Prism flatness calibration device and calibration method based on laser interferometer

Abstract

The invention discloses a prism flatness calibration device and calibration method based on a laser interferometer, the prism flatness calibration device comprises a laser interferometer mechanism, a spectroscope module, a standard optical flat and a prism to be calibrated are sequentially arranged below the laser interferometer mechanism, the standard optical flat is connected with a third fine tuning assembly, and the third fine tuning assembly is connected with a second fine tuning assembly. Three lifting fine adjustment assemblies are arranged at the lower end of the prism to be calibrated, the lifting fine adjustment assemblies are used for adjusting the levelness of the prism to be calibrated, the three lifting fine adjustment assemblies are distributed in an isosceles triangle shape, and the distance from the lifting fine adjustment assembly located on the vertex angle of the isosceles triangle to the bottom edge of the isosceles triangle is bmm. The distance from one lifting fine adjustment assembly located at the base angle of the isosceles triangle to the waist of the isosceles triangle is a mm, bgt; a. Compared with the prior art, laser interference fringe definition adjustment is divided into coarse adjustment and fine adjustment, and the laser interference fringe definition can be rapidly improved; and light intensity adjustment is added between coarse adjustment and fine adjustment, so that the adjustment speed is further increased.

Description

Technical Field

[0001] The present invention relates to the technical field of prism flatness calibration, and in particular to a prism flatness calibration device and a calibration method based on a laser interferometer. Background Art

[0002] With the continuous development of length measurement related technologies, prisms are widely used in the field of metrology as optical standards. When implementing calibration, the flatness of the prism working surface will directly affect the metrological characteristics of the standard and its stability during operation. According to metrology theory, when a prism is used as a standard, the flatness of its working surface must be calibrated to ensure the accuracy of the value traceability of the standard and the integrity of the traceability chain. During the calibration process of the flatness of the prism working surface, it is necessary to adjust the level of the prism; currently, three to four height adjustment mechanisms are generally set under the prism, and the height adjustment mechanisms are evenly distributed; then the level of the prism is adjusted through the height adjustment mechanism. In the actual adjustment process, this adjustment method is not efficient. Summary of the invention

[0003] The invention provides a prism flatness calibration device and a calibration method based on a laser interferometer, which are used to solve the problem of low levelness adjustment efficiency in the existing prism flatness calibration process.

[0004] The present invention provides a prism flatness calibration device based on laser interferometer, comprising a laser interferometer mechanism, wherein a beam splitter module, a standard flat crystal and a prism to be calibrated are arranged in sequence below the laser interferometer mechanism, the standard flat crystal is connected with a third fine-tuning component, and three lifting fine-tuning components are arranged at the lower end of the prism to be calibrated, wherein the lifting fine-tuning components are used to adjust the horizontality of the prism to be calibrated, and the three lifting fine-tuning components are distributed in an isosceles triangle, wherein the distance from the lifting fine-tuning component located at the vertex angle of the isosceles triangle to the base of the isosceles triangle is bmm, and the distance from a lifting fine-tuning component located at the base angle of the isosceles triangle to the waist of the isosceles triangle is amm, wherein b>a.

[0005] Preferably, the prism to be calibrated is mounted on a mounting plate via a prism mounting assembly, and the lifting and fine-tuning assembly is disposed below the mounting plate.

[0006] Preferably, the prism mounting assembly comprises a box body, in which a first positioning plate and a second positioning plate are hinged, and the first positioning plate and the second positioning plate are distributed in a V-shape.

[0007] Preferably, the first positioning plate and the second positioning plate are both provided with positioning balls, the positioning balls are connected with springs, and the box body is provided with adjustment holes matched with the positioning balls.

[0008] Preferably, the hinged end of the first positioning plate is provided with a first groove, the hinged end of the second positioning plate is provided with a protrusion matched with the first groove, and the hinge shaft fixed to the box body passes through the first positioning plate and the protrusion.

[0009] Preferably, a flatness measurement area is provided on the mounting plate, the flatness measurement area is circular, the box body is located in the flatness measurement area, and the lifting and fine-tuning components are distributed outside the flatness measurement area.

[0010] Preferably, the laser interferometer mechanism comprises a support plate and a laser interferometer module, and the laser interferometer module is mounted on the support plate via a first fine-tuning component.

