High-precision autocollimator based on Twyman Green interference principle and angle measurement method

Abstract

The invention provides a high-precision autocollimator based on a Twyman Green interference principle and an angle measurement method, and aims to solve the problem that the existing angle measurement precision cannot be continuously broken through due to the limitation of a geometrical optics principle and the influence of environmental factors in the prior art. The autocollimator comprises a laser, a filtering collimation module, a spectroscope, a reference reflector, a plane reflector, a detector and a data acquisition and processing computer. After the autocollimator is leveled, the plane mirror is placed on a rotary table to be measured, measurement is carried out when the plane mirror does not have a rotation angle and when the plane mirror has a rotation angle, laser is emitted into the filtering collimation module and then is emitted to the spectroscope in the form of monochromatic parallel light and is divided into two paths, and one path is reflected by the plane mirror and then passes through the spectroscope again to reach the detector; the other path is reflected by the reference reflector and then reflected by the spectroscope to the detector; and the two beams of light generate interference on the target surface of the detector, and the detector records an interference image and uploads the interference image to a computer to calculate the offset of interference fringes, thereby completing angle measurement.

Description

Technical Field

[0001] The invention relates to an autocollimator, and in particular to a high-precision autocollimator and an angle measuring method based on the Twyman-Green interference principle. Background Art

[0002] Since the 1990s, with the development of photoelectric detection technology and image processing technology, autocollimators have been further developed in the field of optoelectronics, and the instrument's measurement range, measurement accuracy, measurement speed, and intelligence have been greatly improved. At present, representative photoelectric autocollimators include CSZ-1 of the 6354th Institute of China Shipbuilding Industry Corporation, with an objective lens focal length of 550mm, a light aperture of 50mm, a measurement range of 300″×300″, and a measurement accuracy of ±0.5″; and Auto MAT 5000 of Tianjin Aotemeier Optoelectronic Technology Co., Ltd., with an objective lens focal length of 300mm, a light aperture of 50mm, a measurement range of 1000″×1000″, and a measurement accuracy of ±0.2″. However, it is worth noting that the traditional photoelectric autocollimator is based on the principle of geometric optics, and the measurement principle is the tangent theorem. Its resolution is mainly determined by the focal length of the optical system and the image-side line resolution. The longer the focal length of the optical system, the higher the image-side line resolution of the system, the higher the resolution of the autocollimator, and the higher its measurement accuracy. However, due to the limitation of the aperture of the optical system, its focal length cannot be too long, and the image-side linear resolution is also limited by the size of the photodetector pixels or the magnification of the eyepiece and cannot be further improved. A more complex calibration procedure is required to ensure its accuracy. In addition, the long focal length and large aperture optical system used in pursuit of measurement accuracy is extremely sensitive to environmental conditions. External factors such as temperature changes, airflow disturbances, and vibration of the experimental platform will affect the emission direction and quality of the light beam. The manufacturing accuracy and surface quality of the optical components used in the system, such as lenses and reflectors, also directly affect the measurement accuracy of the autocollimator. Therefore, the traditional autocollimator based on the principle of geometric optics has basically developed to its own bottleneck, and it is urgent to have a breakthrough theoretical method and technical means to improve the angular measurement accuracy of the autocollimator. Summary of the invention

[0003] The main purpose of the present invention is to solve the problem that traditional autocollimators based on geometric optics are limited by the focal length of the optical system, the relative aperture, the pixel size of the electrical detector or the magnification of the eyepiece, especially the long focal length and large aperture optical system is greatly affected by environmental factors, and thus cannot continue to break through the existing angle measurement accuracy. Instead, a high-precision autocollimator and angle measurement method based on the Twyman-Green interference principle are provided.

[0004] The concept of the present invention is:

[0005] Based on the Twyman-Green interference principle, a specific interference pattern is obtained by modulating the reference light, and a specific analysis method is used to solve the posture information of the test beam, that is, the angle information of the test beam. Optical interference, light field modulation, fractional Fourier analysis, numerical analysis and other technologies are comprehensively utilized to achieve real-time, efficient and high-precision self-collimation angle measurement test.

