Galvanometer motor linearity and symmetry detection device and detection method

Abstract

The invention discloses a galvanometer motor linearity and symmetry detection device and method, the device comprises an optical platform provided with a detection station, and the detection station comprises a machine base fixed on the optical platform; the fixed seat is arranged on one side of the machine base; the laser is arranged on the fixed seat; the first optical reflecting mirror is positioned in a receivable range of the first laser beam; the second optical reflecting mirror is positioned in a receivable range of the second laser beam reflected by the first optical reflecting mirror; the first diaphragm is embedded in the machine base; the second diaphragm is embedded in the fixed seat, and a third laser beam reflected by the second optical reflector can penetrate through the second diaphragm; a galvanometer piece of the galvanometer motor is located in a receivable range of a fourth laser beam emitted by the second diaphragm; and the light spot acquisition device is positioned in a receivable range of the fifth laser beam reflected by the galvanometer. The device is simple in structure, low in cost and small in occupied space; operation is simple, verification is convenient, and the performance quality of the galvanometer motor can be rapidly detected.

Description

Technical Field

[0001] The invention belongs to the technical field of galvanometer detection, and in particular relates to a galvanometer motor linearity and symmetry detection device and detection method. Background Art

[0002] At present, in the application fields of laser processing and optical communication, the high-precision control and consistency of the galvanometer determine the market positioning value of the galvanometer products. At the same time, galvanometer products with good consistency are more convenient to disassemble and replace, which reduces the maintenance and calibration costs and can better gain the favor of customers. One of the core components of galvanometer products is the galvanometer motor, and the linearity and symmetry of the galvanometer motor are one of the key factors affecting the high precision and consistency of galvanometer products.

[0003] However, the existing testing instruments are expensive, bulky, and occupy a large space. In addition, the operation is cumbersome, the calibration process is complicated, and the performance quality of the galvanometer motor cannot be quickly tested. Therefore, a galvanometer motor linearity and symmetry testing device and method are designed to solve the above problems.

[0004] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology section of the present invention. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a device and method for detecting the linearity and symmetry of a galvanometer motor.

[0006] In order to achieve the above objectives and other related objectives, the present invention provides a galvanometer motor linearity and symmetry detection device, including an optical platform, on which a detection station is arranged, and the detection station includes: A machine base, the machine base is fixed on the optical platform and is used for mounting a galvanometer motor to be tested; A fixing seat, the fixing seat being arranged on one side of the machine base; A laser, the laser being arranged on the fixing seat and used for emitting an initial first laser beam; the laser and the galvanometer motor being located on different sides of the seat; a first optical reflector, wherein the first optical reflector is located within a receivable range of the first laser beam; a second optical reflector, wherein the second optical reflector is located within a receivable range of the second laser beam reflected by the first optical reflector; A first aperture, wherein the first aperture is embedded in the base; a second aperture, wherein the second aperture is embedded in the fixing seat, and the third laser beam reflected by the second optical reflector can pass through the second aperture; and the galvanometer lens of the galvanometer motor is located within the receivable range of the fourth laser beam emitted by the second aperture; A light spot collection device is located within the receivable range of the fifth laser beam reflected by the galvanometer lens.

[0007] Furthermore, the first optical reflector is arranged on two-dimensional adjustment frame 1, and the second optical reflector is arranged on two-dimensional adjustment frame 2. In this solution, the two-dimensional adjustment frame is arranged to fine-tune the coaxiality and incident angle of the laser beam, which improves the accuracy compared with manual adjustment, thereby ensuring the accuracy of the linearity and symmetry detection of the galvanometer motor.

[0008] Furthermore, the first aperture and the second aperture are both precision micro-aperture apertures, and the fourth laser beam and the fifth laser beam are both shaped small-spot laser beams. In this solution, after the third laser beam passes through the aperture, a shaped small-spot laser beam can be obtained, which facilitates the collection of the light spot and improves the accuracy of the light spot collection.

[0009] Furthermore, the center line of the first aperture is arranged to coincide with the center line of the second aperture, and the propagation paths of the third laser beam and the fourth laser beam are arranged to coincide with the center line of the second aperture. In this solution, the third laser beam and the fourth laser beam are both propagated along the center line of the aperture, so that the small spot laser beam obtained after the laser beam passes through the aperture is more uniform.

