CN113655615A - Large exit pupil optical display device, near-to-eye display device and image projection method - Google Patents
Large exit pupil optical display device, near-to-eye display device and image projection method Download PDFInfo
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Abstract
The present disclosure relates to a large exit pupil optical display device comprising: a beam generator configured to form a beam group having a plurality of light cone distributions with different vertices; a waveguide having an incoupling surface, the incoupled light beam being totally reflected at an interface of the waveguide and a free space; the light beam combiner is positioned on one surface of the waveguide, so that light beams incident on the light beam combiner leave at different angles and continue to propagate, wherein light beams from light beam groups with the same/different light cone distributions are converged at the same/different points; an eyeball tracking unit configured to acquire a position of a pupil; and the control unit is coupled with the light beam generator and the eyeball tracking unit and is configured to adjust the position of the light cone vertex of the light beam group emitted by the light beam generator according to the position of the pupil. The large-exit-pupil optical display device combines a pupil expanding technology and an eyeball tracking technology, and correspondingly adjusts the positions of an entrance pupil and an exit pupil by monitoring the position of the pupil, thereby realizing large-exit-pupil display and having improved stability, flexibility and accuracy.
Description
Technical Field
The present disclosure relates generally to the field of optical display, and more particularly to a large exit pupil optical display device, a near-to-eye display device, and an image projection method.
Background
With the development of computer technology and display technology, Virtual Reality (VR) technology for experiencing a Virtual world through a computer simulation system, and Augmented Reality (AR) technology and Mixed Reality (MR) technology for 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. Near-eye VR display mainly pursues the virtual display of the large visual field of submergence formula, and it is the virtual reality display helmet that corresponds. The near-eye AR and MR technologies aim to realize perspective virtual-real fusion, and correspondingly, augmented reality intelligent glasses or helmets are used. In principle, near-eye display devices for AR as well as MR are also called virtual reality techniques in case of blocking ambient light from entering the user's eyes.
The near-eye display device is generally constructed as a helmet display device or a display device in a glasses shape, and is used for displaying an image displayed by a micro display chip at a far distance through an optical system, enabling human eyes to directly see the displayed enlarged image at the far distance through the near-eye display device, realizing spatial perception positioning by combining with an SLAM technology, realizing interaction through technologies such as gesture recognition, voice recognition and eyeball tracking, and the like, is a novel display technology with important potential commercial application value, and is considered as a novel display technology expected to replace a smart phone.
In recent years, the virtual reality display device has been developed explosively, and many kinds of devices have been provided. International major companies such as Oculus, HTC, Sony, Samsung, etc. have introduced virtual reality helmet display devices, respectively, and research and development of virtual reality display products are actively being carried out in domestic parallel reality, Roc photoelectricity, etc. The near-to-eye display devices used in these virtual reality head-mounted displays are mostly based on the single positive lens display principle, i.e. by placing the display near the object focal plane of the single positive lens, the display will get an erect, enlarged virtual image at infinity at the object side of the lens after passing through the single positive lens.
Near-eye display devices for AR and MR have also been greatly developed in recent years. Such as Microsoft corporation and Magic Leap corporation, have introduced augmented reality products based on augmented reality optical engines that utilize diffractive light waveguides to perform the functions of image in-coupling, out-coupling, and pupil expansion. The technology realizes binocular parallax-based three-dimensional display or double-layer depth volumetric display or common two-dimensional display. And the domestic clear JING optical-electrical, Daojia-resistant and Gordon-valley technologies and the like adopt an array waveguide or a free-form surface AR eyepiece to realize augmented reality. By adopting the technology, two-dimensional display or three-dimensional display can be realized, but the three-dimensional display has the problem of convergence adjustment conflict, namely the convergence of the eye focus and the binocular vision axis of a viewer is inconsistent, so that the problems of visual fatigue, vertigo and the like are caused, and particularly, the discomfort is stronger when the viewer watches a virtual scene with a short distance. Wearing this type of near-to-eye display device for a long period of time is potentially harmful to the vision of young people with immature vision.
One of the biggest challenges for augmented reality helmets or glasses at present is to develop a smaller and more compact optical display core assembly, implement a three-dimensional display technology or a comfortable two-dimensional display without conflict of convergence adjustment, make users more comfortable to wear for a long time, and meet some specific requirements for use in specific occasions.
In addition, the retinal display technology is a display technology in which an image is directly projected to the retina by optical means. In the traditional retina display technology, a display chip such as LCoS (liquid crystal on silicon) is used as an image carrier, display is carried out through a lens system, a semi-transparent and semi-reflective mirror is used for guiding an image into human eyes, and ambient light penetrates through the human eyes to realize penetration type display. The lens group of the scheme has a large volume, the semi-transparent semi-reflecting mirror can attenuate the ambient light brightness by half, and the realization of the compact large-view-field display module which does not attenuate the ambient light is an important problem to be solved urgently in the retina display technology.
Simultaneously, when using augmented reality's intelligent glasses or helmet, if the region of exit pupil is too narrow and small, the slight removal of user's eyeball can surpass the actual effective area of exit pupil that this augmented reality equipped to lead to can't seeing the image, can influence user's use and experience. Therefore, it is of great value to develop an optical display device that is light, thin and compact and allows the user's eyes to move in a wide range.
In addition, by improving the motion structure of the optical display device, for example, forming a plurality of exit pupils rapidly in sequence, thereby approaching the technology of forming an exit pupil region in effect, although it is possible to expand the movable range of the user's eyes to a certain extent, the requirements for the structural stability and circuit control of the optical display device are high, the manufacturing cost and difficulty are increased, and the practical application and popularization of the technology are not facilitated.
Further, in order to solve the above problems, it is necessary to improve the conventional optical display device and the manufacturing method thereof.
The statements in this background section merely represent techniques known to the public and are not, of course, representative of the prior art.
Disclosure of Invention
In view of at least one of the deficiencies of the prior art, the present disclosure provides a large exit pupil optical display device comprising:
a light beam generator configured to form a plurality of light beam groups of light cone distributions; the light cones of the plurality of light beam groups have different vertices;
the waveguide is provided with a coupling-in surface and is used for coupling the light beams in the light beam group into the waveguide, and the light beams coupled into the waveguide are totally reflected at the interface of the waveguide and the free space;
the beam combiner is positioned on one surface of the waveguide, changes the propagation direction of the light beams incident on the waveguide, and enables the light beams to leave the beam combiner at different angles for continuous propagation, wherein the light beams from the light beam group with the same light cone distribution are converged at one point after leaving the beam combiner, and the light beams from the light beam groups with different light cone distributions are converged at different points after leaving the beam combiner;
an eyeball tracking unit configured to acquire a position of a pupil of a user;
the control unit is coupled with the light beam generator and the eyeball tracking unit and is configured to adjust the position of the light cone vertex of the light beam group emitted by the light beam generator according to the position of the pupil of the user.
According to one aspect of the invention, the large exit pupil optical display device has a plurality of entrance pupils including vertices of the cones of the plurality of light beam groups and a plurality of exit pupils including different points at which light beams originating from light beam groups of different cone distributions converge after exiting the beam combiner.
According to one aspect of the invention, the optical beam generator comprises an image source and a micro-electromechanical system,
wherein the image source is configured to generate a light beam carrying color information and/or brightness information of an image pixel; the micro-electro-mechanical system is configured to scan the light beam to form the light beam group with the light cone distribution,
the MEMS comprises an MEMS galvanometer and an MEMS galvanometer moving device, wherein the MEMS galvanometer moving device is connected with the MEMS galvanometer and can enable the MEMS galvanometer to move among a plurality of positions, and each position corresponds to one entrance pupil; at each position, the beams in different directions in the beam group with the light cone distribution scanned by the MEMS galvanometer are coupled in and propagated by the waveguide coupling-in surface, and form a convergence point in a free space through the beam combiner, corresponding to an exit pupil.
According to one aspect of the invention, the optical beam generator comprises an image source and a micro-electromechanical system,
wherein the image source is configured to generate a light beam carrying color information and/or brightness information of an image pixel; the micro-electro-mechanical system is configured to scan the light beam to form the light beam group with the light cone distribution,
the micro-electro-mechanical system comprises a MAHOE optical element and a MEMS galvanometer, the MAHOE optical element is at least provided with a first area and a second area, the entrance pupil at least comprises a first entrance pupil and a second entrance pupil, the exit pupil at least comprises a first exit pupil and a second exit pupil, the light beams are scanned by the MEMS galvanometer and then irradiate onto the first area or the second area of the MAHOE optical element, the light beams irradiating onto the first area are diffracted by the first area of the MAHOE optical element, diffracted light is converged onto the first entrance pupil at different angles to form a light beam group with divergent light cone distribution, enters the waveguide and is diffracted by the beam combiner, and diffracted light in different directions continuously propagates after leaving the beam combiner and is converged onto the first exit pupil; the light beams irradiated on the second area are diffracted by the second area of the MAHOE optical element, the diffracted light is converged to the second entrance pupil at different angles to form a light beam group with divergent light cone distribution, enters the waveguide, is diffracted by the light beam combiner, continues to propagate after leaving the light beam combiner, and is converged to the second exit pupil.
According to one aspect of the present invention, the eye tracking unit comprises a detection light source, a photoelectric sensor and a calculation module, wherein the detection light source is configured to emit detection light to an eye of a user; the detection light is received by the photoelectric sensor after being reflected by eyeballs of the user, and the received image information is sent to the computing module; the calculation module determines the position of a pupil according to the output of the photoelectric sensor and sends a signal to the control unit through conversion; the control unit is coupled with the computing module and the MEMS galvanometer moving device and controls the MEMS galvanometer moving device to move the MEMS galvanometer according to the signal.
According to one aspect of the present invention, the eye tracking unit comprises a detection light source, a photoelectric sensor and a calculation module, wherein the detection light source is configured to emit detection light to an eye of a user; the detection light is received by the photoelectric sensor after being reflected by eyeballs of the user, and the received image information is sent to the computing module; the calculation module determines the position of a pupil according to the output of the photoelectric sensor and sends a signal to the control unit through conversion; the control unit is coupled with the computing module and the MEMS galvanometer, controls the MEMS galvanometer to adjust the angle of the MEMS galvanometer according to the signal, and reflects the light beam from the image source to one of a plurality of areas of the MAHOE optical element, wherein the areas at least comprise a first area and a second area.
According to one aspect of the invention, the detection light source comprises an infrared LED light source.
According to one aspect of the invention, the image generated 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, a controller and a beam combiner, the controller is coupled to the plurality of lasers and controls the plurality of lasers to emit laser beams, and the laser beams of the plurality of lasers are incident on the beam combiner and combined into near-parallel beamlets whose propagation paths spatially coincide.
According to one aspect of the invention, the beam combiner comprises a lens group and optical thin film light splitting sheets respectively corresponding to the wavelengths of the plurality of lasers, wherein the lens group is configured to adjust the divergence angle and/or the diameter of the laser beam emitted by the laser, and the laser beam is projected onto the corresponding optical thin film light splitting sheet to form the near-parallel thin light beams with the spatially coincident propagation paths through reflection or transmission, 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.
According to an aspect of the present invention, the beam combiner further includes a stop, a wave plate, a polarizing plate, an attenuation plate disposed between the lens group and the optical film splitter, and a micro-motor coupled to the lens group, the micro-motor being capable of adjusting a relative position between lenses in the lens group to adjust a divergence angle and/or a diameter of a light beam emitted from the lens group.
According to an aspect of the invention, the light beams of different directions in the set of light beams carry color information and/or brightness information of different image pixels.
According to one aspect of the invention, the beam combiner comprises a diffractive optical element, the beams coupled into the waveguide are diffracted when being incident to different positions of the diffractive optical element after being totally reflected at the interface of the waveguide and the free space, the propagation direction of the diffracted light is changed and the diffracted light is propagated continuously after leaving the beam combiner, wherein the beams from the beam group with the same light cone distribution are converged at one point after leaving the beam combiner.
According to one aspect of the invention, the diffractive optical element is a volume holographic optical element, being a transmissive volume holographic optical element or a reflective volume holographic optical element.
According to one aspect of the invention, the volume holographic optical element comprises a single color volume holographic optical element that diffracts laser light of different wavelengths of the plurality of lasers.
According to one aspect of the present invention, the volume hologram optical element includes a plurality of monochromatic volume hologram optical elements aligned exactly and stacked together, each of the monochromatic volume hologram optical elements diffracting only laser light of a corresponding wavelength and not diffracting laser light of other wavelengths, corresponding to the number of the plurality of lasers.
According to one aspect of the invention, the volume holographic optical element comprises a plurality of volume holographic optical elements that are precisely aligned and stacked together, the number of the plurality of volume holographic optical elements being less than the number of the plurality of lasers, at least one of the plurality of volume holographic optical elements diffracting at least two wavelengths of laser light of the plurality of lasers and not diffracting other wavelengths of laser light; the remaining volume hologram optical elements diffract the remaining laser light of one of the other wavelengths, but do not diffract the remaining laser light of the other wavelengths.
According to one aspect of the invention, the volume holographic optical element comprises a single monochromatic volume holographic optical element that diffracts laser light of only one wavelength.
The invention also provides a near-eye display device comprising the large exit pupil optical display device as described above.
According to one aspect of the invention, the near-eye display device is a virtual reality display device or an augmented reality display device.
According to an aspect of the present invention, the near-eye display device further comprises an image generation unit configured to generate an image to be displayed, the image generation unit being coupled to the light beam generator, wherein light beams of different directions in the light beam group emitted by the light beam generator carry color information and/or brightness information of different pixels in the image.
According to one aspect of the present invention, the near-eye display device 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 the large-exit-pupil optical display device as described above.
The present invention also provides an image projection method of an optical system, including:
monitoring the position of the user's pupil;
generating a light beam group with light cone distribution according to the position of the pupil of the user;
coupling the light beam group distributed by the light cone into a waveguide, wherein the light beam entering the waveguide is totally reflected at the interface of the waveguide and a free space;
and changing the propagation direction of the light beams incident on the light beam combiner through the light beam combiner on one surface of the waveguide, so that the light beams leave the light 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 on the eyeball of the user after leaving the light beam combiner.
