Curved waveguide and head-mounted display

Abstract

The invention discloses a curved waveguide and a head-mounted display. The curved waveguide comprises at least one curved waveguide substrate; the at least one coupling-in area is arranged on at least one side of the curved waveguide substrate; the coupling-out area is arranged on the inner side curved surface of the curved surface waveguide substrate and located on a transmission light path of the image light, and the coupling-out area comprises a diffractive optical element; in the same curved surface waveguide substrate, an area between the coupling-in area and the coupling-out area is an optical functional area, the curvature radiuses of the inner side curved surfaces, corresponding to the curved surface waveguide substrate, of the optical functional area and the coupling-out area are the same, and the curvature radiuses of the outer side curved surfaces, corresponding to the curved surface waveguide substrate, of the optical functional area are the same; along the propagation direction of the image light, the outer curved surface of the coupling-out area corresponding to the curved waveguide substrate is a free curved surface, and the curvature radius is gradually increased. According to the curved waveguide, the available area of a coupling-out region of the curved waveguide is increased, the receivable range of a user image is larger, and the curved waveguide has a better application prospect.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of display technology, and in particular to a curved waveguide and a head-mounted display. Background Art

[0002] Augmented Reality (AR) is a technology that integrates the real world and virtual information. AR display systems usually include a micro-projector and an optical display screen. The pixels on the micro-display are projected into the user's pupils through the optical display screen. At the same time, the user can see the real world through the optical display screen. The micro-projector provides virtual content for the device, and the optical display screen is usually a transparent optical component. Optical waveguide is a realization path for optical display screens. When the refractive index of the transmission medium is greater than that of the surrounding medium and the incident angle in the waveguide is greater than the critical angle of total reflection, light can be transmitted in the waveguide without leakage, and total reflection occurs. After the light from the projector is coupled into the waveguide, the light continues to propagate the image losslessly in the waveguide until it is coupled out by the subsequent structure.

[0003] At present, electric vehicles have become a convenient and commonly used means of transportation. Drivers need to wear helmets when riding electric vehicles, and they need to lower their heads to check relevant information during riding, which may lead to potential traffic accident risks. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a curved waveguide and a head-mounted display, which has a curved display structure compared to a traditional lens-type flat waveguide, increases the available area of ​​the curved waveguide outcoupling region, and has a larger receivable range of user images, thus having better application prospects.

[0005] In a first aspect, an embodiment of the present invention provides a curved waveguide, comprising at least one curved waveguide substrate;

[0006] At least one coupling-in region is disposed on at least one side of the curved waveguide substrate; the coupling-in region is used to couple the image light emitted by the optical machine into the curved waveguide substrate;

[0007] A coupling-out region is arranged on the inner curved surface of the curved waveguide substrate and is located on the transmission optical path of the image light, and is used to couple the image light out of the curved waveguide substrate; the coupling-out region includes a diffractive optical element;

[0008] Among them, in the same curved waveguide substrate, the coupling-in region and the region between the coupling-in region and the coupling-out region are optical functional regions, and the curvature radii of the inner curved surfaces of the optical functional region and the coupling-out region corresponding to the curved waveguide substrate are the same; the curvature radii of the outer curved surface of the optical functional region corresponding to the curved waveguide substrate are the same; along the propagation direction of the image light, the outer curved surface of the coupling-out region corresponding to the curved waveguide substrate is a free curved surface and the curvature radius gradually increases.

[0009] Optionally, the outcoupling area includes n outcoupling positions, and the outer curved surface of the curved waveguide substrate correspondingly includes n-1 reflection positions, and the n outcoupling positions and n-1 reflection positions are alternately arranged on the propagation path of the image light; wherein n≥2, and n is a positive integer; the distances from each of the n-1 reflection positions to the inner curved surface of the curved waveguide substrate and the curvature radius of the outer curved surface of the curved waveguide substrate at the n-1 reflection position are adapted so that the relationship between the emission angle of the i-th outcoupling position and the emission angle of the i+1-th outcoupling position satisfies:

[0010] θ i+1 =θ i +θ;i=1,2,3,4,...,n-1;

[0011]

[0012]

[0013] Among them, θ 0 is the angle between the light and the normal after entering the curved waveguide substrate, r is the radius of curvature of the inner side of the curved waveguide substrate, d is the thickness of the curved waveguide substrate in the optical functional area; θ is the central angle corresponding to the reflection points of two adjacent outcoupling positions, n WG is the refractive index of the curved waveguide substrate, λ is the wavelength of the image light, T is the grating period of the diffractive optical element, and as the value of i gradually increases, the i-th reflection position gradually moves away from the coupling-in region, and the i-th coupling-out position gradually moves away from the coupling-in region.

[0014] Optionally, the n out-coupling positions included in the out-coupling area are consistent with a reference position, and the reference position is the out-coupling position on the out-coupling area when the curvature radius of the outer curved surface of the curved waveguide substrate in the out-coupling area and the optical functional area is the same.

