Mirror surface target displacement sensor capable of inhibiting inclination influence

Abstract

The invention provides a mirror surface target displacement sensor capable of suppressing inclination influence. A left laser and a right laser which are symmetrically arranged are adopted and are incident to a mirror surface target surface at the same inclination angle; a left receiving light path and a right receiving light path which are symmetrically arranged and a linear array CMOS device are adopted to receive reflected laser signals, and an attenuation piece is adopted for each path of receiving to greatly weaken the laser intensity, so that photoelectric devices are protected from being damaged. When the mirror surface target moves back and forth, the distance between the imaging waveforms generated on the left CMOS device and the right CMOS device also changes and belongs to a linear positive correlation relation, and therefore the distance value of the two imaging waveforms can be used for representing the distance of the measured target. When a measuring head or a measured mirror target is inclined, imaging waveforms on the left CMOS device and the right CMOS device are shifted in the same direction, the offset amount is the same, and therefore the distance value between the imaging waveforms on the two CMOS devices does not change, and the influence of inclination can be completely overcome.

Description

Technical Field

[0001] The present invention relates to a displacement sensor, in particular to a mirror target displacement sensor capable of suppressing the influence of tilt. Background Art

[0002] Laser displacement sensor is a sensor that measures the target distance based on the principle of laser triangulation. It has the significant advantages of non-contact, high precision, high speed and wide applicability, and its application is becoming more and more extensive. However, the existing laser displacement sensor mainly measures diffuse reflection targets and is not suitable for the distance and displacement of mirror reflection targets. The reason is that the laser beam emitted by the traditional laser displacement sensor irradiates the surface of the diffuse reflection target and forms a laser spot. The spot is imaged onto the surface of the photoelectric device after passing through the imaging mirror on one side, thereby realizing displacement and distance measurement. However, for targets with mirror reflection surfaces (such as wafers, stainless steel, surface-coated workpieces, etc.), the vertically incident laser beam will be directly reflected back to the laser, and the photoelectric device on one side cannot observe the laser spot at all, so the measurement fails.

[0003] The commonly used solution in the industry is to rotate the existing diffuse reflection laser displacement sensor by half the working angle, so that the reflected light directly enters the receiving end, so as to achieve the measurement of the mirror surface target. Although this method can achieve the function of measuring the mirror reflection target surface, the accuracy cannot be guaranteed at all. The reasons are as follows: First, the receiving optical path of the laser displacement sensor for measuring diffuse reflective targets belongs to the imaging optical path, while the specular target produces direct reflected laser light, and the two optical paths are completely different. If one optical path is forcibly used for another situation, the effect is bound to be greatly reduced.

[0004] Secondly, the practice of asking customers to rotate the probe by half a working angle lacks strict and precise positioning, the measurement accuracy cannot be guaranteed, and the operation is very unstable.

[0005] Third, the laser is reflected by the mirror target surface and then directly hits the imaging surface of the optoelectronic device. The extremely strong laser energy may cause damage to the optoelectronic device.

[0006] Fourth, when the sensor probe or the target has a tilt error during installation, it will directly change the position of the reflected light, resulting in serious measurement errors. Tilt error is also the largest of all error terms and the most important factor affecting the measurement accuracy of mirror targets. Summary of the invention

[0007] Aiming at the current situation that the existing laser displacement sensor cannot overcome the serious influence of the tilt of the probe or the mirror target on the measurement accuracy, the present invention proposes a mirror target displacement sensor that can suppress the influence of the tilt. The sensor adopts two symmetrically arranged lasers on the left and right sides, the symmetry axis is parallel to the normal of the mirror target to be measured, and is incident on the mirror target surface at the same tilt angle; the receiving optical path and the linear array CMOS device with two symmetrically arranged left and right sides are used as photoelectric devices to receive the reflected laser signal, the symmetry axis is parallel to the normal of the mirror target to be measured, the receiving optical path and the laser beam are also axially symmetrically arranged, and the symmetry axis is parallel to the normal of the mirror target to be measured, and each laser corresponds to one receiving optical path and CCD; each receiving path adopts an attenuation plate to greatly reduce the laser intensity to protect the photoelectric device from being damaged; each receiving path adopts an imaging mirror to converge the reflected laser so as to meet the imaging length requirements of the CMOS device. When the mirror target moves forward and backward, the distance between the imaging waveforms generated on the left and right CMOS devices also changes accordingly, and it is a linear positive correlation, so the distance value of the two imaging waveforms can be used to represent the distance of the measured target. When the probe or the measured mirror target is tilted, the imaging waveforms on the left and right CMOS devices will shift in the same direction with the same amount of shift. Therefore, the distance value between the imaging waveforms on the two CMOS devices does not change, and the influence of the tilt can be completely overcome.

