Composite waveguide and display module

Abstract

The utility model relates to a composite waveguide and a display module. The composite waveguide includes: a waveguide substrate; the coupling-in unit comprises a first light regulation and control unit and a second light regulation and control unit, the first light regulation and control unit and the second light regulation and control unit are arranged on the same side of the waveguide substrate in a stacked mode, or the first light regulation and control unit and the second light regulation and control unit are arranged on the two sides of the waveguide substrate respectively; the first light regulation and control unit comprises a first light orientation layer and a first liquid crystal grating layer which are arranged in a stacked mode, and the first light orientation layer is arranged close to the waveguide substrate. The second light regulation and control unit comprises a second light alignment layer and a second liquid crystal grating layer which are stacked, and the second light alignment layer is arranged close to the waveguide substrate; the coupling-out unit and at least one light regulation and control unit in the first light regulation and control unit and the second light regulation and control unit are located on the same side of the waveguide substrate; the out-coupling unit is a relief grating. The composite waveguide can maximize the wide incident angle optical coupling utilization rate, and can also realize the display uniformity in the eye box range.

Description

Technical Field

[0001] The utility model relates to the technical field of optical waveguides, in particular to a composite waveguide and a display module. Background Art

[0002] Augmented reality (AR) display allows an observer to view both real objects in the external world and superimposed images, data, and other information in the real environment, so it is widely used in various fields. The reason is that augmented reality display provides a function of real-time and on-site interaction with the real environment without barriers, which traditional display devices do not have, bringing a new visual experience to users. Since the development of augmented reality display optical technology to date, the main solutions are roughly divided into coaxial side-view prism solutions, arrayed semi-transmissive film waveguide solutions, free-form surface solutions, diffractive waveguide solutions, etc., and different solutions have different display performances. Among them, the diffractive waveguide solution has become the mainstream technical solution that many giants are keen to study due to its small size and excellent form. Based on the technical characteristics of diffractive waveguide, it can be applied to various display product forms such as near-eye display, head-up display, floating display, virtual-real fusion space display, etc. For the diffractive waveguide itself, how to improve the display quality is crucial. Summary of the Utility Model

[0003] Based on this, it is necessary to provide a composite waveguide and a display module that not only have high light energy utilization rate but also can achieve display uniformity within the eye box.

[0004] A composite waveguide, the composite waveguide comprising:

[0005] A waveguide substrate;

[0006] An input unit, including a first light control unit and a second light control unit, the first light control unit and the second light control unit are stacked on the same side of the waveguide substrate, or the first light control unit and the second light control unit are respectively arranged on both sides of the waveguide substrate; the first light control unit includes a first light alignment layer and a first liquid crystal grating layer stacked, and the first light alignment layer is arranged close to the waveguide substrate; the second light control unit includes a second light alignment layer and a second liquid crystal grating layer stacked, and the second light alignment layer is arranged close to the waveguide substrate; and an output unit, located on one side of the waveguide substrate, the output unit being a relief grating.

[0007] The present utility model provides a composite waveguide. The coupling-in unit includes an optical modulation unit, which is a stacked structure of a liquid crystal grating layer and an optical alignment layer. It can separately modulate lights of different wavelength bands, thereby realizing color display based on the composite waveguide, and can also be used to realize pupil dilation conduction of different polarized lights. The composite waveguide of the technical solution of the present utility model can maximize the light coupling utilization rate of wide incident angle light through the liquid crystal grating structure design, and can also realize display uniformity within the eye box through the variable structure parameters of the relief grating, which is beneficial to wide application.

[0008] In a feasible implementation, the thickness of the first optical alignment layer and the second optical alignment layer is 5nm - 100nm, and the thickness of the first liquid crystal grating layer and the second liquid crystal grating layer is 200nm - 5000nm.

[0009] In a feasible implementation, the transmission diffraction efficiency of the relief grating of the coupling-out unit increases gradually from the head to the tail.