[0011] Preferably, the support plate is provided with a visual module, and the visual module is located on one side of the spectroscope module.

[0012] The present invention also provides a prism flatness calibration method based on laser interferometer, comprising the prism flatness calibration device based on laser interferometer as described above, and further comprising the following steps:

[0013] S1: Place the standard flat crystal and the prism to be calibrated, so that the working surface of the prism to be calibrated faces upward and is perpendicular to the horizontal plane;

[0014] S2: Adjust the lifting and fine-tuning components located at the top corner of the isosceles triangle, observe the display window of the visual module, and roughly adjust the clarity of the laser interference fringes to reach the inflection point;

[0015] S3: adjusting the laser interferometer module and the first fine-tuning component, observing the display window of the visual module, and adjusting the light intensity so that the intensity contrast of the laser interference fringes is optimal;

[0016] S4: Adjust the lifting and fine-tuning component located on the bottom side of the isosceles triangle, observe the display window of the visual module, fine-tune the clarity of the laser interference fringes and reach a better inflection point, so that the number of laser interference fringes is no more than 3;

[0017] S5: Read the flatness of the working surface of the prism to be calibrated for the first time, the reading is x1nm;

[0018] S6: Adjust the standard flat crystal through the third fine-tuning component and observe the display window of the visual module so that the laser interference fringes gradually increase and then gradually decrease to a minimum;

[0019] S7: Read the flatness of the working surface of the prism to be calibrated for the second time, and the reading is x2nm;

[0020] S8: repeat steps S5 and S6, and read the flatness of the working surface of the prism to be calibrated for the third time, and the reading is x3nm;

[0021] S9: The flatness of the working surface of the prism to be calibrated is: [(x1+x2+x3) / 3]nm, and the calibration is completed.

[0022] Preferably, in step S1, the specific process of making the working surface of the prism to be calibrated face upward and perpendicular to the horizontal plane is: according to the structural size of the prism to be calibrated, the first positioning plate and the second positioning plate are rotated to a suitable angle and the positioning ball is inserted into the adjustment hole of the box body; then the prism to be calibrated is placed between the first positioning plate and the second positioning plate and their positions are adjusted so that the working surface of the prism to be calibrated faces upward and perpendicular to the horizontal plane.

[0023] Compared with the prior art, the laser interference fringe clarity adjustment in the present invention is divided into coarse adjustment and fine adjustment. The adjustment ability is strong in coarse adjustment and weak in fine adjustment, which can quickly improve the laser interference fringe clarity; and light intensity adjustment is added between coarse adjustment and fine adjustment, which further speeds up the adjustment speed. The flatness measurement value of the prism working surface is traced back to the standard flat crystal and the laser interferometer module, which effectively ensures the integrity of the value traceability chain and greatly improves the accuracy of the flatness measurement of the prism working surface. The present invention is simple to operate, and one calibration operator can implement calibration, which effectively ensures work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a structural schematic diagram of the present invention;

[0026] Figure 2 It is a structural schematic diagram of the prism mounting assembly of the present invention;

[0027] Figure 3 It is a structural schematic diagram of the first positioning plate of the present invention;

[0028] Figure 4 is a structural schematic diagram of a second positioning plate of the present invention;

[0029] Figure 5 This is a schematic diagram of the structure when adjusting the mounting plate of the present invention.

[0030] Reference numerals:

