A dual-beam included angle self-compensation roll angle measurement device and method

Abstract

The application discloses a kind of double-beam included angle self-compensation's roll angle measuring device and method, measuring device is composed of transmitting end and receiving end, transmitting end includes laser, first beam splitter, second beam splitter, third beam splitter, first mirror, second mirror, Wollaston prism, first quadrant photodiode, second quadrant photodiode, first photodiode, second photodiode;Accepting end includes polarizing beam splitter, third mirror, first right-angle prism and second right-angle prism;Receiving end is installed on the measured object.The application will be based on two collimated light beams measurement roll angle and based on polarization measurement roll angle two methods are combined, by the roll angle compensation calibration light path based on polarization designed to be applied to the roll angle measurement system based on two collimated light beams, greatly improve the real-time measurement accuracy of roll angle under long distance.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a high-precision, miniaturized roll angle measuring device and method with self-compensating dual-beam angle. Background Technology

[0002] CNC machine tools, as the mother machines of industry, are the foundation for the manufacture of other equipment. Their machining accuracy determines the quality of the manufactured equipment. Among these, the measurement and calibration of machine tool geometric errors are important and effective means to improve the machining accuracy of machine tool products. Research shows that machine tool operation involves six error elements, including three movement errors and three rotation errors. Multi-degree-of-freedom measurement methods can simultaneously measure multiple errors of a single axis of the machine tool, offering advantages such as fast measurement, low cost, and easy integration. This makes online measurement of machine tool geometric errors feasible and has been widely applied in aerospace, mechanical manufacturing, and other fields. However, existing multi-degree-of-freedom measurement methods mainly employ a roll angle measurement method based on dual collimated beams for real-time measurement of the roll angle of CNC machine tools. This method has low accuracy and is difficult to integrate. Furthermore, the error introduced by the non-parallelism of the dual collimated beams significantly affects the measurement accuracy. Therefore, a high-precision, miniaturized roll angle measurement device based on polarization-based dual-beam angle self-compensation was designed. By measuring the roll angle attitude at different positions on the machine tool guideway using both dual collimated beams and polarization, the included angle of the dual collimated beams is calculated. This achieves calibration of the dual collimated beam measurement results and improves the roll angle measurement accuracy. This has significant practical engineering implications for improving the roll angle measurement accuracy and machining accuracy of machine tools. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-precision, miniaturized roll angle measurement device and method with self-compensation of dual-beam angle.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A roll angle measuring device with self-compensated dual-beam angle comprises a transmitter and a receiver. The transmitter includes a laser, a first beam splitter, a second beam splitter, a third beam splitter, a first reflector, a second reflector, a Wollaston prism, a first four-quadrant photodiode, a second four-quadrant photodiode, a first photodiode, and a second photodiode.

[0006] The receiving end includes a polarizing beam splitter, a third reflecting mirror, a first right-angle prism, and a second right-angle prism;

[0007] The laser emitted from the laser is split into two beams, transmitted and reflected, by a first beam splitter. The transmitted beam from the first beam splitter is reflected by a first reflector and then by a third beam splitter, where it is split into two beams again. The reflected beam from the third beam splitter is reflected by a second reflector to a first right-angle prism and then by a second reflection before being received by a first four-quadrant photodiode. The transmitted beam from the third beam splitter is reflected by a second right-angle prism and then by a second reflection before being received by a second four-quadrant photodiode. The reflected beam from the first beam splitter is split into two beams, transmitted and reflected, by a second beam splitter. The reflected beam from the second beam splitter is then received by a first photodiode and a second photodiode after passing through a Wollaston prism. The transmitted beam from the second beam splitter passes sequentially through a polarizing beam splitter and a third reflector, and then returns to the second beam splitter along the same path after being reflected by the third reflector.

[0008] Furthermore, the receiving end is installed on the object under test. Based on the first and second quadrant photodiodes, when the receiving end generates a roll angle, the polarization vector of the incident light changes accordingly. After being split by the second beam splitter, the light intensity illuminating the first and second photodiodes changes accordingly. The roll angle is measured by the relationship between the light intensity on the first and second photodiodes, and the angle between the double collimated beams incident on the first and second quadrant photodiodes is calculated. Finally, the calculated angle is used to compensate for the roll angle measured by the first and second quadrant photodiodes, thereby realizing the roll angle measurement.

[0009] The present invention also provides a roll angle measurement method with self-compensated dual-beam included angle, comprising:

[0010] (1) Roll angle measurement is performed based on a dual collimated beam directed at the first and second quadrant photodiodes; when the receiver generates a roll angle ε dz At that time, the first and second quadrant photodiodes produce a vertical straightness δ in the Y-axis direction. yr and δ yl The light spot is shifted by -Δy in the Y-axis direction of the photodiode in the first and fourth quadrants and the photodiode in the second and fourth quadrants, respectively. QD1 and -Δy QD2 The distance between the two collimated beams along the X-axis is denoted as L, and the measured roll angle error is denoted as ε. droll The roll angle is then expressed as:

[0011]

[0012] (2) Introduce roll angle measurement error; assume that there is an angular drift θ in the double collimated beam. up The two four-quadrant photodiodes are offset by Δε in the Y-axis direction.droll for

