A device and method for plane splicing large-area gratings

Abstract

A device and method for planar splicing of large-area gratings, comprising a first beam path and a second beam path to generate a coherent beam and form an exposure interference field, which is received by a grating substrate to be exposed. Two reference gratings are provided in the device, which work in conjunction to generate moiré fringes, which are monitored by a moiré fringe detection sensor. A controller compensates for phase, tilt, and period errors using an optical path difference adjustment device and a beam direction adjustment device based on the monitoring results. A translation stage device moves the grating substrate and optical elements to achieve precise docking of different exposure areas. The first reference grating is fixed, while the second reference grating moves along the Y direction with the grating substrate. The present invention is capable of multi-row splicing, breaking the limitations of traditional single-row splicing and increasing the flexibility and application range of grating processing. It not only improves diffraction efficiency and simplifies optical path design, but also reduces processing costs and ensures good grating splicing processing results.

Description

Technical Field

[0001] The present invention relates to holographic grating technology, and in particular to a planar splicing large-area grating device and method. Background Art

[0002] Large-area diffraction gratings play an important role in high-power chirped-pulse amplified laser systems for inertial confinement fusion, high-resolution spectral analysis in astronomical telescopes, and remote interferometry. Holographic exposure can produce holographic gratings through a single exposure, but the exposure aperture is limited by the size of the optical components, as large-aperture, low-aberration collimating lenses are difficult and expensive to manufacture.

[0003] In the stitching exposure, each area of ​​the substrate will be illuminated by a small-scale interference field, and then the substrate moves to the next area to be exposed for the next exposure. In order to maintain the continuity of the wavefronts in adjacent exposure areas, the phase of the stripes in different exposure areas needs to be continuous, and the period and inclination angle need to be the same during the stitching process. That is, the phase and posture of the exposure strips relative to the substrate are guaranteed to be the same between adjacent exposures. BG TURUKHANO proposed a method of using a reference grating to monitor the stitching error to process long strip stitching gratings. This method is limited to processing long strip gratings and cannot be expanded in another direction. Shi Lei et al. proposed a method based on the moiré fringes generated by the latent image grating (photoresist exposed but not developed) to monitor the possible stitching errors in different exposure areas. The latent image grating required for this method has low diffraction efficiency (about 10 -5 The optical path is more complicated because the latent image area used for error monitoring needs to be protected.

[0004] In existing grating splicing processes, the reference grating method is mainly limited to single-row splicing. Although the solution using latent image grating can splice multiple rows, the latent image grating has low diffraction efficiency, complex optical path and difficult adjustment.

[0005] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0006] The main purpose of the present invention is to overcome the defects in the above-mentioned background technology and provide a planar splicing large-area grating device and method.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A planar splicing large-area grating device, comprising:

[0009] A first light beam path and a second light beam path, for providing a coherent light beam and forming an exposure interference field;

[0010] A grating substrate to be exposed, used to receive the exposure interference field;

[0011] a first reference grating and a second reference grating for generating moiré fringes;

[0012] an optical path difference adjustment device, provided on the first light beam path, for adjusting the optical path difference between the two exposure light beams to compensate for phase error;

[0013] A beam direction adjustment device is provided on the first beam path or the second beam path, and is used to adjust the spatial direction of the exposure beam to compensate for the grid line period and tilt errors;

[0014] A moiré fringe detection sensor for monitoring moiré fringes formed by two exposure beams passing through a reference grating;

[0015] A translation stage device includes a first translation stage and a second translation stage, wherein the first translation stage is used to move related optical elements in the X direction to change the position of the exposure area, and the second translation stage is used to move the grating substrate and the second reference grating in the Y direction to achieve precise docking of different exposure areas on the grating substrate and planar splicing of large-area grating exposure areas; the first reference grating is separated from the grating substrate and remains stationary;

[0016] The controller is used to compensate for the stitching error based on the moiré fringe changes of the moiré fringe detection sensor. By controlling the optical path difference adjustment device and the beam direction adjustment device, the phase, tilt and period errors introduced in the stitching process are compensated to ensure the continuity of the fringe phase, period and tilt angle in the exposure area.

