Miniaturized laser interferometer real-time distance measuring device and method based on point-by-point calculation

Abstract

The invention discloses a small laser interferometer real-time distance measuring device and method based on point-by-point calculation. The device comprises a light source, an interference light path, a photoelectric detector and a high-speed acquisition card. An interference light path adopts a half-inch small-size optical element, a detection end adopts millimeter-level photoelectric sensing surfaces which are compactly and densely arranged, and the whole device is small in size and light in weight. Firstly, an interference signal is received by a photoelectric detector; converting into an electric signal, carrying out point-by-point differential processing on a series of interference signals acquired by a high-speed acquisition card, and solving to obtain the phase of each sampling point; the displacement difference of the adjacent sampling points is obtained through phase difference demodulation of the two sampling points; finally, the displacement of each sampling point is accumulated and output in real time, and nanoscale precision displacement measurement is achieved. In order to solve the problem of overlong calculation time caused by point-by-point calculation, parallel processing of collection and calculation is adopted, simple operation such as addition and subtraction is only relied on, and the calculation process is simple and efficient. The device is compact in structure, and the displacement reduction method is high-speed and accurate.

Description

Technical Field

[0001] The invention belongs to the field of optical detection, and in particular relates to a miniaturized laser interferometer real-time distance measurement device and method based on point-by-point calculation. Background Art

[0002] Laser interferometry is a high-precision technology for distance measurement based on the interference phenomenon of light. The basic principle of laser interferometry is to use the interference phenomenon caused by the overlap of two light waves with a fixed phase difference, the same frequency and vibration direction. When the optical path difference of the two light waves changes, their interference fringes will also change accordingly, thereby reflecting the displacement information of the object being measured. Laser interferometry is based on the laser wavelength and has very high measurement accuracy. At the same time, laser interferometry uses a non-contact measurement method to avoid the errors and damage that may be caused by traditional contact measurement. This non-contact measurement method not only improves the accuracy of the measurement, but is also suitable for some occasions where direct contact measurement is not possible.

[0003] However, laser interferometer distance measurement requires the installation of both the reference mirror and the test mirror, thus requiring a larger installation space. This limits its application in some compact or narrow spaces to a certain extent. Laser interferometer distance measurement is very sensitive to disturbances, such as vibrations caused by changes in cutting forces, which may affect its measurement accuracy. Therefore, special attention should be paid to avoiding or reducing disturbance factors when using it.

[0004] In his article “Research on Signal Processing and Measurement Error Compensation Methods of Semiconductor Single-Frequency Laser Interferometer”, Xie Bo used a 635nm semiconductor single-frequency laser for ranging, but did not take into account the influence of the unstable wavelength of the conductor laser on the interference displacement accuracy. At the same time, the entire ranging device was large in size and had few applicable occasions.

[0005] Traditional phase demodulation involves unwrapping operations, which are complex, computationally intensive, and slow. Summary of the invention

[0006] The present invention proposes a miniaturized laser interferometer real-time distance measurement device and method based on point-by-point calculation, which solves the problems of miniaturization and portability of the laser interferometer and high-precision real-time distance measurement. At the same time, it only relies on simple operations such as addition and subtraction, and the calculation process is concise and efficient, thereby improving the calculation speed.

[0007] The technical solution to realize the present invention is: a miniaturized laser interferometer real-time ranging device based on point-by-point calculation, including a frequency-stabilized HeNe laser, an interference optical path, a high-speed single-point photoelectric detector, and a high-speed signal acquisition card; frequency-stable linearly polarized light emitted by the frequency-stabilized HeNe laser is incident on the interference optical path, and four interference linear polarized lights are formed after passing through the interference optical path. The four interference linear polarized lights are respectively received by four high-speed single-point photoelectric detectors to obtain four interference signals; the four high-speed single-point photoelectric detectors are respectively connected to the high-speed signal acquisition card, and the high-speed signal acquisition card transmits the four interference signals to a computer for processing.