[0031] 1. Laser interferometer mechanism, 2. Beam splitter module, 3. Standard flat crystal, 4. Prism to be calibrated, 5. Third fine-tuning assembly, 6. Lifting and fine-tuning assembly, 7. Mounting plate, 8. Prism mounting assembly, 9. Vision module, 11. Support plate, 12. Laser interferometer module, 71. Flatness measurement area, 81. Box body, 82. First positioning plate, 83. Second positioning plate, 84. Positioning ball, 811. Adjustment hole, 821. First groove, 831. Protrusion, 100. Light-transmitting hole, 200. Support connecting plate, 300. Mounting platform, 400. Support arc plate, 500. Second fine-tuning assembly. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See attached Figure 1 The present embodiment provides a prism flatness calibration device based on a laser interferometer, comprising a laser interferometer mechanism 1, wherein a beam splitter module 2, a standard flat crystal 3 and a prism 4 to be calibrated are sequentially arranged below the laser interferometer mechanism 1, wherein the standard flat crystal 3 is connected to a third fine-tuning component 5, and the standard flat crystal 3 is fine-tuned and positioned by the third fine-tuning component 5; and three lifting and fine-tuning components 6 are arranged at the lower end of the prism 4 to be calibrated, and the lifting and fine-tuning components 6 are used to adjust the horizontality of the prism 4 to be calibrated, as shown in FIG. Figure 5 The three lifting and fine-tuning components 6 are distributed in an isosceles triangle. The distance from the lifting and fine-tuning component 6 located at the vertex of the isosceles triangle to the base of the isosceles triangle is bmm, and the distance from a lifting and fine-tuning component 6 located at the base angle of the isosceles triangle to the waist of the isosceles triangle is amm, where b>a.

[0034] As another embodiment of the present invention, the prism 4 to be calibrated is mounted on the mounting plate 7 through the prism mounting assembly 8, and the lifting and fine-tuning assembly 6 is arranged below the mounting plate 7. When the prism 4 to be calibrated is clamped and positioned in the prism mounting assembly 8, the working surface of the prism 4 to be calibrated is located at the top. Specifically, the mounting plate 7 is circular.

[0035] As another embodiment of the present invention: Figure 2 The prism mounting assembly 8 includes a box body 81, in which a first positioning plate 82 and a second positioning plate 83 are hinged, and the first positioning plate 82 and the second positioning plate 83 are distributed in a V shape.

[0036] As another embodiment of the present invention: Figure 3 and attached Figure 4 , a positioning ball 84 is provided on both the first positioning plate 82 and the second positioning plate 83, the positioning ball 84 is connected to a spring, and an adjustment hole 811 that matches the positioning ball 84 is provided on the box body 81. The positioning ball 84 is inserted into different adjustment holes 811 to adjust the angle between the first positioning plate 82 and the second positioning plate 83, so that not only the clamping of the right-angle prism can be achieved, but also the clamping and positioning of prisms of other angle types can be achieved. Specifically, the prism mounting assembly 8 also includes a limit plate, the positioning ball 84 is located between the limit plate and the spring, the diameter of the positioning hole on the limit plate is smaller than the diameter of the positioning ball 84, and the limit plate is installed on the first positioning plate 82 and the second positioning plate 83.

[0037] An embodiment of the first positioning plate 82 and the second positioning plate 83 being hinged in the box body 81: the hinged end of the first positioning plate 82 is provided with a first groove 821, the hinged end of the second positioning plate 83 is provided with a protrusion 831 adapted to the first groove 821, and the hinge shaft fixed to the box body 81 passes through the first positioning plate 82 and the protrusion 831. This arrangement enables the first positioning plate 82 and the second positioning plate 83 to share a hinge shaft.

[0038] The arrangement of the prism mounting assembly 8 facilitates the installation of prisms with different inclinations. After removing the prism mounting assembly 8 , the cubic prism can be directly placed on the mounting plate 7 .

[0039] As another embodiment of the present invention: a flatness measurement area 71 is provided on the mounting plate 7, the flatness measurement area 71 is circular, the box body 81 is located in the flatness measurement area 71, and the lifting and fine-tuning components 6 are distributed outside the flatness measurement area 71. This structural design is conducive to improving the calibration accuracy of the prism.

[0040] As another embodiment of the present invention, the laser interferometer mechanism 1 includes a support plate 11 and a laser interferometer module 12, and the laser interferometer module 12 is mounted on the support plate 11 through a first fine-tuning component. The laser interferometer module 12 realizes fine-tuning positioning with multiple degrees of freedom through the first fine-tuning component.

[0041] As another embodiment of the present invention: the beam splitter module 2 is installed on the support plate 11 through the second fine-tuning component 500. The beam splitter module 2 can achieve fine-tuning positioning with multiple degrees of freedom through the second fine-tuning component 500.

[0042] As another embodiment of the present invention: the support plate 11 is provided with a visual module 9 , and the visual module 9 is located on one side of the spectroscope module 2 .

[0043] As another embodiment of the present invention: a laser beam positioning plate is further provided between the beam splitter module 2 and the standard flat crystal 3 , and a light through hole 100 is provided on the laser beam positioning plate.