[0015] Optionally, an optical structure is set at the reflection position, and the optical structure includes a first side surface, a middle surface and a second side surface that are connected; wherein the middle surface is a reflection surface; the first side surface is parallel to the incident light; the second side surface is parallel to the reflected light; and the slope of the reflection surface is adjusted with the reflection position.

[0016] Optionally, the intermediate surface is coated with a filter film, and the filter film includes a monochrome filter film or a filter film that transmits at least two colors; the incident angle of the filter film satisfies the angle range of total reflection of the image light on the curved waveguide substrate.

[0017] Optionally, a reflection grating is arranged on the intermediate surface; the reflection grating comprises a bevel grating.

[0018] Optionally, the refractive index of the optical structure is consistent with the refractive index of the curved waveguide substrate.

[0019] Optionally, along the propagation direction of the image light in the curved waveguide substrate, the reflectivities of the n reflection positions gradually increase.

[0020] Optionally, an inner curved surface of the out-coupling region corresponding to the curved waveguide substrate is a spherical surface, and an outer curved surface of the out-coupling region corresponding to the curved waveguide substrate is a free-form surface.

[0021] Optionally, the tail end of the curved waveguide substrate is coated with a light absorbing material.

[0022] Optionally, the curved waveguide includes a plurality of curved waveguide substrates stacked in layers;

[0023] The optical functional areas of at least two of the curved waveguide substrates have different curvature radii, and the curved waveguide substrates with different curvature radii propagate incident light rays of different wavelengths.

[0024] Optionally, along the direction in which the image light beam is coupled out of the curved waveguide substrate, the curvature radius of the optical functional areas of the plurality of curved waveguide substrates gradually decreases, and the wavelengths propagated by the plurality of curved waveguide substrates gradually decrease.

[0025] Optionally, along the direction in which the image light is coupled out of the curved waveguide substrate, the thicknesses of the plurality of curved waveguide substrates gradually increase.

[0026] In a second aspect, an embodiment of the present invention further provides a head mounted display, comprising the curved waveguide provided in the first aspect, and further comprising at least one optical machine and at least one image collector;

[0027] The image collector is used to acquire the surrounding image, and transmit the surrounding image through the optical machine to be displayed at the output end of the curved waveguide.

[0028] The curved waveguide based on the diffraction implementation method provided in the embodiment of the present invention has a curved display structure compared to the traditional lens-type flat waveguide sheet, which increases the available area of ​​the curved waveguide outcoupling region, and the receivable range of the user image is larger. The curvature radius of the curved waveguide substrate and the arc length can be set according to the needs of the actual scene. By adjusting the curvature radius of the diffraction waveguide substrate corresponding to the outcoupling region, the emission angle of the outgoing light is adjusted, the imaging aberration is reduced, and the user's visual experience is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0030] Figure 1 A schematic diagram of the structure of a curved waveguide provided in an embodiment of the present application;

[0031] Figure 2 A schematic diagram comparing the light propagation paths of two curved waveguide substrates;

[0032] Figure 3 for Figure 1 A schematic diagram of the tilt angle setting of the reflection position provided in;

[0033] Figure 4 for Figure 1 A schematic diagram of the tilt angle setting of the reflection position provided in;

[0034] Figure 5 A schematic diagram of the structure of another curved waveguide provided in an embodiment of the present application;

[0035] Figure 6 for Figure 5 A schematic diagram of an optical structure arranged at a reflection position;

[0036] Figure 7 for Figure 5 A schematic diagram of an optical structure arranged at a reflection position;

[0037] Figure 8 A side view of a head mounted display provided in an embodiment of the present application;

[0038] Fig. 9 A top view of a head-mounted display provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be fully described below in combination with the drawings in the embodiments of the present invention through specific implementation methods. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work fall within the protection scope of the present invention.

[0040] Example

[0041] An embodiment of the present invention provides a curved waveguide. Figure 1 This is a schematic diagram of the structure of a curved waveguide provided in an embodiment of the present application. Figure 1 As shown, the curved waveguide provided by the embodiment of the present invention includes at least one curved waveguide substrate 10; at least one coupling-in region 20, which is arranged on at least one side of the curved waveguide substrate 10; the coupling-in region 20 is used to couple the image light emitted by the optical machine into the curved waveguide substrate 10; the coupling-out region 30 is arranged on the inner curved surface of the curved waveguide substrate 10, and the coupling-out region 30 includes a diffractive optical element; the coupling-out region 30 is arranged on the transmission optical path of the image light, and is used to couple the image light out of the curved waveguide substrate 10; wherein, in the same curved waveguide substrate 10, the coupling-in region 20, the region between the coupling-in region 20 and the coupling-out region 30 are optical functional regions, the optical functional region and the coupling-out region 30 correspond to the same inner curved surface of the curved waveguide substrate 10 with the same curvature radius, and the optical functional region corresponds to the same outer curved surface of the curved waveguide substrate 10 with the same curvature radius; along the propagation direction of the image light, the curvature radius of the outer curved surface of the curved waveguide substrate 10 corresponding to the coupling-out region 30 gradually increases. The surface normals of the inner curved surface and the outer curved surface of the optical functional area intersect at one point, and the surface normals of the inner curved surface of the out-coupling area also intersect at this point.

