CN115639643B - Volume holographic grating and exposure parameter determining method, manufacturing method and system thereof - Google Patents
Volume holographic grating and exposure parameter determining method, manufacturing method and system thereof Download PDFInfo
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- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
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Abstract
The invention provides a volume holographic grating and an exposure parameter determination method, a manufacturing method, a system, an optical waveguide and a display device thereof; the determining method comprises the steps of determining a first rotation angle of a vector triangle formed by a first vector, a second vector and a grating vector rotating around a rotation axis according to a total reflection critical angle, a target reflection angle when an exposure beam is totally reflected and transmitted in a volume holographic grating and a target direction angle of the exposure beam; and according to the first rotation angle, the target reflection angle and the target direction angle, obtaining a first refraction angle of the first light beam transmitted to the photosensitive material and a second refraction angle of the second light beam transmitted to the photosensitive material. The light beams are controlled through the obtained rotation angle and refraction angle to expose the photosensitive material, so that the exposure light beams are refracted into the photosensitive material to expose under a non-total reflection condition, a coupling prism is not needed in the exposure process, the defect of a double-beam interference exposure body holographic grating based on the coupling prism is avoided, and the complexity, the manufacturing difficulty and the cost of a manufacturing system are reduced.
Description
Technical Field
The embodiment of the invention relates to the technical field of optics, in particular to a volume holographic grating and an exposure parameter determining method, a manufacturing method and a system thereof.
Background
The volume holographic optical waveguide is an important display element in the field of AR display, has important advantages of low processing and manufacturing cost, feasibility of realizing large-format waveguide manufacturing and the like compared with an array optical waveguide and a relief grating optical waveguide, and is a research focus in the field of AR display at present.
The existing volume holographic optical waveguide is realized through double-beam interference exposure, wherein one exposure beam needs to meet the requirement of total reflection propagation in a waveguide substrate, and during exposure, the beam needs to be incident to a holographic photosensitive material through a coupling prism, so that the beam can be subjected to total reflection propagation in the waveguide substrate at the exposure angle during subsequent reproduction. However, this exposure method requires a coupling prism for coupling, and when the prism participates in exposure, an index matching fluid needs to be coated between the prism surface and the waveguide substrate to ensure that the light beam can be coupled into the waveguide from the prism, and the coating quality of the index matching fluid is crucial and is easily affected by dust in the air, etc., so that the matching fluid layer between the prism and the waveguide substrate has defects of non-uniform thickness, bubbles, etc., and the existence of bubbles or dust during subsequent exposure causes local defects of the volume holographic grating, thereby affecting the display quality of the volume holographic optical waveguide. In addition, when a large-size volume holographic optical waveguide needs to be manufactured, a large-size coupling prism is needed, and the processing cost of the large-size coupling prism is very high, so that the manufacturing cost of the large-size volume holographic optical waveguide is increased.
Disclosure of Invention
The embodiment of the invention aims to provide a volume holographic grating and an exposure parameter determining method, a manufacturing method, a system, an optical waveguide and display equipment thereof.
In a first aspect, an embodiment of the present invention provides a method for determining exposure parameters of a volume hologram grating, where the volume hologram grating is a reflective volume hologram grating and is manufactured by exposing a photosensitive material with an exposure beam, where the exposure beam includes a first beam and a second beam that can interfere with each other, and the method for determining the exposure parameters includes: acquiring a target reflection angle of the exposure light beam when the exposure light beam is totally reflected and propagated in the volume holographic grating, a target direction angle of the exposure light beam and a total reflection critical angle of the photosensitive material; obtaining a grating vector according to a first vector corresponding to the target reflection angle and a second vector corresponding to the target direction angle; determining a first rotation angle of a vector triangle formed by the first vector, the second vector and the grating vector rotating around a rotation axis according to the critical angle of total reflection, the target reflection angle and the target direction angle, wherein the rotation axis is a straight line which passes through the intersection point of the first vector and the second vector and is parallel to the grating vector; obtaining a first refraction angle at which the first light beam propagates to the photosensitive material and a second refraction angle at which the second light beam propagates to the photosensitive material according to the first rotation angle, the target reflection angle and the target direction angle, wherein the first refraction angle and the second refraction angle are angles of a corresponding normal of a surface of the holographic photosensitive material and a first vector and a second vector after rotation respectively, and the first refraction angle and the second refraction angle are both smaller than the critical angle of total reflection; determining the first rotation angle, the first refraction angle, and the second refraction angle as the exposure parameters.
In some embodiments, the determining a first rotation angle of a vector triangle formed by the first vector, the second vector and the grating vector around a rotation axis according to the critical angle for total reflection, the target reflection angle and the target direction angle includes: according to the geometrical relationship between the vector triangle before rotation and the vector triangle after rotation, respectively establishing a first function of the first refraction angle relative to the first rotation angle by adopting the target reflection angle and the target direction angle
And a second function ^ of the second refraction angle with respect to the first rotation angle>
Wherein is present>
Is the first angle of rotation; let the first function->
And the second function->
In which>
And obtaining the first rotation angle as the critical angle of total reflection.
In some embodiments, in the case where the target direction angle is 0 °, the first function is:
the second function is:
wherein,
for the first refraction angle->
Is the second refraction angle->
For the target reflection angle->
For the first angle of rotation, is>
Is the critical angle for total reflection.
In some embodiments, said deriving said first and second refraction angles from said first rotation angle, said target reflection angle, and said target direction angle comprises: substituting the first rotation angles into the first functions respectively
And said second function->
To obtain the secondA refractive angle and the second refractive angle.
In a second aspect, an embodiment of the present invention further provides a method for manufacturing a volume holographic grating, where the method includes: acquiring a first rotation angle, a first refraction angle, and a second refraction angle determined by the determination method of any one of the first aspect; and controlling the exposure light beam to expose the photosensitive material according to the first rotation angle, the first refraction angle and the second refraction angle to obtain the volume holographic grating.
In some embodiments, said controlling said exposure beam to expose said photosensitive material according to said first rotation angle, first refraction angle and said second refraction angle comprises: acquiring the refractive index of the photosensitive material and the normal vector of the surface of the photosensitive material; obtaining a first incident vector of the first light beam incident from air to the photosensitive material and a second incident vector of the second light beam incident from air to the photosensitive material by a three-dimensional space refraction theorem according to the first rotation angle, the first refraction angle, the second refraction angle, the refraction index and the normal vector; and controlling the first light beam and the second light beam to respectively enter from two sides of the photosensitive material for exposure according to the first incident vector and the second incident vector.
In some embodiments, the normal vector comprises a first surface normal vector, and a second surface normal vector that is opposite the first surface normal vector; the obtaining, according to the first rotation angle, the first refraction angle, the second refraction angle, the refraction index, and the normal vector, a first incident vector of the first light beam incident from air to the photosensitive material and a second incident vector of the second light beam incident from air to the photosensitive material by a three-dimensional space refraction theorem includes: rotating the first vector by the first rotation angle about the rotation axis to obtain a first refraction vector, and rotating the second vector by the first rotation angle about the rotation axis to obtain a second refraction vector; obtaining a first incident angle according to the first refraction angle and the refraction index; obtaining a second incidence angle according to the second refraction angle and the refractive index; and obtaining the first incident vector according to the first refraction vector, the first refraction angle, the refraction index and the first surface normal vector, and obtaining the second incident vector according to the second refraction vector, the second refraction angle, the refraction index and the second surface normal vector.