[0006] In order to achieve the above invention objectives and complete the above invention concepts, the present invention provides the following technical solutions:

[0007] A high-precision autocollimator based on the Twyman-Green interferometer principle, which is special in that:

[0008] It includes a laser, a filter collimation module and a beam splitter which are sequentially arranged on the laser output light path, wherein the beam splitter is used to split the filtered and collimated laser into a reflected light and a transmitted light;

[0009] It also includes a reference reflector arranged on the transmission light path of the spectroscope, a plane reflector arranged on the reflection light path of the spectroscope, a detector arranged on the output light path of the spectroscope, and a data acquisition and processing computer connected to the output end of the detector;

[0010] The filtering and collimating module is used to filter and collimate the laser light emitted by the laser to make it a beam of monochromatic parallel light;

[0011] The reference reflector is a convex reflector, used to reflect the transmitted light back to the beam splitter in the form of spherical waves;

[0012] The plane reflector is placed on the rotating table to be measured, and is used to reflect the reflected light back to the beam splitter in the form of a plane wave;

[0013] The plane wave is transmitted through the beam splitter, and the spherical wave is reflected again by the beam splitter, and then emitted from the beam splitter to the detector, where it interferes on the target surface of the detector and generates an interference image;

[0014] The detector is used to record the interference image and transmit it to the data acquisition and processing computer for numerical analysis;

[0015] The data acquisition and processing computer is used to perform numerical analysis on the interference image and solve the rotation angle of the plane reflector, thereby obtaining the rotation angle θ of the turntable to be measured.

[0016] Furthermore, a reflecting prism is arranged between the filtering and collimating module and the beam splitter to deflect the filtered and collimated laser by 90 degrees and emit it to the beam splitter.

[0017] Furthermore, a front mirror is arranged between the beam splitter and the plane reflector, for expanding the reflected light and emitting it to the plane reflector; the plane reflector reflects the expanded light beam back to the front mirror in the form of a plane wave, and the front mirror converges the plane wave and emits it to the beam splitter.

[0018] Furthermore, there is a filter and beam reducer group between the beam splitter and the detector, which is used to filter out stray light in the plane waves and spherical waves transmitted and reflected from the beam splitter respectively, and to reduce the beam so that the diameter of the output light beam is smaller than the width of the detector target surface, so that the detector can record the complete interference image.

[0019] Furthermore, the detector is a CCD area array camera or a CMOS area array camera.

[0020] Furthermore, the rotation angle of the plane reflector is calculated by the following formula:

[0021]

[0022] Where y is the plane wave width and R is the radius of curvature of the spherical wave.

[0023] At the same time, the present invention also provides a high-precision angle measurement method based on the Twyman-Green interference principle, which adopts the above-mentioned high-precision autocollimator based on the Twyman-Green interference principle, and its special feature is that it includes the following steps:

[0024] Step 1: Place a high-precision autocollimator based on the Twyman-Green interferometer principle on the experimental platform and use a level to adjust it to a horizontal state;

[0025] Step 2, place the plane reflector on the turntable to be tested, and adjust the plane reflector so that its reflection surface is perpendicular to the optical axis of the light reflected by the beam splitter, that is, the rotation angle θ of the plane reflector is 0;

[0026] Step 3, turn on the laser, and after the emitted laser is collimated and filtered by the filter collimation module, a beam of monochromatic parallel light is obtained;

[0027] Step 4, the obtained monochromatic parallel light is incident on a beam splitter, which splits it into a reflected light and a transmitted light;

[0028] Step 5, output one reflected light to the plane reflector, obtain a plane light wave after being reflected again by the plane reflector, and emit the plane light wave to the spectroscope; at the same time, make one transmitted light reflect by the reference reflector to obtain a spherical light wave, and output the spherical light wave to the spectroscope again;

[0029] Step 6, the plane light wave obtained in step 5 is transmitted through a beam splitter and then emitted to a detector, and at the same time, the spherical light wave obtained after reflection in step 5 is reflected again through a beam splitter and then emitted to a detector;

[0030] Step 7, causing the plane light wave and the spherical light wave to generate Tyeman-Green interference on the target surface of the detector, forming an interference image and recording it by the detector, and the detector transmits the recorded interference image to a data acquisition and processing computer;

[0031] Step 8, rotate the turntable to be tested to a certain set position, repeat steps 3 to 7, and the data acquisition and processing computer calculates the fringe offset by identifying the intensity and position data of the center of the interference image fringe, and obtains the rotation angle θ of the turntable to be tested through solution.

[0032] Furthermore, there is a step a between step 3 and step 4.

[0033] Step a, the obtained monochromatic parallel light is incident on a reflecting prism for reflection, so that its propagation direction is folded 90 degrees and then emitted to a beam splitter.