[0042] For example, the following is combined Figure 1 The curved waveguide provided in the embodiment of the present invention includes a curved waveguide substrate 10 as an example for explanation. Specifically, the curved waveguide substrate 10 can be an optical glass substrate or a resin substrate with a thickness between 0.5 mm and 3 mm. The concave surface of the curved waveguide substrate 10 is defined as the inner curved surface M. 1 , the convex surface is the outer surface M 2 The coupling-in region 20 of the curved waveguide substrate 10 may be one or more regions, which may be disposed on the inner curved surface M of the curved waveguide substrate 10. 1 Or the outer surface M 2 side.

[0043] In some embodiments, the coupling structure of the coupling region 20 is a diffractive optical element, such as a straight tooth grating, a blazed grating, a slanted tooth grating, a volume holographic grating, etc. The coupling structure is disposed on the inner curved surface M of the curved waveguide substrate 10.1 Or outer surface M 2 , the image light emitted by the optical machine is incident on the diffractive optical element after passing through the phase modulator, and when incident on the diffractive optical element, the light of the same field of view angle has the same angle with the normal of the curved waveguide substrate 10 at the coupling-in incident point, that is, the same incident angle, so that the image light of the same field of view angle has the same angle with the normal of the curved waveguide substrate 10 at the coupling-in diffraction point, that is, the same diffraction angle, and thus the total reflection transmission angle in the curved waveguide is the same. In some embodiments, the coupling structure is a geometric optical element, for example, a coupling prism or a coupling inclined plane is provided in the coupling-in region 20, and the image light emitted by the optical machine is incident on the geometric optical element at a specific angle after passing through the phase modulator, so that the image light of the same field of view angle has the same total reflection transmission angle in the curved waveguide substrate 10. The image light S emitted by the optical machine 100 is coupled into the curved waveguide substrate 10 from the coupling-in region 20, and the image light S is reflected on the inner curved surface M of the curved waveguide substrate 10. 1 and the outer surface M 2 The light is totally reflected and transmitted to the outcoupling region 30 .

[0044] Furthermore, in order to adapt to the wearing use of the user, the inner curved surface M of the central area of ​​the curved waveguide substrate 10 can be 1 The outcoupling region 30 is provided. The outcoupling region 30 may adopt a diffraction optical element, such as a diffraction grating, etc., to break the total reflection transmission of the image light S and transmit the image light S from the inner curved surface M 1 The area of ​​the coupling-out region 30 can be reasonably set according to the size of the user's viewing area.

[0045] Furthermore, in order to ensure that the image light is transmitted by total reflection at a constant reflection angle in the curved waveguide substrate 10 after entering the curved waveguide substrate 10 and before being coupled out from the curved waveguide substrate 10, the coupling-in region 20 and the region between the coupling-in region 20 and the coupling-out region 30 are set as optical functional regions, and the surface normals of the optical functional regions are set to intersect at one point. Such a setting is conducive to ensuring that the light is transmitted by total reflection at a constant reflection angle in the curved waveguide after entering the curved waveguide substrate 10, and the transmission is aberration-free. Among them, the curvature radius and arc length of the optical functional region of the curved waveguide substrate 10 can be set according to the needs of the actual scene. For example, in the application of helmet display, the curvature radius of the curved waveguide substrate 10 needs to meet the driver's head wearing comfort requirements.

[0046] It should be noted that if the image light of the same viewing angle is not parallel light when entering the human eye, the distance of the virtual images observed by the human eye at different pupil positions is inconsistent, and there are phenomena such as breakage and crossing between the virtual images, which will cause dizziness to the driver during the head swinging process. Therefore, the light of the same viewing angle needs to be fully reflected and transmitted at a constant and same reflection angle in the curved waveguide substrate 10 after entering the curved waveguide substrate 10, and the image light of the same viewing angle should be basically parallel when coupled out of the curved waveguide substrate 10 and entering the human eye.

[0047] Figure 2 Schematic diagram of the comparison of light propagation paths of two curved waveguide substrates, see Figure 2 As shown, the inner curved surface M of the curved waveguide substrate 10 1 The diffractive optical element of the outcoupling region 30 is set, S is the incident light, S' is the central field of view light Figure 1 The outcoupled light of the transmission path coupled out of the curved waveguide substrate with the outer surface curvature changing as shown, S" is the outcoupled light of the transmission path coupled out of the curved waveguide substrate where the surface normal of the curved waveguide substrate intersects at one point through the central field of view light. If the surface normal of the curved waveguide substrate intersects at one point, since the image light of the same field of view angle has the same angle with the normal of the curved waveguide substrate at the coupling incident point, the light of the same field of view angle has the same angle with the normal of the curved waveguide at the coupling position, that is, the light of the same field of view angle is no longer a parallel light after coupling out of the curved waveguide, which will produce aberrations, such as Figure 2 As shown in the outcoupled light S”, it can be seen that the outcoupled light S” is a converging light. After adjusting the curvature radius of the outer surface corresponding to the outcoupled area and the waveguide thickness, the outcoupled light of the same field angle can be corrected to a parallel light, as shown in Figure 2 As shown in the outcoupled light S', it can be seen that the outcoupled light S' is a parallel light.

