CN113534477B

CN113534477B - Optical assembly, display system and manufacturing method

Info

Publication number: CN113534477B
Application number: CN202010288536.3A
Authority: CN
Inventors: 杨鑫; 黄正宇
Original assignee: Beijing Yilian Technology Co ltd
Current assignee: Beijing Yilian Technology Co ltd
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2023-12-26
Anticipated expiration: 2040-04-14
Also published as: CN113534477A

Abstract

The present disclosure relates to an optical assembly comprising: a beam generator configured to emit a beam group of light cone distribution; a light conducting medium having first and second non-parallel surfaces; a first beam combiner located on the first surface; and a second beam combiner located on the second surface, wherein the first beam combiner is configured to receive the group of light beams of the light cone distribution and to change its propagation direction such that at least a portion thereof propagates through the light conducting medium onto the second beam combiner; the second beam combiner is configured to change the propagation direction of the light beam incident thereon from the first beam combiner such that it continues to propagate at a different angle away from the second beam combiner, wherein the light beams from the group of light beams of the same light cone distribution leave the second beam combiner and converge at a point. The optical component forms an image with equal proportion expansion through carrying out reverse projection compensation on a projection area and is coupled to be imaged on the retina, so that the retina imaging with a large field of view and no distortion is realized.

Description

Optical assembly, display system and manufacturing method

Technical Field

The present disclosure relates generally to the field of optical displays, and more particularly, to an imaging distortion free optical assembly based on trapezoidal back projection compensation, a display system, and a method of manufacture.

Background

With the development of computer technology and display technology, virtual Reality (VR) technology of experiencing a Virtual world through a computer simulation system and augmented Reality (Augmented Reality, AR) technology and Mixed Reality (MR) technology of fusing display contents into a real environment background have been rapidly developed.

The near-eye VR, AR and MR display technology combining the VR, AR and MR technologies with near-eye display is an important novel display technology, and can bring unprecedented visual experience and man-machine interaction to people. Near-to-eye VR displays mainly pursue virtual displays of immersed large fields of view, corresponding to virtual reality display helmets. The purpose of the near-to-eye AR and MR technology is to realize perspective virtual-real fusion, and the purpose is to augment reality intelligent glasses or helmets. In principle, near-eye display devices for AR as well as MR are also known as virtual reality technology in case of blocking the entry of ambient light into the eyes of the user.

The near-eye display device is generally configured as a helmet display device or a glasses-shaped display device, and is used for imaging an image displayed by a micro-display chip at a distance through an optical system, a human eye directly sees the displayed amplified image at the distance through the near-eye display device, meanwhile, space perception positioning is realized by combining with SLAM technology, interaction is realized through technologies such as gesture recognition, voice recognition, eye tracking and the like, and the near-eye display device is a novel display technology with important potential commercial application value and is considered to be a novel display technology hopeful to replace a smart phone.

In recent years, virtual reality display devices have been developed explosively, and various devices have been used. The international megahead companies such as Oculus, HTC, sony, samsung respectively put forward a virtual reality helmet display device, and domestic parallel reality, a roc photoelectricity and the like are actively developing virtual reality display products. Near-eye display devices for these virtual reality head-mounted displays are mostly based on the principle of single positive lens imaging, i.e. by placing the display near the object focal plane of a single positive lens so that the display passes through the single positive lens to form an erect, magnified virtual image at infinity in the object of the lens.

Near-eye display devices for AR and MR have also been greatly developed in recent years. Augmented reality products based on an augmented reality optical engine are proposed by Microsoft corporation, magic Leap corporation and the like, and the augmented reality optical engine realizes functions of image in-coupling, out-coupling, pupil expanding and the like by utilizing a diffraction optical waveguide. The described technology enables a binocular parallax based three-dimensional display or a bi-layer depth volumetric display or a generic two-dimensional display. The national long JING photoelectric, nede Jia, gudong technology and the like realize augmented reality by adopting an array waveguide or free-form surface AR eyepiece. By adopting the technology, two-dimensional display or three-dimensional display can be realized, but the problem of convergence adjustment conflict exists in the realized three-dimensional display, namely, the problem of visual fatigue, dizziness and the like caused by inconsistent focusing of eyes of a viewer and focusing of binocular visual axes, especially when viewing a virtual scene with a relatively short distance, the discomfort is stronger. Wearing this type of near-eye display device for a long period of time has the potential to compromise the vision of teenagers whose vision development is not yet mature.

One of the greatest challenges in the current helmets or glasses for augmented reality is to develop a smaller and more compact optical display core assembly, realize a three-dimensional display technology or comfortable two-dimensional display without vergence adjustment conflict, make users more comfortable to wear for a long time, and meet some specific requirements for use in specific occasions.

In addition, the retinal imaging technique is a display technique in which an image is directly projected to the retina by optical means. The traditional retina imaging technology takes a display chip such as LCoS as an image carrier, images through a lens system, and uses a half mirror to guide the image into human eyes, so that the environment light can penetrate the human eyes to realize penetration display. The lens group of the scheme is large in volume, the half-mirror can attenuate the brightness of the ambient light by half, and the compact large-view-field display module without attenuating the ambient light is an important problem to be solved in the retina imaging technology.

Further, the above-described problems are solved, and improvements are required for the conventional optical imaging apparatus and the manufacturing method thereof.

The matters in the background section are only those known to the public and do not, of course, represent prior art in the field.

Disclosure of Invention

In view of at least one of the deficiencies of the prior art, the present disclosure provides an optical assembly comprising:

a beam generator configured to emit a beam group of light cone distribution;

a light conducting medium having a first surface and a second surface, the first surface being non-parallel to the second surface;

a first beam combiner located on a first surface of the photoconductive medium; and

a second beam combiner located on a second surface of the photoconductive medium,

wherein the first beam combiner is configured to receive the set of light beams of the light cone distribution and to change its direction of propagation such that at least a portion thereof propagates through the light-conducting medium onto the second beam combiner; the second beam combiner is configured to change the propagation direction of the light beam incident on the second beam combiner from the first beam combiner, so that the light beam leaves the second beam combiner at different angles to continue to propagate, wherein the light beams from the light beam group with the same light cone distribution are converged at one point after the direction of the light beam group is changed by the first beam combiner and the second beam combiner, and the light beam group leaves the second beam combiner.

According to one aspect of the invention, the profile of the illuminated area of the beam set of the light cone distribution on any cross section perpendicular to the main direction of the beam set is proportional to the profile of the illuminated area formed on the second beam combiner.

According to one aspect of the invention, the main direction of the beam set is perpendicular to the plane in which the second beam combiner lies.

According to one aspect of the invention, the angle between the first and second beam combiners is in the range 20 ° to 80 °, preferably 45 °.

According to one aspect of the invention, the first and second beam combiners do not overlap each other in a direction perpendicular to the main direction of the beam set.

According to one aspect of the invention, the photoconductive medium comprises a waveguide, wherein the light beam exiting the first beam combiner is incident on the second beam combiner after at least one total reflection in the waveguide.

According to one aspect of the invention, the light beam exiting the first beam combiner is directly incident on the second beam combiner through the light-conducting medium.

According to one aspect of the invention, the light conducting medium is air and the first and second beam combiners are fixed by an external structure.

According to one aspect of the invention, the optical assembly has an entrance pupil and an exit pupil, the apex of the cone of light being the entrance pupil, and the point at which the beams of the group of beams originating from the same cone of light leave the second beam combiner is the exit pupil.

According to one aspect of the invention, the beam generator comprises an image source and a microelectromechanical system,

wherein the image source is configured to generate a laser beam carrying color information and/or brightness information of the image pixels; the micro-electromechanical system is configured to scan the laser beam to form a beam group of the light cone distribution,

wherein the laser beam is a monochromatic or trichromatic laser beam.

According to one aspect of the invention, the beam generator comprises:

the LED light source comprises a light source, wherein the light source is a monochromatic or trichromatic laser light source, an LED light source or an OLED light source and emits divergent illumination light;

DMD, LCoS, LCD configured to carry an image and modulate light impinging thereon by said light source in accordance with said image;

a diaphragm or lens configured to receive the modulated light to form a set of light beams of the light cone distribution.

According to one aspect of the invention, the beam generator comprises:

a lens configured to receive divergent illumination light emitted by the light source and converge at an apex of the cone of light;

DMD, LCoS, LCD are positioned between the lens and the apex and are configured to carry an image and modulate light impinging thereon after passing through the lens in accordance with the image.

According to one aspect of the invention, the MEMS comprises a MEMS galvanometer, an image generated by the image source is formed by scanning beamlets carrying color information and/or brightness information of image pixels emitted from lasers with different wavelengths through the MEMS galvanometer, the image source comprises a plurality of lasers with different wavelengths, a controller and a beam combiner, the controller is coupled with the plurality of lasers with different wavelengths and controls the plurality of lasers with different wavelengths to emit laser beams, and the laser beams of the plurality of lasers with different wavelengths are incident on the beam combiner and are combined into nearly parallel beamlets with coincident propagation paths in space.

According to one aspect of the invention, the beam combiner comprises a lens group and optical film beam splitters corresponding to the wavelengths of the lasers with different wavelengths respectively, wherein the lens group is configured to adjust the divergence angle and/or the diameter of the laser beam emitted by the lasers and cast on the corresponding optical film beam splitters to form the nearly parallel beamlets with coincident spatial propagation paths through reflection or transmission, and the lens group can comprise a liquid lens or a liquid crystal lens, and the equivalent focal length of the lens group can be adjusted through external voltage control and is used for controlling the divergence angle and/or the diameter of the laser beam emitted by the lasers.

According to one aspect of the invention, the beam combiner further comprises a diaphragm, a wave plate, a polarizing plate and an attenuation plate arranged between the lens group and the optical film beam splitter, and the beam combiner further comprises a micro motor coupled with the lens group, wherein the micro motor can adjust the relative position among lenses in the lens group so as to adjust the divergence angle and/or the diameter of the light beam emitted from the lens group.

According to one aspect of the invention, the differently directed beams of the beam set carry color information and/or brightness information for different image pixels.

According to one aspect of the present invention, the first beam combiner includes a first diffractive optical element, the group of light beams of the light cone distribution diffract when incident on different positions of the first diffractive optical element, the propagation direction of the diffracted light changes and continues to propagate in the light-conducting medium, and the diffracted light is incident on different positions of the second beam combiner;

the second beam combiner comprises a second diffractive optical element, the light beams from the first diffractive optical element are diffracted when propagating to different positions of the second diffractive optical element in different directions, the propagation direction is changed and enters free space, and the light beams which enter the free space and are diffracted in different directions from different positions of the second diffractive optical element are converged to the point in the free space.

According to one aspect of the invention, the first and second diffractive optical elements are independently volume holographic optical elements, the first and second diffractive optical elements being one of the following combinations:

the first diffraction optical element is a transmission type volume holographic optical element, and the second diffraction optical element is a reflection type volume holographic optical element; and

the first diffractive optical element is a transmissive volume hologram optical element, and the second diffractive optical element is a transmissive volume hologram optical element.

According to one aspect of the present invention, the volume hologram optical element includes a single color volume hologram optical element that diffracts laser light of different wavelengths of the plurality of lasers.

According to an aspect of the present invention, the volume hologram optical element includes a plurality of single-color volume hologram optical elements accurately aligned and stacked together, and each single-color volume hologram optical element diffracts only laser light of a corresponding wavelength and does not diffract laser light of other wavelengths corresponding to the number of the plurality of lasers.

According to one aspect of the present invention, the volume hologram optical element includes a plurality of volume hologram optical elements accurately aligned and stacked together, the number of the plurality of volume hologram optical elements being smaller than the number of the plurality of lasers, at least one of the plurality of volume hologram optical elements diffracting laser light of at least two wavelengths among the plurality of lasers, and not diffracting laser light of other wavelengths; the remaining volume hologram optical element diffracts laser light of one of the remaining other wavelengths, but does not diffract laser light of the other wavelengths.

According to one aspect of the present invention, the volume hologram optical element includes a single monochromatic volume hologram optical element diffracting only laser light of one wavelength.

According to an aspect of the present invention, the first diffractive optical element and the second diffractive optical element are independently one selected from the single color volume hologram optical element, the plurality of single color volume hologram optical elements that are aligned and stacked together and correspond to the number of lasers, the plurality of volume hologram optical elements that are aligned and stacked together and fewer than the number of lasers, and the single color volume hologram optical element.