[0010] In a feasible implementation, the lateral period of the first optical modulation unit is 250nm - 400nm, and the longitudinal period of the first optical modulation unit is 100nm - 200nm; the lateral period of the second optical modulation unit is 400nm - 500nm, and the longitudinal period of the second optical modulation unit is 200nm - 300nm.

[0011] In a feasible implementation, the lateral period of the first optical modulation unit is 400nm - 500nm, and the longitudinal period of the first optical modulation unit is 200nm - 300nm; the lateral period of the second optical modulation unit is 250nm - 400nm, and the longitudinal period of the second optical modulation unit is 100nm - 200nm.

[0012] In a feasible implementation, the first liquid crystal grating layer and the second liquid crystal grating layer are independently selected from one of a reflective liquid crystal grating layer and a transmissive liquid crystal grating layer.

[0013] In a feasible implementation, the first optical modulation unit and the second optical modulation unit are stacked on the same side of the waveguide substrate, and the coupling-in unit further includes a dielectric layer located between the first optical modulation unit and the second optical modulation unit.

[0014] In a feasible implementation, the thickness of the dielectric layer is 100nm - 5000nm, and the dielectric layer is a visible light transparent dielectric layer.

[0015] A display module includes the composite waveguide as described in any one of the above.

[0016] The display module of the present utility model includes the above-mentioned compound waveguide. The compound waveguide of the technical solution of the present utility model can not only maximize the light coupling utilization rate of wide incident angle light through the liquid crystal grating structure design, but also achieve display uniformity within the eyebox through the variable structure parameters of the relief grating, which is beneficial to wide application.

[0017] In a feasible implementation manner, the display module is a near-eye display module, a head-up display module or an augmented reality wearable display module. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the compound waveguide according to the first embodiment of the present utility model;

[0019] Figure 2 Another schematic diagram of the compound waveguide according to the first embodiment of the present utility model;

[0020] Figure 3 Schematic diagram of the reflective liquid crystal grating layer according to an embodiment of the present utility model;

[0021] Figure 4 Schematic diagram of the transmissive liquid crystal grating layer according to an embodiment of the present utility model;

[0022] Figure 5 Schematic diagram of the preparation of the liquid crystal grating layer according to an embodiment of the present utility model;

[0023] Figure 6 Relationship diagram between the first-order diffraction efficiency and the angle of the liquid crystal grating layer according to an embodiment of the present utility model;

[0024] Figure 7 Effect diagram of the compound waveguide according to an embodiment of the present utility model;

[0025] Figure 8 Schematic diagram of the compound waveguide according to the second embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to make the above objects, features and advantages of the present utility model more obvious and understandable, the following detailed description of the specific embodiments of the present utility model is given with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present utility model. However, the present utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present utility model. Therefore, the present utility model is not limited by the specific embodiments disclosed below.

[0027] It should be noted that when an element is referred to as "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this utility model belongs. The terms used in the specification of this utility model herein are only for the purpose of describing specific embodiments and are not intended to limit this utility model. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0029] Please refer to Figure 1 and Figure 2 , the composite waveguide 100 of the first embodiment of the present utility model includes a waveguide substrate 110, an input coupling unit 120 and an output coupling unit 130. Among them, the waveguide substrate 110 is a material with high transparency under visible light, which can be resin, glass, etc., and the waveguide substrate 110 is in a flat or curved surface form. The input coupling unit 120 is used to couple image light into the waveguide substrate 110, and the output coupling unit 130 is used to couple out the image light conducted in the waveguide substrate 110.

[0030] In the composite waveguide 100 of this embodiment, the input coupling unit 120 includes a first light control unit 140 and a second light control unit 150. The first light control unit 140 and the second light control unit 150 are stacked on the same side of the waveguide substrate 110. The first light control unit 140 includes a first light alignment layer 141 and a first liquid crystal grating layer 142 which are stacked, and the first light alignment layer 141 is arranged close to the waveguide substrate 110, and the first liquid crystal grating layer 142 is arranged away from the waveguide substrate 110. The second light control unit 150 includes a second light alignment layer 151 and a second liquid crystal grating layer 152 which are stacked, and the second light alignment layer 151 is arranged close to the waveguide substrate 110, and the second liquid crystal grating layer 152 is arranged away from the waveguide substrate 110. Among them, the first liquid crystal grating layer 142 and the second liquid crystal grating layer 152 can maximize the light coupling utilization rate of wide incident angle light.

