Angle measurement method and device based on micro-wavelength difference two-wavelength interference

Abstract

The present application relates to the field of optical precision measurement, and discloses an angle measurement method and device based on micro-wavelength difference dual-wavelength interference, comprising the following steps: using a micro-wavelength difference dual-wavelength extended light source, generating isoclinal interference fringes through a Michelson interferometer; using a linear moving mechanism with adjustable tilt direction to move the plane mirror of the test light beam along the tilt direction; and indirectly measuring the tilt angle through the fringe change characteristics of the micro-wavelength difference dual-wavelength interference. The interference method and device for measuring the angle are simple and easy to operate, and are convenient to install and debug; are suitable for high-precision measurement of micro-angles and angles near 180 degrees; use the blurring or clarity of the interference fringes as the basis for judgment and positioning, are sensitive in response, have good accuracy, and are also suitable for computer automatic analysis and processing; and can obtain precision of the order of seconds by using a low-precision linear displacement mechanism to obtain high-precision angle measurement.

Description

Technical Field

[0001] This invention relates to the field of optical precision measurement technology, specifically to an angle measurement method and apparatus based on dual-wavelength interference with a small wavelength difference. Background Technology

[0002] In the engineering practice of optical precision measurement, angles can be measured using the following methods: theodolite method (or telescope aiming method), double-wedge reciprocal rotation method, autocollimator method, moiré fringe method, optical interferometry (including equal thickness interferometry and equal inclination interferometry), laser Doppler frequency shift interferometry, and optical diffraction method. The first four methods are based on the principles of geometric optics, while the latter three are based on the principles of physical optics.

[0003] Methods based on geometric optics for angle measurement generally have a large measurement range, reaching tens of degrees or more. However, they mostly rely on mechanical optical rotary tables, and their accuracy depends on the precision of the dividing head, resulting in relatively low measurement accuracy, typically below 10 minutes. Improving measurement accuracy requires the use of electronic digital counting devices, which is more complex. Methods based on physical optics generally have a smaller measurement range, within 10 degrees. They mostly use interference or diffraction fringe counting methods, offering higher measurement accuracy, typically reaching several seconds.

[0004] Given the contradiction between the accuracy and range of low-coherence angle measurement, it is necessary to develop an angle measurement method that is low in implementation cost, easy to operate, has a large measurement range, and sufficiently high accuracy. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides an angle measurement method and apparatus based on dual-wavelength interferometry with a small wavelength difference. The method for measuring angles is simple and easy to implement, and the apparatus is convenient to install and debug. It is suitable for high-precision measurement of small angles and angles near 180°. Using the blurriness or clarity of the interferogram as a basis for judgment and positioning, it is highly sensitive and accurate. The image data analysis method for positioning with blurry or clear interferograms is suitable for automated analysis and processing. High-precision angle measurement is achieved using a low-precision linear displacement mechanism, achieving accuracy on the order of seconds. This solves the problems of methods based on geometric optics principles having a large angle measurement range but low accuracy, and methods based on physical optics principles having high angle measurement accuracy but a small measurement range.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: an angle measurement method based on dual-wavelength interference with a small wavelength difference, comprising the following steps:

[0009] S1. A dual-wavelength extended light source with a small wavelength difference is used to generate equal-inclination interference fringes through a Michelson interferometer;

[0010] S2. Using an adjustable tilting linear movement mechanism, the plane mirror of the test beam is moved along the tilting direction.

[0011] S3. The tilt angle is indirectly measured by measuring the distance the plane mirror moves when the interference fringes are most blurred in two consecutive instances during the tilting process.

[0012] S4. Calculate the measured angle based on the difference between the two inclination angles.

[0013] Preferably, the light emitted by the dual-wavelength light source with small wavelength difference becomes an extended light source after passing through the frosted glass screen. After passing through the cubic beam splitter prism, it is separated into two coherent beams. The beam reflected upward is the reference beam, and the beam that passes directly through the cubic beam splitter prism is the test beam.

[0014] The reference beam is reflected by the reference beam mirror and returns along the original path, then passes through the cubic beam splitter to reach the CCD camera;

[0015] The test beam is reflected by the test beam mirror and returns along the original path. It is then reflected by the cubic beam splitter prism and reaches the CCD camera in the same way.

