LS: First connection surface 211PS: First plane 211S: First surface 211ZS: First serrated structure 212: Second structural layer 212IS: Second inclined surface 212LS: Second connection surface 212ZS: Second serrated structure 212S: Second surface 212PS: Second plane 220: Second optical microstructure 300: Head-mounted display 310: Lighting system 320: Display unit D1: First direction D2: Second direction EY: Eye GF: Light guide film GS: Light guide surface IB: Image beam LS: Lens module O: Main axis OM: Mask PS: Flat plate structure ST: Stop TH: Through hole WG: Waveguide element ZS: Sawtooth structure θ: Included angle

Claims

1. A head-mounted display disposed in front of at least one eye of a user, comprising: a display unit, a first wave guide, and a second wave guide; the display unit provides an image light beam; the first wave guide is located on a propagation path of the image light beam, and the first wave guide includes a first plate body and a plurality of first optical microstructures; the plurality of first optical microstructures are located in the first plate body, and the plurality of first optical microstructures include a central optical microstructure and edge optical microstructures; the central optical microstructures are respectively located on both sides of a main axis of the image light beam; the edge optical microstructures are respectively located on both sides of the main axis of the image light beam, the central optical microstructure is closer to the main axis of the image light beam than the edge optical microstructure, after the image light beam enters the first plate body through a first surface of the first plate body, a part of the image light beam passes through the central optical microstructure, and other parts of the image light beam propagate to the corresponding edge optical microstructures via the central optical microstructure respectively, and after passing through the corresponding edge optical microstructures, leave the first plate body from a second surface of the first plate body; the second wave guide is located on a propagation path of the image light beam, the first wave guide is located between the display unit and the second wave guide, the first wave guide propagates the image light beam to the second wave guide and adjusts a shape of the image light beam, the second wave guide propagates the image light beam to at least one eye of the user, and the second wave guide includes a second plate body, a plurality of second optical microstructures, and a plurality of light guiding optical film patterns; the second plate body has a light incident surface, and the light incident surface is connected to a first surface and a second surface of the second plate body; the plurality of second optical microstructures are located in the second plate body, each of the second optical microstructures has an optical surface, and the plurality of optical surfaces of the plurality of second optical microstructures are respectively inclined with respect to the first surface of the second plate body; The plurality of light-guiding optical film patterns are located on the plurality of optical surfaces of the plurality of second optical microstructures. The plurality of light-guiding optical film patterns allow a part of the video light beam to pass through and reflect another part of the video light beam. After the video light beam enters the second plate body via the light-incident surface, a part of the video light beam passes through the plurality of light-guiding optical film patterns, and after another part of the video light beam is reflected by the plurality of light-guiding optical film patterns, it leaves the second plate body from the second surface of the second plate body. A head-mounted display.

2. The head-mounted display according to claim 1, wherein a ratio of a positive projection area of the plurality of light-guiding optical film patterns on the second plate body to an area of the second plate body is less than 30%. A head-mounted display.

3. The head-mounted display according to claim 1, wherein an included angle between the first wave guide and the second wave guide is between 90 degrees and 135 degrees. A head-mounted display.

4. The head-mounted display according to claim 1, wherein the plurality of first optical microstructures of the first wave guide are arranged along a first direction, the plurality of second optical microstructures of the second wave guide are arranged along a second direction, and the first direction is perpendicular to the second direction. A head-mounted display.

5. The head-mounted display according to claim 1, wherein each of the first optical microstructures has an optical surface, and the plurality of optical surfaces of the plurality of first optical microstructures extend away from the main axis of the video light beam and close to the second surface of the first plate body from near the main axis of the video light beam and close to the first surface of the first plate body, and are inclined with respect to the first surface of the first plate body. A head-mounted display.

6. The head-mounted display according to claim 5, wherein the first wave guide has a first optical region and a second optical region, the first optical region and the second optical region are respectively located on both sides of the main axis of the video light beam, and an inclination direction of the plurality of optical surfaces of the plurality of first optical microstructures in the first optical region and an inclination direction of the plurality of optical surfaces of the plurality of first optical microstructures in the second optical region are mirror-symmetrical. A head-mounted display.

7. The head-mounted display according to claim 5, The first waveguide has at least one optical film, the at least one optical film is located on at least one of the plurality of optical surfaces of the plurality of first optical microstructures, and the optical film allows a part of the video light beam to pass through and reflects another part of the video light beam. A head-mounted display.

8. The head-mounted display according to claim 7, A head-mounted display, wherein the reflectivity of the at least one optical film located on the central optical microstructure or the edge optical microstructure with respect to the video light beam is greater than the transmittance with respect to the video light beam.

9. The head-mounted display according to claim 7, The plurality of first optical microstructures further include a plurality of relay optical microstructures, and at least one of the relay optical microstructures exists between the central optical microstructure and the edge optical microstructure, A part of the video light beam from the central optical microstructure propagates to the corresponding edge optical microstructure after passing through the plurality of relay optical microstructures, and another part of the video light beam from the central optical microstructure is reflected by the plurality of relay optical microstructures and leaves the first plate body from the second surface of the first plate body. A head-mounted display.

