Plane splicing large-area grating device and method

Abstract

A planar tiled large area grating apparatus and method, the apparatus including a first beam path and a second beam path to generate coherent beams and form an exposure interference field that is received by a grating substrate to be exposed. Two reference gratings are arranged in the device and work cooperatively to generate moire fringes, the moire fringes are monitored by a moire fringe detection sensor, and a controller compensates phase, inclination and periodic errors through an optical path difference adjusting device and a light beam direction adjusting device according to monitoring results. The displacement table device moves the grating substrate and the optical element, and accurate butt joint of different exposure areas is achieved. The first reference grating is fixed, and the second reference grating moves along the Y direction along with the grating substrate. According to the invention, multi-line splicing can be carried out, the limitation of traditional single-line splicing is broken, the flexibility and the application range of grating processing are improved, the diffraction efficiency is improved, the optical path design is simplified, the processing cost is reduced, and a good grating splicing processing effect is ensured.

Description

Technical Field

[0001] The 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 amplification laser systems for inertial confinement fusion, high-resolution spectral analysis of astronomical telescopes, and remote interferometry. Holographic exposure can process holographic gratings through a single exposure, but the exposure aperture size is limited by the size of the optical element because large-aperture, low-aberration collimating lenses are difficult to process and costly.

[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, it is necessary to ensure that the phases of the stripes in different exposure areas are continuous, and the period and inclination are the same during the stitching process. That is, the phase and posture of the exposure strips relative to the substrate are the same between adjacent exposures. BGTURUKHANO proposed a method of using a reference grating to monitor the stitching error to process long strips of stitching gratings. This method is limited to the processing of long strips of gratings and cannot be expanded in another direction. Shi Lei et al. proposed to monitor the possible stitching errors in different exposure areas based on the moiré fringes generated by the latent image grating (photoresist exposed but not developed). 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 the existing grating splicing process, the reference grating method is mainly limited to single-line splicing. In the scheme using latent image grating, although multiple lines can be spliced, the diffraction efficiency of latent image grating is low, the optical path is complex and difficult to adjust.

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

[0006] The main purpose of the present invention is to overcome the defects existing 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 for receiving an exposure interference field;

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

[0012] 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 the phase error;

[0013] A beam direction adjustment device, arranged on the first beam path or the second beam path, for adjusting 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, comprising 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 accurate docking of different exposure areas on the grating substrate and plane splicing of large-area grating exposure areas; and the first reference grating is separated from the grating substrate and remains fixed;

[0016] The controller is used to compensate for the stitching error according to the change of the moiré fringe of the moiré fringe detection sensor, and compensate for the phase, tilt and period errors introduced in the stitching process by controlling the optical path difference adjustment device and the beam direction adjustment device 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 comprises a plane reflector and a biaxial piezoelectric mirror frame or a piezoelectric nano-rotation stage for driving the plane reflector 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 light 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 coplanarly with the grating substrate to be exposed to generate moiré fringes;

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

[0027] The spatial directions of the two exposure beams are adjusted using a beam direction adjustment device to compensate for the grid line period and tilt errors;

[0028] The moiré fringes formed by the interference of the -2nd and -1st order diffracted lights generated by the two exposure beams after passing through the reference grating are monitored by a moiré fringes detection sensor;

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

[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 in the stitching process, and ensures the continuity of the fringe phase, period and tilt angle in the exposure area.

[0031] Furthermore, the method specifically comprises:

[0032] Ensure that the phase, period and inclination of the reference fringe are the same as those of the reference fringe produced by the previous exposure to maintain the phase and attitude of the fringe;

[0033] When a phase error is detected, the plane reflector connected to the piezoelectric ceramic actuator rod moves forward and backward to change the optical path of the single-path light to adjust the stripe position in the exposure area and achieve compensation for the phase error.

[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 stripes to be processed and realizing compensation for the grid line period error;

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

[0036] Furthermore, the method specifically comprises:

[0037] The grating substrate to be exposed includes square grid areas forming an n×n square grid array, where n is not less than 2. In the process of planar splicing of large-area gratings, by precisely controlling the exposure beam and the reference stripes generated by the reference grating, the first area is first exposed and the initial stripes are recorded under the condition of shielding the non-exposed part of the grating substrate; then, 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 of the previous area unchanged; in 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 splicing areas, so as to achieve precise planar splicing of large-area gratings.

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

[0039] The present invention provides a device and method capable of realizing large-area grating plane splicing. The method effectively monitors and compensates for phase, tilt and period errors in the splicing process by using two reference gratings to work in coordination with a grating substrate. Compared with the prior art, the present invention can process spliced ​​gratings of any number of rows and columns, breaking the limitations of previous technologies in the splicing direction and improving the flexibility and application scope of processing. In addition, the reference grating used in the present invention has high diffraction efficiency, simplifies the optical path design, and makes the optical path adjustment simpler and faster. Through the technical means of repeatedly recording reference stripes 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. Finally, the grating processed by 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, which significantly improves the performance and accuracy of the spliced ​​grating.