According to an aspect of the invention, the image projection method further comprises:
when the position of the pupil of the user is monitored to be changed, the position of the light cone vertex of the light beam group with the light cone distribution is adjusted, so that the light beams of the light beam group with the light cone distribution still converge at one point on the eyeball of the user after leaving the light beam synthesizer.
According to one aspect of the invention, the step of monitoring the position of the user's pupils comprises:
emitting detection light to eyeballs of a user through a detection light source;
receiving reflected light of the detection light reflected by eyeballs of the user through a photoelectric sensor to form image information;
and determining the position of the pupil according to the image information.
According to one aspect of the invention, the step of generating a set of beams of a cone distribution comprises:
emitting a light beam carrying color information and/or brightness information of an image pixel by using an image source;
scanning the light beam emitted from the image source by using an MEMS galvanometer to form a light beam group distributed by the light cone,
wherein the step of adjusting the position of the light cone apex of the light beam group of the light cone distribution comprises:
and changing the position of the MEMS galvanometer by a MEMS galvanometer moving device.
According to one aspect of the invention, the step of generating a set of beams of a cone distribution comprises:
emitting a light beam carrying color information and/or brightness information of an image pixel by using an image source;
receiving and scanning the light beam through a MEMS galvanometer;
receiving the beam from the MEMS galvanometer at a first area thereof through a MAHOE optical element and diffracting to generate a set of beams of the cone distribution,
wherein the step of adjusting the position of the light cone apex of the light beam group of the light cone distribution comprises:
and adjusting the angle of the MEMS galvanometer to scan the light beam emitted from the image source onto the second area of the MAHOE optical element.
The present disclosure addresses the problem of complex and bulky optical components in conventional retinal display technologies, and achieves a compact optical display module and near-to-eye display device through the combination of a waveguide and a beam combiner. Moreover, the angle and wavelength selectivity of the volume holographic optical element are utilized, and the pupil expanding type optical display module with a plurality of entrance pupils and exit pupils is realized through optimized design, so that the displayed image can be observed by human eyes in a larger range, and the comfort and the practicability of the application in VR and AR glasses are improved.
Moreover, the pupil-expanding optical display module is combined with the eyeball tracking technology, the positions of the entrance pupil and the exit pupil are correspondingly adjusted by monitoring the positions of the pupils of the user in real time on the basis of the pupil expansion, and the obtained large-exit-pupil optical display device is stable in structure and performance, has excellent applicability, flexibility and accuracy, and has important commercial application value in the near-eye AR and VR display field.
The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings and specification. Moreover, it should be noted that the terminology used in the description has been chosen primarily for readability and instructional purposes, and may not have been chosen to delineate or circumscribe the inventive subject matter.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure. In the drawings:
figure 1 shows a pupil-expanding optical display module according to a first aspect of the present disclosure;
figure 2 shows a pupil-expanding optical display module according to a first embodiment of the present disclosure;
figure 3 shows a mydriatic optical display module according to a second embodiment of the present disclosure;
FIG. 4 illustrates the structure and connection of the eye tracking unit and the control unit according to a preferred embodiment of the present disclosure;
figure 5 shows a large exit pupil optical display device according to a third embodiment of the present disclosure;
figure 6 shows a large exit pupil optical display device according to a fourth embodiment of the present disclosure;
figure 7 shows a pupil expanding optical display module according to a fifth embodiment of the present disclosure;
fig. 8 illustrates a structure of an image source according to a preferred embodiment of the present disclosure;
FIG. 9 illustrates the structure of a volume holographic optical element according to a preferred embodiment of the present disclosure;
fig. 10 illustrates an image projection method of an optical system according to a third aspect of the present disclosure;
FIG. 11 illustrates an image projection method of an optical system according to a specific embodiment of the present disclosure;
fig. 12 shows a method of manufacturing an optical element according to a fourth aspect of the present disclosure;
FIG. 13 is a schematic optical path diagram illustrating fabrication of a beam combiner by the method of FIG. 12;
fig. 14 shows a schematic diagram of the optical path for making a MAHOE optical element according to a preferred embodiment of the present disclosure.
Detailed Description
In the following, only certain exemplary embodiments are briefly described. As those skilled in the art can appreciate, the described embodiments can 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 flowchart 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 is to 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", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be considered as limiting the present disclosure. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present disclosure, "a plurality" means two or more unless specifically limited otherwise.
In the description of the present disclosure, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and the like are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present disclosure can be understood by those of ordinary skill in the art as appropriate. For example, the present disclosure uses the term "coupled" to indicate that the connection between two terminals can be direct connection, indirect connection through an intermediate medium, electrically wired connection, or wireless connection.
In the present disclosure, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise the first and second features being in direct contact, or may comprise the first and second features being in contact, not directly, but via another feature in between. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
The following disclosure provides many different embodiments or examples for implementing different features of the disclosure. To simplify the disclosure of the present disclosure, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present disclosure. Moreover, the present disclosure may repeat reference numerals and/or reference letters in the various examples, which have been repeated for purposes of simplicity and clarity and do not in themselves dictate a 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 applications of other processes and/or use of other materials.
It is to be noted that, unless otherwise specified, technical or scientific terms used in the present disclosure shall have the ordinary meaning as understood by those skilled in the art to which the present invention pertains.
Specific embodiments of the present disclosure are described below in conjunction with the appended drawings, it being understood that the preferred embodiments described herein are merely for purposes of illustrating and explaining the present disclosure and are not intended to limit the present disclosure.
First aspect
A first aspect of the present disclosure relates to a pupil-expanding optical display module 10, as shown in fig. 1. This is described in detail below with reference to fig. 1.
As shown in fig. 1, the extended pupil type optical display module 10 includes a beam generator 11, a waveguide 12, and a beam combiner 13, and has a plurality of entrance pupils IP and a plurality of exit pupils OP. Wherein the plurality of entrance pupils are distributed within an entrance pupil region IPA and the plurality of exit pupils are distributed within an exit pupil region OPA; the light beam generator 11 is configured to form at one instant in time a set of light beams of a cone distribution at an entrance pupil IP within the entrance pupil area IPA, in which light beams of different directions may carry, for example, color information and/or brightness information of different image pixels.
As shown in fig. 1, the light beam generator 11 may generate a cone of light having a divergence angle θ at a first entrance pupil IP1 within an entrance pupil region IPA, where each light beam may individually carry color and/or brightness information for one image pixel. According to a preferred embodiment of the present disclosure, at the first entrance pupil IP1 within the entrance pupil area IPA, the light beam generator 11 may scan to form the light beam group of the light cone distribution, for example, at a first time instant, the light beam generator 11 emits the light beam L11, at a second time instant, the light beam generator 11 emits the light beam L12, and between the first time instant and the second time instant, the light beam generator 11 emits the light beam between L11 and L12. Alternatively, the light beam generator 11 may emit all or part of the light beam in the light cone at the same time, which is within the scope of the present disclosure.
The skilled person will readily understand that the light beam generator 11 may form a continuous distribution of light beams in the light cone, or may form discrete light rays to form a group 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 apex of the cone of light is located at the location of the entrance pupil. In fig. 1, the divergence angle of the light cone is θ. The beam generator 11 may itself have a divergence angle theta such that the divergence angle of the beam emitted therefrom itself corresponds to the divergence angle theta of the cone of light. Or alternatively the beam generator 11 comprises a laser emitting a high-directivity beamlet, in which case the beam generator 11 may for example comprise scanning means for scanning the high-directivity beamlet emitted by the laser to form a cone of light with a divergence angle θ, as will be described in more detail below. Or alternatively, the light beam generator 11 emits a convergent light beam, and the convergent point is the position of the entrance pupil, i.e. the vertex of the light cone, and the light passing through the convergent point can be regarded as a divergent light beam from the convergent point. All of which are within the scope of the present disclosure. In addition, the light beam emitted by the light beam generator 11 may be a monochromatic light beam, or a polychromatic light beam formed by mixing a plurality of monochromatic lights. In addition to carrying color information, the light beam emitted by the light beam generator 11 may also carry brightness information. A beamlet or high directivity beamlet in the present disclosure, for example, refers to a beam having a beam diameter of less than 2mm or less than 1mm (preferably less than 0.01mm), and a divergence angle of 0.02 to 0.03 degrees or less.
In addition, those skilled in the art will readily understand that the light beams of the light cone distribution formed by the light beam generator 11 may be emitted simultaneously or at different times (e.g., formed by scanning), and all such light beams are within the scope of the present disclosure.
As shown in fig. 1, the light beam generator 11 may also generate a cone of light having a divergence angle θ at a second entrance pupil IP2 within the entrance pupil region IPA, where each light beam may individually carry color and/or brightness information for an image pixel. Similarly to the first entrance pupil IP1, at a second entrance pupil IP2 within the entrance pupil area IPA, the light beam generator 11 may scan the set of light beams forming said light cone distribution, e.g. at a first instant the light beam generator 11 emits the light beam L21, at a second instant the light beam generator 11 emits the light beam L22, between which the light beam generator 11 emits the light beam between L21 and L22.
Those skilled in the art will readily appreciate that the light beam generator 11 may also generate a cone of light with a divergence angle θ at other entrance pupils between the first and second entrance pupils IP1 and IP2, with the boundaries of the entrance pupil region IPA (e.g., IP1 and IP2) determined.
It should be noted here that the plurality of entrance pupils may be distributed in a continuous or discrete manner within the entrance pupil region IPA depending on the structure of the light beam generator 11. According to a preferred embodiment of the present disclosure, the plurality of entrance pupils are continuously distributed within the entrance pupil region IPA, i.e. any location point within the entrance pupil region IPA can be used as the entrance pupil IP. According to another preferred embodiment of the present disclosure, the plurality of entrance pupils are discretely distributed within the entrance pupil region IPA, i.e. there are several location points within the entrance pupil region IPA as the entrance pupil IP. As will be described in detail later.
The waveguide 12 has an incoupling surface 121 for receiving the set of light beams of the light cone distribution formed by the light beam generator 11 and for incoupling into the waveguide the light beams of the set of light beams of the light cone distribution. The outside of a part of the surface of the waveguide 12 is air (or free space), and the refractive index of the waveguide 12 is greater than that of air, so that total reflection occurs at the interface between the waveguide 12 and air under the condition that the light beam coupled into the waveguide satisfies a certain incident angle.
The beam combiner 13 is attached to one surface of the waveguide 12, and is configured to change the propagation direction of the light beams incident thereon, so that the light beams leave the beam combiner 13 at different angles and enter a free space (e.g., air) to continue propagating, wherein the light beams from the light beam group with the same light cone distribution converge at a point after leaving the beam combiner 13, and the convergence point is, for example, an exit pupil OP of the pupil-type optical display module 10. As shown in fig. 1, when the light beam generator 11 generates a light cone with a divergence angle θ at, for example, the first entrance pupil IP1 in the entrance pupil region IPA, any one of the light beams in the light cone distribution defined by the light beams L11 and L12 enters the waveguide 12, is incident on the beam combiner 13 after being totally reflected at the interface between the waveguide 12 and the air, exits the waveguide 12 after being modulated by the beam combiner 13, and continues to propagate into the air and all converge at one point, i.e., the first exit pupil OP 1.
Those skilled in the art will readily appreciate that the refractive index of the beam combiner 13 is, for example, the same as or close to that of the waveguide 12, so that when incident on the location of the beam combiner 13, light will enter the beam combiner without continuing to be totally reflected. For example, the beam combiner may be made of a photosensitive film or by coating a photosensitive material on glass, the refractive index of which is close to that of the waveguide, so that light enters the beam combiner without total reflection.
According to a preferred embodiment of the present disclosure, the beam combiner 13 comprises, for example, a diffractive optical element. The diffractive optical element is attached to one surface of the waveguide 12, light beams in different directions after total reflection at an interface of the waveguide and air are diffracted when being transmitted to different positions of the diffractive optical element in different directions, the transmission direction is changed and enters a free space, and 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 to the one point in the free space.
The diffractive optical element is, for example, a volume hologram optical element, which may be a transmissive volume hologram optical element or a reflective volume hologram optical element. As will be described in detail later.
The operation of the extended pupil type optical display module 10 shown in fig. 1 will be described in detail. In fig. 1, the light beam generator 11 generates a light beam group of a light cone distribution at, for example, the first entrance pupil IP1 within the entrance pupil region IPA, and two light beams L11 and L12 located at the boundary in the light beam group are incident on the coupling-in surface 121 of the waveguide 12, respectively, and are coupled into the interior of the waveguide 12 through the coupling-in surface 121. The light beams L11 and L12 propagate inside the waveguide 12, and total reflection occurs at the interface of the waveguide and a free space (e.g., air) (e.g., at points a and B in fig. 1), and the reflected light is finally incident on the beam combiner 13 (the incident points are, for example, at points C and D in fig. 1). The beam combiner 13 is, for example, a reflective volume hologram optical element, which can diffract the light beam incident thereon regardless of the incident direction or incident angle, and the diffracted light beam converges through a point in space, such as the first exit pupil OP1 of the pupil-expanding type optical display module 10 shown in fig. 1.
Similarly, as shown in fig. 1, when the light beam generator 11 generates a light beam group of a light cone distribution at, for example, the second entrance pupil IP2 within the entrance pupil region IPA, two light beams L21 and L22 located at the boundary in the light beam group are respectively incident on the coupling-in surface 121 of the waveguide 12 and are coupled into the interior of the waveguide 12 through the coupling-in surface 121. The light beams L21 and L22 propagate inside the waveguide 12, are totally reflected at the interface of the waveguide and a free space (e.g., air) (e.g., at points a 'and B' in fig. 1), are finally incident on the beam combiner 13 (the incident points are, for example, at points C 'and D' in fig. 1), and are diffraction-modulated by the beam combiner 13 to converge through a point in the space, for example, the second exit pupil OP2 of the extended pupil type optical display module 10 shown in fig. 1.
