Volume holographic optical waveguide display device with high uniformity

Abstract

The utility model provides a volume holographic optical waveguide display device with high uniformity. The volume holographic optical waveguide display device comprises an optical-mechanical system, a waveguide system and a control system, the waveguide system comprises a waveguide substrate and a grating structure arranged in the waveguide substrate, and specifically, the grating structure is a switchable Bragg grating array formed by holographic polymer dispersed liquid crystals. According to the utility model, the on-off state of the sub-grating is controlled by applying an electric field through the control electrode, and the sub-grating is controlled to be in a state with the maximum diffraction efficiency when being opened, so that the grating can couple most light energy in one-time diffraction, and the brightness and the uniformity of single-time light emission are improved; meanwhile, different coupling areas are switched in the grating structure through the control system, and the output view field freely moves in different grating areas, so that the same view field effect of opening all grating view fields is constructed, the basically uniform brightness of the whole coupling area is obtained, and the overall light effect utilization rate and the overall light brightness are improved.

Description

Technical Field

[0001] The utility model relates to the field of holographic projection display, and more specifically, to a volume holographic optical waveguide display device with high uniformity. Background Art

[0002] Augmented Reality (AR) technology is a technology that cleverly integrates virtual information with the real world. It can simulate computer-generated virtual information such as text, images, three-dimensional models, music and videos, and apply them to the real world, thereby achieving "enhancement" of the real world. At present, in the practical application of augmented reality technology, the device that realizes AR display technology is usually composed of display devices and optical devices. Among them, optical devices are mainly based on optical waveguide solutions, specifically, including geometric optical waveguides and diffraction optical waveguides; among them, the implementation method of diffraction optical waveguides is to "transport" virtual images to the eyes of people, and at the same time play the role of replicating the exit pupil. Specifically, the diffraction optical waveguide is composed of a planar optical waveguide and multiple diffraction gratings, and the diffraction optical waveguide mainly includes a surface relief grating waveguide (Surface Relief Grating) manufactured by photolithography technology and a volume holographic grating waveguide (Volumetric Holographic Grating) manufactured based on holographic interference technology.

[0003] AR display devices based on volume holographic grating waveguide technology usually have grating structures such as coupling-in grating, folding grating, and coupling-out grating. The light beam projected by the projection optical machine is coupled into the waveguide from the coupling-in grating area after beam expansion and collimation, and is diffracted by the coupling grating to produce a light beam that is totally reflected in the waveguide. The totally reflected light beam can propagate along the waveguide direction in the waveguide until it encounters the folding grating, and then is deflected by the folding grating at a certain angle and propagates along the waveguide in another direction in the waveguide. Finally, it encounters the coupling-out grating, is diffracted by the grating, is coupled out of the waveguide from the waveguide, and is received by the human eye. However, existing AR display devices generally have the problem of poor uniformity. Uniformity is an important characteristic in AR display technology, which usually includes two aspects: color uniformity and brightness uniformity. It plays a decisive role in the accurate reproduction of image color in the eye box or field of view in AR display. In particular, poor brightness uniformity will greatly affect the clarity, stereoscopicity and accuracy of the image, affecting the visual effect. Specifically, due to the existence of the diffraction effect, the image projection screen has a certain field angle range, which will cause the pupil footprint size of the pupil in the waveguide to be different, resulting in striping, thus becoming a source of light field unevenness. Secondly, due to the low diffraction efficiency of the grating, when the propagating light beam in the waveguide encounters a folded grating or a coupling grating, the light beam will propagate and be diffracted multiple times in these gratings, thereby generating pupil expansion to expand the eye box range. However, with the loss of light beam energy each time it is propagated and diffracted, the light energy of each diffraction is different, resulting in uneven light intensity distribution in the entire coupling area, and the actual coupled light brightness is not high.

