Diffraction optical waveguide and augmented reality display device

Abstract

The invention discloses a diffraction optical waveguide and augmented reality display equipment, and the diffraction optical waveguide comprises a waveguide substrate, the waveguide substrate comprises a first surface and a second surface which are parallel to each other, and the first surface and / or the second surface are / is provided with a coupling-in grating, a turning grating and a coupling-out grating; wherein the turning grating comprises a plurality of turning sub-gratings, and the turning sub-gratings are switchable gratings so as to be switched between a diffraction state and a non-diffraction state; when an optical machine is lightened, the turning sub-gratings are sequentially switched to be in a diffraction state, only one turning sub-grating is in the diffraction state at the same moment, and the sum of the time when the turning sub-gratings are in the diffraction state is not larger than the visual persistence time of human eyes. According to the technical scheme provided by the invention, the unexpected interference effect can be improved or even eliminated, so that the display effect of the diffraction optical waveguide is improved.

Description

Technical Field

[0001] The present application relates to the field of augmented reality, and in particular to a diffraction optical waveguide and an augmented reality display device. Background Art

[0002] Augmented reality is a technology that integrates the real world and virtual information. The augmented reality display system usually includes a micro projector and an optical display screen. The micro projector provides virtual display content for the augmented reality display system and projects it into the human eye through the optical display screen. The optical display screen is usually a transparent optical component, so that users can also see the real world through the optical display screen.

[0003] Diffraction waveguide is a way to realize optical display screen. Grating structure is usually used to expand the exit pupil. There will be multiple expansion paths when realizing the exit pupil expansion, which will then generate a large number of light rays with equal optical path differences transmitted in the same direction. These light rays will produce constructive interference or destructive interference when coupled out to the human eye, resulting in light and dark stripes in the display image, which greatly affects the display effect. Summary of the invention

[0004] The embodiments of the present application provide a diffractive optical waveguide and an augmented reality display device, which can improve or even eliminate undesirable interference effects, thereby enhancing the display effect of the diffractive optical waveguide.

[0005] A diffractive optical waveguide, comprising:

[0006] A waveguide substrate, the waveguide substrate comprises a first surface and a second surface parallel to each other, an in-coupling grating, a turning grating and an out-coupling grating are arranged on the first surface and / or the second surface; wherein the turning grating comprises a plurality of turning sub-gratings, and the turning sub-gratings are switchable gratings for switching between a diffraction state and a non-diffraction state; when the optical engine is turned on, the turning sub-gratings are switched to a diffraction state in sequence, and at the same time, only one of the turning sub-gratings is in the diffraction state, and the sum of the time that the turning sub-gratings are in the diffraction state is not greater than the visual persistence time of the human eye.

[0007] In practice, the boundary lines between the turning sub-gratings are substantially perpendicular to the transmission direction of the light after the light is diffracted and deflected by the turning sub-gratings.

[0008] In practice, the width of the turn sub-grating is smaller than the total reflection step length of the light in the waveguide substrate.

[0009] In practice, the turning grating is a liquid crystal grating and includes at least a first electrode layer, a liquid crystal layer and a second electrode layer along a direction away from the surface of the waveguide substrate; wherein the first electrode layer includes a plurality of discrete strip electrodes, the second electrode layer is a continuous electrode, and the area corresponding to a single strip electrode forms a turning sub-grating that can switch between a diffraction state and a non-diffraction state.

[0010] In practice, the response time of the liquid crystal layer is related to the rotational viscosity, thickness, dielectric constant and elastic constant of the liquid crystal layer.

[0011] Practically, the control voltage of the strip electrodes varies with time to reduce the response time of the liquid crystal layer; wherein the control voltage in the rising phase is greater than the target voltage, the control voltage in the holding phase is equal to the target voltage, and the control voltage in the falling phase is less than the target voltage.

[0012] It is feasible that the target voltages corresponding to at least two of the strip electrodes are different, so that the equivalent refractive indexes of the turning sub-gratings corresponding to at least two of the strip electrodes are different, so that the diffraction efficiency of the turning grating gradually increases along the transmission direction after the light is coupled into the waveguide substrate.