[0048] In order to solve the problem that the light rays in the same field of view are not parallel, the present application further proposes to redesign the outer curved surface area corresponding to the outcoupling area in the curved waveguide substrate. Figure 1 As shown, the curvature radius of the inner curved surface M1 of the out-coupling region 30 corresponding to the curved waveguide substrate 10 is set to be the same as the curvature radius of the optical functional area; along the propagation direction of the image light, the curvature radius of the outer curved surface of the out-coupling region 30 corresponding to the curved waveguide substrate 10 is set to gradually increase, that is, along the propagation direction of the image light, the thickness of the curved waveguide substrate 10 gradually decreases. Through this setting, the out-coupling light is corrected, and the light out-coupling position remains unchanged. Figure 1 and Figure 2 As shown in the outcoupled light S', the central field of view light passes through Figure 1The curvature-changing curved waveguide substrate coupling shown in the figure can adjust the angle of light incident on the coupling position in the curvature-changing coupling area, and correct the convergent light of the same field of view angle of the coupling to be approximately parallel light emission, so as to ensure that the virtual image distance observed by the human eye at different pupil positions is consistent, avoid the phenomenon of breakage and crossing between virtual images, and avoid the problem of dizziness of the driver during the head swinging process, thereby improving the driver's safe driving.

[0049] Among them, the image light S emitted by the optical machine can provide relevant auxiliary information for the driver wearing a helmet (curved waveguide), such as navigation information, road condition information, etc., and project this information into a virtual image, which is displayed at a certain distance in front of the driver, so that the driver can obtain it in a head-on state, which is conducive to reducing potential traffic accidents and improving driving safety.

[0050] In summary, the curved waveguide provided by the present invention has a curved display structure compared to the traditional lens-type flat waveguide, which increases the available area of ​​the curved waveguide outcoupling region, and the receivable range of the user image is larger. The curvature radius of the curved waveguide substrate and the arc length can be set according to the needs of the actual scene. By adjusting the curvature radius of the diffraction waveguide substrate corresponding to the outcoupling region, the emission angle of the outgoing light is adjusted, the imaging aberration is reduced, and the user's visual experience is improved.

[0051] Based on the above embodiments, Figure 3 for Figure 1 The schematic diagram of the tilt angle setting of the reflection position provided in Figure 1 and Figure 3 As shown, optionally, the coupling region includes n coupling positions, and the outer curved surface of the curved waveguide substrate includes n-1 reflection positions accordingly. Starting from the first coupling position, the n coupling positions and the n-1 reflection positions are alternately arranged on the propagation path of the image light; wherein n≥2, and n is a positive integer. The distances of the n-1 reflection positions from the inner curved surface of the curved waveguide substrate and the curvature radius of the outer curved surface of the curved waveguide substrate at the n-1 reflection position are adapted so that the relationship between the emission angle of the i-th coupling position and the emission angle of the i+1-th coupling position satisfies:

[0052] θ i+1 =θ i +θ;i=1,2,3,4,...,n-1;(1.1);

[0053]

[0054]

[0055] Among them, θ 0 is the angle between the light and the normal after entering the curved waveguide substrate, θ1 is the emission angle at the first outcoupling position, r is the radius of curvature of the inner side of the curved waveguide substrate, d is the thickness of the curved waveguide substrate in the optical functional area; θ is the central angle corresponding to the reflection points of two adjacent outcoupling positions, n WG is the refractive index of the curved waveguide substrate, λ is the wavelength of the image light, T is the grating period of the diffractive optical element, and as the value of i gradually increases, the i-th reflection position gradually moves away from the coupling-in region, and the i-th coupling-out position gradually moves away from the coupling-in region.

[0056] Specific, combined Figure 1 and Figure 3 As shown, the inner curved surface M of the curved waveguide substrate 10 corresponding to the outcoupling region 30 1 There are n out-coupling positions, and the outer curved surface M of the curved waveguide substrate 10 corresponding to the out-coupling region 30 is 2 There are n-1 reflection positions 31, and the reflection surface of the reflection position 31 faces the inner curved surface M. 1 The curvature radius of the n-1 reflection positions 31 gradually increases to adjust the output angle of the outcoupled light. The n-1 reflection positions 31 reflect the image light S to the outcoupling area 30 by reflection or total reflection, and the outcoupling area 30 then couples the image light S out of the curved waveguide substrate 10.

