Optical system and display device

Abstract

An optical system and a display device. The optical system comprises a prism assembly, wherein the prism assembly comprises a plurality of light incident surfaces and one light exit surface, each light incident surface being configured to allow incidence of image light of one color, different light incident surfaces being configured to allow incidence of image light of different colors, and the image light of different colors being converged in the prism assembly and then exiting from the light exit surface. The number of prisms comprised in the prism assembly is less than four, and the prism assembly comprises at least a first prism and a second prism. A first surface of the first prism is disposed opposite a second surface of the second prism. A microstructure array is provided between the first surface and the second surface, and the microstructure array is configured to change the propagation direction of image light of at least one color and transmit image light of at least another color.

Description

Optical systems and display devices

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese Patent Application No. 202510230843.9, filed on February 27, 2025, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments of this disclosure relate to an optical system and a display device. Background Technology

[0004] In near-eye display devices, such as augmented reality (AR) display devices, a film prism can be used to combine blue light emitted from a blue display, red light emitted from a red display, and green light emitted from a green display to form the final visual image presented to the user. During this light-combining process, if there is a deviation, the color, brightness, and clarity of the virtual image will be affected, thus reducing the user's immersive experience. Therefore, precise control of the energy and direction of each color of light is necessary to obtain a high-quality image. Summary of the Invention

[0005] This disclosure provides an optical system and a display device.

[0006] This disclosure provides an optical system including a prism assembly. The prism assembly includes multiple incident surfaces and one exiting surface. Each incident surface is configured to receive a single color image light, and different incident surfaces are configured to receive different colors of image light. The different colors of image light converge in the prism assembly and exit from the exiting surface. The prism assembly includes fewer than four prisms, and includes at least a first prism and a second prism. A first surface of the first prism and a second surface of the second prism are disposed opposite each other. A microstructure array is disposed between the first surface and the second surface. The microstructure array is configured to change the propagation direction of at least one color image light and transmit at least another color image light.

[0007] For example, according to an embodiment of this disclosure, the microstructure array includes at least one diffraction structure, each diffraction structure being configured to diffract one color image light and transmit at least one color image light from other color image lights.

[0008] For example, according to embodiments of this disclosure, the at least one diffraction structure includes at least one of a diffraction grating and a subwavelength structure.

[0009] For example, according to an embodiment of this disclosure, the prism group includes two prisms, namely a first prism and a second prism, and the at least one diffraction structure includes a first diffraction structure and a second diffraction structure, the second diffraction structure being located between the first diffraction structure and the second surface; one of the first diffraction structure and the second diffraction structure is configured to diffract a first color image light and transmit a second color image light, and the other of the first diffraction structure and the second diffraction structure is configured to diffract a third color image light and transmit the first color image light and the second color image light.

[0010] For example, according to embodiments of this disclosure, both the first diffraction structure and the second diffraction structure include multiple microstructures, each of which includes multiple microstructure parameters. These multiple microstructure parameters include the distance between adjacent microstructures, the height of the microstructure, and the size of the microstructure in a specific direction parallel to the first surface. The values ​​of at least one microstructure parameter of the same type in the first diffraction structure and the second diffraction structure are different.

[0011] For example, according to an embodiment of this disclosure, the prism group includes two prisms, namely a first prism and a second prism, and a beam-splitting film is further disposed between the first surface and the second surface. The beam-splitting film is located between one of the first surface and the second surface and the diffraction structure. The diffraction structure is configured such that the color of the diffracted image light is different from the color of the image light reflected by the beam-splitting film, and the diffraction structure and the beam-splitting film are configured to transmit at least one light of the same color.

[0012] For example, according to an embodiment of this disclosure, one of the diffraction structure and the beam splitter is configured to change the propagation direction of the first color image light and transmit the second color image light, and the other of the diffraction structure and the beam splitter is configured to change the propagation direction of the third color image light and transmit the first color image light and the second color image light.

[0013] For example, according to an embodiment of this disclosure, the first diffraction structure and the second diffraction structure are two of three types of diffraction structures, including a first type diffraction structure, a second type diffraction structure, and a third type diffraction structure; the first type diffraction structure includes a plurality of first microstructures, the distance between adjacent first microstructures is 100-200 nanometers, the height of the first microstructure is 150-350 nanometers, and the size of the first microstructure in a specific direction parallel to the first surface is 200-250 nanometers; the first type diffraction structure is configured to diffract red image light; the second type diffraction structure includes a plurality of second microstructures. The first type of diffraction structure comprises a plurality of third microstructures, wherein the distance between adjacent second microstructures is 60–120 nm, the height of the second microstructure is 200–500 nm, and the size of the second microstructure in a specific direction parallel to the first surface is 100–150 nm. The second type of diffraction structure is configured to diffract blue image light. The third type of diffraction structure comprises a plurality of third microstructures, the distance between adjacent third microstructures is 80–160 nm, the height of the third microstructure is 200–400 nm, the size of the third microstructure in a specific direction parallel to the first surface is 150–200 nm, and the third type of diffraction structure is configured to diffract green image light.

[0014] For example, according to an embodiment of this disclosure, the diffraction structure includes one of three types of diffraction structures, namely a first type diffraction structure, a second type diffraction structure, and a third type diffraction structure; the first type diffraction structure includes a plurality of first microstructures, the distance between adjacent first microstructures is 100-200 nanometers, the height of the first microstructure is 150-350 nanometers, and the size of the first microstructure in a specific direction parallel to the first surface is 200-250 nanometers, and the first type diffraction structure is configured to diffract red image light; the second type diffraction structure includes a plurality of second microstructures, the distance between adjacent second ... The distance between the microstructures is 60–120 nm, the height of the second microstructure is 200–500 nm, and the size of the second microstructure in a specific direction parallel to the first surface is 100–150 nm. The second type of diffraction structure is configured to diffract blue image light. The third type of diffraction structure includes a plurality of third microstructures, the distance between adjacent third microstructures is 80–160 nm, the height of the third microstructure is 200–400 nm, and the size of the third microstructure in a specific direction parallel to the first surface is 150–200 nm. The third type of diffraction structure is configured to diffract green image light.

[0015] For example, according to an embodiment of this disclosure, the subwavelength structure includes a plurality of microstructures, wherein the plurality of microstructures are at least one of the plurality of first microstructures, the plurality of second microstructures, and the plurality of third microstructures, wherein the microstructures included in the subwavelength structure are inclined relative to the first surface, and the inclination angle of the microstructures relative to the first surface is 5 to 70 degrees.

[0016] For example, according to an embodiment of this disclosure, a structural substrate is disposed between the first diffraction structure and the second diffraction structure, both the first diffraction structure and the second diffraction structure are disposed on the structural substrate, the structural substrate is parallel to the first surface, and the thickness of the structural substrate is 0.1 to 2 mm.

[0017] For example, according to an embodiment of this disclosure, the plurality of light-incident surfaces include a first light-incident surface, a second light-incident surface, and a third light-incident surface. The first light-incident surface is parallel to the light-out surface, the second light-incident surface is parallel to the third light-incident surface and is located on both sides of the first surface, and the included angle between the first surface and the second and third light-incident surfaces is less than 90 degrees.

[0018] For example, according to an embodiment of this disclosure, the emission angle of the image light emitted from the light-emitting surface is 70 to 110 degrees.

[0019] Another embodiment of this disclosure provides a display device, including a plurality of display screens and any of the above-described optical systems, wherein the plurality of display screens are arranged in a one-to-one correspondence with the plurality of light incident surfaces, and different display screens emit image light of different colors. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0021] Figure 1 is a schematic diagram of a prism assembly combining light from images of different colors.

