Method for manufacturing large area gratings

Abstract

The method for manufacturing the large-area grating of the present application, the grating device comprises a base sheet and a grating, and the method comprises emitting a probe laser beam by a laser, passing through the first base sheet and irradiating the second grating, generating a diffracted laser beam, the diffracted laser beam passes through the first base sheet in a transmission mode, thereby entering the air; the light entering the air is reflected by a mirror to a target plate, the diffracted laser beam is received at the target plate, the center of the laser spot is marked on the target plate, denoted as P point; the grating device is translated to form P' point; if P' point and P point do not coincide, it is considered that the grating lines of the first grating and the second grating are not parallel, then the first base plate is horizontally rotated in a state that the grating device is not cured, and the laser spot on the target plate is observed until P' point and P point coincide, which does not need to increase other devices in the holographic recording light path, and the technology is simple and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical element manufacturing method, and particularly relates to a manufacturing method of a large-area grating. BACKGROUND

[0002] Holographic grating is a core element of new flat display and head-mounted display, and has been used by BAE and other companies to develop flat display and head-mounted display. The flat display and head-mounted display optical system containing holographic grating has the advantages of small structure, light weight and large exit pupil. Large-area holographic grating is a key element in flat display, and the parallelism of holographic grating lines is very high. The manufacturing of large-area holographic grating is limited by the aperture of the holographic recording optical system, so the method of splicing two holographic gratings is considered to manufacture large-area holographic grating, and the method of gluing alignment is used to ensure the parallelism of the holographic grating lines.

[0003] In the prior art, the method of multiple exposure splicing alignment is generally used, which needs to add piezoelectric ceramic feedback in the holographic recording light path, adjust and observe the moire fringe, and needs to repeatedly expose and develop the same holographic plate, which is not suitable for halide, gelatin and other recording materials. This technology is complex, difficult and has low success rate and high cost. SUMMARY

[0004] Therefore, the manufacturing method of the large-area grating provided by the present application can reduce the cost by manufacturing two gratings respectively, splicing them into a large-area grating by gluing, and ensuring the parallelism of the holographic grating lines by alignment.

[0005] A manufacturing method of a large-area grating is suitable for the manufacturing and testing of grating devices on optical display equipment or light splitting devices. The grating device includes a base sheet and a grating. The base sheet includes a first base sheet and a second base sheet with the same size. The grating includes a first grating and a second grating. The sum of the lengths of the first grating and the second grating is less than or equal to the length of the base sheet, or the sum of the lengths of the first grating and the second grating is less than or equal to the length of the first base sheet or the second base sheet. The bottom surface of the first base sheet is aligned with one end of the first grating. The top surface of the second base sheet is aligned with one end of the second grating corresponding to the first grating. The first base sheet and the second base sheet are glued to form the grating device. The manufacturing method includes the following steps.

[0006] A laser emits a probe laser beam, which passes through the first base sheet at a preset angle and irradiates the second grating to generate a diffracted laser beam. The diffracted laser beam passes through the first base sheet in a transmissive manner, and thus enters the air.

[0007] The light entering the air is reflected by a mirror to a target plate. The target plate receives the diffracted laser beam, and marks the center of the laser spot on the target plate as a P point.

[0008] Translate the grating device, so that the probe laser beam irradiates the first grating and produces a diffracted laser beam, the diffracted laser beam passes through the first substrate, enters the air again, reflects the light to the target plate through the mirror, marks the center of the laser spot on the target plate as P' point;

[0009] If P' point and P point do not coincide, it is considered that the grating lines of the first grating and the second grating are not parallel, then the grating device rotates the first substrate horizontally in the state of unhardened glue, and observes the laser spot on the target plate until P' point and P point coincide.

[0010] The technical beneficial effects of the present application are:

[0011] The present application adopts the method of glue alignment, which can realize the manufacture of large-area holographic grating. Two regions of holographic grating can be manufactured respectively, spliced into a large-area holographic grating by the method of glue, and the lines of the holographic gratings of the two regions are parallel to each other by the alignment method. Due to the separate manufacture of the holographic grating, the success rate of manufacture is greatly improved, and this method does not need to add other devices in the holographic recording light path, which is simple in technology and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor.

[0013] Figure 1 is a schematic view of a first glass flat plate and a first holographic grating;

[0014] Figure 2 is a schematic view of a second glass flat plate and a second holographic grating;

[0015] Figure 3 is a schematic view of the first and second glass flat plates stacked;

[0016] Figure 4 is a schematic view of a laser beam test;

[0017] Figure 5 is a schematic view of glue alignment,

[0018] Wherein, 101, first substrate; 102, first grating; 103, second substrate; 104, second grating; 105, optical glue; 201, illuminating light with using angle; 202, diffracted light with using angle; 203, probe laser beam; 204, diffracted laser beam; 205, diffracted laser beam parallel to optical platform surface after adjustment by mirror; 206, laser; 207, mirror; 208, target plate. DETAILED DESCRIPTION

[0019] The embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0020] The above embodiments of the present disclosure are described with reference to specific examples. However, a person of ordinary skill in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in the specification. It is obvious that the described embodiments are only some of the embodiments of the present disclosure, but not all of the embodiments. The present disclosure can also be implemented or applied by other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by a person of ordinary skill in the art without creative labor are within the scope of protection of the present disclosure.