In some embodiments, the first incident vector
Comprises the following steps:
Said second incident vector pick>
Comprises the following steps:
(ii) a Wherein it is present>
Is the refractive index->
For a first refraction vector>
Is the second refraction vector->
Is the first surface normal vector->
Is the normal vector of the second surface,
，
，
is the magnitude of the first angle of incidence>
Is the magnitude of the second incident angle.
In some embodiments, if the target direction angle is 0 °, the first rotation angle is 90 °, and the first refraction angle is equal to the second refraction angle, before controlling the first light beam and the second light beam to enter from two sides of the photosensitive material respectively for exposure according to the first incident vector and the second incident vector, the manufacturing method further includes: obtaining the pose angle of the photosensitive material according to the first incidence angle, the target reflection angle and the refractive index; and controlling the included angle between the surface of the photosensitive material and the horizontal plane to be the pose angle so as to enable the plane formed by the first light beam and the second light beam in the air to be positioned in the horizontal plane.
In some embodiments, the pose angle
。
In a third aspect, an embodiment of the present invention further provides a system for manufacturing a volume holographic grating, where the system includes a light source, an angle determining device, and a control device; the light source is a laser light source and is used for emitting exposure beams; the angle determining apparatus is configured to perform the determining method according to any embodiment of the first aspect; the control device is used for executing the manufacturing method according to any one of the embodiments of the second aspect.
In some embodiments, the production system further comprises a pose positioning device; the pose positioning device is used for positioning the pose of the photosensitive material.
In some embodiments, the fabrication system further comprises a light splitting device; the light splitting device is used for splitting the exposure light beam into a first light beam and a second light beam and adjusting the light intensity of the first light beam and the second light beam.
In some embodiments, the fabrication system further comprises an aperture; the diaphragm is arranged between the light splitting device and the photosensitive material and is provided with two through holes.
In a fourth aspect, an embodiment of the present invention provides a volume holographic grating, which is manufactured by the manufacturing method according to any one of the second aspects.
In a fifth aspect, embodiments of the present invention provide an optical waveguide comprising a volume holographic grating as described in the fourth aspect.
In a sixth aspect, embodiments of the present invention provide a display device comprising the optical waveguide according to the fifth aspect.
Compared with the prior art, the invention has the beneficial effects that: compared with the prior art, the embodiment of the invention provides a volume holographic grating and an exposure parameter determining method, a manufacturing method, a system, an optical waveguide and a display device thereof; the determination method comprises the following steps: acquiring a target reflection angle of an exposure beam when the exposure beam is totally reflected and propagated in the volume holographic grating, a target direction angle of the exposure beam and a total reflection critical angle of a photosensitive material; determining a first rotation angle of a vector triangle formed by the first vector, the second vector and the grating vector rotating around a rotation axis according to the critical angle of total reflection, the target reflection angle and the target direction angle, wherein the rotation axis is a straight line which is parallel to the grating vector and is the intersection point of the first vector and the second vector; according to the first rotation angle, the target reflection angle and the target direction angle, a first refraction angle of the first light beam transmitted to the photosensitive material and a second refraction angle of the second light beam transmitted to the photosensitive material are obtained, the first refraction angle and the second refraction angle are respectively angles corresponding to a first vector and a second vector after rotation, and the first refraction angle and the second refraction angle are both smaller than a total reflection critical angle; the first rotation angle, the first refraction angle and the second refraction angle are determined as exposure parameters. The first light beam and the second light beam are controlled to expose the photosensitive material according to the exposure parameters obtained by the exposure parameter determining method, and the first light beam and the second light beam can be incident to the photosensitive material under the non-total reflection condition, so that a coupling prism is not required to be adopted for exposure in the manufacturing process, the respective defect problems generated when the coupling prism is adopted for exposure are avoided, the system complexity, the manufacturing difficulty and the manufacturing cost for manufacturing the volume holographic grating are reduced, and the large-format volume holographic grating is favorably manufactured.
Drawings
One or more embodiments are illustrated by the accompanying figures in the drawings that correspond thereto and are not to be construed as limiting the embodiments, wherein elements/modules and steps having the same reference numerals are represented by like elements/modules and steps, unless otherwise specified, and the drawings are not to scale.
FIG. 1 is a schematic flow chart of a method for determining exposure parameters of a volume holographic grating according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an analysis of a vector ball provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of another vector ball analysis provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating analysis of another vector ball provided by an embodiment of the present invention;
FIG. 5 is a flowchart illustrating step S300 of FIG. 1 according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating analysis of another vector ball provided by an embodiment of the present invention;
FIG. 7 is a flowchart illustrating step S400 in FIG. 1 according to an embodiment of the present invention;
FIG. 8 is a schematic flow chart of a method for fabricating a volume holographic grating according to an embodiment of the present invention;
FIG. 9 is a flowchart illustrating step S20 in FIG. 8 according to an embodiment of the present invention;
FIG. 10 is a schematic flowchart of step S22 in FIG. 9 according to an embodiment of the present invention;
FIG. 11 is a schematic diagram illustrating an analysis of a three-dimensional theorem in space according to an embodiment of the present invention;
FIG. 12 is a partial flow chart of a method for fabricating a volume holographic grating according to an embodiment of the present invention;
FIG. 13 is a schematic illustration of exposure angles for a first beam and a second beam provided by an embodiment of the present invention;
FIG. 14 is a schematic structural diagram of a system for manufacturing a volume holographic grating according to an embodiment of the present invention;
FIG. 15 is a schematic diagram of a portion of a system for fabricating a volume holographic grating according to an embodiment of the present invention;
FIG. 16 is a schematic diagram of a diaphragm provided in an embodiment of the present invention;
FIG. 17 is an elevational view of a portion of a manufacturing system in accordance with an embodiment of the present invention;
FIG. 18 is a top view of a portion of another alternative manufacturing system in accordance with an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the concept of the invention. All falling within the scope of the present invention.
To facilitate an understanding of the present application, the present application is described in more detail below with reference to the figures and the detailed description. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It should be noted that, if not conflicted, the various features of the embodiments of the invention may be combined with each other within the scope of protection of the present application. In addition, although the functional blocks are divided in the device diagram, in some cases, the blocks may be divided differently from those in the device. Further, the terms "first," "second," and the like, as used herein, do not limit the data and the execution order, but merely distinguish the same items or similar items having substantially the same functions and actions.
In a first aspect, an embodiment of the present invention provides a method for determining exposure parameters of a volume holographic grating, where the volume holographic grating is a reflective volume holographic grating and is manufactured by exposing a photosensitive material 10 with an exposure beam, where the exposure beam includes a first beam S and a second beam R that can interfere with each other, and referring to fig. 1 to 4, the method includes:
step S100: obtaining the target reflection angle of the exposure beam when the exposure beam is totally reflected and propagated in the volume holographic grating
The target direction angle of the exposure beam>
And the critical angle of total reflection of the light-sensitive material 10>
。
Specifically, the critical angle of total reflection of the photosensitive material 10
Which is a critical angle of total reflection when the light beam propagates with total reflection inside the photosensitive material 10.
