Deviation measuring device

Abstract

A deviation measuring device for measuring the deviation between the center (O) and standard center (O') of a substrate (W), comprising a reference arm (101), a movable arm (103), and a first linear module (102), the movable arm (103) is provided with a first positioning claw (104) that abuts against two points on the end of the substrate (W), the reference arm (101) is provided with a second positioning claw (105) that abuts against two points on the end of the substrate (W), and the movable arm (103) is arranged to face the reference arm (101). The line connecting the center (x1) of the first positioning claw (104) and the center (x2) of the second positioning claw (105) is a straight line L, which passes through the standard center (O'), and the moving arm (103) is driven by the first linear module (102) to move along the straight line L, and the first positioning claw (104) pushes the substrate (W) until the first positioning claw (104) and the second positioning claw (105) simultaneously contact the edge of the substrate, at which time the substrate center (O) is located on the straight line L. The deviation between the substrate center (O) and the standard center (O') can be calculated based on the coordinates of the reference arm (101) and the moving arm (103). The substrate (W) may be an elliptical or circular substrate with a notch or flat edge.

Description

Technical Field

[0001] The present invention generally relates to the field of semiconductor manufacturing, and more particularly to an apparatus for measuring the deviation between the center of a substrate and a standard center.

Background Art

[0002] In most processes of a substrate processing step, the substrate is rotated with an axis passing through the center of the substrate as the rotation axis, but it is necessary to align the center of the substrate and the center of the substrate chuck, that is, the standard center. In the substrate manufacturing process, due to process-level limitations, there may be a deviation between the shape and size of the substrate and the shape and size of the standard substrate. Therefore, when the substrate is installed, the center of the substrate may deviate from the standard center and cause problems. For example, in a substrate edge cleaning device, the substrate is clamped by a substrate chuck, the substrate is rotated about the rotation axis by the drive of a rotation drive mechanism, and a cleaning nozzle is arranged near the edge of the substrate to clean the edge of the substrate. If there is a deviation between the center of the substrate and the standard center, the distance between the cleaning nozzle and the outer periphery of the substrate will not be a preset value, and a good cleaning result cannot be obtained.

Summary of the Invention

[0003] An object of the present invention is to propose an apparatus for measuring the deviation between the center of a substrate and a standard center.

[0004] To achieve the above objective, embodiments of the present invention provide a deviation measuring device for measuring the deviation between the center of a substrate and a standard center, the device comprising a reference arm, a movable arm, and a first linear module. A positioning claw is provided on the reference arm, configured to contact two points on the edge of the substrate. A second positioning claw is provided on the reference arm, configured to contact two points on the edge of the substrate. The movable arm is positioned on the opposite side of the reference arm. A straight line L is formed by connecting the centers of the first positioning claw and the second positioning claw, and this straight line L passes through the standard center. The first linear module is connected to the movable arm, which is driven by the first linear module to move along the straight line L, and the first positioning claw pushes the substrate until the first positioning claw and the second positioning claw simultaneously contact the edge of the substrate. The deviation between the center of the substrate and the standard center is calculated based on the coordinates of the reference arm and the movable arm, and the substrate may be a circular or elliptical substrate.

[0005] Another embodiment of the present invention provides a deviation measuring device for measuring the deviation between the center of a substrate and a standard center, comprising a reference arm, a movable arm, and a first linear module. The reference arm is provided with positioning claws that contact two points on the edge of the substrate. A contact head and a pressure sensor are arranged on the movable arm. The contact head is configured to contact one point on the edge of the substrate. The pressure sensor is connected to the contact head and measures the pressure between the edge of the substrate and the contact head. The movable arm is positioned on the opposite side from the reference arm. The line connecting the center of the positioning claw and the center of the contact head is a straight line L, and the straight line L passes through the standard center. The first linear module is connected to the movable arm, and the movable arm is driven by the first linear module to move along the straight line L. During measurement, the movable arm starts moving from an initial coordinate and pushes the substrate until the positioning claw and the contact head simultaneously contact the edge of the substrate. At this time, the center of the substrate is located on the straight line L, the movable arm is located at the end coordinate, and the diameter d1 of the substrate is then calculated to obtain the deviation n between the center of the substrate and the standard center. The calculation formula is as follows: JPEG0007869250000001.jpg4682