[0040] The present invention can use reference gratings to monitor errors to process spliced ​​gratings of any number of rows and columns, and can perform multi-row splicing. The reference grating has high diffraction efficiency, a simple optical path, and simple optical path adjustment. The present invention detects and compensates for phase, tilt, and period errors, and the processed spliced ​​grating has a continuous diffraction wave surface. The solution proposed by the present invention can ensure that the errors of the spliced ​​gratings can be monitored and compensated in each area, thereby ensuring a good grating splicing processing effect.

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

[0042] Figure 1 It is a schematic structural diagram 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 splicing 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 a -1 order diffraction wave surface 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 and application of the present invention.

[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 fixing as well as for coupling or communication.

[0048] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0049] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0050] See also Figure 1The embodiment of the present invention provides a planar splicing large-area grating device, comprising: a first beam path and a second beam path, for providing a coherent 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 beam path, for adjusting the optical path difference between the two exposure beams to compensate for the phase error; a beam direction adjustment device, arranged on the first beam path or the second beam path, for adjusting the spatial direction of the exposure beam to compensate for the grating line period and tilt error; a moiré fringe detection sensor, for monitoring the moiré fringes formed by the two exposure 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 accurate 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 fixed; a controller is used to compensate for the splicing error according to the change of the moiré fringe of the moiré fringe detection sensor, and 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: introducing two reference gratings to generate moiré fringes, one of which is fixed and the other moves with the grating substrate, so that the system can 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 the phase error and the grating line period and tilt error respectively, while the moiré fringe detection sensor monitors the splicing error in real time, and the controller dynamically adjusts the beam path according to these data to ensure the continuity of the fringe phase, period and tilt angle of the exposure area. During the working process, by recording the 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 wave surface. This mechanism not only improves the splicing efficiency, but also significantly improves the continuity of the diffraction wavefront of the spliced ​​grating, so that the processed grating has an excellent performance of -1 order diffraction wavefront PV value as low as 0.125λ and 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 with traditional technology, the device and method of the present invention not only breaks through the size limitation of optical elements, reduces the processing difficulty and cost, but also improves the diffraction efficiency, simplifies the optical path design, and can perform multi-row splicing, making the splicing processing of large-area gratings more flexible, efficient and precise.

[0052] See also Figure 1 In some embodiments, the optical path difference adjustment device includes a plane mirror (second plane mirror 22) and a piezoelectric ceramic actuator rod 23 or a piezoelectric nano-displacement stage for driving the plane mirror to move. The beam direction adjustment device includes a plane mirror (fourth plane mirror 18) and a biaxial piezoelectric mirror frame 17 or a piezoelectric nano-rotation stage for driving the plane mirror to rotate. The moiré fringe detection sensor includes a CCD camera 14.

[0053] See also Figure 1The embodiment of the present invention also provides a method for plane splicing large-area gratings using the plane splicing large-area grating device, comprising the following processes: 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, so as to provide a coherent light beam and form an exposure interference field; using a first reference grating 10 and a second reference grating 12 to be arranged coplanarly 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 the grating line period and tilt error; using a moiré fringe detection sensor to monitor the optical path difference between the two exposure beams through the reference light beam The invention relates to a method for detecting moiré fringes formed by the interference of -2 and -1 order diffraction lights generated behind the grating; an operating stage device, wherein the first stage moves the relevant optical elements in the X direction to change the position of the exposure area, and the second stage moves the grating substrate and the second reference grating 12 in the Y direction to achieve the precise docking of different exposure areas on the grating substrate and the planar splicing of the large-area grating exposure area; and the first reference grating 10 is separated from the grating substrate and remains fixed; according to the monitoring result of the moiré fringe detection sensor, the splicing error is compensated by the controller, and the optical path difference adjustment device and the beam direction adjustment device are controlled to compensate for the phase, tilt and period errors introduced in the splicing process, so as to ensure the continuity of the fringe phase, period and tilt angle in the exposure area.

[0054] See also Figure 1 In some embodiments, the method specifically includes: ensuring that the phase, period and inclination 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 by 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 phase error compensation; 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 light beams, thereby changing the period of the stripes to be processed to achieve grid line period error compensation; 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 light beams are located to achieve grid line tilt error compensation.

