Low-cost laser displacement sensor based on PSD

Abstract

The invention provides a low-cost laser displacement sensor based on a PSD. According to the sensor, a one-dimensional PSD (position sensitive device) is adopted as a photoelectric device, light spot change is directly converted into current output, and complex imaging waveform positioning calculation is avoided; a simple ARM is adopted as a processor, only simple operation is needed, and complex calculation of waveform positioning is avoided; a reflector is adopted to carry out turn-back layout on a light path, so that the volume and material consumption of the sensor are reduced; the laser, the focusing mirror, the imaging mirror, the reflecting mirror and the PSD device are simultaneously fixed by adopting the integrated connecting plate, so that the performance is stable and reliable, the assembly is convenient and fast, and the production efficiency is improved. The sensor can effectively solve the problem of high cost of a laser displacement sensor, the reduction amplitude of the measurement precision is limited, the measurement speed can be multiplied, the size is obviously reduced, the implementation cost is low, the cost performance is high, and the sensor has wide practicability and universality.

Description

Technical Field

[0001] The present invention relates to a laser displacement sensor, in particular to a low-cost laser displacement sensor based on a PSD device. 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 prices of existing laser displacement sensors are generally high. The reasons are mainly reflected in the following aspects: First, the cost of the optoelectronic devices sampled by the laser displacement sensor is relatively high. In order to ensure measurement accuracy, most of the existing laser displacement sensors sample various digital linear array optoelectronic devices, such as linear array CCD, linear array CMOS, etc. However, whether it is a linear array CCD or a linear array CMOS, its cost is generally high (hundreds of yuan or even higher), and it accounts for a large proportion of the material cost of the entire sensor, which has also become one of the main obstacles to reducing the cost of sensors.

[0004] Second, the cost of core devices for data processing is relatively high. In order to process a large amount of data from a linear array CCD or CMOS, obtain accurate positioning results of the imaging waveform and ensure a sufficiently high processing speed, it is often necessary to use a relatively high-performance processor, such as DSP or FPGA. However, whether it is DSP or FPGA, its cost is generally high, and it accounts for a large proportion of the material cost of the entire sensor, which has also become one of the main obstacles to reducing the cost of sensors.

[0005] Third, the laser displacement sensor is complex and bulky. In order to ensure accuracy, the laser emission unit and the imaging unit both use conventional direct optical paths, which require a lot of space, resulting in a large volume of the entire sensor, high material consumption, and high manufacturing costs.

[0006] Fourth, the laser displacement sensor has a complex structure and low production efficiency. In order to improve the measurement accuracy, the transmitting unit, imaging unit, photoelectric unit, etc. of the existing laser displacement sensor mostly adopts a relatively complex adjustable mechanism to ensure the accurate position of all photoelectric components (laser, focusing mirror, imaging mirror, photoelectric device, etc.). However, such a mechanism leads to multiple assembly, adjustment, and debugging links in the production process, low production efficiency and high manufacturing cost. Summary of the invention

[0007] Aiming at the high cost defect commonly existing in existing laser displacement sensors, the present invention proposes a low-cost laser displacement sensor based on PSD. The sensor adopts a one-dimensional PSD (position sensitive device) as a photoelectric device, directly converts the spot change into current output, and eliminates the complex imaging waveform positioning calculation; adopts a simple ARM as a processor, which only requires simple calculations, eliminating the complex calculation of waveform positioning; adopts a reflector to fold the optical path, reducing the volume of the sensor and material consumption; adopts an integrated connecting plate to fix the laser, focusing mirror, imaging mirror, reflector, and PSD device at the same time, which not only has stable and reliable performance, but also is easy and quick to assemble, thereby improving production efficiency. The sensor can effectively solve the high cost problem of laser displacement sensors, the measurement accuracy decreases to a limited extent, while the measurement speed can be doubled and the volume can be significantly reduced, achieving low cost and high cost performance, and has wide practicality and versatility.

