A precision assembling method for split type Sagnac interferometer

Abstract

The application discloses a kind of precision assembly methods for split Sagnac interferometer, solve the problem of low precision of existing split Sagnac interferometer assembly, specifically includes: the present application ingeniously uses the light of theodolite A exit as the assembly reference light, first positioning assembly to beam splitter prism;Then use assembly reference light and beam splitter prism to positioning assembly to short arm mirror, finally again use assembly reference light, beam splitter prism and short arm mirror positioning assembly to long arm mirror, this assembly method is well-ordered, easy to operate, not only greatly improve the assembly efficiency, also greatly improve the assembly precision, can efficiently assemble the split Sagnac interferometer satisfying the precision requirement.

Description

Technical Field

[0001] This invention relates to a split-type Sagnac interferometer, and more specifically to a precision assembly and adjustment method for a split-type Sagnac interferometer. Background Technology

[0002] Interferometric imaging spectrometers are currently mainly classified into two categories: time-modulated types based on Michelson interferometers and spatial-modulated types based on transverse shearing interferometers. Spatial-modulated interferometric imaging spectrometers have advantages such as high stability, high throughput, and the ability to perform real-time spectral measurements, and have received more attention and application. In spatial-modulated interferometric imaging spectrometers, the transverse shearing interferometer is its core component. Common transverse shearing interferometers include the Sagnac type, Mach-Zehnder type, and bicornuate reflector type. Among them, the Sagnac type transverse shearing interferometer employs a triangular common optical path structure, is less affected by external vibrations and airflow, has strong anti-interference capabilities, and is the most widely used.

[0003] Sagnac interferometers are divided into solid Sagnac interferometers and split-type Sagnac interferometers. Solid Sagnac interferometers are composed of two identical half-pentagonal prisms glued together. They have a compact structure, stable performance, and are less affected by external interference. However, solid Sagnac interferometers require high glued precision, are difficult to assemble, and have a low success rate. Furthermore, as the resolution of imaging spectrometers continues to improve, the size of the interferometers is constantly increasing, making the manufacturing of large-aperture solid interferometers even more difficult. Split-type Sagnac interferometers are simpler to manufacture, as they do not require the gluing of two half-pentagonal prisms, and have been more widely used. However, due to the increased number of components in split-type Sagnac interferometers, and the extremely strict requirements for the spatial consistency of each component, precise assembly and adjustment of split-type Sagnac interferometers is quite difficult. Existing assembly and adjustment methods cannot achieve high-precision assembly and adjustment of split-type Sagnac interferometers. Summary of the Invention

[0004] The purpose of this invention is to provide a precision assembly and adjustment method for a split-type Sagnac interferometer, so as to solve the technical problem of low assembly and adjustment accuracy of existing split-type Sagnac interferometers.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A precision assembly and adjustment method for a split-type Sagnac interferometer, the split-type Sagnac interferometer comprising an interferometer body, a beam splitter prism, a short-arm mirror, and a long-arm mirror; the outer contour of the sidewall of the interferometer body is pentagonal, wherein two sides are perpendicular to each other, defined as the first right-angle side and the second right-angle side, the side adjacent to the first right-angle side is the first adjacent side, and the side adjacent to the second right-angle side is the second adjacent side; the bottom of the interferometer body is provided with a beam splitter prism mounting position, the sidewall corresponding to the first adjacent side is provided with a short-arm mirror mounting position, and the sidewall corresponding to the second adjacent side is provided with a long-arm mirror mounting position;

[0007] Its special feature is that it includes the following steps:

[0008] Step 1: Establish and adjust the reference light;

[0009] The interferometer body is set on an assembly platform level with the ground. Reticle B and reticle A are respectively installed at the short-arm and long-arm mirror mounting positions on the interferometer body. Theodolite B and theodolite A are set outside the assembly platform. An assembly reference light is established through reticle B, reticle A, theodolite B, and theodolite A. The assembly reference light is the output light of theodolite A.

[0010] Step 2: Positioning and assembling the beam splitter;

[0011] Install the beam splitter prism at the beam splitter mounting position on the interferometer body; move the theodolite B to the outside of the first adjacent side of the interferometer body and level it; based on the installation reference light, the reflection of the installation reference light by the beam splitter prism, the outgoing light of the theodolite B, the reticle B, and the trimming of the beam splitter prism trimming ring, complete the positioning and installation of the beam splitter prism.