[0008] A real-time distance measurement method of a miniaturized laser interferometer based on point-by-point calculation, using the above device, the steps are as follows:

[0009] Step 1, each of the four pairs of light emitted in the interference light path interferes; the third transmitted light is received by the first photodetector to obtain the first interference signal I1; the third reflected light is received by the second photodetector to obtain the second interference signal I2; the second transmitted light is received by the third photodetector to obtain the third interference signal I3; the second reflected light is received by the fourth photodetector to obtain the fourth interference signal I4; thereby, four interference signals with phases differing by 90° are obtained.

[0010] Step 2: Use a four-channel high-speed acquisition card to collect four interference signals in real time and send them to the computer.

[0011] Step 3: The computer performs differential operation on the signal of each acquisition point to obtain the two orthogonal interference signals I at the first moment. sin_1 and I cos_1 , and the two orthogonal interference signals I at the second moment sin_2 and I cos_2 .

[0012] Step 4: At this time, there is a slight phase shift between the two orthogonal signals. The two orthogonal signals are corrected using a slight phase shift elimination method:

[0013] An inverse tangent operation is performed on the two orthogonal interference signals at the first moment to obtain the phase difference Δφ1 between the reference light path and the moving light path at the first moment; an inverse tangent operation is performed on the two orthogonal interference signals at the second moment to obtain the phase difference Δφ2 between the reference light path and the moving light path at the second moment.

[0014] Step 5: Use the phase difference information to restore the displacement.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] (1) Compared with other interferometers, the distance measuring device proposed in the present invention is small in size (the size of the entire mounting plate is less than 120 mm × 100 mm × 40 mm), convenient and portable, and suitable for a variety of measurement environments.

[0017] (2) Taking advantage of the single-point high-speed photoelectric detector and high-speed acquisition card, a point-by-point calculation method is proposed to achieve high-speed and high-precision real-time ranging. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the real-time distance measurement method of the present invention.

[0019] Figure 2 This is the interference optical path diagram of the distance measurement of the present invention. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0021] In view of the defect of large structural volume of laser interferometer ranging devices, the present invention proposes for the first time a miniaturized laser interferometer real-time ranging device and method based on point-by-point calculation, which is suitable for field applications and mobile measurement tasks of high-precision measurements that need to be efficiently operated in a small space, effectively reducing the volume of the device and realizing high-precision real-time ranging.

[0022] Combination Figure 1 and Figure 2 A miniaturized laser interferometer real-time distance measurement device based on point-by-point calculation includes a frequency-stabilized HeNe laser, an interference optical path, a high-speed single-point photoelectric detector, and a high-speed signal acquisition card; frequency-stable linearly polarized light emitted by the frequency-stabilized HeNe laser is incident on the interference optical path, and four interference linear polarized lights are formed after passing through the interference optical path. The four interference linear polarized lights are respectively received by four high-speed single-point photoelectric detectors to obtain four interference signals; the four high-speed single-point photoelectric detectors are respectively connected to the high-speed signal acquisition card, and the high-speed signal acquisition card transmits the four interference signals to a computer for processing.

[0023] The interference optical path includes a first polarization beam splitter prism 1, a first quarter wave plate 2, a reference corner cube prism 3, a second quarter wave plate 4, a moving corner cube prism 5, a non-polarization beam splitter prism 6, a third quarter wave plate 7, a second polarization beam splitter prism 8, a first half wave plate 9, and a third polarization beam splitter prism 10.

[0024] The reference corner cube prism 3 , the first quarter wave plate 2 , the first polarization beam splitter prism 1 , the non-polarization beam splitter prism 6 , the first half wave plate 9 , the third polarization beam splitter prism 10 , and the first photodetector 11 are arranged in sequence on the first optical path.

[0025] The first polarization beam splitter prism 1, the second quarter wave plate 4, and the moving corner cube prism 5 are sequentially arranged on the second optical path.