[0031] Among them, the first photo - alignment layer 141 is used to align the first liquid crystal grating layer 142 and form a first longitudinal period; then, a first transverse period is formed through orthogonal circular polarization interference for modulating light in the first band; the second photo - alignment layer 151 is used to align the second liquid crystal grating layer 152 and form a second longitudinal period, and then a second transverse period is formed through orthogonal circular polarization interference for modulating light in the second band. In this way, separate modulation of light in different bands can be achieved, realizing color display based on a composite waveguide. By applying the coupling unit 120 of this embodiment, one of the three primary colors can be regulated through the first photo - alignment layer 141 and the first liquid crystal grating layer 142, and the other two of the three primary colors can be regulated through the second photo - alignment layer 151 and the second liquid crystal grating layer 152, thus realizing color display.

[0032] In addition, the composite waveguide 100 of this embodiment can also be used to achieve pupil expansion conduction of different polarized lights. For example, the first liquid crystal grating layer 142 can be used to modulate left - hand circularly polarized light, and the second liquid crystal grating layer 152 can be used to modulate right - hand circularly polarized light. When the incident light has both left - hand polarization and right - hand polarization, separate modulation and separate pupil expansion can be achieved to realize two - dimensional or other forms of pupil expansion conduction.

[0033] In the composite waveguide 100 of this embodiment, the coupling - out unit 130 is located on one side of the waveguide substrate 110. Specifically, the coupling - out unit 130, the first light - regulating unit 140, and the second light - regulating unit 150 are all located on the same side of the waveguide substrate 110; the coupling - out unit 130 is a relief grating. The display uniformity within the eyebox range can be achieved by regulating the structural parameters of the relief grating. Of course, it should be noted that the coupling - out unit 130, the first light - regulating unit 140, and the second light - regulating unit 150 can be located on different sides of the waveguide substrate 110 respectively.

[0034] As Figure 1 and Figure 2 shown, the conduction principle of the composite waveguide 100 of this embodiment is as follows (where the arrow direction is the light conduction direction): The incident polarized light enters the coupling unit 120 covered by the liquid crystal grating and is polarization - modulated by the liquid crystal grating to obtain a first - order diffracted polarized light with a certain diffraction angle. The diffraction angle needs to meet the total internal reflection condition of the optical waveguide and is conducted in the waveguide substrate 110 to the coupling - out unit 130. The transmission diffraction efficiency of the relief grating of the coupling - out unit 130 increases gradually from the head to the tail; among them, the head refers to the end that receives light, and the tail refers to the end that outputs light. The efficiency gradient increase from the head to the tail can be achieved through the design of structural parameters, that is, when the relief grating structure at the head receives the conducted light, the transmission diffraction efficiency is low, and then most of the light is retained and continues to be conducted in the waveguide substrate 110. After the second conduction, the transmission diffraction efficiency is higher than the previous time to ensure that the output light is approximate to the previous time. Repeating this process, relatively uniform light can be transmitted and coupled out by the coupling - out unit 130.

[0035] Further, Figure 1 and Figure 2 the order of modulating light rays is different. Specifically, Figure 1 in [reference], the period parameter of the first light modulation unit 140 is used to modulate blue, and the period parameter of the second light modulation unit 150 is used to modulate green and red; while Figure 2 in [reference], the period parameter of the first light modulation unit 140 is used to modulate green and red, and the period parameter of the second light modulation unit 150 is used to modulate blue.