[0010] Furthermore, the first laser beam is arranged at an angle of 45° to the first optical reflector, the second laser beam is arranged at an angle of 45° to the second optical reflector, the first optical reflector and the second optical reflector are arranged symmetrically, and the third laser beam is arranged parallel to the first laser beam. In this solution, the arrangement of the optical reflectors is convenient, and the accurate propagation of the laser beam is guaranteed, which ensures the accuracy of the linearity and symmetry detection of the galvanometer motor.

[0011] Furthermore, the light spot acquisition device includes a center-divided scale. In this solution, the center-divided scale is extremely symmetrical and has accurate markings. The scale lines on the center-divided scale are usually evenly distributed to ensure the accuracy of the measurement; the scale lines of the center-divided scale are thinner, which helps to improve the accuracy of the reading. The thin scale lines can reduce visual errors and make the reading more accurate.

[0012] Furthermore, the scale surface of the center-divided scale ruler is arranged toward the reflection direction of the galvanometer lens. In this solution, it is ensured that the fifth laser beam can be arranged perpendicular to the scale surface of the center-divided scale ruler.

[0013] Furthermore, the laser is a single-mode fiber collimated laser. In this solution, the laser can be used to obtain a high-power, high-efficiency, high-quality beam with high precision and high sensitivity, ensuring the accuracy of the linearity and symmetry detection of the galvanometer motor.

[0014] Furthermore, two detection stations are provided. In this solution, the two detection stations can be used to detect the X-mirror motor and the Y-mirror motor respectively, and the two detection stations can share a machine base and be symmetrically arranged relative to the machine base to improve detection efficiency.

[0015] Furthermore, the shape of the base is T-shaped. In this solution, the T-shaped base is convenient for installing two galvanometer motors.

[0016] The present invention also discloses a method for detecting the linearity and symmetry of a galvanometer motor. The method is applicable to the detection device described in the above technical solution. The method comprises the following steps: Step 1: The laser emits a first laser beam, the first laser beam passes through a first optical reflector to form a second laser beam, the second laser beam passes through the second optical reflector to form a third laser beam, the third laser beam passes through a first aperture and a second aperture to form a fourth laser beam with high quality and a small spot diameter, the fourth laser beam passes through a galvanometer lens of a galvanometer motor and is reflected to form a fifth laser beam, which is irradiated onto a middle scale of a spot collection device; Step 2: Through mutual micro-adjustment of the two-dimensional adjustment frame 1 and the two-dimensional adjustment frame 2, the laser beam is finally irradiated at the center of the galvanometer lens of the galvanometer motor at a fixed angle; Step 3: Set the galvanometer motor in the powered state to be at the origin of the control system, adjust the angle of the galvanometer motor on the base, so that the galvanometer lens of the galvanometer motor in this state forms an angle of 45° with the incident laser beam, and the laser beam is vertically irradiated at the position with coordinate 0 on the center scale after propagation, and set the distance between the center of the galvanometer lens and the center scale to L; Step 4: Send a command to the galvanometer motor through the control system to make the galvanometer motor deflect a certain angle, set the corresponding position of the laser beam spot on the middle scale to S, and calculate the actual rotation angle θ of the galvanometer motor each time through the trigonometric function formula θ=arctan(S / L); Step 5: Continuously send instructions to the galvanometer motor, and obtain the linearity curve of the galvanometer motor according to the calculated error of the actual rotation angle θ; Step 6: Send positive and negative deflection commands of the same change amount to the galvanometer motor, set the two positions corresponding to the laser spot on the middle scale to S1 and S2 respectively, calculate the absolute value errors of S1 and S2, and obtain the symmetry error S′ of the galvanometer motor.

[0017] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art: The device and method for detecting linearity and symmetry of a galvanometer motor designed in the present invention have a simple structure, low manufacturing cost, and wide applicability; the device is exquisite and does not take up space; the operation is simple and intuitive; the tool calibration is convenient and quick, and the performance quality of the galvanometer motor can be quickly detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the detection device of the present invention; Figure 2 It is a schematic diagram of the fixing seat and related structures of the present invention; Figure 3 The detection state of the present invention is shown in FIG. Figure 1 ; Figure 4 The detection state of the present invention is shown in FIG. Figure 2 ; Figure 5 The detection state of the present invention is shown in FIG. Figure 3 ; Figure 6 The detection state of the present invention is shown in FIG. Figure 4 ; In the above drawings, 1. optical platform; 2. machine base; 3. galvanometer motor; 301. galvanometer lens; 4. fixing base; 5. laser; 6. first optical reflector; 7. second optical reflector; 8. first aperture; 9. second aperture; 10. light spot collection device; 11. first laser beam; 12. second laser beam; 13. third laser beam; 14. fourth laser beam; 15. fifth laser beam; 16. two-dimensional adjustment frame 1; 17. two-dimensional adjustment frame 2; 18. driver. DETAILED DESCRIPTION

