Autocollimator calibration method and system

Abstract

The invention relates to the technical field of optics, and discloses an autocollimator calibration method and system so as to ensure the detection precision. The method comprises the following steps: deploying an auxiliary calibration structure on a peripheral emergent collimated light beam of the autocollimator; the auxiliary calibration structure comprises two reflecting surfaces which are integrally formed and are not perpendicular to each other, an included angle between the two reflecting surfaces is a known standard included angle, and the standard included angle is covered by light spots of collimated light beams emitted from the periphery of the autocollimator to form an upper sub-light beam and a lower sub-light beam of an angular bisector; the control host acquires images of light beams generated by the light source, which are respectively reflected by the two reflecting surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and counts the number of pixels between central points of two cross curves in the acquired images; then, the deflection angle corresponding to the unit pixel is calibrated according to the known standard included angle of the auxiliary calibration structure and the counted pixel number, and finally, the angle change of the measured object is tracked according to the deflection angle corresponding to the unit pixel and the change of the pixel number.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to an autocollimator calibration method and system. Background Art

[0002] An autocollimator is a measuring instrument that converts angle measurements into linear measurements using the principle of light self-collimation. Figure 1 As shown in the figure, the autocollimator includes a light source, a cross-reticle, a beam splitter, an objective lens, a photoelectric sensor and a control host. The photosensitive surface of the photoelectric sensor (usually a CCD camera can be used) is located on the focal plane of the objective lens, and the distance between the photosensitive surface of the photoelectric sensor and the cross-reticle and the objective lens is the focal length of the objective lens. When the reflector pitches and yaws, the crosshairs on the photosensitive surface move, and the frame offset value can be measured by the moving distance. Summary of the Invention

[0003] The present invention aims to disclose a method and system for calibrating an autocollimator to ensure detection accuracy.

[0004] To achieve the above-mentioned purpose, the present invention discloses a method for calibrating an autocollimator, wherein the autocollimator includes a light source, a cross-reticle, a beam splitter, an objective lens, a photoelectric sensor, and a control host. The distance between the photosensitive surface of the photoelectric sensor and the cross-reticle and the objective lens is the focal length of the objective lens. The method comprises:

[0005] Step S1: deploying an auxiliary calibration structure on the collimated light beam emitted from the periphery of the autocollimator; the auxiliary calibration structure is formed by two integrally formed non-perpendicular reflective surfaces, the angle between the two reflective surfaces is a known standard angle, and the standard angle is covered by the spot of the collimated light beam emitted from the periphery of the autocollimator to form two upper and lower sub-beams of the angle bisector;

[0006] Step S2, the control host obtains an image of the light beam generated by the light source after being reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and counts the number of pixels between the center points of the two cross lines in the collected image;

[0007] Step S3: The control host calibrates the deflection angle corresponding to a unit pixel according to the standard angle known by the auxiliary calibration structure and the number of pixels counted. The specific calculation formula is: the absolute value of the difference between the standard angle known by the auxiliary calibration structure and 90° × 4 ÷ the number of pixels counted = the deflection angle corresponding to the unit pixel of the autocollimator;

[0008] Step S4: The control host tracks the angle change of the measured object according to the change of the deflection angle and the number of pixels corresponding to the unit pixel.

[0009] Preferably, the method of the present invention further comprises:

[0010] Step S5, adjusting the pitch angle of the auxiliary calibration structure so that the light beam generated by the light source is respectively reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the two cross lines in the image of the photoelectric sensor, and calculating whether the number of pixels between the center points of the two cross lines in different areas corresponding to at least two different pitch angles of the auxiliary calibration structure meets the first type consistency error. If so, the autocollimator is determined to be qualified; otherwise, it is determined to be unqualified.

[0011] Preferably, the method of the present invention further comprises:

[0012] Step S6: Determine whether the difference between the deflection angles corresponding to at least two unit pixels satisfies the second type of consistency error by replacing auxiliary calibration structures with different standard angles. If so, the autocollimator is determined to be qualified; otherwise, it is determined to be unqualified.