[0008] The present invention is achieved through the following technical solutions: The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt proposed by the present invention is that the sensor comprises a laser, a focusing mirror, a window sheet, an attenuation sheet, an imaging mirror, a CMOS device, a synchronizer, a processing circuit, and a housing, wherein: The laser is a semiconductor laser diode, there are two of them, located on the left and right sides of the sensor probe, and can be turned on or off under the control of the processing circuit to achieve measurement and eye protection functions; The focusing mirror is an optical collimating focusing mirror, there are two of them, which are located on the left and right sides of the sensor probe and the front ends of the left and right lasers, respectively. They are made of optical glass or resin materials, and respectively converge the divergent beams of the left and right lasers into two collimated focusing beams, and project them to the surface of the measured mirror target at the same inclination angle; The window pieces are optical window pieces, and there are two of them, which are located at the left and right sides of the front end of the housing and the front end of the focusing lens, respectively, to ensure that the left and right laser beams can pass through with low loss, and at the same time play a sealing and protective role; The attenuation sheet is a neutral attenuation sheet, and there are two of them, which are located in the middle area of ​​the front end of the housing, respectively, to receive the reflected lasers generated by the left and right laser beams on the surface of the target to be measured, and can greatly attenuate the intensity of the reflected lasers from the mirror target surface, reduce the risk of damage to the CMOS device, and at the same time can greatly suppress the influence of ambient light; The imaging mirror is an aspherical imaging mirror, there are two of them, which are located inside the sensor probe and at the rear ends of the left and right attenuation plates, respectively, to converge the reflected laser from the mirror target surface and project it to the left and right CMOS devices respectively to achieve the measurement of the target distance; The CMOS device is a linear array CMOS device, there are two of them, which are respectively located at the rear ends of the left and right imaging mirrors, and are used to respectively receive two beams of reflected laser light from the mirror target surface, and respectively output electrical signals related to the positions of the centroids of the beam irradiation, and send them to the processing circuit for subsequent processing; The synchronizer is a pure logic circuit, which synchronously triggers the left and right CMOS devices under the control of the processing circuit and starts working, so as to ensure the real-time and synchronization of the imaging waveforms obtained by the left and right CMOS devices; The processing circuit is a measurement and control circuit with ARM as the core. On the one hand, it controls the left and right lasers to emit or turn off the lasers as needed; on the other hand, it directly and synchronously triggers the left and right CMOS devices through the synchronizer, and receives electrical signals from the left and right CMOS devices, and finally obtains the displacement value through data processing and calculation; The shell is a highly stable integral structural part, which can not only accurately position and reliably fix the internal components, but also realize the positioning and fixation of the entire sensor probe; the part where the attenuation plate is fixed on the shell is an embedded inclined structure, which, on the one hand, makes the normal direction of the attenuation plate close to the optical axis of the imaging mirror and improves the imaging quality; on the other hand, the shell can be used to form a light-shielding tube to play a certain light-shielding effect.

[0009] The working process of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is as follows: under the control of the processing circuit, two laser beams are simultaneously emitted by the left and right lasers, which are respectively focused by the left and right focusing mirrors and projected onto the surface of the mirror target to be measured at the same tilt angle. The intensity of the two reflected laser beams generated is greatly reduced after passing through two attenuation plates, and are respectively converged by the left and right imaging mirrors to the sensitive surfaces of the left and right CMOS devices. The processing circuit sends a synchronization control signal to the synchronizer, synchronously triggers the left and right CMOS devices to work, and outputs electrical signals related to the centroid of the imaging light spot respectively, and sends them to the processing circuit. The processing circuit finally obtains the distance value between the sensor and the mirror target to be measured through data processing.

