A laser displacement sensor capable of measuring mirror targets

Abstract

The present invention provides a laser displacement sensor capable of measuring a mirror-reflective target. The laser is incident on the mirror-reflective target surface at a certain tilt angle, and the linear array CMOS device and the laser are symmetrically arranged with the normal of the mirror-reflective target surface as the symmetric axis. Attenuation products are used to greatly reduce the laser intensity, and a simple ARM is used as a processor, which only requires simple calculations. An integrated connecting plate is used to simultaneously fix the laser, attenuation plate, focusing mirror, reflector, and CMOS, which not only has stable and reliable performance, but also is convenient and quick to assemble, thereby improving production efficiency. The sensor can realize the displacement and distance measurement of precision reflective targets, has high measurement accuracy, good integration of the integrated probe, low cost, high cost-effectiveness, and has wide practicality and versatility.

Description

Technical Field

[0001] The present invention relates to a laser displacement sensor, in particular to a laser displacement sensor capable of measuring a mirror reflection target. Background Art

[0002] Laser displacement sensor is a sensor that measures 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.

[0003] However, the existing laser displacement sensors are only suitable for measuring diffuse reflection targets and are not suitable for the distance and displacement of specular 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 specular 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.

[0004] At present, some brands in the industry adopt a coping solution, which is to directly rotate the existing laser displacement sensor by half the working angle to achieve the measurement of the mirror surface target. Although this method can achieve the measurement of the mirror reflection target surface, the accuracy cannot be guaranteed. The reasons are as follows: First, the receiving optical path of the original laser displacement sensor is designed based on the principle of diffuse reflection target spot imaging, while the mirror target produces direct reflected laser light, and the two optical flows are completely different. Forcibly using one optical path for another situation will greatly reduce the effect.

[0005] 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.

[0006] 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.

[0007] Fourth, the laser directly hits the optoelectronic device, causing the imaging waveform to change. The diffuse reflection algorithm is no longer applicable and needs to be redesigned and evaluated. Summary of the invention

[0008] Aiming at the current situation that the existing laser displacement sensor cannot measure the mirror reflection target, the present invention proposes a laser displacement sensor that can measure the mirror reflection target. The sensor adopts a laser to enter the mirror surface at a certain tilt angle, adopts a linear array CMOS as a photoelectric device, and is symmetrically arranged with the laser with the normal line of the mirror surface as the symmetrical axis to receive the reflected laser signal; adopts an attenuation product to greatly reduce the laser intensity to protect the photoelectric device from damage; adopts a focusing mirror to converge the reflected laser to meet the imaging length requirements of CMOS; adopts a reflector to return the optical path to reduce the volume of the probe; adopts a simple ARM as a processor, which only requires simple calculations and eliminates the complex calculation of waveform positioning; adopts an integrated connection plate to fix the laser, attenuation plate, focusing mirror, reflector, and CMOS at the same time, which is not only stable and reliable in performance, but also convenient and quick to assemble, and improves production efficiency. The sensor can realize the displacement and distance measurement of precision reflection targets, has high measurement accuracy, good integration of the integrated probe, low cost, high cost performance, and has wide practicality and versatility.

