CN112505925A - Compact augmented reality near-to-eye device - Google Patents
Compact augmented reality near-to-eye device Download PDFInfo
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- CN112505925A CN112505925A CN202011424837.0A CN202011424837A CN112505925A CN 112505925 A CN112505925 A CN 112505925A CN 202011424837 A CN202011424837 A CN 202011424837A CN 112505925 A CN112505925 A CN 112505925A
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B27/0172—Head mounted characterised by optical features
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B27/0172—Head mounted characterised by optical features
- G02B2027/0174—Head mounted characterised by optical features holographic
Abstract
The invention discloses a compact augmented reality near-to-eye device, and relates to the technical field of augmented reality display. The device comprises an LCoS module, an optical machine system and a volume holographic slab waveguide set; the incident surface of the optical-mechanical system is parallel to the emergent surface of the LCoS module, and the optical-mechanical system is used for receiving light emergent from the LCoS module; the emergent surface of the optical-mechanical system is adjacent to the upper surface of the volume holographic slab waveguide set, and the optical-mechanical system is used for converting the LED light source into polarized light and then emergent the polarized light to the volume holographic slab waveguide set; the volume holographic flat waveguide group is used for diffractively transmitting the polarized light and coupling out for imaging. The invention can improve the light effect, realize pupil expansion, ensure the continuity and integrity of the final image, improve the bright and dark stripes of the displayed image and solve the problem of serious crosstalk of similar color light.
Description
Technical Field
The invention relates to the technical field of augmented reality display, in particular to a compact augmented reality near-to-eye device.
Background
The augmented reality technology aims to superimpose a virtual image generated by a computer to a real environment in real time, so that human eyes observe a scene with fusion of reality and virtuality, thereby enhancing real environment information. Therefore, the main problem in the near-eye display device based on the augmented reality technology is how to reduce the volume and weight of the display device, provide sufficient information amount and angle of view, and realize the lightness of the device and the near-eye three-dimensional rendering effect with high spatial resolution and high angular resolution.
However, in the current stage, the microdisplay in the near-eye display device generally needs a high-power and high-brightness illumination unit, which is not favorable for the integration optimization of the system. On the other hand, if a single-layer composite volume holographic grating waveguide is used for transmitting color images, the problem of serious crosstalk of similar color light can occur, and if a plurality of layers of single-color volume holographic grating waveguides are used for transmitting R, G, B three-color light respectively, the dynamic field range of the holographic waveguide can be greatly limited due to the angle selectivity of the volume holographic grating, and the brightness of coupled images is too low, so that the brightness requirement of an augmented reality display device on output images cannot be met.
Disclosure of Invention
The invention aims to provide a compact augmented reality near-to-eye device, which is used for improving the light efficiency, realizing pupil expansion, ensuring the continuity and integrity of a final image, improving the bright and dark stripes of a displayed image and solving the problem of serious crosstalk of similar color light when a display device adopts a composite grating to transmit a color image.
In order to achieve the above object, an embodiment of the present invention provides a compact augmented reality near-eye device, including an LCoS module, an optical engine system, and a volume hologram slab waveguide set; the incidence surface of the optical-mechanical system is parallel to the emergent surface of the LCoS module, and the optical-mechanical system is used for receiving the light emergent from the LCoS module; the emergent surface of the optical-mechanical system is adjacent to the upper surface of the volume holographic slab waveguide group, and the optical-mechanical system is used for converting the light emitted by the LCoS module into polarized light and then emitting the polarized light to the volume holographic slab waveguide group; the volume holographic slab waveguide group comprises a plurality of layer volume holographic slab waveguides, and each volume holographic slab waveguide comprises an adjustable attenuation sheet, an in-coupling volume holographic grating, an out-coupling volume holographic grating and a waveguide plate; the adjustable attenuation sheet is arranged on the upper surface of the waveguide plate and is positioned at the coupling end of the volume holographic slab waveguide; the coupling-in body holographic grating and the coupling-out body holographic grating are arranged on the lower surface of the waveguide plate and are respectively positioned at the coupling-in end and the coupling-out end of the body holographic slab waveguide; and the volume holographic flat waveguide group is used for diffracting and transmitting the polarized light and coupling out for imaging.
