Large-size special-shaped plane grating surface type measuring device and method

Abstract

The invention provides a large-size special-shaped plane grating surface type measuring device. The large-size special-shaped plane grating surface type measuring device comprises an interferometer, an adjusting and positioning mechanism corresponding to the position of the interferometer and a fixing frame arranged on the adjusting and positioning mechanism. Wherein the fixing frame is provided with a clamping groove matched with a to-be-measured grating, and the to-be-measured grating is clamped in the clamping groove and is positioned through a positioning piece on the fixing frame; in addition, the to-be-measured grating is matched with the fixing frame through the adjusting and positioning mechanism to carry out placing posture adjustment. According to the large-size special-shaped plane grating surface type measuring device and method, the surface type measuring precision of the large-size special-shaped plane grating can be effectively improved, and the safety of the plane grating can be effectively ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision displacement measurement, and more specifically, to a device and method for measuring the surface profile of a large-sized special-shaped plane grating. Background Art

[0002] In high-end lithography machines, the ultra-precision motion stage is the core subsystem. The ultra-precision motion stage requires a high-precision plane grating displacement measurement system as support, and the plane grating is the core component of the core subsystem of the lithography machine.

[0003] With the development of photolithography, people's requirements for the performance of plane gratings are constantly increasing. Correspondingly, the difficulty of measuring the technical indicators of plane gratings will also increase. The surface shape of optical components refers to the surface shape accuracy of the component surface. It is one of the important technical indicators of optical components (such as plane gratings) and is related to the actual performance of optical components. Under normal circumstances, skilled technicians generally use Fizeau interferometer to measure the surface shape of optical components.

[0004] However, for the surface measurement of large-aperture plane gratings, due to the large size of the grating, a large-aperture horizontal interferometer is required to measure it, that is, the plane grating is placed upright in front of the interferometer standard mirror during the test. However, since the plane grating is wide and thick, and does not belong to the standard shape of circle or rectangle (it belongs to a special-shaped structure), it is easily affected by the pressure from the fixture during the clamping measurement, as well as the influence of gravity, resulting in a large surface accuracy error, so it is necessary to specially develop a low-stress test fixture that matches large-size special-shaped gratings.

[0005] In addition, the surface of large-sized plane gratings is extremely fragile, and direct contact with hard objects is prohibited. There is no area on the edge of the plane grating that can be touched and clamped. In addition, due to assembly process requirements, there are also high requirements for the surface roughness of the back of the grating. These restrictions require that when developing large-sized plane grating tooling, the issue of protecting the safety of the grating must also be considered.

[0006] In summary, for large-size, large-width-to-thickness-ratio special-shaped plane gratings, there is an urgent need for a large-size grating tooling that can effectively ensure the safety of the grating and significantly improve the grating surface measurement accuracy. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a large-sized special-shaped plane grating surface measurement device and method, which can effectively improve the surface measurement accuracy of large-sized special-shaped plane gratings and effectively ensure the safety of plane gratings.

[0008] The present invention provides a large-size special-shaped plane grating surface measurement device, comprising an interferometer, an adjustment and positioning mechanism corresponding to the position of the interferometer, and a fixed frame arranged on the adjustment and positioning mechanism; wherein a card slot adapted to the grating to be measured is provided on the fixed frame, the grating to be measured is clamped in the card slot and positioned by a positioning piece on the fixed frame; and the grating to be measured is adjusted in placement posture by the adjustment and positioning mechanism in cooperation with the fixed frame; and the interferometer is used to perform surface measurement on the grating to be measured with the adjusted placement posture.

[0009] In addition, a preferred solution is that the adjustment and positioning mechanism includes an adjustment seat and a fixed seat arranged on the adjustment seat, a clamping knob is arranged on the fixed seat, and the fixed frame is squeezed and fixed on the fixed seat by the clamping knob; and,

[0010] The fixed seat is placed on the adjustment seat in an adjustable posture.

[0011] In addition, a preferred solution is that the positioning member includes a front chamfering block and a rear chamfering block arranged on the front and rear sides of the fixed frame and corresponding to the front and rear chamfers of the grating to be measured, and the front chamfering block and the rear chamfering block fix the grating to be measured by contacting and supporting the chamfer.