Angle of reflection of target
The reflection angle is greater than or equal to the total reflection critical angle when the target beam is totally reflected and propagated in the volume holographic grating in the application process of the volume holographic grating. It should be noted that, in practical cases, the volume holographic grating is attached to the waveguide substrate to form the optical waveguide, and the refractive indexes of the waveguide substrate and the volume holographic grating are similar, so that the exposure beam is totally reflected in the waveguide substrateTarget reflection angle in reflection propagation>
Actually, the target reflection angle of the exposure beam propagating in the volume holographic grating in the total reflection mode can be->
. In the case that the refractive indexes of the waveguide substrate and the volume holographic grating cannot be considered to be the same, the target reflection angle ∑ of the exposure beam in the volume holographic grating needs to be calculated according to the refractive indexes of the waveguide substrate and the volume holographic grating and the total reflection angle of the exposure beam in the waveguide substrate>
That is, when the refractive index of the holographic photosensitive material is different from that of the waveguide substrate, it is necessary to perform calculation using the refraction theorem to determine the refraction angle refracted from the waveguide substrate into the grating or from the grating into the waveguide, and the target reflection angle ≧>
Is the angle of propagation within the holographic photosensitive material. For convenience of description and calculation and combination of practical situations, the embodiment of the invention determines the exposure parameters under the condition that the refractive indexes of the waveguide substrate and the volume holographic grating are close.
Target direction angle
For the angle at which the target beam is coupled into the volume holographic grating during the application of the volume holographic grating, i.e. the target direction angle->
The volume holographic grating can be used as an incoupling grating of an optical waveguide for coupling a target beam into a waveguide substrate of the optical waveguide and making the target beam at the refraction angle in the volume holographic grating when the target beam is coupled into the volume holographic grating from an external mediumAnd carrying out total reflection propagation in the waveguide substrate. Target direction angle->
Or the angle at which the target beam is coupled out by the volume holographic grating in the application process of the volume holographic grating, i.e. the target direction angle->
The object beam is incident on the surface of the volume holographic grating at an incident angle when the object beam is coupled out from the volume holographic grating to an external medium, and the prepared volume holographic grating can be used as an out-coupling grating of the optical waveguide, and the out-coupling grating can couple out the object beam which is subjected to total reflection propagation in the waveguide substrate from the waveguide substrate. I.e. the target direction angle>
Is the angle between the target beam in the volume holographic grating and the normal of the volume holographic grating surface in the application process. For example, the target direction angle->
The angle can be 0 degrees, namely the target beam is vertically coupled into the volume holographic grating or the target beam is vertically coupled out through the volume holographic grating; target direction angle->
It may also be around 15 deg., i.e. the object beam is tilted around 15 deg. to be coupled in or out of the volume holographic grating. Typically the external medium is air.
Note also that the exposure beam and the object beam used by the volume holographic grating during application have the same wavelength. The first light beam S and the second light beam R may be plane waves obtained by beam expansion and splitting of the same laser filter device, or plane waves with the same wavelength obtained by beam expansion of two laser filter devices, respectively, and it is sufficient to ensure that the first light beam S and the second light beam R can interfere with each other. The first beam S and the second beam R are respectively propagated into the photosensitive material 10 of the exposure beam, so that the first beam S and the second beam R interfere and form interference fringes inside the photosensitive material 10, thereby manufacturing the volume hologram grating.
The photosensitive material 10 may be one of volume hologram photosensitive materials 10 such as a photopolymer material, a silver salt material, a dichromated gelatin material, and the like. The photosensitive material 10 is typically in the form of a photosensitive film, and the corresponding volume holographic grating is also a film.
Step S200: according to the angle of reflection of the target
The corresponding first vector->
And a target direction angle>
A corresponding second vector +>
Obtaining the grating vector->
。
First vector
Is the propagation direction vector of the total reflection propagation of the target beam in the volume holographic grating, and the second vector
Is the incident or emergent direction vector of the target beam in the volume holographic grating. Wherein a raster vector->
The method is used for representing the period and the inclination angle of the volume holographic grating.
For the sake of illustration, the analysis is carried out below with the aid of K-vector spheres. Firstly, a rectangular coordinate system is established, wherein the rectangular coordinate system comprises a coordinate origin
A first, a second and a third axis perpendicular to one another and based on the wavelength lambda of the exposure beam and the refractive index of the photosensitive material 10>
Establishing a vector ball under a space rectangular coordinate system, wherein the radius of the vector ball is actually
Since the exposure beam and the target beam are the same beam, the radius of the vector sphere may be the size of the unit vector or an arbitrary length. A first axis can be +>
Shaft and/or device>
Shaft or->
Axis if the first coordinate axis is->
Axis, then the second coordinate axis may be +>
Axis, the third coordinate axis may be>
A shaft; if the first axis is->
Axis, then the second coordinate axis may be>
Axis, the third coordinate axis may be>
A shaft; if the first axis is->
Axis, then the second coordinate axis may be>
Axis, the third coordinate axis may be>
And a shaft.
Refer to FIG. 2 for the following description
Is taken as a coordinate origin, a first coordinate axis is +>
Axis, a second axis being->
Axis with a third axis being >>
The shaft is specifically described as an example. The photosensitive material 10 is located in->
In the plane, the normal to the light-sensitive material 10 is in the direction->
Axis, exposure beam is situated->
In the plane, based on the target reflection angle>
A first vector may be obtained>
Target reflection angle->
Is the first vector->
The first vector->
The light beam vector is a light beam vector of the total reflection propagation of a target light beam in the volume holographic grating or the optical waveguide in the application process of the volume holographic grating. Based on the target direction angle->
A second vector can be obtained
Target direction angle->
I.e. the second vector->
Is the second vector->
Either the refracted light vector when the object beam is coupled into the volume holographic grating or the incident light vector when the object beam is coupled out of the volume holographic grating. Then a first vector may be found>
And a second vector->
In a vector difference of (4), i.e. a raster vector &>
. Wherein a first vector +>
The included angle between the normal direction of the photosensitive material 10 and the normal direction is the target reflection angle>
Second vector +>
The included angle between the normal direction of the photosensitive material 10 and the normal direction is the target direction angle>
. In one embodiment, the target direction angle>
Is 0 deg., the second vector is->
And &>
The positive directions of the axes coincide.
Step S300: according to the critical angle of total reflection
Target reflection angle>
And a target direction angle>
Determining a first vector
A second vector +>
And a grating vector->
The formed vector triangle->
A first angle of rotation about an axis of rotation which is a first vector +>
And a second vector +>
And the intersection point of (a) and the raster vector->
Parallel straight lines.