[0009] The present invention is achieved through the following technical solutions: The laser displacement sensor for measuring mirror-reflective targets proposed in the present invention is special in that the sensor includes a laser, a focusing lens, a window sheet, an attenuation sheet, an imaging lens, a CMOS device, a connecting board, a processing circuit, and a housing, wherein: The laser is a semiconductor laser diode. When the measured target is within the measuring range, the laser is turned on under the control of the processing circuit to generate a measuring laser beam and keep it on to complete the measurement function. When the measured target exceeds the measuring range, the laser is turned on and off intermittently under the control of the processing circuit to realize the automatic safety protection function for the human eye and extend the service life of the laser. The focusing mirror is a collimating focusing mirror, which can be made of optical glass or resin material, and converges the divergent light beam of the laser diode into a collimated focusing beam, and projects it onto the surface of the mirror target to be measured at a certain inclination angle; The window is an optical window, which ensures that the laser beam can pass through with low loss and plays a sealing and protective role; The attenuation sheet is a full-band medium-sized attenuation sheet, which can significantly attenuate the intensity of the reflected laser from the mirror target surface, reduce the risk of damage to the CMOS device, and filter out the influence of ambient light; The imaging mirror is an aspherical imaging mirror, which images the reflected laser from the mirror target surface and projects it onto the CMOS device to ensure measurement accuracy; The CMOS device is a linear array CMOS device, which can receive reflected laser irradiation from the mirror target surface, and output an electrical signal related to the centroid position of the beam irradiation, and send it to the processing circuit for processing; The connecting plate is an integrated multifunctional structural part, which can accurately and reliably position and fix the laser, focusing mirror, imaging mirror, and CMOS device at the same time to form an optoelectronic assembly, which is convenient for separate assembly and debugging, improves production efficiency, and reduces production costs; The processing circuit is a measurement and control circuit with ARM as the core, which can control the laser on the one hand, emit the laser or turn off the laser as needed; on the other hand, it receives the electrical signal from the CMOS device and calculates the displacement value; The shell is a highly stable integral structural part, which can not only accurately position and reliably fix the connecting plate, but also realize the positioning and fixation of the entire sensor; the part where the attenuation plate is fixed in the shell is an embedded inclined structure, which, on the one hand, makes the normal direction of the filter 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 tube to play a certain light-shielding effect.

[0010] The working process of the laser displacement sensor capable of measuring the mirror reflection target of the present invention is as follows: the laser beam emitted by the laser is focused by the focusing mirror and then projected to the surface of the mirror target to be measured at a certain tilt angle. The intensity of the reflected laser beam is greatly reduced after passing through the attenuation plate, and is imaged to the sensitive surface of the CMOS device by the imaging mirror. The CMOS device outputs an electrical signal related to the image spot and sends it 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.

[0011] The laser displacement sensor capable of measuring mirror-reflective targets of the present invention is also special in that the angle between the laser beam and the normal of the mirror-reflective target surface (i.e., the incident angle) can be changed according to the distance and displacement range of the mirror-reflective 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 requirements of mass production work process, thereby significantly reducing costs.

[0012] The laser displacement sensor capable of measuring mirror-reflective targets of the present invention is also special in that the attenuation plate has a high attenuation rate, which can not only avoid damage to CMOS devices, but also ensure that the imaging waveform has a good amplitude height, thereby ensuring measurement accuracy.

[0013] The present invention proposes a processing method based on the above-mentioned laser displacement sensor capable of measuring mirror reflection targets, which is specifically as follows: (1) Under the control of the processing circuit, turn on the laser and project the laser onto the mirror target surface to be measured. After being reflected by the mirror target surface, the laser is projected onto the sensitive surface of the CMOS device, generating a corresponding light spot. (2) The CMOS device generates an electrical signal and sends it to the processing circuit to obtain an imaging waveform corresponding to the light spot position; (3) The processing circuit adaptively controls the output of the laser according to the amplitude of the imaging waveform to ensure that the amplitude of the imaging waveform reaches the ideal height; (4) The processing circuit processes the grayscale of each pixel of the imaging waveform to obtain the position coordinates of the imaging waveform; (5) The processing circuit uses the calibration curve obtained in the previous calibration to convert the above imaging waveform position coordinates into the distance value between the sensor and the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the composition of the laser displacement sensor capable of measuring a mirror reflection target according to the present invention.

[0015] Figure 2 It is a schematic diagram of the principle of selecting incident angles of different ranges of the sensor of the present invention.

[0016] Figure 3 It is a schematic diagram of the attenuation sheet principle of the sensor of the present invention.

[0017] In the figure, 1-laser, 2-focusing lens, 3-window, 4-filter, 5-imaging lens, 6-CMOS device, 7-connection board, 8-processing circuit, 9-housing, 10-mirror target to be measured. DETAILED DESCRIPTION

[0018] 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.