[0010] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is that the angle between the left and right laser beams and the normal of the mirror target surface to be measured (i.e., the incident angle) can be changed according to the distance and displacement range of the mirror target to be measured, so that the housing has a unified specification and can adapt to all different specifications, thereby ensuring that the full series of sensors have good interchangeability and meeting the work process requirements of mass production, thereby significantly reducing costs.

[0011] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is that the two left and right laser beams are incident inwardly onto the mirror target surface to be measured, and the distance between the two incident points should be greater than twice the diameter of the imaging mirror.

[0012] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is that the attenuation plate 4 has a high attenuation rate, which can not only avoid damage to the CMOS device 6, but also ensure that the imaging waveform has a good amplitude height, thereby ensuring measurement accuracy.

[0013] The present invention proposes a processing method for a mirror target displacement sensor capable of suppressing the influence of tilt, which is specifically as follows: Under the control of the processing circuit, the left and right lasers are turned on at the same time to project the left and right laser beams onto the mirror target surface to be measured; The left and right laser beams are reflected by the mirror target surface and projected onto the sensitive surfaces of the left and right CMOS devices respectively, generating two imaging waveforms; The processing circuit sends a sampling signal to the synchronizer, which synchronously triggers the left and right CMOS devices, and sends the generated two imaging waveform signals to the processing circuit; The processing circuit processes the left and right imaging waveforms respectively to obtain the position coordinates of the imaging waveforms respectively; The processing circuit subtracts the position coordinates of the left and right imaging waveforms to obtain a distance value of the two imaging waveforms; The processing circuit converts the above two imaging waveform distance values ​​into the distance value between the sensor and the measured target using the calibration curve obtained by the previous calibration; When the measured mirror target moves back and forth, the positions of the two imaging waveforms move accordingly, with opposite directions and the same amount of movement. The processing circuit subtracts the position coordinates of the two left and right imaging waveforms, and finally obtains the distance value of the two imaging waveforms, which corresponds one to one with the distance of the measured precision target.

[0014] When the sensor probe or the measured mirror target is tilted, the positions of the left and right imaging waveforms will be offset, and the two offsets are equal in size and consistent in direction; the processing circuit subtracts the position coordinates of the left and right imaging waveforms, the two position offsets will be eliminated, and ultimately the error caused by the tilt will be eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the composition of the mirror target displacement sensor capable of suppressing the influence of tilt according to the present invention.

[0016] Figure 2 It is a schematic diagram of the working principle of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention.

[0017] Figure 3 It is a schematic diagram of the imaging waveform change principle of the sensor of the present invention.

[0018] Figure 4 It is a schematic diagram of the tilt suppression optical path principle of the sensor of the present invention.

[0019] Figure 5 It is a schematic diagram of the principle of the tilt suppression algorithm of the sensor of the present invention.

[0020] In the figure, 1-laser, 2-focusing mirror, 3-window plate, 4-attenuation plate, 5-imaging mirror, 6-CMOS device, 7-synchronizer, 8-processing circuit, 9-housing, 10-mirror target to be measured. DETAILED DESCRIPTION

[0021] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiment.

