Optical waveguide device and display system

Abstract

The utility model provides an optical waveguide device and a display system comprising the same. The optical waveguide device comprises an optical waveguide sheet, a coupling-in grating, a compensation grating and a coupling-out grating, and the compensation grating is arranged on the surface, opposite to the coupling-in grating, of the optical waveguide sheet and used for receiving transmission light which is incident on the optical waveguide device and cannot be diffracted and coupled into the optical waveguide sheet by the coupling-in grating. And the transmission light is diffracted and coupled into the optical waveguide sheet, so that the transmission light and the incident light reflected by the coupled grating can be transmitted in the optical waveguide sheet through total reflection. On the basis that the coupling-in grating and the coupling-out grating guarantee the coupling-in efficiency and the coupling-out efficiency of the optical waveguide device, more incident light rays are diffracted and coupled into the optical waveguide sheet through the compensation grating, the problem of light loss caused by limited diffraction efficiency of the coupling-in grating is solved, the comprehensive light energy utilization rate of the optical waveguide device is improved, and the optical waveguide device is suitable for large-scale popularization and application. And the brightness of the overall field of view of the display system is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of diffractive optical devices, in particular to an optical waveguide device and a display system. Background Art

[0002] Optical waveguide display systems are mainly applied in the field of augmented reality, such as display devices like AR glasses and AR-HUDs. They have broad application prospects in many fields such as military, medical, education, and entertainment.

[0003] In an optical waveguide display system, the light emitted by a light-emitting device generally enters the surface of the optical waveguide device vertically. After being diffracted by the coupling grating in the optical waveguide device, most of the light can be coupled into the optical waveguide sheet and transmitted to the next optical element at the total reflection angle therein. As the source for introducing the entire light-emitting device into the waveguide, the coupling efficiency of the coupling grating plays a crucial role in the overall efficiency of the entire waveguide. Since the diffraction efficiency of the coupling grating cannot reach 100%, a part of the light passes through the coupling grating and the optical waveguide sheet and is lost from the other side of the optical waveguide sheet, thereby causing light energy loss in the display system.

[0004] In some prior arts, an output grating and / or a reflection grating are added in the optical waveguide device to reduce light loss. However, it can only reduce the light loss at the output grating. In practice, the light loss at the output grating is not much, and the brightness improvement effect is limited. It cannot effectively solve the problem of light loss caused by the limited diffraction efficiency of the input grating. Summary of the Utility Model

[0005] The utility model provides an optical waveguide device and a display system, which can solve the technical problem of light loss in the existing optical waveguide display system due to the limited diffraction efficiency of the input grating in the optical waveguide device.

[0006] In a first aspect, an embodiment of the present application provides an optical waveguide device, including:

[0007] An optical waveguide sheet, including a first surface and a second surface;

[0008] A coupling grating, disposed on the first surface of the optical waveguide sheet; the coupling grating is used to receive incident light within a preset field of view angle and diffract the incident light into the optical waveguide sheet, so that the incident light can propagate in the optical waveguide sheet through total reflection;

[0009] A compensation grating is disposed on the second surface of the optical waveguide sheet and is disposed opposite to the coupling grating; the compensation grating is configured to receive the transmitted light in the incident light that fails to be diffractively coupled into the optical waveguide sheet by the coupling grating, and diffract the transmitted light and couple it into the optical waveguide sheet, so that the transmitted light can propagate in the optical waveguide sheet by total reflection; wherein, the angle between the coherent lights during the exposure of the compensation grating is the same as the angle between the coherent lights during the exposure of the coupling grating;

[0010] A coupling-out grating is disposed on the first surface or the second surface of the optical waveguide sheet; the coupling-out grating is configured to receive the incident light and the transmitted light propagating in the optical waveguide sheet, and diffractively couple the incident light and the transmitted light out of the optical waveguide sheet.

[0011] In some embodiments, the width L of the compensation grating in the light propagation direction satisfies: L ≤ d * tanθ;

[0012] wherein, d is the thickness of the optical waveguide sheet; θ is the reflection angle of the incident light diffractively coupled into the optical waveguide sheet by the coupling grating in the optical waveguide sheet.

[0013] In some embodiments, the width of the compensation grating in the light propagation direction is half of the width of the coupling grating.