[0013] To achieve the above-mentioned objectives, the present invention further discloses an autocollimator calibration system, comprising a light source, a cross-reticle, a beam splitter, an objective lens, a photoelectric sensor, and a control host, wherein the distance between the photosensitive surface of the photoelectric sensor and the cross-reticle and the objective lens is equal to the focal length of the objective lens; and further comprising an auxiliary calibration structure disposed on the collimated light beam emitted from the periphery of the autocollimator; the auxiliary calibration structure is formed as two integrally formed reflecting surfaces in a non-perpendicular relationship, the angle between the two reflecting surfaces being a known standard angle, and the standard angle being covered by the light spot of the collimated light beam emitted from the periphery of the autocollimator to form two upper and lower sub-beams of the angle bisector;

[0014] The control host is used to obtain an image of the light beam generated by the light source after being reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and count the number of pixels between the center points of the two cross lines in the captured image; then, the deflection angle corresponding to the unit pixel is calibrated according to the standard angle known to the auxiliary calibration structure and the counted number of pixels; the specific calculation formula is: the absolute value of the difference between the standard angle known to the auxiliary calibration structure and 90° × 4 ÷ the counted number of pixels = the deflection angle corresponding to the unit pixel of the autocollimator; then, the angular change of the object under test is tracked according to the changes in the deflection angle corresponding to the unit pixel and the number of pixels.

[0015] Similarly, preferably, the control host is further configured to assist in performing: adjusting the pitch angle of the auxiliary calibration structure so that the light beams generated by the light source are displaced after being reflected by the two reflecting surfaces of the auxiliary calibration structure respectively, and calculating whether the number of pixels between the centers of the two cross lines in different regions corresponding to at least two different pitch angles of the auxiliary calibration structure satisfies a first consistency error, and if so, determining that the autocollimator is qualified, otherwise, determining that the autocollimator is unqualified.

[0016] Further, the control host is further configured to assist in performing: judging whether the difference between the deflection angles corresponding to at least two unit pixels satisfies a second consistency error by replacing the auxiliary calibration structures with different standard included angles, and if so, determining that the autocollimator is qualified, otherwise, determining that the autocollimator is unqualified.

[0017] The present application has the following beneficial effects:

[0018] The crosshair plate itself can be regarded as a horizontal bundle and a vertical bundle; under the focusing effect of the objective lens, the shape observed on the photosensitive surface of the photosensor is a cross line; if the included angle between the two reflecting surfaces of the auxiliary calibration structure is 90°, and if the standard included angle of 90° is covered by the light spots of the peripheral outgoing collimated light beams of the autocollimator to form the upper and lower two sub-beams of the angle bisector, then the two superimposed cross lines observed on the photosensitive surface of the photosensor are observed; when the included angle between the two reflecting surfaces is not 90°, the cross shape reflected back to the photosensitive surface by the upper half sub-beam incident to the auxiliary calibration structure is shifted in the other direction, and at the same time, the cross shape reflected back to the photosensitive surface by the lower half sub-beam incident to the auxiliary calibration structure is shifted in the opposite direction, thereby forming two cross shapes with similar brightness and distinct from the virtual image. Based on the foregoing principle, the deflection angle corresponding to the unit pixel of the autocollimator can be accurately calculated by the absolute value of the difference between the standard included angle of the auxiliary calibration structure and 90° multiplied by 4 divided by the number of pixels counted; and the detection accuracy of the autocollimator when tracking the angle change of the measured object according to the change of the deflection angle corresponding to the unit pixel and the number of pixels can be ensured.

[0019] The present application will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, and are incorporated in and constitute a part of this application. The embodiments of the application illustrated in the drawings are provided to explain the present application and are not meant to limit the present application. In the drawings:

[0021] Figure 1 is a schematic diagram of the structure and principle of the autocollimator disclosed in the background art of the present application.

[0022] Figure 2 It is a flow chart of the autocollimator calibration method disclosed in an embodiment of the present invention.

[0023] Figure 3 FIG. 1 is a diagram illustrating an optical path with two reflectors at 90° in the auxiliary calibration structure disclosed in an embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram of the optical path of the two reflectors of the auxiliary calibration structure disclosed in an embodiment of the present invention at 91 degrees.

[0025] Figure 5 is based on Figure 4 The image observed by the auxiliary calibration structure on the photosensitive surface of the photoelectric sensor.

