A method for alignment and error compensation of a laser interferometer system

Abstract

The application discloses a kind of laser interferometer system's installation and error compensation method, comprising: workpiece table component, interferometer component and controller, execute the following steps: control workpiece table component and be placed on workpiece table component on range finder adjustment workpiece table chuck's rotation angle and flatness;Calibration plate is placed on workpiece table chuck, and according to grating ruler coordinate and calibration plate coordinate difference compensation workpiece table component's mechanical error;According to grating ruler feedback control workpiece table longitudinal axis and lateral axis's movement, to laser interferometer component light path collimation;According to grating ruler's feedback control workpiece table longitudinal axis and lateral axis movement, through interferometer detection interferometer component's flat mirror in the installation state of workpiece table component, and adjust the pitch and yaw angle of flat mirror;Control workpiece table grating ruler origin and interferometer origin are consistent;Workpiece table position feedback is switched to interferometer by grating ruler feedback, through calibration plate compensation interferometer component's installation residual error.

Description

A method for assembly, adjustment and error compensation of a laser interferometer system Technical Field

[0001] This invention relates to the field of laser interferometer technology, and in particular to a method for assembling, adjusting and compensating for errors in a laser interferometer system. Background Technology

[0002] In existing technologies, laser interferometers are subject to installation and operational errors during use, which reduce their accuracy. While related technologies involve testing and calibration, these methods cannot effectively eliminate installation and operational errors, thus preventing insufficient accuracy and impacting the overall performance of the laser interferometer. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of the present invention is to provide a method for the assembly, adjustment, and error compensation of a laser interferometer system, wherein the laser interferometer can perform multiple error compensations to improve the accuracy and performance of the laser interferometer.

[0004] According to an embodiment of the present invention, a method for assembling, adjusting, and compensating errors in a laser interferometer system includes: a workpiece stage assembly, an interferometer assembly, and a controller. The workpiece stage assembly includes a workpiece stage suction cup, a vertical axis, and two horizontal axes. The vertical axis is connected to the middle of the two horizontal axes. A first grating ruler is correspondingly disposed on each of the two horizontal axes. A second grating ruler is disposed on the vertical axis. The workpiece stage suction cup is movably disposed on the vertical axis. An image sensor, an objective lens, and a rangefinder are spaced apart on the workpiece stage suction cup. A first reflecting mirror is disposed on the outer side of the workpiece stage suction cup in a first direction, and a second reflecting mirror is disposed on the outer side of the workpiece stage suction cup in a second direction. The interferometer assembly includes a first interferometer and a second interferometer. The first interferometer is disposed on one side of the workpiece stage suction cup in the first direction and opposite to the first reflecting mirror. The second interferometer is disposed on one side of the workpiece stage suction cup in the second direction and opposite to the second reflecting mirror. The controller is communicatively connected to the workpiece stage assembly and the interferometer assembly, and the controller is used to perform the following steps:

[0005] Control the workpiece stage assembly and the rangefinder mounted on the workpiece stage assembly to adjust the working state of the workpiece stage suction cup;

[0006] The assembly, adjustment and error compensation method of the laser interferometer system also includes a calibration plate, which is placed on the workpiece stage suction cup, and the working state of the workpiece stage assembly is adjusted according to the correspondence between the first grating ruler and the second grating ruler and the calibration plate.

[0007] The movement of the vertical axis and the horizontal axis is controlled based on the feedback from the first grating ruler and the second grating ruler to collimate the optical path of the interferometer assembly.

[0008] The vertical axis and the horizontal axis are moved according to the feedback from the first grating ruler and the feedback from the second grating ruler. The installation status of the reflector of the interferometer assembly on the workpiece stage assembly is detected and adjusted by the interferometer.

[0009] Control the origins of the first and second grating rulers to be aligned with the origin of the interferometer;

[0010] The workpiece stage position feedback is switched from grating ruler feedback to interferometer feedback, and the residual installation error of the interferometer assembly is compensated by the calibration plate.

[0011] According to the laser interferometer system assembly and error compensation method of the present invention, the controller is connected to the workpiece stage assembly and the interferometer assembly, and the components within the laser interferometer system assembly and error compensation method are calibrated multiple times to reduce or even eliminate the installation error during the assembly process and the measurement error during use of the laser interferometer, and to improve the accuracy of the laser interferometer system assembly and error compensation method, thereby improving the performance of the laser interferometer system assembly and error compensation method.

[0012] In some embodiments, controlling the workpiece stage assembly and the rangefinder disposed on the workpiece stage assembly to adjust the working state of the workpiece stage suction cup includes: moving the longitudinal axis and the transverse axis to adjust the position of the light spot of the interferometer assembly so that the position of the light spot coincides with the edge of the workpiece stage suction cup.