[0022] Figures 2 and 3 are schematic diagrams of partial cross-sectional structures of optical systems provided according to different examples of embodiments of the present disclosure.

[0023] Figure 4 is a schematic diagram of the optical system shown in Figure 2 in one example.

[0024] Figure 5 is a partial enlarged view of the first and second diffraction structures shown in Figure 4.

[0025] Figures 6 to 8 are schematic diagrams of partial cross-sectional structures of microstructures in subwavelength structures provided according to different examples of embodiments of the present disclosure.

[0026] Figure 9 is a schematic diagram of the optical system shown in Figure 2 in another example.

[0027] Figure 10 is a partial structural schematic diagram of a display device according to another embodiment of the present disclosure. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the described embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0029] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0030] Unless otherwise specified in the following embodiments of this disclosure, the quantity of a component is implied to mean that the component may be one or more, or can be understood as at least one. "At least one" means one or more, and "more" means at least two.

[0031] Figure 1 is a schematic diagram of a prism assembly combining light from images of different colors.

[0032] As shown in Figure 1, the prism assembly 10 includes four prisms, such as prism 11, prism 12, prism 13 and prism 14; prism 11 includes a light-incident surface facing the red display screen 21, a first surface 01 attached to prism 12 and a second surface 02 attached to prism 14; prism 12 includes a light-incident surface facing the green display screen 22, a third surface 03 attached to prism 11 and a fourth surface 04 attached to prism 13; prism 13 includes a light-incident surface facing the blue display screen 23, a fifth surface 05 attached to prism 12 and a sixth surface 06 attached to prism 14; prism 14 includes a light-emitting surface, a seventh surface 07 attached to prism 11 and an eighth surface 08 attached to prism 13.

[0033] As shown in Figure 1, a coating is applied between the first surface 01 and the third surface 03, and between the sixth surface 06 and the eighth surface 08, to reflect red image light and transmit blue and green image light; a coating is applied between the fifth surface 05 and the fourth surface 04, and between the second surface 02 and the seventh surface 07, to reflect blue image light and transmit red and green image light. Ultimately, the red, green, and blue image lights converge at the light-emitting surface to form a combined light source, thus forming a complete color light source.

[0034] In their research, the inventors of this application discovered that the prism assembly shown in Figure 1 presents certain challenges in terms of both assembly and coating direction. For example, assembling the four prisms requires precise control of positional accuracy, such as accurately controlling the position and orientation of each prism to ensure the accuracy of the optical path. Specifically, the inclined surfaces of prisms 11 and 12 need to be on the same plane, as do the inclined surfaces of prisms 13 and 14. Furthermore, the inclined surfaces of prisms 11 and 14, and prisms 12 and 13, need to be on the same plane. Even minute errors during prism assembly can lead to optical path deviations, thereby affecting the function of the entire optical system. Therefore, the equipment used for assembling the prisms must possess high-precision positioning and adjustment capabilities to accurately place the prisms in their predetermined positions. For example, depending on the beam splitting requirements of each prism, different types of coatings need to be deposited on the surface of the prism, such as anti-reflection coatings, high-reflection coatings, beam splitting coatings, and other complex coatings, in order to reflect and transmit the three colors of image light, thereby achieving beam combining. Since multiple prisms are involved, the design difficulty of the coating will be increased, and some optical effects will be sacrificed.

[0035] This disclosure provides an optical system and a display device. The optical system includes a prism assembly. The prism assembly includes multiple incident surfaces and an exiting surface. Each incident surface is configured to receive a single color image light, and different incident surfaces are configured to receive different colors of image light. The different colors of image light converge in the prism assembly and exit from one exiting surface. The prism assembly includes fewer than four prisms, and the prism assembly includes at least a first prism and a second prism. A first surface of the first prism and a second surface of the second prism are disposed opposite each other. A microstructure array is disposed between the first and second surfaces. The microstructure array is configured to change the propagation direction of at least one color image light and transmit at least another color image light.

[0036] The optical system provided in this disclosure, by setting a microstructure array between the first prism and the second prism to change the propagation direction of at least one color image light, can reduce the number of prisms included in the prism group and save at least part of the coating process, thereby reducing the assembly difficulty of the prisms and the coating difficulty, optimizing the performance of the optical system to improve the display effect.

[0037] The optical system and display device provided in the embodiments of this disclosure are described below with reference to the accompanying drawings.

[0038] Figures 2 and 3 are schematic diagrams of partial cross-sectional structures of optical systems provided according to different examples of embodiments of the present disclosure.

[0039] As shown in Figure 2, the optical system includes a prism group 100, which includes multiple light-incident surfaces and a light-outceasing surface 104. Each light-incident surface is configured to receive a color image light, and different light-incident surfaces are configured to receive different color image lights. The different color image lights converge in the prism group 100 and then exit from the same light-outceasing surface 104.

[0040] In some examples, as shown in FIG2, multiple light-incident surfaces include a first light-incident surface 101, a second light-incident surface 102, and a third light-incident surface 103. For example, the first light-incident surface 101 is configured to incident a second color image light 402, the second light-incident surface 102 is configured to incident a third color image light 403, and the third light-incident surface 103 is configured to incident a first color image light 401. The first color image light 401, the second color image light 402, and the third color image light 403 can be blue image light, green image light, and red image light, respectively. The embodiments disclosed herein are not limited thereto, and the colors of the first color image light 401, the second color image light 402, and the third color image light 403 can be interchanged.

[0041] Figure 2 schematically shows multiple light-incident surfaces, including three light-incident surfaces, but is not limited to this; multiple light-incident surfaces may also include two light-incident surfaces.

[0042] For example, as shown in Figure 2, the first color image light 401, the second color image light 402, and the third color image light 403 converge in the prism group 100 and are emitted from the same light-emitting surface 104. The prism group 100 realizes the light combining effect of different color image lights.

[0043] As shown in Figure 2, the prism group 100 includes fewer than four prisms. The prism group 100 includes at least a first prism 110 and a second prism 120. The first surface 111 of the first prism 110 and the second surface 112 of the second prism 120 are disposed opposite to each other. A microstructure array 200 is disposed between the first surface 111 and the second surface 112. The microstructure array 200 is configured to change the propagation direction of at least one color image light and transmit at least another color image light.

[0044] Compared to the optical system shown in Figure 1, which uses four prisms and coats the surfaces of the prisms to achieve the splitting of different color image light, the optical system provided in this embodiment reduces the number of prisms in the prism group 100 by setting a microstructure array 200 between the first prism 110 and the second prism 120 to change the propagation direction of at least one color image light. This reduces the difficulty of prism assembly, as it eliminates the need for precise assembly of prisms with different surfaces that need to be located on the same plane as shown in Figure 1. Furthermore, replacing at least part of the coating with the microstructure array 200 helps reduce the coating difficulty, thereby optimizing the performance of the optical system and improving the display effect.

[0045] In some examples, as shown in Figure 2, the prism assembly 100 includes two prisms, namely a first prism 110 and a second prism 120. For example, the first surface 111 is parallel to the second surface 112, and the microstructure array 200 can be pressed between the first surface 111 and the second surface 112.

[0046] Compared to the optical system with four prisms shown in Figure 1, the prism assembly 100 provided in this disclosure has only two prisms, which can significantly reduce the difficulty of assembling and fitting the prisms.