[0016] A CCD camera can be used to focus on an extended light source at infinity to observe equal-inclination interference fringes, or the naked eye can be used to directly focus on an extended light source at infinity to observe equal-inclination interference fringes.

[0017] Preferably, the test beam reflector is adjusted to move continuously along the direction of the main ray of the beam;

[0018] Let the two wavelengths of a dual-wavelength light source with a small wavelength difference be λ1 and λ2, then the wavelength difference is Δλ = λ2 - λ1;

[0019] The observed equal-inclination interference fringes periodically alternate between blurred and clear. During the continuous periodic repetition of the interference fringes with the minimum blur contrast, the corresponding period of the distance the test beam mirror moves along the principal ray in the test beam path is Δe = e2 - e1, where e1 and e2 are the positions of the test beam mirror when the blur contrast of the equal-inclination interference fringes is the minimum in two adjacent periods.

[0020] According to the principles of physical optics, the calculation formula is as follows:

[0021]

[0022] Considering the small wavelength difference between the two wavelengths, the average wavelength can be approximated as squared. Substituting into formula (1), we get:

[0023]

[0024] Preferably, the test beam reflector is adjusted to move along the tilt direction of the principal ray, and the reflecting surface of the test beam reflector remains perpendicular to the principal ray of the beam;

[0025] Let α be the angle between the tilting direction of the test beam reflector and the mirror surface, let c be the displacement of the test beam reflector along the tilting direction, and let b be the distance the reflector moves along the principal ray direction. The calculation formula is as follows:

[0026] b = c × sinα (3)

[0027] In the formula, the displacement c in the tilt direction is the displacement measured directly, and the displacement b of the test beam reflector along the direction of the principal ray is the displacement measured indirectly.

[0028] Preferably, when indirectly measuring the displacement of the reflector surface along the principal ray direction by tilting the test beam reflector, Δe in equation (1) or (2) should be replaced with Δe×sinα. In this case, Δe is the distance the test beam reflector moves when the two consecutive fringes are most blurred (lowest contrast) along the tilt direction, and α is the tilt angle of the moving direction; then equation (2) is modified as follows:

[0029]

[0030] By selecting a suitable light source with a known small wavelength difference between two wavelengths λ1 and λ2, and measuring the distance Δe by which the test beam mirror moves along the tilt direction of the tilt angle α when the contrast of the interference fringes is minimized in two consecutive instances, the tilt angle α can be indirectly measured. Therefore, equation (4) is transformed into:

[0031]

[0032] The inclination angle is obtained from equation (5):

[0033]

[0034] The tilt angle measurement error caused by a single measurement is obtained by mathematical differentiation from equation (6):

[0035]

[0036] Preferably, the tilt angle measurement error caused by a single measurement can also be obtained by mathematical differentiation operation using equation (5):

[0037]

[0038] As can be seen from equation (8), during measurement, the smaller the tilt angle value, that is, the closer it is to the 0° starting angle position, the greater the distance Δe that it moves when the interference fringes are most blurred (the contrast is the smallest) in two consecutive times, and the smaller the angular position measurement error caused.

[0039] Preferably, the apparatus for implementing an angle measurement method based on dual-wavelength interferometry with a small wavelength difference includes:

[0040] A dual-wavelength light source with a slight wavelength difference;

[0041] A Michelson interferometer, comprising a frosted glass screen, a cubic beam splitter prism, a reference beam mirror, and a test beam mirror;

[0042] A CCD camera was used to observe equal-inclination interference fringes.

[0043] The tilting linear movement mechanism is used to adjust the tilting direction of the test beam reflector;

[0044] A displacement measuring device used to measure the distance the test beam reflector moves along the tilt direction.

[0045] Preferably, the tilting linear movement mechanism includes a coarse adjustment translation stage, a first rotary stage, a linear translation stage, a second rotary stage, and a planar reflecting mirror frame;

[0046] The tilting direction of the test beam reflector is adjusted by rotating the first and second rotary tables, and the displacement of the test beam reflector in the tilting direction is measured by moving the linear translation stage.

[0047] Preferably, both the first and second rotary tables consist of a fixed base and a rotatable surface, and the surface can rotate within a 360° range relative to the base around its respective central axis.