[0057] Practically, the present application adopts the following method to correct the size and curvature radius of the n-1 reflection positions 31 corresponding to the outcoupling region 30 from the inner surface of the curved waveguide substrate:

[0058] Specifically, refer to Figure 3 As shown, the emission angle at the i-th coupling position of the coupling region 30 is set to θ i , then the emission angle at the adjacent i+1th outcoupling position is θ i+1 , the emission angles of the two outcoupling positions should satisfy θ i+1 =θ i +θ, in this way, according to the diffraction of light, the outcoupled light S' with the same field of view angle can be made parallel light.

[0059] Where θ is the normal angle between two adjacent outcoupling positions, and θ satisfies formula (1.2):

[0060]

[0061] The output angle at the first outcoupling position is θ 1 ,θ 1 Satisfies formula (1.3):

[0062]

[0063] Specifically, by using the ray tracing method, after determining each out-coupling position, starting from the first out-coupling position, the outer surface M between two adjacent out-coupling positions is determined one by one. 2 The reflection position of Figure 3 As shown, on the outcoupling region 30, in two adjacent outcoupling positions;

[0064] The diffraction equation of the i-th outcoupling position is:

[0065]

[0066] The diffraction equation of the i+1th outcoupling position is:

[0067]

[0068] Among them, θ i is the outgoing angle of the outgoing light at the ith outgoing coupling position, is the incident angle of the incident light at the i-th outcoupling position, θ i+1 is the outgoing angle of the outgoing light at the i+1th outgoing position, is the incident angle of the incident light at the i+1th outcoupling position.

[0069] refer to Figure 3 As shown, from the above equations (1.1)-(1.3), the difference between the required angle for reflection at the reflection position on the outer curved surface M2 of the curved waveguide substrate 10 corresponding to the outcoupling region 30 and the reflection angle before correction is Therefore, the deviation between the normal angle at the reflection position on the outer curved surface M2 and the normal angle before correction is Thus, the outer surface M between the i-th coupling position and the i+1-th coupling position can be accurately obtained. 2 The reflection position of Figure 3 The i-th reflection position 31i is shown. Similarly, the outer curved surface M between the i+1-th coupling position and the i+2-th coupling position is obtained accurately. 2 The reflection position of Figure 3 The i+1th reflection position 31i+1 is shown.

[0070] For example, when i=1, Figure 3 The comparison diagram and angle relationship of the first out-coupling position and the second out-coupling position before and after correction are shown; when i=n, ​​the angle relationship of the n reflection positions 31 after correction is obtained, and the outer curved surface M of the curved waveguide substrate 10 corresponding to the out-coupling region 20 is obtained. 2 The n reflection positions 31 of the outer surface M 2 All the outer reflection points on the surface are smoothly connected to obtain Figure 1The outer curved surface M2 shown in the figure can correct the aberration of the outgoing light and obtain approximately parallel outgoing light.

[0071] In other embodiments, the heights of n-1 reflection positions can be calculated to fit a smooth free curve according to these reflection points. After the fitting curve is obtained, the curvature radius of the fitting curve at these reflection points can be obtained. Figure 4 for Figure 1 The schematic diagram of the tilt angle setting of the reflection position provided in Figure 1 and Figure 4 As shown, specifically:

[0072] Record the height hi of the i-th reflection position 31i: n outcoupling positions and n-1 reflection positions are arranged alternately on the propagation path of the image light: out1, re1, out2, re2, out3…

[0073] Figure 4 In the example, taking i=1, the first coupling point out1, the incident angle Since the image light S is previously transmitted by total reflection in the waveguide substrate 10, the transmission angles are consistent, which are all θ 0 ; The diffraction angle is θ 1 , that is, the emission angle of the first outcoupling position, satisfies:

[0074] The second coupling point out2, the incident angle is The diffraction angle is θ 2 , that is, the emission angle of the second outcoupling position, satisfies:

[0075] If the outgoing light rays from the two outcoupling positions are to be parallel, then θ 2 =θ 1 +θ, we can get formulas (1.4) and (1.5):

[0076]

[0077]

[0078] Where n is the waveguide refractive index, λ is the image light wavelength, and T is the outcoupling grating period.

[0079] Recombination Figure 4 As shown, according to the geometric relationship:

[0080] Since β+θ 0 =π / 2, then δ 1 =β=π / 2-θ 0, (1.6);

[0081] tanγ 1 =h 1 / A 1 , tanδ 1 =h 1 / B 1 , A 1 +B 1 =2r*sin(θ / 2)=X; (1.7);

[0082] Where X is the position between two adjacent outcoupling positions. According to the three formulas in (1.7), the height h of the i-th reflection position 31i is calculated. 1 .