Specifically, referring to fig. 2, under the same light beam condition, the angular selectivity of the volume holographic grating is related to the tilt angle of the grating, i.e. the direction of the grating vector. The volume holographic grating corresponding to the grating vectors in the same direction can diffract the light beams with the same incident angle, and in the embodiment, the vector triangle is rotated around the rotation axis, so that during the rotation process of the vector triangle, on one hand, the rotated grating vectors are parallel to the initial grating vectors, and on the other hand, the rotated first vectors are parallel to the initial grating vectors
And a second vector->
Is not changed, i.e. the first vector->
The second vector->
And raster vector +>
Formed vector triangle>
Bypassing coordinate axis zero point>
And with the raster vector->
The parallel axis of rotation m rotates so that the first rotated vector is taken into use>
And a second vector->
The grating formed by the exposure is compared with the first vector->
And a second vector->
The gratings formed by the exposures are identical. />
For convenience of description and understanding, please refer to fig. 2 and 3 in combination, in the rectangular coordinate system, the vector is triangular
Before rotating about the axis of rotation, the photosensitive material 10 can be wound round>
The shaft stands at a second angle of rotation>
Rotate to make the grating vector
Parallel to>
Shaft whereby the rotation shaft m becomes>
The shaft, the first vector after rotation is also->
The second vector after rotation is also
Rotated raster vector, i.e. [ MEANS ]>
First vector +>
The second vector->
And a grating vector->
The formed vector triangle is->
. Wherein the second angle of rotation->
Is a grating vector +>
And/or>
The angle between the axes is in degrees. Then, if the target direction angle
Is 0 deg., is rotated by a second rotation angle>
Then, a second vector->
And &>
The positive direction of the shaft has an included angle of->
The first vector->
And
the positive direction of the shaft has an included angle of->
I.e. the first vector->
And/or>
The negative direction of the shaft has an included angle of->
Due to the grating vector->
Is parallel to>
Shaft, thatThen, is based on>
I.e. is present>
. For the purposes of the present description, in the following text the target direction angle->
Is 0 deg., and the raster vector->
Is parallel to>
The axes are explained on the premise that the parameters are calculated after the angle relation between each vector before and after rotation is determined according to the actual angle of the target direction angle and the actual position of the vector triangle.
Please refer to fig. 3 and fig. 4 in combination, let the vector triangle
Winding/combining device>
The shaft (rotation shaft) is rotated over a first angle of rotation>
Then, the rotated vector triangle->
I.e. vector triangle>
And the rotated first vector +>
I.e. the first refraction vector->
And also the rotated second vector->
I.e. the second refraction vector->
And the first refraction vector +>
And &>
The angle in the positive direction of the axis equals a first vector +>
And/or>
The positive direction angle of the shaft is->
Second refraction vector +>
And/or>
The angle in the positive direction of the shaft equals the second vector pick>
And/or>
The positive direction angle of the shaft is->
。
In addition, in vector triangles
Middle, vector->
And the grating vector->
Exactly equivalent, i.e. the magnitude and direction of the grating vector are exactly the same, i.e. the first light beam S according to the first refraction vector->
The second light beam R is according to a second refraction vector
The volume holographic grating obtained by exposing the photosensitive material 10 can make the first light beam S according to the first vector->
The second light beam R according to a second vector->
Propagating through the photosensitive material 10. Wherein the first refraction vector->
A first refraction angle for the propagation direction vector of the first light beam S inside the photosensitive material 10>
Is the first refraction vector->
The angle between the first surface of the photosensitive material 10 and the normal direction of the first surface, wherein the first surface is the surface of the photosensitive material on which the first light beam is incidentThe second refraction vector->
The second refraction angle->
Is the second refraction vector->
And an angle with a normal direction of a second face of the photosensitive material 10 opposite to the first face, wherein the second face is a face on which the second light beam is incident. Then, at the vector triangle->
Winding/judging unit>
During the rotation of the shaft, a suitable first angle of rotation ∑ can be found>
Make the first refraction vector &>
And a second refraction vector +>
It suffices that a condition, i.e. the first refraction angle->
And a second folding angle->
Are all less than the total reflection critical angle>
In this way, the angle of refraction can be subsequently adjusted according to the corresponding angle of refractionDuring line exposure, a coupling prism is not needed to participate in exposure, and the defects generated by exposure of the holographic grating of the volume body through the coupling prism are avoided.
Step S400: according to the first rotation angle
Target reflection angle>
And a target direction angle>
A first refraction angle is obtained at which the first light beam S propagates to the photosensitive material 10>
And a second refraction angle at which the second light beam R propagates to the photosensitive material 10>
First refraction angle->
And a second folding angle->
Respectively the first vector after rotation->
And a second vector +>
Corresponding angle, first refraction angle->
In conjunction with a second folding angle>
Are all less than a critical angle for total reflection>
。
From the foregoing, it can be seen that when the first rotation angle is selected to be suitable
Then, the corresponding first refraction vector ^ is obtained>
And a second refraction vector +>
That the first refraction angle is also available>
And a second folding angle->
。
Step S500: will be the first rotation angle
The first refraction angle->
And a second folding angle->
Determined as exposure parameters.
It can be seen that, under the condition that the exposure beam is the same as the target beam, the exposure parameter obtained by the determination method is utilized to control the first beam S and the second beam R to expose the photosensitive material 10 according to the exposure parameter, and both the first beam S and the second beam R can be incident to the photosensitive material 10 under the non-total reflection condition, so that a coupling prism is not needed to participate in exposure in the manufacturing process, the problems generated when the coupling prism is used for exposure are avoided, the system complexity, the manufacturing difficulty and the manufacturing cost of manufacturing the volume holographic grating are reduced, and the manufacturing of the volume holographic grating with a large breadth is facilitated.
In some embodiments, vector triangles may be recorded by way of model simulation
During a revolution around the axis of rotation, a first angle of rotation->
The first refraction angle->
And a second folding angle +>
A curve is formed by which a first refraction angle can subsequently be selected>
And a second folding angle->
Are all less than the total reflection critical angle>
In a first angle of rotation>
。
In some embodiments, referring to fig. 5, step S300 includes:
step S310: from vector triangles before rotation
And the rotated vector triangle->
In accordance with a geometric relationship between, using a target reflection angle>
Target direction angle>
Respectively establish a first refraction angle->
In relation to the first angle of rotation>
Is greater than or equal to>
And a second refraction angle->
In relation to the first angle of rotation>
Is greater than or equal to>
。
Step S320: let a first function
And a second function->
Wherein is present>
For a total reflection critical angle, a first angle of rotation is determined>
。
In order to reduce the amount of calculation, in the present embodiment, the first refraction angle is established by using the geometric relationship between vector triangles before and after rotation
Is reflected by the target>
The target direction angle->
And a first angle of rotation>
Is a first function->
(ii) a And a second folding angle->
Is reflected by the target>
The target direction angle->
And a first angle of rotation>
Is a second function->
And finally the first function is asserted>
A second function->
Are all less than the total reflection criticalCorner
And the target reflection angle->
The target direction angle->
Are known, so that a first angle of rotation->
. It should be noted that a set of first rotation angles is obtained by solving the inequality equation, and any one of the first rotation angles can be selected from the set of first rotation angles as the first rotation angle £ or £ r obtained in the present embodiment>
。
It can be seen that in the present embodiment, the first function is established
And a second function>
The first angle of rotation can be solved>
。
In some of these embodiments, where the target azimuth angle is 0 °, the first function is:
the second function is:
wherein,
for a first refraction angle>
Is the second refraction angle>
Is the target reflection angle>
Is a first angle of rotation>
The critical angle for total reflection.