[0012] In addition, a preferred solution is that the positioning member further includes a wedge block arranged at the upper end of the fixing frame and corresponding to the position of the side groove of the grating to be measured, and the wedge block fixes the grating to be measured by being inserted into the side groove.

[0013] In addition, a preferred solution is that the hardness of the fixing frame, the hardness of the front chamfered pressing block, the hardness of the rear chamfered pressing block and the hardness of the wedge block are all lower than the hardness of the grating to be measured.

[0014] In addition, a preferred solution is that the fixing frame and the front chamfered pressing block are made of Teflon, and the wedge block and the rear chamfered pressing block are made of polyetheretherketone.

[0015] In addition, a preferred solution is to provide a limit screw on the top of the fixing frame, and the limit screw is pressed and fixed to the upper side of the grating to be measured.

[0016] In addition, a preferred solution is that a rubber pad is provided at the end of the limit screw, and the limit screw is pressed and fixed to the upper side of the grating to be measured through the rubber pad.

[0017] On the other hand, the present invention also provides a large-sized special-shaped plane grating surface measurement method, which uses the aforementioned large-sized special-shaped plane grating surface measurement device for measurement, and the method comprises:

[0018] The grating to be measured is mounted in the card slot of the fixing frame and fixed by a positioning piece;

[0019] Place the fixed frame with the grating to be measured fixed on the adjustment and positioning mechanism, and tighten it with the tightening knob;

[0020] Loosen the positioning member to make the grating to be measured stand upright in the fixing frame, and press the top of the grating to be measured by means of a limit screw;

[0021] The positioning mechanism is used to adjust the placement posture of the grating to be measured in front of the interferometer, and the interferometer is used to perform surface measurement on the grating to be measured.

[0022] In addition, a preferred solution is that, in the process of placing the fixed frame with the grating to be measured fixed thereon on the adjustment and positioning mechanism and pressing it by means of the pressing knob:

[0023] The fixing frame is extended to both sides of the adjusting and positioning mechanism so that the pressure applied by the pressing knob to the fixing frame is perpendicular to the surface of the fixing frame.

[0024] Compared with the prior art, the large-size special-shaped plane grating surface measurement device and method according to the present invention have the following beneficial effects:

[0025] By setting a set of fixing fixtures for the large-sized special-shaped plane grating, the grating can be subjected to only the pressure of gravity and the top clamping screw during the test. At this time, the grating can be considered to be in a low stress state, thereby effectively reducing the interference of stress on the surface test of the large-sized plane grating; in addition, the grating clamping conditions of the large-sized special-shaped plane grating surface measurement device provided by the present invention can be reproduced, and the test environment can be repeated, so that the surface test results can have good repeatability and reproducibility;

[0026] In addition, since the large-size special-shaped plane grating surface measurement device provided by the present invention fully considers the fragility of the grating, the grating will basically not be damaged during the test process.

[0027] In order to achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later and are particularly pointed out in the claims. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] By referring to the following description and claims in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easier to understand. In the accompanying drawings:

[0029] Figure 1 An axonometric diagram of an adjustment and positioning mechanism provided according to an embodiment of the present invention;

[0030] Figure 2 A front axonometric view of a grating of a fixing frame provided according to an embodiment of the present invention;

[0031] Figure 3 A rear axonometric view of a grating of a fixing frame provided according to an embodiment of the present invention;

[0032] Figure 4 A schematic diagram of a limit screw provided according to an embodiment of the present invention;

[0033] Figure 5 The dimension drawing of the grating to be tested;

[0034] Figure 6 It is a schematic diagram of PV value;

[0035] Figure 7 The displacement cloud diagram of each 2N pressure (the U1 direction is consistent with the X-axis direction);

[0036] Figure 8 When 2N pressure is applied, the data excludes the simulation data of the inclined rear face;

[0037] Fig. 9 The displacement cloud diagram of each 5N pressure (the U1 direction is consistent with the X-axis direction);

[0038] Fig.10 When 5N pressure is applied, the simulation data of the inclined rear face is removed;

[0039] Fig.11 A structural diagram of a compression knob is shown.