[0017] Furthermore, the optical path difference adjustment device includes a plane reflector and a piezoelectric ceramic actuator rod or a piezoelectric nano-displacement stage for driving the plane reflector to move.

[0018] Furthermore, the light beam direction adjustment device includes a plane reflective mirror and a biaxial piezoelectric mirror frame or a piezoelectric nano-rotation stage that drives the plane reflective mirror to rotate.

[0019] Furthermore, the moire fringe detection sensor includes a CCD camera.

[0020] Furthermore, the light beam emitted by the laser is split by a beam splitter prism to obtain the first light beam and the second light beam.

[0021] Furthermore, the two exposure beams generate -2 and -1 order diffraction light interference to form moiré fringes after passing through the reference grating.

[0022] Furthermore, the grating substrate is placed vertically or horizontally.

[0023] A method for plane splicing large-area gratings using the plane splicing large-area grating device comprises:

[0024] Emits a light beam through a laser, and uses a beam splitter prism to split the light beam into a first light beam and a second light beam, thereby forming a first light beam path and a second light beam path, so as to provide a coherent light beam and form an exposure interference field;

[0025] The first reference grating and the second reference grating are arranged coplanar with the grating substrate to be exposed to generate moiré fringes;

[0026] An optical path difference adjustment device is used to adjust the optical path difference between the two exposure beams to compensate for the phase error;

[0027] A beam direction adjustment device is used to adjust the spatial directions of the two exposure beams to compensate for the grid line period and tilt errors;

[0028] The moiré fringe detection sensor monitors the moiré fringes formed by the interference of the -2nd and -1st order diffraction lights generated by the two exposure beams passing through the reference grating;

[0029] operating a translation stage device, wherein a first translation stage moves related optical elements in the X direction to change the position of the exposure area, and a second translation stage moves the grating substrate and the second reference grating in the Y direction to achieve precise docking of different exposure areas on the grating substrate and planar splicing of large-area grating exposure areas; and the first reference grating is separated from the grating substrate and remains stationary;

[0030] According to the monitoring results of the moiré fringe detection sensor, the controller compensates for the stitching error, controls the optical path difference adjustment device and the beam direction adjustment device, compensates for the phase, tilt and period errors introduced during the stitching process, and ensures the continuity of the fringe phase, period and tilt angle in the exposure area.

[0031] Furthermore, the method specifically includes:

[0032] Ensure that the phase, period, and tilt of the reference fringe are the same as those generated by the previous exposure to maintain the phase and posture of the fringe;

[0033] When a phase error is detected, the plane reflector connected to the piezoelectric ceramic actuator rod moves back and forth to change the optical path of the single-path light to adjust the position of the stripes in the exposure area and achieve phase error compensation;

[0034] When a grid line period error is detected, the angle between the two exposure beams is adjusted by adjusting the deflection angle of the plane reflector through the biaxial piezoelectric mirror frame, thereby changing the period of the processed stripes and compensating for the grid line period error.

[0035] When a grid line tilt error is detected, the pitch angle of the reflector is adjusted by the biaxial piezoelectric mirror frame to adjust the angle of the plane where the two exposure beams are located, thereby compensating for the grid line tilt error.

[0036] Furthermore, the method specifically includes:

[0037] The grating substrate to be exposed includes square areas forming an n×n grid array, where n is not less than 2. During the planar stitching of large-area gratings, the exposure beam and the reference fringes generated by the reference grating are precisely controlled. The first area is exposed and the initial fringes are recorded while shielding the non-exposed portion of the grating substrate. Subsequently, the subsequent areas are precisely aligned using a translation stage, and the remaining areas are exposed while maintaining the phase, period, and tilt of the reference fringes in the previous area. During this process, a moiré fringe detection sensor is used to monitor and lock the reference fringes in real time to ensure the continuity and consistency of the fringes between the stitching areas, thereby achieving precise planar stitching of large-area gratings.