[0006] Here, d0 is the standard diameter, the positioning claw shape is V-shaped, θ is half the opening angle of the positioning claw, m = Δ1 - Δ0, Δ1 is the distance traveled between the initial and final coordinates of the moving arm, and Δ0 is the standard travel distance of the moving arm. The standard travel distance is determined in advance and is determined as follows: A substrate with a standard diameter d0 is used as the substrate in the measurement, and the distance traveled between the initial and final coordinates of the moving arm is taken as the standard travel distance. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows a perspective view of a deviation measuring device according to the first embodiment of the present invention. [Figure 2] Figure 2 is a comparison diagram showing measurements of a standard-sized substrate W' and a non-standard-sized substrate W, respectively, using the deviation measuring device of the first embodiment. [Figure 3] Figure 3 shows a diagram of the state when a notched substrate is measured using the deviation measuring device of the first embodiment. [Figure 4] Figure 4 shows a diagram of the state when a substrate with a flat edge is measured using the deviation measuring device of the first embodiment. [Figures 5a-5c] Figures 5a to 5c show the first state change diagrams when an elliptical substrate is measured using the deviation measuring device of the first embodiment. [Figures 6a-6b] Figures 6a and 6b show the second state change diagram when an elliptical substrate is measured using the deviation measuring device of the first embodiment. [Figure 7] Figure 7 is a magnified view of a part of the structure shown in Figure 1. [Figure 8] Figure 8 is a magnified view of a part of the structure shown in Figure 3. [Figure 9] Figure 9 shows a perspective view of a deviation measuring device incorporating the displacement sensor of the first embodiment. [Figure 10] Figure 10 shows a perspective view of a deviation measuring device according to a second embodiment of the present invention. [Figure 11] Figure 11 is a magnified view of a part of the structure shown in Figure 10. [Figure 12] Figure 12 shows a top view of the deviation measuring device according to the second embodiment. [Figure 13] Figure 13 shows a schematic diagram illustrating the measurement of the substrate diameter d1 and the deviation n between the substrate center and the standard center in the second embodiment. [Modes for carrying out the invention]

[0008] The principles, technical features, technical effects, and technical solutions in embodiments of the present invention are described below clearly and completely in conjunction with the accompanying drawings.

[0009] <First Embodiment> As shown in Figure 1, an embodiment of the present invention discloses a deviation measuring device for measuring the deviation between the center of a substrate and a standard center. The deviation measuring device includes a reference arm 101, a first linear module 102, and a movable arm 103. The movable arm 103 is provided with a first positioning claw 104 that contacts two points on the edge of the substrate W. The reference arm 101 is provided with a second positioning claw 105 that contacts two points on the edge of the substrate W. The reference arm 101 is positioned opposite the movable arm 103, and the line connecting the center of the first positioning claw 104 and the center of the second positioning claw 105 is a straight line L, which passes through the standard center, and the first linear module 102 is connected to the movable arm 103, and the movable arm 103 can be driven by the first linear module 102 to move along the straight line L. The first positioning claw 104 pushes the substrate W until the first positioning claw 104 and the second positioning claw 105 simultaneously contact the edge of the substrate W. At this time, the center of the substrate W is located on the straight line L. The deviation between the center point of the substrate W and the standard center point can be calculated based on the coordinates of the reference arm 101 and the moving arm 103.

[0010] As shown in Figure 2, x1 is the center point of the first positioning claw 104, and x2 is the center point of the second positioning claw 105. When the substrate W' is a standard-sized substrate, and the first positioning claw 104 and the second positioning claw 105 simultaneously contact the edge of the substrate W', the center point O of the substrate W' is x1 and x 2と The center point O of the substrate W' is the midpoint of x1 and x2, and the center point O of the substrate W' is also the standard center point O'. Furthermore, if the substrate W is a non-standard sized circular substrate, when the first positioning claw 104 and the second positioning claw 105 contact the edge of the substrate W simultaneously, the center point O of the substrate W becomes the midpoint of x1 and x2. The center point O of the substrate W is offset from the standard center point O'. Since the first positioning claw 104 is stationary relative to the moving arm 103 and the second positioning claw 105 is stationary relative to the reference arm 101, the coordinates of the moving arm 103 can be considered as the coordinates of the center point x1 of the first positioning claw 104, and the coordinates of the reference arm 101 can be considered as the coordinates of the center point x2 of the second positioning claw 105. The deviation between the center point O of the substrate W and the standard center point O' can be calculated based on the coordinates of the moving arm 103 and the coordinates of the reference arm 101.