[0048] The linear translation stage consists of a stationary base and a movable surface. The surface can move parallel to the center line in the horizontal plane relative to the base, and the distance or position value of the movement can be read.

[0049] Preferably, the test beam reflector is mounted on a plane reflector frame, which is fixedly connected to a column. The plane reflector frame is used to adjust the pitch of the test beam reflector surface relative to the vertical plane, and the column is used to adjust the height of the test beam reflector.

[0050] (III) Beneficial Effects

[0051] Compared with the prior art, the present invention provides an angle measurement method and apparatus based on dual-wavelength interference with a small wavelength difference, which has the following advantages:

[0052] The present invention provides a simple and easy-to-implement method for measuring angles, and the device is convenient to install and debug. It is suitable for high-precision measurement of small angles and angles around 180°. It uses the fuzziness or clarity of the interferogram as the basis for judgment and positioning, and is highly sensitive and accurate. It is also suitable for automated computer analysis and processing. It uses a low-precision linear displacement mechanism to obtain high-precision angle measurement, and can achieve an accuracy on the order of seconds. Attached Figure Description

[0053] Figure 1 This is a diagram of the equal-inclination interference device for dual-wavelength light source illumination with minute wavelength difference according to the present invention;

[0054] Figure 2 This is an equal-inclination interference pattern of dual-wavelength light source illumination with minute wavelength difference according to the present invention;

[0055] Figure 3 This is a schematic diagram of the micro-wavelength difference dual-wavelength light source equal inclination interferometry angle measurement device of the present invention;

[0056] Figure 4 This is a schematic diagram illustrating the calculation of the optical path of reflection caused by the tilting movement of the plane mirror in this invention.

[0057] Figure 5 This is a physical diagram of the plane mirror tilting linear movement measuring mechanism device of the present invention;

[0058] Figure 6 This is a schematic diagram of eight measurement scenarios for the angle measurement method of this invention.

[0059] In the figure: 1. Dual-wavelength light source with small wavelength difference; 2. Frosted glass screen; 3. Cubic beam splitter prism; 4. Reference beam reflector; 5. Test beam reflector; 6. CCD camera; 7. Coarse adjustment translation stage; 8. First rotary stage; 9. Linear translation stage; 10. Second rotary stage; 11. Planar reflector frame. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0061] Example 1:

[0062] See attached document Figures 1-6 An angle measurement method and apparatus based on dual-wavelength interference with a small wavelength difference includes the following steps:

[0063] S1. A dual-wavelength extended light source with a small wavelength difference is used to generate equal-inclination interference fringes through a Michelson interferometer;

[0064] S2. Using an adjustable tilting linear movement mechanism, the plane mirror of the test beam is moved along the tilting direction.

[0065] S3. The tilt angle is indirectly measured by measuring the distance the plane mirror moves when the interference fringes are most blurred in two consecutive instances during the tilting process.

[0066] S4. Calculate the measured angle based on the difference between the two inclination angles;

[0067] Based on the principle that the optical path difference between the test beam and the reference beam of a dual-wavelength extended light source with a small wavelength difference alternates between blurred and clear equal-inclination interference fringes during continuous change, an adjustable tilting linear movement mechanism is used to move the tilting direction of the plane mirror of the test beam. The tilt angles of different tilting directions are measured twice, and the difference between the two tilt angles is the measured angle.

[0068] The method for measuring angles is simple and easy to implement, and the device is convenient to install and debug. It is suitable for high-precision angle measurement of small angles and angles around 180°. It uses the fuzziness or clarity of the interferogram as the basis for judgment and positioning. It is sensitive and accurate. It is also suitable for automated analysis and processing of computer image data. It uses a low-precision linear displacement mechanism to obtain high-precision angle measurement, which can achieve an accuracy on the order of seconds.

[0069] See attached document Figure 1 The light emitted by the dual-wavelength light source 1 with a small wavelength difference becomes an extended light source after passing through the frosted glass screen 2. It is then separated into two coherent beams by the cubic beam splitter prism 3. The beam reflected upward is the reference beam, and the beam that passes directly through the cubic beam splitter prism 3 is the test beam.