[0008] The present invention is achieved through the following technical solutions: The low-cost laser displacement sensor proposed in the present invention is special in that the sensor includes a laser, a focusing lens, a filter, an imaging lens, a reflector, a PSD 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 beam is intermittently turned on and off under the control of the processing circuit to achieve automatic safety protection for human eyes and extend the service life of the laser. The focusing lens 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 into a collimated focusing beam, projects it onto the surface of the target to be measured, and forms a small-sized measuring light spot; The filter is a narrow-band filter, the central wavelength of which is consistent with that of the laser, and is used to filter out the influence of ambient light; The imaging mirror is an aspherical imaging mirror, which images the laser spot on the surface of the target to be measured and has very small aberration to ensure measurement accuracy; The reflector is a plane reflector, which can be used to fold back the direction of the light beam passing through the imaging mirror, changing the original direction of the light path to reduce the volume of the sensor. When the focal length of the imaging mirror is very long, in order to further compress the volume of the sensor, two reflectors are used to fold back the light path twice in succession. The PSD device is a position sensitive device that can be irradiated by a measuring light beam from a reflector and output an analog electrical signal related to the centroid position of the light beam irradiation and send it to a 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, reflector, and PSD 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 one hand, emit the laser or turn off the laser as needed; on the other hand, it receives the electrical signal from the PSD 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 place where the shell fixes the filter 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, and on the other hand, the shell can be used to form a light tube to play a certain light-shielding effect.

[0009] The working process of the low-cost laser displacement sensor based on PSD of the present invention is as follows: the laser beam emitted by the laser is focused by the focusing mirror and then projected onto the surface of the target to be measured, and a laser spot is formed on the surface of the target to be measured. After the laser spot passes through the light filter, it is imaged to the sensitive surface of the PSD device by the imaging mirror and the reflecting mirror. The PSD device outputs an electrical signal related to the centroid of the image spot and sends it to the processing circuit. The processing circuit finally obtains the distance value between the sensor and the target to be measured through data processing.

[0010] The special feature of the low-cost PSD-based laser displacement sensor of the present invention is that the housing is of uniform specifications and can adapt to all different specifications, thereby ensuring that the full range of sensors has good interchangeability and meets the requirements of mass production work process, thereby significantly reducing costs.

[0011] The special feature of the low-cost PSD-based laser displacement sensor of the present invention is that the connecting plate is of variable structural parameter type, which can adapt to all specifications of the full series, and takes into account both variability and stability.

[0012] The special feature of the low-cost PSD-based laser displacement sensor of the present invention is that the processing circuit is composed of several units including a driving circuit, an amplifying circuit, a processing circuit, a display circuit, a communication circuit, and a power supply circuit; the driving circuit is used to drive and control the laser diode, the amplifying circuit is used to amplify the electrical signal output by the PSD device, the processing circuit is a circuit based on an ARM with a built-in AD function as the core, the display circuit is used to display the measurement results, the power supply circuit provides energy and level reference for all circuits, and the communication circuit is used to transmit instructions and data between the sensor and the host computer.

[0013] The present invention proposes a processing method based on the above-mentioned low-cost PSD-based laser displacement sensor, which is as follows: (1) Turn on the laser and project the laser onto the surface of the target to be measured to form a light spot. The light spot passes through the imaging mirror and the reflector and then projects onto the sensitive surface of the PSD device to generate a corresponding image spot. (2) The PSD device generates two output electrical signals, the size of which is linearly related to the centroid position of the image spot on the sensitive surface of the PSD device; (3) The two electrical signals generated by the PSD device are sent to the processing circuit and converted into digital quantities; (4) The processing circuit processes the two digital quantities, calculates the difference between the two signals and the sum of the two signals respectively, and divides the difference from the sum to finally obtain a difference-sum ratio; (5) The processing circuit converts the above difference and ratio into the distance value between the sensor and the target using the calibration curve obtained in the previous calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the composition of the low-cost laser displacement sensor of the present invention.

[0015] Figure 2 It is a schematic diagram of the principle of the internal and external range control laser of the present invention.

[0016] Figure 3 It is a schematic diagram of the principle composition of the low-cost laser displacement sensor processing circuit of the present invention.

[0017] Figure 4 It is a schematic diagram of the calibration conversion principle of the low-cost laser displacement sensor of the present invention.

[0018] In the figure, 1-laser, 2-focusing lens, 3-filter, 4-imaging lens, 5-reflector, 6-PSD device, 7-connection board, 8-processing circuit, 9-housing, 10-target to be measured. DETAILED DESCRIPTION

[0019] 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.

