Holographic waveguide-based near-eye display

Abstract

The present invention discloses a near-eye display based on holographic waveguide, comprising: an optical waveguide and an array light source, an in-coupling optical element, a reflective spatial light modulator, and an out-coupling optical element arranged on both sides of the optical waveguide; the array light source and the in-coupling optical element are located on opposite sides of the optical waveguide; the opposite side of the out-coupling optical element is the viewpoint of the human eye; the light emitted by the array light source is reflected by the in-coupling optical element, irradiated on the reflective spatial light modulator, modulated by the reflective spatial light modulator, and then reflected on the out-coupling optical element, and the modulated light is guided out of the optical waveguide into the human eye by the out-coupling optical element; the reflective spatial light modulator is synchronized with the driving signal of the array light source. The display structure of the present invention can greatly reduce the size of the optical system, increase the field of view of the holographic imaging, and improve the viewing experience of the user.

Description

Technical Field

[0001] The present invention belongs to the technical field of near-eye display systems, and specifically is a near-eye display based on holographic waveguide and a holographic light field augmented reality display technology based on optical waveguide. Background Art

[0002] In recent years, many well-known high-tech companies at home and abroad have been working hard to develop virtual reality and augmented reality technologies. However, most of the current near-eye display solutions use some optical elements, such as free-form surfaces, optical lenses, semi-transparent and semi-reflective mirrors, optical waveguides, etc., to project the image source content of the display system placed in a non-clear vision distance into the pupil. However, there are still many challenges in the current solutions, such as miniaturization and lightness of the device, low power consumption of the system, high image resolution, real-time rendering, and most importantly, visual comfort. In order to ensure that users can use the device for a long time, a good viewing experience is essential. Unfortunately, there is currently no solution that can effectively solve all of the above problems at the same time.

[0003] The basic principle of holographic display is the interference recording and diffraction reproduction of light waves. This kind of display can provide all the depth clues and motion parallax information required by the human eye, thereby avoiding visual fatigue caused by the conflict between monocular focusing and binocular convergence. Therefore, it is considered to be an ideal true 3D display technology. However, due to the limitations of the display principle, there are problems such as severe resolution loss, small field of view, and complex optical path, resulting in poor imaging quality of this solution, making it difficult to apply and promote it to the commercial market.

[0004] The Chinese patent with the publication number CN105487170A discloses a holographic optical waveguide, which belongs to the field of augmented reality and virtual reality technology. It includes a flat optical waveguide and an optical coupling end and an optical coupling end respectively arranged at both ends of the flat optical waveguide; the optical coupling end reflects the received light so that the reflected light meets the total reflection condition, and is transmitted to the optical coupling end after multiple total reflections between the two reflection surfaces of the flat optical waveguide, and the optical coupling end diffracts the received light out; the optical coupling end is a holographic grating; the holographic grating is a polarization holographic liquid crystal grating, including a transparent substrate, a light orientation layer, and a liquid crystal layer arranged in sequence, and a polarization holographic pattern with a periodic structure is recorded on the light orientation layer. The present invention also discloses a holographic optical waveguide display device. The present invention uses a polarization holographic liquid crystal grating as the optical coupling end of the holographic optical waveguide, which can theoretically make the diffraction efficiency reach 100%, and at the same time can suppress the zero-order wave and eliminate the conjugate image. However, the display device suffers from a serious loss in resolution and a small viewing angle, and cannot provide a good viewing experience. Summary of the invention

[0005] The purpose of the present invention is to address the problems existing in the prior art and provide a near-eye display based on holographic waveguide, which can greatly reduce the size of the optical system, increase the field of view of the holographic imaging, and enhance the user's viewing experience.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A near-eye display based on a holographic waveguide comprises: an optical waveguide and an array light source, an in-coupling optical element, a reflective spatial light modulator, and an out-coupling optical element arranged on both sides of the optical waveguide; the array light source and the in-coupling optical element are located on opposite sides of the optical waveguide; the opposite side of the out-coupling optical element is the viewpoint of a human eye; the light emitted by the array light source is reflected by the in-coupling optical element, irradiated onto the reflective spatial light modulator, modulated by the reflective spatial light modulator, and then reflected onto the out-coupling optical element, and the modulated light is guided out of the optical waveguide by the out-coupling optical element into the human eye; the reflective spatial light modulator is synchronized with the driving signal of the array light source.