[0004] In order to balance the light field distribution in the AR display device based on volume holographic grating waveguide technology and reduce its light output non-uniformity, the improvement solutions commonly used in the prior art include: setting an out-coupling grating with changed diffraction efficiency, using a semi-transparent and semi-reflective refractive index modification layer, multiplexing coupling gratings or overlapping gratings, etc. When using an out-coupling grating with changed diffraction efficiency, it usually has a lower diffraction efficiency at one end close to the propagation direction of the light beam, and a higher diffraction efficiency at the other end to balance the out-coupling light beam energy in all areas; using a semi-transparent and semi-reflective refractive index modification layer uses the shift of the pupil to improve the uniformity of the light field in the exit pupil area; multiplexing or overlapping coupling gratings is used to shift the pupil and modulate the grating diffraction efficiency by changing the combined properties of the grating. However, the holographic grating with changed diffraction efficiency needs to be modulated by modulating the refractive index modulation degree of the holographic film material. The methods of changing the refractive index modulation degree of the holographic film material are mainly to change the component ratio of the holographic material in different areas or to change the exposure dose of the grating in different areas. No matter which method is used, it is impossible to achieve the gradual effect of the diffraction efficiency in the propagation direction of the grating and there is still a certain non-uniformity. Moreover, these methods usually require special processing technology and complex processing procedures. Adding a refractive index modification layer with semi-transparent and semi-reflective characteristics in the waveguide or multiplexing and overlapping gratings will greatly increase the difficulty of processing the entire waveguide and increase the influence of additional stray light. Utility Model Content

[0005] The utility model aims to overcome at least one defect of the above-mentioned prior art, and provides a volume holographic optical waveguide display device with high uniformity, thereby improving the brightness and uniformity of the holographic grating optical waveguide.

[0006] The technical solution adopted by the utility model is: to provide a high-uniform volume holographic optical waveguide display device, including an optical-mechanical system, a waveguide system and a control system; the optical-mechanical system is used to emit a collimated light source; the waveguide system includes a waveguide substrate and a grating structure arranged in the waveguide substrate, the grating structure is used to guide the collimated light source to enter the waveguide substrate for propagation and modulate the collimated light source, and couple the modulated light source out to the human eye;

[0007] The grating structure is a switchable Bragg grating composed of holographic polymer dispersed liquid crystal, and the grating structure is a grating array formed by multiple sub-gratings; the control system is used to switch the coupling area of ​​the grating structure, and the control system includes a plurality of control electrodes, which are installed on the waveguide substrate and are used to switch the sub-gratings on or off.

[0008] In the present technical solution, the grating structure in the volume holographic optical waveguide display device is a switchable Bragg grating composed of holographic polymer dispersed liquid crystal, wherein the holographic polymer dispersed liquid crystal is a grating formed by periodic arrangement of a polymer-rich phase and a liquid crystal-rich phase through polymerization-induced phase separation under coherent laser. Since the liquid crystal material molecules themselves have the characteristic of deflecting the direction of the optical axis under the action of an electric field, the liquid crystal material molecules can change their direction under the action of an electric field and change the refractive index of the liquid crystal. Therefore, this characteristic can be used to modulate the refractive index modulation degree of the holographic polymer dispersed liquid crystal material grating or for the switching of the grating, which is also called a switchable Bragg grating (SBG). In the technical solution, the grating structure in the volume holographic optical waveguide display device is set as a switchable Bragg grating, so that the grating structure to which the electric field is applied can produce optical axis deflection, and the control system is used to control and select the coupling area in the grating structure that can be used for the collimated light source to pass; specifically, the grating structure is set to be a grating array formed by multiple sub-gratings, and the control system includes a number of control electrodes, which are installed on the waveguide substrate, and can switch the sub-gratings on or off in the dimension of the sub-gratings, and when some sub-gratings are turned on, the remaining sub-gratings are turned off, thereby realizing the selection of the coupling area in the grating structure. Furthermore, by controlling the coupling area on the grating structure in an electrically controlled manner, different coupling areas can be conveniently and quickly switched in the grating structure through the control system, and the output field of view can be freely moved in different grating areas, thereby constructing the same field of view effect as when all grating fields of view are turned on, thereby realizing the pupil expansion and exit pupil effects of the original grating structure design. Secondly, the control electrode controls the switching state of the sub-grating only by applying an electric field, which can conveniently define and maintain the sub-grating in a state of maximum diffraction efficiency when it is turned on, so that when the collimated light source passes through the turned-on sub-grating in the grating array, the turned-on sub-grating can maintain the highest diffraction efficiency. Therefore, the collimated light source can couple out most of the light energy in one diffraction, thereby improving the brightness and uniformity of a single light output; further, by quickly switching the coupling area through the control system, all grating areas can have the same light output effect, which also means the same brightness and angle uniformity. At the same time, since each part of the sub-grating has the maximum diffraction efficiency, the utilization rate of the light beam is maximized, the overall brightness of the light beam is improved, and the high brightness and high uniformity of the single light output are continued in the full output field of view, a more balanced light field distribution is constructed, and the overall display effect is improved. Furthermore, since each sub-grating is configured to have the highest diffraction efficiency, all gratings can have the same optical properties, which greatly reduces the complexity and difficulty of grating production. The same production process can be used to ensure the consistency of all characteristics of the grating structure, which not only improves production efficiency, but also further improves the performance of the grating structure.