[0070] The reference beam is reflected by the reference beam mirror 4 and returns along the original path, then passes through the cubic beam splitter prism 3 to reach the CCD camera 6.

[0071] The test beam is reflected by the test beam reflector 5 and returns along the original path. It is then reflected by the cubic beam splitter prism 3 and reaches the CCD camera 6 in the same way.

[0072] The CCD camera 6 can be used to focus at infinity to observe the equal-inclination interference fringes of the extended light source, or the equal-inclination interference fringes can be observed directly by focusing at infinity with the naked eye.

[0073] By adjusting the test beam reflector 5 and moving it continuously along the direction of the main ray of the beam, the alternating changes of blurred and clear periodic changes in the equal inclination interference fringes can be observed.

[0074] Because they are dual-wavelength extended light sources with a small wavelength difference, they produce two sets of equal-inclination interference fringes superimposed together. Therefore, the observed interference fringes will periodically show the situation where the fringes are most blurred (the contrast of the interference fringes is the lowest) and clear.

[0075] Let the two wavelengths of a dual-wavelength light source with a small wavelength difference be λ1 and λ2, then the wavelength difference is Δλ = λ2 - λ1;

[0076] During the periodic occurrence of the most blurred interference fringes, the period of the corresponding distance that the test beam mirror 5 moves along the principal ray in the test beam path is Δe = e2 - e1, where e1 and e2 are the positions of the test beam mirror 5 when the interference fringes are most blurred in two adjacent periods.

[0077] According to the principles of physical optics, the calculation formula is as follows:

[0078]

[0079] Considering the small wavelength difference between the two wavelengths, the average wavelength can be approximated as squared. Substituting into formula (1), we get:

[0080]

[0081] Figure 2 The image depicts the alternating blurring and sharpening of equal-inclination interference fringes from a dual-wavelength light source with a small wavelength difference, as the test beam reflector 5 moves along the principal ray direction. Figure 2 In the middle, the second and sixth images from left to right are the two most blurred cases, corresponding to the distance period of the test beam reflector 5 moving along the direction of the main ray of the test optical path.

[0082] See attached document Figure 1-4 By adjusting the test beam reflector 5, it is moved along the tilt direction of the principal ray, and the reflecting surface of the test beam reflector is still perpendicular to the principal ray of the beam;

[0083] In order to measure the angle, Figure 1 The test beam reflector 5 in the reference beam path, which was originally moved along the principal ray, is now moved along an inclined direction. The reflecting surface of the test beam reflector 5 remains perpendicular to the principal ray. Figure 3 As shown, it can be seen that as long as the test beam reflector 5 is wide enough, its reflection effect does not change, but the distance it moves along the direction of the principal ray is indirectly caused by the distance it moves along the tilt direction.

[0084] like Figure 4As shown, let α be the angle between the tilting direction of the test beam reflector 5 and the mirror surface. This angle is also the angle between the actual movement direction and the direction perpendicular to the principal ray; this angle is called the tilt angle. Let c be the displacement of the test beam reflector 5 along the tilting direction, and b be the distance the reflector moves along the principal ray direction. The calculation formula is:

[0085] b = c × sinα (3)

[0086] In the formula, the displacement c in the tilt direction is the displacement measured directly, and the displacement b of the test beam reflector 5 along the direction of the principal ray is the displacement measured indirectly.

[0087] When indirectly measuring the displacement of the reflector surface along the principal ray direction by tilting the test beam reflector 5, Δe in equation (1) or (2) should be replaced with Δe×sinα. In this case, Δe is the distance moved by the test beam reflector 5 when the interference fringes are most blurred (lowest contrast) in two consecutive measurements along the tilt direction, and α is the tilt angle of the moving direction; then equation (2) is modified as follows:

[0088]

[0089] The method for measuring the angle in this invention involves selecting a suitable light source with a known small wavelength difference, λ1 and λ2, and indirectly measuring the tilt angle α by measuring the distance Δe that the test beam reflector 5 moves along the tilt direction of the tilt angle α when the interference fringes are most blurred (contrast is lowest) for two consecutive times. Therefore, equation (4) is transformed into:

[0090]

[0091] The inclination angle is obtained from equation (5):

[0092]

[0093] The tilt angle measurement error caused by a single measurement is obtained by mathematical differentiation from equation (6):

[0094]

[0095] The tilt angle measurement error caused by a single measurement can also be obtained by mathematical differentiation from equation (5):

[0096]

[0097] As can be seen from equation (8), during measurement, the smaller the tilt angle position value, that is, the closer it is to the 0° starting angle position, the greater the distance Δe that it moves when the two consecutive fringes are most blurred, and the smaller the angle position measurement error caused; therefore, the closer the starting angle position is to 0° during measurement, the better.