[0013] An augmented reality display device, comprising a diffractive optical waveguide and an optical machine as described in any one of the above items.

[0014] Practically, the optical machine sequentially illuminates light with different fields of view, and the field of view of the light illuminated at any time matches the field of view of the light that can be deflected by the folding sub-grating currently in the diffraction state.

[0015] In practice, the field of view of the optical machine in the target direction is divided into a plurality of field of view subareas, and there is a partial overlap between any two adjacent field of view subareas; the target direction is the transmission direction of the light after being diffracted and deflected by the grating.

[0016] The present application provides a diffraction optical waveguide and an augmented reality display device, wherein the turning grating of the diffraction optical waveguide includes a plurality of turning sub-gratings, which can be switched between a diffraction state and a non-diffraction state; when the optical machine is turned on, the turning sub-gratings are switched to the diffraction state in sequence, and at the same time, there is only one turning sub-grating in the diffraction state; in this way, only a part of the turning grating is in the diffraction state at a time, and only a small amount of light undergoes secondary diffraction and deflects again after the diffraction deflection direction, and even no light undergoes secondary diffraction, thereby improving or even eliminating the undesirable interference effect and enhancing the display effect of the diffraction optical waveguide. Moreover, the sum of the time that all the turning sub-gratings are in the diffraction state is not greater than the visual persistence time of the human eye, that is, the image observed by the human eye through the diffraction optical waveguide is a complete image, and the visual experience of the user can also be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of light propagation of a diffraction light waveguide provided in the prior art;

[0019] Figure 2 A schematic diagram of light propagation of a diffractive optical waveguide provided in an embodiment of the present application;

[0020] Figure 3 A structural diagram of a diffraction optical waveguide provided in an embodiment of the present application Figure 1 ;

[0021] Figure 4 A structural diagram of a diffraction optical waveguide provided in an embodiment of the present application Figure 2 ;

[0022] Figure 5 A structural diagram of a diffraction optical waveguide provided in an embodiment of the present application Figure 3 ;

[0023] Figure 6 A schematic diagram of the structure of another diffractive optical waveguide provided in an embodiment of the present application;

[0024] Figure ID:

[0025] 100: diffractive optical waveguide;

[0026] 110: waveguide substrate; 111: first surface; 112: second surface;

[0027] 120: coupling grating;

[0028] 130: turning grating; 131: first electrode layer; 1311: strip electrode; 132: liquid crystal layer; 133: second electrode layer; 1300: turning sub-grating;

[0029] 140: Decoupled grating. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0032] In the prior art, reference Figure 1 In the existing diffraction waveguide architecture, light is diffracted by the coupling-in grating 120 and enters the waveguide substrate 110, and is transmitted toward the turning grating 130, and then is deflected by the turning grating 130 to be transmitted toward the coupling-out grating 140, and then coupled out of the waveguide substrate 110 by the coupling-out grating 140 and enters the human eye. When the light is transmitted to the turning grating 130 and diffracted at position A, part of the light (1-1) continues to be transmitted along the original direction and continues to be diffracted at position B, and part of the light (1-2) is deflected to be transmitted to the coupling-out grating 140 and continues to be diffracted at position C. After the light (1-1) is diffracted at treatment B, part of the light (1-1-1) continues to be transmitted along the original direction, and part of the light (1-1-2) is deflected to the outcoupling grating 140 for transmission, and continues to be diffracted at position D; after the light (1-2) is diffracted at treatment C, part of the light (1-2-1) continues to be transmitted along the original direction, and part of the light (1-2-2) is deflected to the original direction for transmission, and continues to be diffracted at position D; at this time, there are two light rays: light (1-1-2) and light (1-2-2) converge at position B, and constructive interference or destructive interference will occur, resulting in light and dark intervals in the light transmitted to the outcoupling grating 140, which appears as dark lines at a partial field of view angle during outcoupling, affecting the imaging effect.