[0034] Furthermore, in step 5, one path of reflected light is expanded by a front mirror and then output to a plane reflector placed on a turntable to be measured, a plane light wave is obtained after being reflected by the plane reflector, and the plane light wave is again contracted by a front mirror and then emitted to a beam splitter.

[0035] Furthermore, in step 6, after the plane light wave is transmitted through the beam splitter, and after the spherical light wave is reflected again by the beam splitter, both are first incident on the filtering and beam reduction mirror group for filtering and beam reduction, and then emitted to the detector.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention provides a high-precision autocollimator and angle measurement method based on the Twyman-Green interference principle. By combining the optical interference principle with the working principle of the autocollimator, the present invention breaks through the limitations of the focal length, relative aperture and eyepiece magnification of the optical system on the measurement accuracy and measurement method in traditional geometric optical imaging, and also effectively avoids the experimental errors caused by various environmental factors such as temperature changes, airflow disturbances and vibrations of the experimental platform.

[0038] 2. The present invention provides a high-precision autocollimator and angle measurement method based on the Twiman-Green interference principle, wherein a computer calculates the rotation angle of a plane reflector by recording the offset of interference image fringes. Compared with the method of recording the light spot offset by a computer in a traditional autocollimator, this method is easier to be recognized by a computer, thereby obtaining an accurate offset and ensuring the measurement accuracy of the autocollimator. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic structural diagram of an embodiment of a high-precision autocollimator based on the Twyman-Green interferometer principle provided by the present invention;

[0040] Figure 2 A geometric principle diagram for angle measurement using an embodiment of the present invention;

[0041] Figure 3 is a position relationship diagram of a plane wave and a spherical wave when the plane reflector has no rotation angle, i.e., θ=0, in an embodiment of the present invention;

[0042] Figure 4 Schematic diagram of the interference result of the plane wave and the spherical wave on the target surface when the plane reflector has no rotation angle, that is, θ=0 in the embodiment of the present invention: wherein (a) is a diagram showing the position relationship between the plane wave and the spherical wave in the embodiment of the present invention; (b) is a schematic diagram showing the optical path difference between the plane wave and the spherical wave in the embodiment of the present invention; (c) is a curve diagram showing the grayscale change of the interference fringes in the embodiment of the present invention; (d) is a Newton ring produced by the interference of the plane wave and the spherical wave when θ=0 in the embodiment of the present invention;

[0043] Figure 5 : is a position relationship diagram of a plane wave and a spherical wave when the plane reflector has a rotation angle, that is, θ≠0, in an embodiment of the present invention;

[0044] Figure 6 The present invention is a schematic diagram of the interference between the plane wave and the spherical wave on the target surface when the plane reflector has a rotation angle, that is, θ≠0, in an embodiment of the present invention: wherein, (a) is a diagram showing the position relationship between the plane wave and the spherical wave in an embodiment of the present invention; (b) is a schematic diagram showing the optical path difference between the plane wave and the spherical wave in an embodiment of the present invention; (c) is a curve diagram showing the grayscale variation of the interference fringes in an embodiment of the present invention; and (d) is a Newton ring produced by the interference between the plane wave and the spherical wave when θ≠0 in an embodiment of the present invention.

[0045] Description of reference numerals:

[0046] 1-laser, 2-filter collimation module, 3-reflection prism, 4-front mirror, 5-plane reflector, 6-beam splitter, 7-reference reflector, 8-filter beam reducer, 9-detector, 91-detector target surface, 10-data acquisition and processing computer, U1-plane wave, U2-spherical wave, R-spherical wave curvature radius, θ-plane reflector rotation angle, S-movement of the center position of Newton rings. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0048] like Figure 1 As shown, a high-precision autocollimator based on the Twyman-Green interferometer principle of the present invention comprises:

[0049] A laser 1, a filter collimation module 2, a reflection prism 3 and a beam splitter 6 are sequentially arranged on the outgoing light path of the laser 1, wherein the beam splitter 6 is used to split the filtered and collimated laser into a reflected light and a transmitted light;

[0050] A reference reflector 7 arranged on the transmission light path of the beam splitter 6, a pre-mirror 4 and a plane reflector 5 arranged in sequence on the reflection light path of the beam splitter 6, a filter and beam reduction mirror group 8 arranged in sequence on the output light path of the beam splitter 6, a detector 9 and a data acquisition and processing computer 10 connected to the output end of the detector 9;

[0051] The filtering and collimating module 2 is used to filter and collimate the laser light emitted by the laser 1 to make it a beam of monochromatic parallel light;

