Light guide device and head-mounted display equipment

Abstract

The embodiment of the invention provides a light guide device and head-mounted display equipment. The light guide device comprises a substrate, a first grating area, a second grating area, a third grating area and a fourth grating area, wherein the third grating area and the fourth grating area are respectively arranged on two opposite sides of the second grating area along the first direction R1; the first grating area is used for coupling light into the substrate and enabling the light to be totally reflected and propagated in the substrate; the second grating area is used for coupling out the light transmitted to the second grating area; the third grating area and the fourth grating area are used for repeatedly turning back light which passes through the second grating area and is not coupled out between the third grating area and the fourth grating area, so that pupil expansion of the light can be achieved in the second direction R2, and the second direction R2 is perpendicular to the first direction R1. According to the embodiment of the invention, the auxiliary pupil expansion gratings are arranged on the left side and the right side of the second grating area used for coupling out the light, so that pupil expansion is realized in a mode that the light is repeatedly reflected back and forth between the auxiliary pupil expansion gratings.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of optical imaging technology, and more specifically, to a light guide device and a head-mounted display device. Background Art

[0002] Diffractive optical waveguides are the core components of augmented reality (AR) devices. In order to meet the needs of people with different eye distances, diffractive optical waveguides must not only transmit light but also have the effect of expanding pupils.

[0003] At present, the diffraction waveguide pupil expansion schemes are divided into one-dimensional pupil expansion and two-dimensional pupil expansion. One-dimensional pupil expansion only requires a coupling-in zone and a coupling-out zone. There are many two-dimensional pupil expansion schemes, and there are two typical schemes: Scheme 1 is to set an additional turning zone outside the coupling-in zone and the coupling-out zone. The light is first expanded in a certain direction in the turning zone, and then expanded in another direction in the coupling-out zone, thereby achieving the effect of two-dimensional pupil expansion. Scheme 2 is to design the coupling-out zone as a two-dimensional grating, and use the two different diffraction directions of the two-dimensional grating to achieve the effect of two-dimensional pupil expansion. However, in actual applications, it is found that: in the one-dimensional pupil expansion scheme, the coupling-in zone must be set to a long strip shape, and the same is true for the optical machine exit pupil that matches it. Therefore, the volume of the optical machine is large, which will make the AR device as a whole bulky. Among the two two-dimensional pupil expansion schemes mentioned above, the turning zone in Scheme 1 will cause a lot of light energy waste, and the two-dimensional grating in Scheme 2 itself has the defect of low efficiency. Summary of the invention

[0004] The purpose of this application is to provide a new technical solution for a light-guiding device and a head-mounted display device.

[0005] In a first aspect, the present application provides a light guide device. The light guide device comprises a substrate and a first grating region, a second grating region, a third grating region and a fourth grating region arranged on the substrate; wherein the third grating region and the fourth grating region are arranged on opposite sides of the second grating region along a first direction R1;

[0006] The first grating region is used to couple light into the substrate and make the light propagate through total reflection in the substrate;

[0007] The second grating region is used to couple out the light propagating to the second grating region;

[0008] The third grating area and the fourth grating area are used to fold the light that passes through the second grating area but is not coupled out between the third grating area and the fourth grating area multiple times, so that the light can expand the pupil along the second direction R2, and the second direction R2 is perpendicular to the first direction R1.

[0009] Optionally, the light that passes through the second grating region but is not coupled out is reflected back and forth between the third grating region and the fourth grating region, so that the light can be coupled out in the second grating region multiple times.

[0010] Optionally, the first grating region, the second grating region, the third grating region and the fourth grating region all adopt one-dimensional gratings.

[0011] Optionally, a size of the third grating region along the second direction R2 is L1, a size of the fourth grating region along the second direction R2 is L2, a size of the second grating region along the first direction R1 is L, and either L1 or L2 is greater than or equal to L.

[0012] Optionally, a size of the third grating region along the first direction R1 is D1, a size of the fourth grating region along the first direction R1 is D2, and either D1 or D2 is greater than or equal to 10 mm.

[0013] Optionally, a propagation vector of the light modulated by the third grating region and the fourth grating region along the second direction R2 in the second grating region is not zero.