[0014] In some embodiments, the coupling grating is a reflective volume holographic grating or a transmissive volume holographic grating; the compensation grating is a reflective volume holographic grating; the coupling-out grating is a reflective volume holographic grating or a transmissive volume holographic grating.

[0015] In some embodiments, the optical waveguide device further includes a folding grating; the folding grating is disposed in the light output direction of the coupling grating and the light input direction of the coupling-out grating; the folding grating is configured to reflect the incident light propagating in the optical waveguide sheet to achieve one-dimensional pupil expansion of the light at the folding grating;

[0016] wherein, the folding grating is a volume holographic grating.

[0017] In a second aspect, an embodiment of the present application further provides a display system, including a light-emitting device and an optical waveguide device;

[0018] The light-emitting device is configured to generate incident light within a preset field of view angle range; the optical waveguide device includes an optical waveguide sheet, a coupling grating, a compensation grating, and a coupling-out grating;

[0019] The optical waveguide sheet includes a first surface and a second surface; wherein, the first surface of the optical waveguide sheet is the surface close to the light-emitting device;

[0020] The coupling grating is disposed on the first surface of the optical waveguide sheet; the coupling grating is configured to receive the incident light and diffract the incident light and couple it into the optical waveguide sheet, so that the incident light can propagate in the optical waveguide sheet by total internal reflection;

[0021] The compensation grating is disposed on the second surface of the optical waveguide sheet and is disposed opposite to the coupling grating; the compensation grating is configured to receive the transmitted light that fails to be diffracted and coupled into the optical waveguide sheet by the coupling grating in the incident light, and diffract the transmitted light and couple it into the optical waveguide sheet, so that the transmitted light can propagate in the optical waveguide sheet by total internal reflection; wherein, the included angle of the coherent light during exposure of the compensation grating is the same as the included angle of the coherent light during exposure of the coupling grating;

[0022] The output grating is disposed on the first surface or the second surface of the optical waveguide sheet; the output grating is configured to receive the incident light and the transmitted light propagating in the optical waveguide sheet, and diffract and output the incident light and the transmitted light from the optical waveguide sheet.

[0023] In some embodiments, the width L of the compensation grating in the light propagation direction satisfies: L ≤ d * tanθ;

[0024] Wherein, d is the thickness of the optical waveguide sheet; θ is the reflection angle of the incident light diffracted by the coupling grating and coupled into the optical waveguide sheet in the optical waveguide sheet.

[0025] In some embodiments, the width of the compensation grating in the light propagation direction is half of the width of the coupling grating.

[0026] In some embodiments, the coupling grating is a reflective volume holographic grating or a transmissive volume holographic grating; the compensation grating is a reflective volume holographic grating; the output grating is a reflective volume holographic grating or a transmissive volume holographic grating.

[0027] In some embodiments, the display system further includes a folding grating; the folding grating is disposed in the light output direction of the coupling grating and the light input direction of the output grating; the folding grating is configured to reflect the incident light propagating in the optical waveguide sheet to achieve one-dimensional pupil expansion of the light at the folding grating;

[0028] Wherein, the folding grating is a volume holographic grating.

[0029] The optical waveguide device provided by the embodiments of the present application and the display system including the optical waveguide device are configured to provide a compensation grating on the surface opposite to the grating coupled into the optical waveguide sheet, for receiving the transmitted light that is incident on the optical waveguide device but not diffracted and coupled into the optical waveguide sheet by the coupling grating, and diffracting and coupling the transmitted light into the optical waveguide sheet, so that the transmitted light and the incident light diffracted by the coupling grating can propagate in the optical waveguide sheet through total internal reflection together. On the basis that the coupling grating and the decoupling grating ensure the coupling efficiency and the decoupling efficiency of the optical waveguide device, the present application further diffracts and couples more incident light into the optical waveguide sheet through the compensation grating, compensating for the light loss problem caused by the limited diffraction efficiency of the coupling grating, improving the comprehensive light energy utilization rate of the optical waveguide device, and increasing the display brightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0031] Figure 1 It is a schematic side view of the structure of the optical waveguide device provided by an embodiment of the present application;

[0032] Figure 2 It is a schematic diagram of the principle of the optical waveguide device provided by an embodiment of the present application;

[0033] Figure 3 It is a schematic diagram of the principle of the optical waveguide device provided by another embodiment of the present application;

[0034] Figure 4 It is a schematic top view of the structure of the optical waveguide device provided by another embodiment of the present application (the compensation grating is not shown);

[0035] Figure 5 It is a schematic diagram of the structure of the display system provided by an embodiment of the present application.