[0044] As another embodiment of the present invention: two supporting connecting plates 200 are provided between the laser beam positioning plate and the third fine-tuning component 5 , and the light-through hole 100 and the standard flat crystal 3 are provided between the two supporting connecting plates 200 .

[0045] As another embodiment of the present invention: a mounting platform 300 is provided at the lower end of the lifting fine-tuning assembly 6, two supporting arc plates 400 are provided between the mounting platform 300 and the third fine-tuning assembly 5, and the prism 4 to be calibrated is provided between the two supporting arc plates 400. Specifically, a shielding plate is detachably connected between the two supporting arc plates 400, and the provision of the shielding plate can effectively avoid large measurement errors caused by air disturbance.

[0046] The present invention also provides a prism flatness calibration method based on laser interferometer, comprising the prism flatness calibration device based on laser interferometer as described above, and further comprising the following steps:

[0047] S1: Place the prism 4 to be calibrated on the prism mounting assembly 8, so that the working surface of the prism 4 to be calibrated faces upward and is perpendicular to the horizontal plane; turn on the laser interferometer module 12, and perform laser preheating until the laser interferometer is in normal working state; place the standard flat crystal 3 in the mounting groove of the third fine-tuning assembly 5 and lock it. The area of ​​the working surface of the prism 4 to be calibrated is not greater than the area of ​​the working surface of the standard flat crystal 3.

[0048] S2: Refer to the attached Figure 5 , adjust the lifting and fine-tuning component 6 located at the top angle of the isosceles triangle (adjust the lifting and fine-tuning component f), observe the display window of the visual module 9, roughly adjust the clarity of the laser interference fringes and reach the inflection point; when adjusting, the clarity of the laser interference fringes becomes clearer and clearer, and when adjusting again, the clarity of the laser interference fringes begins to decrease and become blurred, and the turning point from clear to blurred is the inflection point.

[0049] S3: adjusting the laser interferometer module 12 and the first fine-tuning component, observing the display window of the visual module 9, so that the light intensity reaches the optimal state, thereby making the intensity contrast of the laser interference fringes reach the optimal state;

[0050] S4: Adjust the lifting and fine-tuning component 6 located on the bottom side of the isosceles triangle (adjust the lifting and fine-tuning component d or e), observe the display window of the visual module 9, fine-tune the clarity of the laser interference fringes and reach a better inflection point, so that the number of laser interference fringes is not more than 3 (the fewer the better);

[0051] The present invention adjusts the clarity of the laser interference fringe in two steps. First, the base of the isosceles triangle is used as the rotation axis and b is used as the radius to roughly adjust the clarity of the laser interference fringe, which has a strong adjustment ability; then the waist of the isosceles triangle is used as the rotation axis and a is used as the radius to finely adjust the clarity of the laser interference fringe, which has a weak adjustment ability. This structural design is conducive to improving the adjustment efficiency of the clarity of the laser interference fringe. After the rough adjustment of the clarity of the laser interference fringe, the light intensity adjustment step is inserted to improve the intensity contrast of the laser interference fringe, so as to facilitate fine adjustment. This design further improves the adjustment efficiency.

[0052] For details, please refer to the attached Figure 5 , with the lifting and fine-tuning components d, e and f as vertices, a non-equilateral isosceles triangle is formed. The length of the side formed by the line connecting vertex d and vertex e in the triangle is smaller than the other two sides. According to the principle of geometry, Figure 5 As shown, the height length a of the triangle with d as the vertex is less than the height length b of the triangle with f as the vertex. When the installation plate 7 is fine-tuned by using the lifting and fine-tuning component f, the line connecting d and e is used as the rotation axis, and the adjustment range is positively correlated with the height length of the triangle with f as the vertex. When the installation plate 7 is fine-tuned by using the lifting and fine-tuning component d or the lifting and fine-tuning component e, the line connecting e and f is used as the rotation axis (if the lifting and fine-tuning component e is used to lift the installation plate 7, the line connecting d and f is used as the rotation axis), and the adjustment range is positively correlated with the height length of the triangle with d as the vertex. Since the length a is less than the length b, the adjustment ability of the lifting and fine-tuning component 6f is stronger than that of the lifting and fine-tuning component 6d or the lifting and fine-tuning component 6e. During the calibration process, the mounting plate 7 is first quickly fine-tuned using the lifting and fine-tuning assembly f to make it parallel to the standard flat crystal 3. Specifically, during the adjustment process, the laser interference fringes are observed through the display window of the visual module 9 and the inflection point of the laser interference fringes clarity is locked. Then, the lifting and fine-tuning assembly d or e is further used to perform precise fine-tuning on the mounting plate 7 and lock the inflection point with better laser interference fringes clarity.