[0026] The second optical path is sequentially arranged with a non-polarization beam splitter prism 6 , a third quarter wave plate 7 , a second polarization beam splitter prism 8 , and a third photodetector 13 .

[0027] The second photodetector 12 is located in the reflected light path of the third polarization beam splitter prism 10 , and the fourth photodetector 14 is located in the reflected light path of the second polarization beam splitter prism 8 .

[0028] The first optical path is perpendicular to the second optical path and the third optical path;

[0029] The second optical path and the third optical path are parallel;

[0030] In the interference optical path, the linearly polarized light emitted by the frequency-stabilized HeNe laser and collimated by the fiber collimator is incident on the first polarization beam splitter prism 1. The light beam is reflected and transmitted on the beam splitting surface of the first polarization beam splitter prism 1 and is divided into two beams of S polarized light and P polarized light with polarization directions perpendicular to each other.

[0031] The S-polarized light reflected by the first polarization beam splitter prism 1 is incident on the first quarter-wave plate 2, and is changed from linearly polarized light to circularly polarized light after passing through the first quarter-wave plate 2, and is emitted to the reference corner cube prism 3. The light reflected by the reference corner cube prism 3 is changed from circularly polarized light back to linearly polarized light after passing through the first quarter-wave plate 2 again, and is incident on the first polarization beam splitter prism 1.

[0032] The P-polarized light transmitted through the first polarization beam splitter prism 1 is incident on the second quarter-wave plate 4, and is changed from linearly polarized light to circularly polarized light after passing through the second quarter-wave plate 4, and is emitted to the moving corner cube prism 5. The light reflected by the moving corner cube prism 5 is changed from circularly polarized light back to linearly polarized light after passing through the second quarter-wave plate 4 again, and is incident on the first polarization beam splitter prism 1.

[0033] At this time, the polarization directions of the two linearly polarized lights have changed by 90°, but the polarization directions are still perpendicular to each other;

[0034] Two beams of linearly polarized light with polarization directions perpendicular to each other emitted from the first polarization beam splitter prism 1 are reflected and transmitted on the beam splitting surface of the non-polarization beam splitter prism 6 to obtain a first reflected light and a first transmitted light;

[0035] After the first reflected light passes through the third quarter-wave plate 7, the polarization direction is changed from two beams of linear polarized light with polarization directions perpendicular to each other to two beams of circular polarized light with opposite rotation directions and phase delay of 90°; after the two beams of circular polarized light are transmitted and reflected on the splitting surface of the second polarization beam splitter prism 8, a second transmitted light and a second reflected light are obtained, and the second transmitted light and the second reflected light are two pairs of linear polarized light, and each pair of linear polarized light interferes;

[0036] After the first transmitted light passes through the first half wave plate 9, the polarization direction changes, and the two beams of linear polarized light with polarization directions perpendicular to each other become two beams of circular polarized light with opposite rotation directions and phase delay of 180°; after the two beams of circular polarized light are transmitted and reflected on the splitting surface of the third polarization splitting prism 10, a third transmitted light and a third reflected light are obtained, and the third transmitted light and the third reflected light are two pairs of linear polarized light, and each pair of linear polarized light interferes; each pair of the four pairs of linear polarized light emitted from the interference light path interferes;

[0037] The four pairs of linearly polarized lights are received by the first photodetector 11 , the second photodetector 12 , the first photodetector 13 , and the fourth photodetector 14 , respectively, to obtain four interference signals with phases differing by 90° in sequence.

[0038] The interference optical path has a compact structure and small component size, and can be integrated into a small-sized mounting plate. The size of the entire mounting plate is less than 120 mm×100 mm×40 mm.

[0039] The frequency-stabilized HeNe laser outputs linearly polarized light with a stable frequency, and the wavelength fluctuation is less than 2pm.