The invention also provides a display system comprising an optical assembly as described above.

According to one aspect of the invention, the display system is a virtual reality display system or an augmented reality display system.

According to one aspect of the invention, the display system further comprises an image generating unit configured to generate an image to be displayed, the image generating unit being coupled to the beam generator, the beams of different directions in the beam group emitted by the beam generator carrying color information and/or brightness information of different pixels in the image.

According to one aspect of the invention, the display system comprises a left eye display unit and a right eye display unit, wherein the left eye display unit and the right eye display unit each comprise an optical assembly as described above.

The invention also relates to the use of an optical assembly or display system as described above for near-eye display.

The invention also relates to an image projection method of the optical system, comprising the following steps:

step S81: generating a beam group with light cone distribution;

step S82: the light beam group distributed by the light cone is incident to a first light beam synthesizer positioned on the first surface of the light conduction medium, and the propagation direction of the light beam incident on the first light beam synthesizer is changed by the first light beam synthesizer, so that the light beam enters the light conduction medium at different angles to continue to propagate;

step S83: changing the propagation direction of the light beam propagating in the light conduction medium and incident on the second light beam synthesizer through a second light beam synthesizer positioned on the second surface of the light conduction medium, so that the light beam exits the second light beam synthesizer at different angles to continue to propagate, wherein the light beams of the light beam group which are distributed by the same light cone are converged at one point after exiting the second light beam synthesizer,

Wherein the first surface is non-parallel to the second surface.

According to one aspect of the invention, the optical system has an entrance pupil and an exit pupil, the vertex of the cone of light being the entrance pupil, and the point at which the beams of the beam groups originating from the same cone of light leave the second beam combiner is the exit pupil.

According to one aspect of the invention, the beam generator comprises a laser light source and a microelectromechanical system,

wherein the step S81 includes:

step S811: emitting a light beam carrying color information and/or brightness information of the image pixels by using a laser light source;

step S812: and scanning the light beam emitted from the laser light source by utilizing a micro-electromechanical system to form the light beam group with the light cone distribution.

According to an aspect of the present invention, the step S81 includes:

Illuminating a display screen by utilizing divergent illumination emitted by a light source, wherein the light source is a monochromatic or trichromatic laser light source, an LED light source or an OLED light source, and the display screen is a DMD, LCoS or LCD;

loading an image in the display screen, and modulating light irradiated on the display screen by the light source according to the image;

the modulated light is formed into a beam group of the light cone distribution by a diaphragm or lens.

According to an aspect of the present invention, the step S81 includes:

the method comprises the steps that a light source is used for emitting divergent illumination light to a lens, and the divergent illumination light is converged to the vertex of the light cone after passing through the lens, wherein the light source is a monochromatic or trichromatic laser light source, an LED light source or an OLED light source;

the light beam passing through the lens is irradiated onto a display screen which is a DMD, LCoS or LCD and is positioned between the lens and the vertex, an image is carried in the display screen, and the light irradiated onto the lens is modulated according to the image.

According to one aspect of the invention, the image projection method is implemented using an optical assembly or display system as described above.

The invention also provides a manufacturing method of the optical element, which comprises the following steps:

Step S91: providing a light conduction medium, wherein the light conduction medium is provided with a first surface and a second surface which are non-parallel to each other, the first photosensitive film/first photosensitive plate is positioned on the first surface, and the second photosensitive film/second photosensitive plate is positioned on the second surface;

step S92: emitting laser light by using a laser;

step S93: splitting the laser beam into a first laser beam and a second laser beam;

step S94: splitting the first laser beam into a third laser beam and a fourth laser beam;

step S95: converging the third laser beam to a first point outside the photoconductive medium and incident on the first photosensitive film/first photosensitive plate after exiting from the first point;

step S96: converging the fourth laser beam to a second point outside the photoconductive medium and incident on the first photosensitive film/first photosensitive plate after exiting from the second point;

step S97: the third laser beam converged to the first point and the fourth laser beam converged to the second point generate interference exposure inside the photosensitive material of the first photosensitive film/first photosensitive plate, so as to obtain a first volume holographic optical element.

According to one aspect of the invention, the method further comprises:

step S98: passing the fourth laser beam through the first photosensitive film/first photosensitive plate, entering the inside of the photoconductive medium, and incident on the second photosensitive film/second photosensitive plate;

step S99: allowing the second laser beam to pass through the second photosensitive film/second photosensitive plate and then converging to a third point outside the photoconductive medium;

step S100: and the fourth laser beam passing through the first photosensitive film/the first photosensitive plate and entering the inside of the photoconductive medium and the second laser beam converged to the third point generate interference exposure in the photosensitive material of the second photosensitive film/the second photosensitive plate to obtain a second volume holographic optical element.

According to one aspect of the invention, the direction of the third laser beam is perpendicular to the second surface.

According to an aspect of the present invention, the photosensitive materials of the first photosensitive film/first photosensitive plate and the second photosensitive film/second photosensitive plate are full-color photosensitive materials, and the step S92 includes: a plurality of lasers are utilized to emit laser beams with different wavelengths, and the laser beams are emitted after being combined;

the step S97 includes: simultaneously performing interference exposure inside the photosensitive material of the first photosensitive film/first photosensitive plate corresponding to different wavelengths of the plurality of lasers;

The step S100 includes: interference exposure is simultaneously performed inside the photosensitive material of the second photosensitive film/second photosensitive plate corresponding to different wavelengths of the plurality of lasers.

According to an aspect of the present invention, the photosensitive materials of the first photosensitive film/first photosensitive plate and the second photosensitive film/second photosensitive plate are full-color photosensitive materials, and the step S92 includes: sequentially utilizing a plurality of lasers to emit laser beams with different wavelengths and emitting the laser beams;

the step S97 includes: sequentially performing a plurality of interference exposures inside the photosensitive material of the first photosensitive film/first photosensitive plate corresponding to different wavelengths of the plurality of lasers;

the step S100 includes: a plurality of interference exposures are sequentially performed inside the photosensitive material of the second photosensitive film/second photosensitive plate corresponding to different wavelengths of the plurality of lasers.

According to an aspect of the present invention, the photosensitive materials of the first photosensitive film/first photosensitive plate and the second photosensitive film/second photosensitive plate are monochromatic photosensitive materials, and the step S92 includes: emitting laser beams with wavelengths corresponding to the monochromatic photosensitive materials by using a laser and emitting the laser beams;

the step S97 includes: performing interference exposure inside a photosensitive material of the first photosensitive film/first photosensitive plate corresponding to a wavelength of the laser to obtain a first bulk holographic optical element corresponding to the wavelength;

The step S100 includes: and performing interference exposure inside the photosensitive material of the second photosensitive film/second photosensitive plate corresponding to the wavelength of the laser to obtain a second volume holographic optical element corresponding to the wavelength.

According to one aspect of the invention, the method further comprises: the first photosensitive film/first photosensitive plate and the second photosensitive film/second photosensitive plate, which can be exposed to laser light of different wavelengths, are replaced, and the first volume hologram optical element and the second volume hologram optical element corresponding to the different wavelengths are obtained through the steps S92, S93, S94, S95, S96, S97, S98, S99, and S100.

According to an aspect of the present invention, the step S92 includes:

emitting laser beams with different wavelengths by a plurality of lasers;

combining the laser beams with different wavelengths through an optical film beam splitter; and

and filtering and expanding and collimating the combined laser beams.

According to one aspect of the invention, the method further comprises:

and respectively copying the obtained first volume holographic optical element and second volume holographic optical element serving as a master.

The invention also provides a volume holographic optical element, which is manufactured by the method.

According to one aspect of the invention, the volume hologram optical element is a transmissive volume hologram optical element or a reflective volume hologram optical element.

The present invention also provides an optical assembly comprising:

a beam generator configured to emit a beam group of light cone distribution;

a first beam combiner comprising a first bulk holographic optical element manufactured according to the method described above, located on a first surface of the photoconductive medium; and

a second beam combiner comprising a second volume holographic optical element manufactured according to the method described above, located on a second surface of the light-conducting medium,

wherein the laser beam is a monochromatic or trichromatic laser beam.

According to one aspect of the invention, the beam generator comprises:

According to one aspect of the invention, the first volume holographic optical element and the second volume holographic optical element are one of the following combinations:

the first volume holographic optical element is a transmission volume holographic optical element, and the second volume holographic optical element is a reflection volume holographic optical element; and

the first volume holographic optical element is a transmissive volume holographic optical element, and the second volume holographic optical element is a transmissive volume holographic optical element.

According to one aspect of the invention, the first volume holographic optical element and the second volume holographic optical element are independently any of the following:

A single color volume hologram optical element that diffracts laser light of different wavelengths of the plurality of lasers;

the plurality of monochromatic volume holographic optical elements corresponding to the number of the plurality of lasers are accurately aligned and stacked together, and each monochromatic volume holographic optical element only diffracts laser light with the corresponding wavelength and does not diffract laser light with other wavelengths;

a plurality of volume hologram optical elements having a number less than the plurality of lasers, being accurately aligned and stacked together, at least one of the plurality of volume hologram optical elements diffracting laser light of at least two wavelengths of the plurality of lasers while not diffracting laser light of other wavelengths; the other volume hologram optical elements diffract the laser light of one of the other wavelengths, but do not diffract the laser light of the other wavelengths;

a single monochromatic volume hologram optical element diffracting only laser light of one wavelength.

The invention also provides the use of an optical assembly or display system as described above for near-eye display.

The invention also provides an image projection method implemented by adopting the optical assembly or the display system.

Aiming at the problems of complex optical components and large volume in the traditional retina display technology, the compact optical components and the display system are realized by combining a plurality of beam synthesizers with a light transmission medium, particularly by using an optical waveguide as the light transmission medium, and the compact retina display device has important commercial application value in the near-to-eye AR and VR display fields.

In addition, the two beam combiners which are not arranged in parallel are arranged in a combined mode, the first beam combiners stretch and compensate the shape of the projected image in the reverse direction, an image with an enlarged equal proportion is formed on the second beam combiners, and the image is coupled out along the direction perpendicular to the surface of the second beam combiners to be directly imaged on the retina of human eyes, so that the augmented reality display without keystone distortion is realized, and defects such as trapezoidal distortion of the image and the like caused by the propagation direction of image light and the off-axis arrangement of the beam combiners are avoided.

In addition, the problem that the incidence angle of the light beam is limited when the light beam synthesizer is manufactured under the condition that the two light beam synthesizers are arranged in parallel is avoided by arranging the two light beam synthesizers, so that the assembly size is smaller, the manufacturing process of the light beam synthesizer is simplified and facilitated, and the production cost and practical application and popularization are reduced.

Not all of the features and advantages described in the specification, particularly, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings and specification. Furthermore, it should be noted that the terms used in this specification are primarily selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive concepts.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate and explain the exemplary embodiments of the disclosure and together with the description serve to explain the disclosure, and do not constitute an undue limitation on the disclosure. In the drawings:

FIG. 1 illustrates an optical assembly according to a first aspect of the present disclosure;

FIG. 2 illustrates an optical assembly according to a preferred embodiment of the present disclosure, including a waveguide as a light-conducting medium;

FIG. 3 illustrates a process of distortion-free imaging by backprojection compensation of an optical assembly according to a first aspect of the present disclosure;

FIG. 4 illustrates an optical assembly including a transmissive first beam combiner and a reflective second beam combiner according to a preferred embodiment of the present disclosure;

FIG. 5 illustrates an optical assembly including a transmissive first beam combiner and a transmissive second beam combiner according to a preferred embodiment of the present disclosure;

fig. 6 illustrates a structure of a volume hologram optical element according to a preferred embodiment of the present disclosure;

fig. 7 illustrates an image projection method of an optical system according to a first aspect of the present disclosure;

fig. 8 illustrates a method of manufacturing an optical element according to a second aspect of the present disclosure;

fig. 9 shows a schematic optical path diagram of a beam combiner manufactured by the method shown in fig. 8, wherein the first beam combiner is transmissive and the second beam combiner is reflective.