Preferably, the compact augmented reality near-to-eye device further comprises an LED light source comprising R, G and a B three-color light source, and a controller for controlling the LED light source to rapidly time-share light R, G and the B three-color light source to realize color illumination.
Preferably, the optical-mechanical system comprises a beam splitter prism, a polarizer, a first half-wave plate, a first quarter-wave plate, a concave mirror, a second quarter-wave plate, a convex mirror and a second half-wave plate; the polaroid, the concave mirror, the convex mirror and the second half-wave plate are respectively arranged on different end face sides of the beam splitter in parallel; the first half-wave plate is arranged between the polaroid and the beam splitter prism; the first quarter-wave plate is arranged between the concave mirror and the beam splitter prism; the second quarter-wave plate is arranged between the convex mirror and the beam splitter prism; the second half-wave plate is arranged between the volume holographic slab waveguide group and the beam splitter prism.
Preferably, the first end face of the beam splitter prism parallel to the polarizing plate is parallel to the adjustable attenuation plate of the volume holographic slab waveguide set; the beam splitting prism is parallel to the second end face of the first quarter-wave plate, is parallel to the third end face of the second quarter-wave plate, and is perpendicular to the first end face.
Preferably, the volume holographic slab waveguide set comprises three layers of overlapped volume holographic slab waveguides, namely a first volume holographic slab waveguide, a second volume holographic slab waveguide and a third volume holographic slab waveguide; the incoupling volume holographic grating of the first volume holographic slab waveguide diffracts only red light; the incoupling volume holographic grating of the second volume holographic slab waveguide diffracts only green light; the incoupling volume holographic grating of the third volume holographic slab waveguide diffracts only blue light.
Preferably, the in-coupling volume holographic grating and the out-coupling volume holographic grating each comprise two identical reflective volume holographic gratings that are compositely stacked with each other.
Preferably, the incoupling volume holographic grating and the outcoupling volume holographic grating are mirror-symmetrical.
Preferably, the material of the waveguide plate is transparent optical glass or transparent optical plastic.
Preferably, the in-coupling volume holographic grating and the out-coupling volume holographic grating are multiplexed volume holographic gratings manufactured based on an angular multiplexing technique.
The embodiment of the invention also provides a preparation method of the holographic grating of the multiplex volume based on the angle multiplexing technology, which is applied to the compact augmented reality near-to-eye device of the embodiment, and the method comprises the following steps: taking any one of R, G, B three colors of monochromatic light to record a volume holographic grating with multiplexed angles; during recording, the positions of object light and reference light are kept fixed, and different angle channels are obtained by rotating a recording material; multiplexing and recording interference fringes in each angle channel, and obtaining a series of angle-multiplexed volume holographic grating units in a volume holographic polymer; during recording, the initial position of the material is ensured to enable the optical axis of the material to be positioned on an angle bisector of an included angle formed by object light and reference light.
