Near-to-eye display device with symmetrical input and high-uniformity output

Abstract

The invention discloses a near-to-eye display device with symmetrical input and high-uniformity output. The near-to-eye display device structurally comprises an image source, a collimation system, an optical waveguide, a coupling-in element and a coupling-out element. Light emitted by the image source is collimated by the collimation system, then enters the optical waveguide from the symmetrical coupling-in elements at the two ends of the waveguide, is totally emitted in the optical waveguide, reaches the coupling-out elements, and is coupled out to enter human eyes. The coupling-in element designed by the invention has high diffraction efficiency, and the coupling-out element has gradually-changed diffraction efficiency, so that the output brightness and uniformity are improved.

Description

Technical Field

[0001] The present invention relates to the field of display, and in particular to a near-eye display device with symmetrical input and high-uniformity output. Background Art

[0002] Currently, virtual reality (VR) and augmented reality (AR) technologies have attracted much attention. VR technology can immerse people in a virtual environment, while AR technology can enable people to receive information about the real environment while observing virtual images, thus realizing the interaction between the virtual world and the real world. They have been applied to military, medical, education, consumption and other fields. Compared with traditional prism, Birdbath, free-form surface and other technologies, the diffraction waveguide solution has a wider field of view, higher transparency and larger eye movement range, and is gradually becoming the mainstream direction of future development.

[0003] However, the diffraction waveguide solution also has some problems. Since light will be reflected multiple times when passing through the coupling element, although pupil expansion is achieved, light is coupled out each time it is reflected by the coupling element, resulting in a decrease in the uniformity of the final output light. In addition, since AR devices often need to be used outdoors, sometimes the strong sunlight outdoors can cause insufficient output brightness. Therefore, the present invention proposes a structure that improves the output uniformity while enhancing the output brightness. Summary of the invention

[0004] The present invention provides a near-eye display device with symmetrical input and high uniformity output, which has strong output brightness and high uniformity of output light, so as to solve the problems of insufficient output brightness and poor uniformity of AR color plates in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A near-eye display device with symmetrical input and high uniformity output comprises an optical waveguide, a first coupling element and a second coupling element are arranged on the surface of the optical waveguide, the first coupling element and the second coupling element are symmetrical in structure, a plurality of coupling elements are arranged between the first coupling element and the second coupling element, and the plurality of coupling elements are arranged along a straight line determined by the first coupling element and the second coupling element; The first coupling element and the second coupling element are each configured with an image source. The image light output by the image source corresponding to the first coupling element is diffracted by the first coupling element to form diffracted light with a diffraction angle greater than the total reflection angle in the optical waveguide. The image light output by the image source corresponding to the second coupling element is diffracted by the second coupling element to form diffracted light with a diffraction angle greater than the total reflection angle in the optical waveguide. The diffracted light formed by the first coupling element and the second coupling element respectively enters the optical waveguide and is totally reflected multiple times in the optical waveguide before reaching each coupling element, and is finally diffracted and coupled out to the human eye through each coupling element.

[0006] Furthermore, the image light output by each image source is collimated into parallel light by the collimation system and then output to the corresponding coupling element.

[0007] Furthermore, the first coupling element is a tilted grating, and the structural parameters of the tilted grating as the first coupling element are: period 480 nm, grating height 500 nm, duty cycle 50%, and tilt angle -24°.

[0008] Furthermore, the second coupling element is a tilted grating, and the structural parameters of the tilted grating as the second coupling element are: period 480 nm, grating height 500 nm, duty cycle 50%, and tilt angle 24°.

[0009] Furthermore, each out-coupling element is a rectangular grating, and a plurality of rectangular gratings are arranged at equal intervals along a straight line defined by the first in-coupling element and the second in-coupling element.

[0010] Furthermore, the diffraction efficiency of each rectangular grating serving as an outcoupling element changes gradually along the linear arrangement direction.

[0011] Compared with the prior art, the present invention improves the brightness of the output image while also improving the uniformity of the output image. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the optical path principle diagram of the present invention.

[0013] Figure 2 This is the first coupling grating structure diagram in the present invention.