Detailed Description

Hereinafter, only certain exemplary embodiments are briefly described. As will be recognized by those of skill in the pertinent art, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should be noted that in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In the description of the present disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," etc. indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the present disclosure and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and thus should not be construed as limiting the present disclosure. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more of the described features. In the description of the present disclosure, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

In the description of the present disclosure, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically connected, electrically connected or can be communicated with each other; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the terms in this disclosure will be understood by those of ordinary skill in the art as the case may be. For example, the term "coupled" is used in this disclosure to indicate that the connection between two terminals may be direct, or may be indirect via an intermediate medium, or may be wired or wireless.

In this disclosure, unless expressly stated or limited otherwise, a first feature being "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other by way of additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

The following disclosure provides many different embodiments, or examples, for implementing different structures of the disclosure. In order to simplify the present disclosure, components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present disclosure. Furthermore, the present disclosure may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present disclosure provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize the application of other processes and/or the use of other materials.

It is noted that unless otherwise indicated, technical or scientific terms used in this disclosure should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

Specific embodiments of the present disclosure are described below with reference to the drawings, it being understood that the preferred embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the present disclosure.

First aspect

A first aspect of the present disclosure relates to an imaging distortion free optical assembly (hereinafter sometimes simply referred to as "optical assembly" or "optical module") 10 based on trapezoidal back projection compensation, as shown in fig. 1. The following is a detailed description with reference to fig. 1.

As shown in fig. 1, the optical assembly 10 includes a beam generator 11, a first beam combiner 12, a light conducting medium 13, and a second beam combiner 14. Wherein the beam generator 11 is configured to form a set of light beams of a light cone distribution, wherein the light beams of different directions in the set of light beams may for example carry color information and/or brightness information of different image pixels. Referring to fig. 1, beam generator 11 generates a cone of light having a divergence angle θ, where each beam may individually carry color and/or brightness information for an image pixel. According to one embodiment of the present disclosure, the light beam generator 11 may scan the set of light beams forming the light cone distribution, e.g. at a first instant the light beam generator 11 emits a light beam L1 and at a second instant the light beam generator 11 emits a light beam L2, between the first instant and the second instant the light beam generator 11 emits a light beam between L1 and L2. Alternatively, the beam generator 11 may emit all or part of the beam group in the cone of light at the same time, which is within the scope of the present disclosure.

Those skilled in the art will readily appreciate that the beam generator 11 may form a continuous distribution of light beams in the light cone, or may form discrete light rays to form groups of light beams, e.g. individual light beams are not spread over any angle of the light cone, but are discrete. According to a preferred embodiment of the present disclosure, the optical assembly 10 has an entrance pupil 10-In and an exit pupil 10-Out, the apex of which may be located at the position of the entrance pupil 10-In. In fig. 1, the divergence angle of the light cone is θ. The beam generator 11 may itself have a divergence angle θ such that the divergence angle of the beam of light emitted therefrom itself corresponds to the divergence angle θ of the cone of light. Or alternatively the beam generator 11 comprises a laser emitting a laser beam which is a highly directional beamlet, in which case the beam generator 11 may for example comprise scanning means for scanning the highly directional beamlet emitted by the laser to form a cone of light having a divergence angle θ, as will be described in more detail below. Or alternatively, the beam generator 11 emits a converging beam, the converging point being the position of the entrance pupil 10-In, i.e. at the vertex of the cone of light, and the light passing through the converging point can then be regarded as a diverging beam from the converging point. These are all within the scope of the present disclosure. In addition, the light beam emitted from the light beam generator 11 may be a single-color light beam or a multi-color light beam formed by mixing a plurality of single-color lights. In addition to carrying color information, the light beam emitted by the light beam generator 11 may also carry luminance information. Beamlets in the present disclosure or beamlets of high directivity, for example, refer to beams having a beam diameter of less than 2 millimeters or less than 1 millimeter (preferably less than 0.01 millimeter), and a divergence angle of 0.02 to 0.03 degrees or less.

In addition, it is well understood by those skilled in the art that the light beams may be emitted simultaneously or at different times (e.g., by scanning) in the light beam group of the light cone distribution formed by the light beam generator 11, which is within the scope of the present disclosure.

Those skilled in the art will readily appreciate that the light-conducting medium may be a solid form medium such as transparent glass or air. When the light transmission medium is air, the fixing of the first beam combiner 12 and the second beam combiner 14 is implemented by an external fixing structure, so that the accuracy of the relative positions is ensured. In the following description, the description of the present disclosure will be made taking an example in which the light-transmitting medium 13 is a solid-state material, and the description will not be repeated regarding the case in which air is used as the light-transmitting medium. These are all within the scope of the present disclosure.

The photoconductive medium 13 is a material in which light connected to the first beam combiner 12 and the second beam combiner 14 respectively can propagate, and a part of the surface thereof is free space (e.g., air) outside. In the photoconductive medium 13, the light beam propagates from the first beam combiner 12 to the second beam combiner 14 and is modulated to leave the photoconductive medium and enter free space (e.g., air). The refractive index of the light-conducting medium 13 is greater than that of air.

The first beam combiner 12 is attached to one surface S11 (first surface) of the photoconductive medium 13, receives the light beam group of the light cone distribution formed by the light beam generator 11, and changes the propagation direction of the light beam so as to propagate in the photoconductive medium 13 at different angles. The second beam combiner 14 is attached to the other surface S12 (second surface) of the photoconductive medium 13 at an inclination angle to the surface S11, receives the light beam redirected by the first beam combiner 12 and propagating in the photoconductive medium 13, and again changes the propagation direction of the light beam so that it enters the free space (e.g. air) at a different angle for continued propagation, wherein the light beams of the light beam group originating from the same light cone distribution are eventually converged in a point in the free space (e.g. air), which may be, for example, the exit pupil 10-Out of the optical assembly 10. The beam generator 11 forms the set of light beams of the light cone distribution in a direction perpendicular to the second beam combiner 14, whereby the main propagation direction of the image light is non-parallel with the vertical axis of the first beam combiner 12 and parallel with the vertical axis of the second beam combiner 14. As shown in fig. 1, any one of the light beams of the light beam group of the light cone distribution defined by the light beams L1 and L2 is first incident on the first light beam combiner 12 disposed obliquely, propagates in the light guiding medium 13 at different angles after being modulated by the first light beam combiner 12, is incident on the second light beam combiner 14, changes angle again after being modulated by the second light beam combiner 14, enters the free space (e.g. air) via the light guiding medium 13, continues to propagate, and finally converges at a point, i.e. the exit pupil 10-Out.

In this disclosure, the expression "main propagation direction" or "main direction" is understood as the direction of the central ray. For example, in the embodiment shown in fig. 1, the main direction of the light cone defined by the light beams L1 and L2 is a vertically upward direction with respect to the second beam combiner 14.

According to the present disclosure, the first beam combiner 12 and the second beam combiner 14 are arranged at an oblique angle therebetween. According to one embodiment of the present disclosure, the inclination angle between the surface S11 of the photoconductive medium 13 to which the first beam combiner 12 is attached and the surface S12 to which the second beam combiner 14 is attached is in the range of 20 ° to 80 ° (based on the acute angle formed therebetween), preferably 45 °. Furthermore, according to a preferred embodiment of the present disclosure, the first beam combiner 12 and the second beam combiner 14 do not overlap each other in a direction perpendicular to the main propagation direction of the image light.

According to the present disclosure, the refractive index of the first beam combiner 12 and the refractive index of the second beam combiner 14 are both greater than the refractive index of air. In the present disclosure, the refractive indices of the first beam combiner 12, the photoconductive medium 13, and the second beam combiner 14 are not particularly limited as long as they are all larger than the refractive index of air, and the above-described beam propagation paths can be realized. According to a preferred embodiment of the present disclosure, the refractive index of the first beam combiner 12 and the second beam combiner 14 are each the same as or close to the refractive index of the photoconductive medium 13. According to a preferred embodiment of the present disclosure, the first beam combiner 12 and the second beam combiner 14 are made of the same material, which may have the same refractive index; or from different materials, which may differ in refractive index. The beam synthesizer can be a photosensitive film, or can be manufactured by coating photosensitive materials on transparent light-transmitting media such as glass and the like and exposing the photosensitive materials in a certain mode.

According to a preferred embodiment of the present disclosure, the first beam combiner 12 comprises, for example, a diffractive optical element. The diffractive optical element is attached to one surface of the photoconductive medium 13, and the light beams in the light beam group distributed by the light beam generator 11 are diffracted when propagating to different positions of the diffractive optical element in different directions, the propagation direction is changed and enter the photoconductive medium, and the light beams (corresponding to the same light cone) which enter the photoconductive medium and are diffracted in different directions from different positions of the diffractive optical element are all incident to different positions of the second light beam synthesizer 14.

According to a preferred embodiment of the present disclosure, the second beam combiner 14 comprises, for example, a diffractive optical element. The diffractive optical element is attached to the other surface of the light-conducting medium 13, and when the light beams which are modulated by the first beam combiner 12 and propagate in the light-conducting medium at different angles and propagate to different positions of the diffractive optical element in different directions, diffraction occurs, the propagation direction changes and enters the free space, and the beamlets (corresponding to the same light cone) which enter the free space and are diffracted in different directions from different positions of the diffractive optical element are converged at the same point in the free space.

The diffractive optical element may be a volume holographic optical element capable of diffracting light of a specific wavelength and a specific direction without diffracting light of other wavelengths and directions, with angle and wavelength selectivity. In the following description, unless specifically stated otherwise, the diffractive optical element refers to a transmissive volume hologram optical element and/or a reflective volume hologram optical element. That is, the diffractive optical element is, for example, a volume hologram optical element, and may be a transmissive volume hologram optical element or a reflective volume hologram optical element. In the present disclosure, the first beam combiner 12 includes a transmissive volume hologram optical element, and the second beam combiner 14 includes a transmissive volume hologram optical element and a reflective volume hologram optical element, depending on the configuration of the actual components. As will be described in detail later.

The operation of the optical assembly 10 shown in fig. 1 is described in detail below. In fig. 1, the beam generator 11 forms a beam group of light cone distribution, for example, two light beams L1 and L2 located at the boundary of the beam group, which are respectively incident on the first beam combiner 12 (the incident points are, for example, at the point a and the point B). The first beam combiner 12 is a transmissive volume hologram optical element, which can enable the light beam incident thereon to be diffracted regardless of the incident direction or angle, and the diffracted light beam enters the light transmission medium 13 to continue to propagate, and is incident on the second beam combiner 14 (the incident points are, for example, point C and point D). The second beam combiner 14 is, for example, a reflective volume hologram optical element, which enables the light beam incident thereon to be diffracted regardless of the incident direction or angle, and the diffracted light beam passes through the photoconductive medium 13 and then converges at a point in free space, for example, an exit pupil 10-Out of the optical component 10 as shown in fig. 1.

Shown in fig. 1 is a combination of a transmissive first beam combiner 12 and a reflective second beam combiner 14, wherein the incident beam from the cone of light distribution beam group and the beam exiting after passing through the first beam combiner 12 are located on either side of the first beam combiner 12, the first beam combiner 12 performing a similar transmissive beam modulation; while the incident light beam from the photoconductive medium is on the same side of the second beam combiner 14 as the light beam exiting after passing through the second beam combiner 14, the second beam combiner 14 performs a reflection-like beam modulation. Those skilled in the art will readily appreciate that the optical assembly 10 according to the present disclosure may also be implemented with, for example, a combination of a transmissive first beam combiner 12 and a transmissive second beam combiner 14, the optical principles of which are similar.

Note that the "convergence at a point", "entrance pupil" and "exit pupil" of the optical assembly 10 in this disclosure may be either a point in space or a region in space. The essential reason that this region can be formed is that the volume hologram optical element has a certain angle selectivity and wavelength selectivity, that is, a wavelength and a propagation angle in the vicinity of the designed wavelength and propagation angle can also be diffracted in accordance with a diffraction relationship; when the wavelength and the propagation angle are far from the designed wavelength and propagation angle, the diffraction efficiency is rapidly reduced, and diffraction is considered not to occur when the diffraction efficiency is reduced to a certain extent. In case a certain diffraction efficiency is met, the corresponding entrance pupil is no longer a point but a certain area, so that the corresponding exit pupil is no longer a point but a certain area.