[0012] Step 3: Positioning and adjusting the short-arm reflector;

[0013] Remove reticle B and reticle A, install the short-arm reflector at the short-arm reflector mounting position on the interferometer body, move the theodolite B to the outside of the second adjacent side of the interferometer body and level it, and complete the positioning and adjustment of the short-arm reflector based on the aforementioned installation reference light, the outgoing light of the theodolite B, the reflection of light by the beam splitter prism, the reflection of light by the short-arm reflector, and the trimming of the trimming ring of the short-arm reflector.

[0014] Step 4: Positioning and adjusting the long-arm reflector;

[0015] Install the long-arm reflector at the long-arm reflector mounting position on the interferometer body, move the theodolite B to the outside of the second right-angle side of the interferometer body and level it, and complete the positioning and adjustment of the long-arm reflector based on the installation reference light, the outgoing light of the theodolite B, the transmission of light by the beam splitter prism, the reflection of light by the short-arm reflector, the reflection of light by the long-arm reflector, and the trimming of the trimming ring of the long-arm reflector.

[0016] This allows for the precise assembly and adjustment of the split-type Sagnac interferometer.

[0017] Furthermore, step 1 specifically includes:

[0018] 1.1 Set up an assembly and adjustment platform so that the angle between it and the horizontal ground is less than 1″;

[0019] 1.2 Install the interferometer body to be assembled and adjusted on the assembly and adjustment platform;

[0020] 1.3. A reticle B is installed at the short-arm mirror mounting position of the interferometer body, and a reticle A is installed at the long-arm mirror mounting position; a theodolite B and a theodolite A are installed outside the assembly and adjustment platform, wherein the working end of the theodolite B is opposite to the reticle B, and the working end of the theodolite A is opposite to the first right-angle side.

[0021] 1.4. Level the theodolite B and the theodolite A, and make them mutually aligned. Then, make the theodolite B aligned with the reticle B, and make the theodolite A aligned with the reticle A and self-aligned with the theodolite B. The light emitted from the theodolite A will then be the reference light for the setup.

[0022] Furthermore, step 1.1 specifically includes:

[0023] A. Place the assembly and adjustment platform on three support frames arranged in a triangle;

[0024] B. Use an electronic level to measure the angle between the assembly platform and the ground.

[0025] C. Adjust the three support frames based on the measured angles so that the angle between the assembly platform and the horizontal ground is less than 1″.

[0026] Furthermore, in step A, the flatness of the assembly platform is less than 0.01 mm;

[0027] In step B, the accuracy of the electronic level is 0.001″.

[0028] Furthermore, step 1.3 specifically includes:

[0029] A reticle B is installed at the short-arm mirror mounting position of the interferometer body, and a reticle A is installed at the long-arm mirror mounting position. Two two-dimensional adjustment platforms are set outside the assembly and adjustment platform, and theodolite B and theodolite A are installed on the two two-dimensional adjustment platforms respectively, so that the working end of theodolite B is opposite to the reticle B, and the working end of theodolite A is opposite to the first right-angle side.

[0030] Further, step 1.2 specifically involves using a pressure plate to mount the interferometer body to be assembled and adjusted onto the assembly and adjustment platform;

[0031] In step 1.3, both theodolite B and theodolite A are TM6100A Leica theodolites with an autocollimation accuracy of 0.5″.

[0032] Furthermore, step 2 specifically includes:

[0033] 2.1 Install a beam splitter at the beam splitter mounting position on the interferometer body; the beam splitter is rectangular and is formed by gluing together a first right-angled triangular prism and a second right-angled triangular prism; the first right-angled triangular prism includes a first vertical surface and a second vertical surface that are perpendicular to each other; the first vertical surface is positioned close to the first right-angle side, the adjustment reference light is incident through the first vertical surface, reflected by the beam splitter, and then emitted from the second vertical surface, and then emitted from the reticle B;

[0034] 2.2 Adjust the angle of the theodolite B so that the theodolite B is aligned with the reticle B and simultaneously self-aligned with the theodolite A, and the angle between the theodolite A and the theodolite B is 90°.

[0035] 2.3. Measure the first pitch angle of the first vertical plane of the beam splitter at point A of the theodolite, and measure the second pitch angle of the second vertical plane of the beam splitter at point B of the theodolite.