[0026] Figure 6 It is a schematic diagram of the optical path for adjusting the pitch angle of the auxiliary calibration structure to detect the first type of consistency. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0028] Example 1

[0029] This embodiment discloses a method for calibrating an autocollimator, referring to Figure 1 The autocollimator includes a light source, a cross-reticle plate, a beam splitter, an objective lens, a photoelectric sensor and a control host. The distance between the photosensitive surface of the photoelectric sensor and the cross-reticle plate and the objective lens is the focal length of the objective lens.

[0030] like Figure 2 As shown, the method of this embodiment includes:

[0031] Step S1: Deploy an auxiliary calibration structure on the collimated light beam emitted from the periphery of the autocollimator; the auxiliary calibration structure is composed of two integrally formed non-perpendicular reflective surfaces, the angle between the two reflective surfaces is a known standard angle, and the standard angle is covered by the light spot of the collimated light beam emitted from the periphery of the autocollimator to form two upper and lower sub-beams of the angle bisector.

[0032] In this step, preferably, the angle bisector coincides with the optical axis of the collimated light beam emitted from the periphery of the autocollimator, so that the brightness and line width of the two cross lines observed subsequently are consistent; however, in the actual calibration environment, it is not required that the upper and lower sub-beams are symmetrical based on the optical axis.

[0033] like Figure 3 As shown in the figure, if there are two reflectors with a 90° angle between them, the light is incident horizontally and the reflected light beam is also reflected back horizontally. What is observed on the photosensitive surface of the photoelectric sensor is two overlapping cross lines.

[0034] like Figure 4 As shown in the figure, if we replace the two reflectors with a known 91° angle, the light beam above the optical axis is incident horizontally, and the reflected light beam forms a 2° angle with the horizontal line. Similarly, if the light beam below the optical axis is incident horizontally, the reflected light beam above also forms a 2° angle with the horizontal line.

[0035] Step S2: The control host obtains an image of the light beam generated by the light source after being reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and counts the number of pixels between the two cross-line center points in the collected image.

[0036] In this step, the autocollimator is a beam of collimated light. When this beam of light is horizontally incident on the 91° angled glass, it will reflect two beams of light with an angle of 4° between them. Two crosses will appear in the autocollimator, and the center distance between the two crosses is 4°. Correspondingly, what is observed on the photosensitive surface of the photoelectric sensor is Figure 5 Two spaced crosshairs are shown.

[0037] It is worth noting that in Figure 5 There are also some darker straight lines, which are usually images formed by additional reflection paths and are ghost images caused by the system itself.

[0038] Step S3: The control host calibrates the deflection angle corresponding to the unit pixel according to the known standard angle of the auxiliary calibration structure and the number of pixels counted.

[0039] In this step, the specific calculation formula is: the absolute value of the difference between the known standard angle of the auxiliary calibration structure and 90°×4÷the number of counted pixels=the deflection angle corresponding to the unit pixel of the autocollimator.

[0040] Step S4: The control host tracks the angle change of the object under test according to the change of the deflection angle and the number of pixels corresponding to the unit pixel. Optionally, the object under test refers to the detection target of the autocollimator in the actual application scenario after the deflection angle corresponding to the actual unit pixel is calibrated, which is not related to the above-mentioned auxiliary calibration structure, including but not limited to Figure 1 The rotation angle of the mirror is shown.

[0041] In this embodiment, auxiliary calibration structures with different angles can be selected when calibrating autocollimators of different accuracies. Generally, the higher the precision of the autocollimator, the smaller the field of view angle. If an auxiliary calibration structure with a large angle is used, the two crosses may not be recognized. For example, if the measurable angle within the field of view of a high-precision autocollimator is ±0.1°, and a 90.2° auxiliary calibration structure is selected, the two crosses are theoretically 0.4° apart. In this case, the two crosses cannot be presented in the autocollimator, making calibration impossible.

[0042] If the selected autocollimator has low accuracy and the angle of the auxiliary calibration structure is close to 90°, calibration cannot be performed. For example, if the deflection angle represented by one pixel of the autocollimator is 1", and the selected auxiliary calibration structure is 90°2", theoretically the distance between the centers of the two crosses is 4", that is, 4 pixels. In this case, the calibration result is inaccurate. It is recommended that the angle of the auxiliary calibration structure be at least 50 times the minimum resolution of the autocollimator, that is, occupy at least 50 pixels. For an autocollimator with an angle of 1", an auxiliary calibration structure of 90°25" or more should be used.