[0052] The reflecting prism 3 is used to deflect the filtered and collimated laser light by 90° and emit it to the beam splitter 6;

[0053] The plane reflector 5 is placed on the rotating table to be measured, and is used to reflect the reflected light back to the beam splitter 6 in the form of a plane wave;

[0054] The front mirror 4 disposed between the beam splitter 6 and the plane reflector 5 is used to expand the reflected light and then emit it to the plane reflector 5; the plane reflector 5 reflects the expanded light beam back to the front mirror 4 in the form of a plane wave, and the front mirror 4 converges the plane wave and then emits it to the beam splitter 6;

[0055] The reference reflector 7 is a convex reflector, which is used to reflect the transmitted light back to the beam splitter 6 in the form of spherical waves;

[0056] The plane wave is transmitted through the beam splitter 6, and the spherical wave is reflected again by the beam splitter 6, and then filtered and beam-contracted by the filter-contractor group 8, and then emitted to the detector 9, and interferes on the target surface of the detector 9 to generate an interference image;

[0057] The detector 9 is a CCD area array camera or a CMOS area array camera, which is used to record the interference image and transmit it to the data acquisition and processing computer 10 for numerical analysis;

[0058] The data acquisition and processing computer 10 is used to perform numerical analysis on the interference image and solve the rotation angle of the plane reflector, thereby obtaining the rotation angle θ of the turntable to be measured.

[0059] Based on the above-mentioned high-precision autocollimator based on the Twyman-Green interferometer principle, a high-precision angle measurement method based on the Twyman-Green interferometer principle of the present invention comprises the following steps:

[0060] Step 1, place the autocollimator on the experimental platform and use a level to adjust it to a horizontal state;

[0061] Step 2, placing the plane reflector 5 on the turntable to be tested, and adjusting the plane reflector 5 so that its reflection surface is perpendicular to the optical axis of the light reflected by the beam splitter, that is, the rotation angle θ of the plane reflector 5 is 0;

[0062] Step 3, turn on the laser 1, and the emitted laser is collimated and filtered by the filtering and collimating module 2 to obtain a beam of monochromatic parallel light;

[0063] Step 4, the obtained monochromatic parallel light is incident on the beam splitter 6, and the beam splitter 6 divides it into a reflected light and a transmitted light; the obtained monochromatic parallel light is incident on the reflecting prism 3 for reflection, so that its propagation direction is folded 90° and then emitted to the beam splitter 6;

[0064] Step 5, make one reflected light beam expand through the front mirror 4 and then output to the plane reflector 5 placed on the turntable to be measured, obtain a plane light wave after reflection through the plane reflector 5, and then reduce the plane light wave through the front mirror 4 and then output to the beam splitter 6; at the same time, make one transmitted light beam reflect through the reference reflector 7 and then obtain a spherical light wave, and then output the spherical light wave to the beam splitter 6 again;

[0065] Step 6, after the plane light wave obtained in step 5 is transmitted through the beam splitter 6, and after the spherical light wave is reflected again through the beam splitter 6, both are first incident on the filter and beam reduction mirror group 8 for filtering and beam reduction, and then emitted to the detector 9;

[0066] Step 7, causing the plane light wave and the spherical light wave to generate Twyman-Green interference on the target surface of the detector 9, forming an interference image and recording it by the detector 9, and the detector 9 transmits the recorded interference image to the data acquisition and processing computer 10;

[0067] Step 8, rotate the turntable to be tested to a certain set position, repeat steps 3 to 7, the data acquisition and processing computer 10 calculates the fringe offset by identifying the intensity and position data of the interference image fringe center, and obtains the rotation angle θ of the turntable to be tested by solving.

[0068] In step 8, when the interference image is received by the detector and uploaded to the computer, the relationship between the center movement S of the Newton rings generated by the interference on the detector target surface and the plane mirror rotation angle θ is as follows: Figure 2 As shown, R is the radius of curvature of the spherical wave. Therefore, the computer calculates the plane mirror rotation angle θ, and the principle is as follows:

[0069] When the plane reflector is perpendicular to the direction of light propagation and there is no angle, θ can be considered to be 0. The positional relationship between the plane wave U1 and the spherical wave U2 on the target surface is as follows: Figure 3 As shown. At this time, the complex amplitude of the plane wave at any point (y, z) on the receiving surface can be expressed as:

[0070]

[0071] Where E0 is the light intensity of the plane wave, i.e. the amplitude; j is the imaginary unit; λ is the laser wavelength; z is the position of the wave in its propagation direction; y is the plane wave width; The term is the phase of the plane wave at the point (y,z);

[0072] The complex amplitude of the spherical wave at any point y on the receiving surface can be expressed as:

[0073]

[0074] Since the spherical wave obeys the paraxial condition, and the plane wave and the spherical wave are obtained by collimating and splitting the same light source, The above formula can be approximately expressed as

[0075]

[0076] Similarly, The term is the phase of the spherical wave at the point (y,z).