[0098] Example 2: The difference from Example 1 is that;

[0099] Assume the reading accuracy of the moving measuring scale of the test beam reflector 5 is 1 μm. The nominal wavelengths of the yellow double lines of the sodium lamp are: λ1 = 588.99 nm, λ2 = 589.59 nm, wavelength difference Δλ = 0.60 nm, and average wavelength... =589.29nm. Taking δ(Δe) = 2μm, the error caused by different tilt angle measurements is calculated according to equation (8), as shown in Table 1.

[0100] Table 1. Accuracy of Angular Position Measurement

[0101] Angular position α 1° 3° 5° 10° 15° 20° 25° 30° 35° 40° Angular position error δα 0.5″ 3.9″ 10.9″ 43.7″ 1.7′ 3.0′ 4.7′ 6.9′ 9.6′ 12.9′ Angular position α 45° 50° 55° 60° 65° 70° 75° 80° 85° 90° Angular position error |δα| 16.8′ 21.7′ 27.8′ 35.7′ 46.2′ 61.4′ 85.7′ 132.7′ 270.6′ ∞

[0102] As shown in Table 1, the larger the inclination angle, the greater the measurement error. When the inclination angle α < 5°, the error of a single measurement |δα| < 11″; when the inclination angle α < 15°, the error of a single measurement |δα| < 2′. After that, the error increases sharply with the increase of the inclination angle, reaching infinity when the inclination angle α = 90°. This indicates that measurements should not be taken at or near the inclination angle of 90°.

[0103] Example 3: The difference from Example 1 is that;

[0104] See attached document Figure 6 The angle represented by equation (6) has a starting angle position of 0°. Figure 3 The tangent direction of the test beam reflector 5 is perpendicular to the principal ray of the test beam. When the test beam reflector 5 moves along this direction, theoretically the interference fringes will not change. The distance moved when the interference fringes are most blurred for two consecutive times is infinite. It is very difficult to accurately find the 0° starting angle position during measurement and debugging operations. That is, the systematic error caused by the uncertainty of the 0° angle position cannot be overcome.

[0105] On the other hand, the error is only sufficiently small when measuring angular positions near 0° and 180°. Therefore, a starting angular position can be chosen near the 0° position, and a second angular position near either the 0° or 180° position can be chosen as the ending angular position. Figure 6 The illustration in the image;

[0106] Figure 6 The vertical line AB represents either a 0° or 180° angle position. The direction of tilting movement is oriented towards the radius of the circle, and the corresponding tilt angle α1 or α2 is the angle between the radius direction and the vertical line AB. The measured angle is the angle rotated counterclockwise from the initial angle position α1 to the final angle position α2 (except for the fourth case, which is clockwise). There are a total of 8 measurement cases.

[0107] Let the measured angle be denoted as α. 1-2 From the appendix Figure 6 As can be seen, the formulas for calculating the measured angle vary slightly under different measurement conditions. Table 2 shows the formulas corresponding to the appendix. Figure 6 Formulas for calculating the measured angle under various measurement conditions.

[0108] Table 2 Formulas for calculating measurement angles under various measurement scenarios

[0109]

[0110] In the above calculation formulas for various measurement scenarios, α1 and α2 are obtained by modifying formula (6):

[0111]

[0112] From equation (7), the measurement error caused by a single angle measurement can be obtained as follows:

[0113]

[0114] In equations (9), (10), and (11) above, Δe1 is the distance moved by the test beam reflector 5 during the movement of the test beam reflector 5 when the interference fringes are most blurred for two consecutive times during the movement of the test beam reflector 5 when the test beam reflector 5 is ....