[0036] Through the above drawings, the clear embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These drawings and the textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following further describes the present utility model in detail through specific embodiments in conjunction with the accompanying drawings. Similar elements in different embodiments are labeled with related similar element numbers. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification to avoid overwhelming the core part of the present application with excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0038] In addition, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can also be reordered or adjusted in an obvious manner by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean a necessary sequence, unless it is stated that a certain sequence must be followed.

[0039] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein. The objects distinguished by "first", "second", etc. are usually of the same type and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" in the specification and claims means at least one of the connected objects. The character " / " generally indicates an "or" relationship between the associated objects before and after. And the "connection" and "coupling" mentioned in the present application, unless otherwise specified, both include direct and indirect connection (coupling).

[0040] The following uses specific embodiments to detail the technical solution of the present application and how the technical solution of the present application solves the above technical problems. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0041] Figure 1 It is a side view schematic diagram of the optical waveguide device structure provided by an embodiment of the present application. As Figure 1 shown, the optical waveguide device provided in this embodiment includes an optical waveguide sheet 110, an input grating 120, a compensation grating 130, and an output grating 140.

[0042] In this embodiment, the optical waveguide sheet 110 is a medium device that guides the propagation of light waves therein, also known as a dielectric optical waveguide. Utilizing the total internal reflection phenomenon at the interface of media with different refractive indices, the light waves are confined to propagate within the waveguide and its surrounding limited area. The basic structure of the optical waveguide is composed of a light-transparent medium (such as quartz glass) to form a guiding structure for transmitting optical-frequency electromagnetic waves. The transmission principle of the optical waveguide relies on the total internal reflection phenomenon. When light waves travel from an optically denser medium to an optically less dense medium, if the incident angle is greater than the critical angle, the light waves will be completely reflected back into the original medium and thus propagate along a predetermined path within the waveguide. The shape of the optical waveguide sheet 110 can be any suitable shape. For example, it can be rectangular, dumbbell-shaped, or butterfly-shaped, etc. The optical waveguide sheet 110 can be made of glass, optical plastic, or other optical transmission materials, which is not limited in this embodiment.

[0043] In this embodiment, the optical waveguide sheet 110 includes a first surface 1101 and a second surface 1102, where the first surface 1101 and the second surface 1102 face away from each other. In some embodiments, the first surface 1101 can be the surface of the display system having the optical waveguide sheet 110 facing the observer's eyes, that is, the first surface 1101 is the surface close to the light-emitting device in the display system, and the second surface 1102 is the surface away from the light-emitting device in the display system. The optical waveguide sheet 110 can propagate light in a direction parallel to the first surface 1101 and the second surface 1102 through total internal reflection. In practice, for the optical waveguide sheet 110, it has a preset coupling-in region and a coupling-out region. The coupling-in region covers the range of incident light rays, and the coupling-out region covers the range of outgoing light rays.

[0044] In this embodiment, the coupling grating 120 is disposed on the first surface 1101 of the optical waveguide sheet 110 and is located in the coupling-in region of the optical waveguide sheet 110. The coupling grating 120 is used to receive incident light rays within a preset field of view angle and diffract the incident light rays into the optical waveguide sheet 110 so that the incident light rays can propagate within the optical waveguide sheet 110 through total internal reflection.

[0045] The coupling-out grating 140 is disposed on the first surface 1101 or the second surface 1102 of the optical waveguide sheet 110 and is located in the coupling-out region of the optical waveguide sheet 110. The coupling-out grating 140 is used to receive the incident light rays and transmitted light rays propagating within the optical waveguide sheet 110 and diffract and couple out the incident light rays and transmitted light rays from the optical waveguide sheet 110.