Specifically, please refer to FIG. 6, but
Point direction->
Make a perpendicular bisector and combine with>
In a point of intersection of >>
Over/based on>
Point direction->
Make the perpendicular bisector and combine with>
Has a crossing point of->
. The first angle of rotation beta is then->
I.e. the vector triangle->
The plane and the vector triangle->
The included angle between the planes. Then, it is taken into consideration>
、
And &>
Parallel and equal in a triangle
The method comprises the following steps:
and the following steps:
then there are:
in a triangle
In (1), the following can be obtained:
thus, there are:
vector
Winding/judging unit>
The diameter of the circle formed by the intersection of the axis rotation and the vector sphere is:
in a right triangle
The method comprises the following steps:
in a triangle
In (1), the following can be obtained:
thus, there are:
wherein,
is the second refraction angle->
，
Is the first refraction angle->
And also->
Then, the first function is:
the second function is:
it can be seen that in the present embodiment, the first function can be obtained by using the geometric relationship
And a second function>
Subsequently both are smaller than the total reflection critical angle>
So that the desired first angle of rotation is obtained>
. Although the functional expression in the present embodiment is established when the target direction angle is 0 °, when the target direction angle is not 0 °, the target direction angle may be added to the functional expression according to a geometric relationship in an actual situation, or the first refraction angle and the second refraction angle may be obtained by subtracting the target direction angle from the solved angle by the functional expression in the present embodiment.
In some embodiments, referring to fig. 7, step S400 includes:
step S410: will be the first rotation angle
Respectively into the first function->
And a second function>
Obtaining a first refraction angle->
And a second folding angle +>
。
From the aforementioned first function
And a second function>
Is obtained when the first angle of rotation->
The first angle of rotation can be greater or smaller>
Target reflection angle>
The target direction angle->
Respectively into the first function->
And a second function
In that a first refraction angle is determined>
And a second folding angle->
。
In one embodiment, if the target direction angle is 0 °, the first refraction angle may be set to be symmetrical with respect to the photosensitive material 10 when the first light beam S and the second light beam R are incident on the photosensitive material 10
Is equal to the second refraction angle +>
Namely:
then there are:
the following can be found:
and also
Then:
i.e. at a target orientation angle of 0 deg., the first rotation angle
At 90 DEG, a first refraction angle>
Is equal to the second refraction angle +>
The vector triangle is>
Located in +>
In-plane.
In a second aspect, an embodiment of the present invention further provides a method for manufacturing a volume holographic grating, please refer to fig. 8, where the method includes:
step S10: acquiring the first rotation angle determined by the determination method of any one of the first aspect
The first refraction angle->
And a second folding angle->
；
Step S20: according to the first rotation angle
First refraction angle->
And a second folding angle->
And controlling the exposure light beam to expose the photosensitive material 10 to obtain the volume holographic grating.
The determining method described in this embodiment has the same steps and functions as the determining method of the exposure parameters of the volume holographic grating described in any embodiment of the first aspect, and is not described herein again. Determining a first refraction angle corresponding to the first light beam S according to the method for determining exposure parameters described in any embodiment of the first aspect
A second refraction angle corresponding to the second light beam R>
And a first angle of rotation>
Thereafter, the first and second light beams S and R can be controlled to expose the photosensitive material 10, wherein the first and second light beams S and R in the photosensitive material are rotated by a first rotation angle ^>
On the rear plane, the grating vector of the manufactured volume holographic grating is the same as that of the target beam, and the coupling prism is not required to be used for exposure, so that the defects caused by exposure of the coupling prism are avoided, the complexity, the manufacturing difficulty and the manufacturing cost of a system for manufacturing the volume holographic grating are reduced, the large-size volume holographic grating is favorably manufactured, and the large-size volume holographic grating is subsequently applied to volume holographic waveguides and target beamsIn the display device, the difficulty and cost of manufacturing the volume holographic waveguide and the display device are also reduced.
In some embodiments, referring to fig. 9, step S20 includes:
step S21: obtaining the refractive index of the photosensitive material 10
And the normal vector of the surface of the light-sensitive material 10->
；
Step S22: according to the first rotation angle
The first refraction angle->
And a second folding angle->
Refractive index->
And the normal vector
A first incident vector which is formed by the refraction theorem in the three-dimensional space and is incident on the photosensitive material 10 from the air in the first light beam S is obtained>
And a second incident vector for the second light beam R to be incident on the photosensitive material 10 from the air>
；
Step S23: according to the first incident vector
And a second incident vector->
The first beam S and the second beam R are controlled to be incident from both sides of the photosensitive material 10, respectively, for exposure.
In the present embodiment, in obtaining the refractive index of the photosensitive material 10, the normal vector of the surface of the photosensitive material 10
First angle of rotation>
First refraction angle->
And a double refraction angle->
A first incoming vector can be found>
And a second incident vector->
May subsequently be based on the first incident vector->
And a second incident vector->
The direction of the first beam S and the second beam R incident on the photosensitive material 10 is controlled, so that the photosensitive material 10 is exposed to produce the desired volume holographic grating.
In some of these embodiments, the normal vector
Comprising a first surface normal vector->
And a normal vector based on the first surface>
An inverted second surface normal vector->
Wherein the first surface normal vector corresponds to the first side of the photosensitive material 10 and the second surface normal vector corresponds to the second side of the photosensitive material 10; referring to fig. 10, step S22 includes:
step S221: the first vector is divided into
Rotates about the axis of rotation by a first angle of rotation>
Obtaining a first refraction vector->
The second vector is->
Rotates about the axis of rotation by a first angle of rotation>
Obtaining a second refraction vector->
；
Step S222: according to the first refraction angle
And a refractive index->
Obtaining a first angle of incidence>
；
Step S223: according to the second refraction angle
And a refractive index->
Obtaining a second angle of incidence>
；
Step S224: according to a first refraction vector
The first refraction angle->
Refractive index->
And a first surface normal vector->
Obtaining a first incident vector->
Based on the second refraction vector->
Second folding angle->
In or on the refractive index>
And a second surface normal vector
Obtaining a second incident vector->
。
First, according to the law of refraction, one obtains
，
In which>
Is based on the magnitude of the first angle of incidence>
Is the magnitude of the second angle of incidence.
Referring to FIG. 11, for a beam of light in space, if the incident light vector is
The normal vector of the surface of the light-sensitive material 10 is->
The transmission vector of the beam of light after being incident to the photosensitive material 10 from the external medium is->
，
Is the size of the included angle between the incident light and the normal line>
The angle between the refracted light and the normal is, then, from the three-dimensional space refraction theorem, the following is obtained:
wherein,
is the refractive index of the external medium, then the incident light vector is:
then, the first incident vector
Comprises the following steps:
second incident vector
Comprises the following steps:
wherein, due to the external mediumThe substance of the air is air, and the air is air,
then>
Is the refractive index->
，
Is the first refraction vector, is>
For the second refraction vector +>
For a first surface normal vector +>
Is the second surface normal vector.