In the embodiment shown in fig. 1, the light beams in the light beam group of the light cone distribution formed by the light beam generator 11, which are modulated by the first light beam combiner 12, change the propagation direction of the light beams and enter the light guiding medium 13, and then propagate in the light guiding medium 13 and are directly incident to the second light beam combiner 14. In this case, the light-transmitting medium 13 may be made of a transparent material such as glass or resin, for example. However, the light-transmitting medium in the present disclosure is not limited to light-transmitting materials such as glass, resin, etc., but the same beam propagation path may be realized using a waveguide such as other transparent medium. Particularly, when the waveguide is used as the light-conducting medium, the refractive index of the light-conducting medium is larger than that of air, so that the light beam entering the waveguide can be totally reflected at the interface of the waveguide and the air under the condition of meeting the incident angle, and then is incident on the second light beam combiner after one or more times of total reflection. One advantage of this implementation is that it allows for a larger space for the structural design, thereby facilitating an optimized structure of the optical module. Namely: the angle of incidence of the light incident on the second beam combiner 14 can satisfy the technical objective of the present invention in both cases where total reflection occurs or not at the interface of the second beam combiner 14 and air.

According to a preferred embodiment of the present disclosure, as shown in fig. 2, the optical assembly 20 comprises a beam generator 21, a first beam combiner 22, a waveguide 23 as a light conducting medium, and a second beam combiner 24. Referring to fig. 2, the light beam generator 21 generates a light cone bordered by light beams L1 and L2, the light beams in the light cone first enter the first light beam combiner 22 disposed obliquely, enter the waveguide 23 at different angles after being modulated by the first light beam combiner 22, and are totally reflected at an interface S21 between the waveguide 23 and a free space (e.g., air), and the totally reflected light is incident on the second light beam combiner 24. Since the refractive index of the second beam combiner 24 is the same as or close to that of the waveguide 23, when the light enters the second beam combiner 24, the light enters the second beam combiner 24 without total reflection. The beam is modulated by the second beam combiner 24, again changing angle, enters free space (e.g. air) for continued propagation, and finally converges at a point, the exit pupil 20-Out.

In fig. 2, S22 drawn in a broken line is an upper surface of the photoconductive medium in the case where total reflection of the light beam does not occur (for example, the case corresponding to fig. 1), and S21 drawn in a solid line is an upper surface of the photoconductive medium in the case where total reflection of the light beam occurs once. As can be seen by comparison, the embodiment shown in fig. 2 enables a further reduction in the thickness of the light-conducting medium by using a waveguide as the light-conducting medium and exploiting the total reflection of light.

In addition, the embodiment shown in fig. 2 also describes an implementation of constructing the optical assembly 20 of the present disclosure with a combination of a transmissive first beam combiner 22 and a transmissive second beam combiner 24.

One advantage of the optical assembly of the present disclosure is that the optical assembly includes a beam generator, a first beam combiner, a light conducting medium, and a second beam combiner, which can effectively reduce the thickness of an associated module. Especially in the case of use in VR or AR spectacles, for example, the thickness of the whole module can be of the order of centimetres, even of the order of millimetres. Furthermore, by using a waveguide as a light-conducting medium, it is possible to further reduce the thickness of the module.

Another advantage of the optical assembly of the present disclosure is that by providing two non-parallel beam combiners, defects such as image keystone distortion caused by oblique incidence of the propagation direction of image light with respect to the beam combiners can be avoided, as described in detail below.

In the optical assembly of the present disclosure based on trapezoidal back projection compensation without imaging distortion, a first beam combiner and a second beam combiner are provided, which are arranged at an oblique angle to each other, wherein the light emitted by the beam generator is obliquely incident on the first beam combiner, and the main direction of the light emitted by the light source is perpendicular to the second beam combiner. In this case, assuming that the shape of the original image is rectangular (i.e., the light beam emitted from the light beam generator has a rectangular outline in a plane perpendicular to its main direction), since the first light beam combiner is arranged obliquely with respect to the main direction, the projected image of the original image formed on the first light beam combiner is partially stretched and deformed from the rectangular shape to a trapezoid-like shape. At this time, the first beam combiner performs inverse stretching and shape compensation on the projection image in the process of diffraction, so that an image which is restored to a rectangle and expanded in equal proportion is formed on the second beam combiner, and the image is coupled and imaged on the retina of human eyes along the direction vertical to the surface of the second beam combiner, thereby realizing the augmented reality display without keystone distortion, and avoiding the defects such as image keystone distortion and the like caused by the propagation direction of image light and the off-axis arrangement of the beam combiner. Thus, the optical assembly of the present disclosure can avoid the keystone problem described above.

In order to more clearly describe the case where the technical solution of the present disclosure is free of keystone distortion, the imaging process in fig. 1 will be illustrated in the form of a two-dimensional top view. Referring to fig. 3 in combination with fig. 1, 41 shows the outline of an original image, i.e. the outline of a cone beam as seen against its main direction, having, for example, a rectangular shape, with its left and right edges marked 411 and 412, respectively. 42 denotes a projection area of the original image 41 formed by scanning on the first beam combiner 12, the left and right edges of which are denoted 421 and 422, respectively, wherein the left edge 421 corresponds to the position of the incident point a in fig. 1 and the right edge 422 corresponds to the position of the incident point B in fig. 1. Since the first beam combiner 12 is arranged obliquely with respect to the original image 41, the projection area 42 of the original image 41 formed on the first beam combiner 12 is gradually stretched (stretched in the up-down direction in the drawing) from its left edge 421 to its right edge 422, so that the projection area 42 is deformed from an initial moment into a trapezoid-like shape. The first beam combiner 12 performs inverse stretching and shape compensation on the projection area 42 during diffraction, and forms a projection area 43 which is reduced to a rectangle and expanded in equal proportion on the second beam combiner 14, and the left edge and the right edge thereof are respectively marked with 431 and 432, wherein the left edge 431 corresponds to the position of the incident point C in fig. 1, and the right edge 432 corresponds to the position of the incident point D in fig. 1. As can be seen from fig. 3, the size of the projection area 43 formed via the optical path procedure described above is scaled up equally with respect to the original image 41, which original image 41 is eventually transferred equally onto the second beam combiner 14, which is still rectangular, rather than having a stretched distorted image, so as to be able to illustrate the advantages of the present disclosure over other solutions.

In one embodiment of the invention, to achieve an imaging process without image distortion as described above, the optical assembly should satisfy the following conditions: any of the beams in the same cone of light distribution, which emanate from the beam generator and reach the optical path of the second beam combiner via the first beam combiner and the photoconductive medium, are always equal. In this way, the contour or shape of the illuminated area can be maintained in equal proportion, for example when the beam of light emitted by the beam generator has a square cross section, the illuminated area produced on the second beam combiner is likewise square; when the beam has a circular cross-section, the illuminated area produced on the second beam combiner is also circular, thus achieving an equal magnification of the image. Taking fig. 1 as an example, assuming that the vertex of the light cone is M, the following quantitative relationship should be satisfied:

MB×n ₁ +BD×n ₂ ＝MA×n ₁ +AC×n ₂

wherein n is ₁ Refractive index of air, n ₂ Is the refractive index of the photoconductive medium.

In the above optical assembly without imaging distortion based on trapezoidal reverse projection compensation according to the present disclosure, the image light forms a reverse projection after passing through the first beam combiner, for compensating the projection distortion of the light emitted from the first beam combiner on the second beam combiner, so that the imaging without trapezoidal distortion can be realized.

Fig. 4A illustrates an optical assembly 50 according to a preferred embodiment of the present disclosure. Described in detail below with reference to fig. 4A.

The optical assembly 50 shown in fig. 4A also includes a first beam combiner 512, a light conducting medium 513, and a second beam combiner 514, similar to that shown in fig. 1, and will not be described again here. As shown in fig. 4A, beam generator 511 comprises an image source 516 and a microelectromechanical system 517, wherein image source 516 is configured to generate a beam L0 carrying color information and/or brightness information of image pixels, beam L0 being incident on microelectromechanical system 517, and microelectromechanical system 517 is configured to scan beam L0 to form a set of beams of the light cone distribution. In accordance with a preferred embodiment of the present disclosure, microelectromechanical system 517 includes, for example, a MEMS galvanometer that receives incident light beam L0 and scans light beam L0 to form a beam set of the light cone distribution.

In fig. 4A, the light beam L0 exiting the image source 516 is always in the same spatial path, but the exiting light beam forms a beam set of light cone distributions (e.g., light cones defined by L1 and L2 in fig. 4A) due to the rotation of the MEMS 517 (e.g., MEMS galvanometer therein) and the scanning of the light beam L0 incident thereon. The micro-electromechanical system 517 includes a MEMS galvanometer by which an image generated by the image source 516 is formed by scanning beamlets carrying color information and/or brightness information of image pixels from lasers of different wavelengths.

According to a preferred embodiment of the present disclosure, the light beam generator is a beamlet generator whose image source comprises a plurality of lasers, a controller coupled to the plurality of lasers and controlling the plurality of lasers to emit laser beams, for example controlling the emission time, intensity and other optical parameters of the lasers. The laser beams of the plurality of lasers are incident on the beam combiner and are combined into nearly parallel beamlets with spatially coincident propagation paths. The following describes in detail with reference to fig. 4A.

As shown in fig. 4A, the image source 516 includes a laser, for example, fig. 4A shows a first laser 501, a second laser 502, and a third laser 503, where the first laser 501 is, for example, a red laser, the second laser 502 is, for example, a green laser, and the third laser 503 is, for example, a blue laser, each emitting a laser beam of a corresponding wavelength. Optionally, the image source 516 further includes a first lens (or lens group) 504, a second lens (or lens group) 505, and a third lens (or lens group) 506, for collimating, reducing the divergence angle, or compressing the laser beams emitted by the first laser 501, the second laser 502, and the third laser 503, respectively, on the light path, so as to form high-directivity beamlets. The beam combiner comprises optical thin film light splitters corresponding to the wavelengths of laser light emitted by the lasers, and the optical thin film light splitters are arranged at the downstream of lenses (or lens groups) corresponding to the lasers, wherein the laser light of the lasers enters the corresponding optical thin film light splitters after passing through the lens groups, and the near-parallel beamlets with coincident propagation paths in space are formed through reflection or transmission. Alternatively, the beam combiner of the image source 516 includes a first beam splitter 507, a second beam splitter 508, and a third beam splitter 509 for combining red, green, and blue laser beams, respectively, corresponding to the red, green, and blue lasers. The first dichroic sheet 507 will be described in detail below as an example. The first light splitting sheet 507 is disposed downstream of the optical path of the first lens 504, and is, for example, an optical thin film split sheet corresponding to the wavelength of the laser light emitted from the first laser 501, so that the red light emitted from the first laser 501 is reflected and the light having a wavelength other than the red light is transmitted. Similarly, the second beam splitter 508 causes the green light emitted by the second laser 502 to be reflected and light of wavelengths other than green light to be transmitted; the third dichroic sheet 509 reflects blue light emitted from the third laser 503 and transmits light having a wavelength other than blue light. The red laser light is reflected by the first light-splitting sheet 507, is incident on the second light-splitting sheet 508 and transmitted through the second light-splitting sheet 508, and then transmitted through the third light-splitting sheet 509. The green laser light is reflected by the second light-splitting sheet 508, is incident on the third light-splitting sheet 509, and is transmitted through the third light-splitting sheet 509. The blue laser light is reflected by the third light-splitting sheet 509. The reflection paths of the first beam splitter 507, the second beam splitter 508, and the third beam splitter 509 are set to be identical as shown in fig. 4A, and thus, the light beams reflected from the three beam splitters eventually synthesize a light beam L0. Wherein the lens group can comprise a liquid lens or a liquid crystal lens, and the equivalent focal length of the lens group can be adjusted through external voltage control, so as to control the divergence angle and/or the diameter of the laser beam emitted by the laser. The controller may for example control the corresponding lasers. For example, if only red and green wavelength components are present in the currently projected pixel, then the first laser 501 and the second laser 502 are controlled by the controller to emit laser beams of corresponding wavelengths; and the third laser 503 is controlled by the controller not to emit a laser beam.

In addition, the beam splitter may be a broadband beam splitter, that is, a beam splitter that allows reflection of light in a certain wavelength range and transmits light in other wavelength ranges.