[0038] The present invention has the following beneficial effects:

[0039] The present invention provides a device and method for achieving large-area grating plane splicing. The method effectively monitors and compensates for phase, tilt, and period errors during the splicing process by using two reference gratings working in conjunction with a grating substrate. Compared with the prior art, the present invention can process spliced ​​gratings with any number of rows and columns, breaking the limitations of previous technologies in the splicing direction and improving processing flexibility and application range. In addition, the reference grating used in the present invention has high diffraction efficiency, which simplifies the optical path design and makes optical path adjustment simpler and faster. By recording reference stripes multiple times and moving the light beam to align with different areas, the present invention can ensure that the errors in each splicing area are accurately monitored and compensated, thereby ensuring the continuity and overall quality of the spliced ​​grating diffraction wavefront. Ultimately, the grating processed using the system of the present invention has excellent -1 order diffraction wavefront PV value and RMS value, and the phase error, tilt error, and period error are all controlled at a low level, significantly improving the performance and accuracy of the spliced ​​grating.

[0040] The present invention uses a reference grating to monitor errors and fabricate spliced ​​gratings with any number of rows and columns, enabling multi-row splicing. The reference grating offers high diffraction efficiency, a simple optical path, and easy optical path adjustment. By detecting and compensating for phase, tilt, and period errors, the fabricated spliced ​​grating exhibits a continuous diffraction wavefront. The proposed solution ensures that errors in every region of the spliced ​​grating are monitored and compensated, ensuring excellent grating splicing results.

[0041] Other beneficial effects of the embodiments of the present invention will be further described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the structure of a planar splicing large-area grating device according to an embodiment of the present invention.

[0043] Figures 2a to 2j This is an example diagram of a method for plane stitching large-area gratings according to an embodiment of the present invention.

[0044] Figure 3 This is the measurement principle diagram of Fizeau interferometer.

[0045] Figure 4 This is the -1st order diffraction wavefront diagram of the grating processed by the planar splicing large-area grating device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0047] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and coupling or communication.

[0048] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0050] See Figure 1The embodiment of the present invention provides a planar splicing large-area grating device, comprising: a first light beam path and a second light beam path, for providing a coherent light beam and forming an exposure interference field; a grating substrate 11 to be exposed, for receiving the exposure interference field; a first reference grating 10 and a second reference grating 12, for generating moiré fringes; an optical path difference adjustment device, arranged on the first light beam path, for adjusting the optical path difference between the two exposure light beams to compensate for phase error; a beam direction adjustment device, arranged on the first light beam path or the second light beam path, for adjusting the spatial direction of the exposure light beam to compensate for grating line period and tilt error; a moiré fringe detection sensor, for monitoring the moiré fringes formed by the two exposure light beams after passing through the reference grating; a translation stage device, comprising a first A translation stage and a second translation stage, wherein the first translation stage is used to move related optical elements in the X direction to change the position of the exposure area, and the second translation stage is used to move the grating substrate 11 and the second reference grating 12 in the Y direction to achieve precise docking of different exposure areas on the grating substrate 11 and planar splicing of large-area grating exposure areas; the first reference grating 10 is separated from the grating substrate 11 and remains stationary; a controller is used to compensate for splicing errors based on the change of the moiré fringes of the moiré fringe detection sensor, and to compensate for the phase, tilt and period errors introduced in the splicing process by controlling the optical path difference adjustment device and the beam direction adjustment device, so as to ensure the continuity of the fringe phase, period and tilt angle of the exposure area.