Thus, in this embodiment, the first incident vector can be obtained according to the three-dimensional refraction theorem
And a second incident vector->
。
To facilitate the light path setup of the exposure beam, in some embodiments, if the target direction angle is 0 °, the first rotation angle
At 90 DEG, a first refraction angle->
Equals a second refraction angle>
Before step S23, please refer to fig. 12, the manufacturing method further includes:
step S11: according to a first incident angle
The target reflection angle->
And a refractive index->
Obtaining the pose angle of the photosensitive material 10;
step S12: and controlling the included angle between the surface of the photosensitive material 10 and the horizontal plane as a pose angle so that the plane formed by the first light beam S and the second light beam R in the air is positioned in the horizontal plane.
Wherein the plane formed by the first light beam S and the second light beam R in the air is positioned in the horizontal plane, namely the first incident vector
And a second incident vector->
Are all positioned on the horizontal plane, this makes it possible to order ^ er/be when a rectangular coordinate system is established>
Axis is perpendicular to the real horizontal plane, then plane>
Is a horizontal plane.
Specifically, as shown in FIG. 3, the photosensitive material 10 may be first placed in a plane
The normal line of the photosensitive material 10 is->
In the axial direction, the surface and the plane of the photosensitive material 10 are then combined>
Is a second angle of rotation->
I.e. winding of the photosensitive material 10
Shaft rotation over a second angle of rotation->
Referring now to FIG. 2, in this case, referring to FIG. 6, the triangle is based on>
Winding/judging unit>
After the axis has been rotated by 90 °, the coordinates of each vector represent:
then, according to the three-dimensional space refraction theorem, there are:
from a first incident vector
And a second incident vector->
The expression (4) indicates that the plane formed by the two vectors is not parallel to the plane->
And both are in->
The component of the axis satisfies the symmetry relation at>
Component of the axis satisfies a symmetry relationship>
The same axial component, then the first incident vector may be asserted>
And a second incident vector->
Continuously winding and collecting>
Shaft rotation over a third angle of rotation->
I.e. letting the photosensitive material continue to wind>
Shaft rotation over a third angle of rotation->
Let the rotated first incidence vector ^ be ^ s>
Comprises the following steps:
setting the rotated second incident vector
Comprises the following steps:
in order to let the rotated first incident vector
And the rotated second incidence vector +>
Are all in the plane>
Make two vectors in->
The component of the axis is 0, resulting in:
namely:
that is, the photosensitive material continues to be wound
The shaft is rotated over the third angle of rotation->
Then, the first incident vector->
And a second incident vector->
The formed plane is in the plane>
I.e. the plane formed by the first light beam S and the second light beam R lies in the plane->
And as shown in FIG. 13, the first light beam R and the second light beam S are incident on the photosensitive material 10 in a manner corresponding to +>
Axisymmetric, second beam R and->
The included angle of the axial positive direction is as follows:
first light beam R and
the included angle eta 2= -eta 1 of the axial positive direction.
It is seen that after exposureIn the process, the surface of the photosensitive material 10 can be controlled to be in a plane
And the photosensitive material 10 is wound and/or stored first>
Shaft rotation over a second angle of rotation->
Then rewound->
Shaft rotation over a third angle of rotation->
By winding the photosensitive material 10>
Shaft rotation pose angle->
At this time, the photosensitive material 10 is on the surface to be clamped, and the position and orientation positioning device is subsequently utilized to clamp the photosensitive material 10 on the surface to be clamped, so that the plane formed by the first light beam S and the second light beam R in the air is positioned on the horizontal plane->
And in addition, the light path is convenient to build, and the manufacturing difficulty is reduced.
In a third aspect, an embodiment of the present invention further provides a system for manufacturing a volume holographic grating, where the system includes a light source 21, an angle determining device, and a control device. The light source 21 is a laser light source for emitting an exposure beam; the angle determining means is configured to perform the exposure parameter determining method according to any one of the embodiments of the first aspect; the control device is used for executing the manufacturing method of any one of the embodiments of the second aspect.
Wherein the light source 21 may be a laser. In this embodiment, the exposure parameter determining method has the same steps and functions as the exposure parameter determining method according to the first aspect, and the manufacturing method has the same steps and functions as the manufacturing method according to the second aspect, and therefore, the description thereof is omitted. In the manufacturing system, the exposure parameters are determined by the angle determining device, and the control device can control the light beams according to the exposure parameters and adjust the directions of the first light beam S and the second light beam R, thereby manufacturing the volume holographic grating of the light beam corresponding to the diffraction target wavelength.
In some of these embodiments, the production system further comprises a pose positioning device; the pose positioning means is used to position the pose of the photosensitive material 10. Specifically, referring to fig. 14, the pose positioning apparatus may include a clamping device 31, and the clamping device 31 may be a rotatable clamp, for example, and may clamp the photosensitive material 10 and then drive the photosensitive material 10 to rotate to a surface to be clamped, so that a plane formed by the first light beam S and the second light beam R in the air is located in a horizontal plane. For another example, the clamping device 31 may also be a dry plate clamp, which has a fixed structure and a movable structure, and when the photosensitive material 10 is placed in the dry plate clamp, the movable structure is screwed down and clamps the photosensitive material 10 together with the fixed structure. In practical applications, the specific structure of the position and orientation positioning device need not be limited in this embodiment, and may be any suitable position and orientation positioning device in the prior art.
In some of these embodiments, the fabrication system further comprises a light splitting device; the beam splitting device is used for splitting the exposure beam into a first beam S and a second beam R and adjusting the light intensity of the first beam S and the second beam R.
Specifically, referring to fig. 14, the light splitting device includes a first polarization beam splitter prism 23 and a second polarization beam splitter prism 25, and the light source device 21, the first polarization beam splitter prism 23 and the second polarization beam splitter prism 25 are sequentially arranged along a first direction, such as
The axes are arranged such that the exposure beam from the light source device 21 can be divided into a first beam S and a second beam R by passing through the first polarization beam splitter prism 23 and the second polarization beam splitter prism 25, respectively, and adjustedThe transmittance-reflectance ratio of the polarization beam splitting film can adjust the light intensity of the first light beam S and the second light beam R. In one embodiment, the beam splitting device may also be a beam splitting prism that splits the exposure light beam emitted by the light source device 21 into the first light beam S and the second light beam R.
In some embodiments, referring to fig. 14, the light splitting device further includes a first half-wave plate 22 and a second half-wave plate 24, wherein the first half-wave plate 22 is disposed between the light source device 21 and the first polarization splitting prism 23, the second half-wave plate 24 is disposed between the first polarization splitting prism 23 and the second polarization splitting prism 25, and the first half-wave plate 22 and the second half-wave plate 24 can be used to adjust the polarization state and transmittance of the light beam, so as to further adjust the intensity of the first light beam S and the second light beam R.
In order to adjust the optical path conveniently, in some embodiments, referring to fig. 14, the light splitting device further includes a reflecting mirror 26 and a reflecting mirror 27, the reflecting mirror 26 is configured to reflect the light beam reflected by the second polarization beam splitter 25 to the photosensitive material 10, the reflecting mirror 27 is configured to reflect the light beam reflected by the first polarization beam splitter 23 to the photosensitive material 10, and by arranging the reflecting mirror 26 and the reflecting mirror 27, the propagation directions of the first light beam S and the second light beam R can be adjusted, so that the first light beam S and the second light beam R expose the photosensitive material 10 according to the exposure parameters. In practical applications, the number of the reflecting mirrors may be set according to actual needs, and is not limited herein.
