A high-precision autocollimator and angle measurement method based on the Tyman Green interference principle

Abstract

The application provides a high-precision autocollimator based on the Tyman Green interference principle and an angle measuring method, aiming at solving the problem that the prior art cannot continue to break through the existing angle measuring precision due to the limitation of geometric optical principle and the influence of environmental factors. The autocollimator comprises a laser, a filtering collimation module, a beam splitter, a reference mirror, a plane mirror, a detector and a data acquisition and processing computer. After the autocollimator is leveled, the plane mirror is placed on a turntable to be measured, and the measurement is carried out when the turntable has no rotation angle and has a rotation angle, so that the laser is emitted to the filtering collimation module to be emitted as monochromatic parallel light to the beam splitter and is divided into two paths. One path is reflected by the plane mirror and then passes through the beam splitter to reach the detector again. The other path is reflected by the reference mirror and then reflected by the beam splitter to reach the detector again. The two beams interfere on the target surface of the detector, the detector records the interference image and uploads it to the computer to calculate the interference fringe offset, so that the angle measurement is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to a collimator, in particular to a high-precision collimator based on the Tyman Green interference principle and an angle measuring method. BACKGROUND

[0002] Since the 1990s, with the development of photoelectric detection technology and image processing technology, the collimator has been further developed in the field of photoelectricity, and the measuring range, measuring accuracy, measuring speed and intelligence of the instrument have been greatly improved. At present, the representative photoelectric collimators are CSZ-1 of the 6354 Institute of China Shipbuilding Heavy Industry, with an objective focal length of 550 mm, a clear aperture of 50 mm, a measuring range of 300″x300″, and a measuring accuracy of ±0.5″; and Auto MAT 5000 of Tianjin Automer Optoelectronic Technology Co., Ltd., with an objective focal length of 300 mm, a clear aperture of 50 mm, a measuring range of 1000″x1000″, and a measuring accuracy of ±0.2″. However, it is worth noting that the traditional photoelectric collimator is based on the principle of geometric optics, and the measuring principle is the tangent theorem. The resolution is mainly determined by the focal length of the optical system and the image line resolution. The longer the focal length of the optical system, the higher the image line resolution of the system, and the higher the resolution of the collimator, and the higher the measuring accuracy. However, due to the limitation of the aperture of the optical system, the focal length cannot be too long, and the image line resolution is also limited by the size of the photoelectric detector pixel or the magnification of the eyepiece, and cannot be further improved, and a more complex calibration procedure is needed to ensure its accuracy. In addition, the long focal length and large aperture optical system used for the pursuit of measuring accuracy is extremely sensitive to environmental conditions. Temperature changes, air flow disturbances and experimental platform vibrations will affect the direction and quality of the light beam. The manufacturing precision and surface quality of the optical elements such as lenses and mirrors used in the system also directly affect the measuring accuracy of the collimator. Therefore, the traditional collimator based on the principle of geometric optics has basically reached its own bottleneck, and it is urgent to have a breakthrough in the theory and technical means to improve the angle measuring accuracy of the collimator. SUMMARY

[0003] The main purpose of the present application is to solve the problem that the traditional collimator based on geometric optics is limited by the focal length of the optical system, the relative aperture, the size of the photoelectric detector pixel or the magnification of the eyepiece, especially the long focal length and large aperture optical system is greatly affected by environmental factors, so that the existing angle measuring accuracy cannot be further improved, and a high-precision collimator based on the Tyman Green interference principle and an angle measuring method are provided.

[0004] The concept of the present application is:

[0005] Based on the Tyman Green interference principle, by modulating the reference light, a specific interference image is obtained, and a specific analysis method is used to solve the attitude information of the test beam, that is, the angle information of the test beam; By comprehensively using optical interference, optical field modulation, fractional Fourier analysis, numerical analysis and other technologies, real-time, efficient and high-precision autocollimation angle measurement test is realized.

