A variable range high-resolution angular displacement measurement device and method

Abstract

The present invention relates to the field of angular displacement measurement technology, and more specifically, to a high-resolution angular displacement measurement device and method with a variable range. When the angle to be measured is small, the device is in a high-resolution mode, at which time the two light spots on the detector are superimposed and interfered, and the angular displacement is measured using the interference effect; when the angle to be measured is large, the device is in a large-range mode, at which time the two light spots on the detector are separated, and the angular displacement is measured using the optical lever effect. While achieving high-resolution angular displacement measurement, the present invention takes into account a larger range, and at the same time uses a periodic square wave modulation method to suppress low-frequency noise in the angle measuring device, and achieves two-dimensional angle measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of angular displacement measurement, and more specifically, to a variable range high-resolution angular displacement measurement device and method. Background Art

[0002] Angular displacement measurement technology is an important part of geometric measurement technology, and it is widely used and plays an important role in social development and production construction. There are many kinds of modern angle measurement methods, and the principles, accuracy, resolution, volume, etc. adopted are also different. According to their working principles, they can be divided into five categories: electrical methods, grating methods, photoelectric encoders, optical methods and electromagnetic methods. At present, the high-resolution angle measurement methods in the field of scientific research are mainly divided into photoelectric encoders, autocollimators and laser interferometry.

[0003] The photoelectric autocollimator uses the principle of optical self-collimation to convert the angular displacement measurement into the measurement of the change in the position of the positioning light spot. This method usually has a working range of the mrad order, but is limited by the performance of the area array image sensor and the light spot positioning algorithm, and the angular displacement measurement resolution is difficult to be better than 10nrad. The principle of laser interferometry is the interference effect, and it can be mainly divided into heterodyne interferometer and homodyne interferometer according to the optical path structure. The research team at the University of Washington used a new laser interferometer angle measurement method to convert the angular displacement measurement into the displacement measurement of the center of the superimposed light spot after the interference of two light spots. The angular displacement measurement resolution of this method is better than However, due to the interference principle, the distance between the two light spots cannot be too large, the range is smaller than that of the autocollimator, and the low-frequency noise is not ideal. At the same time, only the horizontal axis torsion angle of the target mirror can be measured. Summary of the invention

[0004] In order to overcome the above-mentioned defects in the prior art, the present invention provides a variable-range high-resolution angular displacement measurement device and method, which realizes high-resolution angular displacement measurement while taking into account a larger measurement range.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A variable range high-resolution angular displacement measuring device, comprising:

[0007] Light source module: including laser light source, fiber coupling mirror, polarization-maintaining fiber, and fiber collimator;

[0008] Optical element module: including a Faraday isolator, a beam splitter, a polarization beam splitter, a half-wave plate, a quarter-wave plate, a first reflector, a second reflector, a third reflector, a fourth reflector, a fifth reflector, and a target mirror;

[0009] Data acquisition module: including an area array image sensor and a data acquisition system connected to the area array image sensor for acquiring data from the area array image sensor;

[0010] The light beam is emitted by the laser light source, coupled by the polarization-maintaining fiber, and incident from the collimator to the optical element module. Then it passes through the Faraday isolator and the beam splitter, and the light beam is divided into two paths, clockwise and counterclockwise. The clockwise light beam passes through the fourth reflector, the fifth reflector, the third reflector, the polarization beam splitter, and the quarter wave plate in turn, and then hits the target mirror. After reflection, it passes through the quarter wave plate, the polarization beam splitter, the half wave plate, the second reflector, and the first reflector. The counterclockwise light beam passes through the first reflector, the second reflector, the half wave plate, the polarization beam splitter, and the quarter wave plate in turn, and then hits the target mirror. After reflection, it passes through the quarter wave plate, the polarization beam splitter, the third reflector, the fifth reflector, and the fourth reflector. Finally, the two light beams converge again after the beam splitter and hit the area array image sensor together. To reduce environmental disturbances, each module is located on an optical platform, and the center of each component is at the same level.

[0011] Furthermore, when the angle to be measured is small, the two light spots of the two light beams hitting the area array image sensor are superimposed and interfered; when the angle to be measured is large, the two light spots of the two light beams hitting the area array image sensor are separated.