[0047] For example, as shown in Figure 3, the prism assembly 100 further includes a third prism 130, which includes a third surface 113. The third surface 113 is disposed opposite to the first surface 111. A portion of the microstructure array 200 is disposed between the first surface 111 and the second surface 112, and another portion is disposed between the first surface 111 and the third surface 113. For example, the third surface 113 and the second surface 112 are located on the same surface. For example, the surface 115 of the third prism 130 is disposed opposite to the surface 114 of the second prism 120, such as being in contact with each other.

[0048] Compared to the optical system with four prisms shown in Figure 1, the optical system provided in this embodiment reduces the assembly difficulty of prisms by setting the number of prisms included in the prism group 100 to less than four, thus eliminating the need for precise assembly of prisms on different surfaces that need to be located on the same plane as shown in Figure 1.

[0049] With the arrow pointing to the right in the X direction as shown in Figure 3, Figure 3 schematically shows that there are two prisms on the right side of the microstructure array 200 and one prism on the left side of the microstructure array 200, but it is not limited to this; it is also possible that there is one prism on the right side of the microstructure array 200 and two prisms on the left side of the microstructure array 200.

[0050] In some examples, as shown in Figure 2, the first light-incident surface 101 is parallel to the light-outcident surface 104, the second light-incident surface 102 and the third light-incident surface 103 are parallel and located on both sides of the first surface 111, and the included angle between the first surface 111 and the second light-incident surface 102 and the third light-incident surface 103 is less than 90 degrees.

[0051] By setting the relative positions of the light-incident surfaces 104, light-excising surfaces 104, and the second surface 112 in the prism assembly 100, the splitting and combining of light from different color images can be achieved.

[0052] For example, as shown in Figure 2, the light-incident surface of the microstructure array 200 is perpendicular to the XY plane, and the multiple light-incident surfaces and the light-exit surface 104 of the prism group 100 are also perpendicular to the XY plane. For example, the second light-incident surface 102 and the third light-incident surface 103 both intersect with the first light-incident surface 101, or both are perpendicular to the first light-incident surface 101. For example, the angle between the second light-incident surface 102 and the first surface 111 is 45 degrees, and the angle between the third light-incident surface 103 and the second surface 112 is 45 degrees.

[0053] For example, as shown in Figure 2, taking the first color image light 401 perpendicularly incident on the third incident surface 103 as an example, that is, before the first color image light 401 is incident on the microstructure array 200, it is image light propagating in a direction parallel to the Y direction. After the first color image light 401 passes through the microstructure array 200, its propagation direction changes. It is no longer parallel to the Y direction, but propagates towards the light-emitting surface 104 that intersects with the third incident surface 103. Thus, the microstructure array 200 changes the propagation direction of the first color image light 401.

[0054] For example, as shown in Figure 2, taking the third color image light 403 incident perpendicularly onto the second incident surface 102 as an example, the third color image light 403 is an image light propagating in a direction parallel to the Y direction before it is incident onto the microstructure array 200. After passing through the microstructure array 200, the propagation direction of the third color image light 403 changes. It is no longer parallel to the Y direction, but propagates towards the light exiting surface 104 that intersects with the second incident surface 102. Thus, the microstructure array 200 changes the propagation direction of the third color image light 403.

[0055] For example, as shown in Figure 2, taking the second color image light 402 perpendicular to the first incident light surface 101 as an example, that is, before the second color image light 402 is incident on the microstructure array 200, it is image light propagating in a direction parallel to the X direction. After the second color image light 402 passes through the microstructure array 200, its propagation direction does not change, and it propagates towards the light exiting surface 104 parallel to the first incident light surface 101. Thus, the microstructure array 200 does not change the propagation direction of the second color image light 402, that is, the microstructure array 200 transmits the second color image light 402.

[0056] The optical system provided in this disclosure uses a microstructure array 200 to replace at least part of the coating layer shown in FIG1, which can effectively reduce the coating difficulty.

[0057] Figure 2 schematically shows that the microstructure array 200 transmits the second color image light 402 while changing the propagation direction of the first color image light 401 and the third color image light 403. However, it is not limited to this. The microstructure array 200 may change only the propagation direction of the first color image light 401 or only the propagation direction of the third color image light 403.

[0058] In some examples, as shown in Figure 2, the microstructure array 200 includes at least one diffraction structure, each diffraction structure being configured to diffract one color image light and transmit at least one color image light from other color image lights.

[0059] By configuring the microstructure array 200 to include at least one diffraction structure, it is possible to diffract at least one color image light so that the at least one color image light propagates toward the light-emitting surface 104, while transmitting at least one color image light from other color image lights so that at least one color image light from other color image lights also propagates toward the light-emitting surface 104, thereby achieving a better light combining effect.

[0060] For example, as shown in FIG2, in the first example, the microstructure array 200 includes a diffraction structure configured to diffract a first color image light 401 so that the first color image light 401 propagates toward the light-emitting surface 104, and the diffraction structure is configured to transmit a second color image light 402.

[0061] For example, as shown in FIG2, in the second example, the microstructure array 200 includes a diffraction structure configured to diffract a third color image light 403 so that the third color image light 403 propagates toward the light-emitting surface 104, and the diffraction structure is configured to transmit a second color image light 402 and a first color image light 401 whose propagation direction has been changed.

[0062] For example, as shown in Figure 2, the microstructure array 200 may include only one diffraction structure in the first example above, or only one diffraction structure in the second example above, or both diffraction structures in the first and second examples above (i.e., the first and second diffraction structures shown in Figure 4).

[0063] In some examples, as shown in Figure 2, at least one diffraction structure includes at least one of a diffraction grating and a subwavelength structure. Both the diffraction grating and the subwavelength structure diffract light of a specific wavelength incident upon them to change the propagation direction of that light.

[0064] For example, as shown in Figure 2, the microstructure array 200 may include a diffraction grating, or two diffraction gratings, or a subwavelength structure, or two subwavelength structures, or a diffraction grating and a subwavelength structure.

[0065] Figure 2 shows a magnified view of the microstructure array 200 to clearly illustrate its size. The size of the microstructure array 200 is very small compared to the sizes of the first prism 110 and the second prism 120. When the microstructure array 200 is located between the first surface 111 and the second surface 112, there may be virtually no gap between the first surface 111 and the second surface 112, as they may be essentially bonded together. Alternatively, a gap may exist between the first surface 111 and the second surface 112, which could include air or be filled with optical adhesive.

[0066] Figure 2 schematically shows that the light emission ranges of the first color image light 401, the second color image light 402, and the third color image light 403 at the light emission surface 104 are completely consistent, but it is not limited to this. The light emission ranges of the above three color image lights at the light emission surface 104 may also have some deviation.

[0067] Figure 4 is a schematic diagram of the optical system shown in Figure 2 in one example. Figure 5 is a partially enlarged view of the first and second diffraction structures shown in Figure 4.

[0068] In some examples, as shown in Figures 4 and 5, at least one diffraction structure includes a first diffraction structure 210 and a second diffraction structure 220, the second diffraction structure 220 being located between the first diffraction structure 210 and the second surface 112; one of the first diffraction structure 210 and the second diffraction structure 220 is configured to diffract a first color image light 401 and transmit a second color image light 402, and the other of the first diffraction structure 210 and the second diffraction structure 220 is configured to diffract a third color image light 403 and transmit the first color image light 401 and the second color image light 402.

[0069] By configuring the microstructure array 200 to include a first diffraction structure 210 and a second diffraction structure 220, each diffraction structure can diffract a color image light, thereby avoiding fluctuations in the spectral splitting effect of the prism caused by factors such as coating quality, film inhomogeneity, and assembly misalignment, which is beneficial for accurately separating light of a specific wavelength.