[0013] In some embodiments, controlling the workpiece stage assembly and the rangefinder mounted on the workpiece stage assembly to adjust the working state of the workpiece stage suction cup further includes: moving the vertical axis and the horizontal axis to adjust the position of the light spot of the interferometer assembly so that the position of the light spot coincides with the four corner points of the workpiece stage suction cup, and making the height values ​​of the four detected corner points equal.

[0014] In some embodiments, the assembly, adjustment, and error compensation method of the laser interferometer system further includes a calibration plate, which is placed on the workpiece stage suction cup. Adjusting the working state of the workpiece stage assembly according to the correspondence between the first grating ruler and the second grating ruler and the calibration plate includes: when the calibration plate is placed on the workpiece stage suction cup, moving the longitudinal axis and the transverse axis so that when the objective lens is positioned relative to the calibration plate, the image sensor acquires the target center image of the calibration plate and records the difference between the actual platform coordinates and the theoretical target coordinates of the calibration plate.

[0015] In some embodiments, controlling the movement of the vertical axis and the horizontal axis based on the feedback from the first grating ruler and the second grating ruler to collimate the optical path of the interferometer assembly includes: adjusting the movement of the vertical axis and the horizontal axis so that the beam of the interferometer assembly acts on a designated position of the calibration target until the optical path of the interferometer assembly is collimated.

[0016] In some embodiments, controlling the origins of the first and second grating rulers to be consistent with the origin of the interferometer includes: when the distances measured by the first interferometer at the positive and negative limits of the longitudinal axis are not equal, adjusting the yaw value of the interferometer's plane mirror until the two distances are equal.

[0017] In some embodiments, the switching of workpiece stage position feedback from grating ruler feedback to interferometer, and the compensation of residual installation error of the interferometer assembly through the calibration plate, includes: the laser interferometer is an incremental encoder, the grating ruler has a scribe line in the middle of the coordinate origin, the scribe line in the middle of the coordinate origin of the grating ruler is used as the coordinate origin of the laser interferometer, and at the same time the workpiece stage switches the position feedback from grating ruler to laser interferometer.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 is a schematic diagram of the structure of a laser interferometer according to an embodiment of the present invention;

[0021] Figure 2 is a schematic flowchart of the debugging method of a laser interferometer according to an embodiment of the present invention.

[0022] Figure 3 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0023] Figure 4 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0024] Figure 5 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0025] Figure 6 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0026] Figure 7 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0027] Figure 8 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0028] Figure 9 is a partial structural schematic diagram of a laser interferometer according to an embodiment of the present invention;

[0029] Figure label:

[0030] Laser interferometer system 10,

[0031] Workpiece stage assembly 100, workpiece stage suction cup 110, image sensor 111, objective lens 112, rangefinder 113, vertical axis 120, second grating ruler 121, horizontal axis 130, first grating ruler 131, left edge of workpiece stage suction cup 141, lower edge of workpiece stage suction cup 142, lower left corner of workpiece stage suction cup 143, lower right corner of workpiece stage suction cup 144, upper right corner of workpiece stage suction cup 145, upper left corner of workpiece stage suction cup 146, rangefinder spot 147.

[0032] Interferometer assembly 200, first interferometer 210, first reflecting mirror 211, first theoretical plane 2111, first actual plane 2112, second interferometer 220, second reflecting mirror 221, second theoretical plane 2211, second actual plane 2212, first cornerstone mirror 230, second cornerstone mirror 240, polarizing beam splitter 250, quarter-wave plate 260, incident light 261, reference light 262, measuring light 263, interference light 264.

[0033] Calibration plate 300, first mark 301, second mark 302, third mark 303, theoretical coordinates 304, actual coordinates 305

[0034] Collimation target 400, crosshair target 401. Detailed Implementation

[0035] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention are described in detail below.

[0036] The laser interferometer system 10 according to an embodiment of the present invention is described below with reference to Figures 1-9. The system includes a workpiece stage assembly 100, an interferometer assembly 200, and a controller. The workpiece stage assembly 100 includes a workpiece stage suction cup 110, a vertical axis 120, and two horizontal axes 130. The vertical axis 120 is connected to the middle of the two horizontal axes 130. A first grating ruler 131 is correspondingly disposed on each of the two horizontal axes 130, and a second grating ruler 121 is disposed on the vertical axis 120. The workpiece stage suction cup 110 is movably disposed on the vertical axis 120. An image sensor 111, an objective lens 112, and a rangefinder are spaced apart on the workpiece stage suction cup 110. 113. The workpiece stage suction cup 110 is provided with a first reflector 211 on the outer side in the first direction, and a second reflector 221 on the outer side in the second direction; the interferometer assembly 200 includes a first interferometer 210 and a second interferometer 220. The first interferometer 210 is located on one side of the workpiece stage suction cup 110 in the first direction and is arranged opposite to the first reflector 211. The second interferometer 220 is located on one side of the workpiece stage suction cup 110 in the second direction and is arranged opposite to the second reflector 221; the controller is communicatively connected to the workpiece stage assembly 100 and the interferometer assembly 200.