[0046] It can be understood that the input grating 120 and the output grating 140 can be located on the same side of the optical waveguide sheet 110. For example, both are disposed on the first surface 1101 of the optical waveguide sheet 110, or they can be located on different sides, that is, on the first surface 1101 and the second surface 1102 respectively. As a preferred embodiment, the input region is located on the first surface 1101, and the output region is also located on the first surface 1101. Thus, the light-emitting device on the eye side projects input light to the input region, and after diffraction, it is emitted from the output region to the eye.

[0047] In some embodiments, both the input grating 120 and the output grating 140 are volume holographic gratings. A volume holographic grating is an imaging element. The production of a volume holographic grating uses holographic technology. Two exposure light beams with the same wavelength interfere and expose inside the photosensitive material, so that interference fringes are recorded inside the photosensitive material, that is, a volume holographic grating is formed. Compared with the relatively mature surface relief diffraction grating in the prior art, the volume holographic grating has a higher diffraction efficiency. Especially at specific wavelengths and incident angles, the diffraction efficiency can reach a very high level. Moreover, the volume holographic grating can achieve a larger field of view angle, which helps to improve the performance of the optical system. At the same time, the manufacturing process of the volume holographic grating is more efficient than that of the surface relief grating, which can shorten the production cycle, reduce costs, and can realize multiple functions such as imaging and image conversion. It has high design flexibility and can meet the requirements of different application scenarios.

[0048] In a more specific embodiment, the input grating 120 can be a reflective volume holographic grating or a transmissive volume holographic grating; similarly, the output grating 140 can be a reflective volume holographic grating or a transmissive volume holographic grating. It should be noted that the reflective volume holographic grating and the transmissive volume holographic grating each have their own advantages and disadvantages. Generally speaking, under the same recording conditions, the diffraction efficiency of the reflective volume holographic grating is usually higher than that of the transmissive volume holographic grating. The reflective volume holographic grating has stronger wavelength selectivity and can more accurately select light of a specific wavelength for diffraction, thus reducing the dispersion phenomenon. And since the reference beam and the diffracted beam (signal beam) of the reflective volume holographic grating are both on the same side of the grating, it is very beneficial for designing a compact optical system. Compared with the reflective volume holographic grating, the manufacturing process of the transmissive volume holographic grating is relatively simple and easier to achieve large-scale production, which helps to reduce the manufacturing cost and improve the production efficiency. Therefore, when choosing which grating to use, it is necessary to comprehensively consider factors such as specific application requirements, performance requirements, and cost budgets.

[0049] It should be noted that the performance parameters of the coupling grating 120 mainly include diffraction efficiency, coupling efficiency, bandwidth, insertion loss, etc. Among them, the diffraction efficiency is a key performance index, which reflects the efficiency of the grating in coupling the incident light wave into the waveguide. The diffraction efficiency of the coupling grating 120 in the optical waveguide device usually does not exceed 80%. Inevitably, a part of the incident light cannot be diffracted and coupled into the optical waveguide chip 110 by the coupling grating 120, that is, a part of the incident light will directly pass through the coupling grating 120 and the optical waveguide 110. In other words, this part of the light cannot be fully utilized, resulting in a part of light loss.

[0050] Therefore, in this embodiment, a compensation grating 130 is additionally provided on the second surface 1102 of the optical waveguide chip 110 to solve the problem of light loss. The compensation grating 130 is disposed opposite to the coupling grating 120, and the angle between the coherent light during the exposure of the compensation grating 130 is the same as the angle between the coherent light during the exposure of the coupling grating 120. The compensation grating 130 is used to receive the transmitted light that cannot be diffracted and coupled into the optical waveguide chip 110 by the coupling grating 120 from the incident light, and diffract the transmitted light and then couple it into the optical waveguide chip 110, so that the transmitted light can propagate in the optical waveguide chip 110 through total internal reflection.