[0036] 2.4. Trim the trimming ring of the beam splitter according to the measured first and second pitch angles until the difference between the first and second pitch angles and the ground level is within 5″.

[0037] 2.5 Fine-tune the beam splitter so that the autocollimation images of the first and second vertical planes coincide with the crosshairs of the theodolite A and the theodolite B, respectively. Then the beam splitter will match the reference light for installation and adjustment, and the positioning and installation of the beam splitter will be completed.

[0038] Furthermore, step 3 specifically includes:

[0039] 3.1 Remove reticle B and reticle A, and install the short-arm mirror on the short-arm mirror mounting position on the interferometer body;

[0040] 3.2 Move the theodolite B so that its active end is aligned with the mounting position of the long arm reflector on the interferometer body, level it, and simultaneously ensure that it meets the following conditions:

[0041] a1. Ensure that the reference light emitted from the theodolite A can be reflected sequentially by the beam splitter prism and the short-arm mirror before entering the theodolite B.

[0042] b1. Theodolite B can aim at theodolite A, and the sum of the angles of their rotation when aiming at each other is 45°.

[0043] 3.3 Trim the trimming ring of the short-arm reflector so that the reference light emitted from the theodolite A can coincide with the crosshair center of the theodolite B, with an overlap accuracy of less than or equal to 5″.

[0044] Complete the positioning and adjustment of the short-arm reflector.

[0045] Furthermore, step 4 specifically includes:

[0046] 4.1 Install the long-arm reflector at the long-arm reflector mounting position on the interferometer body;

[0047] 4.2 Move the theodolite B so that its active end is aligned with the second right-angle side of the interferometer body and the beam splitter, level it, and simultaneously satisfy the following conditions:

[0048] a2. Ensure that the reference light emitted from the theodolite A can be transmitted through the beam splitter prism, reflected by the long arm mirror, reflected by the short arm mirror, and transmitted through the beam splitter prism before entering the theodolite B.

[0049] b2. Enable the theodolite B to aim at the theodolite A, and ensure that the sum of their rotation angles is 90° when aiming at each other.

[0050] 4.3 Trim the trimming ring of the long-arm reflector so that the light received by theodolite A and theodolite B can coincide with the cross centers of the two instruments, with an overlap accuracy of less than or equal to 5″.

[0051] Complete the positioning and adjustment of the long-arm reflector.

[0052] Furthermore, it also includes step 5, verifying the positioning and adjustment results:

[0053] 5.1 Replace the theodolite A with a camera and the theodolite B with a laser. Set up a homogenizer and tracing paper in the optical path between the laser and the interferometer body. The focal length of the camera is f = 75.03 mm and the pixel size of the camera is P = 5 μm. The wavelength of the laser is λ = 632.8 nm.

[0054] 5.2. Acquire images of the assembled and adjusted split-type Sagnac interferometer using a camera, obtain the number of peaks n of the corresponding frequency curves, and calculate the actual shear quantity D:

[0055]

[0056] 5.3 Compare the actual shearing amount D with the theoretical shearing range:

[0057] If the actual shearing amount D is greater than the maximum value of the theoretical shearing range, return to step 4.3 and trim the trimming ring of the long arm mirror again. The trimming amount d1 = 4ΔD1sin22.5°, where ΔD1 is the difference between the actual shearing amount D and the maximum value of the theoretical shearing range; until the actual shearing amount D is within the theoretical shearing range.

[0058] If the actual shearing amount D is less than the minimum value of the theoretical shearing range, return to step 3.3 and trim the trimming ring of the short-arm reflector again. The trimming amount d2 = 4ΔD2sin22.5°, where ΔD2 is the difference between the actual shearing amount D and the minimum value of the theoretical shearing range; until the actual shearing amount D is within the theoretical shearing range.

[0059] If the actual shearing amount D is within the theoretical shearing range, then the precision assembly and adjustment results of the split-type Sagnac interferometer are qualified.