[0037] Thus, the laser interferometer system 10 includes a workpiece stage assembly 100, an interferometer assembly 200, and a controller. The workpiece stage assembly 100 is adapted to provide a position for the assembly of the interferometer assembly 200, and the interferometer assembly 200 is adapted to be connected to the workpiece stage assembly 100 for use. A controller is also provided, adapted to communicate with the workpiece stage assembly 100 and the interferometer assembly 200 to control the workpiece stage assembly 100 and the interferometer assembly 200 to adjust them according to the design, thereby reducing and eliminating errors in the laser interferometer system 10 and improving the accuracy of its operation.

[0038] Specifically, the controller is used to perform the following steps:

[0039] The workpiece stage assembly 100 and the rangefinder 113 mounted on the workpiece stage assembly 100 are controlled to adjust the working state of the workpiece stage suction cup 110. It is understood that the rangefinder 113 is mounted on the workpiece stage assembly and is suitable for detecting the rotation angle and flatness of the workpiece stage suction cup 110 in the workpiece stage assembly 100, so that the workpiece stage suction cup 110 can adjust the rotation angle and flatness to the required angle as needed, thereby reducing the impact of the installation error of the workpiece stage suction cup 110 in the workpiece stage assembly 100 on the laser interferometer reflector during installation.

[0040] The assembly, adjustment, and error compensation method for the laser interferometer system also includes a calibration plate. The calibration plate is placed on the workpiece stage suction cup, and the working state of the workpiece stage assembly is adjusted according to the correspondence between the first and second grating rulers and the calibration plate. In this way, by setting the calibration plate and corresponding it with the first grating ruler 131 and the second grating ruler 121, the first and second grating rulers can determine the mechanical errors of the longitudinal axis 120 and the transverse axis 130 in the workpiece stage assembly 100 through the calibration of the calibration plate. The mechanical errors of the longitudinal axis 120 and the transverse axis 130 are compensated and adjusted to improve the performance of the longitudinal axis 120 and the transverse axis 130. This allows the workpiece stage assembly 100 to provide a foundation for the subsequent calibration of the laser interferometer optical path and the assembly of the interferometer plane mirror.

[0041] Based on the feedback from the first grating ruler 131 and the second grating ruler 121, the vertical axis 120 and the horizontal axis 130 are moved to collimate the optical path of the interferometer assembly 200. Thus, after detecting the calibration status of the first grating ruler 131 and the second grating ruler 121 relative to the calibration plate 300, the vertical axis 120 and the horizontal axis 130 are adjusted and moved according to the feedback structure to achieve optical path calibration of the interferometer assembly 200.

[0042] The vertical axis 120 and the horizontal axis 130 are controlled to move to detect the installation status of the interferometer assembly 200 on the workpiece stage assembly 100. After the interferometer assembly 200 is calibrated, it is suitable to install the interferometer assembly 200 onto the workpiece stage chuck 110, and control the vertical axis 120 and the horizontal axis 130 to move to detect the installation status of the interferometer assembly 200 on the workpiece stage assembly 100, so as to eliminate the installation error of the interferometer assembly 200 after assembly, thereby reducing the measurement error of the laser interferometer.

[0043] According to an embodiment of the present invention, the laser interferometer system 10 is connected to the workpiece stage assembly 100 and the interferometer assembly 200 via a controller, and performs multiple calibrations on the components within the laser interferometer system 10 to reduce or even eliminate installation errors during the assembly process and measurement errors during use, thereby improving the accuracy of the laser interferometer system 10 and enhancing its performance.

[0044] In some embodiments, after controlling the movement of the vertical axis 120 and the horizontal axis 130 to detect the installation state of the interferometer assembly 200 on the workpiece stage assembly 100, the method further includes controlling the origin of the first grating ruler 131 and the origin of the second grating ruler 121 on the workpiece stage as the origin of the interferometer assembly 200. It is understood that determining the origin during the calibration process is suitable during the detection of the installation state of the workpiece stage assembly 100. For ease of measurement sensing and to simplify the measurement process, the origins of the first grating ruler 131 and the second grating ruler 121 can be used as the origin of the interferometer assembly 200.