[0053] S5: Read the flatness of the working surface of the prism 4 to be calibrated for the first time, the reading is x1nm;

[0054] S6: adjusting the standard flat crystal 3 through the third fine-tuning component 5 and observing the display window of the visual module 9 so that the laser interference fringes gradually increase and then gradually decrease to a minimum;

[0055] S7: Read the flatness of the working surface of the prism 4 to be calibrated for the second time, and the reading is x2nm;

[0056] S8: repeat steps S5 and S6, and read the flatness of the working surface of the prism 4 to be calibrated for the third time, and the reading is x3nm;

[0057] S9: The flatness of the working surface of the prism 4 to be calibrated is: [(x1+x2+x3) / 3] nm, and the calibration is completed.

[0058] Among them, in step S1, the specific process of making the working surface of the prism 4 to be calibrated face upward and perpendicular to the horizontal plane is: according to the structural size of the prism 4 to be calibrated, the first positioning plate 82 and the second positioning plate 83 are rotated to a suitable angle and the positioning ball 84 is inserted into the adjustment hole 811 of the box body 81 for fixation; then the prism 4 to be calibrated is placed between the first positioning plate 82 and the second positioning plate 83 and their positions are adjusted so that the working surface of the prism 4 to be calibrated faces upward and perpendicular to the horizontal plane.

[0059] When it is necessary to measure the flatness of the working surface of the cubic prism, first remove the prism mounting assembly 8 and the prism 4 to be calibrated, then place the cubic prism with the working surface facing upward in the middle position of the mounting plate 7, and finally perform calibration according to steps S2-S9.

[0060] The present invention achieves the following beneficial effects:

[0061] (1) Based on the consideration of metrological characteristics, the present invention adopts a high-precision standard flat crystal 3 and a laser interferometer as the main standard device, which greatly improves the measurement accuracy. The calibration accuracy of the present invention can reach λ / 20 (λ is the wavelength of the visible light band of the helium-neon laser, wavelength ≈ 632.8nm), which meets the demand for prism as a metrological standard value traceability.

[0062] (2) The flatness of the working surface of the prism 4 to be calibrated of the present invention can be traced back to the standard flat crystal 3 and the laser interferometer module 12, which effectively ensures the traceability of its value and the traceability integrity of the calibration method.

[0063] (3) The present invention is provided with a prism mounting assembly adapted to prisms of different angles, and can be used for calibrating the flatness of the working surface of right-angle prisms, prisms of other angles, and cubic prisms;

[0064] (4) When prisms with different precision and working surface areas need to be measured, only the standard flat crystal 3 with the corresponding precision and working surface area needs to be equipped, thereby fundamentally ensuring the applicability and extensibility of the calibration device and calibration method of the present invention;

[0065] (5) The main standard of the calibration device and calibration method of the present invention adopts the standard flat crystal 3 and the laser interferometer module 12, so that the comprehensive parameters of the working surface of the prism 4 to be calibrated can be quickly acquired digitally, further ensuring the measurement accuracy of the flatness of the prism working surface and the precision of the traceability of the measurement value.

[0066] (6) The laser interference fringe clarity adjustment is divided into coarse adjustment and fine adjustment. The coarse adjustment has a strong adjustment capability, while the fine adjustment has a weak adjustment capability. This can quickly improve the laser interference fringe clarity. In addition, light intensity adjustment is added between coarse adjustment and fine adjustment, which further speeds up the adjustment speed.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A prism flatness calibration device based on laser interferometer, characterized in that: It comprises a laser interferometer mechanism, below which are arranged a beam splitter module, a standard flat crystal and a prism to be calibrated in sequence, the standard flat crystal being connected to a third fine-tuning component, the lower end of the prism to be calibrated being provided with three lifting fine-tuning components, the lifting fine-tuning components being used to adjust the horizontality of the prism to be calibrated, the three lifting fine-tuning components being distributed in an isosceles triangle, the distance from a lifting fine-tuning component located at the vertex angle of the isosceles triangle to the base of the isosceles triangle being bmm, the distance from a lifting fine-tuning component located at the base angle of the isosceles triangle to the waist of the isosceles triangle being amm, wherein b>a.