[0014] Figure 3 yes Figure 2 Diffraction efficiency diagram of the grating in Figure 2.

[0015] Figure 4 This is a diagram of the second coupling grating structure in the present invention.

[0016] Figure 5 yes Figure 4 Diffraction efficiency diagram of the grating in Figure 2.

[0017] Figure 6 The incident light passes through Figure 2 Schematic diagram of the diffraction angle after the central grating.

[0018] Figure 7 The incident light passes through Figure 4 Schematic diagram of the diffraction angle after the central grating.

[0019] Figure 8 It is a schematic diagram of the diffraction efficiency distribution of the outcoupling element. DETAILED DESCRIPTION

[0020] like Figure 1As shown, this embodiment discloses a near-eye display device with symmetrical input and high uniformity output, including two groups of image sources 101, two groups of collimation systems 102, an optical waveguide 103, a first coupling element 104, a second coupling element 105, and a total of four coupling elements 106-109.

[0021] The first coupling element 104 is disposed on the left side of the front surface of the optical waveguide 103, and the second coupling element 105 is disposed on the right side of the front surface of the optical waveguide 103. The first coupling element 104 is configured with one set of image sources and collimation systems, and the second coupling element 105 is configured with another set of image sources and collimation systems.

[0022] The light emitted from the image source 101 on the left and right sides of the optical waveguide 103 is collimated into parallel light after passing through the collimation system 102, and then enters the first coupling element 104 on the left side of the front side of the optical waveguide 103 and the second coupling element 105 on the right side of the front side of the optical waveguide 103 respectively.

[0023] The first coupling element 104 and the second coupling element 105 have symmetrical structures. Specifically, the structure of the first coupling element 104 on the left side of the front side of the optical waveguide 103 is a tilted grating, and its structural schematic diagram is shown in FIG. Figure 2 As shown in FIG. 1 , the structural parameters of the tilted grating as the first coupling element 104 are: period 480nm, grating height 500nm, duty cycle 50%, tilt angle -24°. The structure of the second coupling element 105 on the right side of the front side of the optical waveguide 103 is a tilted grating, and its structural schematic diagram is shown in FIG. Figure 4 As shown, the structural parameters of the tilted grating used as the second coupling element 105 are: period 480 nm, grating height 500 nm, duty cycle 50%, and tilt angle 24°.

[0024] The collimated parallel light output by the image source configured by the first coupling element 104 will be diffracted after entering the first coupling element 104. The main efficiency of the first coupling element 104 is concentrated in the +1 order. The diffraction efficiency of the +1 order is as follows: Figure 3 The collimated parallel light output by the image source configured by the second coupling element 105 will be diffracted after passing through the second coupling element 105. The main efficiency of the second coupling element 105 is concentrated in the -1 order. The diffraction efficiency of the -1 order is as follows: Figure 5 shown.

[0025] The +1-order diffraction angle of the first coupling element 104 is as follows: Figure 6 As shown, the -1 order diffraction angle of the second coupling element 105 is as follows: Figure 7 As shown, since the structures of the first coupling element 104 and the second coupling element 105 are symmetrical, the +1st order diffraction angle of the first coupling element 104 and the -1st order diffraction angle of the second coupling element 105 are opposite to each other.

[0026] The diffraction angle of the +1-order diffraction light formed by the first coupling element 104 and the diffraction angle of the -1-order diffraction light formed by the second coupling element 105 are both greater than the total reflection angle in the optical waveguide 103. Therefore, the diffraction light will continue to undergo multiple total reflections in the waveguide and then reach each coupling-out element 106-109, and then be diffracted and coupled out by each coupling-out element 106-109 to enter the human eye.

[0027] The out-coupling elements 106-109 are all rectangular gratings. The rectangular gratings constituting the out-coupling elements are arranged continuously and evenly spaced along the straight line determined by the first coupling element 104 and the second coupling element 105. The schematic diagram of the structure of the rectangular grating as the out-coupling element and the diffraction efficiency distribution are shown in FIG. Figure 8 As shown, in order to solve the problem that pupil expansion will cause the output energy to decrease each time, the output uniformity is improved by setting a gradual diffraction efficiency.