[0019] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0020] It should be noted that in the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. Terms such as "horizontal", "vertical", and "overhanging" do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0021] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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, it can be an electrical connection, it can be a direct connection, it can be indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0023] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0024] Embodiment 1: See attached Figure 1 and attached Figure 2 As shown, this embodiment provides a galvanometer motor linearity and symmetry detection device, including an optical platform 1. The setting of the optical platform 1 can ensure the consistency of detection. The optical platform 1 is provided with a detection station, and the detection station includes: A machine base 2, which is fixed on the optical platform 1 and is used to install a galvanometer motor 3 to be tested; A fixing seat 4, which is arranged on one side of the base 2; See attached Figure 1 and attached Figure 2 As shown, it also includes a laser 5, which is arranged on the fixing base 4 and is used to emit an initial first laser beam 11; the laser 5 and the galvanometer motor 3 are located on different sides of the base 2; the laser 5 is a single-mode fiber collimation laser 5. The laser 5 can obtain a high-power, high-efficiency, high-quality beam with high precision and high sensitivity, thereby ensuring the accuracy of the linearity and symmetry detection of the galvanometer motor 3.

[0025] A first optical reflector 6, wherein the first optical reflector 6 is located within a receivable range of the first laser beam 11; A second optical reflector 7, the second optical reflector 7 is located within a receivable range of the second laser beam 12 reflected by the first optical reflector 6; See attached Figure 1 As shown, it also includes a first aperture 8, which is embedded in the machine base 2; it also includes a second aperture 9, which is embedded in the fixing seat 4, and the third laser beam 13 reflected by the second optical reflector 7 can pass through the second aperture 9; the vibrating lens 301 of the vibrating mirror motor 3 is located within the receivable range of the fourth laser beam 14 emitted by the second aperture 9; the first aperture 8 and the second aperture 9 are both precision micro-aperture apertures, and the fourth laser beam 14 and the fifth laser beam 15 are both shaped small-spot laser beams. After the third laser beam 13 passes through the aperture, a shaped small-spot laser beam can be obtained, which is convenient for the collection of the spot and improves the accuracy of the spot collection. The center line of the first aperture 8 is arranged to coincide with the center line of the second aperture 9, and the propagation routes of the third laser beam 13 and the fourth laser beam 14 are arranged to coincide with the center line of the second aperture 9. The third laser beam 13 and the fourth laser beam 14 are both propagated along the center line of the aperture, so that the small-spot laser beam obtained after the laser beam passes through the aperture is more uniform.

[0026] See attached Figure 1 As shown, it also includes a spot collection device 10, which is located within the receivable range of the fifth laser beam 15 reflected by the vibrating lens 301. The spot collection device 10 includes a center-divided scale. The center-divided scale has excellent symmetry and is accurately marked. The scale lines on the center-divided scale are usually evenly distributed to ensure the accuracy of the measurement; the scale lines of the center-divided scale are thinner, which helps to improve the accuracy of the reading. The thin scale lines can reduce visual errors and make the reading more accurate. The scale surface of the center-divided scale is set toward the reflection direction of the vibrating lens 301. It is ensured that the fifth laser beam 15 can be set perpendicular to the scale surface of the center-divided scale.

[0027] See attached Figure 2 As shown, the first optical reflector 6 is arranged on a two-dimensional adjustment frame 16, and the second optical reflector 7 is arranged on a two-dimensional adjustment frame 17. The two-dimensional adjustment frame is arranged to fine-tune the coaxiality and incident angle of the laser beam, which improves the accuracy compared with manual adjustment, thereby ensuring the accuracy of the linearity and symmetry detection of the galvanometer motor 3.

[0028] See attached Figure 2 As shown, the first laser beam 11 is arranged at a 45° angle with the first optical reflector 6, the second laser beam 12 is arranged at a 45° angle with the second optical reflector 7, the first optical reflector 6 and the second optical reflector 7 are arranged symmetrically, and the third laser beam 13 is arranged parallel to the first laser beam 11. It is convenient to arrange the optical reflectors, and also ensures the accurate propagation of the laser beam, and ensures the accuracy of the linearity and symmetry detection of the galvanometer motor 3.