The light beam L0 is incident on a MEMS galvanometer 517 (such as an optical scanning galvanometer). The mirrors In the galvanometer deflect back and forth In a certain angle range under the action of electromagnetic force, so that an incident light beam L0 is scanned and emitted to form a light cone-shaped light beam group, for example, a light cone defined by reflected light beams L1 and L2 at different moments, wherein the vertex of the light cone, for example, the swinging center of the galvanometer, is positioned at the position of the entrance pupil 50-In of the optical component 50. Additionally, in accordance with a preferred embodiment of the present disclosure, vibrating mirror 517 is disposed with first beam combiner 512 and second beam combiner 514 such that: the beams (e.g., beams L1 and L2) generated by the galvanometer at the scanning limit position can be incident on the first beam combiner 512 and transmitted through the light transmission medium 513 and then incident on the second beam combiner 514, which will not be described herein.

In addition, according to a preferred embodiment of the present disclosure, image source 516 may also include one or more of a stop, a wave plate, a polarizer, an attenuator (not shown) disposed between lenses (or lens groups) 504, 505, 506 and optical film splitters 507, 508, 509. Image source 516 may also include a micro-motor (not shown) coupled to the lens (or lens group) that can adjust the position of the lens (or lens group) or adjust the relative position between lenses in the lens group to adjust optical parameters such as the spot size and/or divergence angle of the beam exiting the lens group.

As will be readily understood by those skilled in the art, the wavelengths and intensities of the laser beams emitted by the first laser 501, the second laser 502, and the third laser 503, for example, three wavelength components of RGB corresponding to one pixel of a picture or a pattern, respectively transmit laser beams of the respective wavelengths, and then perform beam combination.

Those skilled in the art will readily appreciate that image source 516 is schematically illustrated in fig. 4A as including three lasers of red, green, and blue, although the scope of the present disclosure is not limited in this respect. For example, image source 516 may include a greater or lesser number of lasers, and the wavelength of the lasers may be arbitrarily selected as desired. For example, image source 516 may comprise only one laser emitting a single color laser, which is within the scope of the present disclosure.

In addition, the scope of the present disclosure is not limited to the type of optical field emitted by the laser. The laser may emit either plane waves or spherical waves, which are collimated and compressed by a lens or lens group, as will be readily appreciated by those skilled in the art.

In the embodiment of fig. 4A, beam generator 511 further comprises a mirror 510. In this case, the light beam L0 is first incident on the mirror 510 and then reflected by the mirror 510 to the mems 517. Such an arrangement is advantageous for further reducing the thickness of the entire optical module.

Fig. 4B illustrates an optical assembly 50 according to another embodiment of the present disclosure, including a first beam combiner, a light conducting medium, and a second beam combiner, as described in fig. 1 and 4A, and not described again here. In fig. 4B, the optical assembly 50 based on trapezoidal back projection compensation without imaging distortion further includes a light beam generator 511, and the light beam generator 511 includes, for example, a light source 5111, a lens 5112, and a display 5113, which are sequentially arranged. The light source 5111 is, for example, a monochromatic laser light source, or a polychromatic laser light source (e.g., red, green, and blue lasers), or may be an LED light source or an OLED light source, for providing illumination or backlight to the display 5113. When a laser light source is used, for example, a light source coupled into an optical fiber, the illumination light is emitted from the optical fiber, the light emitted from the light source 5111 is incident on the lens 5112, modulated by the lens 5112, and converged at the position of the entrance pupil 50-In, thereby forming the light cone beam group. The display screen 5113 may be, for example, one or more of a DMD, LCoS, and LCD, disposed between the lens 5112 and the entrance pupil 50-In. The display 5113 itself may be loaded with an image and modulate light impinging upon it from the lens 5112 based on information of the color and/or brightness of the loaded image. Thus, the set of light beams exiting through the display 5113 not only converge at the entrance pupil 50-In, but also carry color information and/or brightness information for the different image pixels.

Or alternatively, as shown In fig. 4C, a display 5113 (such as one or more of DMD, LCoS, LCD) may be disposed between the light source 5111 and the lens 5112, where the light emitted by the light source 5111 directly irradiates the display 5113, and the display 5113 modulates the light beam irradiated thereon according to the color and/or brightness information of the loaded image, and the modulated light beam passes through the lens 5112 and is converged at the position of the entrance pupil 50-In, thereby forming the light beam group with the light cone distribution. And will not be described in detail herein.

Alternatively, it is also conceivable for a person skilled in the art to illuminate the display with a surface light source or with a point light source identical to that of fig. 4C and to place a scattering film behind the point light source, and to illuminate the display by means of the scattering light, so that the light emitted from the display has various directions, and to place a small aperture stop at the entrance pupil position of the assembly, and to form a light beam group of a light cone from the light emitted from the display after passing the aperture stop, in which case the same effect can be achieved without the lens 5112.

Fig. 4A illustrates an optical assembly 50 according to a preferred embodiment of the present disclosure that employs a combination of a transmissive first beam combiner 512 and a reflective second beam combiner 514. Fig. 5 then shows an optical assembly 60 according to another preferred embodiment of the present disclosure employing a combination of a transmissive first beam combiner 612 and a transmissive second beam combiner 614. The first beam combiner 612 basically operates in the same manner as the first beam combiner 12 shown in fig. 1, and will not be described herein. Unlike fig. 1, the second beam combiner 614 in fig. 5 performs beam modulation similar to transmission, and the beam propagating in the photoconductive medium 613 at different angles after being modulated by the first beam combiner 612 is incident on the second beam combiner 614, changes angle again after being modulated by the second beam combiner 614 and is transmitted, enters free space (e.g., air), continues to propagate, and finally converges at a point, i.e., exit pupil 60-Out.

According to a preferred embodiment of the present disclosure, the volume hologram optical element is a single color volume hologram optical element, for example, a single color volume hologram optical film, which is obtained, for example, by exposing the laser light of the wavelength corresponding to the plurality of lasers, so that the laser light beams of the corresponding wavelengths emitted by the plurality of lasers can be diffracted and modulated accordingly. For example, when a single Zhang Caise volume holographic optical film sensitive to red, green, and blue lasers is used in the optical assembly of the embodiment of fig. 4A, the color volume holographic optical film diffractively modulates the incident beam, focusing at a point outside the photoconductive medium, whether the incident beam is red, green, blue, or a combination of the various. The single color volume hologram optical film may be obtained by simultaneously exposing the laser beams of the plurality of lasers, or may be obtained by exposing the single color volume hologram optical film to laser beams of one wavelength at a time and sequentially exposing the single color volume hologram optical film a plurality of times. The method has the advantages that a plurality of volume holographic optical films do not need to be aligned and stacked together, and the arrangement method is simple.

Or alternatively, the volume hologram optical element includes a plurality of single-color volume hologram optical elements accurately aligned and stacked together, corresponding to the number of the plurality of lasers, the plurality of single-color volume hologram optical elements being respectively obtained by exposing to laser light of a wavelength corresponding to one of the plurality of lasers. For example, when three single-color volume hologram optical films sensitive to red, green and blue lasers are used for the optical assembly of the embodiment of fig. 4A, the single-color volume hologram optical film sensitive to red laser diffracts only red laser light and does not diffract laser light of other wavelengths, so that after the red laser beams incident thereon at different angles are subjected to diffraction modulation by the film, the red laser beams continue to propagate at different angles (enter a light-conducting medium under the diffraction action of a first beam combiner and continue to propagate under the diffraction action of a second beam combiner). The monochromatic volume holographic optical film sensitive to green laser and the monochromatic volume holographic optical film sensitive to blue laser are similar to the diffraction condition of the monochromatic volume holographic optical film sensitive to red laser on light waves with corresponding wavelengths. Those skilled in the art will readily appreciate that if more wavelength lasers are included in the light source, the beam combiner may also include a corresponding volume holographic optical film. These are all within the scope of the present disclosure. The advantage of this approach is that each volume holographic optical element is only exposed a single time, with high diffraction efficiency. The laser used for exposure is, for example, a single longitudinal mode laser, and has strong coherence. The laser used as the display light source may be a multimode laser of low coherence, or a LED or OLED light source of corresponding wavelength. When in use, the first beam synthesizer and/or the second beam synthesizer of the three monochromatic volume holographic optical films sensitive to red, green and blue lasers are directly attached to the corresponding surfaces of the photoconductive medium, so that the diffraction modulation effect on the light beams with various wavelengths incident on the first beam synthesizer and the second beam synthesizer can be realized.

Fig. 6 shows such an example. The first beam combiner 72 includes three single-color volume hologram optical films, namely, a first volume hologram optical film 721 (sensitive to red), a second volume hologram optical film 722 (sensitive to green), and a third volume hologram optical film 723 (sensitive to blue), which diffract and modulate light beams of different wavelengths, respectively. The second beam combiner 74 includes three single-color volume hologram optical films, namely, a fourth volume hologram optical film 741 (sensitive to red), a fifth volume hologram optical film 742 (sensitive to green), and a sixth volume hologram optical film 743 (sensitive to blue), which diffract and modulate light beams of different wavelengths, respectively. Taking the first volume hologram optical film 721 and the fourth volume hologram optical film 741 of the red component as an example, only red laser light is diffracted and other wavelength laser light is not diffracted, so that the red laser beams incident on the first volume hologram optical film 721 at different angles enter the photoconductive medium 73 for continuous propagation after being modulated by diffraction, and enter the free space for continuous propagation at different angles after being modulated by diffraction of the fourth volume hologram optical film 741, wherein the beams in different directions propagating in the free space are all converged at the exit pupil position. Similarly, the second volume hologram optical film 722 and the fifth volume hologram optical film 742 of the green component diffract only the green laser light and do not diffract the other wavelength laser light, so that the green laser light beams incident thereon at different angles enter the photoconductive medium 73 at different angles to continue to propagate after being modulated by the diffraction of the second volume hologram optical film 722, and enter the free space at different angles to continue to propagate after being modulated by the diffraction of the fifth volume hologram optical film 742, wherein the light beams in different directions propagating in the free space are all converged at the exit pupil position. Also similarly, the third and sixth volume hologram optical films 723 and 743 of the blue component diffract only blue laser light and do not diffract laser light of other wavelengths, so that blue laser light beams incident thereon at different angles enter the photoconductive medium 73 at different angles to continue to propagate after being modulated by diffraction of the third volume hologram optical film 723, and continue to propagate in free space at different angles after being modulated by diffraction of the sixth volume hologram optical film 743, wherein light beams in different directions propagating in free space are all converged at the exit pupil position.

Or alternatively, the volume hologram optical element includes a plurality of volume hologram optical elements accurately aligned and stacked together, the number of the plurality of volume hologram optical elements being smaller than the number of the plurality of lasers, at least one of the plurality of volume hologram optical elements being obtained by laser exposure of at least two of the plurality of lasers, and the remaining volume hologram optical elements being obtained by laser exposure of the remaining one of the plurality of lasers. For example, in the above-described embodiment using three single-color volume hologram optical films sensitive to red, green and blue laser light, one volume hologram optical film sensitive to red and green simultaneously is used instead of the single-color volume hologram optical film sensitive to red laser light and the single-color volume hologram optical film sensitive to green laser light. The volume hologram optical film sensitive to red and green simultaneously is obtained by, for example, exposing with red and green lasers simultaneously or sequentially. Alternatively, a single piece of volume hologram optical film sensitive to both green and blue may be used instead of the single-color volume hologram optical film sensitive to green laser light and the single-color volume hologram optical film sensitive to blue laser light; alternatively, a single piece of volume hologram optical film sensitive to both red and blue may be used instead of the single-color volume hologram optical film sensitive to red laser light and the single-color volume hologram optical film sensitive to blue laser light. These are all within the scope of the present disclosure. This arrangement improves diffraction efficiency while reducing the number of stacks, relative to the arrangement of the embodiments described above in which all of the monochromatic volume hologram optical elements are used.

Alternatively, the volume hologram optical element includes a single-color volume hologram optical element, a laser beam corresponding to one wavelength, and a laser.

According to one embodiment of the present disclosure, the volume hologram optical element is obtained by exposing a film of a photosensitive material or a photosensitive plate of a photosensitive material, including one or more of a silver salt material, a photopolymer material, a gelatin material, which can sense one or more of red light, green light, or blue light, to a glass substrate or a resin substrate in a certain manner. As will be described in detail below.

The configuration and morphology of the diffractive optical elements included in the first beam combiner and the second beam combiner may be independently selected from the different manners described in the above embodiments (for example, a single color volume hologram optical element, or a plurality of monochrome volume hologram optical elements corresponding to the number of lasers, or a plurality of volume hologram optical elements less than the number of lasers, or a single monochrome volume hologram optical element), and may be the same or different. These are all within the scope of the present disclosure.