In some embodiments, referring to fig. 15, the manufacturing system further includes a diaphragm 90; the diaphragm 90 is arranged between the light splitting device and the photosensitive material 10, and the diaphragm 90 is provided with two through holes.
Specifically, as shown in fig. 15, the manufacturing system includes two diaphragms 90, and the two diaphragms 90 are respectively attached to two surfaces of the photosensitive material 10. Referring to fig. 16, the two diaphragms are provided with through holes 91 and 92, and the through holes 91 and 92 are identical in position and size, so that when the diaphragms are subsequently used for exposure, an incoupling grating and an outcoupling grating can be simultaneously formed on the photosensitive material 10, and the one-dimensional pupil-expanding volume holographic optical waveguide can be formed by one-time exposure. It can be seen that in this embodiment, the stop can be used to simultaneously make the incoupling grating and the outcoupling grating.
In some embodiments, referring to fig. 17, the manufacturing system device further includes a first prism 32 and a second prism 33. Among them, the first prism 32 and the second prism 33 may be used to assist the holding device 31 in holding the photosensitive material 10. Specifically, the photosensitive material 10 is wound
Shaft rotation pose angle->
After reaching the surface to be clamped, the surface S of the first prism 32 is arranged 1 Surface S for bonding the surface to be clamped and the second prism 33 3 The surface to be clamped is attached to fix the photosensitive material 10, then the photosensitive material 10 is clamped by the clamping device 31, and the first prism 32 and the second prism 33 are removed.
Referring to FIG. 18, before exposure, the surface S of the first prism 32 2 And surface S of second prism 33 4 The incident directions of the first light beam S and the second light beam R can be quickly adjusted by matching with devices such as a diaphragm and the like. Specifically, the surface S of the first prism 32 is set 2 Flour with S 5 The included angle is eta 1, and the second light beam R is perpendicular to the incident surface S 2 On the surface S adjacent to the first prism 32 2 A diaphragm is arranged at the position of (2), and the second light beam R enters the surface S of the first prism 32 after passing through the diaphragm 2 If the second light beam R is perpendicularly incident to the surface S of the first prism 32 2 The reflected light of the second light beam R generated on the first prism 32 and the air surface returns to the same point of the diaphragm along the original optical path, and if the second light beam R is not vertically incident on the surface S of the first prism 32 2 And part of reflected light is separated from the incident light of the opening of the diaphragm, so that whether the second light beam R is vertically incident or not can be judged, the incident direction of the subsequent second light beam R is convenient, and the manufacturing difficulty is reduced. Similarly, let the surface S of the second prism 33 4 Flour S 6 The included angle is eta 1, and the first light beam S is perpendicular to the incident plane S 4 On the surface S adjacent to the second prism 33 4 A diaphragm is arranged at the position of the diaphragm,the first light beam S passes through the diaphragm and is incident on the surface S of the second prism 33 4 If the first light beam S is perpendicularly incident to the surface S of the second prism 33 4 The reflected light of the first light beam S generated on the second prism 33 and the air surface will return to the same point of the diaphragm along the original optical path, if the first light beam S is not vertically incident on the surface S of the second prism 33 4 And part of the reflected light is separated from the incident light of the opening of the diaphragm, so that whether the first light beam S is vertically incident or not can be judged, the incident direction of the subsequent first light beam S is convenient, and the manufacturing difficulty is reduced.
In some embodiments, referring to fig. 14, the manufacturing system further includes an isolator 70, and the isolator 70 is used for absorbing the light beam transmitted through the second polarization splitting prism 25.
In some embodiments, referring to fig. 14, the manufacturing system further includes a microscope objective 41, a microscope objective 42, a pinhole filter 51 and a pinhole filter 52, the microscope objective 41 and the microscope objective 42 can be used for focusing the first light beam S and the second light beam R, and the pinhole filter 51 can be used for expanding the first light beam S and the second light beam R.
In some embodiments, referring to fig. 14, the manufacturing system further includes a collimating lens 61 and a collimating lens 62, and the collimating lens 61 and the collimating lens 62 are arranged to collimate the first light beam S and the second light beam R.
In a fourth aspect, embodiments of the present invention provide a volume holographic grating, which is manufactured by the manufacturing method of any one of the second aspects. The manufacturing method in this embodiment has the same steps and functions as the manufacturing method described in the second aspect, and is not described herein again. In the exposure process, the wavelength of the exposure light beam and the wavelength of the light beam corresponding to the photosensitive material 10 can be selected as required, specifically, manufacturing systems can be designed for red, green and blue respectively, so that three-color volume holographic gratings can be manufactured, and the volume holographic optical waveguide capable of realizing full-color display can be formed by subsequent combination.
In a fifth aspect, embodiments of the present invention provide an optical waveguide comprising a volume holographic grating as in the fourth aspect. In this embodiment, the volume holographic grating has the same structure and function as the volume holographic grating described in any one of the fourth aspects, and is not described herein again.
In a sixth aspect, embodiments of the present invention provide a display device comprising an optical waveguide as in the fifth aspect. In this embodiment, the display device has the same structure and function as the display device according to any one of the fifth aspects, and details are not repeated here. The display device may be a head-up display (HUD) device, or may be a near-eye display device, such as AR glasses, AR helmet, or the like.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a general hardware platform, and certainly can also be implemented by hardware. Based on the understanding, the above technical solutions substantially or otherwise contributing to the related art may be embodied in the form of a software product, which may be stored in a computer-readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions for executing the method according to each embodiment or some parts of the embodiments by at least one computer device (which may be a personal computer, a server, or a network device, etc.).
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (17)
1. A method for determining exposure parameters of a volume holographic grating is characterized in that the volume holographic grating is a reflection-type volume holographic grating and is prepared by exposing a photosensitive material by using exposure beams, wherein the exposure beams comprise a first beam and a second beam which can generate interference, and the determining method comprises the following steps:
acquiring a target reflection angle of the exposure light beam when the exposure light beam is totally reflected and propagated in the volume holographic grating, a target direction angle of the exposure light beam and a total reflection critical angle of the photosensitive material;
obtaining a grating vector according to a first vector corresponding to the target reflection angle and a second vector corresponding to the target direction angle;
determining a first rotation angle of a vector triangle formed by the first vector, the second vector and the grating vector rotating around a rotation axis according to the critical angle of total reflection, the target reflection angle and the target direction angle, wherein the rotation axis is a straight line which passes through the intersection point of the first vector and the second vector and is parallel to the grating vector;
obtaining a first refraction angle at which the first light beam propagates to the photosensitive material and a second refraction angle at which the second light beam propagates to the photosensitive material according to the first rotation angle, the target reflection angle and the target direction angle, wherein the first refraction angle and the second refraction angle are angles of a corresponding normal of a rotated first vector and a rotated second vector and a holographic photosensitive material surface respectively, and the first refraction angle and the second refraction angle are both smaller than the critical angle of total reflection;
determining the first rotation angle, the first refraction angle, and the second refraction angle as the exposure parameters.