[0033] In order to solve the above problems, improve or even eliminate the undesired interference effect, and enhance the display effect of the diffractive optical waveguide, the present application provides a diffractive optical waveguide and an augmented reality display device including the same.

[0034] The diffraction optical waveguide provided in the present application includes: a waveguide substrate, the waveguide substrate includes a first surface and a second surface parallel to each other, and an in-coupling grating, a turning grating and an out-coupling grating are arranged on the first surface and / or the second surface; wherein the turning grating includes a plurality of turning sub-gratings, and the turning sub-gratings are switchable gratings to switch between a diffraction state and a non-diffraction state; when the optical engine is turned on, the turning sub-gratings are switched to the diffraction state in sequence, and at the same time, there is only one turning sub-grating in the diffraction state, and the sum of the time when the turning sub-gratings are in the diffraction state is not greater than the visual persistence time of the human eye.

[0035] First, the present application defines that the transmission direction of the light after being coupled into the waveguide substrate by the coupling grating and then transmitted toward the turning grating is the first direction, and the transmission direction after being diffracted and deflected by the turning grating is the second direction.

[0036] Specifically, refer to Figure 2 , which shows a schematic diagram of light propagation of a diffractive optical waveguide provided by an embodiment of the present application. Specifically, the diffractive optical waveguide 100 includes a waveguide substrate 110, and the waveguide substrate 110 includes a first surface 111 and a second surface 112 ( Figure 2 (not shown); a coupling-in grating 120, a turning grating 130 and a coupling-out grating 140 are arranged on the first surface 111, and the turning grating 130 includes a plurality of turning sub-gratings 1300. After the optical engine is turned on, the turning sub-gratings 1300 are switched to the diffraction state in sequence, and at the same time, there is only one turning sub-grating 1300 in the diffraction state. When the size of the turning sub-grating 1300 in the light deflection direction (i.e., the second direction) meets certain conditions, when the light is diffracted and deflected in the turning sub-grating 1300 in the diffraction state (such as position A and position B) and transmitted along the second direction, only a small amount of light will be diffracted again, or even no light will be diffracted again, so that secondary diffraction can be reduced or even avoided to improve or even eliminate undesirable interference effects.

[0037] It can be understood that after the light enters the waveguide substrate, when it is totally reflected and transmitted in the waveguide substrate, if there is a grating at the total reflection point, diffraction will occur at this position. In the present application, the starting point of the inventive concept is to prevent or minimize secondary diffraction of the light at the turning grating to improve or even eliminate the undesirable interference effect, thereby dividing the turning grating into a number of turning sub-gratings, and designing the turning sub-gratings as switchable gratings that can switch between a diffraction state and a non-diffraction state, so that when the optical machine is lit and imaging is required, each turning sub-grating of the turning grating continuously switches to a diffraction state in a time sequence until imaging is completed. At the same time, the distance between adjacent total reflection points is the total reflection step length, and constraining the size of the turning sub-grating in the light deflection direction (i.e., the second direction) can reduce or even eliminate secondary diffraction.

[0038] Usually, light is propagated in a bundle, and the size of the turning sub-grating in the second direction must be at least twice smaller than the total reflection step length of the light in the waveguide substrate, so that the undesired interference effect can be improved; and the smaller the size of the turning sub-grating in the second direction, the more obvious the improvement effect on the undesired interference effect. More preferably, when the size of the turning sub-grating in the second direction is smaller than the total reflection step length of the light in the waveguide substrate, the undesired interference effect can even be eliminated.

[0039] In addition, the boundary line between each turning sub-grating can be a straight line or a curve.

[0040] The contour shapes of different turning sub-gratings can be the same or different. The sizes of different turning sub-gratings in the first direction can be the same or different. The sizes of different turning sub-gratings in the second direction can be the same or different.