[0051] The present invention realizes high-precision grating splicing technology through an innovative planar splicing large-area grating device. The device combines a dual-reference grating system, a translation stage device, and a controller to provide an effective solution for large-area grating splicing in multiple directions. The core mechanism of the present invention is to introduce two reference gratings to generate moiré fringes, where one reference grating is fixed and the other moves with the grating substrate, allowing the system to independently control the exposure area in the X and Y directions to achieve precise docking; the optical path difference adjustment device and the beam direction adjustment device are responsible for compensating for phase error and grating line period and tilt error respectively, while the moiré fringe detection sensor monitors the splicing error in real time. The controller dynamically adjusts the beam path based on this data to ensure the continuity of the fringe phase, period, and tilt angle in the exposure area. During operation, by recording reference fringes multiple times and moving the beam to align with different areas, the present invention can ensure that the errors in each splicing area are accurately monitored and compensated, thereby ensuring the continuity and overall quality of the spliced ​​grating diffraction wavefront. This mechanism not only improves the splicing efficiency but also significantly enhances the continuity of the diffraction wavefront of the spliced ​​gratings, resulting in the processed gratings having excellent performance with a -1 order diffraction wavefront PV value as low as 0.125λ and an RMS of 0.022λ. The phase error is controlled within 3.5%, the tilt error does not exceed 0.0040rad, and the period error does not exceed 0.25%. Compared to traditional technologies, the device and method of the present invention not only break through the size limitations of optical components and reduce processing difficulty and cost, but also improve diffraction efficiency, simplify optical path design, and enable multi-row splicing, making the splicing processing of large-area gratings more flexible, efficient, and precise.

[0052] See Figure 1 In some embodiments, the optical path difference adjustment device includes a plane mirror (second plane mirror 22) and a piezoelectric ceramic actuator 23 or a piezoelectric nanometer displacement stage that drives the plane mirror. The beam direction adjustment device includes a plane mirror (fourth plane mirror 18) and a biaxial piezoelectric mirror holder 17 or a piezoelectric nanometer rotation stage that drives the plane mirror. The moiré fringe detection sensor includes a CCD camera 15.

[0053] See Figure 1The embodiment of the present invention further provides a method for plane splicing large-area gratings using the above-mentioned plane splicing large-area grating device, comprising the following steps: emitting a light beam through a laser 1, and using a beam splitter prism 4 to split the light beam into a first light beam and a second light beam, forming a first light beam path and a second light beam path, for providing a coherent light beam and forming an exposure interference field; using a first reference grating 10 and a second reference grating 12 to be arranged coplanar with a grating substrate 11 to be exposed to generate moiré fringes; using an optical path difference adjustment device to adjust the optical path difference between the two exposure beams to compensate for phase error; using a beam direction adjustment device to adjust the spatial directions of the two exposure beams to compensate for grating line period and tilt errors; using a moiré fringe detection sensor to monitor the optical path difference between the two exposure beams passing through the reference light beam. Moiré fringes are formed by interference between -2 and -1 order diffraction light generated behind the grating; an operating stage device is provided, wherein a first stage moves related optical elements in the X direction to change the position of the exposure area, and a second stage moves the grating substrate and the second reference grating 12 in the Y direction to achieve precise docking of different exposure areas on the grating substrate and planar splicing of large-area grating exposure areas; the first reference grating 10 is separated from the grating substrate and remains stationary; based on the monitoring results of the moiré fringe detection sensor, the controller compensates for the splicing error, controls the optical path difference adjustment device and the beam direction adjustment device, compensates for the phase, tilt and period errors introduced during the splicing process, and ensures the continuity of the phase, period and tilt angle of the fringes in the exposure area.

[0054] See Figure 1 In some embodiments, the method specifically includes: ensuring that the phase, period and tilt of the reference stripes are the same as those of the reference stripes generated by the previous exposure to maintain the phase and posture of the stripes; when a phase error is detected, the plane mirror (the second plane mirror 22) connected to the piezoelectric ceramic actuator rod 23 is moved back and forth to change the optical path of the single-path light to adjust the stripe position in the exposure area to achieve compensation for the phase error; when a grid line period error is detected, the deflection angle of the plane mirror (the fourth plane mirror 18) is adjusted by the biaxial piezoelectric mirror frame 17 to adjust the angle between the two exposure beams, thereby changing the period of the stripes to be processed to achieve compensation for the grid line period error; when a grid line tilt error is detected, the pitch angle of the plane mirror (the fourth plane mirror 18) is adjusted by the biaxial piezoelectric mirror frame 17 to adjust the angle of the plane where the two exposure beams are located to achieve compensation for the grid line tilt error.