[0006] To achieve the above-mentioned purposes and complete the above-mentioned ideas, the present application provides the following technical solutions:

[0007] A high-precision autocollimator based on the Tyman Green interference principle, characterized in that:

[0008] The laser, the filter collimation module and the beam splitter are sequentially arranged on the light path of the laser, wherein the beam splitter is used to divide the filtered and collimated laser into one reflected light and one transmitted light;

[0009] It also includes a reference mirror arranged on the transmitted light path of the beam splitter, a plane mirror arranged on the reflected light path of the beam splitter, a detector arranged on the exit light path of the beam splitter, and a data acquisition and processing computer connected to the output end of the detector;

[0010] The filter collimation module is used to filter and collimate the laser emitted by the laser to form a monochromatic parallel light;

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

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

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

[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 mirror, and then obtain the rotation angle θ of the measured rotary table.

[0016] Further, a reflecting prism is arranged between the filter collimation module and the beam splitter to fold and turn the filtered and collimated laser by 90° and emit it to the beam splitter.

[0017] Further, a pre-mirror is arranged between the beam splitter and the plane mirror, used for expanding the reflected light and then emitting the expanded light to the plane mirror; the plane mirror reflects the expanded light in the form of plane wave to the pre-mirror, and the pre-mirror converges the plane wave and then emits the converged light to the beam splitter.

[0018] Further, a filter and converging lens group is arranged between the beam splitter and the detector, used for filtering the stray light in the plane wave and the spherical wave respectively transmitted and reflected by the beam splitter, and converging the light, so that the diameter of the emitted light is smaller than the width of the target surface of the detector, and the detector can record the complete interference image.

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

[0020] Further, the rotation angle of the plane mirror is calculated by the following formula:

[0021]

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

[0023] Meanwhile, the application also provides a high-precision angle measuring method based on the Talbot-Maher-Green interference principle, which adopts the above high-precision autocollimator based on the Talbot-Maher-Green interference principle, and the speciality thereof lies in comprising the following steps:

[0024] Step 1, placing the high-precision autocollimator based on the Talbot-Maher-Green interference principle on an experimental platform, and adjusting it to a horizontal state by using a level;

[0025] Step 2, placing the plane mirror on a rotary table to be measured, and adjusting the plane mirror so that the reflecting surface is perpendicular to the optical axis of the reflected light of the beam splitter, i.e. the rotation angle of the plane mirror is 0;

[0026] Step 3, turning on the laser, and obtaining a monochromatic parallel light by collimating and filtering the emitted laser light by the filter and collimating module;

[0027] Step 4, making the obtained monochromatic parallel light incident to the beam splitter, and dividing the monochromatic parallel light into a reflected light and a transmitted light by the beam splitter;

[0028] Step 5, making the reflected light output to the plane mirror, and obtaining a plane wave by reflecting the reflected light by the plane mirror again, and making the plane wave output to the beam splitter; meanwhile, making the transmitted light output to the beam splitter again by reflecting the transmitted light by the reference mirror to obtain a spherical wave;

[0029] Step 6, making the plane wave obtained in step 5 output to the detector by transmitting the plane wave by the beam splitter, and making the spherical wave obtained by reflecting the spherical wave in step 5 output to the detector again by reflecting the spherical wave by the beam splitter.

[0030] Step 7, the plane wave and the spherical wave generate a Talbot interference on the detector target surface to form an interference image and be recorded by the detector, and the detector transmits the recorded interference image to the data acquisition and processing computer;

[0031] Step 8, the rotation table to be measured is rotated to a certain set position, steps 3 to 7 are repeated, the data acquisition and processing computer calculates the fringe offset through the intensity and position data of the interference image fringe center, and obtains the rotation angle θ of the rotation table to be measured through solving.

[0032] Further, between step 3 and step 4, there is also step a,

[0033] Step a, the obtained monochromatic parallel light is incident on the reflecting prism to be reflected, so that the propagation direction is turned by 90° and then emitted to the beam splitter.

[0034] Further, in step 5, one way of reflected light is expanded by the pre-mirror and then output to the plane mirror placed on the rotation table to be measured, a plane wave is obtained after being reflected by the plane mirror, and the plane wave is again contracted by the pre-mirror and then emitted to the beam splitter.

[0035] Further, in step 6, after the plane wave is transmitted by the beam splitter and the spherical wave is reflected by the beam splitter again, both are first incident to the filtering and contracting lens group to be filtered and contracted, and then emitted to the detector.