[0077] At this time, the total intensity at any point (y, z) on the detector target surface is:

[0078]

[0079] Where Δ is the optical path difference or phase difference between the two light waves,

[0080]

[0081] Substituting into the above formula, we have

[0082]

[0083] Depend on Figure 3 It can be seen that z = R, where R is the radius of curvature of the spherical wave, then:

[0084]

[0085] The interference result is Figure 4 As shown, (a) represents the position relationship between the plane wave and the spherical wave; (b) is a schematic diagram of the optical path difference between the plane wave and the spherical wave; (c) is a curve diagram of the grayscale change of the interference fringes; and (d) is the Newton rings produced by the interference recorded on the detector target surface.

[0086] When the plane reflector has a rotation angle θ, the position relationship between the plane wave U1 and the spherical wave U2 on the target surface is as follows: Figure 5 As shown. At this time, the complex amplitude of the plane wave at any point (y, z) on the receiving surface can be expressed as:

[0087]

[0088] The complex amplitude of the spherical wave at any point (y, z) on the receiving surface can be expressed as:

[0089]

[0090] At this time there are:

[0091]

[0092]

[0093] Among them

[0094]

[0095]

[0096]

[0097] Where μ is the modulation frequency, f0 is the initial frequency, is the phase constant. Then the total intensity at any point (y, z) on the detector target surface can be expressed as:

[0098]

[0099] The results of the interference are as follows Figure 6 , where (a) represents the positional relationship between the plane wave and the spherical wave; (b) is a schematic diagram of the optical path difference between the plane wave and the spherical wave; (c) is a graph showing the grayscale variation of the interference fringes; and (d) is the Newton rings produced by the interference recorded on the detector target surface at this time.

[0100] It can be seen from the above formula that the intensity distribution of the interference fringes on the receiving surface is a linear frequency modulation signal, that is, a chirp signal, also known as a chirp signal.

[0101] In the present invention, fractional Fourier transform is used to process chirp-like signals to obtain:

[0102]

[0103] Among them, α is the fractional order, indicating the degree of transformation, f m is the frequency modulation of the signal at time t, T is the transmission time width, so when f m = 0, at the center of the baseband chirp signal:

[0104]

[0105] θ is the rotation angle of the plane mirror, which is the rotation angle of the turntable to be measured.

[0106] 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 them. For ordinary professional and technical personnel in the field, the specific technical solutions recorded in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present invention.

Claims

1. A high-precision autocollimator based on the Twyman-Green interferometer principle, characterized in that: It comprises a laser (1), a filtering and collimating module (2) and a beam splitter (6) which are sequentially arranged on the output light path of the laser (1), wherein the beam splitter (6) is used to split the filtered and collimated laser light into a reflected light path and a transmitted light path; It also includes a reference reflector (7) arranged on the transmission light path of the beam splitter (6), a plane reflector (5) arranged on the reflection light path of the beam splitter (6), a detector (9) arranged on the output light path of the beam splitter (6), and a data acquisition and processing computer (10) connected to the output end of the detector (9); The filtering and collimating module (2) is used to filter and collimate the laser light emitted by the laser (1) so as to make it a beam of monochromatic parallel light; The reference reflector (7) is a convex reflector, used to reflect the transmitted light back to the beam splitter (6) in the form of a spherical wave; The plane reflector (5) is placed on the rotating platform to be measured, and is used to reflect the reflected light back to the beam splitter (6) in the form of a plane wave; The plane wave is transmitted through the beam splitter (6), and the spherical wave is reflected again by the beam splitter (6), and then emitted from the beam splitter (6) to the detector (9), where interference occurs on the target surface of the detector (9) and an interference image is generated; The detector (9) is used to record the interference image and transmit it to the data acquisition and processing computer (10) for numerical analysis; The data acquisition and processing computer (10) is used to perform numerical analysis on the interference image and solve the rotation angle of the plane reflector, thereby obtaining the rotation angle θ of the turntable to be measured.