[0021] It should be noted that the various aspects of the embodiments described below are within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms and that any specific structure and / or function described herein is merely illustrative. Based on the teachings herein one skilled in the art should appreciate that an aspect described herein can be implemented independently of any other aspects and that an aspect described herein can be implemented both as any number of software and / or hardware structures and as any number of processes and / or operations. For example, an aspect can be implemented as a software program running on hardware that can process information such as, for example, information stored in a computer-readable storage medium. As another example, an aspect can be implemented as a software program running on hardware that can process information such as, for example, information stored in a computer-readable storage medium.

[0022] As Figures 1 to 5The method for manufacturing the large-area grating shown is suitable for manufacturing and testing grating devices on optical display devices or light splitting devices. The grating device includes a base sheet and a grating. The base sheet includes a first base sheet 101 and a second base sheet 103 with the same size. The grating or holographic grating includes a first grating 102 and a second grating 104. The sum of the lengths of the first grating 102 and the second grating 104 is less than or equal to the length of the base sheet, or the sum of the lengths of the first grating 102 and the second grating 104 is less than or equal to the length of the first base sheet 101 or the second base sheet 103. The bottom surface of the first base sheet 101 is aligned with one end of the first grating 102, for example, by using optical glue 105 to bond the first grating 102. The top surface of the second base sheet 103 is aligned with one end of the second grating 104 corresponding to the first grating 102. See Figure 1 The first grating 102 is on the left side of the first base sheet 101. See Figure 2 The second grating 104 is on the right side of the second base sheet 103. The first base sheet 101 and the second base sheet 103 are glued to form a grating device. The two gratings are located in the middle position to form a holographic grating. The manufacturing method includes,

[0023] A long-wave test is performed. A laser 206 emits a probe laser beam 203 at a preset angle in the range of 10°-60°. The probe laser beam 203 passes through the first base sheet 101 and irradiates the second grating 104 to generate a diffracted laser beam 204. The diffracted laser beam 204 passes through the first base sheet 101 in a transmissive manner to enter the air to form the diffracted laser beam 204.

[0024] The light entering the air passes through a mirror 207 to form a mirror-adjusted diffracted laser beam 205 parallel to the surface of the optical platform. The mirror-adjusted diffracted laser beam 205 is received on a target plate 208. The center of the laser spot is marked on the target plate 208 as a P point. A long-wave non-use angle test is performed. The holographic grating in a flat display is generally a holographic waveguide grating. When the illuminating light irradiates the second grating 104 at a use angle, the diffracted light will be totally reflected in the glass flat plate at a large angle and cannot enter the air, which is not convenient for observation. Therefore, the laser 206 with a wavelength greater than that of the illuminating light emits a probe laser beam 203 at an appropriate angle greater than the use angle to irradiate the second grating 104. This can make the diffracted laser beam 204 pass through the first base sheet 101 to enter the air, which is convenient for observation. It should be noted that when the illuminating light 201 is incident at the use angle, the diffracted light 202 at the use angle cannot be diffracted to the mirror 207.

[0025] Translate the grating device, so that the probe laser beam 203 irradiates the first grating 102 and produces a diffracted laser beam 204, the diffracted laser beam 204 through the first substrate 101, into the air again, by the mirror 207 to reflect the light to the target plate 208, on the target plate 208 mark the center of the laser spot, marked as P' point;

[0026] As shown in Figure 5 If the P' point and the P point do not coincide, it is considered that the grating lines of the first grating 102 and the second grating 104 are not parallel, then the grating device is in the state of curing the glue, and the first substrate is horizontally rotated, and the laser spot on the target plate 208 is observed until the P' point and the P point coincide. Preferably, different types of grating devices correspond to different distances of the target plate 208 position, for example, the coincidence accuracy of the P' point and the P point is related to the placement position of the target plate, and the farther the target plate 208 is, the higher the correction accuracy is.

[0027] In the above, the first substrate and the second substrate are made of glass or other transparent materials, and the wavelength of the laser 206 emitting the probe laser beam 203 is 650 nm.

[0028] For example

[0029] The following describes an example of a certain type of holographic grating element for flat display. The two glass plates are glued together, and the holographic grating is in the glue layer. The type of holographic grating is a bulk holographic waveguide grating, the material of the glass plate is fused quartz, and the recording medium of the holographic grating is dichromate gelatin.