[0060] The beneficial effects of this invention are:

[0061] This invention provides a precision assembly and adjustment method for a split-type Sagnac interferometer. This method cleverly utilizes the light emitted from the theodolite A as the assembly reference light. First, the beam splitter is positioned and adjusted. Then, the assembly reference light and the beam splitter are used together to position and adjust the short-arm mirror. Finally, the assembly reference light, the beam splitter, and the short-arm mirror are used together to position and adjust the long-arm mirror. This assembly and adjustment method is orderly and easy to operate, greatly improving both assembly efficiency and assembly accuracy. It can efficiently assemble a split-type Sagnac interferometer that meets accuracy requirements. Attached Figure Description

[0062] Figure 1 This is a state diagram corresponding to step 1 in the precision assembly and adjustment method for a split-type Sagnac interferometer according to an embodiment of the present invention;

[0063] Figure 2 This is a state diagram corresponding to step 2 in the precision assembly and adjustment method for a split-type Sagnac interferometer according to an embodiment of the present invention;

[0064] Figure 3 This is a state diagram corresponding to step 3 in the precision assembly and adjustment method for a split-type Sagnac interferometer according to an embodiment of the present invention;

[0065] Figure 4 This is a state diagram corresponding to step 4 in the precision assembly and adjustment method for a split-type Sagnac interferometer according to an embodiment of the present invention;

[0066] Figure 5 This is a schematic diagram showing the positional structure of the beam splitter prism, the short-arm reflector, and the long-arm reflector in an embodiment of the present invention.

[0067] Icon labels:

[0068] 1-Interferometer body, 11-First right-angled side, 12-Second right-angled side, 13-First adjacent side, 14-Second adjacent side, 2-Beam splitter prism, 21-First right-angled triangular prism, 211-First vertical plane, 212-Second vertical plane, 22-Second right-angled triangular prism, 3-Short-arm reflector, 4-Long-arm reflector, 5-Adjustment platform, 6-Reticle B, 7-Reticle A, 8-Theodolite B, 9-Theodolite A. Detailed Implementation

[0069] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] Combination Figures 1-4 As shown, the split-type Sagnac interferometer includes an interferometer body 1, a beam splitter prism 2, a short-arm mirror 3, and a long-arm mirror 4. The outer contour of the sidewall of the interferometer body 1 is pentagonal, with two sides perpendicular to each other, defined as the first right-angled side 11 and the second right-angled side 12. The side adjacent to the first right-angled side 11 is the first adjacent side 13, and the side adjacent to the second right-angled side 12 is the second adjacent side 14. The bottom of the interferometer body 1 has a beam splitter mounting position, and the sidewall corresponding to the first adjacent side 13 has a short-arm mirror mounting position, and the sidewall corresponding to the second adjacent side 14 has a long-arm mirror mounting position. Glass pads are bonded to the upper and lower non-light-transmitting surfaces of the beam splitter 2, and one of the glass pads is bonded to a metal base to form a beam splitter prism assembly.

[0071] This invention provides a precision assembly and adjustment method for a split-type Sagnac interferometer, comprising the following steps:

[0072] Step 1, as follows Figure 1 As shown, establish and adjust the reference light.

[0073] 1.1 Set up the installation and adjustment platform 5, ensuring that its angle with the horizontal is less than 1″; specifically including:

[0074] A. Place an assembly and adjustment platform 5 with a flatness of less than 0.01 mm on three support frames arranged in a triangle.

[0075] B. Use an electronic level with an accuracy of 0.001″ to measure the angle between the mounting platform 5 and the earth in the X and Y directions.

[0076] C. Adjust the three support frames based on the measured angles so that the angle between the assembly platform 5 and the horizontal ground in both the X and Y directions is less than 1″.

[0077] 1.2 Use the pressure plate to press the interferometer body 1 to be assembled and adjusted onto the assembly and adjustment platform 5. Be careful not to press it too tightly to prevent deformation of the interferometer body 1; also, do not press it too loosely to prevent assembly and adjustment errors caused by loosening of the interferometer body 1 during the debugging process.

[0078] 1.3. A reticle B6 is installed on the short-arm mirror mounting position of the interferometer body 1, and a reticle A7 is installed on the long-arm mirror mounting position. To ensure the stability of the instrument, two two-dimensional adjustment platforms are set outside the assembly and adjustment platform 5. A TM6100A Leica theodolite B8 and a theodolite A9 with an autocollimation accuracy of 0.5″ are respectively installed on the two two-dimensional adjustment platforms, so that the working end of the theodolite B8 is opposite to the reticle B6, and the working end of the theodolite A9 is opposite to the first right-angle side 11.