The embodiment of the invention has the following beneficial effects:
the invention provides a compact augmented reality near-to-eye device, which utilizes the characteristics that a self-luminous LCoS module integrating an LCoS module and an LED light source can provide high-brightness output light and low power consumption to design a small and high-efficiency micro-display optical system, greatly reduces the volume and weight of elements, reduces the size of the system, simultaneously has a more compact structure and is suitable for being worn by a human body. Meanwhile, the multiplexing volume holographic grating manufactured based on the angle multiplexing technology is used as a light coupling-in/coupling-out device to acquire three-dimensional virtual object image information at a multi-angle channel, so that the dynamic range observed by human eyes is increased, and the view field is expanded. On the other hand, because the existing display device has the problem of serious crosstalk of similar color light when the existing display device adopts the single-layer composite type volume holographic grating waveguide to transmit color light, the embodiment of the invention adopts the multilayer single-layer composite type volume holographic grating waveguide to respectively transmit R, G, B three colors of light so as to solve the problem of serious crosstalk of the similar color light. In addition, the coupling-in/coupling-out device of the volume holographic waveguide in the embodiment of the invention adopts the composite volume holographic grating formed by two pieces of composite stacking, can effectively reuse lost 0-order diffraction light to improve the light efficiency when a color image is transmitted, and can solve the technical problem that the brightness of a coupled-out image is too low to meet the brightness requirement of an augmented reality display device on an output image due to the angle selectivity of a single-color volume holographic grating in the prior art. Meanwhile, pupil expansion can be realized, the continuity and the integrity of the final image are ensured, and the purpose of displaying light and shade stripes of the image is improved.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a compact augmented reality near-eye device according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an optical-mechanical system in a compact augmented reality near-to-eye device according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a volume holographic slab waveguide set in a compact augmented reality near-to-eye device according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a manufacturing principle of a multi-angle multiplexed volume holographic grating based on material rotation according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be understood that the step numbers used herein are for convenience of description only and are not intended as limitations on the order in which the steps are performed.
It is to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "comprises" and "comprising" indicate the presence of the described features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The term "and/or" refers to and includes any and all possible combinations of one or more of the associated listed items.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a compact augmented reality near-eye device according to an embodiment of the present invention. The embodiment of the invention provides a compact augmented reality near-to-eye device, which comprises an LCoS module 1, an optical-mechanical system 2 and a volume holographic slab waveguide group 3; the incidence surface of the optical-mechanical system 2 is parallel to the emergence surface of the LCoS module 1, and the optical-mechanical system 2 is used for receiving light emergent from the LCoS module 1; the emergent surface of the optical-mechanical system 2 is adjacent to the upper surface of the volume holographic slab waveguide group 3, and the optical-mechanical system 2 is used for converting light emitted by the LCoS module into polarized light and then emitting the polarized light to the volume holographic slab waveguide group 3; the volume holographic slab waveguide group 3 comprises a plurality of layer volume holographic slab waveguides, and each volume holographic slab waveguide comprises an adjustable attenuation sheet, an incoupling volume holographic grating, an outcoupling volume holographic grating and a waveguide plate; the adjustable attenuation sheet is arranged on the upper surface of the waveguide plate and is positioned at the coupling end of the volume holographic slab waveguide; the coupling-in body holographic grating and the coupling-out body holographic grating are arranged on the lower surface of the waveguide plate and are respectively positioned at the coupling-in end and the coupling-out end of the body holographic slab waveguide; the volume holographic slab waveguide group 3 is used for diffractively transmitting the polarized light and coupling out for imaging.
The compact augmented reality near-eye device provided by the embodiment of the invention further comprises an LED light source and a controller, wherein the LED light source comprises R, G and a three-color B light source, and the controller is used for controlling the LED light source to rapidly light the R, G and the three-color B light source in a time-sharing manner so as to realize color illumination. In this embodiment, the controller is a computer, the LED light source in the self-luminous LCoS module 1 is controlled by the computer, and color illumination is realized by quickly lighting R, G, B light sources in a time-sharing manner.
The embodiment adopts a self-luminous LCoS (liquid Crystal on silicon) display integrated with an LCoS module and an LED light source, can provide high-brightness output light and has the characteristic of low power consumption, designs a small and exquisite high-efficiency micro-display optical system, greatly reduces the volume and the weight of elements, reduces the system size, simultaneously has a more compact structure, and is suitable for being worn by a human body. Meanwhile, the multiplexing volume holographic grating manufactured based on the angle multiplexing technology is used as an optical coupling-in/coupling-out device to achieve the purpose that three-dimensional virtual object image information is obtained at a multi-angle channel, the dynamic range observed by human eyes is greatly increased, and therefore the view field is expanded.