[0045] In some embodiments, after controlling the origins of the first grating ruler 131 and the second grating ruler 121 on the workpiece stage as the origins of the interferometer assembly 200, the method further includes: adjusting the feedback of the first grating ruler 131 and the second grating ruler 121 to switch to feedback from the interferometer assembly 200, and compensating for the optical path collimation error, installation angle error, and flatness error of the interferometer assembly 200 through the calibration plate 300. It is understood that after using the origins of the first grating ruler 131 and the second grating ruler 121 as the origins of the interferometer assembly 200, it is suitable to use the interferometer assembly 200 for feedback. During the feedback process, the interferometer assembly 200 is adapted to be calibrated and tested with the calibration plate 300, so that the interferometer assembly 200 adjusts and compensates for the optical path collimation error, installation angle error, and flatness error according to its calibration with the calibration plate 300, thereby improving the accuracy of the interferometer assembly 200 and thus enhancing its performance.

[0046] In some embodiments, controlling the workpiece stage assembly 100 and the rangefinder 113 mounted on the workpiece stage assembly 100 to adjust the working state of the workpiece stage suction cup 110 includes moving the longitudinal axis 120 and the transverse axis 130 to adjust the position of the light spot of the interferometer assembly 200 so that the position of the light spot coincides with the edge of the workpiece stage suction cup 110. It is understood that during the process of controlling the workpiece stage assembly 100 and the rangefinder 113 mounted on the workpiece stage assembly 100 to measure and adjust the working state of the workpiece stage suction cup 110, it is suitable to control the movement of the longitudinal axis 120 and the transverse axis 133 to adjust the position of the light spot of the interferometer assembly 200 so that the position of the light spot is suitable to coincide with the edge of the workpiece stage suction cup 110. After the position of the light spot coincides with the workpiece stage suction cup 110, it is suitable to complete the adjustment of the rotation angle of the workpiece stage suction cup 110.

[0047] In some embodiments, controlling the workpiece stage assembly 100 and the rangefinder mounted on the workpiece stage assembly 100 to adjust the working state of the workpiece stage suction cup 110 further includes: moving the longitudinal axis 120 and the transverse axis 130 to adjust the position of the light spot of the interferometer assembly 200 so that the position of the light spot coincides with the four corner points of the workpiece stage suction cup 110, and making the detected height values ​​of the four corner points equal. In this way, after adjusting the rotation angle of the workpiece stage suction cup 110, adjusting the position of the light plate to coincide with the corner points of the workpiece stage suction cup 110, and detecting the height value of the rangefinder 113 at the corner points, when the detected light intensity values ​​of the four corner points are basically equal, it is suitable to complete the flatness adjustment of the workpiece stage suction cup 110.

[0048] In some embodiments, the assembly, adjustment, and error compensation method of the laser interferometer system further includes a calibration plate, which is placed on the workpiece stage suction cup, and the working state of the workpiece stage assembly is adjusted according to the correspondence between the first grating ruler and the second grating ruler and the calibration plate; including: when the calibration plate 300 is placed on the workpiece stage suction cup 110, moving the longitudinal axis 120 and the transverse axis 130 so that the objective lens 112 is positioned relative to the calibration plate 300 and adjusting the image sensor 111 so that the image sensor 111 acquires the target center image of the calibration plate and records the actual platform coordinates.

[0049] In some embodiments, controlling the movement of the vertical axis 120 and the horizontal axis 130 based on feedback from the first grating ruler 131 and the second grating ruler 121 to collimate the optical path of the interferometer assembly 200 includes: adjusting the movement of the vertical axis 120 and the horizontal axis 130 so that the beam of the interferometer assembly 200 acts on a designated position of the calibration target until the optical path of the interferometer assembly 200 is collimated. Thus, after the initial optical path collimation of the interferometer assembly 200 is completed, it is suitable to perform further optical path calibration of the interferometer assembly 200. Specifically, controlling the movement of the vertical axis 120 and the horizontal axis 130 so that the beam of the interferometer assembly 200 can act on a designated position of the calibration target, thereby achieving optical path collimation of the interferometer assembly 200.

[0050] In some embodiments, controlling the movement of the longitudinal axis 120 and the transverse axis 130 to detect the installation state of the interferometer assembly 200 on the workpiece stage assembly 100 includes adjusting the position of the interferometer assembly 200 until the measurement results of the interferometer assembly 200 on both sides of the longitudinal axis 120 are equal. Thus, after the interferometer assembly 200 undergoes optical path collimation, it is suitable to detect the interferometer assembly 200, allowing it to detect the measurement results on both sides of the longitudinal axis 120. This enables the detection and feedback of the installation state of the interferometer assembly 200 on the workpiece stage assembly 100, and allows for modification and compensation based on the detection results. This eliminates installation errors after assembly, thereby reducing the measurement error of the laser interferometer and improving its accuracy and performance.