[0083] By analogy, according to the following formula in (1.8):

[0084] δ i+1 =β-(φ i+1 -θ 0 ), δ 1 =β=π / 2-θ 0 , θ i+1 =θ i +θ,θ=2θ 0 -2arcsin((rsinθ 0 ) / (r+d)),

[0085] Ai+Bi=X=2r*sin(θ / 2), tanγi=hi / Ai, tanδi=hi / Bi, i=1, 2, 3….

[0086] The height hi of the i-th reflection position 31i is calculated, and finally the heights of n-1 reflection positions are obtained.

[0087] Furthermore, after determining the heights of n-1 reflection positions in turn, these reflection points are fitted into a smooth free curve. After obtaining the fitting curve, the curvature radius of the fitting curve at these reflection points can be obtained, thereby obtaining the outer surface M2 of the waveguide substrate 10 corresponding to the outcoupling area 30.

[0088] Optionally, the n out-coupling positions included in the out-coupling region are consistent with the reference position, and the reference position is the outer curved surface M of the curved waveguide substrate. 2 The outcoupling position on the outcoupling area when the curvature radii of the outcoupling area and the optical functional area are the same.

[0089] Optionally, the outcoupling region 30 corresponds to the inner curved surface M of the curved waveguide substrate 10. 1The outcoupling region 30 corresponds to the outer curved surface M of the curved waveguide substrate 10. 2 It is a free-form surface.

[0090] Specifically, the inner surface M of the curved band 1 is a spherical surface, the outer surface M 2 It is a free-form surface and can be manufactured by cutting and grinding, etc. Wherein, starting from the first outcoupling position of the light outcoupling, the thickness of the curved waveguide substrate 10 gradually decreases.

[0091] Optionally, the tail end of the curved waveguide substrate 10 is coated with a light absorbing material to reduce light leakage.

[0092] Furthermore, in order to improve the outer curved surface M of the outcoupling region 30 corresponding to the curved waveguide substrate 10 2 To improve the light reflection efficiency, an optical structure 32 may be provided at the n reflection positions 31 . Figure 5 A schematic diagram of the structure of another curved waveguide provided in an embodiment of the present application; Figure 6 for Figure 5 A schematic diagram of an optical structure arranged at a reflection position; Figure 7 for Figure 5 A schematic diagram of an optical structure arranged at a reflection position, combined with Figure 5 and Figure 6 As shown, the reflection position 31 includes a first side surface N connected 1 、Middle surface N 2 and the second side N 3 ; Among them, the middle surface N 2 is a reflective surface; the first side surface N 1 Parallel to the incident light; second side N 3 Parallel to the reflected light; the slope of the reflecting surface adjusts with the reflection position.

[0093] Specifically, we need to add the outer surface M of the light 2 An optical structure 32 with a desired slope is provided at the reflection position 31, such as Figure 5 Optionally, the refractive index of the optical structure 32 is set to be consistent with the refractive index of the curved waveguide substrate 10. The optical structure 32 includes three sides, a middle surface N 2 is the working surface, i.e. the hypotenuse with the required slope, the first side surface N on the right 1 Parallel to the incident light, the second side N on the left 3 Parallel to the reflected light, according to the angular relationship of the reflection position provided in the above embodiment, the slope of the working surface N3 is modulated with the reflection position, so the angles between the left and right hypotenuses and the working surface are not fixed.

[0094] Based on the above embodiments, Figure 5 and Figure 6 As shown, the middle surface N of the optical structure 32 2 The filter film is plated, and the filter film includes a monochromatic filter film or a filter film that transmits at least two colors; the incident angle of the filter film meets the angle range of total reflection of the image light on the curved waveguide substrate 10.

[0095] For example, refer to Figure 6 As shown, in the middle surface N 2 A layer of functional filter film is coated to fully reflect light at a specific incident angle. For example, the functional filter film satisfies the total reflection angle range of 40-70°; or, the functional filter film has a reflectivity of more than 90% for light in a specific band. In some embodiments, it can be selected to selectively reflect one or two of red light, green light, and blue light; in some embodiments, it can be selected to have a reflectivity of more than 90% for light in the visible light band emitted by the optical machine. The reflectivity of the reflection position 31 can be increased by coating, thereby improving the image display effect;

[0096] Based on the above embodiments, continue to refer to Figure 1 and Figure 2 As shown, along the propagation direction of the image light S in the curved waveguide substrate 10, the reflectivity of the n reflection positions 31 gradually increases.

[0097] Specifically, continue to combine Figure 5 and Figure 6 As shown, in some applications, the diffraction waveguide can use a binocular single-lens machine, that is, the image light S emitted by the machine is coupled into the diffraction waveguide substrate 10 from the left and right sides of the diffraction waveguide, and the image light S is transmitted to both sides at the same time. At this time, the reflection positions 31 at the left and right eyes are set to have opposite tilt directions. In order to avoid light crosstalk, a feasible implementation method is to adjust the reflectivity of the filter film on the middle surface N2 of the optical structure 32 on the reflection position 31, such as the reflectivity of the left and right reflection positions gradually increases to 100% as the distance from the coupling distance increases, so as to balance the light uniformity of the outcoupling area.