[0008] Specifically, the array light source is a programmable light emitting unit array; the array light source includes a micro LED array, a laser light source array, a liquid crystal display system or an OLED display system;

[0009] The light-emitting units at any position on the array light source can be individually lit or turned off;

[0010] The array light source is a monochromatic light source or a white light source.

[0011] Specifically, the reflective spatial light modulator is a reflective phase spatial light modulator or a reflective amplitude spatial light modulator.

[0012] Furthermore, when a light-emitting unit at a certain position in the array light source is lit, the array light source will synchronously send a driving signal to the reflective phase-type spatial light modulator, and the modulator will synchronously display a corresponding phase diagram.

[0013] If the reflective spatial light modulator is a reflective amplitude spatial light modulator, when the light-emitting units in the array light source are illuminated in a time-division multiplexing manner, an amplitude modulated image will be synchronously displayed on the modulator; the position of the human eye will form a multi-viewpoint light field convergence, thereby realizing a three-dimensional light field display.

[0014] Specifically, the in-coupling optical element is a holographic optical element, a diffractive optical element or a wedge-shaped reflective mirror attached to the surface of the optical waveguide; the wavelength selectivity of the holographic optical element can be utilized to achieve a color holographic effect by using spatial multiplexing.

[0015] Specifically, the outcoupling optical element is a holographic optical element attached to the surface of the optical waveguide, and is used to guide the light modulated by the reflective spatial light modulator out of the optical waveguide or to converge the light while guiding the light out of the optical waveguide.

[0016] Furthermore, the out-coupling optical element is a simple-function holographic optical element or a complex-function holographic optical element; if the out-coupling optical element is a simple-function holographic optical element, its function is to guide the light modulated by the reflective spatial light modulator out of the optical waveguide and into the human eye; if the out-coupling optical element is a complex-function holographic optical element, its function, in addition to guiding the light out of the optical waveguide, also has the converging function of a positive lens.

[0017] Specifically, the out-coupling optical element adopts a holographic optical element with a certain angular bandwidth, which, in conjunction with an array light source, can effectively increase the exit pupil area, thereby increasing the field of view angle.

[0018] Specifically, the optical waveguide is a flat structure or a curved structure.

[0019] Specifically, the array light source and the reflective spatial light modulator are located on the same side or different sides of the optical waveguide; the in-coupling optical element and the reflective spatial light modulator are located on the same side or different sides of the optical waveguide; the out-coupling optical element and the reflective spatial light modulator are located on the same side or different sides of the optical waveguide.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) by bonding an array light source and a reflective spatial light modulator to an optical waveguide device, the present invention can greatly reduce the size of the optical system, thereby providing technical support for the miniaturization of wearable devices; (2) the present invention uses an array light source to effectively increase the field of view of holographic imaging, thereby improving the viewing experience of users; (3) the reflective spatial light modulator and the array light source of the present invention are controlled by synchronous driving signals. When the light-emitting units at different positions in the array light source are illuminated, the array light source will synchronously send a driving signal to the reflective spatial light modulator; when the reflective spatial light modulator is an amplitude-type spatial light modulator, the light-emitting units in the array light source are illuminated in a time-division multiplexing manner, which will form a multi-viewpoint light field convergence at the pupil position, thereby realizing three-dimensional light field display. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of a near-eye display based on a holographic waveguide according to Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of the optical path of a near-eye display based on a holographic waveguide according to Embodiment 1 of the present invention;

[0023] Figure 3This is a schematic diagram of the optical waveguide structure with a curved surface in Example 1 of the present invention;

[0024] Figure 4 Schematic diagram of the structure in which the in-coupling optical element is a wedge-shaped reflective arc surface in Example 1 of the present invention;

[0025] Figure 5 It is a schematic diagram of synchronous transmission of signals between the light source array and the reflective spatial light modulator in the present invention;

[0026] Figure 6 Schematic diagram of the light path corresponding to the first light-emitting unit in Embodiment 2 of the present invention;

[0027] Figure 7 Schematic diagram of the light path corresponding to the second light-emitting unit in Embodiment 2 of the present invention;

[0028] In the figure: 1. optical waveguide; 2. array light source; 3. in-coupling optical element; 4. reflective spatial light modulator; 5. out-coupling optical element; 6. human eye; 7. first light-emitting unit; 8. eyepiece; 9. light field convergence point of the first viewpoint; 10. second light-emitting unit; 11. light field convergence point of the second viewpoint. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only 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 are within the scope of protection of the present invention.