Referring to fig. 2, fig. 2 is a schematic structural diagram of an optical-mechanical system in a compact augmented reality near-to-eye device according to an embodiment of the present invention. In the present embodiment, the optical-mechanical system 2 includes a beam-splitting prism 211, a polarizer 212, a first half-wave plate 213, a first quarter-wave plate 214, a concave mirror 215, a second quarter-wave plate 216, a convex mirror 217, and a second half-wave plate 218; the polarizing plate 212, the concave mirror 215, the convex mirror 217, and the second half-wave plate 218 are respectively disposed in parallel on different end face sides of the beam splitter prism 211; the first half-wave plate 213 is disposed between the polarizing plate 212 and the beam splitting prism 211; the first quarter-wave plate 214 is disposed between the concave mirror 215 and the beam splitting prism 211; the second quarter wave plate 216 is disposed between the convex mirror 217 and the beam splitter prism 211; the second half-wave plate 218 is disposed between the volume hologram slab waveguide set 3 and the beam splitting prism 211.
The beam splitter prism 211 is a Polarization Beam Splitter (PBS), which is an optical element for separating the horizontal polarization and the vertical polarization of light, and splits incident unpolarized light into two vertical linearly polarized lights. The polarization beam splitter prism is an optical element which is characterized in that a multilayer film structure is plated on the inclined plane of a right-angle prism, then a cubic structure is glued, the P polarization component is completely transmitted, and most of S polarization component is reflected (at least more than 90%) after the light passes through the multilayer film structure for multiple times at the Brewster angle by utilizing the properties that the P polarization transmission rate is 1 and the S polarization transmission rate is less than 1 when the light is incident at the Brewster angle. It should be noted that the working effect of the polarization splitting prism is wavelength limited. In addition, the purity requirements for polarization are high and a glan thompson prism can be used.
In one embodiment, the beam splitter prism 211 is parallel to the first end surface of the polarizer 212 and parallel to the adjustable attenuator 311 of the volume hologram slab waveguide set 3; the beam splitter prism 211 is parallel to the second end surface of the first quarter-wave plate 214, parallel to the third end surface of the second quarter-wave plate 216, and perpendicular to the first end surface.
In this embodiment, when a three-dimensional color virtual object image is loaded on the LCoS module 1, light emitted from the LCoS display is diffraction image light which is modulated by the three-dimensional color virtual object image and carries information of the three-dimensional color virtual object image, and then the diffraction image light is incident to the optical-mechanical system 2. The diffraction image light carrying the image information of the three-dimensional color virtual object forms P-polarized light perpendicular to the incident plane through the polarizer 212 in the optical-mechanical system 2, and is converted into S-polarized light through the first half-wave plate 213. The light enters the beam splitter 211, is totally reflected by a beam splitting film of the beam splitter and enters the concave mirror 215 (wherein the concave mirror 215 and the convex mirror 217 are respectively a concave mirror and a convex mirror capable of reflecting light) after passing through the first quarter-wave plate 214, and is reflected by the concave mirror 215 and then converted into P-polarized light through the first quarter-wave plate 214 again. The P-polarized light reaches the beam splitting film of the beam splitter prism and is transmitted completely, then passes through the second quarter wave plate 216 and reaches the convex mirror 217, and after being reflected by the convex mirror 217, the P-polarized light is converted into S-polarized light through the second quarter wave plate 216. Then, after being totally reflected by the beam splitting film of the beam splitter prism, the light is totally converted into P-polarized light through the second half-wave plate 218, and finally the P-polarized light is incident to the volume hologram slab waveguide set.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a volume holographic slab waveguide set in a compact augmented reality near-to-eye device according to an embodiment of the present invention. The existing display device adopts a single-layer composite type volume holographic grating waveguide to transmit a color image, so that the problem of serious crosstalk of similar color light exists, and the embodiment adopts a multilayer single-layer composite type volume holographic grating waveguide to respectively transmit R, G, B three-color light so as to solve the problem of serious crosstalk of the similar color light. However, due to the angular selectivity of the monochromatic volume holographic grating, the brightness of the coupled-out image is too low to meet the brightness requirement of the augmented reality display device for the output image, so the coupling-in/coupling-out device of the volume holographic waveguide in this embodiment is formed by stacking two composite volume holographic gratings. The structure can effectively reuse the lost 0-level diffraction light, improve the lighting effect, realize pupil expansion, ensure the continuity and integrity of the final image and improve the light and shade stripes of the displayed image.