[0040] Figure numerals: fixed seat 1, adjustment seat 2, clamping knob 3, fixed frame 4, wedge block 5, front chamfer pressure block 6, handle 7, rear chamfer pressure 8, limit screw 9, knob 11, pressure block 12, spring 13, guide column 14.

[0041] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0042] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0043] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] The structure of the large-size special-shaped plane grating surface measurement device provided by the present invention is described in detail below. Figure 1 The isometric structure of the adjustment and positioning mechanism provided according to an embodiment of the present invention is shown. Figure 2 The front axonometric structure of the grating of the fixed frame provided by the embodiment of the present invention is shown. Figure 3 The grating backside axonometric structure of the fixing frame provided in the embodiment of the present invention is shown. Figure 4 A schematic diagram of a limit screw provided according to an embodiment of the present invention is shown. Figure 5 The figure shows the dimensions of the grating to be tested.

[0045] Combined with the figure Figures 1 to 5 It can be seen that the large-sized special-shaped plane grating surface measurement device provided by the present invention mainly includes an interferometer for measuring the surface shape of the large-sized special-shaped plane grating (usually a large-aperture horizontal interferometer, such as a Fizeau interferometer), an adjustment and positioning mechanism corresponding to the horizontal position of the interferometer, and a fixed frame 4 arranged on the adjustment and positioning mechanism for loading the grating to be measured (i.e., the large-sized special-shaped plane grating).

[0046] Specifically, a card slot that matches the shape of the grating to be measured is provided on the fixed frame 4 (the inner contour of the card slot is the same as the outer contour of the grating to be measured). In actual use, the grating to be measured is mounted in the card slot to achieve loading and is fixed in position by a preset positioning piece on the fixed frame 4; after the grating to be measured is fixed on the adjustment and positioning mechanism by the fixed frame 4, the grating to be measured can be adjusted in position by the adjustment and positioning mechanism in cooperation with the fixed frame 4, and the interferometer is used to perform surface measurement on the grating to be measured with the adjusted position, thereby realizing the surface measurement of the grating to be measured under different positional positions by the interferometer. It should be noted that in the actual measurement process, the large-aperture horizontal interferometer and the adjustment and positioning mechanism for carrying the grating to be measured need to be placed on a vibration-isolating optical platform to eliminate the interference of vibration on the surface test.

[0047] In addition, the adjustment and positioning mechanism may include an adjustment seat 2 and a fixed seat 1 arranged on the adjustment seat 2, a clamping knob 3 is arranged on the fixed seat 1, and the fixed frame 4 is squeezed and fixed on the fixed seat 1 by the clamping knob 3; in actual use, the posture of the fixed seat 1 is adjusted by the adjustment seat 2 to adjust the placement posture of the grating, and cooperate with the interferometer to realize the surface measurement of the grating to be measured.

[0048] It should be noted that the fixing seat 1 includes two fixing parts arranged on the adjustment seat 2, and the two sides of the fixing frame 4 are detachably fixed to the two fixing parts through the clamping knobs 3; and, in order to improve the stability of the fixing frame 4, each fixing part is provided with multiple (usually three) clamping knobs 3, and the distances between adjacent clamping knobs 3 are equal, so as to achieve fixation of the fixing frame 4 at different height positions.

[0049] In addition, in order to facilitate the staff to manually adjust the fixed frame 4 (such as position movement, rotation, etc.), a handle 7 can be provided on one side of the fixed frame 4. In actual use, the fixed frame 4 can be adjusted through the handle 7.

[0050] In a preferred embodiment of the present invention, in order to ensure that the grating to be measured is fixed to the fixed frame 4 under the premise of ensuring the safety of the grating to be measured, the positioning member may include a front chamfering block 6 and a rear chamfering block 8 arranged on the front and rear sides of the fixed frame 4 and corresponding to the front and rear chamfers of the grating to be measured. The front chamfering block 6 and the rear chamfering block 8 fix the grating to be measured by squeezing the chamfer.