[0055] See also Figures 2a to 2jIn some embodiments, the method specifically includes: the grating substrate to be exposed includes square grid areas forming an n×n square grid array, where n is not less than 2; in the process of plane stitching of large-area gratings, by precisely controlling the exposure beam and the reference stripes generated by the reference grating, firstly, the first area is exposed and the initial stripes are recorded under the condition of shielding the non-exposed part of the grating substrate; then, the subsequent areas are precisely aligned by the translation stage, and the remaining areas are exposed while keeping the phase, period and inclination of the reference stripes of the previous area unchanged; in this process, the reference stripes are monitored and locked in real time by using a moiré fringe detection sensor to ensure the continuity and consistency of the stripes between the stitching areas, so as to achieve precise plane stitching of large-area gratings.

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

[0057] Planar splicing device for large-area gratings

[0058] Figure 1 The schematic structural diagram 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 prism 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 11 to be exposed, a first reference grating 10, a second reference grating 12, a first displacement stage 16, a second displacement stage 13, a CCD camera 14, a piezoelectric ceramic actuator rod 23, and a biaxial piezoelectric mirror frame 17.

[0059] After the two exposure beams pass through the reference grating, the -2 and -1 order diffraction lights will interfere to form moiré fringes. The generated moiré fringes are monitored by a CCD camera. A fixed reference grating (separated from the substrate) is placed in front of the substrate S. When splicing in the x direction, the positions of the substrate and the reference grating are not moved, and the first displacement stage simultaneously drives the third plane reflector, the fourth plane reflector and the CCD camera to move in the x direction. The movement of the third plane reflector and the fourth plane reflector can change the position of the exposure area. Another reference grating is fixed on the side of the grating substrate to be exposed (the substrate and the reference grating are fixed on the second displacement stage at the same time). When splicing in the y direction, the second displacement stage drives the substrate and the reference grating to move in the y direction at the same time. The piezoelectric ceramic actuator rod is a piezoelectric push rod used to adjust the phase error. The fourth plane reflector is mounted on the dual-axis piezoelectric mirror frame to compensate for the grating line period and tilt errors.

[0060] The phase, tilt and period errors introduced in the stitching process will cause the phase tilt and period changes of the reference fringes generated by the reference grating. In order to ensure that the phase and posture of the fringes are the same, it is only necessary to ensure that the phase and period tilt of the reference fringes are unchanged from those of the reference fringes generated by the previous exposure.

[0061] The stitching error is compensated according to the monitored reference stripes. A piezoelectric ceramic actuator rod is used to connect the second plane reflector. The piezoelectric push rod moves forward and backward to drive the second plane reflector to move forward and backward. The stripe position 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. The pitch angle and deflection angle of the reflector are adjusted using a biaxial piezoelectric mirror frame. The angle between the two exposure beams is changed by adjusting the deflection of a beam of light. When the angle between the two exposure beams changes, 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 of light 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 generated by the first reference grating, called the initial fringe 1-1. Then expose area 1 while locking the reference fringe (ensuring that the fringe phase attitude remains unchanged).

[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 stripes generated by the first reference grating with the initial stripes 1-1 recorded in the first step (i.e., the phase, period, and tilt are all the same). Then expose area 2 while locking the reference stripes.

[0065] Step 3: Translate the first stage to align the exposure area with area 3. At this time, the two reference gratings appear in the exposure area at the same time. When the substrate is blocked, turn on the exposure beam and align the reference stripes generated by the first reference grating with the initial stripes 1-1 and lock and record the reference stripes generated by the second reference grating, which is called initial stripes 2. Use the reference stripes of the first reference grating to lock with the initial stripes 1-1 and expose area 3.

[0066] Step 4: Translate the second stage and align the exposure area with area 6. While shielding the substrate, turn on the exposure beam and align and lock the reference stripes generated by the second reference grating with the initial stripes 2 and record the reference stripes generated by the first reference grating, which are called initial stripes 1-2. Use the reference stripes of the first reference grating to lock with the initial stripes 1-2 and 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 and expose area 5 while locking the reference stripes.

[0068] Step 6: translate the first 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 and expose area 4 while locking the reference stripes.

[0069] Step 7: Translate the first and second translation stages to align the exposure area onto area 9. While shielding the substrate, turn on the exposure beam and align and lock the reference stripes generated by reference grating 2 with initial stripes 2 and record the reference stripes generated by reference grating 1, referred to as initial stripes 1-3. Use the reference stripes of reference grating 1 to lock with initial stripes 1-3 and 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 and expose area 8 while locking the reference stripes.

[0071] Step 9: translate the first 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 and expose area 7 while locking the reference stripes.

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

[0073] In different embodiments, different regions may be exposed in any order in the stitching method, such as first performing step six to expose region 4, and then performing step five to expose region 5.

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

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

[0076] In different embodiments, the period and tilt angle may 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 structure of the optical path is changed to allow the light beam to irradiate downward.