2. The prism flatness calibration device based on laser interferometer according to claim 1, characterized in that: The prism to be calibrated is mounted on a mounting plate via a prism mounting assembly, and the lifting and fine-tuning assembly is arranged below the mounting plate.

3. The prism flatness calibration device based on laser interferometer according to claim 2, characterized in that: The prism mounting assembly comprises a box body, in which a first positioning plate and a second positioning plate are hinged, and the first positioning plate and the second positioning plate are distributed in a V shape.

4. The prism flatness calibration device based on laser interferometer according to claim 3, characterized in that: The first positioning plate and the second positioning plate are both provided with positioning balls, the positioning balls are connected with springs, and the box body is provided with adjustment holes matched with the positioning balls.

5. The prism flatness calibration device based on laser interferometer according to claim 4, characterized in that: The hinged end of the first positioning plate is provided with a first groove, the hinged end of the second positioning plate is provided with a protrusion matched with the first groove, and the hinge shaft fixed on the box body passes through the first positioning plate and the protrusion.

6. The prism flatness calibration device based on laser interferometer according to claim 5, characterized in that: The mounting plate is provided with a flatness measurement area, the flatness measurement area is circular, the box body is located in the flatness measurement area, and the lifting and fine-tuning components are distributed outside the flatness measurement area.

7. The prism flatness calibration device based on laser interferometer according to claim 1, characterized in that: The laser interferometer mechanism comprises a support plate and a laser interferometer module, and the laser interferometer module is mounted on the support plate through a first fine-tuning component.

8. The prism flatness calibration device based on laser interferometer according to claim 7, characterized in that: The support plate is provided with a visual module, and the visual module is located on one side of the spectroscope module.

9. A prism flatness calibration method based on laser interferometer, characterized in that: The prism flatness calibration device based on laser interferometer according to any one of claims 1 to 8 further comprises the following steps: S1: Place the standard flat crystal and the prism to be calibrated, so that the working surface of the prism to be calibrated faces upward and is perpendicular to the horizontal plane; S2: Adjust the lifting and fine-tuning components located at the top corner of the isosceles triangle, observe the display window of the visual module, and roughly adjust the clarity of the laser interference fringes to reach the inflection point; S3: adjusting the laser interferometer module and the first fine-tuning component, observing the display window of the visual module, and adjusting the light intensity so that the intensity contrast of the laser interference fringes is optimal; S4: Adjust the lifting and fine-tuning component located on the bottom side of the isosceles triangle, observe the display window of the visual module, fine-tune the clarity of the laser interference fringes and reach a better inflection point, so that the number of laser interference fringes is no more than 3; S5: Read the flatness of the working surface of the prism to be calibrated for the first time, the reading is x1nm; S6: Adjust the standard flat crystal through the third fine-tuning component and observe the display window of the visual module so that the laser interference fringes gradually increase and then gradually decrease to a minimum; S7: Read the flatness of the working surface of the prism to be calibrated for the second time, and the reading is x2nm; S8: repeat steps S5 and S6, and read the flatness of the working surface of the prism to be calibrated for the third time, and the reading is x3nm; S9: The flatness of the working surface of the prism to be calibrated is: [(x1+x2+x3) / 3]nm, and the calibration is completed.

10. The prism flatness calibration method based on laser interferometer according to claim 9, characterized in that: In step S1, the specific process of making the working surface of the prism to be calibrated face upward and perpendicular to the horizontal plane is: according to the structural size of the prism to be calibrated, the first positioning plate and the second positioning plate are rotated to a suitable angle and the positioning ball is inserted into the adjustment hole of the box body; then the prism to be calibrated is placed between the first positioning plate and the second positioning plate and their positions are adjusted so that the working surface of the prism to be calibrated faces upward and perpendicular to the horizontal plane.

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