[0036] For the composite waveguide 100 of this embodiment, the coupling unit 120 includes a light modulation unit, and the light modulation unit is a stacked structure of a liquid crystal grating layer and a photo-alignment layer, which can achieve separate modulation of lights in different bands, so as to realize color display based on the composite waveguide, and can also be used to realize pupil dilation conduction of different polarized lights. The composite waveguide 100 of this embodiment can not only maximize the light coupling utilization rate of wide incident angle light through the liquid crystal grating structure design, but also realize the display uniformity within the eyebox range through the variable structure parameters of the relief grating.

[0037] Based on the foregoing embodiment, the thickness of the first photo-alignment layer 141 is 5 nm to 100 nm, and the thickness of the first liquid crystal grating layer 142 is 200 nm to 5000 nm. Further, the thickness of the first photo-alignment layer 141 can be, but is not limited to, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, and the thickness of the first liquid crystal grating layer 142 can be, but is not limited to, 200 nm, 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 4000 nm, 4500 nm or 5000 nm.

[0038] Based on the foregoing embodiment, the thickness of the second photo-alignment layer 151 is 5 nm to 100 nm, and the thickness of the second liquid crystal grating layer 152 is 200 nm to 5000 nm. Further, the thickness of the second photo-alignment layer 151 can be, but is not limited to, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, and the thickness of the second liquid crystal grating layer 152 can be, but is not limited to, 200 nm, 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 4000 nm, 4500 nm or 5000 nm.

[0039] On the basis of the foregoing embodiments, the lateral period of the first light modulation unit 140 is 250 nm to 400 nm, and the longitudinal period of the first light modulation unit 140 is 100 nm to 200 nm; the lateral period of the second light modulation unit 150 is 400 nm to 500 nm, and the longitudinal period of the second light modulation unit 150 is 200 nm to 300 nm. Herein, the lateral direction in the present invention refers to the direction of the plane where the waveguide substrate 110 is located, and the longitudinal direction refers to the stacking direction of the first light modulation unit 140 and the second light modulation unit 150, that is, the direction perpendicular to the plane of the waveguide substrate 110. In this embodiment, the first light modulation unit 140 is used to modulate blue, and the second light modulation unit 150 is used to modulate green and red. In this embodiment, the lateral period and the longitudinal period of the first light modulation unit 140 and the second light modulation unit 150 can be comprehensively weighed according to the wavelength range to be modulated and the effective refractive index of the material.

[0040] Further, the lateral period of the first light modulation unit 140 can be, but is not limited to, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm or 400 nm, and the longitudinal period of the first light modulation unit 140 can be, but is not limited to, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm or 200 nm. The lateral period of the second light modulation unit 150 can be, but is not limited to, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm or 500 nm, and the longitudinal period of the second light modulation unit 150 can be, but is not limited to, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm or 300 nm.

[0041] On the basis of the foregoing embodiments, the lateral period of the first light modulation unit 140 is 400 nm to 500 nm, and the longitudinal period of the first light modulation unit 140 is 200 nm to 300 nm; the lateral period of the second light modulation unit 150 is 250 nm to 400 nm, and the longitudinal period of the second light modulation unit 150 is 100 nm to 200 nm. In this embodiment, the first light modulation unit 140 is used to modulate green and red, and the second light modulation unit 150 is used to modulate blue. In this embodiment, the lateral period and the longitudinal period of the first light modulation unit 140 and the second light modulation unit 150 can be comprehensively weighed according to the wavelength range to be modulated and the effective refractive index of the material.

[0042] Further, the lateral period of the first light modulation unit 140 can be, but is not limited to, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, or 500 nm, and the longitudinal period of the first light modulation unit 140 can be, but is not limited to, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, or 300 nm. The lateral period of the second light modulation unit 150 can be, but is not limited to, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, or 400 nm, and the longitudinal period of the second light modulation unit 150 can be, but is not limited to, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, or 200 nm.