[0043] Furthermore, the method of this embodiment also includes:

[0044] Step S5, adjusting the pitch angle of the auxiliary calibration structure so that the light beam generated by the light source is respectively reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the two cross lines in the image of the photoelectric sensor, and calculating whether the number of pixels between the center points of the two cross lines in different areas corresponding to at least two different pitch angles of the auxiliary calibration structure meets the first kind of consistency error. If so, the autocollimator is judged to be qualified, otherwise it is judged to be unqualified.

[0045] For example, using a 91° auxiliary calibration structure, the center pixel of the two crosses is obtained as 100 based on the above step S3. Then adjust the pitch angle of the auxiliary calibration structure to change the incident angle of the light, such as Figure 6 As shown, beam 1 is the optical path in the plane of the auxiliary calibration structure, and beam 2 is the optical path diagram for adjusting the pitch angle of the auxiliary calibration structure so that the incident light presents an angle. Beam 2 is the overall translation of beam 1. In theory, the angle between the line connecting the two crosses and the horizontal direction does not change, and the center distance between the two crosses is still 100 pixels. In practice, in order to test the consistency of the autocollimator, this method is used to determine whether the autocollimation is qualified by setting the tolerance. For example, when beam 1 tests the two crosses at 100 pixels, when beam 2 is in position, the two crosses are 105 pixels apart, and the qualified standard is ±2 pixels, then the autocollimator is judged to be unqualified. This method can be used to measure the consistency of the autocollimator multiple times, such as dividing the autocollimation field of view into 4 blocks, 8 blocks, etc., and adjusting the pitch angle of the auxiliary calibration structure so that the two spaced crosses fall on different areas one after another, and finally judging whether the autocollimator is qualified.

[0046] Preferably, the method of the present invention further comprises:

[0047] Step S6: By replacing auxiliary calibration structures with different standard angles, determine whether the difference between the deflection angles corresponding to at least two unit pixels meets the second type consistency error. If so, the autocollimator is determined to be qualified; otherwise, it is determined to be unqualified.

[0048] The distance between the centers of the two crosses observed by the photoelectric sensor's light-sensitive surface varies for auxiliary calibration structures with different angles. For example, if the auxiliary calibration structure with a 91° angle has a center distance of 100 pixels, replacing it with a 92° auxiliary calibration structure will theoretically have a center distance of 200 pixels.

[0049] The above method of this embodiment can be directly used by equipment manufacturers to calibrate the autocollimator before leaving the factory.

[0050] For the purchaser, if the device manufacturer calibrates the deflection angle corresponding to the unit pixel based on its own method, the above method of this embodiment can be used for compensation. The background and principle of the specific compensation are detailed as follows:

[0051] In an autocollimator, if ΔS represents the size of a pixel, f represents the focal length of the objective lens, and A represents the deflection angle of the reflector, the deflection angle represented by one pixel can be calculated using the formula ΔS = f·tan(2A). Because the angle A is very small, 2A = tan2A is often used. This approximation results in a loss of accuracy, as using tan2A will result in a residual decimal point.

[0052] Factors that affect the accuracy of the autocollimator include the objective lens and the camera pixel size. For example, the theoretical pixel size is 2um, but the actual pixel size is 3um, or a lens with a 1000mm focal length is only 950mm. In this case, there will be a large gap between theory and practice. To compensate for this gap, auxiliary calibration structures are usually used after assembling an autocollimator.

[0053] The compensation logic is as follows: using an auxiliary calibration structure with a known angle (such as 91°), the theoretical distance between the two crosses in the autocollimator can be calculated. For example, for a 91° auxiliary calibration structure, the theoretical autocollimator should have 100 pixels, which is 4° / 100 = 0.04° / pixel. When the auxiliary calibration structure is actually used for calibration, there are only 80 pixels, so the difference is 4° / 80 = 0.05° / pixel. At this point, the gap between theory and practice is known. The angle calculated in software is usually the number of pixels × the angle represented by each pixel = the measured angle (i.e., the specific calculation example corresponding to step S4 above). To this end, the angle represented by each pixel needs to be corrected. For example, 0.04 can be changed to 0.05 to ensure accurate measurement performance. On the contrary, if only the theoretical value is filled in, the test result will differ from the actual angle by 1.25 times.