[0028] In this embodiment, the duty cycle and grating height of the out-coupling elements 106 - 109 can be adjusted to achieve a gradual diffraction efficiency, and the out-coupling elements and the in-coupling elements are set to have the same period to ensure phase matching.

[0029] In this embodiment, the diffraction efficiency distribution diagram of the outcoupling elements 106-109 is shown in FIG. Figure 8 As shown, the efficiency of the output light is analyzed below: First outcoupling energy: ; Second outcoupling energy: ; The third outcoupling energy: ; The fourth outcoupling energy: .

[0030] It should be noted that in Figure 8 In the schematic diagram, the energy of the incident light after diffraction by the coupling element is marked as 100%, which means the total energy of the subsequent total reflection, rather than the total energy of the incident light. This is only exemplary. According to calculations, when other values ​​are taken, the coupled energies after passing through the coupling element are also approximately equal.

[0031] The light emitted by the image source 101 arranged on the left and right sides of the optical waveguide 103 undergoes a symmetrical phase change, and when reaching the outcoupling element, the output brightness is improved compared to when only a single image source is input. The output brightness of the image source 101 is set to be adjustable, so in an environment with strong sunlight, the brightness of the image source can be reasonably adjusted without being adjusted to the maximum, which can not only extend the service life of the image source, but also meet the use requirements in a strong light environment.

[0032] The present embodiment provides a near-eye display device with symmetrical input and high uniformity output, which improves the uniformity of the output result and the brightness under strong light conditions by adopting double-sided image input, first and second coupling-in elements with high diffraction efficiency, and an output coupling element with gradually varying diffraction efficiency.

[0033] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction, and such combinations should also be regarded as the contents disclosed in the present disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0034] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by technical personnel in this field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A near-eye display device with symmetrical input and high uniformity output, characterized in that: The optical waveguide comprises a first coupling element and a second coupling element on the surface of the optical waveguide, the first coupling element and the second coupling element are symmetrical in structure, a plurality of coupling elements are arranged between the first coupling element and the second coupling element, and the plurality of coupling elements are arranged along a straight line determined by the first coupling element and the second coupling element; The first coupling element and the second coupling element are each configured with an image source. The image light output by the image source corresponding to the first coupling element is diffracted by the first coupling element to form diffracted light with a diffraction angle greater than the total reflection angle in the optical waveguide. The image light output by the image source corresponding to the second coupling element is diffracted by the second coupling element to form diffracted light with a diffraction angle greater than the total reflection angle in the optical waveguide. The diffracted light formed by the first coupling element and the second coupling element respectively enters the optical waveguide and is totally reflected multiple times in the optical waveguide before reaching each coupling element, and is finally diffracted and coupled out to the human eye through each coupling element.

2. The near-eye display device with symmetrical input and high uniformity output according to claim 1, characterized in that: The image light output by each image source is collimated into parallel light by the collimation system and then output to the corresponding coupling element.

3. The near-eye display device with symmetrical input and high uniformity output according to claim 1, characterized in that: The first coupling element is a tilted grating, and the structural parameters of the tilted grating as the first coupling element are: period 480 nm, grating height 500 nm, duty cycle 50%, and tilt angle -24°.

4. The near-eye display device with symmetrical input and high uniformity output according to claim 1, characterized in that: The second coupling element is a tilted grating, and the structural parameters of the tilted grating as the second coupling element are: period 480 nm, grating height 500 nm, duty cycle 50%, and tilt angle 24°.

5. The near-eye display device with symmetrical input and high uniformity output according to claim 1, characterized in that: Each out-coupling element is a rectangular grating, and a plurality of rectangular gratings are arranged at equal intervals along a straight line defined by the first in-coupling element and the second in-coupling element.

6. The near-eye display device with symmetrical input and high uniformity output according to claim 5, characterized in that: The diffraction efficiency of each rectangular grating as a coupling-out element changes gradually along the linear arrangement direction.

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