[0098] Based on the above embodiments, Figure 5 and Figure 7 As shown, a reflection grating is arranged on the middle surface N2 of the optical structure 32; the reflection grating includes a slanted grating, and the number of grating layers may also be multiple layers.

[0099] Specifically, refer to Figure 7 As shown, a multi-layer slant grating is arranged on the middle surface N2 of the optical structure 32. By adjusting the grating parameters such as the inclination angle of the slant grating, the reflection efficiency of the slant grating reaches 99%.

[0100] In addition, when the coupling structure in the coupling region uses a diffractive optical element, since the diffraction angles of light of different wavelengths are different, the propagation angles of light of different wavelengths in the curved waveguide are different. The longer the wavelength, the larger the diffraction angle. The angles of blue and red light in the curved waveguide substrate are quite different. In order to achieve better color uniformity, multiple curved waveguides can be superimposed. Different curved waveguides propagate light of different wavelengths. The curvature radius of each curved waveguide is different. The curved waveguide that propagates longer wavelengths has a larger curvature radius. The thickness of each curved waveguide can be different. The thickness of the curved waveguide that propagates longer wavelengths is thinner.

[0101] As an example, a monochromatic light machine emits image light S 11 , another monochromatic light machine emits image light S 12 , image ray S 12 The wavelength λ 12 Greater than the image light S 11 The wavelength λ 11 , that is, 12 >λ 11 , such as red-green light and blue-green light; the curvature radius of the inner curved surface of the second curved waveguide substrate 12 is greater than the curvature radius of the inner curved surface of the first curved waveguide substrate 11, and the first curved waveguide substrate 11 is used to propagate the image light S 11 , using the second curved waveguide substrate 12 to propagate the image light S 12 ; With this setting, the image ray S 11 The image light S is coupled out from the outcoupling region of the first curved waveguide substrate 11. 12 The coupled light is coupled out from the coupling area of ​​the second curved waveguide substrate 12, and the coupled light is mixed to form an image display. The curved waveguide substrate with a larger curvature radius is used to propagate image light with a longer wavelength, which can better achieve the color uniformity of the image display. Furthermore, the thickness of the optical functional area of ​​the first curved waveguide substrate 11 is greater than the thickness of the optical functional area of ​​the second curved waveguide substrate 12. The curved waveguide substrate with a thinner thickness is used to propagate image light with a longer wavelength, which can better achieve the color uniformity of the image display.

[0102] In addition, when the coupling region is a diffractive optical element and the scene is not monochromatic, the optical machine needs to be calibrated to compensate for the dispersion effect caused by the coupled diffraction. Specifically, the image lights corresponding to multiple monochrome images of different colors are projected respectively by a laser beam scanning optical machine, and the image lights are imaged and displayed after passing through the aforementioned curved waveguide; and when projecting image lights of any color among the image lights of multiple monochrome images of different colors, the scanning angle of the laser beam scanning optical machine is adjusted to make the display position of the monochrome image corresponding to the image light approach the target position. When the display position of the monochrome image corresponding to the image light reaches the target position, the corresponding scanning angle of each image pixel in the monochrome image corresponding to the image light is recorded; wherein the target position is the display position where there is no dispersion and no distortion in theory; multiple monochrome images of different colors are displayed as a color image when they overlap; the adjustment of the scanning angle is used to compensate for the dispersion and distortion caused by the diffraction of image lights of different colors.

[0103] Based on the same inventive concept, an embodiment of the present application further provides a head-mounted display, comprising any curved waveguide provided in the above embodiments. Figure 8 A side view of a head mounted display provided in an embodiment of the present application; Fig. 9 A top view of a head mounted display provided in an embodiment of the present application. Figure 8 and Fig. 9 As shown, the head mounted display 300 further includes at least one optical engine 100 and at least one image collector 200; the image collector 200 is located to obtain peripheral images, and transmits the peripheral images through the optical engine 100 to the output end of the curved waveguide for display. Furthermore, the coupling region of the curved waveguide may be located at the side, top or back of the head mounted display 300;

[0104] Specific, combined Figure 8 As shown, the head mounted display 300 may be a helmet, which may be monocular or binocular, and the binocular may use a single optical machine 100 or a dual optical machine 100; when a binocular single optical machine 100 is used, the coupling region may be set at the rear side of the head mounted display 300, and the image light S may be transmitted to both sides at the same time, as shown in FIG. Fig. 9 As shown, at this time, the reflection positions at the left and right eyes are set with opposite tilt directions. In order to avoid light crosstalk, the reflectivity of the reflection position needs to be modulated, that is, the reflectivity of the reflection positions on the left and right sides gradually increases to 100% as the distance of the coupling increases.

[0105] Combination Figure 8 As shown, the image collector 200 can adopt a high-definition small camera, and 1-3 cameras can be set at the rear of the helmet to shoot the road conditions behind, and at the same time transmit the photographed road condition information to the optical machine 100, and the optical machine 100 transmits the video image information to the output end of the waveguide substrate for display.