[0009] Furthermore, the sub-grating is modulated individually by the control electrode, and the size of the sub-grating along the arrangement direction of the grating array is not greater than the size of a pupil. In this technical solution, through the corresponding connection and individual modulation between the sub-grating and the control electrode, the coupling area selection based on the dimension of a single sub-grating can be accurately and conveniently realized; at the same time, by setting the size of the sub-grating along the arrangement direction of the grating array to be not greater than the size of a pupil, the grating area selected by the control system to be opened at a single time is equal to or slightly greater than the size of the pupil, while keeping other gratings in a closed state, so that in the actual working process, the light beam coupled out at a single time is more concentrated and has a high diffraction efficiency, thereby improving the brightness and uniformity of the single light output.

[0010] Optionally, the control electrodes are arranged in pairs on the outer plane of the waveguide substrate and correspond in parallel to the sub-gratings modulated by them; and / or, the control electrodes are arranged in pairs in the waveguide substrate and correspond in parallel to the sub-gratings modulated by them. In the present technical solution, the control electrodes are arranged in pairs and in parallel on both sides of the pupil of the desired modulated sub-grating, and are used to construct an electric field in the sub-grating so as to accurately control the pupil steering of the sub-grating, thereby realizing the opening or closing of the sub-grating. Preferably, the setting position of the control electrode overlaps with the position where the light beam passes near the sub-grating, and the control electrode is set to use a transparent electrode with high transmittance to facilitate the coupling in or out of the light beam. Further preferably, the control electrode uses ITO conductive glass to improve the transparency of the outcoupling area.

[0011] Furthermore, in order to improve the diffraction efficiency of the grating structure and increase the field of view, the grating array can be selectively set as a one-dimensional array or a two-dimensional array. Preferably, the sub-grating is one or more of an overlapping grating or a multiplexed grating, and the uniformity and angular uniformity of the local grating are improved by using a multiplexed grating, an overlapping grating or a smaller grating array.

[0012] As one embodiment, the grating structure includes at least a coupling-in grating and a coupling-out grating. The collimated light source enters the waveguide substrate through the coupling-in grating and propagates along a first propagation direction in the waveguide substrate, and then is expanded by the coupling-out grating and coupled out to the human eye.

[0013] Furthermore, the outcoupling grating is an outcoupling grating array formed by a plurality of outcoupling sub-gratings, and the outcoupling grating array is arranged along the first propagation direction.

[0014] In this embodiment, the optical-mechanical system expands and collimates the image pixel point light source and then couples it into the waveguide substrate. The light beam entering the waveguide substrate is coupled into the grating diffraction to generate a first-order diffraction wave and can propagate in the waveguide by total internal reflection. The coupling grating is set to the highest diffraction efficiency so that most of the light coupled into the waveguide is diffracted into first-order diffraction light and propagates in the waveguide; the diffracted wave propagates in the waveguide along the first propagation direction toward the coupling-out grating by total internal reflection until it encounters the coupling-out grating and undergoes a second diffraction with the coupling-out grating. The diffraction diffracts the light beam that originally propagated by total reflection in the waveguide into a light beam that propagates toward the waveguide surface and is finally coupled out of the waveguide substrate to enter the human eye for imaging. At the same time, the light beam is dilated in the first propagation direction through the action of the coupling-out grating, thereby expanding the exit pupil diameter and field of view of the volume holographic optical waveguide display device. Furthermore, the out-coupling grating is a out-coupling grating array formed by a plurality of out-coupling sub-gratings, and the out-coupling grating array is arranged along the first propagation direction, so that the light beam produces pupil expansion in the first propagation direction. Furthermore, the out-coupling sub-grating is switched on or off by controlling the electrode, and then the out-coupling area on the out-coupling grating array is selected, thereby reducing the area of ​​single light beam coupling out, and improving the diffraction efficiency and brightness of the light beam. At the same time, the out-coupling area on the out-coupling grating is switched by the control system to cover all the out-coupling grating arrays, thereby achieving the exit pupil diameter and field of view effect of the original out-coupling grating array design.