[0043] Based on the foregoing embodiments, the first liquid crystal grating layer 142 and the second liquid crystal grating layer 152 are independently selected from one of a reflective liquid crystal grating layer and a transmissive liquid crystal grating layer. Please refer to Figure 3 , in one embodiment, the first liquid crystal grating layer 142 or the second liquid crystal grating layer 152 is a reflective liquid crystal grating layer. When the incident circularly polarized light has the same helical direction as the twisted helix direction of the liquid crystal molecules, polarization diffraction occurs, and the polarization property of the diffracted light is the same as that of the incident light. Please refer to Figure 4 , in one embodiment, the first liquid crystal grating layer 142 or the second liquid crystal grating layer 152 is a transmissive liquid crystal grating layer. The principle is similar to that of the reflective liquid crystal grating layer, but the polarization property of the diffracted light in the transmissive liquid crystal grating layer is opposite to that of the incident light.

[0044] Please refer to Figure 5 , the preparation method of the first liquid crystal grating layer 142 or the second liquid crystal grating layer 152 in one embodiment is as follows: The exposure of the liquid crystal grating is similar to traditional two-beam exposure. The difference is that the exposure of the liquid crystal grating requires the interference of left-handed circularly polarized light and right-handed circularly polarized light. The interference light field is linearly polarized and the vibration direction rotates periodically in the transverse direction. Its large period is determined by the angle between the two beams of light; the transverse period is provided by the interference exposure of two orthogonal circularly polarized lights, and the longitudinal period is achieved by doping the liquid crystal with a chiral material, and the longitudinal period is controlled according to the helical twisting force constant of the chiral material.

[0045] The lateral period of the first liquid crystal grating layer 142 or the second liquid crystal grating layer 152 in one embodiment is about 435 nm, and the longitudinal period is about 180 nm. By incident circularly polarized light with a wavelength of 532 nm, the first-order diffraction efficiency is tested, and the test results are as Figure 6 shown. It can be seen from Figure 6 that when the incident angle is between -10° and 10°, the diffraction efficiency is greater than 40%, and when the incident angle is between -7° and 7°, the diffraction efficiency is greater than 70%. Therefore, it can maintain a high efficiency at a certain wide incident angle, which helps to improve the comprehensive light energy utilization rate of the composite waveguide.

[0046] On the basis of the foregoing embodiment, the first light control unit 140 and the second light control unit 150 are stacked on the same side of the waveguide substrate 110, and the coupling unit 120 further includes a dielectric layer located between the first light control unit 140 and the second light control unit 160. The dielectric layer serves to isolate the first light control unit 140 and the second light control unit 150.

[0047] On the basis of the foregoing embodiment, the thickness of the dielectric layer is 100 nm to 5000 nm, and the dielectric layer is a visible light transparent dielectric layer. Further, the thickness of the dielectric layer can be, but is not limited to, 100 nm, 200 nm, 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 4000 nm, 4500 nm or 5000 nm. Further, the material of the dielectric layer is a visible light transparent material, such as optical resin, UV curable, thermosetting glue, etc.

[0048] Figure 7 It is a display effect diagram of the composite waveguide in one embodiment. Figure 7 The original image of the resolution version shown enters from the coupling unit 120 through the optical engine and is received by the coupling-out unit 130. The received display image has a high display resolution and brightness.

[0049] In addition, it should be noted that the structure of the composite waveguide of the present invention is not limited to this. The first light control unit and the second light control unit can also be respectively arranged on both sides of the waveguide substrate.

[0050] Please refer to Figure 8 , the composite waveguide 200 of the second embodiment of the present invention includes a waveguide substrate 210, a coupling unit 220 and a coupling-out unit 230. Among them, the waveguide substrate 210 is a material with high transparency under visible light, which can be resin, glass, etc. The waveguide substrate 210 is in a flat or curved surface form. The coupling unit 220 is used to couple image light into the waveguide substrate 210, and the coupling-out unit 230 is used to couple out the image light conducted in the waveguide substrate 210.