In this embodiment, the volume holographic slab waveguide set includes a three-layer volume holographic slab waveguide, and the wavelength selectivity of the volume holographic grating is utilized to perform diffraction transmission on red light, green light and blue light separately and couple out the red light, the green light and the blue light to the human eye for imaging, so as to reduce the chromatic dispersion and crosstalk of similar chromatic light. Each layer holographic slab waveguide includes a tunable attenuator, an incoupling/outcoupling volume holographic grating, and a slab waveguide. The adjustable attenuation sheet and the incoupling volume holographic grating are positioned on the same side of the slab waveguide and are respectively attached to the upper surface and the lower surface of the slab waveguide, and the adjustable attenuation sheet is used for adjusting the incident light intensity so that the final coupled light intensity of R, G, B three-color light is uniform and consistent.
For example, as shown in fig. 3, (a) and (b) in fig. 3 are for clearly showing the labeled content, so the label is split. The volume holographic slab waveguide group 3 comprises three layers of overlapped volume holographic slab waveguides, namely a first volume holographic slab waveguide 31, a second volume holographic slab waveguide 32 and a third volume holographic slab waveguide 33; the incoupling volume holographic grating 313 of the first volume holographic slab waveguide 31 diffracts only red light; the incoupling volume holographic grating 323 of the second volume holographic slab waveguide 32 diffracts only green light; the incoupling volume holographic grating 333 of the third volume holographic slab waveguide 33 diffracts only blue light. The in-coupling volume holographic gratings 313, 323, 333 and the out-coupling volume holographic gratings 314, 324, 334 each comprise two identical reflective volume holographic gratings that are compositely stacked on each other. Wherein the first in-coupling volume holographic grating 313 includes two identical reflective volume holographic gratings 313C1 and 313C2 that are compositely stacked with each other, it is understood that the first out-coupling volume holographic grating 314 includes 314D1 and 314D2, the second in-coupling volume holographic grating 323 includes 323C1 and 323C2, the second out-coupling volume holographic grating 324 includes 324D1 and 324D2, the third in-coupling volume holographic grating 333 includes 333C1 and 333C2, and the third out-coupling volume holographic grating 334 includes 334D1 and 334D 2. The in-coupling volume holographic gratings 313, 323, 333 are mirror symmetric to the out-coupling volume holographic gratings 314, 324, 334, respectively. The material of the waveguide plates 312, 322, 332 is transparent optical glass or transparent optical plastic.
The in-coupling volume hologram gratings 313, 323, and 333 and the out-coupling volume hologram gratings 314, 324, and 334 are multiplexed volume hologram gratings manufactured based on an angle multiplexing technique. The volume holographic grating waveguide with the two-piece composite volume holographic grating stacked structure can effectively reuse 0-order diffraction light lost by the fact that the first layer of grating 313C1 of the first incoupling volume holographic grating at the coupling end directly transmits out of the waveguide, so that the 0-order diffraction light is diffracted at the second layer of grating 313C2 of the first incoupling volume holographic grating and enters the waveguide, and the light efficiency is improved. Meanwhile, at the coupling-out end, the first layer grating 314D1 of the first coupling-out body holographic grating and the second layer grating 314D2 of the first coupling-out body holographic grating can simultaneously couple out the transmission light, so that the propagation period of the light in the optical waveguide is increased, the pupil gap of each field of view light is eliminated, pupil expansion is realized, the continuity and the integrity of the final image are ensured, and the light and dark stripes of the displayed image can be improved.