[0030] Example 1

[0031] like Figure 1 , 2 As shown, this embodiment provides a near-eye display based on a holographic waveguide, comprising: an optical waveguide 1 and an array light source 2, an in-coupling optical element 3, a reflective spatial light modulator 4, and an out-coupling optical element 5 arranged on both sides of the optical waveguide 1; the array light source 2 and the in-coupling optical element 3 are located on opposite sides of the optical waveguide 1; the opposite side of the out-coupling optical element 5 is the viewpoint position of a human eye 6; the light emitted by the array light source 2 is reflected by the in-coupling optical element 3, irradiated onto the reflective spatial light modulator 4, modulated by the reflective spatial light modulator 4, and then reflected onto the out-coupling optical element 5, and the out-coupling optical element 5 guides the modulated light out of the optical waveguide 1 and into the human eye 6; the reflective spatial light modulator 4 is synchronized with the driving signal of the array light source 2.

[0032] Specifically, the array light source 2 is a programmable light emitting unit array; the array light source 2 may be a micro LED array, a laser light source array, a liquid crystal display system or an OLED display system;

[0033] The light-emitting units at any position on the array light source 2 can be individually lit or turned off;

[0034] The array light source 2 is a monochromatic light source or a white light source.

[0035] Specifically, the reflective spatial light modulator 4 is a reflective amplitude spatial light modulator, which is used to load the projection sub-image;

[0036] The reflective amplitude-type spatial light modulator and the programmable light-emitting units arranged in an array are driven by a synchronization signal. When the light-emitting units at different positions in the array light source 2 are illuminated, the amplitude-type spatial light modulator will display the corresponding projection sub-image. Different projection sub-images correspond to information of target objects at different viewpoints.

[0037] Specifically, the optical waveguide 1 is a flat plate structure, and the optical path schematic diagram in the optical waveguide 1 is as follows: Figure 2 As shown;

[0038] Optionally, the optical waveguide 1 may also be Figure 3 The curved structure shown is used to adapt to specific viewing scenarios.

[0039] Specifically, the in-coupling optical element 3 is a holographic optical element or a nanoscale diffraction grating attached to the surface of the optical waveguide 1;

[0040] Specifically, Figure 4 As shown, the in-coupling optical element 3 may also adopt a holographic optical element with a wedge-shaped reflective arc surface structure. The use of the holographic optical element with a wedge-shaped reflective arc surface structure can improve the coupling efficiency of the in-coupling optical element 3 .

[0041] Specifically, the out-coupling optical element 5 is a holographic optical element attached to the surface of the optical waveguide 1 , and is used to guide the light modulated by the reflective spatial light modulator 4 out of the optical waveguide 1 and into the human eye 6 .

[0042] The out-coupling optical element 5 is a composite holographic optical element having a combination of a reflector and a convex lens, such as Figure 2 As shown, the human eye 6 can view directly on the opposite side of the outcoupling optical element 5 .

[0043] The holographic optical elements all have a certain angular bandwidth, which can increase the exit pupil area, thereby increasing the field angle of holographic imaging.

[0044] Specifically, the array light source 2 and the reflective spatial light modulator 4 are located on the same side or different sides of the optical waveguide 1; the in-coupling optical element 3 and the reflective spatial light modulator 4 are located on the same side or different sides of the optical waveguide 1; the out-coupling optical element 5 and the reflective spatial light modulator 4 are located on the same side or different sides of the optical waveguide 1.

[0045] The display principle of this embodiment is as follows: when the control circuit of the light source array gives a light source signal to light up the light-emitting unit at the corresponding position in the light source array, the light source signal will also synchronously cause the display control circuit to send a display signal, so that the reflective amplitude-type spatial light modulator displays the projection sub-image of the corresponding viewpoint; when the light-emitting unit in the array is lit, the other light-emitting units are turned off, and the light emitted by the light-emitting unit passes through the in-coupling optical element 3, and after the light is totally reflected several times in the waveguide at an angle θ, it is irradiated onto the reflective amplitude-type spatial light modulator to be modulated and reflected. At this time, the light carries the projection sub-image related information of the viewpoint, and after several total reflections, it is irradiated on the out-coupling optical element 5 (a composite holographic optical element with a combination of a reflector and a convex lens) and converged to output the optical waveguide 1, forming a light field at the position of the human eye 6; by lighting up other light-emitting units in sequence in a time-division multiplexing manner, a three-dimensional square convergence of multiple viewpoints will be formed at the position of the human eye 6. If the refresh rate is high enough, the light field convergence at the position of the human eye 6 will be regarded by the human eye as a light field transmitted simultaneously, and the complete light field information will be reconstructed on the retina.