The above-described solutions of using a transmissive volume hologram optical element for the first beam combiner and using a reflective or transmissive volume hologram optical element for the second beam combiner are shown in fig. 4 to 6, respectively. Those skilled in the art will readily appreciate that the features of any of these embodiments may be incorporated into another embodiment without the need for inventive effort.

The first aspect of the present disclosure also relates to a display system comprising an imaging distortion free optical assembly based on trapezoidal back projection compensation as described above. The display system is, for example, a virtual reality display system or an augmented reality display system.

According to one embodiment of the disclosure, the display system further comprises an image generating unit configured to generate an image to be displayed, the image generating unit being coupled to the beam generator, the beams of different directions in the beam group emitted by the beam generator carrying color information and/or brightness information of different pixels in the image.

The image generation unit is for example used for generating images that need to be presented to a user. The beam generator scans the image, for example, pixel by pixel, generating a corresponding laser beam from the red, green and blue components of each pixel, carrying color information and/or brightness information for different pixels in the image. The display system projects a beam of light for the pixel into the user's eye (e.g., on the retina) through the optical assembly to image in the user's eye. Preferably, the display system includes two sets of the optical components for displaying the same two-dimensional image for the left eye and the right eye of the user for two-dimensional display or two-dimensional image with parallax to realize three-dimensional display based on binocular parallax. Since the method of the present disclosure is retinal imaging, for a three-dimensional display of binocular parallax, the depth of field of the image is large, and there is no convergence adjustment conflict problem.

The first aspect of the present disclosure also relates to an image projection method 80 of an optical system. As shown in fig. 7, the method 80 includes the steps of:

s81: generating a beam group with light cone distribution;

s82: the light beam group distributed by the light cone is incident to a first light beam synthesizer positioned on the first surface of the light conduction medium, and the propagation direction of the light beam incident on the first light beam synthesizer is changed through the first light beam synthesizer, so that the light beam enters the light conduction medium at different angles to continue to propagate;

s83: and changing the propagation direction of the light beam propagating in the light conduction medium and incident on the second light beam synthesizer through a second light beam synthesizer positioned on the second surface of the light conduction medium, so that the light beam exits the second light beam synthesizer at different angles to continue to propagate, wherein the light beams of the light beam group which are distributed by the same light cone are converged at one point after exiting the second light beam synthesizer, and the first surface and the second surface are non-parallel.

The method 80 may be implemented, for example, by the above-described keystone-based backprojection-compensated imaging-distortion-free optical assembly 10, 20, 50, 60, or by a display system having the above-described keystone-based backprojection-compensated imaging-distortion-free optical assembly. The above description can thus be combined or adapted for use in the image projection method 80 without the need for inventive labor. For example, the profile of the irradiation area of the beam group of the light cone distribution on any cross section perpendicular to the main direction of the beam group is equal to the profile of the irradiation area formed on the second beam combiner, and the main direction of the beam group is perpendicular to the plane of the second beam combiner.

The optical system is provided with an entrance pupil and an exit pupil, wherein the vertex of the light cone is the entrance pupil, and the point at which the light beams from the light beam groups distributed by the same light cone are converged after leaving the light conduction medium is the exit pupil.

According to a preferred embodiment of the present disclosure, the beam generator includes a laser light source and a microelectromechanical system, wherein the step S81 includes:

s811: emitting a light beam carrying color information and/or brightness information of the image pixels by using a laser light source;

s812: and scanning the light beams emitted from the laser light source by using a micro-electromechanical system to form the light beam group with the light cone distribution.

According to a preferred embodiment of the present disclosure, the step S81 includes:

s813: the method comprises the steps of utilizing a light source to emit divergent illumination light to irradiate a display screen, wherein the light source is a monochromatic or trichromatic laser light source or an LED light source or an OLED light source, and the display screen is a DMD, LCoS or LCD;

s814: loading an image in the display screen, and modulating light irradiated on the display screen by the light source according to the image;

s815: the modulated light is formed into a beam group of the light cone distribution by a diaphragm or lens.

S816: utilizing a light source to emit divergent illumination light, irradiating the divergent illumination light onto a lens, and converging the divergent illumination light onto the vertex of the light cone through the lens, wherein the light source is a monochromatic or trichromatic laser light source or an LED light source or an OLED light source;

s817: the light beam passing through the lens is irradiated onto a display screen between the lens and the vertex, the display screen is a DMD, LCoS or LCD, the display screen loads an image, and the light beam irradiated onto the lens is modulated according to the image.

It should be appreciated that the various exemplary display systems described above may be configured in two sets to provide images for the left and right eyes of a person, respectively, and that a three-dimensional display of binocular parallax may be achieved if the images for left and right eye display contain image information of binocular parallax; if the images displayed by the left and right eyes are ordinary two-dimensional images, ordinary two-dimensional display can be realized. The invention can switch between two-dimensional display and three-dimensional display. Accordingly, the display system may include a switch or controller that may be triggered by a user to switch between a two-dimensional display and a three-dimensional display. It should be appreciated that the display technology implemented by the display system is that of retinal imaging, and that the three-dimensional display implemented reduces or eliminates the problem of vergence adjustment conflicts. In addition, in the optical assembly without imaging distortion based on trapezoidal back projection compensation of the present disclosure, since the first beam combiner is arranged at a certain inclination angle with respect to the second beam combiner, in the manufacture of the beam combiner, the light beam can be easily made incident on the first photosensitive film/plate without intentionally reducing the included angle α.

It should be appreciated that the various exemplary methods described above may be implemented in a variety of ways, for example, in some embodiments, the various methods described above may be implemented using software and/or firmware modules, or using hardware modules. Other ways, now known or developed in the future, are also possible, the scope of the present disclosure is not limited in this respect. In particular, embodiments of the present disclosure may be implemented in the form of a computer program product in addition to hardware embodiments.

Second aspect

The above describes an imaging distortion free optical assembly based on trapezoidal back projection compensation according to the first aspect of the present disclosure, comprising a first beam combiner, a light conducting medium and a second beam combiner attached to two surfaces of the light conducting medium at an oblique angle to each other for changing the propagation direction of the light beam incident thereon, for example such that the incident light beam from the same cone of light continues to propagate and converge to a point after leaving the second beam combiner. A method of manufacturing an optical element is described below, which is particularly suitable for manufacturing a beam combiner or a volume holographic optical element suitable for use in the optical assembly of the first aspect of the present disclosure.

A second aspect of the present disclosure relates to a method of manufacturing an optical element, as shown in fig. 8 and 9.

Fig. 8 illustrates a method 90 of manufacturing an optical element according to a second aspect of the present disclosure. Fig. 9 shows a schematic optical path diagram of a first beam combiner and a second beam combiner manufactured by the method 90. Described in detail below in conjunction with fig. 8 and 9.

As shown in fig. 8, the method 90 includes the steps of:

s91: a photoconductive medium is provided, the photoconductive medium having a first surface and a second surface that are non-parallel to each other, a first photosensitive film/plate being disposed on the first surface, and a second photosensitive film/plate being disposed on the second surface.

As shown in fig. 9, the photoconductive medium 1024 has two surfaces S101 and S102 at an inclination angle to each other, wherein the surface S101 is attached with a first photosensitive film/plate 1018 and the surface S102 is attached with a second photosensitive film/plate 1022. The second photosensitive film/plate 1022 preferably has a width greater than the first photosensitive film/plate 1018. The light-conducting medium 1024 may be, for example, the same as the light-conducting medium shown in fig. 1-6, or have at least partially the same optical and/or geometric parameters.

S92: the laser is used to emit laser light.

Fig. 9 shows three lasers 1001, 1002 and 1003, for example a red laser 1003, a green laser 1002 and a blue laser 1001, respectively. It will be readily appreciated by those skilled in the art that the three lasers shown in fig. 9 are merely illustrative and that the number and wavelength are not limiting of the present disclosure, and that a fewer number of lasers may be employed, and that a greater number of lasers may be employed, all of which are within the scope of the present disclosure. Three lasers are described below as examples.

After the three lasers 1001, 1002, and 1003 emit laser beams of different wavelengths, the laser beams of the three wavelengths are combined by a beam combiner to synthesize the laser beams of the three wavelengths into a high-directivity beamlets. According to a preferred embodiment, the combiner comprises a first splitter plate 1004, a second splitter plate 1005 and a third splitter plate 1006. The first spectroscopic plate 1004 will be described in detail below as an example. The first spectroscopic plate 1004 is disposed downstream of the optical path of the laser 1001, and is, for example, an optical thin film spectroscopic plate corresponding to the wavelength of the blue laser light emitted from the laser 1001, so that the blue light emitted from the laser 1001 is reflected and the light having a wavelength other than the blue light is transmitted. Similarly, the second light splitting sheet 1005 is located downstream of the optical path of the laser 1002 such that green light emitted from the laser 1002 is reflected and light having a wavelength other than green light is transmitted; the third light-splitting sheet 1006 is located downstream of the optical path of the laser 1003 such that red light emitted by the laser 1003 is reflected and light of wavelengths other than red light is transmitted. The reflection paths of the first, second, and third light-splitting sheets 1004, 1005, and 1006 are set to be identical, as shown in fig. 9, whereby the light beams reflected from the three light-splitting sheets eventually synthesize a high-directivity beamlet L00.

According to a preferred embodiment of the present disclosure, the combined laser beam is filtered and collimated to expand the beam. As shown in fig. 9, the combined laser beam is made incident on a microscope objective lens and a pinhole filter 1007, and the high-directivity beamlets are concentrated in pinholes to be filtered, and high-quality spherical waves are emitted and made incident on a collimator lens 1008. The pinhole filter 1007 is located at the focal plane of the collimator lens 1008, and thus the light wave emitted from the pinhole filter 1007 passes through the collimator lens 1008 and is converted into a laser beam L10 of a high quality plane wave.

S93: splitting the laser beam into a first laser beam and a second laser beam.

As shown in fig. 9, for example, the beam splitting may be performed by the first beam splitter 1009, and the first beam splitter 1009 is, for example, a semi-reflective and semi-transparent film, so that a beam incident thereon is partially reflected and partially transmitted, and is split into a first laser beam L11 and a second laser beam L22, and the first laser beam L11 and the second laser beam L22 are derived from the same laser beam, thus having stronger coherence.

S94: splitting the first laser beam into a third laser beam and a fourth laser beam.

As shown in fig. 9, for example, the beam splitting may be performed by the second beam splitter 1011, for example, a semi-reflective and semi-transmissive film, so that a beam portion incident thereon is reflected, a portion is transmitted, and the third laser beam L31 and the fourth laser beam L32 are split into the third laser beam L31 and the fourth laser beam L32, and the third laser beam L31 and the fourth laser beam L32 originate from the same laser beam, and thus have strong coherence.

According to a preferred embodiment of the present disclosure, the first laser beam L11 is condensed before splitting. As shown in fig. 9, since the first photosensitive film/plate 1018 has a smaller width than the second photosensitive film/plate 1022, the first laser beam L11 can be appropriately condensed before being incident on the first photosensitive film/plate 1018 to better match the size of the first photosensitive film/plate 1018. The beam reduction can be achieved, for example, by a diaphragm 1010, which is blocked by the diaphragm 1010, and through which only a spot of a certain size passes, whereby a reduced laser beam L30 is obtained. The laser beam L30 is split into a third laser beam L31 and a fourth laser beam L32 by a second beam splitter 1011.

S95: the third laser beam is converged at a first point outside the photoconductive medium and, after emerging from the first point, is incident on the first photosensitive film/plate, for example, as a divergent spherical wave.

As shown in fig. 9, the third laser beam L31 is converged by the first lens 1012 to a first point 1013, for example, a focal point or a point on a focal plane of the first lens 1012, forms a cone beam, and is incident on the first photosensitive film/plate 1018. The first lens 1012 is only one implementation of focusing the third laser beam L31 to the first point 1013, and the scope of the present disclosure is not limited thereto, and other ways of focusing the third laser beam L31 to the first point 1013 are contemplated.

S96: and converging the fourth laser beam to a second point outside the photoconductive medium, and incidence on the first photosensitive film/first photosensitive plate after emergence from the second point.