[0019] The laser displacement sensor for measuring mirror-reflective targets proposed in the present invention is special in 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 connecting board 7, a processing circuit 8, and a housing 9. Figure 1 As shown, where: The laser 1 is a semiconductor laser diode. When the measured mirror target 10 is within the measuring range, the laser 1 is turned on under the control of the processing circuit 8 to generate a measuring laser beam and keep it on, thereby completing the measuring function. When the measured mirror target 10 is beyond the measuring range, the laser 1 is intermittently turned on and off under the control of the processing circuit 8, thereby realizing the automatic safety protection function for the human eye and prolonging the service life of the laser 1. The focusing lens 2 is a collimating focusing lens, which can be made of optical glass or resin material, and converges the divergent light beam of the laser diode 1 into a collimated focusing beam and Figure 1The θ of the species is projected onto the surface of the measured mirror target 10; The window sheet 3 is an optical window sheet, which ensures that the laser beam can pass through with low loss and a transmittance of not less than 90%, and also plays a sealing and protective role; The attenuation sheet 4 is a full-band medium-sized attenuation sheet, which can significantly attenuate the intensity of the reflected laser from the mirror target surface, with an attenuation rate of not less than 5%, thereby reducing the risk of damage to the CMOS device 6 and filtering out the influence of ambient light; The imaging mirror 5 is an aspherical imaging mirror, which images the reflected laser from the surface of the mirror reflection target 10 and projects it to the CMOS device 6 to ensure the measurement accuracy; The CMOS device 6 is a linear array CMOS device, which can receive reflected laser irradiation from the surface of the mirror target 10, and output an electrical signal related to the centroid position of the beam irradiation, and send it to the processing circuit 8 for processing; The connecting plate 7 is an integrated multifunctional structural part, which can accurately and reliably position and fix the laser 1, the focusing mirror 2, the imaging mirror 5, and the CMOS device 6 at the same time to form an optoelectronic assembly, which is convenient for separate assembly and debugging, improves production efficiency, and reduces production costs; The processing circuit 8 is a measurement and control circuit with ARM as the core, which can control the laser 1 to emit or turn off the laser as needed; on the other hand, it receives the electrical signal from the CMOS device 6 and calculates the displacement value; The shell 9 is a highly stable integral structural member, which can not only accurately position and reliably fix the connecting plate 7, but also realize the positioning and fixation of the entire sensor; the part where the shell 9 fixes the attenuation plate 4 is an embedded inclined structure, which, on the one hand, makes the normal direction of the attenuation plate consistent with the optical axis of the imaging mirror and improves the imaging quality; on the other hand, the shell 9 can be used to form a light tube to play a certain shading effect.

[0020] The working process of the laser displacement sensor capable of measuring a mirror-reflective target of the present invention is as follows: the laser beam emitted by the laser 1 is focused by the focusing mirror 2 and then projected to the surface of the mirror-reflective target 10 to be measured at a certain tilt angle. The intensity of the reflected laser beam is greatly reduced after passing through the attenuation sheet 4, and is imaged to the sensitive surface of the CMOS device 6 by the imaging mirror 5. The CMOS device 6 outputs an electrical signal related to the image spot and sends it to the processing circuit 8. The processing circuit 8 finally obtains the distance value between the sensor and the mirror-reflective target 10 to be measured through data processing.

[0021] The laser displacement sensor capable of measuring a mirror-reflective target of the present invention is also special in that the angle between the laser beam and the normal line of the measured mirror-reflective target surface (i.e., the incident angle) can be changed according to the distance and displacement range of the measured mirror-reflective target, such as Figure 2As shown, the housing is of uniform 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.

[0022] The laser displacement sensor capable of measuring a mirror-reflecting target of the present invention is also special in that the attenuation sheet 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 the measurement accuracy. Figure 3 shown.

[0023] The present invention proposes a processing method based on the above-mentioned laser displacement sensor capable of measuring mirror reflection targets, which is specifically as follows: (1) Under the control of the processing circuit 8, the laser 1 is turned on to project the laser onto the surface of the mirror target 10 to be measured. After being reflected by the surface of the mirror target 10, the laser is projected onto the sensitive surface of the CMOS device 6, generating a corresponding light spot; (2) The electrical signal generated by the CMOS device 6 is sent to the processing circuit 8 to obtain an imaging waveform corresponding to the light spot position; (3) The processing circuit 8 adaptively controls the output of the laser 1 according to the amplitude of the imaging waveform to ensure that the amplitude of the imaging waveform reaches an ideal height; (4) The processing circuit 8 processes the grayscale of each pixel of the imaging waveform to obtain the position coordinates of the imaging waveform, for example, by using the centroid method to calculate the centroid of the imaging waveform as the position coordinates of the prime minister waveform; (5) The processing circuit 8 uses the calibration curve obtained by the previous calibration to convert the above imaging waveform position coordinates into the distance value between the sensor and the target 10 to be measured.