[0046] Example 2

[0047] like Figures 5 to 7 As shown, this embodiment provides a near-eye display based on a holographic waveguide. The difference from the above-mentioned embodiment 1 is that in this embodiment, the outcoupling optical element 5 adopts a simple functional holographic optical element with only a reflector function. At this time, it is necessary to add an eyepiece 8 in front of the human eye 6 in the optical system; the human eye 6 watches behind the eyepiece 8.

[0048] In this embodiment, Figure 6 , 7 As shown, when the first light-emitting unit 7 emits light, the reflective amplitude-type spatial light modulator will display the projection sub-image of the first viewpoint; when the light carrying the relevant information of the projection sub-image of the first viewpoint passes through the optical waveguide 1 for several total reflections and irradiates the out-coupling optical element 5 (a simple functional holographic optical element having only the function of a reflector) and is guided out of the optical waveguide 1 to form a light field, the light field is converged by the eyepiece 8 to form a light field convergence point 9 of the first viewpoint at the position of the human eye 6; similarly, when the second light-emitting unit 10 emits light, the reflective amplitude-type spatial light modulator will display the projection sub-image of the second viewpoint; and finally a light field convergence point 11 of the second viewpoint will also be formed at the position of the human eye 6.

[0049] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A near-eye display based on a holographic waveguide, characterized in that: include: An optical waveguide and an array light source, an in-coupling optical element, a reflective spatial light modulator, and an out-coupling optical element arranged on both sides of the optical waveguide; The array light source and the in-coupling optical element are located on opposite sides of the optical waveguide; The opposite side of the out-coupling optical element is the viewpoint of the human eye; the light emitted by the array light source is reflected by the in-coupling optical element, irradiated onto the reflective spatial light modulator, modulated by the reflective spatial light modulator, and then reflected onto the out-coupling optical element, and the out-coupling optical element guides the modulated light out of the optical waveguide into the human eye; The reflective spatial light modulator is synchronized with a driving signal of the array light source; The optical waveguide is a flat structure or a curved structure, and the in-coupling optical element of the curved structure adopts a holographic optical element with a wedge-shaped reflective arc surface structure; the out-coupling optical element adopts a simple function holographic optical element or a composite function holographic optical element with a certain angular bandwidth; the reflective spatial light modulator is a reflective amplitude spatial light modulator.

2. The near-eye display based on holographic waveguide according to claim 1, characterized in that: The array light source is a programmable light emitting unit array; the array light source includes a micro LED array, a laser light source array, a liquid crystal display system or an OLED display system; The light-emitting units at any position on the array light source can be individually lit or turned off; The array light source is a monochromatic light source or a white light source.

3. The near-eye display based on holographic waveguide according to claim 1, characterized in that: The reflective spatial light modulator is a reflective phase spatial light modulator or a reflective amplitude spatial light modulator.

4. The near-eye display based on holographic waveguide according to claim 1, characterized in that: The in-coupling optical element is a holographic optical element, a diffractive optical element or a wedge-shaped reflecting mirror adhered to the surface of the optical waveguide.

5. The near-eye display based on holographic waveguide according to claim 1, characterized in that: The outcoupling optical element is a holographic optical element attached to the surface of the optical waveguide, and is used to guide the light modulated by the reflective spatial light modulator out of the optical waveguide or to converge the light while guiding the light out of the optical waveguide.

6. The near-eye display based on holographic waveguide according to claim 1, characterized in that: The array light source and the reflective spatial light modulator are located on the same side or different sides of the optical waveguide; the in-coupling optical element and the reflective spatial light modulator are located on the same side or different sides of the optical waveguide; the out-coupling optical element and the reflective spatial light modulator are located on the same side or different sides of the optical waveguide.

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