[0051] Specifically, the chamfered parts of the plane grating are contacted and fixed with the front chamfer block 7 and the rear chamfer block 6 respectively, so as not to touch the fragile grating surface and ensure sufficient safety and stability. It should be noted that in the process of installing the grating into the fixed frame 4, the front chamfer block and the rear chamfer block are in contact with the grating chamfer; while in the test process, the front chamfer block and the rear chamfer block are not in contact with the grating chamfer, so as to minimize the stress introduced during the surface test process. It should be further explained that large-sized special-shaped plane gratings are usually made of microcrystalline glass as a substrate, and the chamfer position of the grating is usually specially treated to have higher strength and is not an optical functional component of the grating. Therefore, the position of the grating to be measured can be fixed by setting the front chamfer block 6 and the rear chamfer block 8, and the surface measurement accuracy of the grating to be measured will not be affected.

[0052] Furthermore, the side groove of the grating to be measured also has similar properties to the chamfer, so the positioning member can also include a wedge 5 arranged at the upper end of the fixing frame 4 and corresponding to the position of the side groove of the grating to be measured, and the wedge 5 is inserted into the side groove and fixed to the fixing frame to achieve the fixing effect on the grating. The provision of the wedge 5 can further ensure the safety of the grating to be measured, and will not affect the surface measurement accuracy of the grating to be measured.

[0053] It should be noted that in order to effectively prevent the grating to be measured from being squeezed and damaged at the contact position with foreign objects, thereby affecting the surface measurement accuracy and even rendering the entire grating to be measured unusable, it is necessary to set the hardness of the fixed frame 4, the hardness of the front chamfered pressure block 6, the hardness of the rear chamfered pressure block 8 and the hardness of the wedge block 5 to be lower than the hardness of the grating to be measured (especially the hardness of the position where the grating to be measured is in direct contact with various components).

[0054] It should be further explained that, under normal circumstances, the grating surface (front side) of a large-size grating cannot be in direct contact with the hardware, other surfaces cannot have scratches, and the assembly of the grating also has requirements for the back side (try not to have direct contact with the hardware). Therefore, the fixed frame 4 and the front chamfered block 6 can be made of Teflon, and the wedge block 5 and the rear chamfered block 8 can be made of polyetheretherketone.

[0055] Based on the extremely low friction coefficient of Teflon and its lubricating property, the fixing frame 4 and the front chamfered pressing block 6 are made of Teflon, which can effectively protect the safety of the front side of the grating to be measured. Based on the mechanical characteristics and self-lubricating characteristics of polyetheretherketone, the wedge block 5 and the rear chamfered pressing block 8 are made of polyetheretherketone, which can directly contact the side and back of the grating without scratching the grating, and can effectively protect the safety of the side and back of the grating to be measured.

[0056] It should be noted that when the grating to be tested is placed in the fixing frame 4, in order not to block the grating surface and back, the grating to be tested is fixed by using the chamfer of the grating using the pressing blocks in front and behind the fixing frame 4. At the same time, a wedge block 5 made of polyetheretherketone is designed on the upper end of the fixing frame 4 to further fix the grating to be tested using the side groove. This design can make the grating surface and back completely exposed, without affecting the surface test of the grating to be tested, and even if the Teflon fixing frame 4 is deformed, it will not fall off easily.

[0057] In addition, a limit screw 9 is provided at the top of the fixed frame 4, and the limit screw 9 is pressed and fixed with the upper side of the grating to be measured. In actual use, after the fixed frame 4 is fixed to the adjustment and positioning mechanism by the clamping knob 3, the fixing screws of the front and rear chamfered pressure blocks 8 and the wedge block 5 on the fixed frame 4 that are in direct contact with the grating to be measured can be loosened by half a circle to one circle, so that there is a gap between the pressure blocks (front and rear chamfered pressure blocks 8), the wedge block 5 and the grating, so that the grating stands almost freely at the bottom of the fixed frame 4, and finally the limit screw 9 on the top of the fixed frame 4 is tightened to position the grating to be measured again. At this time, the grating is only subjected to the weak pressure of the top limit screw 9 to stabilize the posture, which is a low-stress state. The grating fixing assembly can adjust the placement posture of the grating in front of the interferometer to complete the measurement.