[0070] For example, as shown in Figure 4, the first color image light 401 can be blue image light, the second color image light 402 can be green image light, and the third color image light 403 can be red image light. For example, the wavelength of the blue image light can be any value from 350 to 495 nanometers, or can include any smaller wavelength band from 350 to 495 nanometers; the wavelength of the green image light can be any value from 496 to 570 nanometers, or can include any smaller wavelength band from 496 to 570 nanometers; the wavelength of the red image light can be any value from 571 to 750 nanometers, or can include any smaller wavelength band from 571 to 750 nanometers.

[0071] By designing the second color image light transmitted through both the first diffraction structure 210 and the second diffraction structure 220 to be green light with strong energy, even if the green light is lost when passing through the diffraction structure, the impact on the image light after light combination is small.

[0072] The embodiments disclosed herein are not limited thereto, and the colors of the first color image light, the second color image light, and the third color image light can be interchanged.

[0073] For example, as shown in Figure 4, the second diffraction structure 220 is configured to diffract blue image light and transmit green image light, and the first diffraction structure 210 is configured to diffract red image light and transmit blue and green image light, so as to achieve the final emission of each color image light from the light-emitting surface 104.

[0074] For example, taking the direction indicated by the arrow in the X direction in Figure 4 as right and the direction indicated by the arrow in the Y direction as upward, the first surface 111 and the second surface 112 in the prism assembly 100 are both tilted along the lower right corner, and the first diffraction structure 210 and the second diffraction structure 220 are both tilted along the lower right corner. After the blue image light enters the second diffraction structure 220 from the upper side, the second diffraction structure 220 changes the propagation direction of the blue image light so that it propagates to the left side of the second diffraction structure 220, and after being transmitted through the first diffraction structure 210, it exits from the light-emitting surface 104. At this time, the second diffraction... The first diffraction structure 220 effectively transmits blue image light. When red image light enters the first diffraction structure 210 from below, the first diffraction structure 210 changes the propagation direction of the red image light, causing it to propagate to the left of the first diffraction structure 210 to the light-emitting surface 104. In this case, the first diffraction structure 210 effectively reflects the red image light. When green image light enters the first diffraction structure 210 and the second diffraction structure 220 from the right, neither diffraction structure changes the propagation direction of the green image light, allowing it to be transmitted to the light-emitting surface 104. Therefore, one of the first diffraction structure 210 and the second diffraction structure 220 effectively reflects one specific color of image light, while the other effectively transmits another specific color of image light.

[0075] Of course, the embodiments disclosed herein are not limited to this. For example, the tilting direction of the first diffraction structure 210 and the second diffraction structure 220 can be replaced with tilting towards the lower left corner; the incident surfaces of the blue image light, the red image light and the green image light can also be interchanged.

[0076] For example, in other examples, the first diffraction structure 210 can be tilted to the lower left. After the blue image light is incident on the second diffraction structure 220 from the upper side, the second diffraction structure 220 changes the propagation direction of the blue image light so that it propagates to the left side of the second diffraction structure 220. At this time, the second diffraction structure 220 is equivalent to reflecting the blue image light. After the red image light is incident on the second diffraction structure 220 from the lower side of the first diffraction structure 210, the first diffraction structure 210 changes the propagation direction of the red image light so that it propagates to the left side of the first diffraction structure 210 to the light-emitting surface 104. At this time, the first diffraction structure 210 is equivalent to transmitting the red image light.

[0077] In the different examples above, whether the diffraction structure acts as a reflection or transmission mechanism for blue image light can be determined by selecting specific parameters such as the material, the width, spacing, and height of the microstructures included in the diffraction structure. Similarly, whether the diffraction structure acts as a reflection or transmission mechanism for red image light can also be determined by selecting specific parameters such as the material, the width, spacing, and height of the microstructures included in the diffraction structure.

[0078] In some examples, as shown in Figures 4 and 5, the first diffraction structure 210 and the second diffraction structure 220 are two of three types of diffraction structures, including the first type of diffraction structure, the second type of diffraction structure and the third type of diffraction structure.

[0079] In some examples, as shown in Figures 4 and 5, the first type of diffraction structure includes multiple first microstructures 201. The distance between adjacent first microstructures 201 is 100–200 nanometers, the height of the first microstructure 201 is 150–350 nanometers, and the size of the first microstructure 201 in a specific direction parallel to the first surface 111 is 200–250 nanometers. The first type of diffraction structure is configured to diffract red image light; at this time, the first type of diffraction structure transmits blue and green image light. For example, by selecting the above-mentioned microstructure parameters and materials of the first microstructure 201, the first type of diffraction structure can achieve a function equivalent to transmission or reflection of red image light.

[0080] In some examples, as shown in Figures 4 and 5, the second type of diffraction structure includes multiple second microstructures 202. The distance between adjacent second microstructures 202 is 60–120 nm, the height of the second microstructure 202 is 200–500 nm, and the size of the second microstructure 202 in a specific direction parallel to the first surface 111 is 100–150 nm. The second type of diffraction structure is configured to diffract blue image light; in this case, the first type of diffraction structure transmits red and green image light. For example, by selecting the above-mentioned microstructure parameters and materials of the second microstructure 202, the second type of diffraction structure can achieve a function equivalent to transmission or reflection of blue image light.

[0081] In some examples, the third-type diffraction structure comprises multiple third microstructures, with a distance of 80–160 nm between adjacent third microstructures, a height of 200–400 nm for each third microstructure, and a dimension of 150–200 nm for each third microstructure in a specific direction parallel to the first surface. The third-type diffraction structure is configured to diffract green image light; in this case, the third-type diffraction structure transmits red and blue image light. For example, by selecting the aforementioned microstructure parameters and materials of the third microstructure, the third-type diffraction structure can be made to function as either a transmitter or a reflector of the green image light.

[0082] By setting the first diffraction structure 210 and the second diffraction structure 220 to any two of the three different types of diffraction structures used for diffracting three different colors of image light, the first diffraction structure 210 and the second diffraction structure 220 can diffract different colors of image light respectively.

[0083] Figures 4 and 5 schematically show that the first diffraction structure 210 is a first type of diffraction structure and the second diffraction structure 220 is a second type of diffraction structure, but are not limited thereto. One of the first diffraction structure 210 and the second diffraction structure 220 can be a first type of diffraction structure and the other can be a third type of diffraction structure; or one of the first diffraction structure 210 and the second diffraction structure 220 can be a second type of diffraction structure and the other can be a third type of diffraction structure.

[0084] For example, as shown in Figures 4 and 5, the distance between adjacent first microstructures 201 is 120 nanometers or 180 nanometers, the height of the first microstructure 201 is 200 nanometers or 300 nanometers, and the dimension of the first microstructure 201 in a specific direction parallel to the first surface 111 is 210 nanometers or 230 nanometers. For example, the distance between adjacent first microstructures 201 is 120–180 nanometers, the height of the first microstructure 201 is 200–300 nanometers, and the dimension of the first microstructure 201 in a specific direction parallel to the first surface 111 is 210–230 nanometers. For example, the distance between adjacent first microstructures 201 is 130–170 nanometers, the height of the first microstructure 201 is 180–250 nanometers, and the dimension of the first microstructure 201 in a specific direction parallel to the first surface 111 is 220–240 nanometers. This embodiment of the disclosure will not list the specific numerical ranges of the distance between adjacent first microstructures 201, the height of the first microstructure 201, and the size of the first microstructure 201 in a specific direction parallel to the first surface 111. The distance between adjacent first microstructures 201 can be any value between 120 and 180 nanometers, the height of the first microstructure 201 can be any value between 200 and 300 nanometers, and the size of the first microstructure 201 in a specific direction parallel to the first surface 111 can be any value between 210 and 230 nanometers.