[0079] 1.4 Level the theodolite B8 and the theodolite A9, and make them mutually aligned. Then, make the theodolite B8 self-align with the reticle B6, and make the theodolite A9 self-align with the reticle A7 and the theodolite B. The light emitted by theodolite A9 will then be the reference light for the setup. Theodolite A9 must not be moved during the entire setup process.

[0080] Step 2, as follows Figure 3 As shown, the positioning and assembly of the beam splitter 2.

[0081] 2.1 Install the beam splitter 2 on the beam splitter mounting position of the interferometer body 1, and tighten all 12 screws to torque; the beam splitter 2 is rectangular and is made of a first right-angled triangular prism 21 and a second right-angled triangular prism 22 glued together; the first right-angled triangular prism 21 includes a first vertical surface 211 and a second vertical surface 212 that are perpendicular to each other; the first vertical surface 211 is set close to the first right-angle side 11, so the adjustment reference light is incident through the first vertical surface 211, reflected by the beam splitter prism 2, and then emitted from the second vertical surface 212, and then emitted from the reticle B 6.

[0082] 2.2 Adjust the angle of the theodolite B8 so that the theodolite B8 is aligned with the center of the reticle B6 for height determination, and simultaneously autoalign with the theodolite A9, and make the angle between the theodolite A9 and the theodolite B8 90°.

[0083] 2.3. Measure the first pitch angle of the first vertical plane 211 of the beam splitter 2 at point A9 of the theodolite, and measure the second pitch angle of the second vertical plane 212 of the beam splitter 2 at point B8 of the theodolite.

[0084] 2.4. Based on the measured first and second pitch angles, trim the trimming ring of the beam splitter 2 until the difference between the first and second pitch angles and the horizontal ground level is within 5″.

[0085] 2.5 Fine-tune the beam splitter 2 so that the autocollimation images of the first vertical plane 211 and the second vertical plane 212 coincide with the crosshairs of the theodolite A9 and the theodolite B8, respectively. Then the beam splitter 2 matches the reference light for installation and adjustment, and the positioning and installation of the beam splitter 2 is completed.

[0086] Step 3, as follows Figure 3 As shown, the positioning and adjustment of the short-arm reflector 3.

[0087] 3.1 Remove reticle B6 and reticle A7, and install the short-arm mirror 3 on the short-arm mirror mounting position of the interferometer body 1.

[0088] 3.2 Move the theodolite B8 so that its active end is aligned with the mounting position of the long-arm reflector of the interferometer body 1, level it, and simultaneously ensure that it meets the following conditions:

[0089] a1. Ensure that the reference light emitted from the theodolite A9 is reflected sequentially by the beam splitter prism 2 and the short-arm mirror 3 before entering the theodolite B8;

[0090] b1. Theodolite B8 can be mutually aimed at theodolite A9, and the sum of the rotation angles of the two instruments during mutual aiming is 45°;

[0091] 3.3 Trim the trimming ring of the short-arm reflector 3 so that the reference light emitted from the theodolite A9 can coincide with the crosshair center of the theodolite B8, with an overlap accuracy of less than or equal to 5″.

[0092] Complete the positioning and adjustment of the short-arm reflector 3.

[0093] Step 4, as follows Figure 4 As shown, the positioning and adjustment of the long-arm reflector 4.

[0094] 4.1 Install the long-arm reflector 4 at the long-arm reflector mounting position on the interferometer body 1.

[0095] 4.2 Move the theodolite B8 so that its working end is aligned with the second right-angle side of the interferometer body 1 and the beam splitter 2, level it, and simultaneously satisfy the following conditions:

[0096] a2. Ensure that the reference light emitted from the theodolite A9 can be transmitted through beam splitter prism 2, reflected by long-arm mirror 4, reflected by short-arm mirror 3, and transmitted through beam splitter prism 2 before entering the theodolite B8.

[0097] b2. Enable the theodolite B8 to align with the theodolite A9, and ensure that the sum of their rotation angles during aligning is 90°.

[0098] 4.3 Trim the trimming ring of the long-arm reflector 4 so that the light received by the theodolite A 9 and the theodolite B 8 can coincide with the cross centers of the two instruments, with an overlap accuracy of less than or equal to 5″.

[0099] After completing the positioning and adjustment of the long-arm reflector 4, the positional relationship of the beam splitter 2, the short-arm reflector 3, and the long-arm reflector 4 is as follows: Figure 5 As shown.