As will be readily understood by those skilled in the art, in fig. 1, when the light beam generator 11 generates a light beam group of a light cone distribution at one entrance pupil between the first entrance pupil IP1 and the second entrance pupil IP2 within the entrance pupil region IPA, the light beams in the light beam group finally converge to one exit pupil between the first exit pupil OP1 and the second exit pupil OP 2. Thereby, an exit pupil area OPA is formed between the first exit pupil OP1 and the second exit pupil OP 2.
Fig. 1 shows the light beams L11 and L12 as being incident on the beam combiner 13 after having undergone one total reflection inside the waveguide 12. It will be understood by those skilled in the art that the scope of the present disclosure is not limited to the number of total internal reflections of the waveguide 12, but may also be a number of total internal reflections, which may be determined, for example, by the size of the waveguide and the refractive index of the waveguide material. In addition, the total reflection times of the light beams with different angles can also be different, and the total reflection times are all within the protection scope of the present disclosure. Further, the beam combiner 13 may be attached to the entire surface of one side of the waveguide 12, or may be attached to a partial surface of one side of the waveguide 12.
The beam combiner 13 shown in fig. 1 is a reflective beam combiner, i.e. the incident beam and the beam exiting after passing through the beam combiner 13 are located on the same side (upper side in fig. 1) of the beam combiner 13, wherein the beam combiner 13 implements a beam modulation similar to the reflective type. Those skilled in the art will appreciate that a transmissive beam combiner may be similarly implemented. In this case, the incident light beam and the light beam emitted after passing through the beam combiner that implements the transmission-like light beam modulation are located on both sides (upper and lower sides with respect to fig. 1) of the beam combiner, which are within the scope of the present disclosure.
Hereinafter, different ways of implementing the plurality of entrance and exit pupils of the pupil-expanding type optical display module of the present disclosure will be described.
According to a preferred embodiment of the present disclosure, the light beam generator comprises an image source and a micro electro mechanical system, wherein the image source is configured to generate a light beam carrying color information and/or brightness information of an image pixel; the micro-electro-mechanical system is configured to scan the light beams to form the light beam group with the light cone distribution. Several embodiments of the pupil expansion according to the invention are described in detail below.
First embodiment
According to a first embodiment of the present disclosure, the MEMS comprises a MEMS galvanometer and a MEMS galvanometer moving device, wherein the MEMS galvanometer moving device is connected to the MEMS galvanometer and can move the MEMS galvanometer among a plurality of positions, and each position corresponds to an entrance pupil; at each position, the beams in different directions in the beam group with the light cone distribution scanned by the MEMS galvanometer are coupled in and propagated by the waveguide coupling-in surface, and form a convergence point in a free space through the beam combiner, and the convergence point corresponds to an exit pupil.
As shown in fig. 2, the pupil-expanding type optical display module 20 includes a beam generator 21, a waveguide 22, and a beam combiner 23. Wherein the light beam generator 21 comprises an image source (not shown in the figure) and a micro-electromechanical system, the micro-electromechanical system comprises a MEMS galvanometer 211 and a MEMS galvanometer moving device 212, and the MEMS galvanometer moving device 212 is connected with the MEMS galvanometer 211 and enables the MEMS galvanometer 211 to move (in the up-and-down direction in fig. 2).
The extended pupil type optical display module 20 includes at least two entrance pupils, i.e., a first entrance pupil IP1 and a second entrance pupil IP2, and at least two exit pupils, i.e., a first exit pupil OP1 and a second exit pupil OP 2. The waveguide 22 has a coupling-in face 221. The light beam group of the first cone distribution having its vertex at the first entrance pupil IP1 is coupled into the interior of the waveguide 22 via the coupling-in surface 221, and is totally reflected at the interface of the waveguide 22 and the air, and is incident at the interface of the waveguide 22 and the beam combiner 23 after one or more total reflections. The beam combiner 23 performs diffraction modulation on the light beams incident thereon, so that the light beams enter the free space at different angles to continue to propagate, wherein the light beams in different directions of free space propagation, which are derived from the light beam group of the first light cone distribution, are all converged at the first exit pupil OP 1. Similarly, the light beam group of the second light cone distribution whose vertex is at the second entrance pupil IP2 is coupled into the interior of the waveguide 22 via the coupling-in surface 221, and is totally reflected at the interface of the waveguide 22 and the air, enters the interface of the waveguide 22 and the light beam combiner 23 after one or more total reflections, and is diffraction-modulated by the latter to enter the free space at different angles to continue propagating, wherein the light beams of different directions propagating in the free space, originating from the light beam group of the second light cone distribution, are all converged at the second exit pupil OP 2. Thus, the beam combiner 23 can modulate the light beams from the light beam groups with different cone distributions, for example, the light beams of the light beam group with the first entrance pupil IP1 as the vertex of the cone are diffracted and modulated and then converged to the first exit pupil OP 1; the light beams of the light beam group having the second entrance pupil IP2 as the vertex of the light cone are subjected to diffraction modulation and then converged at the second exit pupil OP 2.
The incident light beam L0 in fig. 2 originates from the image source, carrying color information and/or brightness information of the image pixels. The MEMS galvanometer 211 scans the incident beam L0 to form the set of beams of the cone of light distribution. The MEMS galvanometer moving device 212 is connected to the MEMS galvanometer 211 to change the position of the MEMS galvanometer 211, and each position corresponds to an entrance pupil IP. The MEMS galvanometer 211 is shown in FIG. 2 to have at least two positions 211-1 and 211-2, wherein at position 211-1, the vertex of the beam group of the light cone distribution scanned by the MEMS galvanometer 211 is located at the first entrance pupil IP 1; at position 211-2, the apex of the beam set of the cone of light scanned by the MEMS mirror 211 is located at the second entrance pupil IP 2. The MEMS galvanometer moving device 212 is coupled to the MEMS galvanometer 211 to move and switch the MEMS galvanometer 211 between positions 211-1 and 211-2 as desired. As described above, when the MEMS galvanometer 211 is at the position 211-1, the light beams of the obtained light beam group are finally converged at the first exit pupil OP 1; when the MEMS galvanometer 211 is at position 211-2, the resulting beam of the beam group is finally converged at the second exit pupil OP 2. In this case, the first and second entrance pupils IP1 and IP2 form an entrance pupil region IPA, and the first and second exit pupils OP1 and OP2 respectively form an exit pupil region OPA. Thus, the extended pupil optical display module 20 according to the first embodiment of the present disclosure can realize a plurality of entrance pupils and exit pupils, so that the image formed by scanning can be viewed to a wider range by human eyes.
According to a preferred embodiment of the present disclosure, the MEMS galvanometer moving device is, for example, a micro-motor.
For example, at time 1, the MEMS galvanometer 211 is driven by the micro-motor 212 to be at position 211-1, the combined high-directivity beamlets L0 are scanned by the MEMS galvanometer 211, the scanning light is refracted by the waveguide coupling-in surface 221 and enters the waveguide 22, total reflection occurs at the interface between the waveguide and the air, and the totally reflected high-directivity beamlets are reversely diffracted by the reflective volume hologram optical element 23 and converge at point OP1, i.e., the exit pupil position of time 1. At the time 2, the MEMS galvanometer 211 is driven by the micro-motor 212 to be at the position 211-2, the combined high-directivity beamlet L0 is scanned by the MEMS galvanometer 211, the scanning light is refracted by the waveguide coupling surface 221 to enter the waveguide 22, and is totally reflected at the interface between the waveguide and the air, and the totally reflected high-directivity beamlet is reversely diffracted by the reflective volume holographic optical element 23 and converges at the point OP2, i.e., the exit pupil position of the time 2.
Second embodiment
According to a second embodiment of the present disclosure, the micro-electro-mechanical system includes a MAHOE optical element and a MEMS galvanometer, the MAHOE optical element has at least a first region and a second region, the entrance pupil includes at least a first entrance pupil and a second entrance pupil, and the exit pupil includes at least a first exit pupil and a second exit pupil, wherein a light beam from the image source is scanned by the MEMS galvanometer and then irradiated onto the first region or the second region of the MAHOE optical element, wherein the light beam irradiated onto the first region is diffracted by the first region of the MAHOE optical element, and diffracted light converges at different angles to the first entrance pupil to form a light beam group with divergent light cone distribution, enters a waveguide, is diffracted by a beam combiner, and diffracted light in different directions continues to propagate after leaving the beam combiner and converges to the first exit pupil; the light beams irradiated on the second area are diffracted by the second area of the MAHOE optical element, and the diffracted light is converged to the second entrance pupil at different angles to form a light beam group with divergent light cone distribution, enters the waveguide, is diffracted by the light beam combiner, continues to propagate after leaving the light beam combiner, and is converged to the second exit pupil.
In the present disclosure, the abbreviation "MAHOE" refers to a microlens array volume holographic optical element (microlens array volume holographic optical element).
As shown in fig. 3, the pupil-expanding type optical display module 30 includes a beam generator 31, a waveguide 32, and a beam combiner 33. Wherein the light beam generator 31 includes an image source (not shown in the figure) and a micro-electromechanical system, the micro-electromechanical system includes a MEMS galvanometer 311 and a MAHOE optical element 312, the MAHOE optical element 312 includes a plurality of regions (distributed along the up-down direction in fig. 3), and the MEMS galvanometer 311 can scan the incident light beam and make the light beam irradiate on the regions.
The extended pupil type optical display module 30 includes at least two entrance pupils, i.e., a first entrance pupil IP1 and a second entrance pupil IP2, and at least two exit pupils, i.e., a first exit pupil OP1 and a second exit pupil OP 2. The waveguide 32 has a coupling-in face 321. The MEMS mirrors 311 are similar to the MEMS mirror 211 shown in fig. 2, and are used for receiving the incident light beam L0 and scanning to form a light beam group with a light cone distribution. However, unlike the embodiment of fig. 2, the vertex position of the beam group of the light cone distribution formed by scanning the MEMS galvanometer 311 in fig. 3 is not the entrance pupil position of the pupil-expanding optical display module 30.
The MAHOE optical element 312 shown in fig. 3 is, for example, a reflective volume hologram optical element, which includes at least two regions, i.e., a first region 312-1 and a second region 312-2, wherein the first region 312-1 can converge the light beam incident thereon to a point by diffraction modulation, i.e., a first entrance pupil IP1 of the pupil-expanding type optical display module 30; the second region 312-2 may converge the light beams incident thereon to a point, i.e., the second entrance pupil IP2 of the pupil-expanding type optical display module 30, through diffraction modulation. The light beams converging to the first entrance pupil IP1 or the second entrance pupil IP2 form a light cone distribution of light beam groups, which are coupled into the interior of the waveguide 32 through the coupling-in surface 321 of the waveguide 32, and are totally reflected at the interface of the waveguide 32 and the air once or more, and finally incident on the beam combiner 33, and are further diffraction-modulated by the beam combiner 33 to converge at the position of the first exit pupil OP1 or the second exit pupil OP 2.
The light beam L0 emitted from the image source is scanned by the MEMS galvanometer 311, and when the scanning light beam propagates to the first region 312-1 of the MAHOE optical element 312, it is diffracted in the reverse direction, and the high-directional diffracted light beam converges at the first entrance pupil IP1 and then propagates further, and is refracted through the coupling-in surface 321 of the waveguide 32 to enter the waveguide, and is totally reflected at the interface between the waveguide 32 and the free space, and the totally reflected high-directional light beam is diffracted in the reverse direction by the beam combiner (e.g., the reflective volume hologram optical element in fig. 3) 33 and converges at one point, i.e., the first exit pupil OP 1.
The light beam L0 emitted from the image source is scanned by the MEMS galvanometer 311, and when the scanning light beam propagates to the second region 312-2 of the MAHOE optical element 312, it is diffracted in the reverse direction, the high-directional beamlets after the diffraction in the reverse direction converge on the second entrance pupil IP2 and continue to propagate, and refract into the waveguide through the coupling-in surface 321 of the waveguide 32, and totally reflect at the interface between the waveguide 32 and the free space, and the high-directional beamlets totally reflected are diffracted in the reverse direction by the beam combiner (e.g., the reflective volume holographic optical element in fig. 3) 33 and converge on one point, i.e., the second exit pupil OP 2.
It will be readily appreciated by those skilled in the art that, in addition to the reflective volume hologram optical element described above, the MAHOE optical element according to the present disclosure may also be fabricated as a transmissive volume hologram optical element for achieving multiple entrance and exit pupils for the purpose of expanding the pupil, all within the scope of the present disclosure.
In the above embodiments, the pupil expanding optical display module of the present disclosure can achieve the effect of multiple entrance pupils and exit pupils by setting the MEMS galvanometer moving device to drive the MEMS galvanometer to move (for example, the first embodiment) or by setting the MAHOE optical element with multiple diffraction modulation regions (for example, the second embodiment), so as to achieve the purpose of expanding the pupil.
It will be understood by those skilled in the art that, although there is substantially only one entrance pupil IP and one exit pupil OP at each moment, by increasing the moving speed (e.g. the first embodiment) or the rotating speed (e.g. the second embodiment) of the MEMS galvanometer, for example, so that the light cone vertex of the incident light beam is rapidly switched between the respective entrance pupil positions (IP1 … … IPi … … IP2), the time interval during which the emergent light beam converges at the respective exit pupil positions (OP1 … … OPi … … OP2) is sufficiently short to form multiple exit pupils, i.e. to form one exit pupil region, in effect, close to simultaneously, when it is shorter than the category that can be generally recognized by the human eye. In this case, as mentioned above, the user's eyes may be allowed to move in a wide range, but the requirements for structural stability and circuit control of the related device are correspondingly high.
Second aspect of the invention
A second aspect of the present disclosure relates to a large exit pupil optical display device. The large-exit-pupil optical display device comprises a pupil-expanding optical display module according to the first aspect of the disclosure, an eyeball tracking unit and a control unit, wherein the eyeball tracking unit is configured to acquire the position of the pupil of a user; the control unit is coupled with the light beam generator and the eyeball tracking unit in the pupil expanding type optical display module and is configured to adjust the position of the light cone vertex of the light beam group emitted by the light beam generator according to the position of the pupil of the user.