[0051] A debugging method for a laser interferometer system 10 according to an embodiment of the present invention includes the following steps:

[0052] The workpiece stage assembly 100 and the rangefinder 113 mounted on the workpiece stage assembly 100 are controlled to adjust the working state of the workpiece stage suction cup 110. It is understood that the rangefinder 113 is mounted on the workpiece stage assembly and is suitable for detecting the rotation angle and flatness of the workpiece stage suction cup 110 in the workpiece stage assembly 100, so that the workpiece stage suction cup 110 can adjust the rotation angle and flatness to the required angle as needed, thereby reducing the impact of the installation error of the workpiece stage suction cup 110 in the workpiece stage assembly 100 on the laser interferometer reflector during installation.

[0053] The assembly, adjustment, and error compensation method for the laser interferometer system also includes a calibration plate. The calibration plate 300 is placed on the workpiece stage suction cup, and the working state of the workpiece stage assembly is adjusted according to the correspondence between the first and second grating rulers and the calibration plate. In this way, by setting the calibration plate 300 relative to the first grating ruler 131 and the second grating ruler 121, the calibration plate can detect the setting of the first grating ruler 131 and the second grating ruler 121, thereby determining the mechanical errors of the longitudinal axis 120 and the transverse axis 130 in the workpiece stage assembly 100. The calibration plate can then compensate for and adjust the mechanical errors of the longitudinal axis 120 and the transverse axis 130 to improve their performance. This allows the workpiece stage assembly 100 to provide a foundation for the subsequent calibration of the laser interferometer optical path and the assembly of the interferometer plane mirror.

[0054] Based on the feedback from the first grating ruler 131 and the second grating ruler 121, the vertical axis 120 and the horizontal axis 130 are moved to collimate the optical path of the interferometer assembly 200. Thus, after detecting the calibration status of the first grating ruler 131 and the second grating ruler 121 relative to the calibration plate 300, the vertical axis 120 and the horizontal axis 130 are adjusted and moved according to the feedback structure to achieve optical path calibration of the interferometer assembly 200.

[0055] The vertical axis 120 and horizontal axis 130 are controlled to move to detect the installation status of the interferometer assembly 200 on the workpiece stage assembly 100. After the interferometer assembly 200 is calibrated, it is suitable to install the interferometer assembly 200 onto the workpiece stage chuck 110, and control the vertical axis 120 and horizontal axis 130 to detect the installation status of the interferometer assembly 200 on the workpiece stage assembly 100, so as to eliminate the installation error of the interferometer assembly 200 after assembly, thereby reducing the measurement error of the laser interferometer.

[0056] According to an embodiment of the present invention, the laser interferometer system 10 is connected to the workpiece stage assembly 100 and the interferometer assembly 200 via a controller, and performs multiple calibrations on the components within the laser interferometer system 10 to reduce or even eliminate installation errors during the assembly process and measurement errors during use, thereby improving the accuracy of the laser interferometer system 10 and enhancing its performance.

[0057] It is understandable that, as shown in Figure 3, the structure of the interferometer assembly, taking the first interferometer 210 as an example, includes a first corner cube mirror 230, a second corner cube mirror 240, a polarizing beam splitter 250, and a quarter-wave plate 260.

[0058] Incident light 261 passes through polarizing beam splitter 250 to generate reference light 262 and measurement light 263. Reference light 262 passes through first corner prism 230 and polarizing beam splitter 250 to enter interference light 264. Measurement light 263 passes through quarter-wave plate 260, first reflecting mirror 211, second corner prism 240 and polarizing beam splitter 250 to enter interference light 264 and interfere with reference light 262.

[0059] The phase of the measuring light 263 can be changed by 90 degrees every two times it passes through the quarter-wave plate, thereby changing its transmission or reflection state as it enters the polarizing beam splitter 250.

[0060] When the position of the first reflecting mirror 211 relative to the first interferometer 210 moves, the interference fringes in the interference light 264 increase or decrease accordingly, and a change in the interference fringe is generated for every quarter of the laser interferometer wavelength moved, so that the displacement can be measured by the change in the interference fringes.

[0061] As shown in Figure 4, taking the first interferometer 210 as an example, when the output beam of the first interferometer 210 has an angle of α with the horizontal axis, the measured distance s and the actual distance d are not the same. The actual distance d is the cosine of the measured distance s multiplied by the angle α. The difference between s and d is called the cosine error. The cosine error is proportional to the measured distance s and the angle α. Therefore, it is necessary to collimate the output beam of the first interferometer 210 so that the output beam of the first interferometer 210 is parallel to the horizontal axis and the angle α is minimized.