[0100] Step 5: Inspect the positioning and adjustment results;

[0101] 5.1 Replace the theodolite A9 with a camera (focal length f = 75.03 mm, pixel size P = 5 μm) and replace the theodolite B8 with a laser (wavelength λ = 632.8 nm). Add a homogenizer and tracing paper to the optical path between the laser and the interferometer body 1. At this time, the homogenizer and tracing paper have no order.

[0102] 5.2 Use a camera to acquire images of the positioned and adjusted split-type Sagnac interferometer, obtain the number of peaks n of the corresponding frequency curves in the acquired images, and calculate the number of pixels N:

[0103]

[0104] Then calculate the actual shear amount D:

[0105]

[0106] In the formula, x is the spacing between the black and white stripes in the acquired image, x = PN;

[0107] but:

[0108]

[0109] 5.3 The theoretical shearing range of the split-type Sagnac interferometer used in the operation is 0.959~0.988mm. If the actual shearing amount D is greater than the maximum value of the theoretical shearing range, return to step 4.3 and trim the trimming ring of the long-arm reflector 4 again. The trimming amount d1=4ΔD1sin22.5°, where ΔD1 is the difference between the actual shearing amount D and the maximum value of the theoretical shearing range; until the actual shearing amount D is within the theoretical shearing range; the trimming result must simultaneously meet the requirements of shearing amount and the theodolite center penetration.

[0110] If the actual shearing amount D is less than the minimum value of the theoretical shearing range, return to step 3.3 and trim the trimming ring of the short-arm reflector 3 again. The trimming amount d2 = 4ΔD2sin22.5°, where ΔD2 is the difference between the actual shearing amount D and the minimum value of the theoretical shearing range. The trimming result must meet the requirements of both shearing amount and the theodolite core until the actual shearing amount D is within the theoretical shearing range.

[0111] If the actual shearing amount D is within the theoretical shearing range, then the precision assembly and adjustment results of the split-type Sagnac interferometer are qualified.

[0112] The method described in this embodiment solves the problems of high assembly difficulty, low efficiency, and low accuracy of the split-type Sagnac interferometer, and achieves high-precision assembly of the split-type Sagnac interferometer.

[0113] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A precision assembly method for a split Sagnac interferometer, the split Sagnac interferometer comprising an interferometer body (1), a beam splitter prism (2), a short arm mirror (3) and a long arm mirror (4); the outer profile of the side wall of the interferometer body (1) is pentagonal, two of which are perpendicular to each other, defined as a first right angle side (11) and a second right angle side (12), the side adjacent to the first right angle side (11) is a first adjacent side (13), and the side adjacent to the second right angle side (12) is a second adjacent side (14); the bottom of the interferometer body (1) is provided with a beam splitter prism mounting position, the first adjacent side (13) of which is provided with a short arm mirror mounting position on the corresponding side wall, and the second adjacent side (14) of which is provided with a long arm mirror mounting position on the corresponding side wall; characterized in that comprising the following steps: Step 1, establishing an assembly reference light; The assembled interferometer body (1) is arranged on an assembly platform (5) which is horizontal to the ground, a scale plate B (6) and a scale plate A (7) are arranged on the short arm mirror mounting position and the long arm mirror mounting position of the interferometer body (1) respectively, and theodolites B (8) and theodolites A (9) are arranged outside the assembly platform (5); the assembly reference light is established by the scale plate B (6), the scale plate A (7), the theodolites B (8) and the theodolites A (9); the assembly reference light is the outgoing light of the theodolites A (9); Step 2, positioning and assembling the beam splitter prism (2); The beam splitter prism (2) is mounted on the beam splitter prism mounting position of the interferometer body (1); the theodolites B (8) are moved to the outside of the first adjacent side (13) of the interferometer body (1) and leveled, and based on the assembly reference light, the reflection of the assembly reference light by the beam splitter prism (2), the outgoing light of the theodolites B (8), the scale plate B (6) and the trimming of the trimming circle of the beam splitter prism (2), the positioning and assembling of the beam splitter prism (2) are completed; Step 3, positioning and assembling the short arm mirror (3); The scale plate B (6) and the scale plate A (7) are removed, the short arm mirror (3) is mounted on the short arm mirror mounting position of the interferometer body (1), the theodolites B (8) are moved to the outside of the second adjacent side (14) of the interferometer body (1) and leveled, and based on the assembly reference light, the outgoing light of the theodolites B (8), the reflection of the light by the beam splitter prism (2), the reflection of the light by the short arm mirror (3) and the trimming of the trimming circle of the short arm mirror (3), the positioning and assembling of the short arm mirror (3) are completed; Step 4, positioning and assembling the long arm mirror (4); The long arm mirror (4) is mounted on the long arm mirror mounting position of the interferometer body (1), the theodolites B (8) are moved to the outside of the second right angle side (12) of the interferometer body (1) and leveled, and based on the assembly reference light, the outgoing light of the theodolites B (8), the transmission of the light by the beam splitter prism (2), the reflection of the light by the short arm mirror (3), the reflection of the light by the long arm mirror (4) and the trimming of the trimming circle of the long arm mirror (4), the positioning and assembling of the long arm mirror (4) are completed; Thus, the precision assembly of the split Sagnac interferometer is completed.