The diffraction image light which is emitted by the optical-mechanical system and carries the image information of the three-dimensional color virtual object vertically enters the first layer of grating 313C1 of the first incoupling volume holographic grating at the coupling end of the first volume holographic flat waveguide through the first adjustable attenuation sheet 311, only the negative first-order diffraction light of red light is coupled into the optical waveguide due to the wavelength selectivity of the volume holographic grating, the 0-order diffraction light of the red light is vertically incident into the second layer of grating 313C2 of the first incoupling volume holographic grating and then is diffracted, and the negative first-order diffraction light of the diffraction light is also coupled into the optical waveguide.
When the total reflection condition is satisfied, the two coupled-in diffracted lights can propagate forwards in the optical waveguide in a total reflection manner to the coupled-out volume holographic grating 314 at the coupled-out end of the first integrated holographic slab waveguide for diffraction coupling. At the coupling-out end, the first layer grating 314D1 of the first coupling-out body holographic grating and the second layer grating 314D2 of the first coupling-out body holographic grating can simultaneously couple out the transmission light, so that the propagation period of the light in the optical waveguide is increased, the pupil gap of each field of view light is eliminated, the pupil expansion is realized, the continuity and the integrity of the final image are ensured, and the bright and dark stripes of the displayed image can be improved.
Then, the diffracted image light which is filtered to remove the red light and carries the image information of the three-dimensional colorful virtual object vertically enters the first layer of grating 323C1 of the second incoupling volume holographic grating at the coupling end of the second volume holographic slab waveguide through the second adjustable attenuation sheet 321, only the negative first-order diffracted light of the green light is coupled into the optical waveguide due to the wavelength selectivity of the volume holographic grating, the 0-order diffracted light of the green light is vertically incident to the second layer of grating 323C2 of the second incoupling volume holographic grating and is diffracted, and the negative first-order diffracted light of the diffracted light is also coupled into the optical waveguide. When the total reflection condition is satisfied, the two coupled-in diffracted lights can propagate forward in the optical waveguide by total reflection to the coupled-out volume holographic grating 324 at the coupling-out end of the second volume holographic slab waveguide for diffraction coupling.
Similarly, the diffracted image light with the three-dimensional color virtual object image information, from which the red light and the green light are filtered, is vertically incident to the first grating 333C1 of the third incoupling volume holographic grating at the coupling end of the third volume holographic slab waveguide through the third adjustable attenuator 331, only the negative first-order diffracted light of the blue light is coupled into the optical waveguide due to the wavelength selectivity of the volume holographic grating, while the 0-order diffracted light of the blue light is vertically incident to the second grating 333C2 of the third incoupling volume holographic grating and is diffracted, and the negative first-order diffracted light of the diffracted light is also coupled into the optical waveguide. When the total reflection condition is satisfied, the two coupled-in diffracted lights can be propagated forward in the optical waveguide in a total reflection manner to the coupled-out volume holographic grating 334 at the coupled-out end of the third volume holographic slab waveguide for diffraction coupling. And finally, three beams of monochromatic coupled-out diffraction light enter human eyes for imaging to form a full-color image, the full-color three-dimensional virtual object image can be observed at the human eyes, and the ambient light enters the human eyes for imaging through the coupling-out device and the waveguide sheet without being influenced.
Referring to fig. 4, fig. 4 is a schematic diagram illustrating a manufacturing principle of a multi-angle multiplexed volume holographic grating based on material rotation. The embodiment of the invention provides a method for preparing a holographic grating of a multiplex volume based on the angular multiplexing technology, which is applied to the compact augmented reality near-to-eye device and comprises the following steps:
the method comprises the steps of respectively taking R, G, B monochromatic light of any one of three colors to record an angle-multiplexed volume holographic grating, keeping the positions of object light and reference light fixed during recording, obtaining different angle channels by rotating a recording material, and multiplexing and recording interference fringes in each angle channel, thus obtaining a series of angle-multiplexed volume holographic grating units in a volume holographic polymer.