[0055] See Figures 2a to 2jIn some embodiments, the method specifically includes: a grating substrate to be exposed includes square grid areas forming an n×n grid array, where n is not less than 2; during the process of planar stitching of large-area gratings, by precisely controlling the exposure beam and the reference fringes generated by the reference grating, firstly, while shielding the non-exposed portion of the grating substrate, the first area is exposed and the initial fringes are recorded; then, the subsequent areas are precisely aligned by a translation stage, and the remaining areas are exposed while maintaining the phase, period, and tilt of the reference fringes of the previous area unchanged; during this process, a moiré fringe detection sensor is used to monitor and lock the reference fringes in real time to ensure the continuity and consistency of the fringes between the stitching areas, thereby achieving precise planar stitching of large-area gratings.

[0056] Specific embodiments of the present invention are further described below.

[0057] Planar splicing device for large-area gratings

[0058] Figure 1 The schematic diagram of the structure of a planar splicing large-area grating device is shown. The planar splicing large-area grating device of this embodiment includes a laser 1, a shutter 2, a first half-wave plate 3, a second half-wave plate 5, a beam splitter 4, a first plane reflector 6, a second plane reflector 22, a third plane reflector 14, a fourth plane reflector 18, a first spatial light filter 7, a second spatial light filter 21, a first collimating lens 8, a second collimating lens 20, a first rectangular aperture 9, a second rectangular aperture 19, a grating substrate to be exposed 11, a first reference grating 10, a second reference grating 12, a first translation stage 16, a second translation stage 13, a CCD camera 14, a piezoelectric ceramic actuator rod 23, and a biaxial piezoelectric mirror holder 17.

[0059] After the two exposure beams pass through the reference grating, the -2nd and -1st order diffracted light, respectively, interfere to form moiré fringes. The resulting moiré fringes are monitored using a CCD camera. A stationary reference grating (separate from the substrate) is placed in front of substrate S. During splicing in the x-direction, neither the substrate nor the reference grating remains stationary. The first translation stage simultaneously drives the third plane mirror, the fourth plane mirror, and the CCD camera to move in the x-direction. The movement of the third and fourth plane mirrors changes the position of the exposure area. Another reference grating is fixed to the side of the grating substrate to be exposed (the substrate and reference grating are both fixed to the second translation stage). During splicing in the y-direction, the second translation stage drives the substrate and reference grating to move simultaneously in the y-direction. The piezoelectric ceramic actuator rod is a piezoelectric push rod used to adjust phase error. The fourth plane mirror is mounted on a dual-axis piezoelectric mirror mount to compensate for grating line period and tilt errors.

[0060] Phase, tilt, and period errors introduced during the stitching process will cause phase tilt and period variations in the reference fringes produced by the reference grating, respectively. To ensure that the fringes have the same phase and orientation, it is sufficient to ensure that the phase, period, and tilt of the reference fringes remain unchanged from those produced by the previous exposure.

[0061] The stitching error is compensated based on the monitored reference stripes. A piezoelectric ceramic actuator rod is used to connect the second plane reflector. The piezoelectric push rod moves back and forth to drive the second plane reflector to move back and forth. The position of the stripes in the exposure area is adjusted by changing the optical path of the single-path light to compensate for the phase error. The phase is locked to the original position through real-time monitoring of the reference stripes. A dual-axis piezoelectric mirror frame is used to adjust the pitch and deflection angles of the reflector. By adjusting the deflection of a beam of light to change the angle between the two exposure beams, the period of the processed stripes will also change. The grid line period error can be compensated by changing the deflection angle. Changing the pitch angle of the reflector can change the azimuth angle of the single beam of light to adjust the angle of the plane where the two beams are located. The grid line tilt error can be compensated by changing the pitch angle.