2. The precision alignment method for split Sagnac interferometer according to claim 1, wherein, Step 1 specifically comprises: 1.1, set the installation and adjustment platform (5) to make its angle with the ground level less than 1"; 1.2, the to-be-adjusted interferometer body (1) is installed on the installation and adjustment platform (5); 1.3, the installation and adjustment platform (5) is provided with a scale plate B (6) at the short arm mirror installation position of the interferometer body (1) and a scale plate A (7) at the long arm mirror installation position; a theodolite B (8) and a theodolite A (9) are arranged outside the installation and adjustment platform (5), the action end of the theodolite B (8) is opposite to the scale plate B (6), and the action end of the theodolite A (9) is opposite to the first right angle side (11); 1.4, the theodolite B (8) and the theodolite A (9) are leveled, and the two are mutually sighted, and then the theodolite B (8) is pierced through the scale plate B (6), and the theodolite A (9) is pierced through the scale plate A (7) and is self-accurate with the theodolite B (8), so that the light emitted by the theodolite A (9) is the installation and adjustment reference light.

3. The precision alignment method for split Sagnac interferometer according to claim 2, wherein, Step 1.1 specifically comprises: A, placing the installation and adjustment platform (5) on three triangularly arranged support frames; B, measuring the angle between the installation and adjustment platform (5) and the ground level by using an electronic level; C, adjusting the three support frames based on the measured angle, so that the angle between the installation and adjustment platform (5) and the ground level is less than 1".

4. The precision installation and adjustment method for a split Sagnac interferometer according to claim 3, characterized in that: In step A, the flatness of the installation and adjustment platform (5) is less than 0.01 mm; In step B, the precision of the electronic level is 0.001".

5. The precision alignment method for split Sagnac interferometer according to claim 4, wherein, Step 1.3 specifically comprises: The installation and adjustment platform (5) is provided with a scale plate B (6) at the short arm mirror installation position of the interferometer body (1) and a scale plate A (7) at the long arm mirror installation position; two two-dimensional adjustment tables are arranged outside the installation and adjustment platform (5), and a theodolite B (8) and a theodolite A (9) are respectively installed on the two two-dimensional adjustment tables, so that the action end of the theodolite B (8) is opposite to the scale plate B (6), and the action end of the theodolite A (9) is opposite to the first right angle side (11).

6. The precision installation and adjustment method for a split Sagnac interferometer according to claim 5, characterized in that: In step 1.2, the to-be-adjusted interferometer body (1) is installed on the installation and adjustment platform (5) by using a pressing plate; In step 1.3, the theodolite B (6) and the theodolite A (9) are both TM6100A Leica theodolites with a self-accuracy of 0.5".