[0022] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt proposed by the present invention is that the sensor comprises a laser 1, a focusing lens 2, a window sheet 3, an attenuation sheet 4, an imaging lens 5, a CMOS device 6, a synchronizer 7, a processing circuit 8, and a housing 9. Figure 1 As shown, where: The laser 1 is a semiconductor laser diode, there are two of them, namely 1a and 1b, which are located on the left and right sides of the sensor probe, respectively, and can be turned on or off under the control of the processing circuit 8 to achieve measurement and human eye protection functions; The focusing mirror 2 is an optical collimating focusing mirror, and there are two of them, namely 2a and 2b, which are respectively located on the left and right sides of the sensor probe and at the front ends of the left and right lasers 1a and 1b, and are made of optical glass or resin materials. They respectively converge the divergent light beams of the left and right lasers 1a and 1b into two collimated focusing light beams, and project them to the surface of the measured mirror target 10 at the same inclination angle; The window sheet 3 is an optical window sheet, and there are two of them, namely 3a and 3b, which are respectively located on the left and right sides of the front end of the housing 9. The focusing lens is the front end of 2a and 2b, ensuring that the left and right laser beams can pass through with low loss, and at the same time play a sealing and protective role; The attenuation sheet 4 is a neutral attenuation sheet, and there are two of them, namely 4a and 4b, which are respectively located in the middle area of ​​the front end of the housing 9, and respectively receive the reflected lasers generated by the left and right laser beams on the surface of the measured target 10, which can greatly attenuate the intensity of the reflected laser from the surface of the mirror target 10, reduce the risk of damage to the CMOS device 6, and at the same time can greatly suppress the influence of ambient light; The imaging mirror 5 is an aspherical imaging mirror, and there are two of them, namely 5a and 5b, which are located inside the sensor probe and at the rear ends of the left and right attenuation plates, respectively, to converge the reflected laser from the mirror target surface and project it to the left and right CMOS devices, respectively, to achieve the measurement of the target distance; The CMOS device 6 is a linear array CMOS device, and there are two of them, namely 6a and 6b, which are respectively located at the rear ends of the left and right imaging mirrors 5a and 5b, and are used to respectively receive two beams of reflected laser light from the surface of the mirror target 10, and respectively output electrical signals related to the positions of the centroids of the beams, and send them to the processing circuit 8 for subsequent processing; The synchronizer 7 is a pure logic circuit, which synchronously triggers the left and right CMOS devices 6a and 6b under the control of the processing circuit 8 and starts working, so as to ensure the real-time and synchronization of the imaging waveforms obtained by the left and right CMOS devices 6a and 6b; The processing circuit 8 is a measurement and control circuit with ARM as the core. On the one hand, it controls the left and right lasers 1a and 1b to emit or turn off the lasers as needed; on the other hand, it directly and synchronously triggers the left and right CMOS devices 6a and 6b through the synchronizer 7, and receives electrical signals from the left and right CMOS devices 6a and 6b, and finally obtains the displacement value through data processing and calculation; The shell 9 is a highly stable integral structural part, which can not only accurately position and reliably fix the internal components, but also realize the positioning and fixation of the entire sensor probe; the part where the shell fixes the attenuation plates 4a and 4b is an embedded inclined structure, which on the one hand makes the normal direction of the attenuation plates 4a and 4b close to the optical axis of the imaging mirror and improves the imaging quality, and on the other hand, the shell can be used to form a light-shielding tube to play a certain light-shielding effect.

[0023] The working process of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is as follows: under the control of the processing circuit 8, two laser beams are simultaneously emitted by the left and right lasers 1a and 1b, and after being focused by the left and right focusing mirrors 2a and 2b and the window plates 3a and 3b, they are projected to the surface of the mirror target 10 to be measured at the same tilt angle. The intensity of the two reflected laser beams generated is greatly reduced after passing through the two attenuation plates 4a and 4b, and they are respectively converged by the left and right imaging mirrors 5a and 5b to the sensitive surfaces of the left and right CMOS devices 6a and 6b. The processing circuit 8 sends a synchronization control signal to the synchronizer 7, synchronously triggering the left and right CMOS devices 6a and 6b to work, and outputs electrical signals related to the centroid of the imaging light spot, respectively, and sends them to the processing circuit 8. The processing circuit 8 finally obtains the distance value between the sensor and the mirror target 10 to be measured through data processing.

[0024] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is that the angle between the left and right laser beams and the normal of the surface of the mirror target 10 to be measured (i.e., the incident angle) can be changed according to the distance and displacement range of the mirror target 10 to be measured, so that the housing 9 is of uniform specifications and can adapt to all different specifications, thereby ensuring that the full series of sensors have good interchangeability and meeting the requirements of mass production work process, thereby significantly reducing costs.

[0025] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is that the two left and right laser beams are incident inwardly onto the surface of the mirror target 10 to be measured, and the distance between the two incident points should be greater than twice the diameter of the imaging mirror 5.

[0026] The special feature of the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention is that the attenuation plate has a high attenuation rate, generally not less than 80%, which can not only avoid damage to the CMOS device, but also ensure that the imaging waveform has a good amplitude height, thereby ensuring measurement accuracy.