[0062] Planar stitching methods for large area gratings, such as Figures 2a to 2j As shown, the following steps are included:

[0063] Step 1: While shielding the substrate, turn on the exposure beam and record the reference fringe produced by the first reference grating, referred to as initial fringe 1-1. Then, while locking the reference fringe (ensuring the fringe phase and attitude remain unchanged), expose area 1.

[0064] Step 2: Translate the first stage to align the exposure area with Area 2. While shielding the substrate, turn on the exposure beam and align the reference fringe produced by the first reference grating with the initial fringe 1-1 recorded in Step 1 (i.e., the phase, period, and tilt are identical). Then, while locking onto the reference fringe, expose Area 2.

[0065] Step 3: Shift the first translation stage to align the exposure area with Area 3. At this point, both reference gratings appear simultaneously within the exposure area. While shielding the substrate, turn on the exposure beam and align the reference fringe produced by the first reference grating with Initial Fringe 1-1, locking and recording the reference fringe produced by the second reference grating, referred to as Initial Fringe 2. Using the reference fringe of the first reference grating, locked with Initial Fringe 1-1, expose Area 3.

[0066] Step 4: Translate the second translation stage and align the exposure area with Area 6. While shielding the substrate, turn on the exposure beam and align the reference fringe produced by the second reference grating with Initial Fringe 2, locking and recording the reference fringe produced by the first reference grating, referred to as Initial Fringe 1-2. Using the reference fringe of the first reference grating, locked with Initial Fringe 1-2, expose Area 6.

[0067] Step 5: Translate the first translation stage to align the exposure area with area 5. While shielding the substrate, turn on the exposure beam and align the reference stripes generated by the first reference grating with the initial stripes 1-2. Expose area 5 while locking the reference stripes.

[0068] Step 6: Translate the first translation stage to align the exposure area with area 4. While shielding the substrate, turn on the exposure beam and align the reference stripes generated by the first reference grating with the initial stripes 1-2. Expose area 4 while locking the reference stripes.

[0069] Step 7: Translate the first and second translation stages to align the exposure area with area 9. While shielding the substrate, turn on the exposure beam and align the reference stripes generated by reference grating 2 with initial stripes 2, locking them and recording the reference stripes generated by reference grating 1, referred to as initial stripes 1-3. Using the reference stripes of reference grating 1, locked with initial stripes 1-3, expose area 9.

[0070] Step 8: Translate the first translation stage to align the exposure area with area 8. While shielding the substrate, turn on the exposure beam and align the reference stripes generated by the first reference grating with the initial stripes 1-3. Expose area 8 while locking the reference stripes.

[0071] Step 9: Translate the first translation stage to align the exposure area with area 7. While shielding the substrate, turn on the exposure beam and align the reference stripes generated by the first reference grating with the initial stripes 1-3. Expose area 7 while locking the reference stripes.

[0072] The 9-region stitching proposed in the above embodiment is only an example. The method can be applied to the stitching of n×n regions, and the process is the same.

[0073] In different embodiments, different areas can be exposed in any order in the stitching method, such as first performing step 6 to expose area 4, and then performing step 5 to expose area 5.

[0074] In different embodiments, the actuator piezoelectric ceramic actuator rod 23 that drives the second plane reflector 22 can be replaced with a single-axis piezoelectric nano-displacement stage.

[0075] In different embodiments, the -2 and -1 order diffraction lights in the splicing method can be replaced with other orders that can overlap and generate interference fringes.

[0076] In different embodiments, the period and tilt angle can be compensated by changing the position of the aperture of the spatial light filter.

[0077] In different embodiments, the substrate can be placed horizontally instead of vertically. When placed horizontally, the front-end structure of the optical path is changed so that the light beam is irradiated downward.