[0085] For example, as shown in Figures 4 and 5, the distance between adjacent second microstructures 202 is 60 nanometers or 120 nanometers, the height of the second microstructure 202 is 200 nanometers or 500 nanometers, and the dimension of the second microstructure 202 in a specific direction parallel to the first surface 111 is 100 nanometers or 150 nanometers. For example, the distance between adjacent second microstructures 202 is 80–100 nanometers, the height of the second microstructure 202 is 250–400 nanometers, and the dimension of the second microstructure 202 in a specific direction parallel to the first surface 111 is 120–140 nanometers. For example, the distance between adjacent second microstructures 202 is 90–100 nanometers, the height of the second microstructure 202 is 300–450 nanometers, and the dimension of the second microstructure 202 in a specific direction parallel to the first surface 111 is 110–130 nanometers. This embodiment of the disclosure will not list the specific numerical ranges of the distance between adjacent second microstructures 202, the height of the second microstructure 202, and the size of the second microstructure 202 in a specific direction parallel to the first surface 111. The distance between adjacent second microstructures 202 can be any value between 60 and 120 nanometers, the height of the second microstructure 202 can be any value between 200 and 500 nanometers, and the size of the second microstructure 202 in a specific direction parallel to the first surface 111 can be any value between 100 and 150 nanometers.

[0086] For example, as shown in Figures 4 and 5, the distance between adjacent third microstructures is 80 nm or 160 nm, the height of the third microstructure is 200 nm or 400 nm, and the size of the third microstructure in a specific direction parallel to the first surface 111 is 150 nm or 200 nm. For example, the distance between adjacent third microstructures is 100–150 nm, the height of the third microstructure is 250–300 nm, and the size of the third microstructure in a specific direction parallel to the first surface 111 is 160–180 nm. For example, the distance between adjacent third microstructures is 90–120 nm, the height of the third microstructure is 230–350 nm, and the size of the third microstructure in a specific direction parallel to the first surface 111 is 170–190 nm. This embodiment of the disclosure will not list the distance between adjacent third microstructures, the height of the third microstructure, and the size of the third microstructure in a specific direction parallel to the first surface 111. The distance between adjacent third microstructures can be any value between 80 and 160 nanometers, the height of the third microstructure can be any value between 200 and 400 nanometers, and the size of the third microstructure in a specific direction parallel to the first surface 111 can be any value between 150 and 200 nanometers.

[0087] For example, the different types of diffraction structures mentioned above can be diffraction gratings or subwavelength structures.

[0088] For example, as shown in Figure 5, when any of the above types of diffraction structures is a diffraction grating, the diffraction grating includes multiple microstructures that are multiple strip structures extending in a direction perpendicular to the UV plane, such as multiple strip structures arranged in the V direction. The size of the microstructure in a specific direction parallel to the first surface 111 can refer to the width w of the strip structure, that is, the size of the strip structure perpendicular to its extension direction. For example, the width of each strip structure at each position can be equal. The distance between adjacent microstructures can refer to the distance s between adjacent strip structures. The height of the microstructure can refer to the size h of the microstructure in the direction perpendicular to the first surface 111.

[0089] For example, different microstructures in a diffraction grating have exactly the same parameters such as width, height, and length, and multiple microstructures are evenly arranged.

[0090] For example, when any of the above-mentioned diffraction structures is a subwavelength structure, the multiple microstructures included in the subwavelength structure can be multiple structures distributed in two dimensions on a plane perpendicular to the U direction. The shapes of each microstructure can be columnar, conical, stepped, etc. Figure 5 illustrates this with a rectangular cross-section of the microstructure cut by the UV plane, indicating that the microstructure is a columnar structure. The dimension of the microstructure in a specific direction parallel to the first surface 111 can refer to the maximum dimension of the microstructure in that direction, such as w. The distance between adjacent microstructures can refer to the distance s between adjacent microstructures, such as the distance between adjacent microstructures arranged in the V direction. The height of the microstructure can refer to the dimension h of the microstructure in the direction perpendicular to the first surface 111.

[0091] For example, the parameters of different microstructures in the subwavelength structure can be the same or different. For example, the height of different microstructures can be the same or different. For example, the maximum size of different microstructures in the direction parallel to the first surface 111 can be the same or different. For example, along a certain direction, the microstructures can be arranged at equal intervals or at unequal intervals.

[0092] For example, the aforementioned subwavelength structure refers to a structure whose microstructural parameters (such as period, width, height, etc.) are smaller than the wavelength of light in the specific band it affects. These microstructures can be nanometer-sized to influence electromagnetic waves passing through or propagating in their vicinity. By utilizing subwavelength scaling effects, at least one of the phase, amplitude, and polarization of light can be modulated to achieve precise wavelength separation, such as diffracting one color image light while transmitting other color image light.

[0093] For example, in one embodiment of this disclosure, by designing the microstructure parameters, the phase of a specific wavelength band can be modulated to control the deflection direction of light in that specific wavelength band. For example, in one embodiment of this disclosure, by designing the microstructure parameters, the phase and amplitude of a specific wavelength band can be modulated to achieve diffraction of light in that specific wavelength band. For example, in another embodiment of this disclosure, by designing the microstructure parameters, the phase, amplitude, and polarization of a specific wavelength band can all be modulated to achieve diffraction of light in that specific wavelength band.

[0094] In some examples, as shown in Figures 4 and 5, both the first diffraction structure 210 and the second diffraction structure 220 include a plurality of microstructures 2000. The plurality of microstructures 2000 include a plurality of microstructure parameters, including the distance between adjacent microstructures 2000, the height of a microstructure 2000, and the size of a microstructure 2000 in a specific direction parallel to the first surface 111. The values ​​of at least one microstructure parameter of the same type in the first diffraction structure 210 and the second diffraction structure 220 are different.

[0095] The distance between adjacent microstructures, the height of the microstructures, and the dimensions of the microstructures in a specific direction parallel to the first surface 111 can be the same as the corresponding microstructure parameters in the first microstructure 201, the second microstructure 202, and the third microstructure, and will not be repeated here.

[0096] The difference in the values ​​of at least one type of microstructure parameter of the same type in the first diffraction structure 210 and the second diffraction structure 220 may refer to the following: the distance between adjacent microstructures 2000 in the first diffraction structure 210 is different from the distance between adjacent microstructures 2000 in the second diffraction structure 220; and / or the height of microstructures 2000 in the first diffraction structure 210 is different from the height of microstructures 2000 in the second diffraction structure 220; and / or the width of microstructures 2000 in the first diffraction structure 210 is different from the width of microstructures 2000 in the second diffraction structure 220.

[0097] By setting the values ​​of at least one type of microstructure parameter of the same type in the first diffraction structure 210 and the second diffraction structure 220 to be different, the first diffraction structure 210 and the second color structure can diffract different colors of image light.