[0015] As one of the embodiments, the grating structure at least includes a coupling-in grating, a folded grating and a coupling-out grating. The collimated light source enters the waveguide substrate through the coupling-in grating and propagates toward the folded grating along a second propagation direction; then, after a pupil expansion from the folded grating, it propagates toward the coupling-out grating along a third propagation direction, and after a pupil expansion from the coupling-out grating for a second time, it is coupled out to the human eye.

[0016] Further, the folded grating is a folded grating array formed by a plurality of folded sub-gratings, and the folded grating array propagates along the second propagation direction; and / or, the outcoupling grating is an outcoupling grating array formed by a plurality of outcoupling sub-gratings, and the outcoupling grating array is arranged along the third propagation direction.

[0017] In this embodiment, the optical-mechanical system expands and collimates the image pixel point light source and then couples it into the waveguide substrate. The light beam entering the waveguide substrate is coupled into the grating diffraction to generate a first-order diffraction wave and can propagate in the waveguide by total internal reflection. The coupling grating is set to the highest diffraction efficiency so that most of the light coupled into the waveguide is diffracted into first-order diffraction light and propagates in the waveguide; the diffracted wave propagates in the waveguide along the second propagation direction toward the folded grating by total internal reflection until it encounters the folded grating and reacts with the folded grating to cause a second diffraction to cause the light beam to turn at a certain angle. The action of the folded grating causes the incident light beam to expand once in the initial propagation direction. The light beam after the second diffraction continues to propagate in the waveguide plane by total internal reflection toward the outcoupling grating along the third propagation direction until it encounters the outcoupling grating and undergoes a third diffraction with the outcoupling grating. The diffraction diffracts the light beam originally propagated by total reflection in the waveguide into a light beam propagating toward the waveguide surface and finally coupled out of the waveguide substrate to enter the human eye for imaging. At the same time, the light beam also generates a secondary pupil expansion in the third propagation direction through the action of the outcoupling grating, and the exit pupil diameter and field of view of the volume holographic optical waveguide display device are expanded through the two-dimensional pupil expansion scheme. Preferably, the folded grating and the outcoupling grating can both be controlled by the control system to switch the coupling areas on the folded grating and the outcoupling grating, thereby realizing the exit pupil diameter of the original outcoupling grating array design in the second propagation direction and the third propagation direction, and improving the diffraction efficiency and brightness of the light beam when propagating in the waveguide plane, and improving the light uniformity and field of view effect.

[0018] The beneficial effects of the utility model are:

[0019] 1. By controlling the switching state of the sub-grating by applying an electric field through the control electrode, the sub-grating is conveniently defined and maintained in a state of maximum diffraction efficiency when it is turned on, so that when the collimated light source passes through the turned-on sub-grating in the grating array, the turned-on sub-grating can maintain the highest diffraction efficiency, so that the collimated light source can couple out most of the light energy in one diffraction, thereby improving the brightness and uniformity of a single light output; further, through the control system, different coupling areas are conveniently and quickly switched in the grating structure, and the output field of view is freely moved in different grating areas, thereby constructing the same field of view effect as when all grating fields of view are turned on, thereby realizing the pupil expansion and exit pupil effects of the original grating structure design, and continuing the high brightness and high uniformity of a single light output, obtaining a basically uniform brightness in the entire coupling area, improving the overall light efficiency utilization rate, and improving the overall brightness.

[0020] 2. By configuring the sub-gratings to have the highest diffraction efficiency, all sub-gratings can have the same optical characteristics, which can be achieved through single exposure or repetitive processes, thereby greatly reducing the complexity and difficulty of grating structure production. The same production process can be used to ensure the consistency of all characteristics of the grating structure, which not only improves production efficiency but also further improves the performance of the grating structure. At the same time, there is no need to introduce redundant optical elements in the holographic optical waveguide display device, and no additional stray light will be introduced, so it has both good static and dynamic characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic cross-section of a switchable Bragg grating composed of holographic polymer dispersed liquid crystal.