[0078] A method for detecting a wavefront error of a spliced ​​grating comprises the following steps:

[0079] The -m order diffraction wavefront is detected using a Fizeau interferometer. The 0 order diffraction wavefront is also measured to eliminate the additional impact of substrate unevenness. When measuring the -m order wavefront, the grating is placed at an angle of

[0080]

[0081] is the interferometer wavelength, and d is the period of the grating to be measured.

[0082] When there is a phase error, the diffraction wavefront pattern is discontinuous and exhibits jumps. Fringe misalignment caused by wavefront misalignment can be observed in the interferogram: the left and right fringes are disjointed at their junctions. When there is a grid line period error, the diffraction wavefront pattern deflects, and variations in the fringe period can be observed in the interferogram. When there is a grid line tilt error, the diffraction wavefront pattern deflects, and variations in the fringe tilt can be observed in the interferogram.

[0083] When there is phase error in the grating lines of the spliced ​​grating When , the diffraction wavefront jump becomes:

[0084]

[0085] When there is a grid line tilt error, the diffraction wave surface will tilt. When the grid line tilt error is When the diffraction wave surface is tilted for:

[0086]

[0087] in Place the angle for the grating.

[0088] When there is a grid line period error, the diffraction wave surface will tilt in another direction. When the diffraction wave surface is tilted for:

[0089]

[0090] The measurement principle diagram of the cable interferometer is as follows: Figure 3 shown.

[0091] A reference grating can be used to monitor errors and process spliced ​​gratings with any number of rows and columns. The reference grating has high diffraction efficiency, a simple optical path, and is easy to adjust.

[0092] The present invention's planar spliced ​​large-area grating device can detect and compensate for phase, tilt, and period errors. The resulting spliced ​​grating produces a continuous diffraction wavefront. This ensures that errors in each region of the spliced ​​grating are monitored and compensated, ensuring excellent results.

[0093] The PV value of the first-order diffraction wavefront of the grating produced by the planar splicing large-area grating device of the present invention is 0.125 ,RMS is 0.022 The phase error does not exceed 3.5%, the tilt error does not exceed 0.0040rad, and the period error does not exceed 0.25%. Figure 4 shown.

[0094] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A planar splicing large area grating device, characterized in that: include: A first light beam path and a second light beam path, for providing a coherent light beam and forming an exposure interference field; A grating substrate to be exposed, used to receive the exposure interference field; a first reference grating and a second reference grating for generating moiré fringes; an optical path difference adjustment device, provided on the first light beam path, for adjusting the optical path difference between the two exposure light beams to compensate for phase error; A beam direction adjustment device is provided on the first beam path or the second beam path, and is used to adjust the spatial direction of the exposure beam to compensate for the grid line period and tilt errors; A moiré fringe detection sensor for monitoring moiré fringes formed by two exposure beams passing through a reference grating; A translation stage device includes a first translation stage and a second translation stage, wherein the first translation stage is used to move an optical element related to determining the position of an exposure area in the X direction to change the position of the exposure area, and the second translation stage is used to move the grating substrate and the second reference grating in the Y direction to achieve precise docking of different exposure areas on the grating substrate and planar splicing of large-area grating exposure areas; the first reference grating is separated from the grating substrate and remains stationary; The controller is used to compensate for the stitching error based on the moiré fringe changes of the moiré fringe detection sensor. By controlling the optical path difference adjustment device and the beam direction adjustment device, the phase, tilt and period errors introduced in the stitching process are compensated to ensure the continuity of the fringe phase, period and tilt angle in the exposure area.

2. The planar splicing large-area grating device according to claim 1, characterized in that: The optical path difference adjustment device includes a plane reflector and a piezoelectric ceramic actuator rod or a piezoelectric nano-displacement stage for driving the plane reflector to move.

3. The planar splicing large-area grating device according to claim 1, characterized in that: The light beam direction adjustment device comprises a plane reflector and a biaxial piezoelectric mirror frame or a piezoelectric nano-rotation stage for driving the plane reflector to rotate.