[0029] See attached Figure 1 As shown, there are two detection stations. The two detection stations can be used to detect the X-galvanometer motor 3 and the Y-galvanometer motor 3 respectively. The X-galvanometer motor 3 is mainly used to control the deflection of the laser beam in the horizontal direction (X-axis). It rotates at high speed to enable the laser beam to move precisely in the X-axis direction, thereby achieving fine control during laser welding or cutting. The Y-galvanometer motor 3 controls the deflection of the laser beam in the vertical direction (Y-axis). Similarly, it rotates at high speed to enable the laser beam to move precisely in the Y-axis direction, and works in conjunction with the X-galvanometer motor 3 to complete complex laser processing tasks. The two detection stations can share a machine base 2 and be arranged symmetrically relative to the machine base 2 to improve the detection efficiency. The shape of the machine base 2 is T-shaped. It is convenient for the installation of two galvanometer motors 3.

[0030] Embodiment 2: The present invention also discloses a method for detecting the linearity and symmetry of a galvanometer motor 3. The detection method is applicable to the detection device in the first embodiment. The detection method comprises the following steps: Step 1: a first laser beam 11 is emitted by a laser 5, the first laser beam 11 passes through a first optical reflector 6 to form a second laser beam 12, the second laser beam 12 passes through a second optical reflector 7 to form a third laser beam 13, the third laser beam 13 passes through a first aperture 8 and a second aperture 9 to form a fourth laser beam 14 with high quality and a small spot diameter, the fourth laser beam 14 passes through a galvanometer lens 301 of a galvanometer motor 3 and is reflected to form a fifth laser beam 15, which is irradiated onto a center scale of the spot collection device 10; Step 2: Through the mutual micro-adjustment of the two-dimensional adjustment frame 16 and the two-dimensional adjustment frame 2 17, the laser beam is finally irradiated at the center of the galvanometer lens 301 of the galvanometer motor 3 at a fixed angle, see the attached Figure 3 As shown; Step 3: Set the galvanometer motor 3 in the powered state to be at the origin of the control system, adjust the angle of the galvanometer motor 3 on the base 2, so that the galvanometer lens 301 of the galvanometer motor 3 in this state forms an angle of 45° with the incident laser beam, and the laser beam is vertically irradiated at the position with coordinate 0 on the middle scale after propagation. Set the distance between the center of the galvanometer lens 301 and the middle scale to L, see the attached figure. Figure 3 As shown; Step 4: Send a command to the galvanometer motor 3 through the control system, and control the driver 18 to make the galvanometer motor 3 deflect a certain angle, and set the corresponding position of the laser beam spot on the middle scale to S, see the attached Figure 4 As shown in the figure, the actual rotation angle θ of the galvanometer motor 3 is calculated by the trigonometric formula: θ=arctan(S / L), see the attached Figure 4 As shown; Step 5: continuously send instructions to the galvanometer motor 3, and obtain the linearity curve of the galvanometer motor 3 according to the calculated error of the actual rotation angle θ; Step 6: Send the same amount of positive and negative deflection instructions to the galvanometer motor 3, and set the two positions corresponding to the laser spot on the middle scale to S1 and S2 respectively, see the attached Figure 5 and attached Figure 6 As shown, the absolute value errors of S1 and S2 are calculated, and the symmetry error S′ of the galvanometer motor 3 is obtained.

[0031] Calibration of galvanometer motor 3: Through the detection device, the same instruction array is given to different galvanometer motors 3, and the actual deflection angle of the galvanometer motor 3 is corrected so that it obtains the same actual rotation angle θ of the galvanometer motor 3 corresponding to each set of instructions, thereby ensuring the consistency of the galvanometer motor 3.

[0032] The detection method of the X galvanometer motor and the Y galvanometer motor is the same.

[0033] The device and method for detecting linearity and symmetry of a galvanometer motor designed in the present invention have a simple structure, low manufacturing cost, and wide applicability; the device is exquisite and does not take up space; the operation is simple and intuitive; the tool calibration is convenient and quick, and the performance quality of the galvanometer motor can be quickly detected.