[0115] See attached document Figure 3 and Figure 6 An apparatus for implementing an angle measurement method based on dual-wavelength interferometry with a small wavelength difference, comprising:

[0116] A dual-wavelength light source with a slight wavelength difference;

[0117] The Michelson interferometer includes a frosted glass screen 2, a cubic beam splitter prism 3, a reference beam mirror 4, and a test beam mirror 5.

[0118] CCD camera 6, used to observe equal-inclination interference fringes;

[0119] The tilting linear movement mechanism is used to adjust the tilting movement direction of the test beam reflector 5;

[0120] The displacement measuring device, contained within the tilting linear movement mechanism, is used to measure the distance the test beam reflector 5 moves along the tilting direction.

[0121] The tilting linear movement mechanism includes: a coarse adjustment translation stage 7, a first rotary stage 8, a linear translation stage 9, a second rotary stage 10, and a plane mirror frame 11;

[0122] The tilting direction of the test beam reflector 5 is adjusted by rotating the first rotating stage 8 and the second rotating stage 10, and the tilting displacement of the test beam reflector 5 is measured by moving the linear translation stage 9.

[0123] Between the first rotary table 8 and the second rotary table 10, there is a single-axis linear translation stage 9, and a plane mirror holder 11 with a test beam reflector 5 is mounted on top of the second rotary table 10.

[0124] The first rotary table 8 and the second rotary table 10 can rotate independently around their respective central axes within a 360° range in the horizontal plane. The middle single-axis linear translation stage 9 can drive the upper second rotary table 10 and its upper plane reflector to move linearly together. In conjunction with the rotation of the lower first rotary table 8, tilt direction adjustment and displacement measurement can be achieved.

[0125] The plane mirror mount 11 on which the test beam reflector 5 is located can be adjusted in height and pitch. The entire device can also be mounted on the coarse adjustment translation stage 7 at the bottom, which can move along the direction of the main ray of the test beam, to facilitate coarse adjustment of the entire device over a large distance.

[0126] Specifically, Figure 5 In the middle, from bottom to top, are the coarse adjustment translation stage 7, the first rotary stage 8, the linear translation stage 9, the second rotary stage 10, and the plane mirror frame 11.

[0127] The first rotating platform 8 and the second rotating platform 10 are each composed of their own stationary base and rotatable surface, and the surface can rotate relative to the base around their respective central axis within a range of 360°.

[0128] The linear translation stage 9 consists of a stationary base and a movable surface. The surface can move parallel to the base along the horizontal inner center line, and the distance or position value of the movement can be read.

[0129] The test beam reflector 5 is mounted on the plane reflector frame 11, which is fixedly connected to the column. The plane reflector frame 11 can be tilted to adjust the plane reflector surface in the vertical plane. The column can be raised and lowered to adjust the height of the plane mirror.

[0130] The base of the first rotary stage 8 is fixedly mounted on the experimental workbench, or it can be mounted on the coarse adjustment translation stage 7 (shown in the diagram, mounted on the coarse adjustment translation stage 7) for easy coarse adjustment but not for measurement. Its rotatable platform is fixedly connected to the base of the linear translation stage 9. Rotating the rotatable platform of the first rotary stage 8 adjusts the tilting direction of the linear translation stage 9. The movable linear movement platform of the linear translation stage 9 is fixedly connected to the base of the second rotary stage 10. Pushing the platform of the linear translation stage 9 causes the second rotary stage 10 to move linearly along with it. The mirror frame column containing the plane mirror holder 11 is fixedly connected to the platform of the second rotary stage 10. Rotating the platform of the second rotary stage 10 allows the plane mirror holder 11 to rotate in the horizontal plane, causing the principal ray in the horizontal plane to be reflected back along its original path (the normal of the mirror coincides with the principal ray).

[0131] To move the plane mirror holder 11 in the horizontal plane along a direction inclined to the principal ray, and to reflect the principal ray back along its original path using the test beam reflector 5 on the plane mirror holder 11, the method is as follows: First, rotate the platform of the first rotary stage 8 so that the movement direction of the linear translation stage 9 on the platform is inclined to the direction of the principal ray, and then lock the platform to stop rotating. At this time, the movement direction of the linear translation stage 9 is not perpendicular to the principal ray, but has an angle α relative to the perpendicular direction of the principal ray. Then, rotate the platform of the second rotary stage 10 so that the test beam reflector 5 on the plane mirror holder 11 on the platform reflects the principal ray back along its original path, and then lock the platform to stop rotating. Thus, the movable platform of the linear translation stage 9 moves linearly in the direction of the angle α, and the position and distance can be measured. (Reference) Figure 3 and Figure 4 As shown.