[0041] In practice, the dividing line between the turning sub-gratings is substantially perpendicular to the transmission direction of the light after the light is diffracted and deflected by the turning sub-grating. Specifically, the turning grating is divided into a plurality of turning sub-gratings in the present application in order to reduce or even avoid secondary diffraction of the light after diffraction and deflection, and therefore it is necessary to limit the size of the diffraction sub-grating in the diffraction state when the light is transmitted in the second direction. Therefore, preferably, the dividing line between the turning sub-gratings is substantially perpendicular to the transmission direction of the light after the light is diffracted and deflected by the turning sub-grating.

[0042] It should be noted that a completely vertical relationship in the geometric sense is not required here, and the boundary line between the turning sub-gratings can have a small angle with the transmission direction of the light after diffraction and deflection by the turning sub-grating, such as 2°, 5° or even 10°.

[0043] In practice, the width of the turning sub-grating is smaller than the total reflection step length of the light in the waveguide substrate. The width of the turning sub-grating may be the size of the turning sub-grating in the second direction.

[0044] It is feasible to control the opening (in the diffraction state) and closing (in the non-diffraction state) of the turning sub-grating in the turning grating to realize the directional selection of the deflection area of ​​the turning grating. Among them, the state switching of each turning sub-grating in turn can be a preset order or a random order. After the optical machine is turned on, the turning sub-gratings in the turning grating cyclically switch states. In each cycle, all the turning sub-gratings have been switched to the diffraction state, and at the same time, there is only one turning sub-grating in the diffraction state.

[0045] For example, assuming that the size of each turning sub-grating in the second direction is the same, the number N of the turning sub-gratings is the ratio of the maximum size Max(L) of the turning grating along the second direction to the size l of the turning sub-grating in the second direction, that is, N = Max(L) / l. Assuming that the visual persistence time of the human eye is t, and the time control method of the turning sub-grating is orderly changing along the second direction, then the opening time of each turning sub-grating is Δt <t / N。

[0046] In addition, the turning sub-grating in the diffraction state changes in time, and the opening time of each turning sub-grating is much shorter than the visual persistence time of the human eye, so the human eye will not feel the change of the grating area. However, since the turning sub-region does not necessarily completely overlap with the light propagation path of a certain field of view, the main light of the turning grating in some fields of view may only partially interact with the turning sub-grating currently in the diffraction state at a certain time, and the other part will interact with the new turning sub-grating in the diffraction state at the next moment, so there will be no loss of light. For the propagating light, since the time for the light to pass through the waveguide is extremely short (far shorter than the opening time of the turning sub-grating), it can be considered as a transient process, so the time gradient of the grating area will not cause the secondary deflection of the light downward, and the result of the entire time superposition is a complete image.

[0047] The turning grating of the diffraction optical waveguide provided by the present application includes a plurality of turning sub-gratings, which can be switched between the diffraction state and the non-diffraction state; when the optical machine is turned on, the turning sub-gratings are switched to the diffraction state in turn, and at the same time, there is only one turning sub-grating in the diffraction state; in this way, only a part of the turning grating is in the diffraction state at a time, and only a small amount of light undergoes secondary diffraction and deflects again after the diffraction deflection direction, and even no light undergoes secondary diffraction, thereby improving or even eliminating the undesirable interference effect and improving the display effect of the diffraction optical waveguide. Moreover, the sum of the time that all the turning sub-gratings are in the diffraction state is not greater than the visual persistence time of the human eye, that is, the image observed by the human eye through the diffraction optical waveguide is a complete image, and the visual experience of the user can also be guaranteed.

[0048] Further practicably, the turning grating is implemented as a liquid crystal grating, and the turning sub-grating is switched between the diffraction state and the non-diffraction state by electrical control. Specifically, along the direction away from the surface of the waveguide substrate, the turning grating includes at least a first electrode layer, a liquid crystal layer, and a second electrode layer; wherein the first electrode layer includes a plurality of discrete strip electrodes, the second electrode layer is a continuous electrode, and the area corresponding to a single strip electrode forms a turning sub-grating that can be switched between the diffraction state and the non-diffraction state.