[0034] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for detecting linearity and symmetry of a galvanometer motor, characterized in that: It comprises an optical platform (1), on which a detection station is arranged, and the detection station comprises: A machine base (2), the machine base (2) being fixed on the optical platform (1) and used for mounting a galvanometer motor (3) to be tested; A fixing seat (4), the fixing seat (4) being arranged on one side of the machine base (2); a laser (5), the laser (5) being arranged on the fixing seat (4) and used for emitting an initial first laser beam (11); the laser (5) and the galvanometer motor (3) being located on different sides of the machine seat (2); A first optical reflector (6), the first optical reflector (6) being located within a receivable range of the first laser beam (11); a second optical reflector (7), the second optical reflector (7) being located within a receivable range of a second laser beam (12) reflected by the first optical reflector (6); A first aperture (8), wherein the first aperture (8) is embedded in the machine base (2); a second aperture (9), the second aperture (9) being embedded in the fixing seat (4), the third laser beam (13) reflected by the second optical reflector (7) being able to pass through the second aperture (9); the galvanometer lens (301) of the galvanometer motor (3) being located within a receivable range of the fourth laser beam (14) emitted by the second aperture (9); A light spot collection device (10), wherein the light spot collection device (10) is located within a receivable range of the fifth laser beam (15) reflected by the galvanometer lens (301).

2. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: The first optical reflector (6) is arranged on a two-dimensional adjustment frame 1 (16), and the second optical reflector (7) is arranged on a two-dimensional adjustment frame 2 (17).

3. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: The first diaphragm (8) and the second diaphragm (9) are both precision micro-aperture diaphragms, and the fourth laser beam (14) and the fifth laser beam (15) are both shaped small-spot laser beams.

4. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: The center line of the first aperture (8) is arranged to coincide with the center line of the second aperture (9), and the propagation paths of the third laser beam (13) and the fourth laser beam (14) are arranged to coincide with the center line of the second aperture (9).

5. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: The first laser beam (11) is arranged at an angle of 45° to the first optical reflector (6), the second laser beam (12) is arranged at an angle of 45° to the second optical reflector (7), the first optical reflector (6) and the second optical reflector (7) are arranged symmetrically, and the third laser beam (13) is arranged parallel to the first laser beam (11).

6. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: The light spot collection device (10) comprises a center-divided scale.

7. The device for detecting linearity and symmetry of a galvanometer motor according to claim 6, characterized in that: The scale surface of the center-divided scale ruler is arranged toward the reflection direction of the vibrating lens (301).

8. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: The laser (5) is a single-mode optical fiber collimation laser (5).

9. The device for detecting linearity and symmetry of a galvanometer motor according to claim 1, characterized in that: Two detection stations are provided, and the machine base (2) is in a T-shape.

10. A method for detecting linearity and symmetry of a galvanometer motor (3), characterized in that: The detection method is applicable to the detection device according to any one of claims 1 to 9, and the detection method comprises the following steps: Step 1: The laser (5) emits a first laser beam (11), the first laser beam (11) passes through a first optical reflector (6) to form a second laser beam (12), the second laser beam (12) passes through the second optical reflector (7) to form a third laser beam (13), the third laser beam (13) passes through a first aperture (8) and a second aperture (9) to form a fourth laser beam (14) of high quality and a small spot diameter, the fourth laser beam (14) passes through a galvanometer lens (301) of a galvanometer motor (3) and is reflected to form a fifth laser beam (15), which is irradiated onto a center scale of a spot collection device (10); Step 2: by mutual micro-adjustment of the two-dimensional adjustment frame 1 (16) and the two-dimensional adjustment frame 2 (17), the laser beam is finally irradiated at a fixed angle to the center of the galvanometer lens (301) of the galvanometer motor (3); Step 3: Set the galvanometer motor (3) in the powered state to be at the origin of the control system, adjust the angle of the galvanometer motor (3) on the base (2), so that the galvanometer piece (301) of the galvanometer motor (3) in this state forms an angle of 45° with the incident laser beam, and the laser beam is vertically irradiated at the position with coordinate 0 on the center scale ruler after propagation, and set the distance between the center of the galvanometer piece (301) and the center scale ruler at this time to be L; Step 4: Sending a command to the galvanometer motor (3) through the control system so that the galvanometer motor (3) deflects a certain angle, setting the position of the laser beam spot on the middle scale to S, and calculating the actual rotation angle θ of the galvanometer motor (3) each time through the trigonometric function formula θ=arctan(S / L); Step 5: continuously sending instructions to the galvanometer motor (3), and obtaining a linearity curve of the galvanometer motor (3) according to the calculated error of the actual rotation angle θ; Step 6: Send positive and negative deflection instructions of the same change amount to the galvanometer motor (3), set the two positions corresponding to the laser spot on the middle scale to S1 and S2 respectively, calculate the absolute value errors of S1 and S2, and obtain the symmetry error S′ of the galvanometer motor (3).

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