[0020] The low-cost laser displacement sensor based on PSD proposed by the present invention is special in that the sensor includes a laser 1, a focusing lens 2, a filter 3, an imaging lens 4, a reflector 5, a PSD 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, such as a red laser diode with a wavelength of 650nm. When the measured 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 target 10 exceeds the measuring range, the laser 1 is intermittently turned on and off under the control of the processing circuit 8 to achieve an automatic safety protection function for the human eye and extend the service life of the laser 1. Figure 2 As shown; The focusing lens 2 is a collimating focusing lens, which can converge the divergent light beam of the laser diode 1 into a collimated focusing light beam, project it onto the surface of the target 10 to form a small-sized measuring light spot; The filter 3 is a narrow-band filter, the central wavelength of which is consistent with that of the laser 1, for example, 650 nm, and is used to overcome the influence of ambient light; The imaging mirror 4 is an aspherical imaging mirror, which can be made of optical glass or resin material, and images the laser spot on the surface of the measured target 10, and has very small aberration to ensure measurement accuracy; The reflector 5 is a plane reflector, such as an aluminum-plated reflector, which can be used to fold back the direction of the light beam passing through the imaging mirror 4, changing the original direction of the light path to reduce the volume of the sensor; when the focal length of the imaging mirror 4 is very long, in order to further compress the volume size of the sensor, two reflectors 5a and 5b are used to continuously fold the light path twice; The PSD device 6 is a position sensitive device that can receive the measurement light beam from the reflector 5, and output an analog electrical signal related to the centroid position of the light beam, 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, focusing mirror 2, imaging mirror 4, reflector 5, and PSD 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, such as STM32 chip, MSP430 single chip microcomputer, etc., which can control the laser 1 on the one hand, emit laser or turn off the laser as needed; on the other hand, it receives the electrical signal from the PSD device 6 and calculates the displacement value; The housing 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 fixing of the entire sensor; the housing 9 fixes the filter 3, which is an embedded inclined structure. On the one hand, the normal direction of the filter 3 is close to the optical axis of the imaging mirror 4, thereby improving the imaging quality; on the other hand, the housing 9 can be used to form a light cylinder, which plays a certain light shielding role, such as Figure 1 shown.

[0021] The working process of the low-cost laser displacement sensor based on PSD 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 onto the surface of the target 10 to be measured, and forms a laser spot, which is imaged by the imaging mirror 4 through the reflector 5 to the sensitive surface of the PSD device 6. The electrical signal output by the PSD device 6 enters the processing circuit 8, and the distance between the sensor and the target 10 to be measured is obtained through data processing.

[0022] The special feature of the low-cost PSD-based laser displacement sensor of the present invention is that the housing 9 is of uniform specifications and can adapt to all different specifications, thereby ensuring that the full range of sensors has good interchangeability and meets the requirements of mass production work process, thereby significantly reducing costs.

[0023] The special feature of the low-cost PSD-based laser displacement sensor of the present invention is that the connecting plate 7 is of variable structural parameter type, which can adapt to all specifications of the full series, and takes into account both variability and stability.

[0024] The special feature of the low-cost laser displacement sensor based on PSD of the present invention is that the processing circuit 8 is composed of several units, such as a driving circuit 8a, an amplifying circuit 8b, a processing circuit 8c, a display circuit 8d, a power supply circuit 8e, and a communication circuit 8f. Figure 3 As shown; the driving circuit 8a is used to drive and control the laser 1, the amplifier circuit 8b is used to amplify the electrical signal output by the PSD device 6, the processing circuit 8c is a circuit based on the built-in AD function ARM, the display circuit 8d is used to display the measurement results, the power supply circuit 8e provides energy and level reference for all circuits, and the communication circuit 8f is used to transmit instructions and data between the sensor and the host computer.

[0025] The present invention proposes a processing method based on the above-mentioned low-cost PSD-based laser displacement sensor, which is as follows: (1) Turn on the laser 1, project the laser onto the surface of the target 10 to form a light spot, and then the light spot passes through the imaging mirror 4 and the reflector 5 and is projected onto the sensitive surface of the PSD device 6, generating a corresponding image spot; (2) The PSD device 6 generates two output electrical signals P1 and P2, the magnitude of which is linearly related to the position of the image spot on the sensitive surface of the PSD device 6; (3) The two electrical signals I1 and I2 generated by the PSD device 6 are sent to the processing circuit 8 and converted into digital quantities D1 and D2; (4) The processing circuit 6 processes the two digital quantities D1 and D2, respectively calculates the difference D1-D2 of the two signals and the sum D1+D2 of the two signals, and divides the difference and the sum to finally obtain the difference-sum ratio, i.e., R = (D1-D2) / (D1+D2); (5) The processing circuit 6 converts the above difference and ratio R into the distance value d between the sensor and the target 10 using the calibration curve f(x) obtained previously, that is, d = f(R), as shown in Figure 4 shown. Compared with the prior art, the low-cost laser displacement sensor of the present invention has the following beneficial effects: (1) The low-cost laser displacement sensor based on PSD of the present invention uses a PSD device that costs only about 1 / 10 of that of a linear array CMOS, and uses an ARM chip that costs only about 1 / 5 of that of a DSP or FPGA. The use of a uniform specification housing and a mass production process can reduce the cost by more than half, making the material cost of the sensor only 1 / 3 of that of a traditional laser displacement sensor, with lower production costs and a prominent cost-performance advantage.