4. The planar splicing large-area grating device according to any one of claims 1 to 3, characterized in that: The moire fringe detection sensor includes a CCD camera.

5. The planar splicing large-area grating device according to any one of claims 1 to 3, characterized in that: The light beam emitted by the laser is split by a beam splitter prism to obtain the first light beam and the second light beam.

6. The planar splicing large-area grating device according to any one of claims 1 to 3, characterized in that: The two exposure beams generate -2 and -1 order diffraction light interference after passing through the reference grating to form moiré fringes.

7. The planar splicing large-area grating device according to any one of claims 1 to 3, characterized in that: The grating substrate is placed vertically or horizontally.

8. A method for plane splicing large-area gratings using the plane splicing large-area grating device according to any one of claims 1 to 7, characterized in that: include: Emits a light beam through a laser, and uses a beam splitter prism to split the light beam into a first light beam and a second light beam, thereby forming a first light beam path and a second light beam path, so as to provide a coherent light beam and form an exposure interference field; The first reference grating and the second reference grating are arranged coplanar with the grating substrate to be exposed to generate moiré fringes; An optical path difference adjustment device is used to adjust the optical path difference between the two exposure beams to compensate for the phase error; A beam direction adjustment device is used to adjust the spatial directions of the two exposure beams to compensate for the grid line period and tilt errors; The moiré fringe detection sensor monitors the moiré fringes formed by the interference of the -2nd and -1st order diffraction lights generated by the two exposure beams passing through the reference grating; operating a translation stage device, wherein a first translation stage moves an optical element associated with determining a position of an exposure area in an X direction to change the position of the exposure area, and a second translation stage moves a grating substrate and a second reference grating in a Y direction to achieve precise docking of different exposure areas on the grating substrate and planar splicing of exposure areas of a large area grating; and the first reference grating is separated from the grating substrate and remains stationary; According to the monitoring results of the moiré fringe detection sensor, the controller compensates for the stitching error, controls the optical path difference adjustment device and the beam direction adjustment device, compensates for the phase, tilt and period errors introduced during the stitching process, and ensures the continuity of the fringe phase, period and tilt angle in the exposure area.

9. The method for planar splicing of large-area gratings of a planar splicing large-area grating device according to claim 8, characterized in that: Specifically include: Ensure that the phase, period, and tilt of the reference fringe are the same as those generated by the previous exposure to maintain the phase and posture of the fringe; When a phase error is detected, the plane reflector connected to the piezoelectric ceramic actuator rod moves back and forth to change the optical path of the single-path light to adjust the position of the stripes in the exposure area and achieve phase error compensation; When a grid line period error is detected, the angle between the two exposure beams is adjusted by adjusting the deflection angle of the plane reflector through the biaxial piezoelectric mirror frame, thereby changing the period of the processed stripes and compensating for the grid line period error. When a grid line tilt error is detected, the pitch angle of the reflector is adjusted by the biaxial piezoelectric mirror frame to adjust the angle of the plane where the two exposure beams are located, thereby compensating for the grid line tilt error.

10. The planar splicing large area grating method of the planar splicing large area grating device according to claim 8, characterized in that: Specifically include: The grating substrate to be exposed includes square grid areas forming an n×n grid array, where n is not less than 2. During the process of planar splicing of large-area gratings, the first area is exposed and the initial stripes are recorded by precisely controlling the exposure beam and the reference stripes generated by the reference grating. The non-exposed portion of the grating substrate is shielded. Subsequently, the subsequent areas are precisely aligned through the translation stage, and the remaining areas are exposed while keeping the phase, period and inclination of the reference stripes in the previous area unchanged. During this process, the moiré fringe detection sensor is used to monitor and lock the reference stripes in real time to ensure the continuity and consistency of the stripes between the stitching areas, thereby achieving precise planar stitching of large-area gratings.

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