[0014] Optionally, light is coupled into the substrate through the first grating area and propagates to the second grating area by total reflection. In the second grating area, based on the multi-order diffraction characteristics of the grating, part of the light will be directly coupled out, and the other part of the light will continue to propagate in the original direction until entering the fourth grating area. The fourth grating area provides the light with a modulation amount that is twice that of the first grating area, so that the horizontal propagation direction of the light entering the fourth grating area is reversed and re-enters the second grating area. Part of the light will be coupled out, and the other part of the light will propagate in the original direction until entering the third grating area. The light is reversed in the horizontal direction and re-enters the second grating area, and this cycle is repeated.

[0015] Optionally, the light guiding device is a diffraction light waveguide.

[0016] Optionally, the grating vector directions of the first grating region, the second grating region, the third grating region and the fourth grating region are the same;

[0017] The first grating region has a first grating period Λ1, the second grating region has a second grating period Λ2, the third grating region has a third grating period Λ3, and the fourth grating region has a grating period Λ4, and satisfies: Λ1=Λ2=2Λ3=2Λ4.

[0018] Optionally, when incident on the first grating area, the light is incident away from the center of the first grating area, and the deviation direction is perpendicular to the grating vector direction of the first grating area.

[0019] Optionally, when the light is incident on the first grating area, the deviation angle formed by the light and the center of the first grating area is (FOV v / 2n)+△θ; where FOV v is the size of the vertical field of view, n is the refractive index of the substrate of the light-guiding device, and △θ>0.

[0020] Optionally, the first grating region has a first grating period Λ1, the second grating region has a second grating period Λ2, the third grating region has a third grating period Λ3, and the fourth grating region has a grating period Λ4, and satisfies: Λ1=Λ2, Λ3=Λ4, wherein Λ1=2Λ3cosφ, φ is the azimuth angle of the grating in the first grating region.

[0021] Optionally, the grating in the second grating region is a holographic grating.

[0022] In a second aspect, the present application provides a head mounted display device. The head mounted display device comprises:

[0023] shell;

[0024] Projection light machine; and,

[0025] A light guiding device as described in the first aspect.

[0026] The beneficial effects of this application are:

[0027] According to the light-guiding device provided in the embodiment of the present application, two grating areas are added to the substrate, and the two newly added grating areas are designed to be distributed on the left and right sides of the second grating area for coupling out light. The two newly added grating areas form auxiliary pupil expansion areas on the left and right sides of the second grating area. This design enables the light that passes through the second grating area but is not coupled out to be utilized. The uncoupled light returns back and forth between the two newly added grating areas for multiple times to achieve light pupil expansion, so that the light that was originally not coupled out can be coupled out multiple times in the second grating area, which is beneficial to improving the imaging quality.

[0028] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0030] Figure 1 One of the light propagation principle diagrams of the light guide device provided in one embodiment of the present application;

[0031] Figure 2 A second diagram of the light propagation principle of the light guide device provided in one embodiment of the present application;

[0032] Figure 3 A K-space diagram of a light guide device provided in one embodiment of the present application;

[0033] Figure 4 One of the light propagation principle diagrams of a light guide device provided in another embodiment of the present application;

[0034] Figure 5 A second diagram of the light propagation principle of a light guide device provided in another embodiment of the present application;

[0035] Figure 6 A K-space diagram of a light guide device provided in another embodiment of the present application;

[0036] Figure 7 A schematic diagram of the structure of a grating used in a light guiding device provided in an embodiment of the present application.

[0037] Reference numerals:

[0038] 1. The first grating region; 2. The second grating region; 3. The third grating region; 4. The fourth grating region; 5. The substrate. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0040] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

[0041] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0042] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0043] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0044] The light guide device and the head mounted display device provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0045] According to one aspect of an embodiment of the present application, a light guide device is provided, and the light guide device is, for example, a diffractive light waveguide, which can be suitable for use in an augmented reality (AR) device to transmit light emitted by a projection optical machine. The augmented reality (AR) device may include AR glasses or an AR helmet, and the embodiment of the present application does not limit the specific form of the head-mounted display device.