[0011] For example, when measuring a standard-sized circuit board, if the x2 coordinate is 0 and the x1 coordinate is 310, the coordinate of the standard center point O' will be 155. When measuring a non-standard-sized circular circuit board, if the x2 coordinate is 0 and the x1 coordinate is 309.8, the coordinate of the center point O of the board will be 154.9, and the deviation between the center point O of the board and the standard center point O' will be 0.1.

[0012] The substrate W may be a circular substrate with a notch. As shown in Figure 3, when the first positioning claw 104 and the second positioning claw 105 simultaneously contact the edge of the substrate W, if the notch is very close to the second positioning claw 105, there are two points I and J on the edge of the substrate W that contacts the first positioning claw 104, so only point H of the second positioning claw 105 contacts the edge of the substrate W. As a result, the presence of the notch does not affect the calculation of the position of the center point of the substrate W. The substrate W may also be a circular substrate with a flat edge, as shown in Figure 4, and the presence of a flat edge does not affect the calculation of the position of the center point of the substrate W.

[0013] The substrate W may be an elliptical substrate. As shown in Figure 5a, two points on the edge of the substrate W are in contact with the second positioning claw 105. However, if the center point O of the substrate W is not on the straight line L, the thrust F of the first positioning claw 104 on the substrate W rotates the substrate W counterclockwise, and the substrate W passes through the position shown in Figure 5b and finally reaches the position shown in Figure 5c. At this time, the two points on the edge of the substrate W are in contact with the first positioning claw 104, the center point O of the substrate W and its minor axis are on the straight line L, and the center point O of the substrate W is the midpoint of x1 and x2. x1 is the center point of the first positioning claw 104, and x2 is the center point of the second positioning claw 105. The arc arrows in Figures 5a and 5b indicate the direction of rotation of the substrate W when the first positioning claw 104 pushes the substrate W.

[0014] When the substrate W is in the position shown in Figure 6a, the thrust F of the first positioning claw 104 of the substrate W causes the substrate W to rotate clockwise, and the substrate W eventually takes the position shown in Figure 6a. The center point O and the major axis of the substrate are located on a straight line L, and the center point O of the substrate W is the midpoint of x1 and x2, where x1 is the center point of the first positioning claw 104 and x2 is the center point of the second positioning claw 105. The arc-shaped arrow in Figure 6a indicates the direction of rotation of the substrate W when the first positioning claw 104 pushes the substrate W.

[0015] As shown in FIG. 7, a pressure sensor 106 is provided on the moving arm 103. The pressure sensor 106 is connected to the first positioning claw 104 and measures the pressure between the end of the substrate W and the first positioning claw 104. During each measurement, after the first positioning claw 104 and the second positioning claw 105 simultaneously contact the end of the substrate W, the pressure between the first positioning claw 104 and the substrate W is maintained at a fixed value (e.g., 5 N) or within a set range (e.g., 4.8 N to 5.2 N). Thereby, the error due to poor contact between the first positioning claw 104 and the substrate W is reduced, and the calculation accuracy of the center position of the substrate W is improved.

[0016] The measurement of the deviation between the center of the substrate and the standard center using the apparatus of this embodiment includes the following steps. In step S1, the substrate W is horizontally lifted by a support mechanism (not shown) and abutted against the second positioning claw 105. The above-mentioned support mechanism may be a smooth and horizontal platform or an air suspension platform. In step S2, the position of the reference arm 101 is fixed, and the moving arm 103 starts to move from the initial coordinates, is driven by the first linear module 102, and moves along the straight line L. The first positioning claw 104 pushes the substrate W until the first positioning claw 104 and the second positioning claw 105 simultaneously contact the edge of the substrate W. In step S3, the moving arm 103 slowly moves along the straight line L, and during this time, the pressure sensor 106 measures the pressure in real time. In step S4, when the pressure reaches the set value or the set range, the moving arm 103 stops moving and maintains the pressure within the set value or the set range. In step S5, based on the coordinates of the reference arm 101 and the moving arm 103, the center point position of the substrate W is calculated to obtain the deviation between the center of the substrate W and the standard center.