[0051] That is, in this embodiment, when the incident light is projected onto the coupling grating 120, most of the incident light is diffracted by the coupling grating 120 to form diffracted light. The diffracted light is totally reflected on the second surface 1102 of the optical waveguide chip 110 and then projected onto the first surface 1101. Then, it totally reflects and propagates between the first surface 1101 and the second surface 1102 of the optical waveguide chip 110 towards the output grating 140, and finally is coupled out from the output grating 140. The light transmitted through the coupling grating 120 is projected onto the compensation grating 130, and the compensation grating 130 is used to diffract it to form reflected light, which is projected onto the first surface 1101 of the optical waveguide chip 110 in the form of reflection. Then, it totally reflects and propagates between the first surface 1101 and the second surface 1102 of the optical waveguide chip 110 towards the output grating 140, and finally is coupled out from the output grating 140. Thus, the transmitted light that would otherwise be lost from the second surface 1102 of the optical waveguide chip 110 when passing through the coupling grating 120 is reused, improving the light energy utilization rate of the optical waveguide device, and further improving the output efficiency of the field of view, achieving an increase in the overall brightness of the optical waveguide device.

[0052] In some embodiments, when fabricating the compensation grating 130 and the output grating 140, the angle between the coherent light during the exposure of the compensation grating 130 needs to be set to be the same as the angle between the coherent light during the exposure of the output grating 140, so that the light diffracted by the compensation grating 130 can smoothly be output from the output grating 140 after entering the optical waveguide sheet 110, that is: the existence of the compensation grating 130 (reflecting the leaked light) has solved the problem of light leakage, but if the angles during the exposure of the two are inconsistent, it will cause this part of the leaked light not to be output from the optical waveguide sheet 110, making this part of the light still wasted and the final picture brightness not increasing.

[0053] In some embodiments, the compensation grating 130 is also a reflective volume holographic grating.

[0054] In one embodiment, the width L of the compensation grating 130 in the light propagation direction satisfies: L ≤ d * tanθ; where d is the thickness of the optical waveguide sheet 110; θ is the reflection angle of the incident light coupled into the optical waveguide sheet 110 after being diffracted by the input grating 120 within the optical waveguide sheet 110.

[0055] It should be noted that Figure 1 In the side view of the optical waveguide device structure provided in this embodiment, the light propagates from the input grating 120 on the left to the output grating 140 on the right. In this embodiment, the width L of the compensation grating 130 in the light propagation direction refers to the horizontal dimension in the side view as Figure 1 shown. In this direction, the width L of the compensation grating 130 satisfies: L ≤ d * tanθ. Further, it should be noted that in the vertical direction in the side view as Figure 1 shown, the dimension of the compensation grating 130 is the same as the corresponding dimension of the input grating 120.

[0056] Figure 2 This is the schematic diagram of the optical waveguide device provided by an embodiment of the present application. As Figure 2 shown, in a specific embodiment, combining the structure of the optical waveguide device in any of the above embodiments, when the incident light is projected onto the input grating 120, most of the incident light is diffracted by the input grating 120 to form diffracted light, and the other part of the incident light passes through the input grating 120 and is projected onto the compensation grating 130. The transmitted light is diffracted by the compensation grating 130 to form reflected light. The diffracted light and the reflected light are projected onto the first surface 1101 together, and then totally reflect and propagate between the first surface 1101 and the second surface 1102 of the optical waveguide sheet 110 towards the output grating 140, and finally are output from the output grating 140 and enter the human eye. Figure 2Among them, the solid line represents the diffracted light formed by the diffraction of the coupling grating 120, and the dashed line represents the reflected light formed by the diffraction of the compensation grating 130. Assuming that the diffraction efficiency of the coupling grating 120 is 80%, that is, 80% of the incident light can be diffracted by the coupling grating 120 to form diffracted light. That is to say, the light intensity that can continue to propagate in the optical waveguide sheet 110 is 80% of the incident light, that is, 20% of the light is lost at the coupling grating 120. The transmitted light will be projected onto the compensation grating 130, and the compensation grating 130 is used to diffract and form reflected light, that is, a part of the 20% light loss will be reflected back into the optical waveguide and utilized again. The amount of reflected light is related to the width of the compensation grating.

[0057] As a preferred embodiment, the width of the compensation grating 130 is half of the width of the coupling grating 120. At this time, half of the transmitted light reaches the compensation grating 130. The diffraction efficiency of the compensation grating is 80%, then the light intensity that can be utilized again is 20% * 0.5 * 80%. After synthesis, after adding the compensation grating 130, the light intensity that can be totally reflected and propagated in the optical waveguide sheet 110 is 80% + 20% * 0.5 * 80% = 88%, and the light energy utilization rate is increased by 8%.