[0012] According to the above technical means, the present invention provides a high-resolution angular displacement measurement device with a variable range, which is divided into a high-resolution mode and a large-range mode, combining the characteristics of high resolution and large range to the maximum extent, so as to perform efficient angular displacement measurement. When the angle to be measured is small, the device is in the high-resolution mode. At this time, the two light spots on the area array image sensor are superimposed and interfered, and the device uses the interference effect to measure the angular displacement; when the angle to be measured is large, the device is in the large-range mode. At this time, the two light spots on the area array image sensor are separated, and the device uses the optical lever effect to measure the angular displacement. The critical angle for switching between the two modes is different for different devices, and can be analyzed in combination with the shape and position of the light spot on the area array image sensor. The angular displacement measurement resolution level of the high-resolution mode can reach The angular displacement measurement range in the wide range mode can reach ±7.5mrad.

[0013] The present invention also provides a variable range high-resolution angular displacement measurement method, using the above-mentioned angular displacement measurement device, comprising:

[0014] When the angle to be measured is small, the angular displacement measuring device is in high-resolution mode. At this time, the two light spots on the area array image sensor are superimposed and interfered, and the angular displacement is measured by using the interference effect.

[0015] When the angle to be measured is large, the angular displacement measuring device is in the large-range mode. At this time, the two light spots hitting the area array image sensor are separated, and the angular displacement is measured using the optical lever effect.

[0016] The direction of the laser beam in the high-resolution mode is as follows: The beam is emitted from the laser light source, coupled through a polarization-maintaining fiber, and then enters the optical element module from the collimator. After that, it passes through the Faraday isolator. After passing through the beam splitter, the beam is divided into two paths, clockwise and counterclockwise. The clockwise beam passes through the fourth mirror, the fifth mirror, the third mirror, the polarization beam splitter, and the quarter-wave plate in sequence and then hits the target mirror. After reflection, it passes through the quarter-wave plate, the polarization beam splitter, the half-wave plate, the second mirror, and the first mirror again; the counterclockwise beam passes through the first mirror, the second mirror, the half-wave plate, the polarization beam splitter, and the quarter-wave plate in sequence and then hits the target mirror. After reflection, it passes through the quarter-wave plate, the polarization beam splitter, the third mirror, the fifth mirror, and the fourth mirror. Finally, the two beams converge again after the beam splitter and hit the area array image sensor together. Among them, the optical path difference between the clockwise and counterclockwise beams can be changed by changing the pitch angle of the non-target mirror or adding a phase compensator, thereby changing the phase difference during interference to ensure that the two light spots on the area array image sensor present approximately destructive interference with weak light intensity.

[0017] The working principle of the high-resolution mode is as follows: When the deflection angle of the target mirror is small and the two light spots on the area array image sensor overlap, the angular displacement is measured using the interference effect. Let the electric vector amplitudes of the two beams on the detector be E 10 、E 20 , the phase is , and the frequencies ω1 = ω2. Then, at a certain point P in the superposition region at time t, the field strengths of the two beams are respectively:

[0018]

[0019] According to the principle of linear superposition, the total field strength at point P is:

[0020]

[0021] When the beam is small, the deflection angle of the target mirror causes an optical path difference between the two beams on the area array image sensor, thereby changing the center position of the superposed light spot after interference; under the condition of bσ << a, we get:

[0022]

[0023] Among them, a = sin 2 φ2, b = -2k0θsinφ, σ is the light spot radius, k0 is the wave vector, and φ is the phase difference between the two beams; therefore, for a deflection angle θ of the target mirror, the translation amount x1 of the center of the superposed light spot after interference is:

[0024]

[0025] The relationship between the target mirror deflection angle θ and the translation x1 of the center of the superimposed light spot after interference is expressed by the calibration coefficient k:

[0026]

[0027] Therefore, this method can obtain a response of the deflection angle by detecting the translation amount, and can obtain the relationship curve between the translation amount and the deflection angle by calibration, which can directly and effectively reflect the change of the deflection angle. The typical measurement resolution level of angular displacement in high-resolution mode can be better than