As shown in fig. 9, the fourth laser beam L32 is converged by the first mirror 1014, the second mirror 1015, and the second lens 1016 to a second point 1017, for example, a point on the focal point or focal plane of the second lens 1016, to form a cone-shaped beam, and is incident on the first photosensitive film/plate 1018. The first mirror 1014, the second mirror 1015, and the second lens 1016 are only one implementation for converging the fourth laser beam L32 to the second point 1017, and the scope of the present disclosure is not limited in this respect and other ways of converging the fourth laser beam L32 to the second point 1017 are contemplated.

S97: the third laser beam converged to the first point and the fourth laser beam converged to the second point generate interference exposure in the photosensitive material of the first photosensitive film/the first photosensitive plate, and the first volume holographic optical element can be obtained through subsequent processing.

As shown in fig. 9, the third laser beam converged to the first point 1013 is signal light, the fourth laser beam converged to the second point 1017 is reference light, and the signal light and the reference light are subjected to interference exposure inside the first photosensitive film/plate 1018, thereby obtaining a first volume hologram optical element, that is, the first beam combiner.

S98: the fourth laser beam passes through the first photosensitive film/first photosensitive plate, enters the inside of the photoconductive medium, and is incident on the second photosensitive film/second photosensitive plate.

As shown in fig. 9, the fourth laser beam L32 incident on the first photosensitive film/plate 1018 partially passes through the first photosensitive film/plate 1018, enters the interior of the photoconductive medium 1024, continues to propagate, and is incident on the second photosensitive film/plate 1022.

S99: and enabling the second laser beam to pass through the second photosensitive film/second photosensitive plate and then to be converged at a third point outside the photoconductive medium.

As shown in fig. 9, the second laser light beam L22 is converged to the third point 1023 after passing through the third mirror 1019, the fourth mirror 1020, and the third lens 1021. It will be readily appreciated by those skilled in the art that the third point 1023 is not necessarily the focal point or at the focal plane of the third lens 1021, as the second laser beam L22 will be refracted as it passes through the second photosensitive film/plate 1022 and/or the light-conducting medium 1024, and thus the converging third point 1023 may be located in front of or behind the focal point or focal plane of the third lens 1021. Furthermore, it is easily understood by those skilled in the art that the third mirror 1019, the fourth mirror 1020, and the third lens 1021 are just one implementation way to make the second laser beam L22 converge to the third point 1023, and the scope of the present disclosure is not limited thereto, and other ways to converge the second laser beam L22 to the third point 1023 are conceivable.

S100: and the fourth laser beam passing through the first photosensitive film/the first photosensitive plate and entering the inside of the photoconductive medium and the second laser beam converged to the third point generate interference exposure in the photosensitive material of the second photosensitive film/the second photosensitive plate to obtain a second volume holographic optical element.

As shown in fig. 9, the fourth laser beam L32 passing through the first photosensitive film/plate 1018 and entering the light conducting medium 1024 is signal light, the second laser beam L22 converged to the third point 1023 is reference light, the signal light and the reference light are subjected to interference exposure in the second photosensitive film/plate 1022, and the second bulk hologram optical element, that is, the second beam combiner, is obtained after subsequent processing.

As will be readily appreciated by those skilled in the art, in the above-described fabrication path, multiple lasers are combined and then expanded before splitting for exposure. However, it is also possible to expand the beam of light emitted by the lasers and then combine the beam by the mirror and the beam combining beam splitting plate to form a mixed-color plane wave for subsequent exposure, and both implementations are obvious to those skilled in the art and should be considered as being within the scope of the present disclosure.

According to one embodiment of the present invention, when the method of manufacturing the optical element satisfies the following conditions, the manufactured volume hologram optical element may reduce or eliminate the keystone distortion of the image according to the first aspect of the present disclosure during the process for imaging: the third laser beam L31, the fourth laser beam L32, the first photosensitive film/plate 1018, and the second photosensitive film/plate 1022 are disposed such that the sum of the optical paths of any position on the first photosensitive film/plate 1018 where the third laser beam L31 is incident upon the first photosensitive film/plate 1018 after exiting the first point 1013 and the optical paths of the corresponding position on the second photosensitive film/plate 1022 where the fourth laser beam L32 is incident upon the second photosensitive film/plate 1018 via the photoconductive medium 1024 is always equal (as is known from the description of the optical assembly of the first aspect of the present disclosure, there is a correspondence between the respective position points on the first beam combiner or the first photosensitive film/plate and the second beam combiner or the second photosensitive film/plate).

In the embodiment shown in fig. 9, the fourth laser beam L32 is incident on the first photosensitive film/plate 1018 at an angle α to the main propagation direction of the image light (vertically upward direction in the drawing) after converging to the second point 1017. In the optical assembly without imaging distortion based on trapezoidal back projection compensation of the present disclosure, since the first beam combiner is arranged at a certain inclination angle with respect to the second beam combiner, in the manufacture of the beam combiner, the light beam can be easily made incident on the first photosensitive film/plate without deliberately reducing the included angle α.

The optical component without imaging distortion based on trapezoidal reverse projection compensation is further beneficial in that by arranging the first beam synthesizer at a certain inclined angle relative to the second beam synthesizer, the problem that the incidence angle of a light beam is limited when the beam synthesizer is manufactured under the condition that two beam synthesizers are arranged in parallel can be avoided, so that the manufacturing process of the beam synthesizer is simplified and facilitated to a great extent, and the production cost and practical application popularization are reduced.

According to a preferred embodiment of the present disclosure, the direction of the third laser beam is perpendicular to the second surface.

According to a preferred embodiment of the present disclosure, said step S97 and said step S100 are performed simultaneously. That is, the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022 are simultaneously exposed.

Subsequent processing after exposure of the first and second photosensitive films/plates 1018, 1022 may be employed in the trapezoidal reverse projection compensation based imaging distortion free optical assembly of the first aspect of the present disclosure as first and second beam combiners for modulating one or more specific wavelengths of incident light beams. Those skilled in the art will readily understand that the wavelength of the laser light emitted by the laser in step S92 may be the same as or similar to the corresponding wavelength at the time of display. Those skilled in the art will appreciate that wavelengths within 20nm of each other may be referred to as similar. For example, the red laser 1003 in fig. 9 is the same as or similar to the wavelength of the first laser 501 in fig. 4A, the green laser 1002 in fig. 9 is the same as or similar to the wavelength of the second laser 502 in fig. 4A, and the blue laser 1001 in fig. 9 is the same as or similar to the wavelength of the third laser 503 in fig. 4A. It will be appreciated by those skilled in the art that when implementing the display scheme of the present invention using LCoS or DMD as a display device, the color display to be implemented is a time-series color display, the wavelength range of the red, green, blue LEDs or OLEDs to be used should be included in the laser wavelength range used when the first and second photosensitive films/plates 1018 and 1022 are exposed, and the red, green, blue LEDs or OLEDs having a wide wavelength range are screened through the first and second photosensitive films/plates 1018 and 1022 when displayed due to the wavelength selectivity of the volume hologram optical element itself, so that only light having a wavelength satisfying the bragg condition is diffracted, and the color saturation of the displayed image is high. It will be appreciated by those skilled in the art that when the LCD is used as the display device to implement the display scheme of the present invention, the LCD is coated with a color filter, and the displayed colors are simultaneously displayed instead of the time-sequential color display scheme, where red, green, blue LEDs or OLED light beam combination back-illumination may be used, and white LEDs or OLED light may also be used to illuminate, where the light after passing through the color filter carries color and intensity information of the image, and each color light wave has a larger bandwidth, and may still be subjected to certain wavelength selection by the implemented beam combiner during final imaging, so as to implement a color display effect with high saturation.

In addition, it is easily understood by those skilled in the art that the photosensitive film or plate after the interference exposure in steps S97 and S100 may need to be subjected to some subsequent process. For example, for photopolymer materials, subsequent processing steps such as uv curing, thermal curing, etc. are required. The scope of the present disclosure is not limited to the subsequent processing steps.

The exposed first and second photosensitive films/plates 1018, 1022 may be used as first and second beam combiners in an imaging distortion free optical assembly based on trapezoidal back projection compensation according to the first aspect of the present disclosure, although the scope of the present disclosure is not limited in this respect. The laser used for the exposure is, for example, a single longitudinal mode laser, and has strong coherence. When used in the keystone-based backprojection-compensated imaging-distortion-free optical assembly, the laser used as the display light source may be a low-coherence multimode laser, or a corresponding wavelength LED or OLED light source, or a white LED or OLED.

Those skilled in the art will readily appreciate that when the first and second photosensitive films/plates 1018, 1022 are used in the trapezoidal reverse projection compensation based imaging distortion free optical component of the first aspect of the present disclosure, the photoconductive medium in the optical component may be identical to the photoconductive medium 1024 used in fabricating the first and second photosensitive films/plates 1018, 1022, for example, corresponding to the entrance pupil of the optical component, thereby ensuring that the light cone beam is incident on the second beam combiner after entering the photoconductive medium, and can be diffraction modulated and focused to the exit pupil of the optical component. Alternatively, the photoconductive medium in the optical assembly may not be exactly the same as the photoconductive medium 1024 used in fabricating the first and second photosensitive films/plates 1018, 1022, but have at least partially the same optical and/or geometric parameters to ensure that the light cone beam, after entering the photoconductive material, impinges on the second beam combiner in the same or similar direction as the second photosensitive film/plate 1022 when fabricating the first and second photosensitive films/plates 1018, 1022, and is capable of being diffraction modulated to converge at the exit pupil of the optical assembly. For this purpose the physical parameters of the light-conducting medium used for recording may be different from the physical parameters of the light-conducting medium used for display. For example, the light-conducting medium in the optical component is configured such that: the angle of the light beam incident on each point on the second beam combiner attached thereto is the same as the angle of the light beam propagating inside the photoconductive medium 1024 and incident on the point on the second photosensitive film/plate 1022 when the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022 are fabricated. Thereby ensuring that the photoconductive medium in the optical assembly and the first and second beam combiners are able to reasonably modulate the incident light beam.

In accordance with a preferred embodiment of the present disclosure, the photosensitive material on the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022 is a full color photosensitive material. Step S92 includes: a plurality of lasers are utilized to emit laser beams with different wavelengths, and the laser beams are emitted after being combined; steps S97 and S100 each include: interference exposure is performed simultaneously inside the photosensitive material corresponding to different wavelengths of the plurality of lasers. In this way, two volume hologram optical elements of full color can be formed by one exposure.

According to an alternative embodiment of the present disclosure, the photosensitive material on the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022 is a full color photosensitive material. Step S92 includes: sequentially utilizing a plurality of lasers to emit laser beams with different wavelengths and emitting the laser beams; steps S97 and S100 each include: a plurality of interference exposures are sequentially performed inside the photosensitive material corresponding to different wavelengths of the plurality of lasers. For example, in the optical path diagram shown in fig. 9, first, a blue laser beam is emitted by a blue laser 1001, and one exposure is performed in the photosensitive material on the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022; then, the green laser 1002 is caused to emit a green laser beam, and one exposure is performed in the photosensitive material on the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022; then, the red laser 1003 is again caused to emit a red laser beam, and exposure is performed again in the photosensitive material on the first photosensitive film/plate 1018 and the second photosensitive film/plate 1022. After the three exposures, a full-color volume hologram optical element can be formed.

According to an alternative embodiment of the present disclosure, the photosensitive material on the first and second photosensitive films/plates 1018, 1022 is a single color photosensitive material, for example sensitive to only red light. In this case, step S92 includes: the laser device is used for emitting laser beams with the wavelength corresponding to the monochromatic photosensitive material and emitting the laser beams; steps S97 and S100 each include: and performing interference exposure inside the photosensitive material corresponding to the wavelength of the laser to obtain a volume holographic optical element corresponding to the wavelength. The volume hologram optical element thus formed is a monochromatic volume hologram optical element.

According to a preferred embodiment of the present disclosure, after one single-color volume hologram optical element is formed, a photosensitive film/plate that can expose light of different wavelengths may also be replaced, and a plurality of volume hologram optical elements corresponding to the different wavelengths are obtained through the foregoing steps S92 to S100. For example, after the formation of the red volume hologram optical element, a blue-sensitive photosensitive film/plate is replaced, and a blue laser is used to emit laser light and expose the laser light to form a blue volume hologram optical element, and then a green volume hologram optical element is formed. The monochromatic volume hologram optical element formed in this way can be used alone or can be aligned and stacked accurately for use as a beam combiner in the optical assembly of the first aspect of the present disclosure.