[0098] For example, as shown in Figures 4 and 5, the materials of the microstructure can include one or more inorganic compounds, such as silicon (Si), germanium (Ge), titanium dioxide (TiO2), gallium nitride (GaN), hafnium dioxide (HfO2), tantalum pentoxide (Ta2O5), indium tin oxide (ITO), aluminum-doped zinc oxide (Al:ZnO, AZO), gallium-doped zinc oxide (Ga:ZnO, GZO), magnesium fluoride (MgF2), silicon nitride (Si3N4), silicon dioxide (SiO2), and aluminum oxide (Al2O3). For example, the materials of the microstructure can also include one or more metallic materials, such as aluminum (Al), silver (Ag), barium fluoride (BaF2), and zinc selenide (ZnSe).

[0099] For example, as shown in Figures 4 and 5, the materials of the first diffraction structure 210 and the second diffraction structure 220 can be the same or different. For example, the materials of the first diffraction structure 210 and the second diffraction structure 220 may differ from the material of the prism. For example, the microstructure material can be a metallic material. By setting a small distance between adjacent microstructures and a small height for each microstructure, the microstructure can achieve a reflective effect on light of a specific wavelength; simultaneously, by adjusting some microstructure parameters, it can achieve a transmission effect on light of other wavelengths. For example, the microstructure material can be an inorganic compound. By adjusting the microstructure parameters, the microstructure can achieve a transmission effect on light of a specific wavelength.

[0100] In some examples, as shown in Figures 4 and 5, a structural substrate 230 is also included between the first diffraction structure 210 and the second diffraction structure 220. Both the first diffraction structure 210 and the second diffraction structure 220 are disposed on the structural substrate 230, which is parallel to the first surface 111 and has a thickness of 0.1 to 2 mm.

[0101] By setting the thickness range of the structural substrate 230, the structural substrate 230 can be made as thin as possible while ensuring that it can support the first diffraction structure 210 and the second diffraction structure 220, so as to reduce the size and weight of the prism assembly 100.

[0102] For example, as shown in Figure 5, the thickness of the structural substrate 230 can refer to the dimension of the structural substrate 230 in the U direction, such as 0.2 to 1 mm, or 0.5 to 1.5 mm, or 0.3 to 0.7 mm, etc. In this embodiment, the thickness of the structural substrate 230 will not be listed one by one. The thickness of the structural substrate 230 can be any value between 0.1 and 2 mm.

[0103] For example, as shown in Figure 5, the material of the structural substrate 230 may include at least one of quartz glass, single-crystal silicon, silicon nitride, and gallium arsenide. For example, the structural substrate 230 may include a single film layer or multiple film layers.

[0104] Taking the first diffraction structure 210 and the second diffraction structure 220 shown in Figure 5 as examples, both of which are subwavelength structures, Figure 5 schematically shows that: multiple microstructures in the first diffraction structure 210 have the same height, the same size in the V direction, and are arranged at equal intervals; multiple microstructures in the second diffraction structure 220 have the same height, the same size in the V direction, and are arranged at equal intervals.

[0105] Figure 4 schematically shows that both the first diffraction structure 210 and the second diffraction structure 220 are fabricated on the structural substrate 230, and the first diffraction structure 210, the second diffraction structure 220, and the structural substrate 230 are pressed between the first surface 111 and the second surface 112. However, it is not limited to this. At least one of the first diffraction structure 210 and the second diffraction structure 220 can be formed on the surface of the prism, or the first diffraction structure 210 and / or the second diffraction structure 220 can be patterned in the base film layer after forming a base film layer on the surface of the prism.

[0106] Figures 6 to 8 are schematic diagrams of partial cross-sectional structures of microstructures in subwavelength structures provided according to different examples of embodiments of the present disclosure.

[0107] For example, as shown in Figure 6, both the first diffraction structure 210 and the second diffraction structure 220 are subwavelength structures. The multiple microstructures 2000 in the first diffraction structure 210 can have different heights, and the multiple microstructures 2000 in the second diffraction structure 220 can have different heights.

[0108] In some examples, as shown in Figures 7 and 8, the subwavelength structure includes multiple microstructures 2000, which are at least one of multiple first microstructures 201, multiple second microstructures 202, and multiple third microstructures. The microstructures 2000 included in the subwavelength structure are inclined relative to the first surface 111, such as a surface perpendicular to the U direction, and the inclination angle of the microstructures 2000 relative to the first surface 111 is 5 to 70 degrees.

[0109] By setting the microstructure 2000 in the subwavelength structure to be tilted relative to the first surface 111, it is beneficial to reduce the number of diffraction orders during diffraction and improve diffraction efficiency.

[0110] For example, as shown in Figures 7 and 8, the microstructure 2000 is tilted relative to the structural substrate 230, and the tilt angle θ can be in the range of 5 to 70 degrees.

[0111] In the UV surface shown in Figures 7 and 8, the extension direction of the microstructure 2000 is no longer along the direction perpendicular to the main surface of the structural substrate 230, such as the U direction, as shown in Figures 5 and 6. Instead, it extends along a direction with a certain angle to the U direction. This can be referred to as the microstructure being tilted.

[0112] For example, as shown in Figures 7 and 8, the tilt angle θ can be 5 degrees or 70 degrees. For example, the range of the tilt angle θ can be 10 to 30 degrees. For example, the range of the tilt angle θ can be 45 to 60 degrees. For example, the range of the tilt angle θ can be 20 to 50 degrees. This disclosure embodiment will not list all the ranges of the tilt angle θ; the tilt angle θ can be any angle from 5 to 70 degrees.

[0113] For example, as shown in Figure 7, the multiple microstructures 2000 in the first diffraction structure 210 can be tilted in the same direction at the same angle, and the multiple microstructures 2000 in the second diffraction structure 220 can also be tilted in the same direction at the same angle, and both the microstructures 2000 in the first diffraction structure 210 and the microstructures 2000 in the second diffraction structure 220 are tilted in the same direction. For example, the tilt angles of the multiple microstructures 2000 in the first diffraction structure 210 and the multiple microstructures 2000 in the second diffraction structure 220 can be the same or different.

[0114] The embodiments disclosed herein are not limited thereto. For example, the plurality of microstructures 2000 in the first diffraction structure 210 and the plurality of microstructures 2000 in the second diffraction structure 220 may be tilted in different directions.

[0115] For example, as shown in Figure 8, a portion of the microstructures 2000 in the first diffraction structure 210 can be tilted by the same angle in one direction, while another portion of the microstructures 2000 in the first diffraction structure 210 can be tilted by the same angle in another direction; similarly, a portion of the microstructures 2000 in the second diffraction structure 220 can be tilted by the same angle in one direction, while another portion of the microstructures 2000 in the second diffraction structure 220 can be tilted by the same angle in another direction. For instance, the tilt angles of the multiple microstructures 2000 in the first diffraction structure 210 and the multiple microstructures 2000 in the second diffraction structure 220 can be the same or different.

[0116] For example, as shown in Figure 8, the plurality of microstructures 2000 in the first diffraction structure 210 can be symmetrically distributed with respect to a centerline extending along the U direction, and the plurality of microstructures 2000 in the second diffraction structure 220 can be symmetrically distributed with respect to a centerline extending along the U direction. However, this is not a limitation; at least one of the microstructures 2000 in the first diffraction structure 210 and the second diffraction structure 220 can be asymmetrically distributed.

[0117] By setting at least one of the first diffraction structure 210 and the second diffraction structure 220 as a subwavelength structure, it is beneficial to simplify the production process and improve production efficiency while achieving better display effects.