[0040] The high-speed single-point photoelectric detector and high-speed signal acquisition card have a bandwidth of 10 MHz and a rise time of <11 ns; the high-speed signal acquisition card is a four-channel acquisition card, and the maximum sampling rate of each channel is 2MS / s, that is, each channel can collect 2×10 6 The signal of the sampling point.

[0041] A real-time distance measurement method of a miniaturized laser interferometer based on point-by-point calculation, the steps are as follows:

[0042] Step 1, each of the four pairs of light emitted in the interference light path interferes; the third transmitted light is received by the first photodetector 11 to obtain a first interference signal I1; the third reflected light is received by the second photodetector 12 to obtain a second interference signal I2; the second transmitted light is received by the third photodetector 13 to obtain a third interference signal I3; the second reflected light is received by the fourth photodetector 14 to obtain a fourth interference signal I4; thereby, four interference signals with phases differing by 90° are obtained;

[0043] Step 2: Use a four-channel high-speed acquisition card to collect four-way interference signals in real time and send them to a computer;

[0044] Step 3: The computer performs differential operation on the signal of each acquisition point, as follows:

[0045] The four interference signals collected in real time by the four-channel high-speed card at the first moment are differentially processed, the first interference signal collected at the first moment is differentially processed with the second interference signal, and the third interference signal collected at the first moment is differentially processed with the fourth interference signal, so as to obtain two orthogonal interference signals at the first moment:

[0046] I sin_1 =I 1_1 -I 2_1

[0047] I cos_1 =I 3_1 -I 4_1

[0048] Among them, I sin_1 is the sinusoidal signal at the first moment, I cos_1 is the cosine signal at the first moment, I 1_1 is the interference signal received by the first photodetector 11 at the first moment, I 2_1 is the interference signal received by the second photodetector 12 at the first moment, I 3_1 is the interference signal received by the third photodetector 13 at the first moment, I 4_1 is the interference signal received by the fourth photodetector 14 at the first moment.

[0049] The first interference signal collected at the second moment is differentially processed with the second interference signal, and the third interference signal collected at the second moment is differentially processed with the fourth interference signal, so as to obtain two orthogonal interference signals at the second moment:

[0050] I sin_2 =I 1_2 -I 2_2

[0051] I cos_2 =I 3_2 -I 4_2

[0052] Among them, I sin_2 is the sinusoidal signal at the second moment, I cos_2 is the cosine signal at the second moment, I 1_2 is the interference signal received by the first photodetector 11 at the second moment, I 2_2 is the interference signal received by the second photodetector 12 at the second moment, I 3_2 is the interference signal received by the third photodetector 13 at the second moment, I 4_2 is the interference signal received by the fourth photodetector 14 at the second moment.

[0053] Step 4: At this time, there is a slight phase shift between the two orthogonal signals. The slight phase shift elimination method can be used to correct the two orthogonal signals to improve the measurement accuracy, as follows:

[0054] Assume that the amplitude of the cosine signal is K cos , the amplitude of the sinusoidal signal is K sin The two orthogonal signals are:

[0055] I cos =K cos cosφ

[0056] I sin =K sin sin(φ+δ)

[0057] Among them, I cos is the cosine signal, I sin is a sinusoidal signal, φ is the phase, and δ is the small phase shift between the two orthogonal signals.

[0058] Introduce a quantity K sincos , which corresponds to I sin +I cos and the amplitude of the maximum value, that is:

[0059]

[0060] From this we can get:

[0061]

[0062] From this, the small phase shift δ can be calculated to eliminate the small phase shift δ between the orthogonal signals, that is:

[0063] I cos =K cos cosφ=I′ cos

[0064]

[0065] Among them, I′ cos is the corrected cosine signal, I′ sin is the modified sinusoidal signal, that is

[0066] I′ cos =I cos

[0067]

[0068] Using the above correction method, we can get the corrected orthogonal signal:

[0069] I′ sin_1 = sin(φ2_1 -φ 1_1 )