[0030] (1) A first holographic grating is made on the first glass substrate, and the first holographic grating is located below and to the right of the first glass substrate. A second holographic grating is made on the second glass substrate, and the second holographic grating is located above and to the left of the second glass substrate.

[0031] (2) The second glass substrate is fixed to the optical platform, and the fixed way is to use the magnetic table seat to abut against the side of the second glass plate, so that it cannot be translated or rotated;

[0032] (3) The first glass substrate is placed above the second glass substrate, and the second glass substrate and the first glass substrate are filled with optical epoxy resin glue. The combination of the first glass substrate and the second glass substrate is clamped on the guide rail which can move horizontally. Before the optical epoxy resin glue is cured, complete

[0033] (9) operation;

[0034] (4) use a laser to emit a probe laser beam, which passes through the first glass substrate at a proper angle, illuminates the second holographic grating, and generates a diffracted laser beam, which passes through the first glass substrate and enters the air. It should be noted that the holographic grating in the flat display is generally a holographic waveguide grating. When the illuminating light ray illuminates the second holographic grating at the use angle, the diffracted light ray will be totally reflected in the glass flat plate at a large angle and cannot enter the air, which is inconvenient for observation. Therefore, the use of a laser with a wavelength greater than that of the illuminating light ray and a proper angle greater than the use angle to emit a probe laser beam to illuminate the second holographic grating can make the diffracted laser beam pass through the first substrate and enter the air, which is convenient for observation. In this embodiment, the illuminating light ray is incident at an angle of 0°, the wavelength of the illuminating light ray is 532 nm, the wavelength of the laser is 650 nm, the probe laser beam illuminates the first glass substrate at an incident angle of 60°, passes through the first glass substrate, illuminates the second holographic grating, and the diffracted laser beam passes through the first glass substrate and enters the air;

[0035] (5) insert a mirror in the transmission path of the diffracted laser beam and adjust the mirror to make the diffracted laser beam parallel to the surface of the optical platform;

[0036] (6) set a target plate at a position 10 meters away from the test point, i.e., the position where the probe laser beam illuminates the holographic grating, to receive the diffracted laser beam and mark the center of the laser spot on the target plate as point P;

[0037] (7) move the guide rail to translate the combination of the first glass substrate and the second glass substrate, so that the probe laser beam illuminates the first holographic grating, generates a diffracted laser beam, and the diffracted laser beam passes through the first glass substrate and enters the air. The diffracted laser beam is reflected by the mirror and illuminates the target plate, and the center of the laser spot is point P'. If the grating lines of the first holographic grating and the second holographic grating are not parallel, points P' and P do not coincide;

[0038] (8) horizontally rotate the first glass substrate and simultaneously observe the laser spot on the target plate to make points P' and P coincide and align;

[0039] (9) after 24 hours, the epoxy resin glue is cured, and the fabrication of the large-area holographic grating is completed.

[0040] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or replacements within the technical range disclosed in the present disclosure can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A method for fabricating a large-area grating, applicable to the fabrication and testing of grating devices on optical display devices or beam splitters, wherein the grating device comprises a substrate and a grating, characterized in that, The substrate includes a first substrate and a second substrate of the same size. The grating includes a first grating and a second grating. The sum of the lengths of the first grating and the second grating is less than or equal to the length of the substrate, or the sum of the lengths of the first grating and the second grating is less than or equal to the length of either the first substrate or the second substrate. The first grating is aligned with one end of the bottom surface of the first substrate, and the second grating is aligned with the other end of the top surface of the second substrate corresponding to the first substrate. The first substrate and the second substrate are bonded together to form a grating device. The fabrication method includes... A laser emits a probe laser beam, which passes through the first substrate at a preset angle and illuminates the second grating, generating a diffracted laser beam. The diffracted laser beam passes through the first substrate in a transmission manner and enters the air. The preset angle ranges from 10° to 60°. Light entering the air is reflected by a mirror to the target plate, which receives the diffracted laser beam and marks the center of the laser spot on the target plate, denoted as point P. The grating device is translated so that the probe laser beam illuminates the first grating and generates a diffracted laser beam. The diffracted laser beam passes through the first substrate, re-enters the air, and is reflected by a mirror to the target plate. The center of the laser spot is marked on the target plate and denoted as point P'. If point P' and point P do not coincide, it is considered that the grating lines of the first grating and the second grating are not parallel. Then, while the grating device is in the uncured state of adhesive bonding, the first substrate is rotated horizontally and the laser spot on the target plate is observed until point P' and point P coincide.

2. The manufacturing method according to claim 1, characterized in that, Different types of grating devices correspond to target plate positions at different distances.

3. The manufacturing method according to claim 1, characterized in that, The first and second substrates are made of glass.

4. The manufacturing method according to claim 1, characterized in that, The laser emits a detection laser beam with a wavelength of 650 nm.

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