[0028] The direction of the laser beam in the large-range mode is as follows: the beam is emitted by the laser light source, coupled by the polarization-maintaining fiber, and then incident on the optical element module from the collimator, and then passes through the Faraday isolator. After passing through the beam splitter, the beam is divided into two paths, clockwise and counterclockwise. The clockwise beam passes through the fourth reflector, the fifth reflector, the third reflector, the polarization beam splitter, and the 1 / 4 wave plate in turn, and then hits the target mirror. After reflection, it passes through the 1 / 4 wave plate, the polarization beam splitter, the half-wave plate, the second reflector, and the first reflector; the counterclockwise beam passes through the first reflector, the second reflector, the half-wave plate, the polarization beam splitter, and the 1 / 4 wave plate in turn, and then hits the target mirror. After reflection, it passes through the 1 / 4 wave plate, the polarization beam splitter, the third reflector, the fifth reflector, and the fourth reflector. Finally, the two beams converge again after the beam splitter and hit the area array image sensor together.

[0029] The principle of the large-range mode is: when the target mirror has a large deflection angle, the two light spots on the area array image sensor will basically not overlap, and the optical lever principle is used to measure the angular displacement. Assume that the optical paths of the clockwise and counterclockwise light beams from the target mirror to the area array image sensor are l1 and l2 respectively; at this time:

[0030] l1=l2=l (14)

[0031] When the target mirror has a deflection angle θ, according to the optical lever effect, the distance between the centers of the two light spots on the area array image sensor is:

[0032] Δx2=2l·sin2θ (15)

[0033] By measuring the distance Δx2 between the centers of the two light spots on the area array image sensor, the corresponding angle θ to be measured is obtained:

[0034]

[0035] Considering a typical case, for an area array image sensor with a size of 1 inch × 1 inch, the angular displacement measurement range of the wide range mode is ±7.5 mrad.

[0036] Furthermore, for the discussion in the high-resolution working mode, different device parameters correspond to different calibration coefficients k. Generally speaking, the smaller the calibration coefficient k, the higher the device resolution and the smaller the measurable θ angle range. For the large-range mode, the upper limit of this mode depends on the size of the area array image sensor and the arm length l of the optical lever effect. Therefore, the two working modes corresponding to different angle measuring devices have different ranges. Regarding the transition between the two modes, the above discussion and the related spot shape and position on the area array image sensor can be combined for analysis. The relationship between the spot position and shape changing with the deflection angle of the target reflector can be obtained through calibration.

[0037] Furthermore, for the angle values ​​to be measured between the high-resolution mode and the wide-range mode, the position and shape of the light spot on the area array image sensor are extracted by applying an angle of corresponding magnitude to the target reflector, and a one-to-one correspondence with the angle to be measured is established; when the angle to be measured of the target reflector falls within this interval, the corresponding angle is obtained according to the calibrated relationship here.

[0038] Furthermore, when the device is working, in order to improve the measurement resolution of the angular displacement measurement device, a periodic square wave modulation is added to the laser light source, and the noise background of the area array image sensor is suppressed by differential processing of the image data; including: using a square wave current to drive the laser light source, and its period is twice the sampling interval of the image sensor; the area array image sensor sequentially measures the target spot image when there is light, and the background noise such as the dark current of the area array image sensor when there is no light according to the timing of the modulated square wave, and the signal of the corresponding pixel of the image is subtracted during data processing, thereby deducting the background signal of the area array image sensor and reducing the low-frequency noise of the area array image sensor.

[0039] Furthermore, by utilizing the relationship between the spot position in the vertical direction of the area array image sensor and the pitch angle of the reflector of the target to be measured, two-dimensional angle measurement is performed while high-resolution measurement of the horizontal angle is performed.

[0040] In the above analysis, the deflection angle of the target mirror refers to the twisting in the plane of its optical path, and the two light spots move in the horizontal x-axis direction of the detector. The change in the pitch angle of the target reflector to be measured along the orthogonal direction will cause the light spot to move in the vertical direction. The area array image sensor can obtain the position of the light spot in two directions. By changing the known pitch angle and measuring the moving position of the light spot along the vertical direction, the calibration coefficient of the light spot position to the pitch angle can be obtained, so that the present invention can achieve high-resolution measurement of the x-direction angle while realizing two-dimensional angle measurement.