According to the large exit pupil optical display device disclosed by the present disclosure, the pupil expanding function of the pupil expanding type optical display module is combined with the eye tracking function of the eye tracking unit, wherein when the pupil of the user is located at any exit pupil OP position, the eye tracking unit monitors and converts the pupil position, and then the control unit moves the vertex of the light beam group distributed by the light cone to the entrance pupil IP position corresponding to the exit pupil OP, thereby realizing the display function of the large exit pupil. The large-exit pupil optical display device can adjust the position of the light cone vertex of the emergent light beam of the light beam generator in real time according to the position of the pupil of a user without being limited by the moving speed or the rotating speed of the MEMS galvanometer, and therefore, the large-exit pupil optical display device has excellent flexibility and accuracy, stable structure and performance and low energy consumption.
Fig. 4 shows the structure and connection of the eyeball tracking unit and the control unit according to a preferred embodiment of the present disclosure. Referring to fig. 4, the eye tracking unit 40 includes a detection light source 41, a photoelectric sensor 42, and a calculation module 43, wherein the detection light source 41 emits detection light to an eyeball of a user; the photoelectric sensor 42 records the reflected light data reflected by the eyeball of the user and sends the data to the calculation module 43; the calculation module 43 converts the received reflected light data into a signal containing, for example, spatial coordinate information by calculation. One end of the control unit 44 is connected with the calculation module 43 and receives the signal sent by the calculation module 43; the other end is connected with the light beam generator 451 in the pupil-expanding optical display module 45, and the light beam generator 451 is controlled by the received signal to adjust the position of the vertex of the light cone of the light beam group emitted therefrom (i.e. the entrance pupil IP of the pupil-expanding optical display module 45), so that the exit pupil OP corresponding to the entrance pupil IP matches with the position of the pupil of the user, thereby ensuring that the user can normally view the image. The photosensor 42 is, for example, an image pickup unit, which may be selected from image pickup sensors such as CCD or CMOS, and may be used to pick up an image of the eyeball of the user.
The manner in which a large exit pupil is achieved through a combination of the pupil expansion function and the eye tracking function in accordance with the present disclosure is further described. In the large exit pupil optical display device of the present disclosure, the detection light source in the eye tracking unit first emits detection light to the user's eyes; the detection light is received by the photoelectric sensor after being reflected by the eyeball of the user, for example, array-form image information is formed, the image information can express the difference of parameters such as color or light intensity of different areas, and the image information is sent to the calculation module by the photoelectric sensor; the calculation module determines the position of the pupil according to the characteristics of the image information output by the photosensor (for example, an array with a significantly changed numerical value may correspond to the boundary of the pupil), converts the position into a corresponding electrical signal (for example, including a spatial motion command) through a preset algorithm, and sends the electrical signal to the control unit. One end of the control unit is coupled with the eyeball tracking unit, such as a calculation module therein, and receives an electric signal from the calculation module; the other end is coupled with a light beam generator, such as a micro-electromechanical system therein, and the micro-electromechanical system is controlled to move correspondingly according to the received electric signals.
According to one embodiment of the present disclosure, the detection light emitted by the detection light source to the eyeball of the user is non-visible light, which is preferably an infrared LED light source, and emits invisible infrared light, thereby avoiding affecting the user and reducing the user experience.
In addition, according to an embodiment of the present disclosure, part of the components (e.g., the detection light source and the photoelectric sensor) of the eyeball tracking unit and the functions thereof may be implemented by a common display device such as a camera, and the position of the pupil of the user may be determined by other means besides the above, such as directly capturing an image of the eyeball of the user by the camera and performing image detection. The present invention is not limited to the specific structure and the specific analysis manner of the eyeball tracking unit, as long as the position of the pupil of the user can be appropriately acquired. The eye tracking unit may be implemented using existing technologies, which are commercially available, for example, related products manufactured using TOBII.
According to a preferred embodiment of the present disclosure, the control unit is connected to a MEMS galvanometer moving device (e.g., the MEMS galvanometer moving device 212 shown in fig. 2) in a micro-electro-mechanical system included in the optical beam generator, and the MEMS galvanometer moving device is controlled to adjust the movement of the MEMS galvanometer.
According to a preferred embodiment of the present disclosure, the control unit is connected to a MEMS galvanometer (e.g., the MEMS galvanometer 311 shown in fig. 3) in the MEMS included in the optical beam generator, and reflects the optical beam from the image source onto different areas of the MAHOE optical element by controlling the MEMS galvanometer to adjust its angle.
Third embodiment
According to a third embodiment of the present disclosure, the large exit pupil optical display device includes the pupil-expanding optical display module of the first embodiment of the present disclosure, an eyeball tracking unit and a control unit, wherein a micro-electromechanical system of the pupil-expanding optical display module includes an MEMS galvanometer and an MEMS galvanometer moving device; the control unit is connected with a calculation module in the eyeball tracking unit and an MEMS galvanometer moving device in the pupil expanding type optical display module.
The structures of the pupil-expanding optical display module, the eyeball tracking unit and the control unit are the same as the above, and are not described again here.
As shown in fig. 5, the large exit pupil optical display device 50 includes a pupil-expanding type optical display module 51, an eye tracking unit 54, and a control unit 58, and includes at least two entrance pupils IP1, IP2 and two exit pupils OP1, OP 2. The micro-electro-mechanical system of the pupil-expanding optical display module 51 comprises an MEMS galvanometer 511 and an MEMS galvanometer moving device 512; the eyeball tracking unit 54 includes a detection light source 55, a photoelectric sensor 56, and a calculation module 57; the control unit 58 is connected with the MEMS galvanometer moving device 512 and the calculation module 57; the detection light source 55 may emit detection light toward the eyeball of the user.
At time t1, the user's pupil is at the position of the first exit pupil OP1, and the detection light source 55 emits detection light to the user's eyeball; the photoelectric sensor 56 records reflected light data reflected by the eyeball of the user and sends the formed image information to the calculation module 57; the calculation module 57 determines the position of the pupil according to the characteristics of the received image information, converts the pupil position into an electrical signal containing spatial coordinate information through a preset algorithm, and sends the electrical signal to the control unit 58. The control unit 58 controls the MEMS galvanometer moving device 512 to move the MEMS galvanometer 511 to the position 511-1 according to the electrical signal from the computing module 57, scans the light beam L0 from the image source, and forms a light beam group with a light cone distribution at the position of the first entrance pupil IP 1.
At time t2, the user's pupil is at the position of the second exit pupil OP2, and the detection light source 55 emits detection light to the user's eyeball; the photoelectric sensor 56 records reflected light data reflected by the eyeball of the user and sends the formed image information to the calculation module 57; the calculation module 57 determines the position of the pupil according to the characteristics of the received image information, converts the pupil position into an electrical signal containing spatial coordinate information through a preset algorithm, and sends the electrical signal to the control unit 58. The control unit 58 controls the MEMS galvanometer moving device 512 to move the MEMS galvanometer 511 to the position 511-2 according to the electrical signal from the computing module 57, scans the light beam L0 from the image source, and forms a light beam group with a light cone distribution at the position of the second entrance pupil IP 2.
Fourth embodiment
According to a fourth embodiment of the present disclosure, the large exit pupil optical display device includes the pupil expanding optical display module of the second embodiment of the present disclosure, and an eyeball tracking unit and a control unit, wherein the micro-electromechanical system of the pupil expanding optical display module includes an MEMS galvanometer and a MAHOE optical element having a plurality of regions; the control unit is connected with a calculation module in the eyeball tracking unit and an MEMS (micro-electromechanical systems) galvanometer in the pupil-expanding type optical display module.
The structures of the pupil-expanding optical display module, the eyeball tracking unit and the control unit are the same as the above, and are not described again here.
As shown in fig. 6, the large exit pupil optical display device 60 includes a pupil-expanding type optical display module 61, an eye tracking unit 64, and a control unit 68, and includes at least two entrance pupils IP1, IP2 and two exit pupils OP1, OP 2. The micro-electromechanical system of the pupil-expanding optical display module 61 includes an MEMS galvanometer 611 and a MAHOE optical element 612 with at least two regions; the eyeball tracking unit 64 includes a detection light source 65, a photoelectric sensor 66 and a calculation module 67; the control unit 68 is connected with the MEMS galvanometer 611 and the calculation module 67; the detection light source 65 may emit detection light toward the eyeball of the user.
At time t1, the user's pupil is at the position of the first exit pupil OP1, and the detection light source 65 emits detection light to the user's eyeball; the photoelectric sensor 66 records reflected light data reflected by the eyeball of the user and sends the formed image information to the calculation module 67; the calculation module 67 determines the position of the pupil according to the characteristics of the received image information, converts the pupil position into an electrical signal containing spatial coordinate information through a preset algorithm, and sends the electrical signal to the control unit 68. The control unit 68 controls the MEMS galvanometer 611 to adjust the angle according to the electrical signal from the computing module 67, scans the light beam L0 from the image source, irradiates the first region 612-1 of the MAHOE optical element 612, performs diffraction modulation on the first region 612-1, and forms a light beam group with a light cone distribution at the position of the first entrance pupil IP 1.
At time t2, the user's pupil is at the position of the second exit pupil OP2, and the detection light source 65 emits detection light to the user's eyeball; the photoelectric sensor 66 records reflected light data reflected by the eyeball of the user and sends the formed image information to the calculation module 67; the calculation module 67 determines the position of the pupil according to the characteristics of the received image information, converts the pupil position into an electrical signal containing spatial coordinate information through a preset algorithm, and sends the electrical signal to the control unit 68. The control unit 68 controls the MEMS galvanometer 611 to adjust the angle according to the electrical signal from the computing module 67, scans the light beam L0 from the image source, irradiates the second region 612-2 of the MAHOE optical element 612, performs diffraction modulation on the light beam by the second region 612-2, and forms a light beam group with a light cone distribution at the position of the second entrance pupil IP 2.
It will be appreciated by those skilled in the art that in the first and third embodiments described above, the plurality of entrance pupils may be continuously distributed within the entrance pupil region IPA and the plurality of exit pupils may be continuously distributed within the exit pupil region OPA. In the second and fourth embodiments described above, the plurality of entrance pupils may be discretely distributed within the entrance pupil region IPA, and the plurality of exit pupils may be discretely distributed within the exit pupil region OPA.
As described previously, the large exit pupil optical display device according to the present disclosure may have a plurality of entrance pupils IP and a plurality of exit pupils OP, wherein the light beams in the light beam group of the light cone distribution from each entrance pupil IP are finally converged at the corresponding exit pupil OP, thereby forming an entrance pupil region IPA and a corresponding exit pupil region OPA. That is, the "entrance pupil" and the "exit pupil" of the large exit pupil optical display device of the present disclosure may be one point in space or one region in space, and thus, the image formed by scanning can be viewed to the human eye in a wide range. This is achieved because the volume hologram optical element has certain angle selectivity and wavelength selectivity, that is, the wavelength and propagation angle in the vicinity of the designed wavelength and propagation angle can be diffracted according to the diffraction relationship, and when the wavelength and propagation angle are far from the designed wavelength and propagation angle, the diffraction efficiency is rapidly decreased, and when the diffraction efficiency is decreased to a certain degree, it can be considered that no diffraction occurs. Therefore, when a certain diffraction efficiency is satisfied, the corresponding entrance pupil is not a point but a certain region, and the corresponding exit pupil is not a point but a region. For example, when a silver salt material is used, its angular selectivity may be, for example, in the range of ± 5 °; when a photopolymer is used, its angular selectivity can be, for example, in the range of ± 1.5 °.
Fifth embodiment
In the foregoing first and second embodiments, the pupil-expanding type optical display modules of the present disclosure each have a plurality of entrance pupils and a plurality of exit pupils, which utilize the angular selectivity and wavelength selectivity of the volume hologram optical element, so that the light beam generator forms a light beam group having a plurality of light cone distributions, wherein each light cone vertex corresponds to one entrance pupil; and the light beams of different light beam groups are respectively converged in free space, wherein each convergence point corresponds to one exit pupil. That is, the pupil-expanding optical display module according to the first and second embodiments of the present disclosure implements a pupil expansion by changing the position of the vertex of the light cone of the light beam group having a light cone distribution and converging the light beams in the light beam group at different positions in free space.
According to a fifth embodiment of the present disclosure, there is provided a pupil expanding type optical display module, which is different from the first and second embodiments in that: the beam generator is configured to form a set of beams of a cone of light distribution; and the beam combiner moving device is connected with the beam combiner and can move the beam combiner among a plurality of positions, wherein in each position, the beams in the beam group form a convergent point in free space after being diffracted and modulated by the beam combiner, and the convergent point corresponds to an exit pupil.
According to one embodiment of the present disclosure, the beam combiner moving device is, for example, a micro-motor.
According to one embodiment of the present disclosure, the beam combiner moving device is connected to the waveguide, and moves the beam combiner by moving the waveguide.
The principle and process of implementing a pupil expansion of a pupil expansion type optical display module according to a fifth embodiment of the present disclosure are described below with reference to fig. 7. For convenience of description and understanding, the waveguide is omitted in fig. 7, and the light beam coupled into the waveguide is simplified to be directly incident on the beam combiner without first being totally reflected. It will be appreciated by those skilled in the art that the foregoing omissions and simplifications are made merely for the purpose of providing a clearer and intuitive understanding of those skilled in the art, and do not affect the discussion herein of the display principles and processes.
Referring to fig. 7, the pupil-expanding type optical display module 70 includes a beam generator 71, a waveguide (not shown), and a beam combiner 73. The pupil expanding type optical display module 70 further includes a beam combiner moving device 731, which is connected to the beam combiner 73 and can move the beam combiner 73 (in fig. 7, move in the left-right direction).