[0070] I′ cos_1 =cos(φ 2_1 -φ 1_1 )

[0071] I′ sin_2 = sin(φ 2_2 -φ 1_2 )

[0072] I′ cos_2 =cos(φ 2_2 -φ 1_2 )

[0073] Among them, φ 1_1 is the phase of the reference light path at the first moment, φ 2_1 is the phase of the moving light path at the first moment, φ 2_1 -φ 1_1 is the phase difference between the reference light path and the moving light path, also denoted as Δφ1; φ 1_2 is the phase of the reference light path at the second moment, φ 2_2 is the phase of the moving light path at the second moment, φ 2_2 -φ 1_2 It is the phase difference between the reference light path and the moving light path at the second moment, which can also be recorded as Δφ2.

[0074] An inverse tangent operation is performed on the two orthogonal interference signals at the first moment to obtain the phase difference Δφ1 between the reference light path and the moving light path at the first moment; an inverse tangent operation is performed on the two orthogonal interference signals at the second moment to obtain the phase difference Δφ2 between the reference light path and the moving light path at the second moment.

[0075] Step 5: Use the phase difference information to restore the displacement, as follows:

[0076] Get the phase difference information of two adjacent sampling points, and subtract the phase difference of the first moment from the phase difference of the second moment, that is:

[0077] Δφ2-Δφ1=φ 2_2 -φ 1_2 -φ 2_1 +φ 1_1

[0078] Since the reference corner cube 3 does not move, the reference path phase information does not change, that is:

[0079] Δφ2-Δφ1=φ 2_2 -φ 2_1

[0080] The phase difference information of the moving optical path of two adjacent sampling points is thus obtained and recorded as ΔΦ1;

[0081] From the relationship between the phase difference and the displacement, we can get the distance that the moving angle cone moves relative to the reference angle cone at the first moment and the second moment, that is, the displacement Δx1 of the moving angle cone between the first moment and the second moment, namely:

[0082]

[0083] Where, λ is the wavelength of HeNe laser;

[0084] By continuously calculating the phase difference between two adjacent sampling points, the displacement between two adjacent sampling points is obtained. The total displacement x of the moving angle cone can be obtained by accumulating the displacement between all two adjacent sampling points:

[0085]

[0086] Where Δx i is the displacement between the i+1th moment and the ith moment, φ 2_i+1 is the phase of the moving light path at the i+1th moment, φ 2_i is the phase of the moving light path at the i-th moment, and n represents the total number of sampling points.

[0087] Example 1: Application of miniaturized laser interferometer in high-speed dynamic measurement

[0088] In some application scenarios, the objects to be measured are often high-speed moving objects, such as in mechanical engineering, aerospace, automated production lines, etc. When dealing with high-speed dynamic measurements, traditional laser interferometers are prone to measurement errors or data delays due to frequent signal changes or fast target movement. Therefore, it is necessary to maintain high-precision measurements under high-speed dynamic conditions.

[0089] Device configuration: The device is consistent with the above claims, and the moving corner cube prism 5 is connected to the measurement object to maintain a consistent movement state.

[0090] ① The moving corner cube prism 5 is connected to the measurement object to keep the moving state consistent.

[0091] ② When the measured object starts to move, the moving corner cube prism 5 also starts to move simultaneously.

[0092] ③ As the moving corner cube prism 5 generates movement, four interference signals generated are received in real time by the first photodetector 11, the second photodetector 12, the first photodetector 13, and the fourth photodetector 14, and the high-speed signal acquisition card transmits the four interference signals to the computer for processing.

[0093] ④ The computer uses a miniaturized laser interferometer real-time ranging method based on point-by-point calculation to perform point-by-point differential calculation, orthogonal signal correction and displacement restoration on the signal.

[0094] ⑤Finally, the computer outputs the displacement information of the measured object in real time based on the calculation results.