During recording, in order to ensure the symmetry of the angular channel, the initial position of the material should be such that the optical axis is located on the bisector of the included angle formed by the object light and the reference light.
Assuming that the total number of interference fringes to be recorded in multiplex is n, the material should be rotated by an angle θ0And then starts angle multiplex recording.
Where Δ θminIs the minimum multiplexing angle interval. Between minimum multiplexing angles in practical applicationThe spacing is typically chosen to be greater than the Bragg angle Δ θb. Namely:
wherein L is the material thickness, lambda is the recording light wavelength, and theta is the included angle between the object light and the reference light and the optical axis during recording.
Thus, after recording a first volume holographic grating at an initial angle, the recording material is then rotated in the initial direction by delta thetaminAnd when the angle reaches a second angle channel, a second volume holographic grating can be recorded in a superposed manner at the same area of the volume holographic material, and the repeated operation can realize the multiplexing recording of the n individual holographic gratings in the same area.
And finally, respectively recording other two monochromatic lights of R, G, B three colors in the same mode to obtain corresponding angle multiplexing volume holographic gratings.
In order to ensure that the directions of interference fringe vectors of the angular multiplexing volume holographic gratings recorded by the R, G, B three-color lights in each angular channel are consistent during recording, the initial recording angle theta of each R, G, B-color light recording angular multiplexing volume holographic grating should satisfy the following condition:
λR、λG、λBrespectively R, G, B wavelengths of three color lights, thetaR、θG、θBInitial recording angles of the angle multiplexing volume hologram gratings are recorded for R, G, B three color lights, respectively.
After the recording is completed, when the diffraction image light carrying the image information of the three-dimensional color virtual object is irradiated to the multiplexed volume holographic grating, the component image information of the three-dimensional virtual object R, G, B is obtained at the multi-angle channel. Thus greatly increasing the dynamic range observed by human eyes and expanding the visual field.
The compact augmented reality near-to-eye device provided by the invention utilizes the characteristics that the self-luminous LCoS module provides high-brightness emergent light and low power consumption to design a small and high-efficiency micro-display optical system, greatly reduces the volume and weight of elements, reduces the system size, simultaneously has a more compact structure and is suitable for being worn by a human body. Meanwhile, the multiplexing volume holographic grating manufactured based on the angle multiplexing technology is used as a light coupling-in/coupling-out device to acquire three-dimensional virtual object image information at a multi-angle channel, so that the dynamic range observed by human eyes is increased, and the view field is expanded. On the other hand, because the existing display device adopts the problem of serious crosstalk of similar color light when the single-layer composite type volume holographic grating waveguide is adopted to transmit a color image, the invention adopts the multilayer single-layer composite type volume holographic grating waveguide to respectively transmit R, G, B three-color light so as to solve the problem of serious crosstalk of the similar color light. In addition, the coupling-in/coupling-out device of the volume holographic waveguide in the embodiment of the invention is formed by stacking two composite volume holographic gratings, so that the lost 0-order diffraction light can be effectively reused to improve the light efficiency when a color image is transmitted, and the technical problem that the brightness of a coupled-out image is too low due to the angle selectivity of a single-color volume holographic grating and the brightness requirement of an augmented reality display device on an output image is difficult to meet in the prior art can be solved. Meanwhile, pupil expansion can be realized, the continuity and the integrity of the final image are ensured, and the purpose of displaying light and shade stripes of the image is improved.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. A compact augmented reality near-to-eye device is characterized by comprising an LCoS module, an optical machine system and a volume holographic slab waveguide set;
the incidence surface of the optical-mechanical system is parallel to the emergent surface of the LCoS module, and the optical-mechanical system is used for receiving the light emergent from the LCoS module;
the emergent surface of the optical-mechanical system is adjacent to the upper surface of the volume holographic slab waveguide group, and the optical-mechanical system is used for converting the light emitted by the LCoS module into polarized light and then emitting the polarized light to the volume holographic slab waveguide group;
the volume holographic slab waveguide group comprises a plurality of layer volume holographic slab waveguides, and each volume holographic slab waveguide comprises an adjustable attenuation sheet, an in-coupling volume holographic grating, an out-coupling volume holographic grating and a waveguide plate; the adjustable attenuation sheet is arranged on the upper surface of the waveguide plate and is positioned at the coupling end of the volume holographic slab waveguide; the coupling-in body holographic grating and the coupling-out body holographic grating are arranged on the lower surface of the waveguide plate and are respectively positioned at the coupling-in end and the coupling-out end of the body holographic slab waveguide;
and the volume holographic flat waveguide group is used for diffracting and transmitting the polarized light and coupling out for imaging.