[0027] The present invention proposes a processing method for a mirror target displacement sensor capable of suppressing the influence of tilt, which is specifically as follows: (1) Under the control of the processing circuit 8, the left and right lasers 1a and 1b are turned on at the same time to project the left and right laser beams onto the surface of the mirror target 10 to be measured; (2) After being reflected by the mirror target 10, the left and right laser beams are projected onto the sensitive surfaces of the left and right CMOS devices 6a and 6b, respectively, generating two imaging waveforms, such as Figure 2 and Figure 3 As shown; (3) The processing circuit 8 sends a sampling signal to the synchronizer 7, which synchronously triggers the left and right CMOS devices 6a and 6b, and sends the generated two imaging waveform signals to the processing circuit 8; (4) The processing circuit 8 processes the left and right imaging waveforms respectively to obtain the position coordinates L and R of the imaging waveforms respectively; (5) The processing circuit 8 subtracts the position coordinates L and R of the two imaging waveforms to obtain a distance value D=LR between the two imaging waveforms; (6) The processing circuit 8 uses the calibration curve obtained by the previous calibration to convert the imaging waveform distance value D into the distance value d between the sensor and the target; (7) When the measured mirror target 10 moves forward and backward, the positions of the two imaging waveforms move accordingly, with opposite directions and the same amount of movement, as shown in Figure 2. Figure 3 The processing circuit subtracts the position coordinates of the two imaging waveforms, and finally obtains the distance value D=(L+Δ)-(R-Δ)=L-R+2Δ of the two imaging waveforms, which corresponds to the distance of the precision target 10 under test.

[0028] (8) When the sensor probe or the measured mirror target 10 is tilted, the positions of the left and right imaging waveforms are offset, and the two offsets are equal in magnitude and consistent in direction, such as Figure 4 and Figure 5 The processing circuit 8 subtracts the above two imaging waveform position coordinates, and the two position offsets will be eliminated, that is, D = (L + δ) - (R + δ) = LR, and finally the error δ caused by the tilt is eliminated. Compared with the prior art, the mirror target displacement sensor capable of suppressing the influence of tilt of the present invention has the following beneficial effects: The mirror target displacement sensor capable of suppressing the influence of tilt of the present invention adopts a laser tilted incidence method and a focusing optical path to achieve distance measurement of the mirror target, so that the material cost of the sensor is the same as that of a traditional laser displacement sensor, and the cost-performance ratio is outstanding.

[0029] The mirror target displacement sensor capable of suppressing the influence of tilt of the present invention adopts two mechanisms and an expensive receiving optical path, which are arranged in an axisymmetric manner to form a differential structure, and can completely eliminate the measurement error caused by the tilt of the probe or the target being measured, thereby greatly improving the user experience and practicality.

[0030] The mirror target displacement sensor capable of suppressing the influence of tilt of the present invention adopts a high-proportional attenuation plate to significantly reduce the intensity of reflected laser, thereby ensuring the safety of CMOS devices, optimizing imaging waveforms, and improving measurement and control accuracy.

[0031] The mirror target displacement sensor capable of suppressing the influence of tilt of the present invention can select different incident angles according to the distance of the target so as to ensure the same span, thereby keeping the outer dimensions of the shell consistent, reducing the production cost and maintaining a high cost performance. It can be seen that the technical solution of the present invention has very outstanding technical advantages and progress compared with traditional laser displacement sensors.