[0049] It should be noted that, in theory, one of the first electrode layer and the second electrode layer can be a plurality of discrete strip electrodes and the other can be a continuous electrode. In the present application, based on the process capability of the current prior art, the first electrode layer on the surface of the waveguide substrate is selected to be prepared as a plurality of discrete strip electrodes. The first electrode layer and the second electrode layer are both transparent electrodes. Further preferably, the first electrode layer and the second electrode layer are both made of ITO conductive glass to improve the transparency of the turning area.

[0050] For example, reference Figure 3-5 , these figures respectively show the structural schematic diagrams of the diffraction optical waveguide provided by an embodiment of the present application at different viewing angles. Specifically, along the direction away from the surface 111 of the waveguide substrate 110, the turning grating 130 at least includes a first electrode layer 131, a liquid crystal layer 132 and a second electrode layer 133, and the first electrode layer 131 includes a plurality of strip electrodes 1311. Among them, Figure 5 A schematic diagram of the layer where the first electrode layer is located is shown.

[0051] In practice, a voltage is applied between any strip electrode 1311 and the second electrode layer, and the liquid crystal molecules in the liquid crystal region corresponding to the strip electrode 1311 are periodically arranged under the action of the external electric field to form a grating, namely, a turning sub-grating. In this way, the strip electrodes correspond to the turning sub-gratings one by one, and the plurality of discrete strip electrodes included in the first electrode layer can be controlled separately, and each strip electrode modulates a turning sub-grating separately, so as to conveniently and quickly realize the opening and closing of the turning sub-grating.

[0052] Generally speaking, the visual persistence time of the human eye is usually 0.1s, and the response time of the liquid crystal material is usually 1-5ms. Taking 5ms as an example, the maximum number of turning sub-gratings is 10. At this time, the size of the turning sub-grating in the second direction may not meet the demand for improving the interference efficiency. In order to increase the number of turning sub-gratings, it is necessary to reduce the response time of the liquid crystal grating.

[0053] In practice, the response time of the liquid crystal layer is related to the rotational viscosity, thickness, dielectric constant and elastic constant of the liquid crystal layer. The response time of the liquid crystal grating can be reduced by modulating these parameters.

[0054] It should be noted that liquid crystal molecules have viscosity. Under the action of an external electric field, the rotation of liquid crystal molecules is not instantaneous. The hysteresis of liquid crystal molecule rotation is usually quantified by response time. This time is divided into rise time and fall time, that is, the time taken by the liquid crystal molecules to respond to polarization in the electric field and the depolarization process of elastic recovery after the electric field is removed. The calculation formula is as follows:

[0055]

[0056] Among them, Tr is the rise time, T f is the falling time, γ is the rotational viscosity, d is the liquid crystal thickness, Δε is the dielectric constant of the liquid crystal, V is the applied voltage, and K is the elastic constant of the liquid crystal.

[0057] Therefore, the response time of the liquid crystal can be reduced by reducing the rotational viscosity and / or thickness of the liquid crystal, and / or increasing the dielectric constant and / or elastic constant of the liquid crystal, so that the response time is much shorter than the visual persistence time of the human eye.

[0058] In practice, in order to further optimize the response time of the liquid crystal layer, an overdrive method can also be used. Specifically, the control voltage of the strip electrodes changes with time to reduce the response time of the liquid crystal layer; that is, the control voltage in the rising stage is greater than the target voltage, the control voltage in the holding stage is equal to the target voltage, and the control voltage in the falling stage is less than the target voltage. The target voltage is the voltage when the liquid crystal layer works normally as a diffraction grating.

[0059] In practice, the target voltages corresponding to at least two strip electrodes are different, so that the equivalent refractive indexes of the turning sub-gratings corresponding to the at least two strip electrodes are different, so that the diffraction efficiency of the turning grating along the transmission direction after the light is coupled into the waveguide substrate gradually increases.