[0078] A wavefront error detection method for 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] λ 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 has jumps. From the interference pattern, we can observe the fringe misalignment caused by the wavefront misalignment: the left fringe and the right fringe are not connected at the junction. When there is a grid line period error, the diffraction wavefront pattern is deflected, and the fringe period change can be observed from the interference pattern. When there is a grid line tilt error, the diffraction wavefront pattern is deflected, and the fringe tilt change can be observed from the interference pattern.

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

[0084]

[0085] When there is a grid line tilt error, the diffraction wave surface will tilt. When the grid line tilt error is Δγ, the inclination angle δ of the diffraction wave surface 1 for:

[0086] δ 1 =arctan(tan2Δγ*sinθ)

[0087] Where θ is the grating placement angle.

[0088] When there is a grid line period error, the diffraction wave surface will tilt in another direction. When the grid line period error is Δd, the inclination angle δ of the diffraction wave surface is 2 for:

[0089]

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

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

[0092] The planar splicing large-area grating device of the present invention can detect and compensate for phase, tilt and period errors. The processed splicing grating diffraction wave surface is continuous. The present invention can ensure that the splicing grating error can be monitored and compensated in each area, and can ensure good effect.

[0093] The grating -1 order diffraction wavefront PV value produced by the planar splicing large area grating device of the present invention is 0.125λ, and the RMS is 0.022λ. 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%. The -1 order diffraction wavefront diagram is as follows Figure 4 shown.

[0094] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. 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 can be made herein without departing from the scope of protection of the patent application.

Claims

1. A planar splicing large area grating device, It is 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 for receiving an exposure interference field; A first reference grating and a second reference grating 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 the phase error; A beam direction adjustment device, arranged on the first beam path or the second beam path, for adjusting 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, comprising 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 accurate docking of different exposure areas on the grating substrate and plane splicing of large-area grating exposure areas; and the first reference grating is separated from the grating substrate and remains fixed; The controller is used to compensate for the stitching error according to the change of the moiré fringe of the moiré fringe detection sensor, and compensate for the phase, tilt and period errors introduced in the stitching process by controlling the optical path difference adjustment device and the beam direction adjustment device to ensure the continuity of the fringe phase, period and tilt angle in the exposure area.

2. The planar splicing large area grating device as claimed in claim 1, It is characterized in that The optical path difference adjustment device comprises a plane reflector and a piezoelectric ceramic actuating rod or a piezoelectric nano displacement stage for driving the plane reflector to move.

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

4. The planar splicing large area grating device according to any one of claims 1 to 3, It is 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 4, It is 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 5, It is characterized in that The two exposure light beams generate -2 and -1 order diffraction light interference to form moiré fringes after passing through the reference grating.

7. The planar splicing large area grating device according to any one of claims 1 to 6, It is 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, It is 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 coplanarly with the grating substrate to be exposed to generate moiré fringes; The optical path difference adjusting device is used to adjust the optical path difference between the two exposure light beams to compensate for the phase error; The spatial directions of the two exposure beams are adjusted using a beam direction adjustment device to compensate for the grid line period and tilt errors; The moiré fringes formed by the interference of the -2nd and -1st order diffracted lights generated by the two exposure beams after passing through the reference grating are monitored by a moiré fringes detection sensor; An operating stage device is provided, wherein the first stage moves the related optical elements in the X direction to change the position of the exposure area, and the second stage moves the grating substrate and the second reference grating in the Y direction to achieve accurate docking of different exposure areas on the grating substrate and plane splicing of large-area grating exposure areas; and the first reference grating is separated from the grating substrate and remains fixed; 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 in the stitching process, and ensures the continuity of the fringe phase, period and tilt angle in the exposure area.

9. The planar splicing large area grating method of the planar splicing large area grating device as claimed in claim 8, It is characterized in that Specifically include: Ensure that the phase, period and inclination of the reference fringe are the same as those of the reference fringe produced by the previous exposure to maintain the phase and attitude of the fringe; When a phase error is detected, the plane reflector connected to the piezoelectric ceramic actuator rod moves forward and backward to change the optical path of the single-path light to adjust the stripe position in the exposure area and achieve compensation for the phase error. 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 stripes to be processed and realizing compensation for the grid line period error; When a grid line tilt error is detected, the pitch angle of the reflector is adjusted by a biaxial piezoelectric mirror frame to adjust the angle of the plane where the two exposure beams are located, thereby achieving compensation for the grid line tilt error.

10. The planar splicing large area grating method of the planar splicing large area grating device as claimed in claim 8, It is characterized in that Specifically include: The grating substrate to be exposed includes square grid areas forming an n×n square grid array, where n is not less than 2. In the process of plane splicing of large-area gratings, by precisely controlling the exposure beam and the reference stripes generated by the reference grating, the first area is first exposed and the initial stripes are recorded under the condition of shielding the non-exposed part of the grating substrate; 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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