[0058] It should be noted that a rubber pad is provided at the end of the limit screw 9, and the limit screw 9 is pressed and fixed to the upper side of the grating to be measured by the rubber pad. By providing a rubber pad to wrap the part where the screw head directly contacts the grating side, the stress between the limit screw 9 and the upper side of the grating to be measured can be effectively reduced, thereby preventing the grating to be measured from being scratched.

[0059] In addition, it should be noted that after the grating is installed in the fixing frame 4, it is placed in the fixing adjustment seat 2, and the fixing frame 4 is pressed with six pressing knobs 3. Since the six pressing knobs 3 will exert a large pressure on the grating fixing frame 4, in order to ensure the low stress state of the grating during the test, the fixing frame 4 is extended to both sides so that the pressure exerted by the pressing knobs 3 on the fixing frame 4 is perpendicular to the surface of the fixing frame 4, which will not cause deformation of the fixing frame 4, and thus the pressure will not affect the low stress state of the grating.

[0060] On the other hand, in order to further illustrate the working principle and performance of the large-sized special-shaped plane grating surface measurement device provided by the present invention, the present invention also provides a large-sized special-shaped plane grating surface measurement method, which uses the aforementioned large-sized special-shaped plane grating surface measurement device for measurement, and the method comprises:

[0061] The grating to be tested is mounted in the card slot of the fixing frame 4 and fixed by a positioning piece;

[0062] Place the fixed frame 4 with the grating to be measured fixed on the adjustment and positioning mechanism, and tighten it by the tightening knob 3;

[0063] The positioning member is loosened to allow the grating to be measured to stand in the fixing frame 4, and the top of the grating to be measured is squeezed by the limit screw 9;

[0064] The positioning mechanism is used to adjust the placement posture of the grating to be measured in front of the interferometer, and the interferometer is used to measure the surface shape of the grating to be measured.

[0065] Specifically, when placing the fixed frame 4 with the grating to be measured on the adjustment and positioning mechanism and tightening it through the tightening knob 3: the fixed frame 4 is extended to both sides of the adjustment and positioning mechanism so that the pressure applied by the tightening knob 3 to the fixed frame 4 is perpendicular to the surface of the fixed frame 4.

[0066] It should be noted that during the test (measurement) process, the main factors affecting the surface shape of the grating to be measured are the clamping force of the tooling and the angle between the grating surface and the direction of gravity. The grating is in the fixed frame 4, and when the fixed frame 4 is installed in the fixed adjustment seat 2, the positioning side is placed upright on the lower surface of the fixed frame 4. Since there is an angle between the grating surface and the direction of gravity, in order to prevent the grating from tipping over and touching the wedge 5 to introduce external force, the grating is checked for tipping. The grating dimensions during the actual measurement process are as follows: Figure 5 As shown, γ is the minimum tilt angle of the grating. Meet the use requirements. Since the interferometer field of view range is ±0.5°, the angle is increased by 20%, and 2N and 5N pressures are applied to the contact area between the upper surface of the grating and the limit element respectively, and the angle of 0.6° between the grating surface and the gravity direction is analyzed.

[0067] Table 1 Data on the change of surface shape caused by clamping force and gravity

[0068]

[0069] The static analysis results under 2N pressure conditions are as follows Figure 7 / Figure 8 The static analysis results under 5N pressure conditions are shown in Fig. 9 / Fig.10 shown.

[0070] Combined with Table 1, Figures 6 to 10 It can be seen that by adjusting the clamping force of the limit screw, the purpose of low-stress surface testing of large-sized special-shaped plane gratings can be achieved.

[0071] It should be noted that Figure 6In the figure, the solid line represents the ideal state in actual working conditions, where there is a slight tilt but the surface shape is not affected by the clamping force and gravity, which does not exist in reality; the dotted line represents the actual state under the dual low stress of clamping force and gravity. The part with the largest change between the two is the PV value of the surface shape caused by low stress, which is the meaning of the "PV" value in Table 1.

[0072] Specifically, Fig.11 is the structural diagram of the pressing knob. Fig.11 It can be seen that the clamping knob includes a knob 11, a clamping block 12, a spring 13 and a guide column 14, a total of 4 parts. Tightening the knob 11 can push the clamping block 12 downward, and after being rotated to a certain extent, the right side of the clamping block 12 can apply pressure to the fixed frame 4, thereby fixing the fixed frame 4. The spring 13 ensures that when the knob is rotated in the opposite direction to loosen the clamping block 12, the clamping block 12 can be reset; the function of the guide column 14 is to prevent the clamping block 12 from rotating when the knob 11 is rotated, so that the clamping block 12 can move vertically up and down.