[0062] The calibration and compensation process of a laser interferometer includes

[0063] First, by moving the workpiece stage and the rangefinder 113 on the gantry beam above the workpiece stage, the rotation angle and flatness of the workpiece stage suction cup 110 can be adjusted to avoid the installation error of the workpiece stage suction cup 110 affecting the installation of the laser interferometer reflector.

[0064] Specifically, as shown in Figure 5, the left edge 141 and the bottom edge 142 of the suction area of ​​the workpiece stage suction cup 110 are perpendicular to each other, and the suction area has a lower left corner point 143. The longitudinal axis 120 and the transverse axis 130 of the workpiece stage are moved so that the light spot 147 of the rangefinder 113 coincides with the lower left corner point 143 of the suction area of ​​the workpiece stage suction cup 110. Then, the longitudinal and transverse axes of the workpiece stage are moved respectively to determine whether the light spot 147 of the rangefinder 113 coincides with the bottom edge 142 and the left edge 141 of the suction area of ​​the workpiece stage suction cup 110. When the light spot of the rangefinder 113 does not coincide with the bottom edge 142 or the left edge 141 of the suction area of ​​the workpiece stage suction cup 110, the rotation angle of the workpiece stage is adjusted until they coincide, thus completing the adjustment of the rotation angle of the workpiece stage suction cup 110.

[0065] After the rotation angle of the workpiece stage suction cup 110 is adjusted, move the longitudinal axis 120 and the transverse axis 130 of the workpiece stage so that the light spot 147 of the rangefinder 113 reaches the four corner points of the suction area of ​​the workpiece stage suction cup 110: the lower left corner 143, the lower right corner 144, the upper right corner 145, and the upper left corner 146, respectively, and record the height value of the rangefinder 113. When the height values ​​of the rangefinder 113 at the four corner points of the suction area of ​​the workpiece stage suction cup 110 are not equal, adjust the levelness of the workpiece stage until the four height values ​​are basically equal, thereby completing the flatness adjustment of the workpiece stage suction cup 110.

[0066] It is understandable that, as shown in Figure 6, the calibration plate 300 is a equidistant marking mask made of a low-expansion coefficient material, produced by a higher-precision device such as an electron beam lithography machine. Therefore, the spacing of the multiple markings 301, 302, and 303 on the calibration plate 300 can be considered a standard value, which can be used as a standard for calibrating other machine tools. The calibration plate 300 is placed on the upper surface of the workpiece stage suction cup 110 and adsorbed. The longitudinal axis 120 and transverse axis 130 of the workpiece stage are moved so that the objective lens 112 is positioned above the markings on the calibration plate 300, and the image sensor 111 can obtain an image of the markings through the objective lens 112. The image sensor 111 acquires the image of the markings, then calculates the deviation between the center of the markings and the center of the image sensor 111 according to an image processing algorithm. Then, the longitudinal axis 120 and transverse axis 130 of the workpiece stage are moved so that the center of the markings coincides with the center of the image sensor 111. Simultaneously, the transverse axis and y-coordinate values ​​of the workpiece stage are recorded, thereby avoiding the influence of objective lens 112 distortion on the measurement results.

[0067] Furthermore, as shown in Figure 6, by sequentially measuring all the marks on the calibration plate 300, a coordinate diagram can be generated. Taking the mark on the calibration plate 300 as an example, there is a difference between its theoretical coordinate 304 and the actual workpiece stage coordinate 305. This difference may be caused by factors such as the thermal expansion of the first grating ruler 131 and the second grating ruler 121, the non-parallelism of the main axis and the secondary axis of the horizontal axis of the workpiece stage, the non-orthogonality of the two axes with the y-axis of the workpiece stage, and the Abbe error caused by the non-coplanarity of the first grating ruler 131 and the second grating ruler 121 with the horizontal plane of the workpiece stage suction cup 110.

[0068] Calibration using calibration plate 300 can compensate for mechanical errors in the longitudinal axis 120 and transverse axis 130 of the workpiece stage, thereby improving the straightness and orthogonality of the longitudinal axis 120 and transverse axis 130, providing a good foundation for optical path collimation of the laser interferometer and assembly and adjustment of the interferometer plane mirror.

[0069] Meanwhile, as shown in Figure 7, the interferometer optical path collimation target 400 has a crosshair target 401 at its front center and an adhesive material on its back. Taking the collimation of the measurement beam of the first interferometer 210 as an example, the interferometer optical path collimation target 400 can be attached to the left side surface of the workpiece stage suction cup 110. At this time, the first reflecting mirror 211 of the first interferometer 210 is not installed on the lower surface of the left convex surface of the workpiece stage suction cup 110, and can move back and forth along the horizontal axis with the workpiece stage suction cup 110.