The pupil-expanding type optical display module 70 has an entrance pupil IP and at least two exit pupils OP and OP'. The light beam generator 71 emits a light beam LaAnd LbA defined cone of rays distributes a group of rays with the cone apex at the entrance pupil IP location. At time t1, beam combiner 73 is in the initial position. Similarly to the above, the light beam LaAnd LbAny light beam in the defined light beam group enters the waveguide through the coupling-in surface, is totally reflected at the interface between the waveguide and the free space, then enters the beam combiner 73, enters the free space after being diffraction modulated by the beam combiner 73, continues to propagate and is converged at one point, namely the exit pupil OP. At time t2, beam combiner moving means 731 moves beam combiner 73 by distance D in the direction of the arrow in FIG. 71. At this time, the light beam LaAnd LbAny light beam in the defined group of light beams, after passing through the coupling waveguide, is incident on the beam combiner 73 after being totally reflected, and after being diffracted by the beam combiner 73, enters the free space to continue propagating, but the convergence point changes and is located at a distance D from the exit pupil OP along the direction of the arrow in fig. 72I.e. the exit pupil OP'. Thus, the pupil-expanding optical display module according to the fifth embodiment of the present disclosure realizes a pupil expansion by moving the beam combiner under a fixed beam group having a cone distribution.
The principle and process of changing the exit pupil of the pupil-expanding optical display module 70 from OP to OP' will be further described with reference to FIG. 7.
First, according to the present disclosure, the volume holographic optical element satisfies the following diffraction equation:
sin(α)+sin(β)＝K
wherein for any position point on the volume holographic optical element, alpha represents the included angle between the incident ray and the normal, beta represents the included angle between the diffracted ray and the normal, and K represents a constant.
When the beam combiner 73 is in the initial position, as shown in FIG. 7, the beam L is formed by the beamaAnd LbAny light beam L in the defined group of light beamscIncident on the beam combiner 73 at the point S, modulated by the beam combiner 73, and used as a diffracted beam LdAnd converges with the other diffracted beams in the beam group at the exit pupil OP location. Suppose an incident beam LcAt an angle alpha of 60 DEG to the normal N and a diffracted beam LdAn angle β of 0 ° to the normal N (set here for convenience of calculation only, and the same holds for other angles of incidence/diffraction) is then substituted into the values according to the diffraction equation:
sin(60)+sin(0)＝0.8660
when the beam combiner 73 moves by a distance D in the direction of the arrow in FIG. 71While in the beam LaAnd LbBeams L incident on beam combiner 73 at a point S in a defined group of beamsc' diffraction also occurs according to the diffraction relationship. Suppose an incident beam Lc'an angle α' to the normal N of 65 ° (set by way of example only here, and equally applicable for other angles of incidence greater than the angle α), then substituting values according to the diffraction equation above yields:
sin(65)+sin(β')＝0.8660
obtaining the diffracted beam Ld'the angle beta' to the normal N is-2.3086 deg.. The diffracted light beam L satisfies the angle selectivity and the wavelength selectivity of the volume hologram optical elementdAlong which angle other diffracted beams in the beam group converge at a distance D from the exit pupil OP2From this, the position of the exit pupil OP' can be determined.
Thus, in the pupil expanding optical display module according to the fifth embodiment of the present disclosure, when the beam combiner is moved, the exit pupil position is moved accordingly, and the pupil expanding function can be realized.
A fifth embodiment of the present disclosure also provides a large exit pupil optical display device. The large exit pupil optical display device comprises a pupil expanding type optical display module according to a fifth embodiment of the present disclosure, an eyeball tracking unit and a control unit, wherein the pupil expanding type optical display module comprises a light beam combiner moving device which can move a light beam combiner among a plurality of positions; the eyeball tracking unit includes a detection light source, a photoelectric sensor, and a calculation module similarly to the aforementioned third and fourth embodiments; the control unit is connected with a calculation module in the eyeball tracking unit and a beam combiner moving device in the pupil-expanding type optical display module.
Taking fig. 7 as an example, a process of implementing the large exit pupil function of the large exit pupil optical display device according to the fifth embodiment of the present disclosure is briefly described below, wherein the operation of the eye tracking unit is the same as that described above, and is not repeated herein.
At time t, the user's pupil moves from the exit pupil OP position to a distance D from the exit pupil OP in the direction of the arrow in fig. 72At the exit pupil OP' position. The eyeball tracking unit in the large-exit-pupil optical display device judges the change of the pupil position, converts the change into an electric signal through a preset algorithm and sends the electric signal to the control unit. The control unit controls the beam combiner moving device 731 to drive the beam combiner 73 to move by a distance D in the direction of the arrow in fig. 7 according to the received electric signal1So that the light beams in the light beam group with the light cone distribution emitted by the light beam generator 71 are diffracted and modulated by the light beam combiner 73 and then converged at the current position of the pupil of the user.
As can be seen from the above first to fifth embodiments, in order to realize the functions of the extended pupil and the large exit pupil, the extended pupil optical display module and the large exit pupil optical display device of the present disclosure may be configured to adjust not only the position of the vertex of the cone of the beam group emitted from the beam generator but also the position of the beam combiner. Thus, the pupil-expanding type optical display module/large exit pupil optical display device according to the present disclosure may be configured in which the relative positions of the light cone vertex of the light beam group emitted from the light beam generator and the light beam combiner are made adjustable.
In addition, those skilled in the art will appreciate that the technical features in the above first to fourth embodiments and the fifth embodiment can be combined with each other without inventive efforts. For example, for the extended pupil type optical display module/large exit pupil optical display device, the vertex of the light cone of the light beam group emitted from the light beam generator and the position of the light beam combiner may be configured to be adjustable. All of which are within the scope of the present disclosure.
The pupil expanding type optical display module comprises the light beam generator, the waveguide and the light beam synthesizer, and the thickness of the related optical assembly can be effectively reduced. Especially in the case of VR or AR glasses, the thickness of the whole module can be made to be centimeter magnitude or even millimeter magnitude or less. In the existing VR or AR optical module, the light beam generator needs to be arranged at the side of the head of the user and needs to have a certain angle to avoid the light beam being blocked by the forehead of the user, so the thickness of the whole module needs to be made larger. The pupil-expanding optical display module disclosed by the invention can be used without considering the problem of forehead shielding of a user, so that the whole thickness can be smaller.
In addition, according to the pupil expanding type optical display module disclosed by the invention, by utilizing the angle selectivity and the wavelength selectivity of the volume holographic optical element, the position of the light cone vertex of the light beam group emitted by the light beam generator and the corresponding position of the convergence point of the light beams in the light beam group in the free space can be changed through structural design, so that the pupil expanding type optical display module has a plurality of entrance pupils and a plurality of exit pupils, and the purpose of expanding the pupil can be achieved. Therefore, the pupil expanding type optical display module can enable human eyes to observe the scanned and formed image in a large range, and improves the comfort and the practicability in application.
In addition, the present disclosure can provide a large exit pupil optical display device by combining the pupil expansion type optical display module with an eye tracking technology and further introducing an eye tracking function on the basis of the pupil expansion function. The large-exit-pupil optical display device according to the present disclosure can monitor the position of the user's pupil in real time and adjust the positions of the user's entrance pupil and exit pupil accordingly, thus having excellent structural and performance stability and improving applicability, flexibility and accuracy in application.
Fig. 8 illustrates the structure of an image source 80 according to a preferred embodiment of the present disclosure. Described in detail below with reference to fig. 8.
As previously mentioned, a pupil-expanding optical display module according to the present disclosure includes a beam generator, which may include an image source and a micro-electromechanical system. According to a preferred embodiment of the present disclosure, the image source is configured to generate a light beam carrying color information and/or brightness information of an image pixel; the micro-electro-mechanical system is configured to scan the light beams to form a set of light beams having a cone of light distribution. In fig. 8, the image source 80 is configured to generate a light beam L0 carrying color information and/or brightness information for an image pixel, the light beam L0 always being located on the same spatial path.
According to a preferred embodiment of the present disclosure, the beam generator is a beamlet generator, the image source of which comprises a plurality of lasers, a controller and a beam combiner. The controller is coupled to the plurality of lasers and controls the plurality of lasers to emit laser beams, such as controlling the emission time, intensity, and other optical parameters of the lasers. Laser beams of the plurality of lasers are incident to the beam combiner and combined into near-parallel beamlets whose propagation paths are overlapped in space. This is described in detail below with reference to fig. 8.
As shown in fig. 8, the image source 80 comprises lasers, such as a first laser 81, a second laser 82 and a third laser 83, as shown, wherein the first laser 81 is, for example, a red laser, the second laser 82 is, for example, a green laser, and the third laser 83 is, for example, a blue laser, each emitting a laser beam of a corresponding wavelength. Optionally, the image source 80 further comprises a first lens (or lens group) 84, a second lens (or lens group) 85 and a third lens (or lens group) 86 for collimating, or reducing the divergence angle, or compressing the laser beams emitted by the first laser 81, the second laser 82 and the third laser 83 upstream in the optical path, respectively, to form high-directivity beamlets. The beam combiner includes, for example, optical thin film beam splitters corresponding to wavelengths of laser light emitted by the plurality of lasers, and the optical thin film beam splitters are respectively disposed downstream of lenses (or lens groups) corresponding to the lasers, wherein the laser light of the lasers passes through the lenses (or lens groups) and then enters the corresponding optical thin film beam splitters, and forms the near-parallel beamlets whose propagation paths coincide in space through reflection or transmission. Optionally, the beam combiner of the image source 80 includes a first dichroic sheet 87, a second dichroic sheet 88, and a third dichroic sheet 89, corresponding to the red laser 81, the green laser 82, and the blue laser 83, for combining the red, green, and blue laser beams, respectively. The first light splitter 87 is described in detail below as an example. The first light splitter 87 is disposed downstream of the first lens 84 in the optical path, and is, for example, an optical thin film splitter corresponding to the wavelength of the laser light emitted from the first laser 81, so that the red light emitted from the first laser 81 is reflected and light of colors other than red light is transmitted. Similarly, the second dichroic sheet 88 causes green light emitted by the second laser 82 to be reflected and light of colors other than green light to be transmitted; the third dichroic sheet 89 allows the blue light emitted by the third laser 83 to be reflected and light of colors other than the blue light to be transmitted. The red laser light is reflected by the first dichroic sheet 87, incident on the second dichroic sheet 88 and transmitted through the second dichroic sheet 88, and then transmitted through the third dichroic sheet 89. The green laser light is reflected by the second dichroic sheet 88, incident on the third dichroic sheet 89 and transmitted through the third dichroic sheet 89. The blue laser light is reflected by the third light splitter 89. The reflection paths of the first light splitting sheet 87, the second light splitting sheet 88 and the third light splitting sheet 89 are set to be the same as shown in fig. 8, so that the light beams reflected from the three light splitting sheets are finally combined into a light beam L0. 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 that the divergence angle and/or the diameter of a laser beam emitted by the laser can be controlled. The controller may, for example, control the corresponding laser. For example, if only red and green color components are currently projected in a pixel, the first laser 81 and the second laser 82 are controlled by the controller to emit laser beams of corresponding wavelengths, and the third laser 83 is controlled by the controller not to emit laser beams.
In addition, the beam splitter may also be a broadband beam splitter, which allows light in a certain wavelength range to be reflected and transmits light in other wavelength ranges.
In addition, according to a preferred embodiment of the present disclosure, the image source 80 may further include one or more of a diaphragm, a wave plate, a polarizing plate, an attenuation plate (not shown) disposed between the lenses (or lens groups) 84, 85, 86 and the optical film splitters 87, 88, 89. The image source 80 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 a lens group, to adjust optical parameters such as the spot size and/or divergence angle of the light beam exiting the lens (or 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 81, the second laser 82 and the third laser 83, for example, the RGB three-color components corresponding to one pixel of a picture or pattern, respectively transmit laser beams with corresponding wavelengths, and then are combined.
Those skilled in the art will readily appreciate that fig. 8 schematically illustrates that the image source 80 includes three lasers of red, green, and blue, although the scope of the present disclosure is not so limited. For example, the image source 80 may include a greater or lesser number of lasers, and the wavelengths of the lasers may be selected as desired. For example, the image source 80 may include only one laser emitting a monochromatic laser, all 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 emits either a plane wave or a spherical wave, which is collimated and compressed by a lens or a set of lenses, as will be readily understood by those skilled in the art.
As described above, the beam combiner includes, for example, a diffractive optical element, such as a volume hologram optical element, which may be a transmissive volume hologram optical element or a reflective volume hologram optical element. As will be described in detail below.
According to a preferred embodiment of the present disclosure, the volume holographic optical element is a single colored volume holographic optical element, such as a single sheet of colored volume holographic optical film. The single color volume holographic optical film is obtained by, for example, exposing laser beams having wavelengths corresponding to a plurality of lasers, so that laser beams having the wavelengths corresponding to the plurality of lasers can be diffracted and modulated accordingly. For example, when a single color volume holographic optical film sensitive to red, green, and blue lasers is used in the pupil-expanding type optical display module, the color volume holographic optical film can diffract and modulate an incident beam and converge the incident beam at a point outside the waveguide no matter the incident beam is red, green, blue, or a combination of a plurality of the red, green, and blue. The single color volume hologram optical film may be obtained by simultaneous exposure with the laser beams of the plurality of lasers, or may be obtained by performing multiple successive exposures each with a laser beam of one wavelength. The method has the advantages that a plurality of volume holographic optical films do not need to be aligned and stacked together, and the setting mode is simple.
Or alternatively, the volume hologram optical element includes a plurality of monochromatic volume hologram optical elements aligned exactly and stacked together, corresponding to the number of the plurality of lasers, each of the plurality of monochromatic volume hologram optical elements being obtained by exposure to laser light of a wavelength corresponding to one of the plurality of lasers. For example, when three monochromatic volume holographic optical films sensitive to red, green and blue lasers are used for the extended pupil type optical display module, the monochromatic volume holographic optical film sensitive to red lasers only diffracts red lasers and does not diffract lasers with other wavelengths, so that red laser beams incident on the film at different angles enter a free space at different angles and continue to propagate after being subjected to diffraction modulation of the film. The monochromatic volume holographic optical film sensitive to green laser and the monochromatic volume holographic optical film sensitive to blue laser are similar to those of the monochromatic volume holographic optical film sensitive to red laser. It will be readily understood by those skilled in the art that if more wavelengths of lasers are included in the light source, the beam combiner may also include a corresponding volume holographic optical film, all within the scope of the present disclosure. The advantage of this approach is that each volume holographic optical element is only exposed once, and diffraction efficiency is high. 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 low-coherence multimode laser. When the laser diffraction modulation device is used, the beam combiner comprising the three monochromatic volume holographic optical films sensitive to red, green and blue lasers is directly attached to the corresponding surface of the waveguide, and then the diffraction modulation effect of various wavelength beams incident on the beam combiner can be achieved.