In the optical path diagram shown in fig. 9, the finally formed volume hologram optical element is a combination of a transmissive first volume hologram optical element and a reflective second volume hologram optical element. The manufacturing method 90 of the present disclosure may also be used to form a combination of a transmissive first volume holographic optical element and a transmissive second volume holographic optical element, which are in principle communicating.

In addition, it will be appreciated by those skilled in the art that a concave lens may be provided between the beam generator and the first beam combiner during the above manufacturing process, and the same concave lens may be used during display, thereby enabling expansion of the field angle with a small MEMS galvanometer scan angle, which variations are within the scope of the present disclosure.

In addition, it will be appreciated by those skilled in the art that the thickness of the photoconductive medium can be made smaller in order to ensure that the second beam combiner has a certain size when the condition of total reflection is satisfied in the above manufacturing process. As described above, when the total reflection condition is satisfied, the light coupled into the light-conducting medium may be incident on the second beam combiner after the light-conducting medium and the surface of the air are totally reflected once or several times, so as to achieve the requirement of a thinner light-conducting medium. Those skilled in the art will appreciate that when a scheme is employed in which the light reaches the second beam combiner after one or more total reflections, the second beam combiner is also fabricated by exposure taking into account the total reflection. These are all intended to be within the scope of this disclosure.

In addition, the first photosensitive film/plate 1018 (first volume hologram optical element) and the second photosensitive film/plate 1022 (second volume hologram optical element) obtained after exposure can be used as a master to perform copying, so that the manufacturing cost can be greatly reduced and the manufacturing speed can be increased.

The second aspect of the present disclosure also relates to a volume hologram optical element manufactured by the above method 90, wherein the first volume hologram optical element is a transmissive volume hologram optical element and the second volume hologram optical element is a transmissive volume hologram optical element or a reflective volume hologram optical element.

The second aspect of the present disclosure also relates to an imaging distortion free optical assembly based on trapezoidal back projection compensation, comprising a first beam combiner and a second beam combiner manufactured by the above method 90, the remainder being the same as the optical assembly of the first aspect of the present disclosure.

The structure of the optical assembly of the second aspect of the present disclosure is shown in fig. 1 to 6, for example, and thus any feature or combination of features of the optical assembly of the first aspect of the present disclosure may be used in the optical assembly of the second aspect of the present disclosure, and will not be described here again.

A second aspect of the present disclosure also relates to a display system comprising the keystone-based backprojection-compensated imaging-distortion-free optical assembly. The display system is, for example, a virtual reality display system or an augmented reality display system.

According to a preferred embodiment of the present disclosure, the display system further comprises an image generating unit configured to generate an image to be displayed, the image generating unit being coupled to the beam generator, the beams of different directions in the set of beams emitted by the beam generator carrying wavelength information and/or brightness information of different pixels in the image.

According to yet another aspect of the present disclosure, the present disclosure also relates to an imaging distortion free optical assembly and display system based on trapezoidal back projection compensation as described above and the use of an imaging distortion free optical assembly and display system based on trapezoidal back projection compensation manufactured by the method as described above in near-eye display.

It should be noted that embodiments of the present disclosure may be implemented by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or special purpose design hardware. Those of ordinary skill in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such as provided on a carrier medium such as a magnetic disk, CD or DVD-ROM, a programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The apparatus of the present disclosure and its modules may be implemented by hardware circuitry, such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., as well as software executed by various types of processors, or by a combination of the above hardware circuitry and software, such as firmware.

It should be noted that although several modules or sub-modules of the apparatus are mentioned in the detailed description above, this division is not mandatory only. Indeed, in accordance with embodiments of the present disclosure, the features and functions of two or more modules described above may be implemented in one module. Conversely, the features and functions of one module described above may be further divided into a plurality of modules to be embodied.

While the present disclosure has been described with reference to the presently contemplated embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. On the contrary, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

The foregoing description is only of the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Although the present disclosure has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described above, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. An optical assembly, comprising:

a beam generator configured to emit a beam group of light cone distribution;

wherein the first beam combiner is configured to receive the set of light beams of the light cone distribution and to change its direction of propagation such that at least a portion thereof propagates through the light-conducting medium onto the second beam combiner; the second beam combiner is configured to change the propagation direction of the light beam incident on the second beam combiner from the first beam combiner, so that the light beam leaves the second beam combiner at different angles to continue to propagate, wherein the light beams from the light beam group with the same light cone distribution are converged at one point after the direction of the light beam group is changed by the first beam combiner and the second beam combiner, and the light beam group leaves the second beam combiner;

the first beam combiner and the second beam combiner are obliquely arranged, light emitted by the beam generator obliquely enters the first beam combiner, the main direction of the light emitted by the beam generator is perpendicular to the second beam combiner, and the first beam combiner carries out reverse stretching and shape compensation on a projection image in the diffraction process.

2. The optical assembly of claim 1, wherein the profile of the illuminated area of the beam set of light cone distribution in any cross-section perpendicular to the main direction of the beam set is proportional to the profile of the illuminated area formed on the second beam combiner.

3. The optical assembly of claim 1, wherein the principal direction of the set of light beams is perpendicular to a plane in which the second beam combiner lies.

4. The optical assembly of claim 1, wherein an angle between the first and second beam combiners ranges from 20 ° to 80 °.

5. The optical assembly of claim 4, wherein the angle between the first and second beam combiners is 45 °.

6. The optical assembly of claim 1, wherein the first and second beam combiners do not overlap each other in a direction perpendicular to a principal direction of the beam set.

7. The optical assembly of claim 1, wherein the light-conducting medium comprises a waveguide, wherein the light beam exiting the first beam combiner is incident on the second beam combiner after at least one total reflection in the waveguide.

8. The optical assembly of claim 1, wherein the light beam exiting the first beam combiner is directly incident on the second beam combiner through the light-conducting medium.

9. The optical assembly of claim 8, wherein the light conducting medium is air and the first and second beam combiners are secured by an external structure.

10. The optical assembly of claim 1, wherein the optical assembly has an entrance pupil and an exit pupil, the apex of the cone of light being the entrance pupil, the point at which beams from a group of beams of the same cone of light converge after exiting the second beam combiner being the exit pupil.

11. The optical assembly of any one of claims 1-10, wherein the beam generator comprises an image source and a microelectromechanical system,

wherein the laser beam is a monochromatic or trichromatic laser beam.

12. The optical assembly of any of claims 1-10, wherein the beam generator comprises:

13. The optical assembly of any of claims 1-10, wherein the beam generator comprises:

14. The optical assembly of claim 11, wherein the microelectromechanical system comprises a MEMS galvanometer, the image produced by the image source is formed by scanning beamlets carrying color information and/or brightness information of image pixels from lasers of different wavelengths through the MEMS galvanometer, the image source comprises a plurality of lasers of different wavelengths, a controller coupled to the plurality of lasers of different wavelengths and controlling the plurality of lasers of different wavelengths to emit laser beams, the laser beams of the plurality of lasers of different wavelengths are incident on the combiner and are synthesized as nearly parallel beamlets whose spatially coincident propagation paths.

15. The optical assembly of claim 14, wherein the beam combiner comprises a lens group and optical thin film splitters corresponding to wavelengths of the plurality of lasers of different wavelengths, respectively, wherein the lens group is configured to adjust divergence angle and/or diameter of laser beams emitted by the lasers and to project the laser beams onto the corresponding optical thin film splitters to form the near-parallel beamlets having coincident propagation paths in space through reflection or transmission, wherein the lens group can comprise a liquid lens or a liquid crystal lens, and an equivalent focal length of the lens group can be adjusted through external voltage control for controlling divergence angle and/or diameter of laser beams emitted by the lasers.

16. The optical assembly of claim 15, wherein the beam combiner further comprises a stop, a wave plate, a polarizer, an attenuator disposed between the lens group and the optical film splitter, the beam combiner further comprising a micro-motor coupled to the lens group, the micro-motor being operable to adjust the relative position between lenses in the lens group to adjust the divergence angle and/or diameter of the light beam exiting the lens group.

17. The optical assembly according to any one of claims 1-10, wherein the light beams of different directions in the set of light beams carry color information and/or brightness information of different image pixels.

18. The optical assembly of any one of claims 1-10, wherein the first beam combiner comprises a first diffractive optical element, the group of light beams of the light cone distribution diffracting when incident on different locations of the first diffractive optical element, the direction of propagation of diffracted light changing and continuing within the light-conducting medium and incident on different locations of the second beam combiner;

19. The optical assembly of claim 18, wherein the first and second diffractive optical elements are independently volume holographic optical elements, the first and second diffractive optical elements being one of the following combinations:

20. The optical assembly of claim 19, wherein the volume hologram optical element comprises a single color volume hologram optical element that diffracts laser light of different wavelengths of a plurality of lasers.

21. The optical assembly of claim 19, wherein the volume hologram optical element comprises a plurality of single-color volume hologram optical elements accurately aligned and stacked together, corresponding to the number of the plurality of lasers, each single-color volume hologram optical element diffracts only laser light of a corresponding wavelength and does not diffract laser light of other wavelengths.

22. The optical assembly of claim 19, wherein the volume hologram optical element comprises a plurality of volume hologram optical elements accurately aligned and stacked together, the number of the plurality of volume hologram optical elements being less than the number of the plurality of lasers, at least one of the plurality of volume hologram optical elements diffracting laser light of at least two wavelengths of the plurality of lasers and not diffracting laser light of other wavelengths; the remaining volume hologram optical element diffracts laser light of one of the remaining other wavelengths, but does not diffract laser light of the other wavelengths.

23. The optical assembly of claim 19, wherein the volume hologram optical element comprises a single monochromatic volume hologram optical element that diffracts only one wavelength of laser light.

24. The optical assembly of any of claims 20-23, wherein the first and second diffractive optical elements are independently one selected from a single color volume holographic optical element, a plurality of single color volume holographic optical elements precisely aligned and stacked together and corresponding to a number of lasers, a plurality of volume holographic optical elements precisely aligned and stacked together and less than a number of lasers, a single color volume holographic optical element.

25. A display system comprising the optical assembly of any one of claims 1-24.

26. The display system of claim 25, wherein the display system is a virtual reality display system or an augmented reality display system.

27. A display system according to claim 25 or 26, further comprising an image generation unit configured to generate an image to be displayed, the image generation unit being coupled to the beam generator, the beams of different directions in the set of beams emitted by the beam generator carrying color information and/or brightness information of different pixels in the image.

28. A display system according to claim 25 or 26, comprising a left eye display unit and a right eye display unit, wherein the left eye display unit and the right eye display unit each comprise an optical assembly according to any of claims 1-24.

29. Use of an optical assembly according to any of claims 1-24 or a display system according to any of claims 25-28 for near-eye display.

30. An image projection method of an optical system, comprising:

step S81: generating a beam group with light cone distribution;

The first surface is not parallel to the second surface, the first beam combiner and the second beam combiner are obliquely arranged, light emitted by the beam generator obliquely enters the first beam combiner, the main direction of the light emitted by the beam generator is perpendicular to the second beam combiner, and the first beam combiner performs inverse stretching and shape compensation on a projection image.

31. An image projection method according to claim 30, wherein the profile of the illuminated area of the beam group of light cone distribution in any cross section perpendicular to the main direction of the beam group is proportional to the profile of the illuminated area formed on the second beam combiner.

32. The image projection method of claim 30, wherein the principal direction of the set of light beams is perpendicular to a plane in which the second beam combiner lies.

33. The image projection method according to claim 30, wherein the optical system has an entrance pupil and an exit pupil, the vertex of the light cone being the entrance pupil, and the point at which the light beams originating from the light beam group of the same light cone distribution leave the second light beam combiner is the exit pupil.

34. The image projection method according to any one of claims 30 to 33, wherein the beam generator comprises a laser light source and a microelectromechanical system,

wherein the step S81 includes:

35. The image projection method according to any one of claims 30 to 33, wherein the step S81 includes:

36. The image projection method according to any one of claims 30 to 33, wherein the step S81 includes:

37. The image projection method according to any one of claims 30-33, wherein the image projection method is implemented with an optical assembly according to any one of claims 1-24 or a display system according to any one of claims 25-28.