[0017] In step S2, the initial coordinates of the reference arm 101 and the initial coordinates of the moving arm 103 can be obtained in advance. In step S5, the coordinates of the reference arm 101 are the initial coordinates of the reference arm 101. Since the displacement amount of the moving arm 103 on the first linear module 102 can be read, the coordinates of the moving arm 103 can be calculated based on the initial coordinates of the moving arm 103 and the displacement amount of the moving arm 103 on the first linear module 102.

[0018] The displacement sensor 1012 can also be used to obtain the movement amount of the first linear module 102. As shown in FIG. 9, the displacement sensor 1012 may be fixed on the first linear module 102 and arranged to face the moving arm 103. After the moving arm 103 moves, the displacement sensor 1012 can measure the moving distance of the moving arm 103, and this moving distance is the displacement amount of the moving arm 103 on the first linear module 102.

[0019] As shown in FIGS. 7 to 9, the first positioning claw 104 is connected to the pressure sensor 106 via a spring 107, and the spring 107 serves as a buffer to prevent damage to the substrate W by the first positioning claw 104, so that the measured value of the pressure sensor 106 becomes more accurate.

[0020] One strip-shaped protrusion 1041 is arranged on each side of the first positioning claw 104, and two parallel rails 108 are arranged on the moving arm 103. The two strip-shaped protrusions 1041 are respectively connected to the two rails 108, so that the first positioning claw 104 can slide along the rails 108.

[0021] Two rollers 109 are respectively provided on the first positioning claw 104 and the second positioning claw 105, and the rolling surfaces of the rollers 109 are used for abutting against the end of the substrate W. Since rolling friction occurs between the roller 109 and the end of the substrate W when the first positioning claw 104 presses and rotates the substrate W, the end of the substrate W is not easily damaged.

[0022] Instead of the roller 109, circular balls embedded in the leading ends of the first positioning claw 104 and the second positioning claw 105 may be used.

[0023] The deviation measuring device of this embodiment further comprises a second linear module 1011, which is connected to a reference arm 101. The reference arm 101 and the movable arm 103 are driven by the second linear module 1011 and the first linear module 102, respectively, and can move along a straight line L. After measuring the deviation between the center of the substrate W and the standard center, the center of the substrate W and the standard center can be aligned by moving the reference arm 101 and the movable arm 103 in synchronization with the substrate W in order to move the center of the substrate W to the standard center.

[0024] The displacement of the reference arm 101 on the second linear module 1011 may be read directly, or the displacement of the reference arm 101 on the second linear module 1011 may be obtained using a displacement sensor 1012. As shown in Figure 9, the displacement sensor 1012 may be fixed on the second linear module 1011 and positioned opposite the reference arm 101. When the reference arm 101 moves, the displacement sensor 1012 can measure the distance the reference arm 101 moves. This distance is the displacement of the reference arm 101 on the second linear module 1011.

[0025] <Second Embodiment> As shown in Figures 10 and 12, embodiments of the present invention disclose a deviation measuring device for measuring the deviation between the center of a substrate and a standard center. The deviation measuring device includes a reference arm 201, a first linear module 202, and a movable arm 203. A positioning claw 204 is provided on the reference arm 201, and the positioning claw 204 is configured to contact two points on the edge of the substrate. A contact head 205 and a pressure sensor 206 are arranged on the movable arm 203. The contact head 205 is configured to contact one point on the edge of the substrate, and the pressure sensor 206 is connected to the contact head 205 to measure the pressure between the edge of the substrate and the contact head 205. The movable arm 203 is positioned opposite the reference arm 201, and the line connecting the center of the positioning claw 204 and the center of the contact head 205 is a straight line L passing through the standard center. The first linear module 202 is connected to the movable arm 203, and the movable arm 203 can be driven by the first linear module 202 to move along the straight line L. The moving arm 203 pushes the substrate, bringing the edges of the substrate into contact with the positioning claw 204 and the contact head 205. At this time, the center of the substrate is located on a straight line L, and the deviation between the center of the substrate and the standard center can be calculated based on the coordinates of the reference arm 201 and the moving arm 203.

[0026] As shown in Figure 11, the contact head 205 is connected to the pressure sensor 206 via a spring 207. The movable arm 203 is provided with a slide groove 2010, allowing the contact head 205 to slide along the slide groove 2010. To prevent the contact head 205 from damaging the edges of the substrate, a roller 209 is placed on the contact head 205, with the roller surface of the roller 209 in contact with the edges of the substrate. When the substrate and the contact head 205 slide relative to each other during the contact process, the friction between the substrate and the contact head 205 becomes rolling friction rather than sliding friction, thereby reducing damage to the edges of the substrate. Instead of the roller 209, a circular ball embedded in the front of the contact head 205 may be used.