[0046] The light guide device proposed in the embodiment of the present application, see Figure 1 and Figure 2 , the light-guiding device includes a substrate 5, and a first grating area 1, a second grating area 2, a third grating area 3 and a fourth grating area 4 are arranged on the substrate 5. The third grating area 3 and the fourth grating area 4 are arranged on opposite sides of the second grating area 2 along the first direction R1. The first grating area 1 is used to couple light into the substrate 5 and make the light propagate through total reflection in the substrate 5. The second grating area 2 is used to couple out light propagating to the second grating area 2. The third grating area 3 and the fourth grating area 4 are used to reflect the light that passes through the second grating area 2 but is not coupled out back and forth between the third grating area 3 and the fourth grating area 4 for multiple times, so that the light can expand the pupil along the second direction R2, and the second direction R2 is perpendicular to the first direction R1.

[0047] According to the light guide device provided in the above embodiment, four grating regions are arranged on the substrate 5, which are the first grating region 1, the second grating region 2, the third grating region 3 and the fourth grating region 4 mentioned above.

[0048] The first grating region 1 is the coupling-in portion of the entire light guide device, which is responsible for coupling the light emitted by, for example, a projection light machine into the substrate 5, and allowing the light to propagate through total internal reflection in the substrate 5. The second grating region 2 is the coupling-out portion of the entire light guide device, which is responsible for coupling out the light that is totally internally reflected in the substrate 5.

[0049] The third grating area 3 and the fourth grating area 4 are two newly added grating areas on the substrate 5, and the two newly added grating areas are respectively arranged on the left and right sides of the second grating area 2, see Figure 1 and Figure 2 At this time, the third grating area 3, the second grating area 2 and the fourth grating area 4 are arranged adjacent to each other on one surface of the substrate 5 and the three are arranged in a transverse direction. The first direction R1 mentioned in the above embodiment refers to the transverse direction here, which is perpendicular to the light pupil expansion direction.

[0050] In the light-guiding device provided in the embodiment of the present application, the newly added third grating area 3 and the fourth grating area 4 form a partitioned auxiliary pupil expansion area on the left and right sides of the second grating area 2. The two cooperate with each other, and the light that passes through the second grating area 2 but is not coupled out by total reflection can form a back-and-forth reflection state between the third grating area 3 and the fourth grating area 4, that is, this part of the light has undergone multiple turns, so that the light is coupled out multiple times in the second grating area 2, realizing the principle of light pupil expansion. And, see Figure 1 and Figure 2 As the light travels back between the third grating area 3 and the fourth grating area 4, the light tends to gradually extend downward, thereby achieving a pupil expansion effect along the longitudinal direction. It should be noted that the second direction R2 mentioned in the above embodiment refers to the longitudinal direction here, and the second direction R2 is perpendicular to the first direction R1.

[0051] According to the light-guiding device provided in the embodiment of the present application, two grating areas are added to the substrate 5, and the two newly added grating areas are designed to be distributed on the left and right sides of the second grating area 2 for coupling out light. The two newly added grating areas form auxiliary pupil expansion areas on the left and right sides of the second grating area 2. This design enables the light that passes through the second grating area 2 but is not coupled out to be utilized. The uncoupled light is returned back and forth between the two newly added grating areas multiple times to achieve light pupil expansion, so that the light that was originally not coupled out can be coupled out multiple times in the second grating area 2, which is beneficial to improving the imaging quality.

[0052] According to the optical architecture of the light-guiding device provided in the embodiment of the present application, the appearance of the first grating area 1 used for coupling in light is not restricted and can be designed into any shape as needed to match optical machines of various shapes. The design of the coupling part can be very flexible.

[0053] The light guide device provided in the embodiment of the present application provides a new pupil expansion technology solution, which can solve the defects of the existing one-dimensional grating pupil expansion solution and the two-dimensional grating pupil expansion solution. Moreover, there is no need to make major improvements to the structure of the light guide device itself, and only grating areas need to be added on both sides of its outcoupling part, which does not increase the difficulty of production.

[0054] Optionally, the first grating region 1 serves as the coupling-in part of the light-guiding device, and the second grating region 2 serves as the coupling-out part of the light-guiding device. The two may be located on the same surface of the light-guiding device, or may be separately arranged on two opposite surfaces of the light-guiding device. This application does not impose any restrictions on this.

[0055] In some examples of the present application, the first grating region 1 , the second grating region 2 , the third grating region 3 , and the fourth grating region 4 all adopt one-dimensional gratings.

[0056] The light guide device provided in the embodiment of the present application comprises four grating regions each of which uses a one-dimensional grating. The pupil expansion effect is achieved through the coordination between the one-dimensional gratings. In this way, the defect of low efficiency of the two gratings themselves can be avoided.