[0058] Figure 3 This is the schematic diagram of the optical waveguide device provided by another embodiment of the present application. As Figure 2 shown, in a specific embodiment, combining the structure of the optical waveguide device in any of the above embodiments, assuming that the size of the compensation grating 130 exceeds the defined size in the above embodiment, a part of the diffracted light formed by the diffraction of the incident light through the coupling grating 120 will pass through the second surface 1102 of the optical waveguide sheet 110 and be transmitted onto the compensation grating 130, and this part of the light will exit from the compensation grating 130 and will not be transmitted in the optical waveguide, forming a new light leakage point, and higher light energy utilization cannot be achieved. Therefore, it is very necessary to define the size of the compensation grating 130.

[0059] Figure 4 This is the top view schematic diagram of the optical waveguide device structure provided by another embodiment of the present application (the compensation grating is not shown). As Figure 4 shown, on the basis of any of the above embodiments, the optical waveguide device provided in this embodiment further includes a folding grating 150 disposed in the light output direction of the coupling grating 120 and the light input direction of the coupling-out grating 140.

[0060] In this embodiment, the folding grating 150 is used to reflect the incident light propagating in the optical waveguide sheet 110 to achieve one-dimensional pupil expansion at the folding grating 150. In some embodiments, the folding grating 150 is a volume holographic grating.

[0061] In summary, the optical waveguide device provided by the embodiment of the present application includes an optical waveguide sheet, an input grating, a compensation grating, and an output grating. By providing a compensation grating on the surface opposite to the input grating on the optical waveguide sheet, it is used to receive the transmitted light that is incident on the optical waveguide device and not diffracted and coupled into the optical waveguide sheet by the input grating, and diffract the transmitted light and then couple it into the optical waveguide sheet, so that the transmitted light and the incident light diffracted by the input grating can propagate in the optical waveguide sheet through total internal reflection together. On the basis that the input grating and the output grating ensure the input efficiency and output efficiency of the optical waveguide device, the present application further diffracts and couples more incident light into the optical waveguide sheet through the compensation grating, making up for the light loss problem caused by the limited diffraction efficiency of the input grating, improving the comprehensive light energy utilization rate of the optical waveguide device, and increasing the display brightness.

[0062] Figure 5 FIG. is a schematic structural diagram of a display system provided by an embodiment of the present application. As Figure 5 shown, the display system provided by this embodiment includes a light emitting device 510 and the optical waveguide device 520 described in any of the above embodiments.

[0063] In this embodiment, the light emitting device 510 is used to generate incident light within a preset field of view angle and irradiate it on the optical waveguide device 520. The light emitting device 520 can be a micro display such as a Laser Beam Scanning (LBS), Digital Light Procession (DLP), Digital Micromirror Device (DMD), Liquid Crystal On Silicon (LCOS), Micro ElectroMechanical System (MEMS), Organic Light Emitting Diode (OLED), MicroLED light emitting device, etc. The light emitted by the light emitting device 520 is visible light.

[0064] The optical waveguide device 520 is used to receive the incident light, and successively diffract and couple it into the optical waveguide sheet through the input grating and the compensation grating, so that most of the light intensity in the incident light can propagate in the optical waveguide sheet through total internal reflection, and finally be coupled out through the output grating and enter the human eye.

[0065] It should be noted that the display system in this embodiment has the beneficial effects of the optical waveguide device in any of the above embodiments, which will not be elaborated here.

[0066] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Those of ordinary skill in the art, under the inspiration of the present application, without departing from the spirit of the present application and the scope protected by the claims, for those skilled in the technical field to which the present application pertains, according to the idea of the present application, can also make several simple deductions, deformations or substitutions, all of which fall within the protection scope of the present application.