[0118] In some examples, as shown in Figures 2 to 4, the emission angle of the image light emitted from the light-emitting surface 104 is 70 to 110 degrees. For example, the emission angle of the image light emitted from the light-emitting surface 104 is 70 or 110 degrees. For example, the emission angle of the image light emitted from the light-emitting surface 104 is 80 to 100 degrees. For example, the emission angle of the image light emitted from the light-emitting surface 104 is 85 to 95 degrees. For example, the emission angle of the image light emitted from the light-emitting surface 104 is 90 degrees. This embodiment of the present disclosure will not list the specific values ​​of the emission angle of the image light emitted from the light-emitting surface 104 one by one. The emission angle of the image light emitted from the light-emitting surface 104 can be any value between 70 and 110 degrees, and the closer it is to 90 degrees, the better the light combining effect of the optical system.

[0119] By adjusting the relative positions of the incident light surface, the exit light surface 104, the first surface 111, and the second surface 112 in the prism group 100, and simultaneously adjusting the microstructure parameters in the first diffraction structure 210 and the second diffraction structure 220, the exit angle of the image light emitted from the exit light surface 104 can be set to close to 90 degrees, which is beneficial to improving the light combining effect of the optical system.

[0120] For example, in other examples, at least one of the first diffraction structure 210 and the second diffraction structure 220 is a subwavelength structure. By adjusting the parameters of the microstructure in the subwavelength structure, the subwavelength structure can have a converging effect on light as a positive lens or a diverging effect as a negative lens, so as to adjust the emission angle of the image light emitted from the light-emitting surface 104 to be close to 90 degrees.

[0121] For example, in other examples, the image light incident on the prism group 100 can be light with polarization characteristics. By adjusting the microstructure parameters in the diffraction structure, it is beneficial to precisely adjust the propagation direction of light with specific polarization characteristics to achieve precise beam splitting.

[0122] For example, the optical system also includes at least one lens located on the light-emitting side of the prism group 100 to adjust the light-emitting direction of the combined light emitted from the prism group 100.

[0123] Figure 9 is a schematic diagram of the optical system shown in Figure 2 in another example. The difference between the optical system shown in Figure 9 and the optical system shown in Figure 4 lies in the different structure between the first surface 111 and the second surface 112. The prism in the optical system shown in Figure 9 can have the same features as the prism in the optical system shown in Figure 4, which will not be described again here.

[0124] In some examples, as shown in Figure 9, the prism assembly 100 includes two prisms, namely a first prism 110 and a second prism 120. A beam-splitting film 300 is also disposed between the first surface 111 and the second surface 112, and the beam-splitting film 300 is located between one of the first surface 111 and the second surface 112 and the diffraction structure. Figure 9 schematically shows the beam-splitting film 300 located between the first surface 111 and the diffraction structure, but it is not limited to this; the beam-splitting film 300 may also be located between the second surface 112 and the diffraction structure.

[0125] In some examples, as shown in Figure 9, the diffraction structure is configured such that the color of the diffracted image light is different from the color of the image light reflected by the beam splitter 300, and the diffraction structure and the beam splitter 300 are configured to transmit at least one light of the same color.

[0126] Compared to the optical system shown in Figure 1, which has four prisms and coats each surface of the prisms to achieve the beam splitting effect of different color image light, the optical system provided in this embodiment has a diffraction structure and a beam splitting film 300 between the first prism 110 and the second prism 120. This can reduce the number of prisms included in the prism group 100, thereby reducing the difficulty of assembling the prism group 100, and at the same time reduce the amount of coating, thereby reducing the coating difficulty, thus optimizing the performance of the optical system and improving the display effect.

[0127] Figure 9 schematically shows that the prism assembly 100 includes two prisms, but is not limited thereto; the prism assembly 100 may also include three prisms as shown in Figure 3.

[0128] In some examples, as shown in Figure 9, one of the diffraction structure and beam splitter 300 is configured to change the propagation direction of the first color image light 401 and transmit the second color image light 402, while the other diffraction structure and beam splitter 300 is configured to change the propagation direction of the third color image light 403 and transmit the first color image light 401 and the second color image light 402. The beam splitter 300 changing the propagation direction of a specific color image light means that the beam splitter 300 reflects that specific color image light.

[0129] For example, as shown in Figure 9, the image light diffracted by the diffraction structure can be the first color image light 401, the image light reflected by the beam splitter 300 can be the third color image light 403, and both the diffraction structure and the beam splitter 300 transmit the second color image light 402. For example, the beam splitter 300 also transmits the first color image light 401. For example, the first color image light 401 can be blue image light, the second color image light 402 can be green image light, and the third color image light 403 can be red image light.

[0130] For example, taking the direction of the arrow in the X direction as right and the direction of the arrow in the Y direction as upward as shown in Figure 9, the first surface 111 and the second surface 112 in the prism group 100 are both tilted along the lower right corner. The diffraction structure and the beam splitter 300 are also tilted along the lower right corner. When the blue image light is incident on the diffraction structure from the upper side, the diffraction structure changes the propagation direction of the blue image light so that it propagates to the left side of the diffraction structure. After being transmitted through the beam splitter 300, it exits from the light-emitting surface 104. At this time, the diffraction structure is equivalent to transmitting the blue image light. When the red image light is incident on the beam splitter 300 from the lower side, the beam splitter 300 reflects the red image light towards the light-emitting surface 104. When the green image light is incident on the diffraction structure and the beam splitter 300 from the right side, the two do not change the propagation direction of the green image light so that it is transmitted to the light-emitting surface 104. Thus, the diffraction structure acts as a transmitter for one specific color image light, while the beam splitter 300 acts as a reflector for another specific color image light.

[0131] Of course, the embodiments disclosed herein are not limited to this. For example, the tilt direction of the diffraction structure and the beam splitter 300 can be replaced with tilting towards the lower left corner; the incident surfaces of the blue image light, red image light and green image light can also be interchanged.

[0132] In some examples, as shown in Figure 9, the diffraction structure includes one of three types of diffraction structures: a first type, a second type, and a third type. The first type diffraction structure includes multiple first microstructures 201, with a distance of 100–200 nm between adjacent first microstructures 201, a height of 150–350 nm for each first microstructure 201, and a dimension of 200–250 nm in a specific direction parallel to the first surface 111. This first type diffraction structure is configured to diffract red image light. The second type diffraction structure includes multiple second microstructures 202, with a distance of 60–120 nm between adjacent second microstructures 202, and a height of… The second type of diffraction structure has a size of 200–500 nanometers, and the second microstructure 202 has a size of 100–150 nanometers in a specific direction parallel to the first surface 111. The second type of diffraction structure is configured to diffract blue image light. The third type of diffraction structure includes a plurality of third microstructures, the distance between adjacent third microstructures is 80–160 nanometers, the height of the third microstructure is 200–400 nanometers, and the size of the third microstructure in a specific direction parallel to the first surface 111 is 150–200 nanometers. The third type of diffraction structure is configured to diffract green image light.

[0133] Figure 9 schematically illustrates a second-type diffraction structure, but it is not limited to this; the diffraction structure can be a first-type or a third-type diffraction structure. The first-type, second-type, and third-type diffraction structures in this example can have the same characteristics as the first-type, second-type, and third-type diffraction structures in the optical system shown in Figure 4, and will not be described again here.

[0134] Figure 9 schematically shows a structural substrate 230 disposed between the diffraction structure and the beam-splitting film 300, but is not limited thereto. When the diffraction structure is formed on the surface of the prism, the diffraction structure can directly contact the beam-splitting film 300.

[0135] Figure 10 is a partial structural schematic diagram of a display device according to another embodiment of the present disclosure.