[0057] Moreover, although the light guide device provided in the embodiment of the present application realizes pupil expansion through a one-dimensional grating, based on the new pupil expansion method, the shape of the first grating area 1 used for coupling light can include but is not limited to a long strip, for example, it can be any shape such as a circle, an ellipse, etc. In this way, the limitation on the projection optical machine is relatively small.

[0058] In some examples of this application, see Figure 1 The size of the third grating region 3 along the second direction R2 is L1, the size of the fourth grating region 4 along the second direction R2 is L2, the size of the second grating region 2 along the first direction R1 is L, and either L1 or L2 is greater than or equal to L.

[0059] See also Figure 1 The shapes of the third grating region 3 and the fourth grating region 4 are, for example, long strips, and a dimension L1 of the third grating region 3 along the second direction R2 is defined as the length dimension of the third grating region 3, and a dimension L2 of the fourth grating region 4 along the second direction R2 is defined as the length dimension of the fourth grating region 4.

[0060] The second grating region 2 is responsible for coupling out light, and its shape is designed to be, for example, rectangular, and two opposite short sides are arranged to be adjacent to the third grating region 3 and the fourth grating region 4 respectively.

[0061] On this basis, for the third grating region 3 and the fourth grating region 4 in the shape of long strips, the length dimensions of the two may be substantially the same as the length of the long side of the second grating region 2 .

[0062] Optionally, see Figure 1 and Figure 2 , the length of the fourth grating region 4 may be greater than the length of the third grating region 3 .

[0063] In some examples of the present application, a size of the third grating region 3 along the first direction R1 is D1, a size of the fourth grating region 4 along the first direction R1 is D2, and either D1 or D2 is greater than or equal to 10 mm.

[0064] According to the description in the above example, the third grating area 3 and the fourth grating area 4 are both in the shape of long strips, and the dimension D1 of the third grating area 3 along the first direction R1 can be defined as its width dimension. Similarly, the dimension D2 of the fourth grating area 4 along the first direction R1 can be defined as its width dimension. The width dimensions of the third grating area 3 and the fourth grating area 4 are related to the total reflection distance of the light in the substrate 5 of the light guide device, and the width dimensions of the two can be set to be less than or equal to 10 mm.

[0065] According to the above two examples, the overall grating layout on the light guide device can be made more compact.

[0066] In some examples of the present application, a propagation vector of the light modulated by the third grating region 3 and the fourth grating region 4 along the second direction R2 in the second grating region 2 is not zero.

[0067] According to the above example, it is possible to ensure that the light is continuously dilated along the second direction R2, thereby facilitating the increase of the amount of outcoupled light from the second grating area 2 to enhance the pupil dilation effect.

[0068] It should be noted that, in the light-guiding device provided in the embodiment of the present application, in the second grating area 2 responsible for outcoupling the light, the light expands along the longitudinal pupil and eventually covers the entire second grating area 2 .

[0069] According to the light guide device provided in the embodiment of the present application, see Figure 1 and Figure 2 , the propagation path of the light is: the light is coupled into the substrate 5 through the first grating area 1 and propagates to the second grating area 2 through total reflection. In the second grating area 2, based on the multi-order diffraction characteristics of the grating, a part of the light will be directly coupled out, and the other part of the light will continue to propagate along the original direction until it enters the fourth grating area 4. The fourth grating area 4 provides the light with a double modulation amount relative to the first grating area 1, so that the horizontal propagation direction of the light entering the fourth grating area 4 is reversed and re-enters the second grating area 2. A part of the light will be coupled out, and the other part of the light will propagate along the original direction until it enters the third grating area 3. The light is reversed in the horizontal direction and re-enters the second grating area 2, and this cycle is repeated.

[0070] The light may be emitted by a projection light engine, for example.

[0071] In some examples of the present application, the light guiding device is a diffractive light waveguide.

[0072] In one example of this application, see Figures 1 to 3The light guide device comprises a substrate 5, a first grating area 1, a second grating area 2, a third grating area 3 and a fourth grating area 4 arranged on the substrate 5; wherein the first grating area 1 is a coupling-in area, the second grating area 2 is a coupling-out area, and the third grating area 3 and the fourth grating area 4 are arranged on opposite sides of the second grating area 2 along the first direction R1. The third grating area 3 and the fourth grating area 4 are auxiliary pupil expansion gratings.