[0026] (2) The low-cost PSD-based laser displacement sensor of the present invention adopts PSD devices and has only two output signals. Not only is the data volume only about 1 / 1000 of that of linear array CMOS or CCD, but it also directly outputs an electrical signal related to the centroid position of the incident light beam, avoiding the tedious process of imaging waveform positioning calculation, and the speed of the sensor is increased by orders of magnitude.

[0027] (3) The low-cost PSD-based laser displacement sensor of the present invention can automatically turn on or off the laser according to whether the target is within the measuring range, thereby ensuring the normal measurement and protecting the safety of human eyes. At the same time, it can significantly extend the working life of the laser, achieving three goals at one stroke.

[0028] (4) The low-cost laser displacement sensor based on PSD of the present invention can effectively solve the high cost problem of laser displacement sensors, and the measurement accuracy is reduced to a limited extent, while the measurement speed is doubled and the volume is significantly reduced, which truly achieves low cost and high cost performance, and has wide practicality and versatility. Therefore, the cost performance is extremely advantageous. 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 low-cost laser displacement sensor based on PSD, characterized by: The sensor includes a laser, a focusing lens, a filter, an imaging lens, a reflector, a PSD 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 8, a measuring laser beam is generated and kept on, and the measuring function is completed; when the measured target exceeds the measuring range, the laser is intermittently turned on and off under the control of the processing circuit, realizing the automatic safety protection function for the human eye and extending the service life of the laser; The focusing lens is a collimating focusing lens, which can be made of optical glass or resin, and can converge the divergent light beam of the laser diode into a collimated focusing beam, project it onto the surface of the target to be measured, and form a small-sized measuring light spot; The filter is a narrow-band filter, the central wavelength of which is consistent with the laser, and is used to overcome the influence of ambient light; The imaging mirror is an aspherical imaging mirror, which images the laser spot on the surface of the target to be measured to ensure the measurement accuracy; The reflector is a plane reflector, which can bend the direction of the light beam passing through the imaging mirror, change the original direction of the light path, and reduce the volume of the sensor; when the focal length of the imaging mirror is very long, two reflectors are used to perform two consecutive light path foldings, further compressing the volume of the sensor; The PSD device is a position sensitive device that can receive the light beam from the reflector and output an analog electrical signal related to the centroid position of the light beam, and send it to the processing circuit for processing; The processing circuit is a measurement and control circuit with ARM as the core, which can control the laser on one hand, emit the laser or turn off the laser as needed; on the other hand, it receives the electrical signal from the PSD device and calculates the displacement value; The connecting plate is an integrated multifunctional structural part, which can accurately and reliably position and fix the laser, focusing mirror, imaging mirror, reflecting mirror and PSD device at the same time; The housing is a highly stable integral structural member, which can not only accurately position and reliably fix the connecting plate, but also realize the positioning and fixation of the entire sensor.

2. The low-cost PSD-based laser displacement sensor according to claim 1, further characterized in that: The housing is of uniform specifications and can adapt to all different specifications, thereby ensuring that the full range of sensors has good interchangeability and meets the requirements of mass production processes, thereby significantly reducing costs.

3. The low-cost PSD-based laser displacement sensor according to claim 1, further characterized in that: The connecting plate is of variable structural parameter type and can adapt to all specifications of the full series.

4. The low-cost laser displacement sensor based on PSD according to claim 1, further characterized by: The processing circuit is composed of a driving circuit, an amplifying circuit, a processing circuit, a display circuit, a communication circuit and a power supply circuit.

5. The present invention provides a data processing method according to any one of claims 1 to 5, which is specifically as follows: (1) Turn on the laser and project the laser onto the surface of the target to be measured to form a light spot. The light spot passes through the imaging mirror and the reflector and then projects onto the sensitive surface of the PSD device to generate a corresponding image spot. (2) The PSD device generates two output electrical signals, the size of which is linearly related to the position of the image spot on the sensitive surface of the PSD device; (3) The two electrical signals generated by the PSD device are sent to the processing circuit and converted into digital quantities; (4) The processing circuit processes the two digital quantities and calculates the ratio of the difference between the two signals and the sum of the two signals, that is, the difference-sum ratio; (5) The processing circuit converts the above difference and ratio into the distance value between the sensor and the target using the calibration curve obtained in the previous calibration.

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