[0022] Figure 2 Schematic plan view of a waveguide system using a one-dimensional grating array for outcoupling gratings.

[0023] Figure 3 Schematic plan view of a waveguide system using a two-dimensional grating array for outcoupling gratings.

[0024] Figure 4 A cross-sectional schematic diagram of a waveguide system in which control electrodes are arranged on both sides of the surface of a waveguide substrate.

[0025] Figure 5 This is a cross-sectional schematic diagram of a waveguide system in which control electrodes are arranged inside a waveguide substrate and on both sides of a grating structure.

[0026] Figure 6 Schematic plan view of a waveguide system using multiplexing gratings for outcoupling grating arrays.

[0027] Figure 7 Schematic plan view of a waveguide system using overlapping gratings for outcoupling grating arrays.

[0028] Figure 8 A plan view of a two-dimensional pupil expansion waveguide system. DETAILED DESCRIPTION

[0029] The drawings of the present invention are only used for illustrative purposes and cannot be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0030] The utility model provides a highly uniform volume holographic optical waveguide display device, including an optomechanical system, a waveguide system and a control system; the optomechanical system emits a collimated light source into the waveguide system, the waveguide system includes a waveguide substrate and a grating structure arranged in the waveguide substrate, the grating structure is used to guide the collimated light source to enter the waveguide substrate for propagation and modulate the collimated light source, and couple the modulated light source out to the human eye. Specifically, the waveguide substrate is composed of a single layer or multiple layers of transparent glass, which constructs a space for light source modulation; the grating structure used is a switchable Bragg grating composed of holographic polymer dispersed liquid crystals. Since the holographic polymer dispersed liquid crystals are formed by polymerization-induced phase separation under coherent lasers and are composed of a periodic arrangement of a polymer-rich phase and a liquid crystal-rich phase, a grating structure with desired parameters can be formed conveniently and economically by changing the spatial energy distribution of the exposure light field of the holographic polymer dispersed liquid crystals. At the same time, since the liquid crystal itself has the characteristic of deflecting the direction of the optical axis under the action of an electric field, such as Figure 1 As shown, the direction of the optical axis of the liquid crystal material molecule 302 can change with the voltage state applied by the paired control electrodes 301. When there is no voltage, the optical axis of the liquid crystal material molecule 302 points vertically to the polymer material 303. At this time, the liquid crystal material molecule 302 has the largest refractive index in the horizontal direction. When a certain voltage is applied by the control electrode 301, the optical axis of the liquid crystal material molecule 302 turns and can be parallel to the polymer material 303. At this time, the refractive index of the liquid crystal material molecule 302 in the horizontal direction is the lowest and close to the refractive index of the polymer material 303. Further, the refractive index difference between the liquid crystal material molecule 302 and the polymer material 303 can be adjusted by the magnitude of the applied voltage, thereby adjusting the diffraction efficiency of the grating. The switchable Bragg grating composed of holographic polymer dispersed liquid crystal can realize the turning of the pupil by applying an electric field on both sides of the pupil, thereby modulating the transmittance of the light beam relative to the grating, realizing the opening or closing of the grating, and realizing the directional selection of the light beam outcoupling area. Furthermore, the grating structure is set to form a grating array composed of multiple sub-gratings, and at the same time, the control system includes a plurality of control electrodes 301, which are respectively used to switch the sub-gratings on or off, which can not only realize the directional selection of the light beam outcoupling area, but also facilitate the optimal diffraction efficiency of the modulation grating, and improve the brightness and uniformity of the light beam when it is emitted. At the same time, the control system can also switch the required coupling area on the grating structure in a directional manner, and conveniently and quickly move the output field of view freely in different grating areas, thereby constructing the same field of view effect as when all grating fields of view are turned on, which not only realizes the pupil expansion and exit pupil effects of the original grating structure design, but also makes the full field of view light effect composed of multiple light beams emitted, thereby improving the brightness and uniformity of the full field of view light effect.

[0031] In a specific embodiment, the sub-gratings in the grating structure correspond one-to-one to the control electrode 301 and are modulated individually by it. Each sub-grating can be physically divided or can be physically non-divided and defined by the area of ​​the control electrode 301, and each sub-grating can be individually modulated to any diffraction efficiency between the maximum diffraction efficiency and the zero diffraction efficiency.