2. A high-precision autocollimator based on the Twyman-Green interferometer principle according to claim 1, characterized in that: A reflecting prism (3) is also provided between the filtering and collimating module (2) and the beam splitter (6) and is used to fold the filtered and collimated laser light by 90 degrees and emit it to the beam splitter (6).

3. A high-precision autocollimator based on the Twyman-Green interferometer principle according to any one of claims 1 or 2, characterized in that: A front mirror (4) is also provided between the beam splitter (6) and the plane reflector (5) for expanding the reflected light and then emitting it to the plane reflector (5); the plane reflector (5) reflects the expanded light beam back to the front mirror (4) in the form of a plane wave, and the front mirror (4) converges the plane wave and then emits it to the beam splitter (6).

4. The high-precision autocollimator based on the Twyman-Green interferometer principle according to claim 3, characterized in that: A filtering and beam reduction mirror group (8) is also provided between the beam splitter (6) and the detector (9) for filtering out stray light in the plane wave and the spherical wave respectively transmitted and reflected from the beam splitter (6), and for beam reduction so that the diameter of the outgoing light beam is smaller than the width of the target surface of the detector (9), so that the detector (9) can record a complete interference image.

5. The high-precision autocollimator based on the Twyman-Green interferometer principle according to claim 4, characterized in that: The detector (9) is a CCD area array camera or a CMOS area array camera.

6. A high-precision autocollimator based on the Twyman-Green interferometer principle according to claim 5, characterized in that: The plane reflector angle is calculated by the following formula: Where y is the plane wave width and R is the radius of curvature of the spherical wave.

7. A high-precision angle measurement method based on the Twyman-Green interferometer principle, using a high-precision autocollimator based on the Twyman-Green interferometer principle as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Place a high-precision autocollimator based on the Twyman-Green interferometer principle on the experimental platform and use a level to adjust it to a horizontal state; Step 2, placing the plane reflector (5) on the turntable to be tested, and adjusting the plane reflector (5) so that its reflection surface is perpendicular to the optical axis of the light reflected by the beam splitter (6), that is, the rotation angle θ of the plane reflector (5) = 0; Step 3, turning on the laser (1), and the emitted laser light is collimated and filtered by the filtering and collimating module (2) to obtain a beam of monochromatic parallel light; Step 4, the obtained monochromatic parallel light is incident on a beam splitter (6), and the beam splitter (6) splits the monochromatic parallel light into a reflected light and a transmitted light; Step 5, output one reflected light to the plane reflector (5), and obtain a plane light wave after being reflected again by the plane reflector (5), and output the plane light wave to the beam splitter (6); at the same time, obtain a spherical light wave after being reflected by the reference reflector (7), and output the spherical light wave to the beam splitter (6) again; Step 6, the plane light wave obtained in step 5 is transmitted through the beam splitter (6) and then emitted to the detector (9), and at the same time, the spherical light wave obtained after reflection in step 5 is reflected again through the beam splitter (6) and then emitted to the detector (9); Step 7, causing the plane light wave and the spherical light wave to generate Twyman-Green interference on the target surface of the detector (9), forming an interference image which is recorded by the detector (9), and the detector (9) transmits the recorded interference image to the data acquisition and processing computer (10); Step 8, rotating the turntable to be tested to a certain set position, repeating steps 3 to 7, the data acquisition and processing computer (10) calculates the fringe offset by identifying the intensity and position data of the center of the interference image fringe, and obtains the rotation angle θ of the turntable to be tested by solving the calculation.

8. The high-precision angle measurement method based on the Twyman-Green interferometer principle according to claim 7, characterized in that: There is also step a between step 3 and step 4: Step a, the obtained monochromatic parallel light is incident on a reflecting prism (3) for reflection, so that its propagation direction is deflected by 90 degrees and then emitted to a beam splitter (6).

9. A high-precision angle measurement method based on the Twyman-Green interferometry principle according to any one of claims 7 or 8, characterized in that: In step 5, one path of reflected light is expanded by the front mirror (4) and then output to the plane reflector (5) placed on the turntable to be measured, and a plane light wave is obtained after being reflected by the plane reflector (5). The plane light wave is then contracted by the front mirror (4) again and then output to the beam splitter (6).

10. The high-precision angle measurement method based on the Twyman-Green interferometer principle according to claim 9, characterized in that: In step 6, after the plane light wave is transmitted through the beam splitter (6), and after the spherical light wave is reflected again by the beam splitter (6), both are first incident on the filtering and beam reduction mirror group (8) for filtering and beam reduction, and then emitted to the detector (9).

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