[0060] Specifically, since each strip electrode can apply an electric field individually, different target voltages can be applied to different strip electrodes. When the target voltages are different, the equivalent refractive index of the turning sub-grating corresponding to the strip electrode is also different, and the diffraction efficiency of each turning sub-grating can be controlled individually. Based on this, the present application can optimize the refractive index distribution of the turning grating by controlling different strip electrodes to apply different target voltages, and then optimize the pupil expansion efficiency distribution of the turning grating.

[0061] In this embodiment, by correspondingly connecting and individually modulating the turning sub-gratings and the strip electrodes, the turning area selection based on the dimension of a single turning sub-grating can be accurately and conveniently realized, and the diffraction efficiency of each turning sub-grating can be individually modulated. Specifically, different target voltages can be applied by controlling different strip electrodes, so that the equivalent refractive index of the turning sub-gratings controlled by different strip electrodes is different, and then the diffraction efficiency of the turning sub-gratings controlled by different strip electrodes is different, so that the specific target voltage value can be modulated so that the diffraction efficiency of the turning grating along the transmission direction after the light is coupled into the waveguide substrate gradually increases, so as to further optimize the pupil expansion uniformity of the turning grating.

[0062] In the above implementation, each turning sub-grating is not physically divided, but is defined by the area of ​​the control electrode. In another embodiment, each sub-grating may also be physically divided.

[0063] The augmented reality display device provided in the present application includes a diffractive optical waveguide and an optical machine as described in any of the above items.

[0064] It can be understood that for the diffraction optical waveguide with time-sharing control of the turning grating provided in the present application, only one turning sub-grating is in the diffraction state at any time, and different turning sub-gratings deflect light rays in different fields of view, so that only the light rays in the field of view corresponding to the turning sub-grating in the diffraction state can be deflected to the outcoupling grating for effective utilization, while the light rays in the field of view corresponding to other turning sub-gratings in the non-diffraction state cannot be deflected and are wasted. When the number of turning sub-gratings is N (assuming that the diffraction efficiency and area of ​​each turning sub-grating are the same in an ideal situation), the energy loss is (N-1) / N.

[0065] In order to reduce the energy loss problem caused by the time-sharing control of the turning grating, it is feasible that the optical machine in the present application sequentially illuminates light with different fields of view, and the field of view of the light illuminated at any time matches the field of view of the light that can be deflected by the turning sub-grating that is currently in the diffraction state.

[0066] Specifically, the field of view of the optical machine along the second direction is divided into a number of field of view sub-areas, each of which corresponds to at least one turning sub-grating, so as to ensure that the field of view range of the light that is lit at any time matches the field of view range of the light that can be deflected by the turning sub-grating that is currently in the diffraction state. In this way, while ensuring the integrity of the image, energy is saved and the undesired interference effect is improved.

[0067] In practice, the field of view of the optical machine in the target direction is divided into a number of field of view partitions, and there is a partial overlap between any two adjacent field of view partitions; the target direction is the transmission direction of the light after being diffracted and deflected by the grating.

[0068] It can be understood that, as mentioned in the above-mentioned embodiment, since the turning sub-region does not necessarily completely coincide with the light propagation path of a certain field of view, the main light of the turning grating of some fields of view may only partially interact with the turning sub-grating currently in the diffraction state at a certain time, and the other part will interact with the new turning sub-grating in the diffraction state at the next moment. At this time, in order to improve the undesirable interference effect, it can be ensured that the image observed by the human eye through the diffraction light waveguide is a complete image, and the design makes it possible for any two adjacent field of view partitions to partially overlap, so that the field of view that may be affected by at least two turning sub-gratings in the field of view partition can be illuminated when these turning sub-gratings are turned on. Exemplarily, the field of view of the optical machine in the target direction is (-20°, 20°), which is divided into 4 field of view partitions (-20°, -9°), (-11°-1°), (-1°-11°) and (9°-20°).