[0073] The grating vector directions of the first grating area 1, the second grating area 2, the third grating area 3 and the fourth grating area 4 are the same. The first grating area 1 has a first grating period Λ1, the second grating area 2 has a second grating period Λ2, the third grating area 3 has a third grating period Λ3, and the fourth grating area 4 has a grating period Λ4, and they satisfy: Λ1=Λ2=2Λ3=2Λ4.

[0074] Figure 1 and Figure 2 is a top view of the light guide device provided in the above example. Figure 3 is the K-space diagram of the light-guiding device provided in the above example.

[0075] Specifically, Figure 1 and Figure 2 The light propagation paths of the lower left edge field of view A and the upper right edge field of view B in the light guide device are shown respectively.

[0076] The grating vector directions of the first grating area 1, the second grating area 2, the third grating area 3, and the fourth grating area 4 are the same, that is, the grating normal directions of the four grating areas are consistent. For example, the directions of the grating vectors can be horizontal, see Figure 3 Of course, the directions of the grating vectors may also be any other directions.

[0077] All grating examples have exactly the same orientation, which can reduce the difficulty of preparation in processes such as laser etching and nanoimprinting.

[0078] Moreover, in the above example, the grating period relationship of the first grating area 1, the second grating area 2, the third grating area 3 and the fourth grating area 4 satisfies: Λ1=Λ2=2Λ3=2Λ4; wherein Λ1, Λ2, Λ3, and Λ4 are respectively the grating periods of the first grating area 1, the second grating area 2, the third grating area 3, and the fourth grating area 4. According to the grating vector size k=2π / Λ, it can be determined that the light modulation capability of the third grating area 3 and the fourth grating area 4 is twice that of the first grating area 1 and the second grating area 2.

[0079] Based on the above example, when light is incident on the first grating area 1 , it should be incident in a direction deviated from the center of the first grating area 1 , and the deviation direction is perpendicular to the grating vector direction of the first grating area 1 .

[0080] Optionally, when the light is incident on the first grating area 1, the deviation angle formed between the light and the center of the first grating area 1 is (FOV v / 2n)+△θ; where FOV v is the size of the vertical field of view, n is the refractive index of the substrate 5 of the light-guiding device, and △θ>0.

[0081] See also Figure 1 and Figure 2 This example requires that the light emitted by the projection optical machine is incident on the first grating area 1 at an angle, that is, the light should form a certain deviation relative to the center of the first grating area 1, and the deviation direction should be perpendicular to the grating vector direction of the first grating area 1, see Figure 3 .

[0082] In the above example, the purpose of using the oblique incidence of light is to make the propagation direction of the light always downward, for example, downward to the left or downward to the right, after the light is modulated by the third grating area 3 and the fourth grating area 4. Figure 1 The middle ray is always to the lower left, such as Figure 2 The center light is always to the lower right.

[0083] See also Figures 1 to 3 , the pupil expansion principle of the light guide device is described as follows:

[0084] After the light is coupled into the substrate 5 through the first grating area 1, in the second grating area 2, due to the multi-order diffraction of the grating, such as the 0th diffraction order and the 1st diffraction order, a part of the light is directly coupled out through the second grating area 2, while the other part of the light is the coupled-out light and will continue to propagate in the original direction until it enters the fourth grating area 4 located on the right side of the second grating area 2; since the fourth grating area 4 provides twice the modulation amount of the first grating area 1, the horizontal propagation direction of the light will be reversed, and the light will re-enter the second grating area 2. At this time, a part of the light will be coupled out in the second grating area 2, and the other part of the light will propagate in the original direction until it enters the third grating area 3 located on the left side of the second grating area 2. Similar to the light propagation of the fourth grating area 4, the light will reverse in the horizontal direction and re-enter the second grating area 2, and this cycle will be repeated until the light covers the entire second grating area 2.

[0085] It should be noted that the light is restricted in the second grating area 2 by the third grating area 3 and the fourth grating area 4 in the horizontal direction. At the same time, since the propagation vector of the light in the second direction R2, i.e., the longitudinal direction, is not zero, as the light repeatedly returns and propagates in the third grating area 3 and the fourth grating area 4, the light will gradually extend downward, thereby achieving a pupil expansion effect along the second direction R2. Figure 1 and Figure 2 .