[0032] Preferably, the size of the sub-grating along the arrangement direction of the grating array is not larger than the size of a pupil, so that the grating area that is selectively opened at a single time is equal to or slightly larger than the size of the pupil, so that the single coupled light beam is more concentrated and has high diffraction efficiency, thereby improving the brightness and uniformity of the single light output.

[0033] Since the sub-gratings in the grating structure correspond to the control electrodes 301 one by one and are modulated individually by the control electrodes 301, each control electrode 301 can be individually connected to a control system, specifically, a voltage controller, and individually modulate the diffraction efficiency of each sub-grating; therefore, the control electrodes 301 form an electrode array corresponding to the grating array modulated by them, and the area of ​​the electrode array should be greater than or equal to the area of ​​the grating region to be modulated, so as to achieve stable modulation of the grating array. Specifically, in order to facilitate the corresponding modulation between the control electrodes 301 and the sub-gratings, while maximizing the realization of the electrical control function and avoiding interference with the function of the waveguide system itself, the control electrodes 301 should be arranged in pairs on the waveguide substrate 101, and correspond in parallel to the sub-gratings modulated by them.

[0034] As an implementation method, Figure 2 As shown, the grating structure includes a coupling-in grating 102 and a coupling-out grating 103, and control electrodes 301 are arranged on the two side surfaces of the waveguide region corresponding to the coupling-out grating 103. The control electrodes 301 are arranged in pairs and correspond to the grating structure modulated by them in parallel. The control electrodes 301 are transparent electrodes, preferably, made of ITO transparent conductive glass.

[0035] As another embodiment, Figure 3 As shown, the control electrode 301 is arranged inside the waveguide substrate 101 and on both sides of the outcoupling grating 103; the control electrode 301 is a transparent electrode, preferably made of ITO transparent conductive glass. Optionally, the control electrode 301 may or may not be in contact with the modulated grating structure.

[0036] In a specific embodiment, the grating structure at least includes a coupling-in grating 102 and a coupling-out grating 103. In order to improve the diffraction efficiency of the grating structure and increase the field of view, the grating structure can be a one-dimensional grating array or a two-dimensional grating array composed of sub-gratings. In order to improve the uniformity and angular uniformity of the local grating, multiplexed gratings, overlapping gratings or smaller grating arrays can also be used.

[0037] In one embodiment, the grating structure includes an in-coupled grating 102 and an out-coupled grating 103, and the out-coupled grating 103 is a one-dimensional grating array formed by a plurality of out-coupled sub-gratings 1031. Figure 4 As shown, the waveguide system includes a waveguide substrate 101 and a grating structure arranged in the waveguide substrate 101; wherein the waveguide substrate 101 is composed of a single layer or multiple layers of transparent glass, the grating structure includes an in-coupling grating 102 and an out-coupling grating 103, and a collimated light source enters the waveguide substrate 101 through the in-coupling grating 102, generating a diffracted light beam that can be totally internally reflected in the waveguide substrate 101; the diffracted light beam propagates along a first propagation direction 201 in the waveguide substrate 101, and then is diffracted and coupled out of the waveguide substrate 101 by the out-coupling grating 103, and the pupil is expanded and projected to the human eye. The one-dimensional grating array formed by the out-coupling sub-grating 10311 is arranged along the first propagation direction 201.

[0038] As another embodiment, Figure 5 As shown, the grating structure includes an in-coupling grating 102 and an out-coupling grating 103 , and the out-coupling grating 103 is a two-dimensional grating array formed by a plurality of out-coupling sub-gratings 1031 .

[0039] As another embodiment, Figure 6 As shown, the grating structure includes an in-coupled grating 102 and an out-coupled grating 103, wherein the out-coupled grating 103 is a one-dimensional or two-dimensional out-coupled grating array, and the out-coupled grating array adopts a multiplexed structure grating to balance the light field uniformity, angle uniformity and color uniformity within the grating unit. Preferably, each sub-grating in the out-coupled grating array can adopt the same grating structure or different grating structures.