[0070] As shown in Figure 7, the point where the interferometer optical path collimating target 400 is closest to the first interferometer 210 is defined as the near end, and the point where the interferometer optical path collimating target 400 is farthest from the first interferometer 210 is defined as the far end. When at the near end, adjust the up, down, left, and right positions of the interferometer optical path collimating target 400 so that the measurement beam of the first interferometer 210 passes through the center of the crosshair on the front of the interferometer optical path collimating target 400. Then, control the horizontal axis of the workpiece stage to move the interferometer target to its farthest point. At this time, adjust the yaw and pitch values ​​of the first interferometer 210 so that the measurement beam of the first interferometer 210 passes through the center of the crosshair on the front of the interferometer optical path collimating target. Then, repeat the adjustment of the near end of the center target (up, down, left, right) and the adjustment of the far end of the first interferometer 210 (yaw and pitch) until the measurement beam of the first interferometer 210 is centered on the front target of the interferometer optical path collimation target at both the near and far ends. This completes the collimation adjustment of the measurement beam of the first interferometer 210 with the horizontal axis of the workpiece stage.

[0071] After the measuring beam of the first interferometer 210 is aligned with the horizontal axis of the workpiece stage, the position of the reference beam in the interference beam is fixed, while the position of the measuring beam in the interferometer beam depends on the yaw and pitch attitude of the first reflecting mirror 211 on the horizontal axis of the interferometer. The intensity of the interferometer signal at the interference beam depends on the degree of coincidence between the measuring beam and the reference beam at the interference beam. By adjusting the yaw and pitch angles of the plane reflecting mirror at a point on the interferometer, the degree of coincidence between the measuring beam and the reference beam can be qualitatively observed by the human eye, or quantitatively observed by a multimeter and oscilloscope to convert the optical interferometer signal into an electrical signal, including the voltage and peak voltage. When the plane reflecting mirror of the interferometer is long, this point-to-surface interferometer mirror attitude adjustment method has a large installation error, resulting in a large measurement error.

[0072] Furthermore, as shown in Figure 8, by adjusting the first reflecting mirror 211 at a single point, the minute yaw angle of the plane reflecting mirror is difficult to detect. When the y-axis is at its positive limit, the first interferometer 210 measures a distance of d1, while when the y-axis is at its negative limit, the first interferometer 210 measures a distance of d2. When d1 and d2 are not equal, the yaw value of the interferometer's plane reflecting mirror is adjusted until d1 and d2 are approximately equal. This patent, through the method of coordinating the interferometer and the workpiece stage, fully utilizes the workpiece stage's motion stroke and the interferometer's own measurement function to detect minute installation errors in the interferometer's plane reflecting mirror, thereby improving measurement accuracy.

[0073] Furthermore, the laser interferometer is an incremental encoder, and its coordinate origin needs to be manually specified, while the grating ruler has a graduation line indicating the coordinate origin. Therefore, the graduation line in the middle of the grating ruler can be used as the coordinate origin of the laser interferometer. Specifically, the grating ruler is used to hom the origin. When the grating ruler finds the origin, a pulse signal is sent to zero the laser interferometer, and simultaneously, the workpiece stage switches its position feedback from the grating ruler to the laser interferometer. This method ensures that the interferometer origin and the workpiece stage origin are consistent, while also guaranteeing the stability of the interferometer origin.

[0074] Moreover, although the above steps basically ensure that the first interferometer 210 and the second interferometer 220 are collimated with the vertical axis 120 and the horizontal axis 130, and that the first reflecting mirror 211 of the interferometer and the reflecting surface of the first reflecting mirror 211 of the interferometer are perpendicular to the vertical axis 120 and the horizontal axis 130, there are still some deviations.

[0075] Furthermore, as shown in Figure 9, there are differences between the first theoretical plane 2111 and the first actual plane 2112 of the first reflecting mirror 211, and between the second theoretical plane 2211 and the second actual plane 2212 of the second reflecting mirror 221. Therefore, compensation is still required. The specific compensation method is the same as the compensation method of the grating ruler calibration plate, but the workpiece stage position feedback is a laser interferometer, and the compensation error is the residual error of the laser interferometer assembly and adjustment.

[0076] In summary, this patent avoids affecting the installation of the interferometer's plane mirror by coarsely adjusting the flatness and rotation angle of the workpiece stage suction cup 110; it avoids affecting the collimation of the interferometer's optical path and the yaw and pitch attitude adjustment of the interferometer's plane mirror by using calibration compensation based on the feedback of the grating ruler; and it further eliminates the interferometer's installation and adjustment residuals by using the interferometer and the grating ruler to share the same coordinate origin and by calibrating and compensating again through the calibration plate 300, thereby improving the positioning accuracy of the workpiece under the feedback of the interferometer.