[0086] In another example of this application, see Figures 4 to 6 The light guide device comprises a substrate 5, a first grating area 1, a second grating area 2, a third grating area 3 and a fourth grating area 4 arranged on the substrate 5; wherein the first grating area 1 is a coupling-in area, the second grating area 2 is a coupling-out area, and the third grating area 3 and the fourth grating area 4 are arranged on opposite sides of the second grating area 2 along the first direction R1. The third grating area 3 and the fourth grating area 4 are auxiliary pupil expansion gratings.

[0087] Among them, the first grating area 1 has a first grating period Λ1, the second grating area 2 has a second grating period Λ2, the third grating area 3 has a third grating period Λ3, and the fourth grating area 4 has a grating period Λ4, and satisfies: Λ1=Λ2, Λ3=Λ4, wherein Λ1=2Λ3cosφ, φ is the azimuth angle of the grating in the first grating area 1.

[0088] Optionally, the grating in the second grating area 2 is a holographic grating.

[0089] Figure 4 and Figure 5 The schematic top views of the light guide device provided for the above example respectively show the light propagation paths of the lower left edge field of view A and the upper right edge field of view B in this example. Figure 6 is the K-space diagram of the light-guiding device provided in the above example.

[0090] Figures 4 to 6 The grating layout on the light guide device shown is similar to Figures 1 to 3 The examples shown are basically the same, and the main difference between the two is that the grating vector directions of the first grating area 1 and the second grating area 2 are designed to be different. Figures 4 to 6 Based on the example shown, the light emitted by the projection optical machine no longer needs to be incident on the first grating area 1 off-center, and can be incident at any angle, and the grating vector directions of the first grating area 1 and the second grating area 2 are adjusted accordingly, so that the light still propagates downward in the substrate 5, see Figure 4 and Figure 5 .

[0091] The grating relationship satisfies: Λ1=Λ2, Λ3=Λ4, wherein Λ1=2Λ3cosφ, φ is the azimuth angle of the grating in the first grating region 1.

[0092] Additionally, this example behaves slightly differently from the previous example when coupling light out:

[0093] exist Figures 1 to 3 In the light-guiding device shown, the first grating vector and the second grating vector of the second grating region 2 correspond to the ±1st diffraction orders of the second grating region 2, for example, respectively, and both can be used as outcoupling orders. Figures 4 to 6 In the light-guiding device shown, only the first grating vector of the second grating region 2 can be used as an out-coupling order, and the image coupled out by the second grating vector thereof may cause a ghost phenomenon.

[0094] In order to avoid the possible ghost phenomenon, it is necessary to suppress the second grating vector of the second grating area 2. Based on this, a volume grating can be selected in the second grating area 2 to achieve this goal.

[0095] See also Figure 7 , (a) and (b) are diffraction diagrams of the surface relief grating, which correspond to the first grating vector and the second grating vector of the second grating area 2 respectively, and (c) and (d) are diffraction diagrams of the holographic grating, which correspond to the first grating vector and the second grating vector of the second grating area 2 respectively. Since the surface relief grating is a thin grating, based on the Ramanes diffraction principle, it is impossible to completely eliminate the diffraction order on one side. However, as a thick grating, the holographic grating can only respond to a certain angular bandwidth based on the Bragg diffraction principle, so the diffraction order on one side can be divided.

[0096] The light-guiding device provided in the embodiment of the present application comprises four grating regions, wherein the gratings are all one-dimensional gratings. Figures 4 to 6 In the example shown, the second grating area 2 needs to use a holographic grating, and other grating areas can be one or more of a surface relief grating and a holographic grating.

[0097] The surface relief grating includes rectangular grating, blazed grating, tilted grating, step grating, sinusoidal grating, etc. The holographic volume grating includes photopolymer volume grating, polymer dispersed liquid crystal volume grating and liquid crystal volume grating, etc.

[0098] It should be noted that in order to obtain better optical performance, in the light-guiding device provided in the embodiment of the present application, each grating can be partitioned and designed based on parameters such as grating thickness, duty cycle, grating tilt angle, coating depth, coating material, volume grating Bragg tilt angle, and volume grating material refractive index.

[0099] According to another embodiment of the present application, a head mounted display device is provided, wherein the head mounted display device comprises a housing, a projection light engine, and the light guide device as described above.

[0100] The head mounted display device includes AR smart glasses or AR smart helmets, etc., which is not limited in the embodiments of the present application.