2. The compact augmented reality near-eye device of claim 1 further comprising an LED light source comprising R, G and a B tristimulus light source, and a controller for controlling the LED light source to rapidly time-share light R, G and the B tristimulus light source to achieve color illumination.
3. The compact augmented reality near-eye device of claim 1,
the optical-mechanical system comprises a beam splitter prism, a polarizing plate, a first half wave plate, a first quarter wave plate, a concave mirror, a second quarter wave plate, a convex mirror and a second half wave plate;
the polaroid, the concave mirror, the convex mirror and the second half-wave plate are respectively arranged on different end face sides of the beam splitter in parallel; the first half-wave plate is arranged between the polaroid and the beam splitter prism; the first quarter-wave plate is arranged between the concave mirror and the beam splitter prism; the second quarter-wave plate is arranged between the convex mirror and the beam splitter prism; the second half-wave plate is arranged between the volume holographic slab waveguide group and the beam splitter prism.
4. The compact augmented reality near-eye device of claim 3,
the first end surface of the light splitting prism parallel to the polaroid is parallel to the adjustable attenuation sheet of the volume holographic slab waveguide group;
the beam splitting prism is parallel to the second end face of the first quarter-wave plate, is parallel to the third end face of the second quarter-wave plate, and is perpendicular to the first end face.
5. The compact augmented reality near-eye device of claim 1, wherein the set of volume holographic slab waveguides comprises three overlapping layers of volume holographic slab waveguides, a first volume holographic slab waveguide, a second volume holographic slab waveguide, and a third volume holographic slab waveguide;
the incoupling volume holographic grating of the first volume holographic slab waveguide diffracts only red light; the incoupling volume holographic grating of the second volume holographic slab waveguide diffracts only green light; the incoupling volume holographic grating of the third volume holographic slab waveguide diffracts only blue light.
6. The compact augmented reality near-eye device of claim 1, wherein the in-coupling volume holographic grating and the out-coupling volume holographic grating each comprise two identical and compositely stacked reflective volume holographic gratings.
7. The compact augmented reality near-eye device of claim 1, wherein the in-coupling volume holographic grating and the out-coupling volume holographic grating are mirror symmetric.
8. The compact augmented reality near-eye device of claim 1, wherein the material of the waveguide plate is transparent optical glass or transparent optical plastic.
9. The compact augmented reality near-eye device of any one of claims 1-8, wherein the in-coupling volume holographic grating and the out-coupling volume holographic grating are multiplexed volume holographic gratings fabricated based on an angular multiplexing technique.
10. A method for preparing a multiplexed volume holographic grating based on an angle multiplexing technology, which is applied to the compact augmented reality near-to-eye device of claim 9, the method comprising:
taking any one of R, G, B three colors of monochromatic light to record a volume holographic grating with multiplexed angles;
during recording, the positions of object light and reference light are kept fixed, and different angle channels are obtained by rotating a recording material;
multiplexing and recording interference fringes in each angle channel, and obtaining a series of angle-multiplexed volume holographic grating units in a volume holographic polymer; during recording, the initial position of the material is ensured to enable the optical axis of the material to be positioned on an angle bisector of an included angle formed by object light and reference light.
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