[0041] Compared with the prior art, the beneficial effects are:

[0042] 1. The present invention uses an array image sensor as a detector, which can realize high-resolution and large-range measurement modes respectively. The high-resolution mode uses the principle of laser interference to convert the angle change of the target reflector in a small range into a light spot translation, thereby achieving a high angle detection sensitivity. The large-range mode uses the principle of optical rods to obtain the angle of the target reflector by generating the displacement difference of the light spot through the clockwise and counterclockwise optical paths.

[0043] 2. The present invention adopts an area array image sensor as a detector, and utilizes the relationship between the vertical spot position of the area array image sensor and the pitch angle of the target reflector to achieve two-dimensional angle measurement while performing high-resolution measurement of the horizontal angle.

[0044] 3. The present invention modulates the laser light source with a periodic square wave, and uses an image sensor to measure the target spot image when there is light, and the background noise such as the dark current of the detector when there is no light according to the modulation timing. The background signal of the detector is deducted through differential data processing to reduce the low-frequency noise of the detector.

[0045] In summary, the present invention achieves high-resolution angular displacement measurement while taking into account a larger measuring range, and at the same time uses a periodic square wave modulation method to suppress low-frequency noise in the angle measuring device and achieves two-dimensional angle measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of the angular displacement measuring device of the present invention.

[0047] Figure 2 It is a schematic diagram of the detection image in the high-resolution working mode of the present invention.

[0048] Figure 3 It is a schematic diagram of the working principle of the present invention in high-resolution mode.

[0049] Figure 4 It is a schematic diagram of the detection image in the large-range working mode of the present invention.

[0050] Figure numerals: 1. laser light source; 2. fiber coupling mirror; 3. polarization-maintaining fiber; 4. fiber collimator; 5. Faraday isolator; 6. beam splitter; 7. polarization beam splitter; 8. half-wave plate; 9. quarter-wave plate; 10. first reflector; 11. second reflector; 12. third reflector; 13. fourth reflector; 14. fifth reflector; 15. target mirror; 16. area array image sensor. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The present invention is described in one of the embodiments in combination with the specific implementation methods. Among them, the drawings are only used for exemplary descriptions, and only schematic diagrams are shown, not physical drawings, and cannot be understood as limitations on this patent; in order to better illustrate the embodiments of the present invention, some parts of the drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0052] In the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only used for exemplary explanations and cannot be understood as a limitation of this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances. In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or schemes that satisfy both A and B.

[0053] Embodiment 1:

[0054] like Figure 1 As shown, this embodiment provides a high-resolution angular displacement measurement device with a variable range, comprising:

[0055] Light source module: It includes laser light source 1, fiber coupling mirror 2, polarization-maintaining fiber 3, and fiber collimator 4. The laser diode light source is incident through fiber coupling, the input power is 2mW, the wavelength is 632.8nm, the spot radius σ=0.6mm, the square wave modulation signal period T is set to 0.1s, and the duty cycle is 1:1. The laser light source 1 can be a laser diode.

[0056] Optical element module: It includes Faraday isolator 5, beam splitter 6, polarization beam splitter 7, half-wave plate 8, quarter-wave plate 9, first reflector 10, second reflector 11, third reflector 12, fourth reflector 13, fifth reflector 14 and target mirror 15. The size of each mirror is 1 inch. The short side of the interferometer is 6 cm and the long side is 10 cm.

[0057] Data acquisition module: includes the area array image sensor 16 and a data acquisition system connected to the area array image sensor 16 for acquiring data from the area array image sensor 16 .

[0058] The target mirror 15 and the array image sensor 16 are located at the upper end of the beam splitter 6 and the polarization beam splitter 7, respectively, and the distance is 10 cm. The fiber collimator 4 is located at the left end of the beam splitter 6 and the distance is 10 cm. The detector uses a 1 inch × 1 inch array image sensor 16, and the sampling rate is set to 20Hz. To reduce environmental disturbances, all modules in the figure are located on the optical platform, and the centers of all components are located at the same level. The assembly diagram is shown in Figure 1 shown.