[0101] The specific implementation of the head-mounted display device of the embodiment of the present application can refer to the above-mentioned embodiments of the light guide device, so it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0102] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0103] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A light guide device, characterized in that: The invention comprises a substrate (5) and a first grating region (1), a second grating region (2), a third grating region (3) and a fourth grating region (4) arranged on the substrate (5); wherein the third grating region (3) and the fourth grating region (4) are arranged on two opposite sides of the second grating region (2) along a first direction R1; The first grating region (1) is used to couple light into the substrate (5) and cause the light to propagate by total reflection in the substrate (5); The second grating region (2) is used to couple out light propagating to the second grating region (2); The third grating area (3) and the fourth grating area (4) are used to reflect the light that has passed through the second grating area (2) but has not been coupled out back and forth between the third grating area (3) and the fourth grating area (4) for multiple times, so that the light can expand the pupil along a second direction R2, and the second direction R2 is perpendicular to the first direction R1.

2. The light guide device according to claim 1, characterized in that: The first grating region (1), the second grating region (2), the third grating region (3) and the fourth grating region (4) all adopt one-dimensional gratings.

3. The light guide device according to claim 1, characterized in that: The size of the third grating region (3) along the second direction R2 is L1, the size of the fourth grating region (4) along the second direction R2 is L2, the size of the second grating region (2) along the first direction R1 is L, and either L1 or L2 is greater than or equal to L.

4. The light guide device according to claim 3, characterized in that: The size of the third grating region (3) along the first direction R1 is D1, the size of the fourth grating region (4) along the first direction R1 is D2, and either D1 or D2 is greater than or equal to 10 mm.

5. The light guide device according to claim 1, characterized in that: The propagation vector of the light modulated by the third grating area (3) and the fourth grating area (4) along the second direction R2 in the second grating area (2) is not zero.

6. The light guide device according to claim 1, characterized in that: The light is coupled into the substrate (5) through the first grating area (1) and propagates to the second grating area (2) by total reflection. In the second grating area (2), based on the multi-order diffraction characteristics of the grating, part of the light is directly coupled out, and the other part of the light continues to propagate along the original direction until entering the fourth grating area (4). The fourth grating area (4) provides the light with a modulation amount twice that of the first grating area (1), so that the horizontal propagation direction of the light entering the fourth grating area (4) is reversed and re-enters the second grating area (2). Part of the light is coupled out, and the other part of the light propagates along the original direction until entering the third grating area (3). The light is reversed in the horizontal direction and re-enters the second grating area (2), and the cycle repeats.

7. The light guide device according to claim 1, characterized in that: The light guiding device is a diffraction light waveguide.

8. The light guide device according to any one of claims 1 to 7, characterized in that: The grating vector directions of the first grating region (1), the second grating region (2), the third grating region (3) and the fourth grating region (4) are the same; The first grating region (1) has a first grating period Λ1, the second grating region (2) has a second grating period Λ2, the third grating region (3) has a third grating period Λ3, and the fourth grating region (4) has a grating period Λ4, and satisfies: Λ1=Λ2=2Λ3=2Λ4.

9. The light guide device according to claim 8, characterized in that: When incident on the first grating area (1), the light is incident in a direction deviated from the center of the first grating area (1), and the deviation direction is perpendicular to the grating vector direction of the first grating area (1).

10. The light guide device according to claim 8, characterized in that: When the light is incident on the first grating area (1), the deviation angle formed by the light and the center of the first grating area (1) is (FOV v / 2n)+△θ; where FOV v is the size of the vertical field of view, n is the refractive index of the substrate (5) of the light-guiding device, and △θ>0.

11. The light guide device according to any one of claims 1 to 7, characterized in that: The first grating region (1) has a first grating period Λ1, the second grating region (2) has a second grating period Λ2, the third grating region (3) has a third grating period Λ3, and the fourth grating region (4) has a grating period Λ4, and satisfies: Λ1=Λ2, Λ3=Λ4, wherein Λ1=2Λ3cosφ, φ is the azimuth angle of the grating in the first grating region (1).

12. The light guide device according to claim 11, characterized in that: The grating in the second grating area (2) is a holographic grating.

13. A head mounted display device, characterized in that: include: shell; Projection light machine; as well as, A light guiding device as claimed in any one of claims 1 to 12.

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