[0054] Example 2

[0055] This embodiment discloses an autocollimator calibration system, comprising a light source, a cross-reticle, a beam splitter, an objective lens, a photoelectric sensor, and a control host. The distance between the photosensitive surface of the photoelectric sensor and the cross-reticle and the objective lens is equal to the focal length of the objective lens. The system also includes an auxiliary calibration structure disposed on the peripheral collimated light beam emitted from the autocollimator. The auxiliary calibration structure is formed as two integrally formed reflective surfaces in a non-perpendicular relationship. The angle between the two reflective surfaces is a known standard angle, and the standard angle is covered by the light spot of the peripheral collimated light beam emitted from the autocollimator to form two sub-beams above and below the angle bisector. Preferably, the angle bisector coincides with the optical axis of the peripheral collimated light beam emitted from the autocollimator.

[0056] The control host is used to obtain an image of the light beam generated by the light source after being reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and count the number of pixels between the center points of the two cross lines in the collected image; then, the deflection angle corresponding to the unit pixel is calibrated based on the standard angle known by the auxiliary calibration structure and the counted number of pixels; the specific calculation formula is: the absolute value of the difference between the standard angle known by the auxiliary calibration structure and 90° × 4 ÷ the counted number of pixels = the deflection angle corresponding to the unit pixel of the autocollimator; then, the angular changes of the object under test are tracked based on the changes in the deflection angle corresponding to the unit pixel and the number of pixels.

[0057] Similarly, referring to the above-mentioned embodiment 1, the control host of this embodiment can also be used to assist in the execution of: adjusting the pitch angle of the auxiliary calibration structure, so that the light beam generated by the light source is respectively reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the two cross lines in the image of the photoelectric sensor to be displaced, and calculating whether the number of pixels between the center points of the two cross lines in different areas corresponding to at least two different pitch angles of the auxiliary calibration structure meets the first type of consistency error. If so, the autocollimator is judged to be qualified, otherwise it is judged to be unqualified.

[0058] Furthermore, the control host of this embodiment can also be used to assist in the execution: by replacing auxiliary calibration structures with different standard angles to determine whether the difference in deflection angles corresponding to at least two unit pixels satisfies the second type of consistency error. If so, the autocollimator is determined to be qualified, otherwise it is determined to be unqualified.

[0059] In summary, the methods and systems disclosed in the above two embodiments of the present invention respectively have at least the following beneficial effects:

[0060] The cross scale plate itself can be regarded as a horizontal bundle and a vertical bundle; under the focusing effect of the objective lens, the shape observed on the photosensitive surface of the photoelectric sensor is a cross line; if the angle between the two reflecting surfaces of the auxiliary calibration structure of the application is 90°, if the standard angle of 90° is covered by the light spot of the peripheral outgoing collimated beam of the autocollimator to form the upper and lower two sub-beams of the angle bisector, then the two superimposed cross lines observed on the photosensitive surface of the photoelectric sensor are observed; when the angle between the two reflecting surfaces is not 90°, the cross shape reflected back to the photosensitive surface by the upper half of the sub-beam incident to the auxiliary calibration structure will be offset in other directions, at the same time, the cross shape reflected back to the photosensitive surface by the lower half of the sub-beam incident to the auxiliary calibration structure will be offset in the opposite direction, thereby forming two cross shapes with close brightness and clear distinction from the virtual image. Based on the foregoing principle, the absolute value of the difference between the standard angle of the auxiliary calibration structure and 90°×4÷ the number of pixels counted can be accurately calculated to obtain the deflection angle corresponding to a unit pixel of the autocollimator; thereby the detection accuracy of the autocollimator when tracking the angle change of the measured object according to the change of the deflection angle corresponding to a unit pixel and the number of pixels can be ensured.