[0059] The laser beam is emitted by the laser diode, coupled by the polarization-maintaining optical fiber 3, and then incident on the optical element module from the collimator, and then passes through the Faraday isolator 5. After passing through the beam splitter 6, the beam is divided into two clockwise and counterclockwise paths. The clockwise beam passes through the fourth reflector 13, the fifth reflector 14, the third reflector 12, the polarization beam splitter 7, and the 1 / 4 wave plate 9 in sequence, and then hits the target mirror 15. After reflection, it passes through the 1 / 4 wave plate 9, the polarization beam splitter 7, the half-wave plate 8, the second reflector 11, and the first reflector 10; the counterclockwise beam passes through the first reflector 10, the second reflector 11, the half-wave plate 8, the polarization beam splitter 7, and the 1 / 4 wave plate 9 in sequence, and then hits the target mirror 15. After reflection, it passes through the 1 / 4 wave plate 9, the polarization beam splitter 7, the third reflector 12, the fifth reflector 14, and the fourth reflector 13. Finally, the two beams converge again after the beam splitter 6 and hit the area array image sensor 16 together.

[0060] When the angle to be measured is small, the two light spots of the two light beams hitting the area array image sensor 16 are superimposed and interfered; when the angle to be measured is large, the two light spots of the two light beams hitting the area array image sensor 16 are separated.

[0061] Embodiment 2:

[0062] This embodiment provides a variable range high-resolution angular displacement measurement method, using the angular displacement measurement device provided in Embodiment 1, including:

[0063] (1) When the angle to be measured is small, the angular displacement measuring device is in high-resolution mode. At this time, the two light spots hitting the area array image sensor 16 are superposed and interfered, and the angular displacement is measured by using the interference effect. The detection image in the high-resolution working mode is as shown in Figure 2 Let the electric vector amplitudes of the two light beams on the area array image sensor 16 be E 10 , E 20 , and the phase be . If the frequencies ω1 = ω2, then the field strengths at a certain point P in the superposition area at time t are respectively:

[0064]

[0065] According to the principle of linear superposition, the total field strength at point P is:

[0066]

[0067] When the light beam is small, the deflection angle of the objective mirror 15 causes an optical path difference between the two light beams on the area array image sensor 16, and then changes the center position of the superposed light spot after interference, as shown in Figure 3 . Under the condition of satisfying bσ << a, we get:

[0068]

[0069] Among them, a = sin 2 φ2, b = -2k0θsinφ, σ is the light spot radius, k0 is the wave vector, and φ is the phase difference between the two light beams. Therefore, for a deflection angle θ of the objective mirror 15, the translation amount Δx1 of the center of the superposed light spot after interference is:

[0070]

[0071] The relationship between the deflection angle θ of the objective mirror 15 and the translation amount x1 of the center of the superposed light spot after interference is represented by the calibration coefficient k:

[0072]

[0073] Therefore, this method can obtain a response of the deflection angle by detecting the translation amount, and can obtain the relationship curve between the translation amount and the deflection angle through calibration, and then can directly and effectively reflect the change of the deflection angle. The typical measurement resolution level of the angular displacement in the high-resolution mode can be better than

[0074] (2) When the angle to be measured is large, the angular displacement measuring device is in a large-range mode. At this time, the two light spots hitting the area array image sensor 16 are separated, and the angular displacement is measured by using the optical lever effect. The detection image in the large-range working mode is as shown in Figure 4As shown. Assume that the optical paths of the clockwise and counterclockwise light beams from the target mirror 15 to the area array image sensor 16 are l1 and l2 respectively; at this time:

[0075] l1=l2=l (22)

[0076] When the target mirror 15 has a deflection angle θ, according to the optical lever effect, the distance between the centers of the two light spots on the area array image sensor 16 is:

[0077] Δx2=2l·sin2θ (23)

[0078] By measuring the distance Δx2 between the centers of the two light spots on the area array image sensor 16, the corresponding angle θ to be measured is obtained:

[0079]

[0080] Before carrying out the measurement, the angular displacement measuring device is calibrated. For the calibration of the high-resolution mode, the piezoelectric nano-optical adjustment mirror frame is used to control the target mirror 15 to deflect a smaller angle Δθ in turn, such as 0.1μrad each time. The center of gravity method is used to read the horizontal translation Δx1 of the center of mass of the superimposed light spot on the area array image sensor 16, and the corresponding calibration coefficient k=Δθ / Δx1 (typical value is 0.03rad / mm) can be obtained. During the calibration process, the angle measurement range with good linearity of the device output result can also be obtained. In this range, when measuring the small angle to be measured of the target reflector, the translation x1 of the center of mass of the light spot can be read at this time, and the small angle to be measured is θ=x1·k.