10. The head-mounted display according to claim 9, A head-mounted display, wherein the reflectivity of the at least one optical film located on the plurality of relay optical microstructures with respect to the video light beam is smaller than the transmittance with respect to the video light beam.

11. The head-mounted display according to claim 5, The first plate body includes a first structural layer and a second structural layer, The first structural layer has a plurality of first inclined surfaces and a plurality of first connection surfaces, and each of the first connection surfaces is connected to different ends of the plurality of adjacent first inclined surfaces to form a first serrated structure, The second structural layer has a plurality of second inclined surfaces and a plurality of second connection surfaces, and each of the second connection surfaces is connected to different ends of the plurality of adjacent second inclined surfaces to form a second serrated structure. The plurality of second inclined surfaces correspond to the plurality of first inclined surfaces, and the plurality of second connection surfaces correspond to the plurality of first connection surfaces. Thus, the first serrated structure coincides with the second serrated structure, and the plurality of second inclined surfaces contact the plurality of first inclined surfaces to form the plurality of optical surfaces of the plurality of first optical microstructures. A head-mounted display.

12. The head-mounted display according to claim 11, wherein the first waveguide has at least one optical film, the at least one optical film is located on at least one of the plurality of first inclined surfaces of the first structural layer and the plurality of second inclined surfaces of the second structural layer, and the optical film allows some of the video light beams to pass through and reflects other portions of the video light beams. Head-mounted display.

13. The head-mounted display according to claim 1, wherein the minimum distance between two adjacent light guiding optical film patterns is smaller than the size of the user's pupil. Head-mounted display.

14. The head-mounted display according to claim 13, wherein the ratio between the size of each light guiding optical film pattern and the minimum distance between two adjacent light guiding optical film patterns is between 0.6 and 0.

7. Head-mounted display.

15. The head-mounted display according to claim 13, wherein the second plate body includes a first structural layer and a second structural layer, the first structural layer has a plurality of first inclined surfaces and a plurality of first connection surfaces, and each of the first connection surfaces is connected to different ends of the adjacent plurality of first inclined surfaces to form a first serrated structure, the second structural layer has a plurality of second inclined surfaces and a plurality of second connection surfaces, and each of the second connection surfaces is connected to different ends of the adjacent plurality of second inclined surfaces to form a second serrated structure, the plurality of second inclined surfaces correspond to the plurality of first inclined surfaces, and the plurality of second connection surfaces correspond to the plurality of first connection surfaces, whereby the first serrated structure coincides with the second serrated structure, and the plurality of second inclined surfaces contact the plurality of first inclined surfaces to form the plurality of optical surfaces of the plurality of second optical microstructures. Head-mounted display.

16. The head-mounted display according to claim 15, wherein The second waveguide has a first optical region and a second optical region. The first optical region is located between the light incident surface and the second optical region. The first serrated structure, the second serrated structure, and the plurality of second optical microstructures are located within the second optical region. The second waveguide further includes a light guiding film, and the light guiding film is located on a light guiding surface inside the second waveguide. The light guiding surface is located within the first optical region and is parallel to the first surface of the second plate body. The light guiding film allows some of the video light beams to pass through and reflects other portions of the video light beams. Also, the video light beams propagate in a total reflection manner within the second waveguide, a head-mounted display.

17. The head-mounted display according to claim 16, wherein the first structural layer further has a first plane, the second structural layer further has a second plane, and the second plane contacts the first plane to form the light guiding surface, a head-mounted display.

18. A waveguide applied to a head-mounted display, wherein the waveguide is used to receive video light beams, the waveguide includes a first plate body, a plurality of optical films, and a plurality of first optical microstructures, each of the plurality of optical films is used to allow some of the video light beams to pass through and reflect other portions of the video light beams, the plurality of first optical microstructures are located within the first plate body, and the plurality of first optical microstructures include two central optical microstructures, a plurality of relay optical microstructures, and two edge optical microstructures, the reflectivity of at least one of the plurality of optical films located on the two central optical microstructures or the two edge optical microstructures with respect to the video light beams is greater than the transmittance with respect to the video light beams, and the reflectivity of at least one other of the plurality of optical films located on the plurality of relay optical microstructures with respect to the video light beams is less than the transmittance with respect to the video light beams, the two central optical microstructures are respectively located on both sides of the main axis of the video light beams, the two edge optical microstructures are respectively located on both sides of the main axis of the video light beams, and the two central optical microstructures are closer to the main axis of the video light beams than the two edge optical microstructures. At least one of the plurality of relay optical microstructures is disposed between one of the two central optical microstructures and one of the two edge optical microstructures. After the video light beam enters the first plate body via the first surface of the first plate body, a part of the video light beam passes through the two central optical microstructures and leaves the first plate body, and another part of the video light beam is reflected by the two central optical microstructures and then propagates within the first plate body. A part of the other part of the video light beam propagates to the two edge optical microstructures and leaves the first plate body from the second surface of the first plate body, which is a waveguide.

Images