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

[0037] 1. The high-precision autocollimator and the angle measuring method based on the Talbot interference principle provided by the present application combine the optical interference principle with the working principle of the autocollimator, break through the limitations of the focal length, relative aperture and eyepiece magnification of the optical system in the traditional geometric optical imaging on the measurement precision and the measurement method, effectively avoid the experimental errors caused by various environmental factors such as temperature change, air flow disturbance and experimental platform vibration, and the like.

[0038] 2. The high-precision autocollimator and the angle measuring method based on the Talbot interference principle provided by the present application, wherein the computer calculates the rotation angle of the plane mirror through the recorded interference image fringe offset, compared with the method of recording the spot offset by the computer in the traditional autocollimator, the method is more easily identified by the computer, so as to obtain the accurate offset and ensure the measurement precision of the autocollimator. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The structure schematic view of the high-precision autocollimator based on the Talbot interference principle provided by the present application is shown in the embodiment.

[0040] Figure 2 This is a geometric schematic diagram illustrating the angle measurement using an embodiment of the present invention.

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

[0042] Figure 4 This is a schematic diagram showing the interference result of a plane wave and a spherical wave on a target surface when the plane mirror has no rotation angle (θ = 0) in an embodiment of the present invention: (a) is a diagram showing the positional 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 diagram showing the grayscale variation curve of the interference fringes in an embodiment of the present invention; and (d) is a diagram showing the Newton's rings generated by the interference between the plane wave and the spherical wave when θ = 0 in an embodiment of the present invention.

[0043] Figure 5 This is a diagram showing the positional relationship between the plane wave and the spherical wave when the plane mirror has a rotation angle, i.e., θ≠0, in an embodiment of the present invention.

[0044] Figure 6 The diagram below shows the interference results of a plane wave and a spherical wave on a target surface when the plane mirror has a rotation angle (θ≠0) in an embodiment of the present invention: (a) is a diagram showing the positional relationship between the plane wave and the spherical wave in an embodiment of the present invention; (b) is a diagram showing the optical path difference between the plane wave and the spherical wave in an embodiment of the present invention; (c) is a diagram showing the grayscale variation curve of the interference fringes in an embodiment of the present invention; and (d) is a diagram showing the Newton's rings generated by the interference between the plane wave and the spherical wave when θ≠0 in an embodiment of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1-Laser, 2-Filtering and collimating module, 3-Reflecting prism, 4-Front mirror, 5-Plane mirror, 6-Beam splitter, 7-Reference mirror, 8-Filtering and beam-shrinking mirror group, 9-Detector, 91-Detector target surface, 10-Data acquisition and processing computer, U1-Plane wave, U2-Spherical wave, R-Spherical wave radius of curvature, θ-Plane mirror rotation angle, S-Motion of the center position of Newton's rings. Detailed Implementation

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

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

[0049] Laser 1, filter collimation module 2, reflection prism 3 and beam splitter 6 are sequentially arranged in the output optical path of laser 1, wherein beam splitter 6 is used to split the filtered and collimated laser into a reflected light and a transmitted light.

[0050] Reference mirror 7 is arranged on the transmission light path of beamsplitter 6, pre-mirror 4 and plane mirror 5 are arranged on the reflection light path of beamsplitter 6 in sequence, filter and beam-reducing mirror group 8 is arranged on the exit light path of beamsplitter 6 in sequence, detector 9 and data acquisition and processing computer 10 connected to the output end of detector 9 are arranged;

[0051] The filter and collimation module 2 is used for filtering and collimating the laser emitted by the laser 1 to become a monochromatic parallel light;

[0052] The reflecting prism 3 is used for folding and emitting the filtered and collimated laser to the beamsplitter 6 by 90°;

[0053] The plane mirror 5 is placed on the measured rotary table, and is used for reflecting the reflected light in the form of plane wave back to the beamsplitter 6;

[0054] The pre-mirror 4 arranged between the beamsplitter 6 and the plane mirror 5 is used for expanding the reflected light and emitting it to the plane mirror 5; the plane mirror 5 reflects the expanded light beam in the form of plane wave back to the pre-mirror 4, and the pre-mirror 4 collects the plane wave and emits it to the beamsplitter 6;