[0024] Compared with the prior art, the low-cost laser displacement sensor of the present invention has the following beneficial effects: (1) The laser displacement sensor capable of measuring a mirror-reflective target of the present invention uses an oblique laser incidence method to achieve distance measurement of the mirror target, thereby making the material cost of the sensor the same as that of a traditional laser displacement sensor, and having an outstanding cost-effectiveness advantage.

[0025] (2) The laser displacement sensor of the present invention, which can measure mirror-reflective targets, adopts a high-proportional attenuation plate to significantly reduce the intensity of the reflected laser, thereby ensuring the safety of the CMOS device, optimizing the imaging waveform, and improving the measurement and control accuracy.

[0026] (3) The laser displacement sensor capable of measuring a mirror-reflecting target 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 housing consistent, reducing the manufacturing cost and maintaining a high cost-performance ratio.

[0027] 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 laser displacement sensor capable of measuring a mirror-reflecting target 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 connecting board, a processing circuit, and a housing, wherein: The laser is a semiconductor laser diode. When the measured target is within the measuring range, the laser is turned on under the control of the processing circuit to generate a measuring laser beam and keep it on to complete the measuring function. When the measured target exceeds the measuring range, the laser is turned on and off intermittently under the control of the processing circuit to realize the automatic safety protection function for the human eye and extend the service life of the laser. The focusing mirror is a collimating focusing mirror, which can be made of optical glass or resin material, and converges the divergent light beam of the laser diode into a collimated focusing beam, and projects it onto the surface of the mirror target to be measured at a certain inclination angle; The window is an optical window, which ensures that the laser beam can pass through with low loss and plays a sealing and protective role; The attenuation sheet is a full-band medium-sized attenuation sheet, which can significantly attenuate the intensity of the reflected laser from the mirror target surface, reduce the risk of damage to the CMOS device, and filter out the influence of ambient light; The imaging mirror is an aspherical imaging mirror, which images the reflected laser from the mirror target surface and projects it onto the CMOS device to ensure measurement accuracy; The CMOS device is a linear array CMOS device, which can receive reflected laser irradiation from the mirror target surface, and output an electrical signal related to the centroid position of the beam irradiation, and send it to the processing circuit for processing; The connecting plate is an integrated multifunctional structural part, which can accurately and reliably position and fix the laser, focusing mirror, imaging mirror, and CMOS device at the same time to form an optoelectronic assembly, which is convenient for separate assembly and debugging, improves production efficiency, and reduces production costs; The processing circuit is a measurement and control circuit with ARM as the core, which can control the laser on the one hand, emit the laser or turn off the laser as needed; on the other hand, it receives the electrical signal from the CMOS device and calculates the displacement value; The shell is a highly stable integral structural part, which can not only accurately position and reliably fix the connecting plate, but also realize the positioning and fixation of the entire sensor; the part where the attenuation plate is fixed in the shell is an embedded inclined structure, which, on the one hand, makes the normal direction of the filter 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 tube to play a certain light-shielding effect.

2. The laser displacement sensor capable of measuring a mirror-reflective target 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 laser displacement sensor capable of measuring a mirror-reflective target 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.

4. The present invention provides a data processing method according to any one of claims 1 to 5, which is specifically as follows: (1) Under the control of the processing circuit, turn on the laser and project the laser onto the mirror target surface to be measured. After being reflected by the mirror target surface, the laser is projected onto the sensitive surface of the CMOS device, generating a corresponding light spot. (2) The CMOS device generates an electrical signal and sends it to the processing circuit to obtain an imaging waveform corresponding to the light spot position; (3) The processing circuit adaptively controls the output of the laser according to the amplitude of the imaging waveform to ensure that the amplitude of the imaging waveform reaches the ideal height; (4) The processing circuit processes the grayscale of each pixel of the imaging waveform to obtain the position coordinates of the imaging waveform; (5) The processing circuit uses the calibration curve obtained in the previous calibration to convert the above imaging waveform position coordinates into the distance value between the sensor and the target.

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