Or alternatively, the volume holographic optical element comprises a plurality of volume holographic optical elements that are precisely aligned and stacked together, the number of the plurality of volume holographic optical elements being less than the number of the plurality of lasers, at least one of the plurality of volume holographic optical elements being obtained by laser exposure of at least two of the plurality of lasers, the remaining volume holographic optical elements being obtained by laser exposure of a remaining one of the plurality of lasers. For example, on the basis of the above-described embodiment using three sheets of the monochromatic volume holographic optical films sensitive to red, green and blue lasers, a sheet of the volume holographic optical film sensitive to red and green at the same time is used instead of the monochromatic volume holographic optical film sensitive to red laser and the monochromatic volume holographic optical film sensitive to green laser. The volume holographic optical film sensitive to red and green simultaneously is obtained, for example, by simultaneous or sequential exposure with red and green lasers. Alternatively, a sheet of volume holographic optical film sensitive to both green and blue may be used instead of the monochromatic volume holographic optical film sensitive to green laser and the monochromatic volume holographic optical film sensitive to blue laser; or a sheet of volume holographic optical film sensitive to both red and blue may be used instead of the monochromatic volume holographic optical film sensitive to red laser light and the monochromatic volume holographic optical film sensitive to blue laser light. All of which are within the scope of the present disclosure. This arrangement improves diffraction efficiency while reducing the number of times of stacking, relative to the arrangement of the above-described embodiments that all employ a single-color volume holographic optical element.
Alternatively, the volume hologram optical element includes a sheet of monochromatic volume hologram optical element corresponding to a laser beam of one wavelength and a laser.
In a preferred embodiment of the present disclosure, as shown in fig. 9, the beam combiner 90 includes three monochromatic volume holographic optical films, a first volume holographic optical film 901 (sensitive to red), a second volume holographic optical film 902 (sensitive to green), and a third volume holographic optical film 903 (sensitive to blue), which respectively perform diffraction modulation on beams with different wavelengths. Taking the first holographic optical film 901 with red component as an example, only the red laser beam is diffracted, but the laser beams with other wavelengths are not diffracted, so that the red laser beams incident thereon at different angles enter the free space to continue to propagate at different angles after being diffracted and modulated by the first holographic optical film 901, wherein the beams in different directions propagating in the free space all converge at the exit pupil position. Similarly, the second volume holographic optical film 902 for the green component diffracts only the green laser light without diffracting the laser light with other wavelengths, so that the green laser beams incident thereon at different angles enter the free space to continue to propagate after being diffraction-modulated by the second volume holographic optical film 902 at different angles, wherein the beams in different directions propagating in the free space are converged at the exit pupil position. Similarly, the third volume holographic optical film 903 of the blue component diffracts only the blue laser light and does not diffract the laser light of other wavelengths, so that the blue laser beams incident thereon at different angles enter the free space to continue to propagate at different angles after being diffraction-modulated by the third volume holographic optical film 903, wherein the beams in different directions propagating in the free space are converged at the exit pupil position.
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 in which a photosensitive material is attached to a glass substrate or a resin substrate in such a manner that the photosensitive material includes one or more of a silver salt material, a photopolymer material, and a gelatin material, and the photosensitive material can sense one or more of red light, green light, or blue light. As will be described in detail below.
The embodiments shown in fig. 1 to 7 all use a reflective volume hologram optical element. Those skilled in the art will readily appreciate that the implementation can also be performed using transmissive volume holographic optical elements. The technical features of any of these solutions can be combined into another solution without creative efforts.
A second aspect of the present disclosure is also directed to a near-eye display device comprising the large exit pupil optical display device as described above. The near-eye display device is, for example, a virtual reality display device or an augmented reality display device.
According to one embodiment of the present disclosure, the near-eye display device further includes an image generation unit configured to generate an image to be displayed, the image generation unit being coupled to the light beam generator, light beams of different directions in the light beam group emitted by the light beam generator carrying color information and/or brightness information of different pixels in the image.
The image generation unit is for example used to generate images that need to be presented to a user. The beam generator scans the image, e.g. pixel by pixel, generating a respective laser beam from the red, green and blue components of each pixel, wherein color information and/or brightness information of different pixels in the image is carried. The near-eye display device projects the light beam of the pixel into the eye (e.g., on the retina) of the user through the large exit pupil optical display device as described above, thereby displaying in the eye of the user. Preferably, the near-eye display device includes a left-eye display unit and a right-eye display unit, and includes two sets of the large-exit-pupil optical display devices, wherein the left-eye display unit and the right-eye display unit both include the large-exit-pupil optical display devices, and respectively display the same two-dimensional image for the left eye and the right eye of the user for two-dimensional display, or the two-dimensional image with parallax is used for realizing three-dimensional display based on binocular parallax.
Third aspect of the invention
A third aspect of the present disclosure relates to an image projection method 100 of an optical system. As shown in fig. 10, the image projection method 100 includes:
s101: monitoring the position of the user's pupil;
the position of the user's pupil may be monitored, for example, by the eye tracking unit 40, 54 or 64 described above.
S102: generating a light beam group with light cone distribution according to the position of the pupil of the user;
the apex of the cone of light is located at the location of the entrance pupil corresponding to the user's pupil, such as described with reference to fig. 1-6.
S103: coupling the light beam group distributed by the light cone into a waveguide, wherein the light beam entering the waveguide is totally reflected at the interface of the waveguide and a free space;
s104: and changing the propagation direction of the light beams incident on the light beam combiner through the light beam combiner on one surface of the waveguide, so that the light beams leave the light 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 on the eyeball of the user after leaving the light beam combiner.
According to a preferred embodiment of the present disclosure, the image projection method 100 further includes:
s105: when the position of the pupil of the user is monitored to be changed, the position of the light cone vertex of the light beam group with the light cone distribution is adjusted, so that the light beams of the light beam group with the light cone distribution still converge at one point on the eyeball of the user after leaving the light beam synthesizer.
According to a preferred embodiment of the present disclosure, the step S101 includes:
emitting detection light to eyeballs of a user through a detection light source;
receiving reflected light of the detection light reflected by eyeballs of the user through a photoelectric sensor to form image information;
and determining the position of the pupil according to the image information.
According to a preferred embodiment of the present disclosure, the step S102 includes:
emitting a light beam carrying color information and/or brightness information of an image pixel by using an image source;
scanning the light beam emitted from the image source by using an MEMS galvanometer to form a light beam group distributed by the light cone,
the step S105 includes:
and changing the position of the MEMS galvanometer by a MEMS galvanometer moving device.
According to a preferred embodiment of the present disclosure, the step S102 includes:
emitting a light beam carrying color information and/or brightness information of an image pixel by using an image source;
receiving and scanning the light beam through a MEMS galvanometer;
receiving the beam from the MEMS galvanometer at a first area thereof through a MAHOE optical element and diffracting to generate a set of beams of the cone distribution,
the step S105 includes:
and adjusting the angle of the MEMS galvanometer to scan the light beam emitted from the image source onto the second area of the MAHOE optical element.
According to an embodiment of the present disclosure, as shown in fig. 11, the image projection method 110 includes the following steps:
s111: at the moment T, the pupil of the user is at the first position, and the detection light is emitted to the eyeball of the user through the detection light source and is reflected to the photoelectric sensor;
s112: recording reflected light data reflected by eyeballs of a user through the photoelectric sensor, and sending formed image information to the computing module;
s113: determining the position of the pupil according to the received image information through the computing module, converting the position into an electric signal and sending the electric signal to the control unit;
s114: controlling, by the control unit, the micro-electro-mechanical system according to the received electrical signal such that a beam group of a light cone distribution is formed at a position corresponding to the first position;
s115: and at the moment T', the pupil of the user is at a second position, and the steps S111-114 are repeated, so that a light beam group with light cone distribution is formed at the corresponding position of the second position.
According to a preferred embodiment of the present disclosure, the MEMS comprises a MEMS galvanometer moving device and a MEMS galvanometer, wherein the MEMS galvanometer moving device is connected to the MEMS galvanometer and can move the MEMS galvanometer between a plurality of positions, and each position corresponds to an entrance pupil; at each position, the beams in different directions in the beam group with the light cone distribution scanned by the MEMS galvanometer are coupled in and propagated by the waveguide coupling-in surface, and form a convergence point in a free space through the beam combiner, and the convergence point corresponds to an exit pupil. In this case, the step S114 includes: controlling the MEMS galvanometer moving device to move the MEMS galvanometer through the control unit according to the received electric signals, so that the top point of the light beam group distributed by the light cone is located at the position corresponding to the first position; and the step S115 includes: and controlling the MEMS galvanometer moving device to move the MEMS galvanometer through the control unit according to the received electric signals, so that the vertex of the light beam group distributed by the light cone is positioned at the corresponding position of the second position.
According to a preferred embodiment of the present disclosure, the MEMS comprises a MAHOE optical element and a MEMS galvanometer, the MAHOE optical element has at least a first area and a second area, the entrance pupil includes at least a first entrance pupil and a second entrance pupil, the exit pupil includes at least a first exit pupil and a second exit pupil, wherein a light beam from an image source is scanned by the MEMS galvanometer and then irradiated onto the first area or the second area of the MAHOE optical element, wherein the light beam irradiated onto the first area is diffracted by the first area, diffracted light is converged onto the first entrance pupil at different angles to form a light beam group with a light cone distribution, enters a waveguide and is diffracted by a beam combiner, and diffracted light in different directions continues to propagate and is converged onto the first exit pupil after leaving the beam combiner; the light beams irradiated on the second area are diffracted by the second area, and the diffracted light is converged to the second entrance pupil at different angles to form a light beam group with light cone distribution, enters the waveguide, is diffracted by the light beam combiner, and is continuously propagated after leaving the light beam combiner in different directions and converged to the second exit pupil. In this case, the step S114 includes: controlling the MEMS galvanometer to adjust the angle of the MEMS galvanometer through the control unit according to the received electric signals, and reflecting the light beams from the image source to one of the areas of the MAHOE optical element so that the top points of the light beam groups of the light cone distribution formed by diffraction modulation of the area are positioned at the corresponding position of the first position; the step S115 includes: and the control unit controls the MEMS galvanometer to adjust the angle of the MEMS galvanometer according to the received electric signals, and reflects the light beams from the image source to one of the areas of the MAHOE optical element, so that the top points of the light beam groups of the light cone distribution formed by diffraction modulation of the area are positioned at the corresponding positions of the second position.
The image projection method 100 may be implemented by a large exit pupil optical display device as described above, or by a near-eye display device including a large exit pupil optical display device as described above.
It should be appreciated that the various exemplary display systems described above may be implemented in two sets to provide images to the left and right eyes of a person, respectively. If the images displayed by the left eye and the right eye contain image information of binocular parallax, three-dimensional display of the binocular parallax can be realized; if the images displayed by the left and right eyes are ordinary two-dimensional images, ordinary two-dimensional display can be realized. It should be appreciated that the display system implements a display technology that is a retinal display, and that the three-dimensional display that implements reduces or eliminates the convergence accommodation conflict problem.
It should be appreciated that the foregoing various exemplary methods may be implemented in various ways, for example, in some embodiments, the foregoing various methods may be implemented using software and/or firmware modules, as well as hardware modules. Other ways, now known or later developed, are also possible, and 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.
Fourth aspect of the invention
A fourth aspect of the present disclosure relates to a method 120 of manufacturing an optical element, as shown in fig. 12 and 13. The method is particularly suitable for manufacturing beam combiners or volume holographic optical elements for use in extended pupil type optical display modules of the first aspect of the disclosure and large exit pupil optical display devices of the second aspect of the disclosure.
Fig. 12 shows a method 120 of manufacturing an optical element according to a fourth aspect of the present disclosure. Fig. 13 shows a schematic optical path diagram of a beam combiner manufactured by the manufacturing method 120. As described in detail below in conjunction with fig. 12 and 13.
As shown in fig. 12, the manufacturing method 120 includes the steps of:
s121: a waveguide is provided having a coupling-in face with a photosensitive film/plate attached to a surface of the waveguide.
As shown in fig. 13, the waveguide 1214 has a coupling-in surface 1213 for coupling light beams incident thereon into the waveguide 1214. The outside of a part of the surface of the waveguide 1214 is air, and the refractive index of the waveguide 1214 is larger than that of air, so that the light beam coupled into the waveguide 1214 is totally reflected at the interface between the waveguide 1214 and air under the condition that a certain incident angle is satisfied. A photosensitive film/plate 1216 is attached to one surface of the waveguide 1214. The waveguide 1214 may, for example, be identical to the waveguides shown in fig. 1 to 9, or have at least partially identical optical and/or geometrical parameters.
S122: laser light is emitted by a laser.
Fig. 13 shows three lasers 1201, 1202 and 1203, for example a red laser 1203, a green laser 1202 and a blue laser 1201, respectively. Those skilled in the art will readily understand that the three lasers shown in fig. 13 are merely illustrative, and the number and wavelength thereof do not limit the present disclosure, and a smaller number of lasers may be used, or a larger number of lasers may be used, which are within the scope of the present disclosure. Three lasers will be described as an example.