[0081] When the angle of the target reflector is large, the clockwise and counterclockwise optical paths are separated at the position of the light spot on the array image sensor 16, and the device enters the large-range mode, and the angle to be measured is obtained according to the principle of the optical lever. The optical lever effect arm length l1=l2=l, which can also be calibrated by rotating a certain angle and measuring the corresponding light spot movement distance to improve the measurement accuracy of the device. For the two light spots measured by the array image sensor 16, the distance x2 between the centers of the two light spots is obtained by the circle fitting method, and the corresponding angle to be measured θ is:

[0082]

[0083] If the size of the area array image sensor 16 is selected to be 1 inch×1 inch, it is expected that the angle that can be measured is within the range of ±7.5 mrad.

[0084] For the angle value to be measured between the high-resolution mode and the wide-range mode, a one-to-one correspondence with the angle to be measured is established by applying an angle of corresponding magnitude to the target reflector and extracting the position and shape of the light spot on the area array image sensor 16. When the angle to be measured of the target reflector to be measured falls within this interval, the corresponding angle can be obtained according to the relationship calibrated here.

[0085] Embodiment 3:

[0086] The other methods of this embodiment are the same as those of Embodiment 2, except that, in this embodiment, the optical path difference between the two clockwise and counterclockwise light beams is changed by changing the pitch angle of the non-target reflector or adding a phase compensator, thereby changing the phase difference during interference, thereby ensuring that the two light spots on the area array image sensor 16 present approximately destructive interference with weak light intensity.

[0087] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0088] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A high-resolution angular displacement measuring device with a variable range, characterized in that: Including: Light source module: including a laser light source (1), a fiber optic coupling mirror (2), a polarization maintaining fiber (3), and a fiber optic collimator (4); Optical element module: including a Faraday isolator (5), a beam splitter (6), a polarization beam splitter (7), a half-wave plate (8), a quarter-wave plate (9), a first mirror (10), a second mirror (11), a third mirror (12), a fourth mirror (13), a fifth mirror (14), and a target mirror (15); Data acquisition module: including a area array image sensor (16) and a data acquisition system connected to the area array image sensor (16) for acquiring data in the area array image sensor (16); The light beam is emitted from the laser light source (1), coupled by the polarization maintaining fiber (3), and then enters the optical element module from the collimator. After that, it passes through the Faraday isolator (5). After passing through the beam splitter (6), the light beam is divided into two paths, clockwise and counterclockwise. The clockwise light beam sequentially passes through the fourth mirror (13), the fifth mirror (14), the third mirror (12), the polarization beam splitter (7), and the quarter-wave plate (9) and then hits the target mirror (15). After reflection, it passes through the quarter-wave plate (9), the polarization beam splitter (7), the half-wave plate (8), the second mirror (11), and the first mirror (10) again; The counterclockwise light beam sequentially passes through the first mirror (10), the second mirror (11), the half-wave plate (8), the polarization beam splitter (7), and the quarter-wave plate (9) and then hits the target mirror (15). After reflection, it passes through the quarter-wave plate (9), the polarization beam splitter (7), the third mirror (12), the fifth mirror (14), and the fourth mirror (13) again; Finally, the two light beams converge again after the beam splitter (6) and hit the area array image sensor (16) together.

2. The variable range high-resolution angular displacement measuring device according to claim 1, characterized in that: When the angle to be measured is small, the two light spots of the two light beams hitting the area array image sensor (16) overlap and interfere; when the angle to be measured is large, the two light spots of the two light beams hitting the area array image sensor (16) are separated.