7. The precision alignment method for split Sagnac interferometer according to any one of claims 1-6, wherein, Step 2 specifically comprises: 2.1, installing a beam splitter prism (2) at the beam splitter prism installation position of the interferometer body (1); the beam splitter prism (2) is rectangular and is glued by a first right triangle prism (21) and a second right triangle prism (22); the first right triangle prism (21) comprises a first vertical surface (211) and a second vertical surface (212) perpendicular to each other; the first vertical surface (211) is arranged close to the first right angle side (11), the installation and adjustment reference light is incident through the first vertical surface (211), is reflected by the beam splitter prism (2), is then emitted from the second vertical surface (212), and is then emitted from the scale plate B (6); 2.2, adjust the angle of the theodolite B (8) to make the theodolite B (8) and the scale plate B (6) cross, and at the same time, the theodolite A (9) is perpendicular to the theodolite B (8), and the angle between the theodolite A (9) and the theodolite B (8) is 90°; 2.3, measure the first pitch angle of the first vertical surface (211) of the light splitting prism (2) at the theodolite A (9), and measure the second pitch angle of the second vertical surface (212) of the light splitting prism (2) at the theodolite B (8); 2.4, according to the measured first pitch angle and the second pitch angle, the trimming circle of the light splitting prism (2) is trimmed until the difference between the first pitch angle and the second pitch angle and the ground level is within 5″; 2.5, fine-tune the light splitting prism (2) so that the self-perpendicular images of the first vertical surface (211) and the second vertical surface (212) coincide with the cross center of the theodolite A (9) and the theodolite B (8) respectively, then the light splitting prism (2) is consistent with the installation reference light, and the positioning and installation of the light splitting prism (2) is completed.

8. The precision alignment method for split Sagnac interferometer according to claim 7, wherein, Step 3 specifically includes: 3.1, remove the scale plate B (6) and the scale plate A (7), and install the short arm mirror (3) on the short arm mirror installation position of the interferometer body (1); 3.2, move the theodolite B (8) to make its action end opposite to the long arm mirror installation position of the interferometer body (1), level it and at the same time make it meet the following conditions: a1, the installation reference light emitted by the theodolite A (9) can enter the theodolite B (8) after being reflected by the light splitting prism (2) and the short arm mirror (3) in turn; b1, the theodolite B (8) can mutual sight with the theodolite A (9), and the sum of the rotation angles of the two is 45°; 3.3, trim the trimming circle of the short arm mirror (3) so that the installation reference light emitted by the theodolite A (9) can coincide with the cross center of the theodolite B (8), and the coincidence precision is less than or equal to 5″; complete the positioning and installation of the short arm mirror (3).

9. The precision alignment method for split Sagnac interferometer according to claim 8, wherein, Step 4 specifically includes: 4.1, install the long arm mirror (4) on the long arm mirror installation position of the interferometer body (1); 4.2, move the theodolite B (8) to make its action end opposite to the second straight edge of the interferometer body (1) and the light splitting prism (2), level it and at the same time meet the following conditions: a2, the installation reference light emitted by the theodolite A (9) can enter the theodolite B (8) after being transmitted by the light splitting prism (2), reflected by the long arm mirror (4), reflected by the short arm mirror (3) and transmitted by the light splitting prism (2) in turn; b2, the theodolite B (8) can mutual sight with the theodolite A (9), and the sum of the rotation angles of the two is 90°; 4.3, trim the trimming circle of the long arm mirror (4) so that the light received by the theodolite A (9) and the theodolite B (8) can coincide with the cross center of the two respectively, and the coincidence precision is less than or equal to 5″; complete the positioning and installation of the long arm mirror (4).

10. The precision alignment method for split Sagnac interferometer according to claim 9, wherein, It also includes step 5, verifying the positioning and installation result: 5.1, replace the theodolite A (9) with a camera, replace the theodolite B (8) with a laser, set a homogenizer and sulfuric acid paper on the light path between the laser and the interferometer body (1); the focal length of the camera f = 75.03 mm, the camera pixel size P = 5 μm; the wavelength of the laser λ = 632.8 nm; 5.2, acquire the image of the split type Sagnac interferometer through the camera, obtain the number of wave peaks n of the image corresponding frequency curve, and calculate the actual shear amount D: 5.3, compare the actual shear amount D with the theoretical shear range: If the actual shear amount D is greater than the maximum value of the theoretical shear range, return to step 4.3, and cut the shear circle of the long arm mirror (4) again, the shear amount d1 = 4ΔD1sin22.5°, wherein ΔD1 is the difference between the actual shear amount D and the maximum value of the theoretical shear range; until the actual shear amount D is within the theoretical shear range; If the actual shear amount D is less than the minimum value of the theoretical shear range, return to step 3.3, and cut the shear circle of the short arm mirror (3) again, the shear amount d2 = 4ΔD2sin22.5°, wherein ΔD2 is the difference between the actual shear amount D and the minimum value of the theoretical shear range; until the actual shear amount D is within the theoretical shear range; If the actual shear amount D is within the theoretical shear range, the precision assembly result of the split type Sagnac interferometer is qualified.

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