[0132] The debugging and measurement process includes the following steps:

[0133] Step 1, according to Figure 3 Set up the Michelson interferometer with the following components: a dual-wavelength light source with small wavelength difference 1, a frosted glass screen 2, a cubic beam splitter prism 3, a reference beam reflector 4, and a test beam reflector 5. The test beam reflector 5 is installed... Figure 5 The plane mirror mount 11 in the tilting linear motion measuring mechanism is shown. After adjusting the height and coaxiality of each optical component using conventional optical adjustment methods, the translation stage 7 is coarsely adjusted. After observing the equal-inclination interference fringes with the naked eye, the CCD camera 6 with a lens is then installed. The CCD camera 6 receives the image signal of the equal-inclination interference fringes and transmits it to the computer for display.

[0134] Step Two, Reference Figure 5Rotate the first rotary stage 8 so that the linear translation stage 9 moves in the direction of the starting angle α1 of the measured angle. Rotate the second rotary stage 10 so that the test beam reflector 5 returns to the position where the equal-inclination interference fringes can be observed. Move the linear translation stage 9 to move the test beam reflector 5, observe the periodic changes in the blurring and sharpness of the equal-inclination interference fringes, and record the position values ​​e1 and e1' of the difference in blurring degree between two consecutive interference fringes. The distance moved when the blurring degree of the interference fringes differs between two consecutive interference fringes is Δe1 = e1' - e1.

[0135] Third, rotate the first rotary stage 8 for the second time, so that the linear translation stage 9 moves in the direction of the final angle α2 of the measured angle. Rotate the second rotary stage 10 again, so that the test beam reflector 5 returns to the position where the equal-inclination interference fringes can be observed. Move the linear translation stage 9 to move the test beam reflector 5, observe the periodic changes in the blurring and sharpness of the equal-inclination interference fringes, and record the position values ​​e2 and e2' of the extreme difference in the blurring degree of the interference fringes between two consecutive tests. The distance moved when the blurring degree of the interference fringes is at its extreme difference between two consecutive tests is Δe2 = e2' - e2.

[0136] Fourth step: Calculate the measurement results. Substitute the measurement results Δe1 and Δe2 from the second and third steps into equations (9) and (10) respectively to calculate the initial and final angle positions α1 and α2.

[0137] Depending on whether the selected starting angle position and ending angle position are near 0° or 180°, or to the left or right, select from Table 2 (and...). Figure 6 The corresponding formula for calculating the measured angle is used to calculate the measured angle value α. 1-2 ;

[0138] Based on the single measurement accuracy δ(Δe1) and δ(Δe2) of the linear translation stage 9 used, substitute them into equation (11) to calculate the measurement angle α. 1-2 The error is calculated. If the direct measurement involves multiple measurements, the corresponding experimental data processing method should be used to calculate and process the data.

[0139] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An angle measurement method based on dual-wavelength interference with a small wavelength difference, characterized in that, Includes the following steps: S1. A dual-wavelength extended light source with a small wavelength difference is used to generate equal-inclination interference fringes through a Michelson interferometer; S2. Using an adjustable tilting linear movement mechanism, the plane mirror of the test beam is moved along the tilting direction. S3. The tilt angle is indirectly measured by measuring the distance the plane mirror moves when the interference fringes are most blurred in two consecutive instances during the tilting process. S4. Based on the inclination angles measured twice and the circumstances of the two inclination angle measurements, select different angle calculation formulas to calculate the measured angles.

2. The angle measurement method based on dual-wavelength interference with a small wavelength difference according to claim 1, characterized in that: The light emitted by the dual-wavelength light source with a small wavelength difference becomes an extended light source after passing through the frosted glass screen. It is then separated into two coherent beams by a cubic beam splitter. The beam reflected upward is the reference beam, and the beam that passes directly through the cubic beam splitter is the test beam. The reference beam is reflected by the reference beam mirror and returns along the original path, then passes through the cubic beam splitter to reach the CCD camera; The test beam is reflected by the test beam mirror and returns along the original path. It is then reflected by the cubic beam splitter prism and reaches the CCD camera in the same way. A CCD camera can be used to focus on an extended light source at infinity to observe equal-inclination interference fringes, or the naked eye can be used to directly focus on an extended light source at infinity to observe equal-inclination interference fringes.