3. A variable range high-resolution angular displacement measurement method, characterized in that: Using the angular displacement measuring device described in claim 1 or 2, including: When the angle to be measured is small, the angular displacement measuring device is in a high-resolution mode. At this time, the two light spots hitting the area array image sensor (16) overlap and interfere, and the angular displacement is measured using the interference effect; When the angle to be measured is large, the angular displacement measuring device is in a large-range mode. At this time, the two light spots hitting the area array image sensor (16) are separated, and the angular displacement is measured using the optical lever effect.

4. The variable range high-resolution angular displacement measurement method according to claim 3, characterized in that: By changing the pitch angle of the non-target mirror or adding a phase compensator to change the optical path difference between the clockwise and counterclockwise light beams, and then changing the phase difference during interference, it is ensured that the two light spots on the area array image sensor (16) present approximate destructive interference with weak light intensity.

5. The variable range high-resolution angular displacement measurement method according to claim 3, characterized in that: When the angle to be measured is small, the electric vector amplitudes of the two light beams on the area array image sensor (16) are E and 10 、E 20 , the phase is Frequency ω1 = ω2, then the field strength at a point P in the superposition area at time t is: According to the principle of linear superposition, the total field strength at point P is: When the light beam is small, the deflection angle of the target mirror (15) causes an optical path difference between the two light beams on the area array image sensor (16), and then changes the center position of the overlapping light spot after interference; Under the condition of satisfying bσ << a, we get: Where a = sin 2 φ2,b=-2k0θsinφ, σ is the spot radius, k0 is the wave vector, and φ is the phase difference between the two beams; therefore, for a target mirror (15) with a deflection angle θ, the translation x1 of the center of the superimposed spot after interference is: The relationship between the deflection angle θ of the target mirror (15) and the translation amount x1 of the center of the superimposed light spot after interference is expressed by the calibration coefficient k:

6. The variable range high-resolution angular displacement measurement method according to claim 5, characterized in that: When the angle to be measured is relatively large, it is assumed that the optical paths of the clockwise and counterclockwise light beams from the target mirror (15) to the area array image sensor (16) are l1 and l2 respectively; at this time: l1＝l2＝l (6) When the target mirror (15) has a deflection angle θ, according to the optical lever effect, the distance between the centers of the two light spots on the area array image sensor (16) is: Δx2=2l·sin2θ (7) By measuring the distance Δx2 between the centers of the two light spots on the area array image sensor (16), the corresponding angle θ to be measured is obtained:

7. The variable range high-resolution angular displacement measurement method according to claim 6, characterized in that: For the high-resolution meter mode, the smaller the calibration coefficient k is, the higher the resolution of the displacement measuring device is, and the smaller the θ angle range that can be measured is; for the large-range mode, the upper limit of the measurement angle depends on the size of the area array image sensor (16) and the arm length l of the optical lever effect.

8. The variable range high-resolution angular displacement measurement method according to claim 6, characterized in that: By utilizing the relationship between the vertical spot position of the area array image sensor (16) and the pitch angle of the reflector of the target to be measured, two-dimensional angle measurement is performed while high-resolution horizontal angle measurement is performed.

9. The variable range high-resolution angular displacement measurement method according to any one of claims 3 to 8, characterized in that: For the angle value to be measured between the high-resolution mode and the large-range mode, a corresponding angle is applied to the target reflector to extract the position and shape of the light spot on the area array image sensor (16), and a one-to-one correspondence with the angle to be measured is established; when the angle to be measured of the target reflector falls within this interval, the corresponding angle is obtained according to the calibrated relationship.

10. The variable range high-resolution angular displacement measurement method according to any one of claims 3 to 8, characterized in that: In order to improve the measurement resolution of an angular displacement measurement device, a laser light source (1) is added with periodic square wave modulation, and the noise background of an area array image sensor (16) is suppressed by differential processing of image data; the method comprises: using a square wave current to drive the laser light source (1), wherein the period is twice the sampling interval of the area array image sensor (16); the area array image sensor (16) sequentially measures the target spot image when there is light, and the background noise such as the dark current of the area array image sensor (16) when there is no light according to the timing of the modulated square wave, and performing differential processing on the signals of the corresponding pixels of the image during data processing, thereby deducting the background signal of the area array image sensor (16) and reducing the low-frequency noise of the area array image sensor (16).

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