[0040] As another embodiment, Figure 7 As shown, the grating structure includes a coupling-in grating 102 and a coupling-out grating 103, wherein the coupling-out grating 103 is a one-dimensional or two-dimensional coupling-out grating array, the coupling-out grating array adopts overlapping gratings, and the coupling-out grating array has multiple grating layers in the waveguide thickness direction; optionally, the grating arrays of different layers can be the same array structure or different array structures; the gratings of different layers can have a certain displacement in the horizontal direction or no displacement; the gratings of different layers can have different grating structures, including multiplexed gratings, to compensate for the light field uniformity, angle uniformity and color uniformity in the grating; wherein the gratings of different layers can be controlled individually by a control unit or combined and controlled.

[0041] As another embodiment, the grating structure further includes a folded grating 104, such as Figure 8As shown, the grating structure includes a coupling-in grating 102, a folded grating 104 and a coupling-out grating 103. Preferably, the waveguide system includes a switchable folded grating array and a switchable coupling-out grating array, providing a two-dimensional pupil expansion waveguide system; wherein the folded grating 104 and the coupling-out grating 103 both have array structures, and both can be one-dimensional arrays or two-dimensional arrays. Consistent with the aforementioned embodiment, the switchable folded grating array and the switchable coupling-out grating array can also have the aforementioned various grating structure configurations, including multiplexed structure gratings or overlapping gratings, etc., so that the switchable folded grating array and the switchable coupling-out grating array can constitute a two-dimensional switching mode to reflect the dynamic characteristics of the waveguide display.

[0042] Obviously, the above embodiments of the utility model are only examples for clearly explaining the technical solution of the utility model, and are not intended to limit the specific implementation methods of the utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the utility model shall be included in the protection scope of the claims of the utility model.

Claims

1. A high uniformity volume holographic optical waveguide display device, characterized in that: It comprises an optomechanical system, a waveguide system and a control system; the optomechanical system is used to emit a collimated light source; the waveguide system comprises a waveguide substrate and a grating structure arranged in the waveguide substrate, the grating structure is used to guide the collimated light source to propagate into the waveguide substrate and modulate the collimated light source, and couple the modulated light source out of the waveguide substrate; The grating structure is a switchable Bragg grating composed of holographic polymer dispersed liquid crystal, and the grating structure is a grating array formed by multiple sub-gratings; the control system is used to switch the coupling area of ​​the grating structure, and the control system includes a plurality of control electrodes, which are installed on the waveguide substrate and are used to switch the sub-gratings on or off.

2. The device according to claim 1, characterized in that The sub-grating is modulated individually by the control electrode, and the size of the sub-grating along the arrangement direction of the grating array is not greater than the size of a pupil.

3. The device according to claim 2, characterized in that The control electrodes are arranged in pairs on the outer plane of the waveguide substrate and correspond to the sub-gratings modulated by them in parallel; and / or, the control electrodes are arranged in pairs in the waveguide substrate and correspond to the sub-gratings modulated by them in parallel.

4. The device according to claim 3, characterized in that The control electrode is a transparent electrode.

5. The device according to claim 1, characterized in that The grating array is a one-dimensional array or a two-dimensional array.

6. The device according to claim 1, characterized in that The sub-gratings are one or more of overlapping gratings and multiplexed gratings.

7. The device according to any one of claims 1 to 6, characterized in that: The grating structure at least includes a coupling-in grating and a coupling-out grating. The collimated light source enters the waveguide substrate through the coupling-in grating, propagates along a first propagation direction in the waveguide substrate, and then is expanded by the coupling-out grating and coupled out to the human eye.

8. The device according to claim 7, characterized in that The outcoupling grating is an outcoupling grating array formed by a plurality of outcoupling sub-gratings, and the outcoupling grating array is arranged along the first propagation direction.

9. The device according to claim 8, characterized in that The grating structure also includes a folded grating. The collimated light source enters the waveguide substrate through the coupling-in grating and propagates toward the folded grating along a second propagation direction. Then, after a pupil expansion from the folded grating, the collimated light source propagates toward the coupling-out grating along a third propagation direction, and after a pupil expansion from the coupling-out grating for a second time, the collimated light source is coupled out to the human eye.

10. The device according to claim 9, characterized in that The folded grating is a folded grating array formed by a plurality of folded sub-gratings, and the folded grating array propagates along the second propagation direction; and / or, the outcoupling grating is an outcoupling grating array formed by a plurality of outcoupling sub-gratings, and the outcoupling grating array is arranged along the third propagation direction.

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