Claims

1. A mirror target displacement sensor capable of suppressing the influence of tilt is special in that the sensor comprises a laser, a focusing lens, a window sheet, an attenuation sheet, an imaging lens, a CMOS device, a synchronizer, a processing circuit, and a housing, wherein: The laser is a semiconductor laser diode, there are two of them, located on the left and right sides of the sensor probe, and can be turned on or off under the control of the processing circuit to achieve measurement and eye protection functions; The focusing mirror is an optical collimating focusing mirror, there are two of them, which are located on the left and right sides of the sensor probe and the front ends of the left and right lasers, respectively. They are made of optical glass or resin materials, and respectively converge the divergent beams of the left and right lasers into two collimated focusing beams, and project them to the surface of the measured mirror target at the same inclination angle; The window pieces are optical window pieces, and there are two of them, which are located at the left and right sides of the front end of the housing and the front end of the focusing lens, respectively, to ensure that the left and right laser beams can pass through with low loss, and at the same time play a sealing and protective role; The attenuation sheet is a neutral attenuation sheet, and there are two of them, which are located in the middle area of ​​the front end of the housing, respectively, to receive the reflected lasers generated by the left and right laser beams on the surface of the target to be measured, and can greatly attenuate the intensity of the reflected lasers from the mirror target surface, reduce the risk of damage to the CMOS device, and at the same time can greatly suppress the influence of ambient light; The imaging mirror is an aspherical imaging mirror, there are two of them, which are located inside the sensor probe and at the rear ends of the left and right attenuation plates, respectively, to converge the reflected laser from the mirror target surface and project it to the left and right CMOS devices respectively to achieve the measurement of the target distance; The CMOS device is a linear array CMOS device, there are two of them, which are respectively located at the rear ends of the left and right imaging mirrors, and are used to respectively receive two beams of reflected laser light from the mirror target surface, and respectively output electrical signals related to the positions of the centroids of the beam irradiation, and send them to the processing circuit for subsequent processing; The synchronizer is a pure logic circuit, which synchronously triggers the left and right CMOS devices under the control of the processing circuit and starts working, so as to ensure the real-time and synchronization of the imaging waveforms obtained by the left and right CMOS devices; The processing circuit is a measurement and control circuit with ARM as the core. On the one hand, it controls the left and right lasers to emit or turn off the lasers as needed; on the other hand, it directly and synchronously triggers the left and right CMOS devices through the synchronizer, and receives electrical signals from the left and right CMOS devices, and finally obtains the displacement value through data processing and calculation; The shell is a highly stable integral structural part, which can not only accurately position and reliably fix the internal components, but also realize the positioning and fixation of the entire sensor probe; the part where the attenuation plate is fixed on the shell is an embedded inclined structure, which, on the one hand, makes the normal direction of the attenuation plate close to the optical axis of the imaging mirror and improves the imaging quality; on the other hand, the shell can be used to form a light-shielding tube to play a certain light-shielding effect.

2. The mirror target displacement sensor capable of suppressing the influence of tilt according to claim 1, further characterized in that: The angle between the laser beam and the normal of the measured mirror target surface (i.e., the incident angle) can be changed according to the distance and displacement range of the measured mirror target, so that the housing has a unified specification and can adapt to all different specifications, thereby ensuring that the full range of sensors has good interchangeability and meets the work process requirements of mass production, thereby significantly reducing costs.

3. The mirror target displacement sensor capable of suppressing the influence of tilt according to claim 1, further characterized in that: The two left and right laser beams are incident inwardly onto the measured mirror target surface, and the distance between the two incident points should be greater than twice the diameter of the imaging mirror.

4. The mirror target displacement sensor capable of suppressing the influence of tilt according to claim 1, further characterized in that: The attenuation sheet has a high attenuation rate, which can not only avoid damage to the CMOS device, but also ensure that the imaging waveform has a good amplitude height, thereby ensuring measurement accuracy.

5. The present invention provides a data processing method according to any one of claims 1 to 4, which is specifically as follows: (1) Under the control of the processing circuit, the left and right lasers are turned on at the same time to project the left and right laser beams onto the mirror target surface to be measured; (2) The left and right laser beams are reflected by the mirror target surface and projected onto the sensitive surfaces of the left and right CMOS devices respectively, generating two imaging waveforms; (3) The processing circuit sends a sampling signal to the synchronizer, synchronously triggering the left and right CMOS devices, and sending the two generated imaging waveform signals to the processing circuit; (4) The processing circuit processes the left and right imaging waveforms respectively to obtain the position coordinates of the imaging waveforms respectively; (5) The processing circuit subtracts the position coordinates of the left and right imaging waveforms to obtain a distance value between the two imaging waveforms; (6) The processing circuit converts the above two imaging waveform distance values ​​into the distance values ​​between the sensor and the target using the calibration curve obtained by the previous calibration; (7) When the measured mirror target moves forward and backward, the positions of the two imaging waveforms move accordingly, with opposite directions and the same amount of movement. The processing circuit subtracts the position coordinates of the two imaging waveforms, and finally obtains the distance values ​​of the two imaging waveforms, which correspond to the distance of the measured precision target. (8) When the sensor probe or the measured mirror target is tilted, the positions of the left and right imaging waveforms will be offset, and the two offsets are equal in magnitude and consistent in direction; the processing circuit subtracts the position coordinates of the left and right imaging waveforms, and the two position offsets will be eliminated, and finally the error caused by the tilt will be eliminated.

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