[0027] Measuring the deviation between the center of the substrate and the standard center using the apparatus of this embodiment includes the following steps. In step S1, the substrate W is lifted horizontally by a support mechanism (not shown) and brought into contact with the positioning claw 204. The support mechanism described above may be a smooth, horizontal platform or a floating platform. In step S2, the position of the reference arm 201 is fixed, and the moving arm 203 starts moving from its initial coordinates, is driven by the first linear module 202 and moves along the straight line L, with the contact head 205 pushing the substrate W until the positioning claw 204 and the contact head 205 simultaneously contact the edge of the substrate W. In step S3, the moving arm 203 moves slowly along the straight line L, and during this process, the pressure sensor 206 measures the pressure in real time. In step S4, when the pressure reaches the set value or set range, the moving arm 203 stops moving and maintains the pressure within the set value or set range. At this time, the moving arm 203 is positioned at the end coordinates. In step S5, the diameter d1 of the substrate W is calculated, and the deviation n between the center of the substrate W and the standard center is determined. The formula for this calculation is as follows: JPEG0007869250000002.jpg4682

[0028] Here, d0 is the standard diameter, the shape of the positioning claw 204 is V-shaped, θ is half the opening angle of the positioning claw 204, m = Δ1 - Δ0, Δ1 is the travel distance between the initial and end coordinates of the moving arm 203, and Δ0 is the standard travel distance of the moving arm 203. The standard travel distance is determined in advance, and the method for determining it is as follows: A substrate with a standard diameter d0 is used as the substrate in the measurement step, steps S1 to S4 are performed, and the travel distance between the initial and end coordinates of the moving arm 203 obtained is taken as the standard travel distance.

[0029] In step S2, the positioning claw 204 and the contact head 205 make contact with three points on the edge of the substrate, and the line connecting these three points forms an isosceles triangle, so the center of the circular substrate is located on the straight line L.

[0030] The following explains the calculation principle for the substrate diameter d1 and the deviation n between the substrate center and the standard center, using the case of a standard diameter of 300 mm as an example.

[0031] As shown in Figure 13, the dotted circle represents a standard substrate with a diameter d0 of 300 mm, the solid circle represents a substrate with an unknown diameter (diameter d1), and the folded line on the right represents the V-shaped positioning claw 204. O is the standard center, i.e., the center of the standard substrate, and P is the center of the substrate with an unknown diameter. Point A is the contact point between the contact head 205 and the standard substrate, point B is the contact point between the contact head 205 and the substrate with an unknown diameter, point C is the contact point between the standard substrate and the positioning claw 204, and point D is the contact point between the substrate with an unknown diameter and the positioning claw 204. The length of AB is defined as m, where m is a directional quantity. When d1 < 300, m > 0, and when d1 > 300, m < 0. The length of OP is defined as n, where n is also a directional quantity. When P is to the right of O, n > 0, and when P is to the left of O, n < 0. The angle θ is half the opening angle of the positioning claw 204.

[0032] The relationship between the deviation n and the diameter d1 of an unknown substrate can be obtained from Figure 13. JPEG0007869250000003.jpg1868

[0033] From Figure 13, we can see that m follows the following equation. JPEG0007869250000004.jpg1787

[0034] Combining the two equations above, we can obtain the following result. JPEG0007869250000005.jpg15100

[0035] Therefore, after first measuring the diameter d1 of the substrate according to equation (3), the deviation n between the center of the substrate with an unknown diameter and the standard center can be determined according to equation (1).

[0036] The apparatus of this embodiment further includes a second linear module 2011. The second linear module 2011 is connected to a reference arm 201. The reference arm 201 and the moving arm 203 are driven by the second linear module 2011 and the first linear module 202, respectively, and can move along a straight line L. After measuring the deviation between the center of the substrate W and the standard center, the center of the substrate W can be aligned with the standard center by moving the reference arm 201 and the moving arm 203 in synchronization with the substrate W in order to move the center of the substrate W to the standard center.