[0061] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calibrating an autocollimator, wherein the autocollimator comprises a light source, a cross-reticle, a beam splitter, an objective lens, a photoelectric sensor, and a control host, wherein the distance between the photosensitive surface of the photoelectric sensor and the cross-reticle and the objective lens is the focal length of the objective lens; The method comprises: Step S1: deploying an auxiliary calibration structure on the collimated light beam emitted from the periphery of the autocollimator; the auxiliary calibration structure is formed by two integrally formed non-perpendicular reflective surfaces, the angle between the two reflective surfaces is a known standard angle, and the standard angle is covered by the spot of the collimated light beam emitted from the periphery of the autocollimator to form two upper and lower sub-beams of the angle bisector; Step S2, the control host obtains an image of the light beam generated by the light source after being reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and counts the number of pixels between the center points of the two cross lines in the collected image; Step S3: The control host calibrates the deflection angle corresponding to a unit pixel according to the standard angle known by the auxiliary calibration structure and the number of pixels counted. The specific calculation formula is: the absolute value of the difference between the standard angle known by the auxiliary calibration structure and 90° × 4 ÷ the number of pixels counted = the deflection angle corresponding to the unit pixel of the autocollimator; Step S4: The control host tracks the angle change of the measured object according to the change of the deflection angle and the number of pixels corresponding to the unit pixel.

2. The autocollimator calibration method according to claim 1, characterized in that: Also includes: Step S5, adjusting the pitch angle of the auxiliary calibration structure so that the light beam generated by the light source is respectively reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the two cross lines in the image of the photoelectric sensor, and calculating whether the number of pixels between the center points of the two cross lines in different areas corresponding to at least two different pitch angles of the auxiliary calibration structure meets the first type consistency error. If so, the autocollimator is determined to be qualified; otherwise, it is determined to be unqualified.

3. The autocollimator calibration method according to claim 1 or 2, characterized in that: Also includes: Step S6: Determine whether the difference between the deflection angles corresponding to at least two unit pixels satisfies the second type of consistency error by replacing auxiliary calibration structures with different standard angles. If so, the autocollimator is determined to be qualified; otherwise, it is determined to be unqualified.

4. An autocollimator calibration system, comprising a light source, a cross-reticle, a beam splitter, an objective lens, a photoelectric sensor, and a control host, wherein the distance between the photosensitive surface of the photoelectric sensor and the cross-reticle and the objective lens is the focal length of the objective lens; characterized in that: The apparatus further includes an auxiliary calibration structure disposed on the collimated light beam emitted from the periphery of the autocollimator; the auxiliary calibration structure is formed of two integrally formed reflecting surfaces in a non-perpendicular relationship, the angle between the two reflecting surfaces being a known standard angle, and the standard angle being covered by the light spot of the collimated light beam emitted from the periphery of the autocollimator to form two upper and lower sub-beams of the angle bisector; The control host is used to obtain an image of the light beam generated by the light source after being reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the photoelectric sensor, and count the number of pixels between the center points of the two cross lines in the captured image; then, the deflection angle corresponding to the unit pixel is calibrated according to the standard angle known to the auxiliary calibration structure and the counted number of pixels; the specific calculation formula is: the absolute value of the difference between the standard angle known to the auxiliary calibration structure and 90° × 4 ÷ the counted number of pixels = the deflection angle corresponding to the unit pixel of the autocollimator; then, the angular change of the object under test is tracked according to the changes in the deflection angle corresponding to the unit pixel and the number of pixels.

5. The autocollimator calibration system according to claim 4, characterized in that: The control host is also used to assist in the execution of: adjusting the pitch angle of the auxiliary calibration structure so that the light beam generated by the light source is reflected by the two reflective surfaces of the auxiliary calibration structure and then imaged on the two cross lines in the image of the photoelectric sensor to be displaced, and calculating whether the number of pixels between the center points of the two cross lines in different areas corresponding to at least two different pitch angles of the auxiliary calibration structure meets the first type of consistency error. If so, the autocollimator is judged to be qualified; otherwise, it is judged to be unqualified.

6. The autocollimator calibration system according to claim 4 or 5, characterized in that: The control host is also used to assist in the execution of: determining whether the difference in deflection angles corresponding to at least two unit pixels satisfies the second type of consistency error by replacing auxiliary calibration structures with different standard angles; if so, the autocollimator is determined to be qualified; otherwise, it is determined to be unqualified.

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