[0106] In summary, compared with traditional lens-type flat waveguides, the head-mounted display of the present application has a curved display structure, a larger usable area, and a larger image receivable range. The shape of the helmet also provides more possibilities for the installation location of the optical machine and the circuit board. It is more beautiful, has greater design flexibility, puts less pressure on the ears, and has better application prospects.

[0107] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and the features of the various embodiments of the present invention may be combined with each other in part or in whole, and may cooperate with each other in various ways and be technically driven. It is possible for those skilled in the art to make various obvious changes, readjustments, combinations and substitutions without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A curved waveguide, It is characterized in that include: at least one curved waveguide substrate; At least one coupling-in region is disposed on at least one side of the curved waveguide substrate; the coupling-in region is used to couple the image light emitted by the optical machine into the curved waveguide substrate; A coupling-out region is arranged on the inner curved surface of the curved waveguide substrate and is located on the transmission optical path of the image light, and is used to couple the image light out of the curved waveguide substrate; the coupling-out region includes a diffractive optical element; Among them, in the same curved waveguide substrate, the coupling-in region and the region between the coupling-in region and the coupling-out region are optical functional regions, the optical functional region and the coupling-out region have the same curvature radius of the inner curved surface corresponding to the curved waveguide substrate, and the optical functional region has the same curvature radius of the outer curved surface corresponding to the curved waveguide substrate; along the propagation direction of the image light, the outer curved surface of the coupling-out region corresponding to the curved waveguide substrate is a free curved surface and the curvature radius gradually increases.

2. The curved waveguide according to claim 1, It is characterized in that The coupling-out region includes n coupling-out positions, and the outer curved surface of the curved waveguide substrate includes n-1 reflection positions accordingly. The n coupling-out positions and the n-1 reflection positions are alternately arranged on the propagation path of the image light; wherein n≥2, and n is a positive integer; the distances from each of the n-1 reflection positions to the inner curved surface of the curved waveguide substrate and the curvature radius of the outer curved surface of the curved waveguide substrate at the n-1 reflection position are adapted so that the relationship between the emission angle of the i-th coupling-out position and the emission angle of the i+1-th coupling-out position satisfies: i i+1 =θ i +θ;i=1,2,3,4,……,n-1; Among them, θ 0 is the angle between the light and the normal after entering the curved waveguide substrate, θ 1 is the emission angle at the first outcoupling position, r is the radius of curvature of the inner side of the curved waveguide substrate, d is the thickness of the curved waveguide substrate in the optical functional area; θ is the central angle corresponding to the reflection points of two adjacent outcoupling positions, n WG is the refractive index of the curved waveguide substrate, λ is the wavelength of the image light, T is the grating period of the diffractive optical element, and as the value of i gradually increases, the i-th reflection position gradually moves away from the coupling-in region, and the i-th coupling-out position gradually moves away from the coupling-in region.

3. The curved waveguide according to claim 2, It is characterized in that The n out-coupling positions included in the out-coupling area are consistent with a reference position, and the reference position is the out-coupling position on the out-coupling area when the curvature radius of the outer curved surface of the curved waveguide substrate is the same as that of the optical functional area.

4. The curved waveguide according to claim 2, It is characterized in that An optical structure is set at the reflection position, and the optical structure includes a first side surface, a middle surface and a second side surface that are connected; wherein the middle surface is a reflection surface; the first side surface is parallel to the incident light; the second side surface is parallel to the reflected light; and the slope of the reflection surface is adjusted with the reflection position.

5. The curved waveguide according to claim 4, It is characterized in that The intermediate surface is coated with a filter film, which includes a monochromatic filter film or a filter film that transmits at least two colors; the incident angle of the filter film satisfies the angle range of total reflection of the image light on the curved waveguide substrate.

6. The curved waveguide according to claim 4, It is characterized in that A reflection grating is arranged on the intermediate surface; the reflection grating comprises a slanted tooth grating.

7. The curved waveguide according to claim 4, It is characterized in that The refractive index of the optical structure is consistent with the refractive index of the curved waveguide substrate.

8. The curved waveguide according to claim 2, It is characterized in that Along the propagation direction of the image light in the curved waveguide substrate, the reflectivities of the n reflection positions gradually increase.

9. The curved waveguide according to claim 1, It is characterized in that The curved waveguide includes a plurality of curved waveguide substrates stacked in layers; The optical functional areas of at least two of the curved waveguide substrates have different curvature radii, and the curved waveguide substrates with different curvature radii propagate incident light rays of different wavelengths.

10. A head mounted display, It is characterized in that A curved waveguide comprising the curved waveguide according to any one of claims 1 to 9, further comprising at least one optical machine and at least one image collector; The image collector is used to acquire the surrounding image, and transmit the surrounding image through the optical machine to be displayed at the output end of the curved waveguide.

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