2. The method according to claim 1, wherein determining a first rotation angle by which a vector triangle formed by the first vector, the second vector, and the grating vector is rotated around a rotation axis, based on the critical angle for total reflection, the target reflection angle, and the target direction angle, comprises:
according to the geometric relation between the vector triangle before rotation and the vector triangle after rotation, respectively establishing a first function of the first refraction angle relative to the first rotation angle by adopting the target reflection angle and the target direction angle
And a second function +of the second refraction angle in relation to the first rotation angle>
Wherein is present>
At the first angle of rotation;
let the first function
And the second function->
Wherein is present>
And obtaining the first rotation angle for the critical angle of total reflection.
3. The determination method according to claim 2, wherein in the case where the target direction angle is 0 °, the first function is:
the second function is:
wherein,
for the first refraction angle->
Is the second refraction angle->
For the target reflection angle->
For the first angle of rotation, is>
Is the critical angle for total reflection.
4. The determination method according to claim 2, wherein the deriving the first and second refraction angles from the first rotation angle, the target reflection angle, and the target direction angle includes:
substituting the first rotation angles into the first functions, respectively
And said second function->
And obtaining the first refraction angle and the second refraction angle.
5. A method for making a volume holographic grating, comprising:
acquiring a first rotation angle, a first refraction angle and a second refraction angle determined by the determination method according to any one of claims 1 to 4;
and controlling the exposure light beam to expose the photosensitive material according to the first rotation angle, the first refraction angle and the second refraction angle to obtain the volume holographic grating.
6. The manufacturing method according to claim 5, wherein the controlling the exposure beam to expose the photosensitive material according to the first rotation angle, the first refraction angle, and the second refraction angle includes:
acquiring the refractive index of the photosensitive material and the normal vector of the surface of the photosensitive material;
obtaining a first incident vector of the first light beam incident from air to the photosensitive material and a second incident vector of the second light beam incident from air to the photosensitive material by a three-dimensional space refraction theorem according to the first rotation angle, the first refraction angle, the second refraction angle, the refraction index and the normal vector;
and controlling the first light beam and the second light beam to respectively enter from two sides of the photosensitive material for exposure according to the first incident vector and the second incident vector.
7. The method of manufacturing according to claim 6,
the normal vector comprises a first surface normal vector and a second surface normal vector opposite to the first surface normal vector;
the obtaining, by a three-dimensional spatial refraction theorem, a first incident vector of the first light beam incident from air to the photosensitive material and a second incident vector of the second light beam incident from air to the photosensitive material according to the first rotation angle, the first refraction angle, the second refraction angle, the refraction index, and the normal vector, includes:
rotating the first vector by the first rotation angle about the rotation axis to obtain a first refraction vector, and rotating the second vector by the first rotation angle about the rotation axis to obtain a second refraction vector;
obtaining a first incident angle according to the first refraction angle and the refraction index;
obtaining a second incidence angle according to the second refraction angle and the refractive index;
and obtaining the first incident vector according to the first refraction vector, the first refraction angle, the refraction index and the first surface normal vector, and obtaining the second incident vector according to the second refraction vector, the second refraction angle, the refraction index and the second surface normal vector.
8. The method of manufacturing according to claim 7,
the first incident vector
Comprises the following steps:
Said second incident vector pick>
Comprises the following steps:
；
wherein,
is the refractive index->
Is the first refraction vector, is>
Is the second refraction vector->
Is the normal vector of the first surface,
is the second surface normal vector +>
，
，
Is the magnitude of the first angle of incidence>
Is the magnitude of the second incident angle. />
9. The manufacturing method according to claim 7, wherein if the target direction angle is 0 °, the first rotation angle is 90 °, and the first refraction angle is equal to the second refraction angle, before controlling the first light beam and the second light beam to be incident from both sides of the photosensitive material respectively for exposure according to the first incident vector and the second incident vector, the manufacturing method further comprises:
obtaining the pose angle of the photosensitive material according to the first incident angle, the target reflection angle and the refractive index;
and controlling the included angle between the surface of the photosensitive material and the horizontal plane to be the pose angle so as to enable the plane formed by the first light beam and the second light beam in the air to be positioned in the horizontal plane.
10. The method of manufacturing according to claim 9, wherein the pose angle
。
11. A system for manufacturing volume holographic grating is characterized by comprising a light source, an angle determining device and a control device;
the light source is a laser light source and is used for emitting exposure beams;
the angle determination means is used for executing the determination method according to any one of claims 1 to 4;
the control device is used for executing the manufacturing method of any one of claims 5-10.
12. The production system of claim 11, further comprising a pose positioning device;
the pose positioning device is used for positioning the pose of the photosensitive material.
13. The fabrication system of claim 11, further comprising a light splitting device;
the light splitting device is used for splitting the exposure light beam into a first light beam and a second light beam and adjusting the light intensity of the first light beam and the second light beam.
14. The production system of claim 13, further comprising an aperture;
the diaphragm is arranged between the light splitting device and the photosensitive material and is provided with two through holes.
15. A volume holographic grating, wherein the volume holographic grating is produced by the production method according to any one of claims 5 to 10.
16. An optical waveguide comprising the volume holographic grating of claim 15.
17. A display device comprising the light guide of claim 16.
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| CN202211660955.0A CN115639643B (en) | 2022-12-23 | 2022-12-23 | Volume holographic grating and exposure parameter determining method, manufacturing method and system thereof |
| PCT/CN2023/083114 WO2024130873A1 (en) | 2022-12-23 | 2023-03-22 | Volume holographic grating, exposure parameter determination method therefor, and manufacturing method and system therefor |
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| CN118192072B (en) * | 2024-04-08 | 2024-11-01 | 尼卡光学(天津)有限公司 | Volume holographic grating and grating vector distribution formulation, manufacturing method and manufacturing device thereof |
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| US7359046B1 (en) * | 2005-04-12 | 2008-04-15 | Ondax, Inc. | Method and apparatus for wafer-level measurement of volume holographic gratings |
| CN101246229A (en) * | 2008-03-25 | 2008-08-20 | 清华大学 | A method of directly fabricating a photoresist master grating on a convex substrate |
| CN101441431B (en) * | 2008-12-29 | 2011-11-30 | 中国科学院长春光学精密机械与物理研究所 | Method for real time monitoring exposure amount in holographic grating manufacture |
| CN102636968A (en) * | 2012-05-08 | 2012-08-15 | 上海理工大学 | Holographic exposure device of any groove grating structure and exposure method thereof |
| US10073416B2 (en) * | 2015-04-24 | 2018-09-11 | Lg Display Co., Ltd. | Method for producing a holographic optical element |
| CN106406061B (en) * | 2016-11-16 | 2021-11-19 | 苏州苏大维格科技集团股份有限公司 | Method for manufacturing volume holographic element |
| GB2574884A (en) * | 2018-06-22 | 2019-12-25 | Metamaterial Tech Inc | Spatially varying volume holographic gratings |
| CN111638571B (en) * | 2020-05-22 | 2021-04-27 | 东南大学 | An automatic exposure system for preparing color holographic waveguide gratings |
| CN113835145B (en) * | 2021-09-10 | 2023-08-15 | 深圳珑璟光电科技有限公司 | Holographic grating manufacturing device, holographic grating and two-dimensional holographic grating optical waveguide |
| CN114815024B (en) * | 2022-05-19 | 2023-08-08 | 南京工业职业技术大学 | Exposure area calculation method for batch preparation of holographic diffraction waveguides and application thereof |
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