Claims

1. An optical waveguide device, characterized in that, Comprising: An optical waveguide sheet, including a first surface and a second surface; An input grating, disposed on the first surface of the optical waveguide sheet; The input grating is configured to receive incident light within a preset field of view angle, and diffract the incident light and couple it into the optical waveguide sheet, so that the incident light can propagate within the optical waveguide sheet through total internal reflection; A compensation grating, disposed on the second surface of the optical waveguide sheet and opposite to the input grating; the compensation grating is configured to receive the transmitted light that fails to be diffracted and coupled into the optical waveguide sheet by the input grating among the incident light, and diffract the transmitted light and couple it into the optical waveguide sheet, so that the transmitted light can propagate within the optical waveguide sheet through total internal reflection; wherein, the included angle of the coherent light during the exposure of the compensation grating is the same as the included angle of the coherent light during the exposure of the input grating; An output grating, disposed on the first surface or the second surface of the optical waveguide sheet; the output grating is configured to receive the incident light and the transmitted light propagating within the optical waveguide sheet, and diffract and couple out the incident light and the transmitted light from the optical waveguide sheet.

2. The optical waveguide device according to claim 1, wherein The width L of the compensation grating in the light propagation direction satisfies: L ≤ d * tanθ; Wherein, d is the thickness of the optical waveguide sheet; θ is the reflection angle of the incident light diffracted by the input grating and coupled into the optical waveguide sheet within the optical waveguide sheet.

3. The optical waveguide device according to claim 2, characterized in that, The width of the compensation grating in the light propagation direction is half of the width of the input grating.

4. The optical waveguide device according to any one of claims 1-3, characterized in that, The input grating is a reflective volume holographic grating or a transmissive volume holographic grating; the compensation grating is a reflective volume holographic grating; the output grating is a reflective volume holographic grating or a transmissive volume holographic grating.

5. The optical waveguide device according to claim 4, characterized in that, Further comprising a folding grating; the folding grating is disposed in the light output direction of the input grating and the light input direction of the output grating; the folding grating is configured to reflect the incident light propagating within the optical waveguide sheet to achieve one-dimensional pupil expansion at the folding grating; Wherein, the folding grating is a volume holographic grating.

6. A display system, characterized in that, Comprising a light emitting device and an optical waveguide device; The light emitting device is configured to generate incident light within a preset field of view angle; the optical waveguide device includes an optical waveguide sheet, an input grating, a compensation grating, and an output grating; The optical waveguide sheet includes a first surface and a second surface; wherein, the first surface of the optical waveguide sheet is the surface close to the light emitting device; The input grating is disposed on the first surface of the optical waveguide sheet; the input grating is configured to receive the incident light, and diffract the incident light and couple it into the optical waveguide sheet, so that the incident light can propagate within the optical waveguide sheet through total internal reflection; The compensation grating is disposed on the second surface of the optical waveguide sheet and opposite to the input grating; the compensation grating is configured to receive the transmitted light that fails to be diffracted and coupled into the optical waveguide sheet by the input grating among the incident light, and diffract the transmitted light and couple it into the optical waveguide sheet, so that the transmitted light can propagate within the optical waveguide sheet through total internal reflection; wherein, the included angle of the coherent light during the exposure of the compensation grating is the same as the included angle of the coherent light during the exposure of the input grating; The output grating is disposed on the first surface or the second surface of the optical waveguide sheet; the output grating is configured to receive the incident light and the transmitted light propagating in the optical waveguide sheet, and diffract and output the incident light and the transmitted light from the optical waveguide sheet.

7. The display system according to claim 6, wherein The width L of the compensation grating in the light propagation direction satisfies: L ≤ d * tanθ; Wherein, d is the thickness of the optical waveguide sheet; θ is the reflection angle of the incident light coupled into the optical waveguide sheet after being diffracted by the input grating within the optical waveguide sheet.

8. The display system according to claim 7, wherein, The width of the compensation grating in the light propagation direction is half of the width of the input grating.

9. The display system according to any one of claims 6-8, characterized in that, The input grating is a reflective volume holographic grating or a transmissive volume holographic grating; the compensation grating is a reflective volume holographic grating; the output grating is a reflective volume holographic grating or a transmissive volume holographic grating.

10. The display system according to claim 9, wherein, It further includes a folding grating; the folding grating is disposed in the light output direction of the input grating and the light input direction of the output grating; the folding grating is configured to reflect the incident light propagating in the optical waveguide sheet to achieve one-dimensional pupil expansion of the light at the folding grating; Wherein, the folding grating is a volume holographic grating.

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