[0136] As shown in Figure 10, the display device includes multiple displays and any of the aforementioned optical systems. The multiple displays are arranged in a one-to-one correspondence with multiple light-incident surfaces, and different displays emit image light of different colors. Figure 10 schematically shows the optical system as shown in Figure 2, but the optical system can be any of the examples shown in Figures 3 to 9.

[0137] For example, as shown in Figure 10, multiple displays include a first display 410, a second display 420, and a third display 430. The first display 410 emits a first color image light 401, the second display 420 emits a second color image light 402, and the third display 430 emits a third color image light 403. The first display 410 is positioned opposite to the third light-incident surface 103, the second display 420 is positioned opposite to the first light-incident surface 101, and the third display 430 is positioned opposite to the second light-incident surface 102. The different color image lights emitted from the different displays are transmitted through the prisms in the prism assembly 100 and diffracted by the diffraction structure, and then combine at the light-emitting surface 104.

[0138] Figure 10 schematically shows three displays, but it is not limited to this; the number of displays can also be two.

[0139] For example, as shown in Figure 10, the display screen can be any type of display screen, such as liquid crystal display screen, inorganic light-emitting diode display screen, organic light-emitting diode display screen, quantum dot display screen, etc.

[0140] For example, the display device can be an augmented reality (AR) display device.

[0141] For example, the display device can be a near-eye display device, such as a wearable helmet or glasses, but the embodiments disclosed herein are not limited thereto.

[0142] The following points need to be explained:

[0143] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure, and other structures can be referred to the general design.

[0144] (2) Where there is no conflict, features of the same embodiment and different embodiments of this disclosure may be combined with each other.

[0145] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. An optical system, comprising: A prism assembly includes multiple incident light surfaces and one exit light surface. Each incident light surface is configured to receive image light of a single color. Different incident light surfaces are configured to receive image light of different colors. The different color image lights converge in the prism assembly and exit from the exit light surface. The prism group includes fewer than four prisms, and includes at least a first prism and a second prism. The first surface of the first prism and the second surface of the second prism are disposed opposite each other. A microstructure array is disposed between the first surface and the second surface. The microstructure array is configured to change the propagation direction of at least one color image light and transmit at least another color image light.

2. The optical system according to claim 1, wherein, The microstructure array includes at least one diffraction structure, each diffraction structure being configured to diffract one color image light and transmit at least one color image light from other color image lights.

3. The optical system according to claim 2, wherein, The at least one diffraction structure includes at least one of a diffraction grating and a subwavelength structure.

4. The optical system according to claim 3, wherein, The prism group includes two prisms, namely the first prism and the second prism, and the at least one diffraction structure includes a first diffraction structure and a second diffraction structure, wherein the second diffraction structure is located between the first diffraction structure and the second surface. One of the first diffraction structure and the second diffraction structure is configured to diffract a first color image light and transmit a second color image light, and the other of the first diffraction structure and the second diffraction structure is configured to diffract a third color image light and transmit the first color image light and the second color image light.

5. The optical system according to claim 4, wherein, Both the first diffraction structure and the second diffraction structure include multiple microstructures, each of which includes multiple microstructure parameters, such as the distance between adjacent microstructures, the height of the microstructure, and the size of the microstructure in a specific direction parallel to the first surface. The values ​​of at least one type of microstructure parameter in the first diffraction structure and the second diffraction structure are different.

6. The optical system according to claim 3, wherein, The prism assembly includes two prisms, namely the first prism and the second prism. A beam-splitting film is also disposed between the first surface and the second surface, and the beam-splitting film is located between one of the first surface and the second surface and the diffraction structure. The diffraction structure is configured such that the color of the diffracted image light is different from the color of the image light reflected by the beam splitter, and the diffraction structure and the beam splitter are configured to transmit at least one light of the same color.

7. The optical system according to claim 6, wherein, One of the diffraction structure and the beam splitter is configured to change the propagation direction of the first color image light and transmit the second color image light, and the other of the diffraction structure and the beam splitter is configured to change the propagation direction of the third color image light and transmit the first color image light and the second color image light.

8. The optical system according to claim 4, wherein, The first diffraction structure and the second diffraction structure are two of three types of diffraction structures, which include a first type of diffraction structure, a second type of diffraction structure, and a third type of diffraction structure. The first type of diffraction structure includes a plurality of first microstructures, the distance between adjacent first microstructures is 100-200 nanometers, the height of the first microstructure is 150-350 nanometers, the size of the first microstructure in a specific direction parallel to the first surface is 200-250 nanometers, and the first type of diffraction structure is configured to diffract red image light. The second type of diffraction structure includes a plurality of second microstructures, the distance between adjacent second microstructures is 60-120 nanometers, the height of the second microstructure is 200-500 nanometers, the size of the second microstructure in a specific direction parallel to the first surface is 100-150 nanometers, and the second type of diffraction structure is configured to diffract blue image light. The third type of diffraction structure includes multiple third microstructures, with a distance of 80–160 nanometers between adjacent third microstructures, a height of 200–400 nanometers for each third microstructure, and a dimension of 150–200 nanometers for each third microstructure in a specific direction parallel to the first surface. The third type of diffraction structure is configured to diffract green image light.

9. The optical system according to claim 6 or 7, wherein, The diffraction structure includes one of three types of diffraction structures, namely, a first type of diffraction structure, a second type of diffraction structure, and a third type of diffraction structure. The first type of diffraction structure includes a plurality of first microstructures, the distance between adjacent first microstructures is 100-200 nanometers, the height of the first microstructure is 150-350 nanometers, the size of the first microstructure in a specific direction parallel to the first surface is 200-250 nanometers, and the first type of diffraction structure is configured to diffract red image light. The second type of diffraction structure includes a plurality of second microstructures, the distance between adjacent second microstructures is 60-120 nanometers, the height of the second microstructure is 200-500 nanometers, the size of the second microstructure in a specific direction parallel to the first surface is 100-150 nanometers, and the second type of diffraction structure is configured to diffract blue image light. The third type of diffraction structure includes multiple third microstructures, with a distance of 80–160 nanometers between adjacent third microstructures, a height of 200–400 nanometers for each third microstructure, and a dimension of 150–200 nanometers for each third microstructure in a specific direction parallel to the first surface. The third type of diffraction structure is configured to diffract green image light.

10. The optical system according to claim 8 or 9, wherein, The subwavelength structure includes multiple microstructures, which are at least one of the multiple first microstructures, the multiple second microstructures, and the multiple third microstructures. The microstructures in the subwavelength structure are inclined relative to the first surface, and the inclination angle of the microstructures relative to the first surface is 5 to 70 degrees.

11. The optical system according to claim 4, 5 or 8, wherein, A structural substrate is disposed between the first diffraction structure and the second diffraction structure. Both the first diffraction structure and the second diffraction structure are disposed on the structural substrate. The structural substrate is parallel to the first surface and has a thickness of 0.1 to 2 mm.

12. The optical system according to any one of claims 1-11, wherein, The plurality of light-incident surfaces include a first light-incident surface, a second light-incident surface, and a third light-incident surface. The first light-incident surface is parallel to the light-out surface, the second light-incident surface is parallel to the third light-incident surface and is located on both sides of the first surface, and the included angle between the first surface and the second and third light-incident surfaces is less than 90 degrees.

13. The optical system according to any one of claims 1-12, wherein, The emission angle of the image light emitted from the light-emitting surface is 70 to 110 degrees.

14. A display device comprising a plurality of displays and an optical system according to any one of claims 1-13, wherein, The plurality of displays are arranged in a one-to-one correspondence with the plurality of light-incident surfaces, and different displays emit image light of different colors.

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