[0073] As above Figures 1 to 11 The large-size profiled plane grating surface profile measuring device and method according to the present invention are described by way of example. However, those skilled in the art should understand that various improvements can be made to the large-size profiled plane grating surface profile measuring device and method proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A large-size special-shaped plane grating surface measurement device, characterized in that: It includes an interferometer, an adjustment and positioning mechanism corresponding to the position of the interferometer, and a fixing frame arranged on the adjustment and positioning mechanism; wherein, A slot adapted to the grating to be measured is provided on the fixing frame, and the grating to be measured is mounted in the slot and positioned by a positioning piece on the fixing frame; and The grating to be measured is adjusted in placement posture by the adjustment and positioning mechanism in cooperation with the fixing frame; The interferometer is used to measure the surface shape of the grating to be measured with its posture adjusted.

2. The large-size special-shaped plane grating surface measurement device according to claim 1, characterized in that: The adjustment and positioning mechanism comprises an adjustment seat and a fixing seat arranged on the adjustment seat, a pressing knob is arranged on the fixing seat, and the fixing frame is pressed and fixed on the fixing seat by the pressing knob; and The fixed seat is placed on the adjustment seat in an adjustable posture.

3. The large-size special-shaped plane grating surface measurement device according to claim 1, characterized in that: The positioning member includes a front chamfer pressing block and a rear chamfer pressing block arranged on the front and rear sides of the fixing frame and corresponding to the front and rear chamfers of the grating to be measured. The front chamfer pressing block and the rear chamfer pressing block fix the grating to be measured by squeezing the chamfer.

4. The large-size special-shaped plane grating surface measurement device according to claim 2, characterized in that: The positioning member further comprises a wedge block arranged at the upper end of the fixing frame and corresponding to the position of the side groove of the grating to be measured, and the wedge block fixes the grating to be measured by squeezing the side groove.

5. The large-size special-shaped plane grating surface measurement device according to claim 4, characterized in that: The hardness of the fixing frame, the hardness of the front chamfered pressing block, the hardness of the rear chamfered pressing block and the hardness of the wedge block are all lower than the hardness of the grating to be measured.

6. The large-size special-shaped plane grating surface measurement device according to claim 5, characterized in that: The fixing frame and the front chamfered pressing block are made of Teflon, and the wedge block and the rear chamfered pressing block are made of polyetheretherketone.

7. The large-size special-shaped plane grating surface measurement device according to any one of claims 1 to 6, characterized in that: A limit screw is arranged on the top of the fixing frame, and the limit screw is pressed and fixed to the upper side of the grating to be measured.

8. The large-size special-shaped plane grating surface measurement device according to claim 7, characterized in that: A rubber pad is arranged at the end of the limit screw, and the limit screw is pressed and fixed to the upper side of the grating to be measured through the rubber pad.

9. A method for measuring the surface profile of a large-sized irregular plane grating, characterized in that: The large-size special-shaped plane grating surface profile measuring device according to any one of claims 1 to 8 is used for measurement, and the method comprises: The grating to be measured is mounted in the card slot of the fixing frame and fixed by a positioning piece; Place the fixed frame with the grating to be measured fixed on the adjustment and positioning mechanism, and tighten it with the tightening knob; Loosen the positioning member to make the grating to be measured stand in the fixing frame, and press the top of the grating to be measured by means of a limit screw; The positioning mechanism is used to adjust the placement posture of the grating to be measured in front of the interferometer, and the interferometer is used to perform surface measurement on the grating to be measured.

10. The large-size special-shaped plane grating surface measurement method according to claim 9, characterized in that: When placing the fixed frame with the grating to be measured on the adjustment and positioning mechanism and tightening it with the tightening knob: The fixing frame is extended to both sides of the adjusting and positioning mechanism so that the pressure applied by the pressing knob to the fixing frame is perpendicular to the surface of the fixing frame.

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