3. The angle measurement method based on dual-wavelength interference with a small wavelength difference according to claim 2, characterized in that: By adjusting the test beam reflector, it is moved along the tilt direction of the principal ray, and the reflecting surface of the test beam reflector is perpendicular to the principal ray; Let the angle between the tilting direction of the test beam reflector and the mirror surface be θ. Let the displacement of the test beam reflector along the tilt direction be... c Then the distance the reflecting surface moves along the direction of the principal ray is b The calculation formula is as follows: （3） In the formula, the displacement in the tilt direction c It is a directly measured displacement, the displacement of the test beam reflector surface along the direction of the principal ray. b It is an indirect measurement of displacement.

4. The angle measurement method based on dual-wavelength interference with a small wavelength difference according to claim 3, characterized in that: When measuring indirectly by tilting and moving the test beam reflector, let's assume... It is the distance the test beam reflector moves when the fringes are most blurred in two consecutive measurements along the tilt direction. It is the tilt angle in the direction of movement; and let the two wavelengths of the dual-wavelength light source with a small wavelength difference be respectively... and Then the wavelength difference is Considering the small wavelength difference between the two wavelengths, the average wavelength can be approximated as squared. Then we have the formula: （4） Select a suitable dual-wavelength pair with a known small wavelength difference. and The light source was used to measure the angle along the reflector of the test beam when the interference fringes were most blurred in two consecutive tests. The distance moved in the direction of tilt The tilt angle was measured indirectly. Therefore, equation (4) is transformed into: （5） The inclination angle is obtained from equation (5): （6） From equation (6), through mathematical differentiation, the tilt angle measurement error caused by a single measurement is obtained as follows: （7）。 5. The angle measurement method based on dual-wavelength interference with a small wavelength difference according to claim 4, characterized in that: From equation (5), the tilt angle measurement error caused by a single measurement can also be obtained through mathematical differentiation: （8） As can be seen from equation (8), during measurement, the smaller the tilt angle value, that is, the closer it is to the 0° starting angle position, the greater the distance moved when the fringes are most blurred in two consecutive measurements. The larger the value, the smaller the angular position measurement error.

6. An apparatus for implementing the angle measurement method based on dual-wavelength interference with a small wavelength difference as described in any one of claims 1-5, characterized in that, include: A dual-wavelength extended light source with a small wavelength difference; A Michelson interferometer, comprising a frosted glass screen, a cubic beam splitter prism, a reference beam mirror, and a test beam mirror; A CCD camera was used to observe equal-inclination interference fringes. The tilting linear movement mechanism is used to adjust the tilting direction of the test beam reflector; A displacement measuring device used to measure the distance the test beam reflector moves along the tilt direction.

7. The apparatus for angle measurement based on dual-wavelength interference with a small wavelength difference according to claim 6, characterized in that: The tilting linear movement mechanism includes a coarse adjustment translation stage, a first rotary stage, a linear translation stage, a second rotary stage, and a plane mirror frame; The tilt direction of the test beam reflector is adjusted by rotating the first and second rotary tables, and the tilt displacement of the test beam reflector is measured by moving the linear translation stage.

8. The apparatus for angle measurement based on dual-wavelength interference with a small wavelength difference according to claim 7, characterized in that: The first and second rotary tables each consist of a fixed base and a rotatable surface, and the surface can rotate 360° relative to the base around its central axis. The linear translation stage consists of a stationary base and a movable surface. The surface moves parallel to the centerline relative to the base, and the distance or position of the movement is read.

9. The apparatus for angle measurement based on dual-wavelength interference with a small wavelength difference according to claim 7, characterized in that: The test beam reflector is mounted on a plane reflector frame, which is fixedly connected to a column. The plane reflector frame is used to adjust the pitch of the test beam reflector relative to the vertical plane, and the column is used to adjust the height of the test beam reflector.

Images