[0069] The turning grating of the diffraction light waveguide included in the augmented reality display device provided by the present application includes a number of turning sub-gratings, which can be switched between the diffraction state and the non-diffraction state; when the optical machine is turned on, the turning sub-gratings are switched to the diffraction state in turn, and at the same time, there is only one turning sub-grating in the diffraction state; in this way, only a part of the turning grating is in the diffraction state at a time, and only a small amount of light undergoes secondary diffraction and deflects again after the diffraction deflection direction, and even no light undergoes secondary diffraction, thereby improving or even eliminating the undesirable interference effect and enhancing the display effect of the diffraction light waveguide. Moreover, the sum of the time that all the turning sub-gratings are in the diffraction state is not greater than the visual persistence time of the human eye, that is, the image observed by the human eye through the diffraction light waveguide is a complete image, and the user's visual experience can also be guaranteed. At the same time, the optical machine is adaptively divided into several fields of view and lit up at different times, and the field of view of the light that is lit up each time matches the field of view that can be deflected by the turned-on turning sub-grating. This saves energy and improves the undesired interference effect while ensuring the integrity of the image.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diffractive optical waveguide, characterized in that: The diffractive optical waveguide comprises: A waveguide substrate, the waveguide substrate comprises a first surface and a second surface parallel to each other, an in-coupling grating, a turning grating and an out-coupling grating are arranged on the first surface and / or the second surface; wherein the turning grating comprises a plurality of turning sub-gratings, and the turning sub-gratings are switchable gratings for switching between a diffraction state and a non-diffraction state; when the optical engine is turned on, the turning sub-gratings are switched to a diffraction state in sequence, and at the same time, only one of the turning sub-gratings is in the diffraction state, and the sum of the time that the turning sub-gratings are in the diffraction state is not greater than the visual persistence time of the human eye.

2. The diffractive optical waveguide according to claim 1, characterized in that: The boundary lines between the fold sub-gratings are substantially perpendicular to the transmission direction of the light after the light is diffracted and deflected by the fold sub-gratings.

3. The diffractive optical waveguide according to claim 2, characterized in that: The width of the turn sub-grating is smaller than the total reflection step length of the light in the waveguide substrate.

4. The diffractive optical waveguide according to claim 1, characterized in that: The turning grating is a liquid crystal grating and includes at least a first electrode layer, a liquid crystal layer and a second electrode layer along a direction away from the surface of the waveguide substrate; wherein the first electrode layer includes a plurality of discrete strip electrodes, the second electrode layer is a continuous electrode, and the area corresponding to a single strip electrode forms a turning sub-grating that can switch between a diffraction state and a non-diffraction state.

5. The diffractive optical waveguide according to claim 4, characterized in that: The response time of the liquid crystal layer is related to the rotational viscosity, thickness, dielectric constant and elastic constant of the liquid crystal layer.

6. The diffractive optical waveguide according to claim 4, characterized in that: The control voltage of the strip electrodes varies with time to reduce the response time of the liquid crystal layer; wherein the control voltage in the rising stage is greater than the target voltage, the control voltage in the holding stage is equal to the target voltage, and the control voltage in the falling stage is less than the target voltage.

7. The diffractive optical waveguide according to claim 6, characterized in that: The target voltages corresponding to at least two of the strip electrodes are different, so that the equivalent refractive indexes of the turning sub-gratings corresponding to at least two of the strip electrodes are different, so that the diffraction efficiency of the turning grating along the transmission direction after the light is coupled into the waveguide substrate gradually increases.

8. An augmented reality display device, characterized in that: The augmented reality display device comprises a diffractive optical waveguide and an optical machine as described in any one of claims 1 to 7.

9. The augmented reality display device according to claim 8, characterized in that: The optical machine sequentially illuminates light with different fields of view, and the field of view of the light illuminated at any time matches the field of view of the light that can be deflected by the folding sub-grating currently in the diffraction state.

10. The augmented reality display device according to claim 9, characterized in that: The field of view of the optical machine in the target direction is divided into a plurality of field of view subareas, and there is a partial overlap between any two adjacent field of view subareas; the target direction is the transmission direction of the light after being diffracted and deflected by the grating.

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