After the three lasers 1201, 1202 and 1203 emit laser beams with different wavelengths, the laser beams with the three wavelengths are combined by the beam combiner to be combined into a high-directivity thin beam. According to a preferred embodiment, the beam combiner includes a first light splitter 1204, a second light splitter 1205, and a third light splitter 1206. The first light splitter 1204 is taken as an example for detailed description. A first light splitting sheet 1204, for example, an optical thin film light splitting sheet corresponding to the wavelength of blue laser light emitted from the laser 1201, is disposed downstream of the optical path of the laser 1201, so that blue light emitted from the laser 1201 is reflected and light having wavelengths other than the blue light is transmitted. Similarly, a second dichroic sheet 1205 is positioned in the optical path downstream of the laser 1202 such that green light emitted by the laser 1202 is reflected and light of wavelengths other than green is transmitted; a third light splitter 1206 is positioned in the optical path downstream of laser 1203 such that red light emitted by laser 1203 is reflected and light of wavelengths other than red is transmitted. The reflection paths of the first, second and third light splitters 1204, 1205, 1206 are arranged to be the same, as shown in fig. 13, whereby the light beams reflected from the three light splitters eventually combine to form a highly directional beamlet L00.
According to a preferred embodiment of the present disclosure, the combined laser beam is filtered, collimated and expanded. As shown in fig. 13, the combined laser beam is incident on a microscope objective and a pinhole filter 1207, and high-power high-directivity beamlets are converged on a pinhole for filtering, thereby emitting high-quality spherical waves, and then incident on a collimator lens 1208. Here, the pinhole filter 1207 is located at the focal plane of the collimator lens 1208, so that the light wave emitted from the pinhole filter 1207 is converted into the laser beam L00' of a high-quality plane wave after passing through the collimator lens 1208.
S123: the laser light is split into a first laser beam and a second laser beam.
As shown in fig. 13, the beam splitting may be performed by a beam splitter 1209, for example, the beam splitter 1209 is a semi-reflective and semi-transparent film, for example, so that the beam incident thereon is partially reflected, partially transmitted, and 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 and thus have strong coherence.
S124: and converging the first laser beam to a first point outside the waveguide, emitting the first laser beam to a coupling-in surface of the waveguide, entering the waveguide, totally reflecting the first laser beam at an interface between the waveguide and a free space, and irradiating the first laser beam onto the photosensitive film/photosensitive plate.
As shown in fig. 13, the first laser beam L11 passes through the mirror 1210 and the first lens 1211 and converges at a first point 1212 (which is, for example, a focal point of the first lens 1211 or a point on a focal plane) to form a cone beam, and is incident on the coupling-in surface 1213 of the waveguide 1214, and when an angle incidence condition is satisfied, total reflection occurs inside the waveguide 1214, and the cone beam is incident on the photosensitive film/photosensitive plate 1216 after one or more total reflections. The reflecting mirror 1210 and the first lens 1211 are just one implementation of converging the first laser beam L11 to the first point 1212, and the scope of the present disclosure is not limited thereto, and other ways of converging the first laser beam L11 to the first point 1212 are conceivable.
S125: and converging the second laser beam to a second point outside the waveguide after passing through the photosensitive film/plate.
As shown in fig. 13, the second laser beam L22 may be converged by a second lens 1217, for example. It will be readily understood by those skilled in the art that the second point 1215 need not be the focal point of the second lens 1217 or lie in the focal plane, since the second laser beam L22 is refracted as it passes through the photosensitive film/plate 1216 and/or the waveguide 1214, and thus the converging second point 1215 may be located near the focal point of the second lens 1217.
S126: the first laser beam converged to the first point and totally reflected inside the waveguide and the second laser beam converged to the second point generate interference exposure inside the photosensitive material of the photosensitive film/plate, and a volume hologram optical element, i.e., the beam combiner, is obtained.
As shown in fig. 13, the first laser beam L11 converged to the first point 1212 and totally reflected inside the waveguide 1214 is a signal light, and the second laser beam L22 converged to the second point 1215 is a reference light, and the signal light and the reference light undergo interference exposure inside the photosensitive film/plate 1216, and a volume hologram optical element can be obtained by subsequent processing.
In the above fabrication path, the multiple lasers are combined and then expanded, and then split for exposure, as will be readily understood by those skilled in the art. However, the light emitted from the multiple lasers may be expanded and then combined by the reflector and the beam combining and splitting plate to form a mixed planar wave for subsequent exposure, and both implementations will be obvious to those skilled in the art and should be considered as within the scope of the present disclosure.
The exposed photosensitive film/plate 1216 may be used in a pupil-expanding optical display module of the first aspect of the present disclosure for modulating one or more incident light beams of a specific wavelength. Those skilled in the art will readily understand that the laser wavelength emitted by the laser in step S122 may be the same as or similar to the corresponding wavelength in the display. Those skilled in the art will appreciate that wavelengths that differ by less than 20nm may be referred to as being similar. For example, red laser 1203 in fig. 13 has the same or similar wavelength as first laser 81 in fig. 8, green laser 1202 in fig. 13 has the same or similar wavelength as second laser 82 in fig. 8, and blue laser 1201 in fig. 13 has the same or similar wavelength as third laser 83 in fig. 8. It will be understood by those skilled in the art that when the display scheme of the present invention is implemented using LCoS or DMD as the display device, the color display is a time-sequential color display, the wavelength range of the red, green, blue LEDs or OLEDs used should be included in the wavelength range of the laser used when the photosensitive film/photosensitive plate 1216 is exposed, and due to the wavelength selectivity of the volume holographic optical element itself, the light of the red, green, blue LEDs or OLEDs having a wide wavelength range can be screened by the photosensitive film/photosensitive plate 1216, and only the light having the wavelength satisfying the bragg condition is diffracted, so that the saturation of the color of the displayed image is high. It can be understood by those skilled in the art that when the LCD is used as a display device to implement the display scheme of the present invention, the LCD is coated with color filters, and the displayed colors are displayed simultaneously, instead of a time-sequential color display scheme, light of red, green, and blue LEDs or OLEDs may be used for illumination after being combined, or white LEDs or OLEDs may be used for illumination, and the light after passing through the color filters carries color and intensity information of an image, and the light of each color has a relatively large bandwidth, and can still be selected by the implemented beam combiner during final display, thereby implementing a color display effect with high saturation.
In addition, those skilled in the art will readily understand that some subsequent processing may be required for the photosensitive film/plate after the interference exposure in step S126. For example, for the photopolymer material, the subsequent processing steps such as ultraviolet curing, thermal curing and the like are required; for silver salt materials, the subsequent processing steps of development, fixing and bleaching are required to obtain the beam combiner. The scope of the present disclosure is not limited to the subsequent processing steps.
The exposed photosensitive film/plate 1216 may be used as a beam combiner in a pupil-expanding type optical display module according to the first aspect of the present disclosure or a large exit pupil optical display device according to the second aspect of the present disclosure, but the scope of the present disclosure is not limited thereto. The laser used for the exposure is, for example, a single longitudinal mode laser, and has strong coherence. When used in the extended pupil type optical display module or the large exit pupil optical display device, the laser used as the display light source may be a low-coherence multimode laser.
It is easily understood by those skilled in the art that when the photosensitive film/plate 1216 is used in the extended pupil type optical display module of the first aspect of the present disclosure, the waveguide in the extended pupil type optical display module may be identical to the waveguide 1214 used in manufacturing the photosensitive film/plate 1216, and the point 1212, for example, corresponds to the entrance pupil of the extended pupil type optical display module, so as to ensure that the light beams in the cone shape enter the waveguide, are irradiated onto the beam combiner through total reflection, and can be diffracted and modulated to converge on the exit pupil of the extended pupil type optical display module. Alternatively, the waveguide in the extended pupil optical display module may not be identical to the waveguide 1214 used in fabricating the photosensitive film/plate 1216, but have at least partially the same optical and/or geometrical parameters, so as to ensure that the illumination direction of the light cone-shaped light beam entering the waveguide and illuminating different positions on the beam combiner via total reflection is the same as or similar to the direction of the light totally reflected on the waveguide 1214 when fabricating the photosensitive film/plate 1216, and the light cone-shaped light beam can be diffracted and modulated and then converged to the exit pupil of the extended pupil optical display module. For this purpose the physical parameters of the waveguide used for recording may be different from the physical parameters of the waveguide used for display. For example, the waveguides in a pupil-expanding optical display module may be configured such that: the angle of the light beam incident on each point of the beam combiner attached thereto is the same as the angle of the light beam incident on the point of the photosensitive film/plate 1216 after being totally reflected inside the waveguide 1214 when the photosensitive film/plate 1216 is fabricated, thereby ensuring that the waveguide and the beam combiner in the extended pupil type optical display module can reasonably modulate the coupled light beam.
According to a preferred embodiment of the present disclosure, the photosensitive material on the photosensitive film/plate 1216 is a full color photosensitive material. The step S122 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 S126 includes: and simultaneously performing interference exposure inside the photosensitive material corresponding to different wavelengths of the plurality of lasers. In this way, a full-color volume hologram optical element can be formed by one exposure.
According to an alternative embodiment of the present disclosure, the photosensitive material on the photosensitive film/plate 1216 is a full color photosensitive material. The step S122 includes: sequentially emitting laser beams with different wavelengths by using a plurality of lasers and emitting the laser beams; the step S126 includes: a plurality of interference exposures are successively performed inside the photosensitive material corresponding to different wavelengths of the plurality of lasers. For example, in the optical path diagram of fig. 13, first, a blue laser beam is emitted by a blue laser 1201, and a primary exposure is performed in a photosensitive material of a photosensitive film/plate 1216; then, the green laser 1202 is made to emit a green laser beam, and a primary exposure is performed in the photosensitive material of the photosensitive film/plate 1216; the red laser 1203 is then caused to emit a beam of red laser light, which is exposed once in the photosensitive material of the photosensitive film/plate 1216. After three exposures, a full-color volume holographic optical element can be formed.
According to an alternative embodiment of the present disclosure, the photosensitive material on the photosensitive film/plate 1216 is a single color photosensitive material, e.g., sensitive only to red light. In this case, the step S122 includes: emitting laser beams with the wavelength corresponding to the monochromatic photosensitive material by using a laser and emitting the laser beams; the step S126 includes: and carrying out interference exposure in the photosensitive material corresponding to the wavelength of the laser to obtain the 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 forming a single-color volume holographic optical element, the photosensitive film/plate that can expose light with different wavelengths may be replaced, and a plurality of volume holographic optical elements corresponding to the different wavelengths may be obtained through the foregoing steps S122 to S126. The photosensitive material for recording with laser light of different wavelengths may be the same or different, but will be photosensitive to laser light of said wavelengths. For example, after a red volume hologram optical element is formed, a photosensitive film/plate sensitive to blue light is replaced, laser light is emitted from a blue laser and exposure is performed, a blue volume hologram optical element is formed, and then a green volume hologram optical element is formed. The monochromic holographic optical element formed in this way can be used alone or can be aligned and stacked accurately for use as a beam combiner in a pupil-expanding optical display module according to the first aspect of the present disclosure.
In the optical path diagram shown in fig. 13, the volume hologram optical element finally formed is a reflective volume hologram optical element. The fabrication method 120 of the present disclosure can also be used to form transmissive volume holographic optical elements, which are in principle communicating. For example, a transmissive volume hologram optical element may be formed by disposing the second lens 1217 on the opposite side of the waveguide 1214 from the photosensitive film/plate 1216, and disposing a plurality of mirrors so that the second laser beam L22 is incident on the second lens 1217. In addition, a transmissive volume hologram optical element may also be formed by reversely converging the second laser beam L22 by using a concave mirror on the opposite side of the waveguide 1214 from the photosensitive film/plate 1216 instead of the second lens 1217. Of course, the present disclosure is not limited to the various embodiments described above.
In addition, those skilled in the art will appreciate that in the above-described manufacturing process, a concave lens may be provided between the beam generator and the coupling-in surface of the waveguide, and the same concave lens may be used in the display, thereby enabling an expansion of the field angle with a small MEMS galvanometer scanning angle, and such changes are within the scope of the present disclosure.
In addition, the coupling-in surfaces of the waveguides shown in fig. 1 to 9 and 13 are each a recessed coupling-in surface structure. According to a preferred embodiment of the present disclosure, a convex coupling-in face structure may also be employed. The use of a raised incoupling surface structure is advantageous in that the raised structure of the waveguide can be brought into close proximity or contact with the edge where the beam combiner is located, the raised incoupling structure intersecting the plane where the beam combiner is located, the position of intersection being useful for positioning as a starting position for attachment of the beam combiner to the waveguide, and such variations are within the scope of the present disclosure.
According to a preferred embodiment of the present disclosure, the MAHOE optical element can be fabricated by:
as shown in fig. 14, a microlens array 1302 including a plurality of microlenses is disposed on a photosensitive material film 1303. The microlens array 1302 is schematically illustrated in FIG. 14 as including a first microlens 1302-1 and a second microlens 1302-2, and those skilled in the art will readily appreciate that the microlens array 1302 may also include a greater number of microlenses. The first microlens 1302-1 and the second microlens 1302-2 are described below as an example.
A laser (not shown) emits a laser beam as a coherent light source. For example, the laser beam is split, wherein a part of the split beam is collimated and expanded to form a parallel first beam 1301 (plane wave), and the other part of the split beam is collimated and expanded to be focused by a lens to form a second beam 1307 (divergent spherical wave) after a focus 1304. Since the first light beam 1301 and the second light beam 1307 are from the same coherent light source, they have coherence. The first light beam 1301 passes through the first microlens 1302-1 and then converges to a point 1305 on the focal plane of the first microlens 1302-1, wherein the point 1305 corresponds to the second entrance pupil IP2 in fig. 3. The first light beam 1301 passes through the second microlens 1302-2 and converges to a point 1306 at the focal plane of the second microlens 1302-2, wherein the point 1306 corresponds to the first entrance pupil IP1 in fig. 3. After passing through the microlens array 1302, the first light beam 1301 of the plane wave interferes with the second light beam 1307 of the spherical wave emitted from the point 1304 inside the photosensitive material film 1303, thereby forming a volume hologram optical element, i.e., a MAHOE optical element in the present disclosure.