[0051] In the composite waveguide 200 of this embodiment, the coupling-in unit 220 includes a first light control unit 240 and a second light control unit 250. The first light control unit 240 and the second light control unit 250 are oppositely arranged on both sides of the waveguide substrate 210 and are both located in the coupling-in region. The first light control unit 240 includes a first light alignment layer 241 and a first liquid crystal grating layer 242 which are stacked, and the first light alignment layer 241 is arranged close to the waveguide substrate 210, and the first liquid crystal grating layer 242 is arranged away from the waveguide substrate 210. The second light control unit 250 includes a second light alignment layer 251 and a second liquid crystal grating layer 252 which are stacked, and the second light alignment layer 251 is arranged close to the waveguide substrate 210, and the second liquid crystal grating layer 252 is arranged away from the waveguide substrate 210. Among them, the first liquid crystal grating layer 242 and the second liquid crystal grating layer 252 can maximize the light coupling utilization rate of wide incident angle light.

[0052] Among them, the first light alignment layer 241 is used to align the first liquid crystal grating layer 242 and form a first longitudinal period; then, a first transverse period is formed through orthogonal circular polarization interference for modulating light in the first band; the second light alignment layer 251 is used to align the second liquid crystal grating layer 252 and form a second longitudinal period, and then a second transverse period is formed through orthogonal circular polarization interference for modulating light in the second band. In this way, separate modulation of light in different bands can be achieved, and color display based on the composite waveguide can be realized. By applying the coupling-in unit 220 of this embodiment, one of the three primary colors can be regulated by the first light alignment layer 241 and the first liquid crystal grating layer 242, and the other two of the three primary colors can be regulated by the second light alignment layer 251 and the second liquid crystal grating layer 252, so as to realize single-layer color display.

[0053] In addition, the composite waveguide 200 of this embodiment can also be used to realize pupil expansion conduction of different polarized lights. For example, the first liquid crystal grating layer 242 can be used to modulate left-handed circularly polarized light, and the second liquid crystal grating layer 252 can be used to modulate right-handed circularly polarized light. When the incident light has both left-handed polarization and right-handed polarization, separate modulation and separate pupil expansion can be performed to realize two-dimensional or other forms of pupil expansion conduction.

[0054] In the composite waveguide 200 of this embodiment, the coupling-out unit 230 and the first light control unit 240 are located on the same side of the waveguide substrate 210; the coupling-out unit 230 is a relief grating. The display uniformity within the eye box can be achieved by regulating the structural parameters of the relief grating.

[0055] The conduction principle of the composite waveguide 200 in this embodiment is as follows (where the arrow direction is the light conduction direction): The incident polarized light enters the coupling unit 220 covered with a liquid crystal grating, and through the polarization modulation of the liquid crystal grating, a first-order diffracted polarized light with a certain diffraction angle is achieved. The diffraction angle needs to satisfy the total reflection condition of the optical waveguide and is conducted in the waveguide substrate 210 to the coupling-out unit 230. The transmission diffraction efficiency of the relief grating of the coupling-out unit 230 increases gradually from the head to the tail. Here, the head refers to the end that receives light, and the tail refers to the end that outputs light. The efficiency gradient increase from the head to the tail can be achieved through the design of structural parameters. That is, when the relief grating structure at the head receives the conducted light, the transmission diffraction efficiency is low, and most of the light is retained and continues to be conducted in the waveguide substrate 210. After the second conduction, the transmission diffraction efficiency is higher than the previous time to ensure that the output light is similar to the previous time. By repeating this process, relatively uniform light can be transmitted and coupled out by the coupling-out unit 230.

[0056] The present utility model provides a composite waveguide. The coupling unit includes a light control unit, and the light control unit is a stacked structure of a liquid crystal grating layer and a photo-aligned layer, which can separately modulate lights of different bands, thereby realizing color display based on the composite waveguide, and can also be used to realize pupil expansion conduction of different polarized lights. The composite waveguide of the technical solution of the present utility model can not only maximize the light coupling utilization rate of wide incident angle light through the design of the liquid crystal grating structure, but also realize display uniformity within the eye box through variable structural parameters of the relief grating, which is conducive to wide application.