Claims

1. A miniaturized laser interferometer real-time distance measurement device based on point-by-point calculation, characterized in that: It includes a frequency-stabilized HeNe laser, an interference optical path, a high-speed single-point photoelectric detector, and a high-speed signal acquisition card; the frequency-stable linearly polarized light emitted by the frequency-stabilized HeNe laser is incident on the interference optical path, and four interference linearly polarized lights are formed after passing through the interference optical path. The four interference linearly polarized lights are respectively received by four high-speed single-point photoelectric detectors to obtain four interference signals; the four high-speed single-point photoelectric detectors are respectively connected to the high-speed signal acquisition card, and the high-speed signal acquisition card transmits the four interference signals to a computer for processing.

2. The miniaturized laser interferometer real-time distance measurement device based on point-by-point calculation according to claim 1 is characterized in that: The interference optical path comprises a first polarization beam splitter prism (1), a first quarter wave plate (2), a reference corner cube prism (3), a second quarter wave plate (4), a moving corner cube prism (5), a non-polarization beam splitter prism (6), a third quarter wave plate (7), a second polarization beam splitter prism (8), a first half wave plate (9), and a third polarization beam splitter prism (10); In the interference optical path, linearly polarized light emitted by a frequency-stabilized HeNe laser and collimated by a fiber collimator is incident on a first polarization beam splitter prism (1), and the light beam is reflected and transmitted on the beam splitting surface of the first polarization beam splitter prism (1), and is split into two beams of S polarized light and P polarized light with polarization directions perpendicular to each other; The S-polarized light reflected by the first polarization beam splitter (1) is incident on the first quarter-wave plate (2), and after passing through the first quarter-wave plate (2), the linearly polarized light is changed into circularly polarized light, and then emitted to the reference corner cube prism (3). The light reflected by the reference corner cube prism (3) is again changed into linearly polarized light after passing through the first quarter-wave plate (2) and then incident on the first polarization beam splitter (1). The P-polarized light transmitted through the first polarization beam splitter (1) is incident on the second quarter-wave plate (4), and after passing through the second quarter-wave plate (4), it is converted from linearly polarized light to circularly polarized light, and then emitted to the moving corner cube prism (5). The light reflected by the moving corner cube prism (5) is converted from circularly polarized light back to linearly polarized light after passing through the second quarter-wave plate (4) again, and then is incident on the first polarization beam splitter (1); At this time, the polarization directions of the two linearly polarized lights have changed by 90°, but the polarization directions are still perpendicular to each other; Two beams of linearly polarized light with polarization directions perpendicular to each other emitted from the first polarization beam splitter prism (1) are reflected and transmitted on the beam splitting surface of the non-polarization beam splitter prism (6) to obtain first reflected light and first transmitted light; After the first reflected light passes through the third quarter-wave plate (7), the polarization direction is changed, and two beams of linear polarized light with polarization directions perpendicular to each other are transformed into two beams of circular polarized light with opposite rotation directions and phase delay of 90°; after the two beams of circular polarized light are transmitted and reflected on the splitting surface of the second polarization splitting prism (8), a second transmitted light and a second reflected light are obtained, and the second transmitted light and the second reflected light are two pairs of linear polarized light, and each pair of linear polarized light interferes; After the first transmitted light passes through the first half-wave plate (9), the polarization direction is changed, and two beams of linear polarized light with polarization directions perpendicular to each other are transformed into two beams of circular polarized light with rotation directions opposite to each other and phase delayed by 180 degrees; after the two beams of circular polarized light are transmitted and reflected on the splitting surface of the third polarization splitting prism (10), third transmitted light and third reflected light are obtained, and the third transmitted light and the third reflected light are two pairs of linear polarized light, and each pair of linear polarized light interferes; Each of the four pairs of light emitted from the interference light path interferes; the third transmitted light is received by the first photodetector (11), the third reflected light is received by the second photodetector (12), the second transmitted light is received by the third photodetector (13), and the second reflected light is received by the fourth photodetector (14), thereby obtaining four interference signals with phases that differ by 90 degrees in sequence.