[0037] The displacement of the first linear module 202 and the second linear module 2011 may be read directly, or it may be measured by displacement sensors mounted on the first linear module 202 and the second linear module 2011. Specifically, the displacement sensor of the first linear module 202 is positioned opposite the moving arm 203 and configured to measure the distance the moving arm 203 travels, and the displacement sensor of the second linear module 2011 is positioned opposite the reference arm 201 and configured to measure the distance the reference arm 201 travels.

[0038] In summary, the present invention discloses relevant technology in a specific and detailed manner so that it can be reasonably implemented by those skilled in the art through the embodiments and related drawings described above. The embodiments described above are for illustrative purposes only and do not limit the present invention, and the scope of the present invention shall be defined by the claims. Changes in the number of components described herein or substitution with equivalent components shall still remain within the scope of the present invention.

Claims

1. A deviation measuring device for measuring the deviation between the center of a substrate and the standard center, It comprises a reference arm, a moving arm, and a first linear module. The moving arm is provided with a first positioning claw, which contacts two points on the end of the substrate. The reference arm is provided with a second positioning claw, which contacts two points on the end of the substrate. The moving arm is positioned opposite the reference arm, and the line connecting the center of the first positioning claw and the center of the second positioning claw is a straight line L, and the straight line L passes through the standard center, A deviation measuring device wherein the first linear module is connected to the moving arm, the moving arm is driven by the first linear module to move along the straight line L, the first positioning claw pushes the substrate until the first positioning claw and the second positioning claw simultaneously contact the edge of the substrate, at which point the center of the substrate is located on the straight line L, the deviation between the center of the substrate and the standard center is calculated based on the coordinates of the reference arm and the moving arm, and the substrate is a circular or elliptical substrate.

2. The deviation measuring device according to claim 1, further comprising a pressure sensor positioned on the moving arm, wherein the pressure sensor is connected to a first positioning claw to measure the pressure between the end of the substrate and the first positioning claw.

3. The deviation measuring device according to claim 2, wherein the first positioning claw is connected to the pressure sensor via a spring.

4. The deviation measuring device according to claim 3, wherein a strip-shaped projection is arranged on each side of the first positioning claw, two parallel rails are arranged on the moving arm, and the two strip-shaped projections are connected to the two rails, respectively, so that the first positioning claw slides along the rails.

5. The deviation measuring device according to claim 1, wherein the first positioning claw and the second positioning claw are each provided with two rolling elements, and the rolling surfaces of the rolling elements are used to contact the edge of the substrate.

6. The deviation measuring device according to claim 5, wherein the rolling element is a roller.

7. The deviation measuring device according to claim 1, further comprising a second linear module, the second linear module being connected to the reference arm, the reference arm being driven by the second linear module to move along the straight line L, and the reference arm and the moving arm moving in sync with the substrate to align the center of the substrate with the standard center.

8. The deviation measuring device according to claim 7, wherein both the displacement of the moving arm on the first linear module and the displacement of the reference arm on the second linear module are directly read.

9. The deviation measuring device according to claim 7, wherein the first linear module is fixed to a displacement sensor, the displacement sensor is positioned opposite the moving arm and configured to measure the distance the moving arm travels, and the second linear module is fixed to the displacement sensor, the displacement sensor is positioned opposite the reference arm and configured to measure the distance the reference arm travels.

10.

11. The deviation measuring device according to claim 10, wherein the contact head is connected to the pressure sensor via a spring.

12. The deviation measuring device according to claim 10, wherein the movable arm is provided with a slide groove, and the contact head slides along the slide groove.

13. The deviation measuring device according to claim 10, wherein the contact head is provided with rolling elements, and the rolling surface of the rolling elements is used to contact the edge of the substrate.

14. The deviation measuring device according to claim 13, wherein the rolling element is a roller.

15. The deviation measuring device according to claim 10, further comprising a second linear module, the second linear module being connected to the reference arm, the reference arm being driven by the second linear module to move along the straight line L, and the reference arm and the moving arm moving in sync with the substrate to align the center of the substrate with the standard center.

16. The deviation measuring device according to claim 15, wherein both the displacement of the moving arm on the first linear module and the displacement of the reference arm on the second linear module are directly read.

17. The deviation measuring device according to claim 15, wherein the first linear module is fixed to a displacement sensor, the displacement sensor is positioned opposite the moving arm and configured to measure the distance the moving arm travels, and the second linear module is fixed to the displacement sensor, the displacement sensor is positioned opposite the reference arm and configured to measure the distance the reference arm travels.

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