[0055] The reference mirror 7 is a convex mirror, which is used for reflecting the transmitted light in the form of spherical wave back to the beamsplitter 6;

[0056] The plane wave is transmitted through the beamsplitter 6, and the spherical wave is reflected by the beamsplitter 6 again, then filtered and reduced by the filter and beam-reducing mirror group 8, and emitted to the detector 9, and interference images are generated on the target surface of the detector 9;

[0057] The detector 9 is a CCD area array camera or a CMOS area array camera, which is used for recording the interference images and transmitting them to the data acquisition and processing computer 10 for numerical analysis;

[0058] The data acquisition and processing computer 10 is used for numerical analysis of the interference images, and solving the rotation angle of the plane mirror, and then obtaining the rotation angle θ of the measured rotary table.

[0059] Based on the above-mentioned high-precision autocollimator based on the Tyman Green interference principle, the high-precision angle measuring method based on the Tyman Green interference principle comprises the following steps:

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

[0061] Step 2, place the plane mirror 5 on the measured rotary table, and adjust the plane mirror 5 so that the reflecting surface is perpendicular to the optical axis of the reflected light of the beamsplitter, that is, the rotation angle θ of the plane mirror 5 is 0;

[0062] Step 3, open the laser 1, the emitted laser is collimated and filtered by the filter collimation module 2, and a monochromatic parallel light is obtained;

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

[0064] Step 5, the reflected light is expanded by the pre-mirror 4 and then output to the plane mirror 5 placed on the rotary table to be measured, and a plane light wave is obtained after reflection by the plane mirror 5, and the plane light wave is output to the beam splitter 6 again after being contracted by the pre-mirror 4; at the same time, the transmitted light is reflected by the reference mirror 7 to obtain a spherical light wave, and the spherical light wave is output to the beam splitter 6 again;

[0065] Step 6, the plane light wave obtained in step 5 is transmitted by the beam splitter 6, and the spherical light wave is reflected by the beam splitter 6 again, both of which are first incident to the filter and contraction lens group 8 for filtering and contraction, and then output to the detector 9;

[0066] Step 7, the plane light wave and the spherical light wave produce a Talbot interference on the target surface of the detector 9, form an interference image and are recorded 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 rotary table to be measured to a certain set position, repeat steps 3 to 7, the data acquisition and processing computer 10 calculates the fringe shift by identifying the intensity and position data of the center of the interference image fringe, and obtains the rotation angle θ of the rotary table to be measured 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 ring produced by the interference on the target surface of the detector and the rotation angle θ of the plane mirror is as shown in Figure 2 , wherein R is the curvature radius of the spherical wave. Thus, the computer solves the rotation angle θ of the plane mirror, and the principle is as follows:

[0069] When the plane mirror is perpendicular to the direction of light propagation and there is no rotation angle, θ can be considered as 0, and the position relationship between the plane wave U1 and the spherical wave U2 on the target surface is as shown in Figure 3 . 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] wherein E0 is the light intensity of the plane wave, i.e. the amplitude; j is the imaginary unit; λ is the wavelength of the laser; z is the position of the wave in its propagation direction; y is the width of the plane wave; 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 plane can be expressed as:

[0073]

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

[0075]

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

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

[0078]

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

[0080]

[0081] Substituting the above formula gives

[0082]

[0083] From Figure 3 It can be known that z = R, where R is the radius of curvature of the spherical wave, so we have:

[0084]

[0085] The interference result is shown in Figure 4 , where (a) represents the position relationship between the plane wave and the spherical wave; (b) is the optical path difference diagram of the plane wave and the spherical wave; (c) is the gray scale change curve of the interference fringes; (d) is the Newton's ring recorded by the detector target surface.

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

[0087]

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

[0089]

[0090] At this time:

[0091]

[0092]

[0093] Wherein let

[0094]

[0095]

[0096]

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

[0098]

[0099] The interference results are as follows: Figure 6 Wherein (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 curve diagram of the gray scale change of the interference fringes; and (d) is the Newton ring recorded by the detector target surface at this time.