3. The miniaturized laser interferometer real-time distance measurement device based on point-by-point calculation according to claim 2, characterized in that: The interference optical path has a compact structure and is integrated on the mounting plate. The size of the entire mounting plate is less than 120mm×100mm×40mm.

4. The miniaturized laser interferometer real-time distance measurement device based on point-by-point calculation according to claim 3 is characterized in that: The frequency-stabilized HeNe laser outputs linearly polarized light with a stable frequency and a wavelength fluctuation of less than 2pm.

5. The miniaturized laser interferometer real-time distance measurement device based on point-by-point calculation according to claim 4, characterized in that: The bandwidth of the high-speed single-point photodetector is 10MHz, and the rise time is less than 11ns. The high-speed signal acquisition card is a four-channel acquisition card, and the maximum sampling rate of each channel is 2MS / s, that is, each channel can collect 2×10 6 The signal of the sampling point.

6. A real-time distance measurement method of a miniaturized laser interferometer based on point-by-point calculation, characterized in that: Using the device described in any one of claims 1 to 5, the steps are as follows: Step 1: Each of the four pairs of light emitted in the interference light path interferes with each other; the third transmitted light is received by the first photodetector (11) to obtain a first interference signal I1; the third reflected light is received by the second photodetector (12) to obtain a second interference signal I2; the second transmitted light is received by the third photodetector (13) to obtain a third interference signal I3; the second reflected light is received by the fourth photodetector (14) to obtain a fourth interference signal I4; thereby, four interference signals with phases that differ by 90° are obtained; Step 2: Use a four-channel high-speed acquisition card to collect four-way interference signals in real time and send them to a computer; Step 3: The computer performs differential operation on the signal of each acquisition point to obtain the two orthogonal interference signals I at the first moment. sin_1 and I cos_1 , and the two orthogonal interference signals I at the second moment sin_2 and I cos_2 ; Step 4: At this time, there is a slight phase shift between the two orthogonal signals. The two orthogonal signals are corrected using a slight phase shift elimination method: Performing an inverse tangent operation on the two orthogonal interference signals at the first moment, the phase difference Δφ1 between the reference light path and the moving light path at the first moment is obtained; performing an inverse tangent operation on the two orthogonal interference signals at the second moment, the phase difference Δφ2 between the reference light path and the moving light path at the second moment is obtained; Step 5: Use the phase difference information to restore the displacement.

7. The method for real-time distance measurement using a miniaturized laser interferometer based on point-by-point calculation according to claim 6, characterized in that: In step 3, the computer performs differential operation on the signal of each acquisition point, as follows: The four interference signals collected in real time by the four-channel high-speed card at the first moment are differentially processed, the first interference signal collected at the first moment is differentially processed with the second interference signal, and the third interference signal collected at the first moment is differentially processed with the fourth interference signal, so as to obtain two orthogonal interference signals at the first moment: I sin_1 =I 1_1 -I 2_1 I cos_1 =I 3_1 -I 4_1 Among them, I sin_1 is the sinusoidal signal at the first moment, I cos_1 is the cosine signal at the first moment, I 1_1 is the interference signal received by the first photodetector (11) at the first moment, I 2_1 is the interference signal received by the second photodetector (12) at the first moment, I 3_1 is the interference signal received by the third photodetector (13) at the first moment, I 4_1 is the interference signal received by the fourth photodetector (14) at the first moment; The first interference signal collected at the second moment is differentially processed with the second interference signal, and the third interference signal collected at the second moment is differentially processed with the fourth interference signal, so as to obtain two orthogonal interference signals at the second moment: I sin_2 =I 1_2 -I 2_2 I cos_2 =I 3_2 -I 4_2 Among them, I sin_2 is the sinusoidal signal at the second moment, I cos_2 is the cosine signal at the second moment, I 1_2 is the interference signal received by the first photodetector (11) at the second moment, I 2_2 is the interference signal received by the second photodetector (12) at the second moment, I 3_2 is the interference signal received by the third photodetector (13) at the second moment, I 4_2 is the interference signal received by the fourth photodetector (14) at the second moment.