[0057] A display module in one embodiment includes the composite waveguide as described above in any one.

[0058] On the basis of the foregoing embodiments, the display module is a near-eye display module, a head-up display module, or an augmented reality wearable display module. The composite waveguide of the present utility model can be applied in the field of near-eye displays, fitting the shape of glasses, and the eyes can view virtual images superimposed on the real space through the diffractive waveguide; it can be used in the field of in-vehicle head-up displays, combined with the windshield for head-up displays with ultra-long virtual image viewing distances; it can be used in virtual-real fusion space displays, in the form of a desktop space transparent display based on a large-aperture diffractive waveguide. The observer stands in front of the diffractive waveguide and can directly view the virtual images superimposed on the real space behind the transparent screen through the large-aperture diffractive waveguide.

[0059] The display module of the present utility model includes the above composite waveguide. The composite waveguide of the technical solution of the present utility model can not only maximize the light coupling utilization rate of wide incident angle light through the design of the liquid crystal grating structure, but also realize display uniformity within the eye box through variable structural parameters of the relief grating, which is conducive to wide application.

[0060] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0061] The above-described embodiments merely represent several implementation manners of the present utility model. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the utility model patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can still be made, and these all belong to the protection scope of the present utility model. Therefore, the protection scope of the present utility model patent shall be subject to the appended claims.

Claims

1. A composite waveguide, characterized in that: The composite waveguide comprises: waveguide substrate; A coupling unit, comprising a first light regulation unit and a second light regulation unit, wherein the first light regulation unit and the second light regulation unit are stacked on the same side of the waveguide substrate, or the first light regulation unit and the second light regulation unit are respectively arranged on both sides of the waveguide substrate; the first light regulation unit comprises a first light orientation layer and a first liquid crystal grating layer which are stacked, and the first light orientation layer is arranged close to the waveguide substrate; the second light regulation unit comprises a second light orientation layer and a second liquid crystal grating layer which are stacked, and the second light orientation layer is arranged close to the waveguide substrate; and The outcoupling unit is located on one side of the waveguide substrate, and the outcoupling unit is a relief grating.

2. The composite waveguide according to claim 1, characterized in that The thickness of the first photo-alignment layer and the second photo-alignment layer is 5 nm to 100 nm, and the thickness of the first liquid crystal grating layer and the second liquid crystal grating layer is 200 nm to 5000 nm.

3. The composite waveguide according to claim 1, characterized in that The transmission diffraction efficiency of the relief grating of the outcoupling unit increases gradually from the head to the tail.

4. The composite waveguide according to claim 1, characterized in that The lateral period of the first light control unit is 250nm-400nm, and the longitudinal period of the first light control unit is 100nm-200nm; the lateral period of the second light control unit is 400nm-500nm, and the longitudinal period of the second light control unit is 200nm-300nm.

5. The composite waveguide according to claim 1, characterized in that The lateral period of the first light control unit is 400nm-500nm, and the longitudinal period of the first light control unit is 200nm-300nm; the lateral period of the second light control unit is 250nm-400nm, and the longitudinal period of the second light control unit is 100nm-200nm.

6. The composite waveguide according to claim 1, characterized in that The first liquid crystal grating layer and the second liquid crystal grating layer are independently selected from one of a reflective liquid crystal grating layer and a transmissive liquid crystal grating layer.

7. The composite waveguide according to claim 1, characterized in that The first light regulating unit and the second light regulating unit are stacked on the same side of the waveguide substrate, and the coupling unit further includes a dielectric layer located between the first light regulating unit and the second light regulating unit.

8. The composite waveguide according to claim 7, characterized in that The thickness of the dielectric layer is 100 nm to 5000 nm, and the dielectric layer is a visible light transparent dielectric layer.

9. A display module, characterized in that: A composite waveguide comprising the composite waveguide according to any one of claims 1 to 8.

10. The display module according to claim 9, characterized in that: The display module is a near-eye display module, a head-up display module or an augmented reality wearable display module.

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