[0100] From the above formula, it can be seen that the intensity distribution of the interference fringes on the receiving surface is a chirp signal, also known as a chirp signal.

[0101] In the present application, the chirp signal is processed by using fractional Fourier transform, and the following formula can be obtained:

[0102]

[0103] Wherein α is the fractional order, indicating the degree of transformation, f m The frequency modulation of the signal at time t is f, and T is the transmission time width. Therefore, when f m = 0, there is:

[0104]

[0105] θ is the rotation angle of the plane mirror, that is, the rotation angle of the to-be-measured rotary table to be obtained.

[0106] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same. For those skilled in the art, the specific technical solutions described in the foregoing examples can be modified, or some of the technical features 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 application.

Claims

1. A high-precision autocollimator based on the Twyman-Green interferometry principle, characterized in that: It includes a laser (1), a filtering and collimating module (2) and a beam splitter (6) arranged sequentially on the output optical 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; It also includes a reference mirror (7) set in the transmission optical path of the beam splitter (6), a plane mirror (5) set in the reflection optical path of the beam splitter (6), a detector (9) set in the output optical 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 collimation module (2) is used to filter and collimate the laser emitted from the laser (1) so that it becomes a monochromatic parallel light beam; The reference mirror (7) is a convex mirror used to reflect the transmitted light back to the beam splitter (6) in the form of a spherical wave. The plane mirror (5) is placed on the test turntable 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 it interferes on the target surface of the detector (9) and generates an interference image. 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 calculate the rotation angle of the plane mirror, thereby obtaining the rotation angle θ of the turntable under test.

2. A high-precision autocollimator based on the Twyman-Green interferometry 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) to fold the filtered and collimated laser by 90° and send it out to the beam splitter (6).

3. A high-precision autocollimator based on the Twyman-Green interferometry 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 mirror (5) to expand the reflected light and send it out onto the plane mirror (5); the plane mirror (5) reflects the expanded beam back to the front mirror (4) in the form of a plane wave, and the front mirror (4) gathers the plane wave and sends it out to the beam splitter (6).

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

5. A high-precision autocollimator based on the Twyman-Green interferometry 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 interferometry principle according to claim 5, characterized in that, The rotation angle of the plane mirror is calculated using 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 interferometry principle, using a high-precision autocollimator based on the Twyman-Green interferometry principle as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Place the high-precision autocollimator based on the Twyman Green interferometry principle on the experimental platform and use a level to adjust it to a horizontal state. Step 2: Place the plane mirror (5) on the turntable to be tested, and adjust the plane mirror (5) so that its reflecting surface is perpendicular to the optical axis of the light reflected by the beam splitter (6), that is, the plane mirror (5) rotates at an angle θ = 0. Step 3: Turn on the laser (1). The emitted laser light is collimated and filtered by the collimation module (2) to obtain a beam of monochromatic parallel light. Step 4: The obtained monochromatic parallel light is incident on the beam splitter (6), which splits it into a reflected light and a transmitted light. Step 5: Output one reflected light to the plane mirror (5), so that it is reflected again by the plane mirror (5) to obtain a plane light wave, and output the plane light wave to the beam splitter (6); at the same time, output one transmitted light to the reference mirror (7) to obtain a spherical light wave, 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). 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: The plane light wave and the spherical light wave generate Thyman Green interference on the target surface of the detector (9), forming an interference image which is recorded by the detector (9). The detector (9) transmits the recorded interference image to the data acquisition and processing computer (10). 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 (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 problem.

8. A high-precision angle measurement method based on the Twyman-Green interferometry principle according to claim 7, characterized in that, There is another step, a, between step 3 and step 4: Step a: The obtained monochromatic parallel light is incident on the reflecting prism (3) for reflection, so that its propagation direction is folded by 90° and then emitted to the 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 reflected light is expanded by the front mirror (4) and output to the plane mirror (5) placed on the turntable to be tested. After being reflected by the plane mirror (5), a plane light wave is obtained, and the plane light wave is again reduced by the front mirror (4) and output to the beam splitter (6).

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

Images