8. The method for real-time distance measurement using a miniaturized laser interferometer based on point-by-point calculation according to claim 7, characterized in that: In step 4, there is a slight phase shift between the two orthogonal signals. The two orthogonal signals are corrected by using a slight phase shift elimination method, as follows: Assume that the amplitude of the cosine signal is K cos , the amplitude of the sinusoidal signal is K sin ; The two orthogonal signals are: I cos =K cos cosφ I sin =K sin sin(φ+δ) Among them, I cos is the cosine signal, I sin is a sinusoidal signal, φ is the phase, and δ is the small phase shift between the two orthogonal signals; Introduce a quantity K sincos , which corresponds to I sin +I cos and the amplitude of the maximum value, that is: From this we get: From this, the small phase shift δ can be calculated to eliminate the small phase shift δ between the orthogonal signals, that is: I cos =K cos cosφ=I c ′ os Among them, I c ' os is the corrected cosine signal, I s ' in is the modified sinusoidal signal, that is I c ′ os =I cos Using the above correction method, the corrected orthogonal signal I is obtained. s ' in_1 ,I c ' os_1 ,I s ' in_2 ,I c ' os_2 : I s ′ in_1 =sin(φ 2_1 -f 1_1 ) I c ′ os_1 =cos(φ 2_1 -f 1_1 ) I s ′ in_2 =sin(φ 2_2 -f 1_2 ) I c ′ os_2 =cos(φ 2_2 -f 1_2 ) Among them, φ 1_1 is the phase of the reference light path at the first moment, φ 2_1 is the phase of the moving light path at the first moment, φ 2_1 -φ 1_1 is the phase difference between the reference light path and the moving light path, also denoted as Δφ1; φ 1_2 is the phase of the reference light path at the second moment, φ 2_2 is the phase of the moving light path at the second moment, φ 2_2 -φ 1_2 is the phase difference between the reference light path and the moving light path at the second moment, also recorded as Δφ2; An inverse tangent operation is performed on the two orthogonal interference signals at the first moment to obtain the phase difference Δφ1 between the reference light path and the moving light path at the first moment; an inverse tangent operation is performed on the two orthogonal interference signals at the second moment to obtain the phase difference Δφ2 between the reference light path and the moving light path at the second moment.

9. The method for real-time distance measurement using a miniaturized laser interferometer based on point-by-point calculation according to claim 6, characterized in that: In step 5, the phase difference information is used to restore the displacement, as follows: Get the phase difference information of two adjacent sampling points, and subtract the phase difference of the first moment from the phase difference of the second moment, that is: Δφ2-Δφ1=φ 2_2 -f 1_2 -f 2_1 +φ 1_1 , Since the reference corner cube (3) does not move, the reference path phase information does not change, that is: Δφ2-Δφ1=φ 2_2 -f 2_1 The phase difference information of the moving optical path of two adjacent sampling points is thus obtained and recorded as ΔΦ1; From the relationship between the phase difference and the displacement, we can get the distance that the moving angle cone moves relative to the reference angle cone at the first moment and the second moment, that is, the displacement Δx1 of the moving angle cone between the first moment and the second moment, namely: Where, λ is the wavelength of HeNe laser; By continuously calculating the phase difference between two adjacent sampling points, the displacement between two adjacent sampling points is obtained. The total displacement x of the moving angle cone can be obtained by accumulating the displacement between all two adjacent sampling points: Where Δx i is the displacement between the i+1th moment and the ith moment, φ 2_i+1 is the phase of the moving light path at the i+1th moment, φ 2_i is the phase of the moving light path at the i-th moment, and n represents the total number of sampling points.

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