When the MAHOE optical element is in use, the spherical wave emitted from point 1304 is received and is diffracted in the opposite direction, and the diffracted light is converged at points 1305 and 1306. For example, when a high-directivity beamlet of different direction emanating from point 1304 propagates to the area where the phase information of the first microlens 1302-1 is recorded, the high-directivity beamlet of the opposite diffraction will propagate through point 1305; when the differently directed high-directivity beamlet emanating from point 1304 propagates to the area where the phase information of the second microlens 1302-2 is recorded, the oppositely diffracted high-directivity beamlet will propagate through point 1306.
The method of fabricating a MAHOE optical element according to an embodiment of the present disclosure, which is a reflective volume hologram optical element, is described above. On the basis of this, the person skilled in the art can conceive of other production methods for producing, for example, volume holographic optical elements of the transmissive type. It is clear that a volume holographic optical element made transmissive still achieves the objects of the invention, all falling within the scope of protection of the present disclosure.
The fourth aspect of the present disclosure also relates to a volume hologram optical element manufactured by the manufacturing method 120, wherein the volume hologram optical element is a transmissive volume hologram optical element or a reflective volume hologram optical element.
The fourth aspect of the present disclosure also relates to a large exit pupil optical display device comprising a beam combiner manufactured by the manufacturing method 120, the rest being the same as the large exit pupil optical display device of the second aspect of the present disclosure.
The structure of the large exit pupil optical display device of the fourth aspect of the present disclosure is, for example, as shown in fig. 1 to 9, and therefore any feature or combination of features of the large exit pupil optical display device of the second aspect of the present disclosure can be used in the large exit pupil optical display device of the fourth aspect of the present disclosure, and will not be described herein again.
A fourth aspect of the present disclosure is also directed to a near-eye display device comprising the large exit pupil optical display device as described above. The near-eye display device is, for example, a virtual reality display device or an augmented reality display device.
According to a preferred embodiment of the present disclosure, the near-eye display device further comprises an image generation unit configured to generate an image to be displayed, the image generation unit being coupled to the light beam generator, the light beams of different directions in the group of light beams emitted by the light beam generator carrying color information and/or brightness information of different pixels in the image.
It should be noted that the embodiments of the present disclosure can be realized 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 specially designed hardware. Those skilled 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 code being provided on a carrier medium such as a disk, CD-or DVD-ROM, programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier, for example. The apparatus and its modules of the present disclosure may be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above hardware circuits and software, such as firmware.
It should be noted that although in the above detailed description several modules or sub-modules of the apparatus are mentioned, this division is only not mandatory. Indeed, the features and functions of two or more of the modules described above may be implemented in one module, according to embodiments of the present disclosure. Conversely, the features and functions of one module described above may be further embodied as divided into a plurality of modules.
While the present disclosure has been described with reference to presently contemplated embodiments, it is to be understood that the 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 above description is only a preferred embodiment 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 various changes in the embodiments and modifications can be made, and equivalents can be substituted for elements thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Claims (26)
1. A large exit pupil optical display device comprising:
a light beam generator configured to form a plurality of light beam groups of light cone distributions; the light cones of the plurality of light beam groups have different vertices;
the waveguide is provided with a coupling-in surface and is used for coupling the light beams in the light beam group into the waveguide, and the light beams coupled into the waveguide are totally reflected at the interface of the waveguide and the free space;
the beam combiner is positioned on one surface of the waveguide, changes the propagation direction of the light beams incident on the waveguide, and enables the light beams to leave the beam combiner at different angles for continuous propagation, wherein the light beams from the light beam group with the same light cone distribution are converged at one point after leaving the beam combiner, and the light beams from the light beam groups with different light cone distributions are converged at different points after leaving the beam combiner;
an eyeball tracking unit configured to acquire a position of a pupil of a user;
the control unit is coupled with the light beam generator and the eyeball tracking unit and is configured to adjust the position of the light cone vertex of the light beam group emitted by the light beam generator according to the position of the pupil of the user.
2. The large exit pupil optical display device according to claim 1, wherein the large exit pupil optical display device has a plurality of entrance pupils including vertices of the light cones of the plurality of light beam groups and a plurality of exit pupils including different points where the light beams originating from the light beam groups of different light cone distributions converge after exiting the beam combiner.
3. The large exit pupil optical display device according to claim 1 or 2, wherein the beam generator comprises an image source and a micro-electromechanical system,
wherein the image source is configured to generate a light beam carrying color information and/or brightness information of an image pixel; the micro-electro-mechanical system is configured to scan the light beam to form the light beam group with the light cone distribution,
the MEMS comprises an MEMS galvanometer and an MEMS galvanometer moving device, wherein the MEMS galvanometer moving device is connected with the MEMS galvanometer and can enable the MEMS galvanometer to move among a plurality of positions, and each position corresponds to one entrance pupil; at each position, the beams in different directions in the beam group with the light cone distribution scanned by the MEMS galvanometer are coupled in and propagated by the waveguide coupling-in surface, and form a convergence point in a free space through the beam combiner, corresponding to an exit pupil.
4. The large exit pupil optical display device according to claim 1 or 2, wherein the beam generator comprises an image source and a micro-electromechanical system,
wherein the image source is configured to generate a light beam carrying color information and/or brightness information of an image pixel; the micro-electro-mechanical system is configured to scan the light beam to form the light beam group with the light cone distribution,
the micro-electro-mechanical system comprises a MAHOE optical element and a MEMS galvanometer, the MAHOE optical element is at least provided with a first area and a second area, the entrance pupil at least comprises a first entrance pupil and a second entrance pupil, the exit pupil at least comprises a first exit pupil and a second exit pupil, the light beams are scanned by the MEMS galvanometer and then irradiate onto the first area or the second area of the MAHOE optical element, the light beams irradiating onto the first area are diffracted by the first area of the MAHOE optical element, diffracted light is converged onto the first entrance pupil at different angles to form a light beam group with divergent light cone distribution, enters the waveguide and is diffracted by the beam combiner, and diffracted light in different directions continuously propagates after leaving the beam combiner and is converged onto the first exit pupil; the light beams irradiated on the second area are diffracted by the second area of the MAHOE optical element, the diffracted light is converged to the second entrance pupil at different angles to form a light beam group with divergent light cone distribution, enters the waveguide, is diffracted by the light beam combiner, continues to propagate after leaving the light beam combiner, and is converged to the second exit pupil.
5. The large exit pupil optical display device according to claim 3, wherein the eye tracking unit comprises a detection light source, a photosensor, and a calculation module, wherein the detection light source is configured to emit detection light to the user's eye; the detection light is received by the photoelectric sensor after being reflected by eyeballs of the user, and the received image information is sent to the computing module; the calculation module determines the position of a pupil according to the output of the photoelectric sensor and sends a signal to the control unit through conversion; the control unit is coupled with the computing module and the MEMS galvanometer moving device and controls the MEMS galvanometer moving device to move the MEMS galvanometer according to the signal.
6. The large exit pupil optical display device according to claim 4, wherein the eye tracking unit comprises a detection light source, a photosensor, and a calculation module, wherein the detection light source is configured to emit detection light to the user's eye; the detection light is received by the photoelectric sensor after being reflected by eyeballs of the user, and the received image information is sent to the computing module; the calculation module determines the position of a pupil according to the output of the photoelectric sensor and sends a signal to the control unit through conversion; the control unit is coupled with the computing module and the MEMS galvanometer, controls the MEMS galvanometer to adjust the angle of the MEMS galvanometer according to the signal, and reflects the light beam from the image source to one of a plurality of areas of the MAHOE optical element, wherein the areas at least comprise a first area and a second area.
7. The large exit pupil optical display device of claim 5 or 6, wherein the detection light source comprises an infrared LED light source.
8. The large exit pupil optical display device of claim 7, wherein the image generated by the image source is formed by scanning beamlets from lasers of different wavelengths that carry color information and/or brightness information of image pixels through the MEMS galvanometer, the image source comprising a plurality of lasers, a controller, and a combiner, the controller coupled to the plurality of lasers and controlling the plurality of lasers to emit laser beams, the laser beams of the plurality of lasers incident on the combiner and combined into near-parallel beamlets whose propagation paths spatially coincide.
9. The large exit pupil optical display device according to claim 8, wherein the beam combiner comprises a lens group and optical thin film splitters respectively corresponding to the wavelengths of the plurality of lasers, wherein the lens group is configured to adjust the divergence angle and/or diameter of the laser beam emitted by the laser, and project onto the corresponding optical thin film splitters to form, through reflection or transmission, the near-parallel beamlets whose propagation paths are spatially coincident, wherein the lens group may 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 diameter of the laser beam emitted by the laser.
10. The large exit pupil optical display device of claim 9 wherein the beam combiner further comprises a stop, a wave plate, a polarizer, an attenuator plate disposed between the lens group and the optical film splitter plate, the beam combiner further comprising a micro-motor coupled to the lens group, the micro-motor being capable of adjusting the relative position between the lenses in the lens group to adjust the divergence angle and/or diameter of the light beam exiting the lens group.
11. The large exit pupil optical display device according to claim 1 or 2, wherein differently directed light beams in the set of light beams carry color information and/or brightness information for different image pixels.
12. The large exit pupil optical display device according to claim 1 or 2, wherein the beam combiner comprises a diffractive optical element, and the beams coupled into the waveguide diffract when incident on different positions of the diffractive optical element after total reflection at the interface between the waveguide and the free space, and the propagation direction of the diffracted light changes and continues to propagate out of the beam combiner, wherein the beams from the group of beams with the same cone distribution converge after leaving the beam combiner.
13. The large exit pupil optical display device of claim 12, wherein the diffractive optical element is a volume holographic optical element, being a transmissive volume holographic optical element or a reflective volume holographic optical element.
14. The large exit pupil optical display device of claim 13 wherein the volume holographic optical element comprises a single color volume holographic optical element that diffracts laser light of different wavelengths of the plurality of lasers.
15. The large exit pupil optical display device of claim 13 wherein the volume holographic optical element comprises a plurality of individual color volume holographic optical elements aligned exactly in position and stacked together, corresponding to the number of the plurality of lasers, each individual color volume holographic optical element diffracting only laser light of the corresponding wavelength and not other wavelengths.
16. The large exit pupil optical display device of claim 13 wherein the volume holographic optical element comprises a plurality of volume holographic optical elements that are precisely aligned and stacked together, the number of the plurality of volume holographic optical elements being less than the number of the plurality of lasers, at least one of the plurality of volume holographic optical elements diffracting at least two wavelengths of laser light of the plurality of lasers and not diffracting other wavelengths of laser light; the remaining volume hologram optical elements diffract the remaining laser light of one of the other wavelengths, but do not diffract the remaining laser light of the other wavelengths.
17. The large exit pupil optical display device of claim 13 wherein the volume holographic optical element comprises a single monochromatic volume holographic optical element that diffracts laser light of only one wavelength.
18. A near-eye display device comprising the large exit pupil optical display device of any one of claims 1-17.
19. The near-eye display device of claim 18, wherein the near-eye display device is a virtual reality display device or an augmented reality display device.
20. The near-eye display device of claim 18 or 19, further comprising an image generation unit configured to generate an image to be displayed, the image generation unit being coupled to the light beam generator, light beams of different directions of the set of light beams emitted by the light beam generator carrying color information and/or brightness information of different pixels in the image.
21. The near-eye display device of claim 18 or 19, comprising a left-eye display unit and a right-eye display unit, wherein the left-eye display unit and right-eye display unit each comprise the large-exit-pupil optical display device of any one of claims 1-17.
22. An image projection method of an optical system, comprising:
monitoring the position of the user's pupil;
generating a light beam group with light cone distribution according to the position of the pupil of the user;
coupling the light beam group distributed by the light cone into a waveguide, wherein the light beam entering the waveguide is totally reflected at the interface of the waveguide and a free space;
and changing the propagation direction of the light beams incident on the light beam combiner through the light beam combiner on one surface of the waveguide, so that the light beams leave the light 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 on the eyeball of the user after leaving the light beam combiner.
23. An image projection method according to claim 22, further comprising:
when the position of the pupil of the user is monitored to be changed, the position of the light cone vertex of the light beam group with the light cone distribution is adjusted, so that the light beams of the light beam group with the light cone distribution still converge at one point on the eyeball of the user after leaving the light beam synthesizer.
24. An image projection method according to claim 22 or 23, wherein the step of monitoring the position of the user's pupil comprises:
emitting detection light to eyeballs of a user through a detection light source;
receiving reflected light of the detection light reflected by eyeballs of the user through a photoelectric sensor to form image information;
and determining the position of the pupil according to the image information.
25. An image projection method according to claim 23, wherein the step of generating a set of beams of a cone distribution comprises:
emitting a light beam carrying color information and/or brightness information of an image pixel by using an image source;
scanning the light beam emitted from the image source by using an MEMS galvanometer to form a light beam group distributed by the light cone,
wherein the step of adjusting the position of the light cone apex of the light beam group of the light cone distribution comprises:
and changing the position of the MEMS galvanometer by a MEMS galvanometer moving device.
26. An image projection method according to claim 23, wherein the step of generating a set of beams of a cone distribution comprises:
emitting a light beam carrying color information and/or brightness information of an image pixel by using an image source;
receiving and scanning the light beam through a MEMS galvanometer;
receiving the beam from the MEMS galvanometer at a first area thereof through a MAHOE optical element and diffracting to generate a set of beams of the cone distribution,
wherein the step of adjusting the position of the light cone apex of the light beam group of the light cone distribution comprises:
and adjusting the angle of the MEMS galvanometer to scan the light beam emitted from the image source onto the second area of the MAHOE optical element.
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| CN202010398804.7A CN113655615A (en) | 2020-05-12 | 2020-05-12 | Large exit pupil optical display device, near-to-eye display device and image projection method |
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| WO2023125088A1 (en) * | 2021-12-30 | 2023-07-06 | 比亚迪股份有限公司 | Display apparatus, vehicle, and control method for vehicle |
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| CN114815262A (en) * | 2022-05-17 | 2022-07-29 | 常山县亿思达电子有限公司 | Contact MR (magnetic resonance) lens system based on bidirectional microvibration scanning projection imaging |
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