[0077] Other configurations and operations of the laser interferometer system 10 according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0078] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0079] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for assembling, adjusting, and compensating for errors in a laser interferometer system, characterized in that, include: A workpiece stage assembly includes a workpiece stage suction cup, a longitudinal axis, and two transverse axes. The longitudinal axis is connected to the middle of the two transverse axes. A first grating ruler is correspondingly arranged on each of the two transverse axes, and a second grating ruler is arranged on the longitudinal axis. The workpiece stage suction cup is movably mounted on the longitudinal axis. An image sensor, an objective lens, and a rangefinder are spaced apart on the workpiece stage suction cup. A first reflecting mirror is located on the outer side of the workpiece stage suction cup in a first direction, and a second reflecting mirror is located on the outer side of the workpiece stage suction cup in a second direction. An interferometer assembly includes a first interferometer and a second interferometer. The first interferometer is located on one side of the workpiece stage suction cup in the first direction and is opposite to the first reflecting mirror. The second interferometer is located on one side of the workpiece stage suction cup in the second direction and is opposite to the second reflecting mirror. A controller is connected to the workpiece stage assembly and the... The interferometer assembly is communicatively connected, and the controller is used to perform the following steps: controlling the workpiece stage assembly and the rangefinder mounted on the workpiece stage assembly to adjust the working state of the workpiece stage suction cup; the assembly, adjustment, and error compensation method of the laser interferometer system further includes a calibration plate, which is placed on the workpiece stage suction cup, and the mechanical error of the workpiece stage assembly is compensated according to the correspondence between the first grating ruler and the second grating ruler and the calibration plate; when the calibration plate is mounted on the workpiece stage suction cup, the longitudinal axis and the transverse axis are moved so that when the objective lens is positioned relative to the calibration plate, the image sensor acquires the target center image of the calibration plate and records the difference between the actual platform coordinates and the theoretical target coordinates of the calibration plate; the movement of the longitudinal axis and the transverse axis is controlled according to the feedback of the first grating ruler and the feedback of the second grating ruler to collimate the optical path of the interferometer assembly; The longitudinal and transverse axes are moved according to the feedback from the first and second grating rulers. The installation status of the reflector of the interferometer assembly on the workpiece stage assembly is detected and adjusted by the interferometer. The origins of the first and second grating rulers are aligned with the origin of the interferometer. The workpiece stage position feedback is switched from grating ruler feedback to interferometer feedback, and the residual installation error of the interferometer assembly is compensated by the calibration plate.

2. The assembly, adjustment, and error compensation method for the laser interferometer system according to claim 1, characterized in that, The method of controlling the workpiece stage assembly and the rangefinder mounted on the workpiece stage assembly to adjust the working state of the workpiece stage suction cup includes: moving the vertical axis and the horizontal axis to adjust the position of the light spot of the interferometer assembly so that the position of the light spot coincides with the edge of the workpiece stage suction cup.

3. The assembly, adjustment, and error compensation method for the laser interferometer system according to claim 2, characterized in that, The method of controlling the workpiece stage assembly and the rangefinder mounted on the workpiece stage assembly to adjust the working state of the workpiece stage suction cup further includes: moving the vertical axis and the horizontal axis to adjust the position of the light spot of the interferometer assembly so that the position of the light spot coincides with the four corner points of the workpiece stage suction cup, and making the height values ​​of the four detected corner points equal.

4. The assembly, adjustment, and error compensation method for the laser interferometer system according to claim 1, characterized in that, The method of controlling the movement of the vertical axis and the horizontal axis based on the feedback from the first grating ruler and the second grating ruler to collimate the optical path of the interferometer assembly includes: adjusting the movement of the vertical axis and the horizontal axis so that the beam of the interferometer assembly acts on the designated position of the calibration target until the optical path of the interferometer assembly is collimated.

5. The assembly, adjustment, and error compensation method for the laser interferometer system according to claim 1, characterized in that, The control of the origins of the first and second grating rulers to be consistent with the origin of the interferometer includes: when the distances measured by the first interferometer at the positive and negative limits of the longitudinal axis are not equal, adjusting the yaw value of the interferometer's plane mirror until the two distances are equal.

6. The assembly, adjustment, and error compensation method for the laser interferometer system according to claim 1, characterized in that, The method of switching the workpiece stage position feedback from the grating ruler to the interferometer, and compensating for the residual installation error of the interferometer assembly through the calibration plate, includes: the laser interferometer is an incremental encoder, the grating ruler has a line in the middle of the coordinate origin, the line in the middle of the grating ruler is used as the coordinate origin of the laser interferometer, and at the same time the workpiece stage switches the position feedback from the grating ruler to the laser interferometer.

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