[0013] Roll angle measurement error Δε caused by laser angle drift droll It varies linearly with the measurement distance D;

[0014] (3) Roll angle measurement based on polarization: By adjusting the polarizing beam splitter, the vibration direction of the incident light from the second beam splitter is set to be parallel to the X-axis. Then, when the receiver generates a roll angle ε pz At that time, the light intensities measured by the first photodiode and the second photodiode were respectively:

[0015]

[0016] in It is the light intensity measured by the first photodiode. I0 is the light intensity measured by the second photodiode, I0 is the total intensity of the two beams, and the intensity difference ΔI between the two beams is:

[0017]

[0018] By equating the roll angle to an infinitesimal, we obtain the roll angle ε measured by the first photodiode and the second photodiode. proll for:

[0019]

[0020] (4) The roll angle ε measured in step (1) droll Perform compensation calibration: After starting calibration, the roll angle measured by the first four-quadrant photodiode and the second four-quadrant photodiode in step (1) is ε. droll In step (3), the roll angle measured by the first photodiode and the second photodiode is ε. proll The receiver is moved to a certain position, and continuous measurement is performed over a time period t seconds, with one result obtained per second, denoted as ε. proll,t Then, the average of these t measured results is taken to eliminate random errors, resulting in...

[0021]

[0022] Based on the above formulas (1) and (6), measurements are taken at different locations A and B at the receiving end to obtain ε. droll_A , and ε droll_B , The angle drift θ is calculated after differentiation. up for:

[0023]

[0024] Where D AB The distance between points A and B; the measured roll angle ε after compensation and calibration. cdroll for:

[0025]

[0026] Where D is the distance between the transmitter and receiver, i.e., the measurement distance.

[0027] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0028] 1. This invention combines two methods: roll angle measurement based on dual collimated beams and roll angle measurement based on polarization. By applying the designed polarization-based roll angle compensation and calibration optical path to the roll angle measurement system based on dual collimated beams, the real-time measurement accuracy of roll angle over long distances is greatly improved.

[0029] 2. This invention adopts a separate receiving end and transmitting end, realizing photoelectric separation. That is, the receiving end only has optical elements and no electrical connection, avoiding the rolling angle measurement error caused by the tension generated by the cable connection when the measured object moves. It is also easy to install in actual use.

[0030] 3. The optical path of the measurement optical path of the present invention is twice the measurement distance, thus the roll angle measurement resolution is increased by 2 times. Compared with the ordinary transceiver integrated type, which requires increasing the distance between the two beams to increase the roll angle measurement resolution, this method can reduce the size of the measurement device while ensuring measurement accuracy. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the roll angle measuring device with self-compensated dual-beam angle of the present invention.

[0032] Figure 2a This is a diagram of the optical path structure of a dual collimated beam using two four-quadrant photodiodes.

[0033] Figure 2b This is a schematic diagram showing the relationship between the roll angle and the position of the light spot on the two four-quadrant photodiodes.

[0034] Figure 3 This is a schematic diagram of the roll angle measurement error caused by the angle between two collimated beams.

[0035] Figure 4 This is a schematic diagram showing the positions of the two four-quadrant photodiodes when the roll angle measurement error is caused by the angle between the two collimated beams.

[0036] Figure reference numerals: 1-Laser, 2-Beam splitter, 3-Reflector, 4-Beam splitter, 5-Wollaston prism, 6-Photodiode, 7-Photodiode, 8-Reflector, 9-Beam splitter, 10-Four-quadrant photodiode, 11-Four-quadrant photodiode, 12-Right-angle prism, 13-Reflector, 14-Polarizing beam splitter, 15-Right-angle prism Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0038] This embodiment provides a high-precision, miniaturized roll angle measurement device with self-compensating dual-beam included angle, such as... Figure 1 As shown, it consists of a transmitter and a receiver. The transmitter includes a laser 1, beam splitters 2, 4, and 9, a reflector 3 and 8, a Wollaston prism 5, a four-quadrant photodiode 10 and 11, a photodiode 6, and a photodiode 7. The receiver includes a polarizing beam splitter 14, a reflector 13, a right-angle prism 12, and a right-angle prism 15.

[0039] Specifically, the laser emitted from laser 1 is split into two beams by beam splitter 2: one along the -Z direction and the other along the +X direction. One beam along the +X direction is reflected by mirror 3 and then along the -Z direction to beam splitter 9. Beam splitter 9 splits the beams along the -X direction and the other along the -Z direction. The beam along the -X direction reaches mirror 8 and is reflected by right-angle prism 12. After a second reflection by right-angle prism 12, it is received by four-quadrant photodiode 10. The beam along the -Z direction is reflected by right-angle prism 15 and after a second reflection by right-angle prism 15, it is received by four-quadrant photodiode 11. The other beam, after being split by beam splitter 2, along the -Z direction, passes through beam splitter 4 and polarizing beam splitter prism 14 along the -Z direction. After being reflected by mirror 13, it returns to beam splitter 4 along the +Z direction. After being split by beam splitter 4, it passes through Wollaston prism 5 along the +X direction and is received by photodiodes 6 and 7.

[0040] When the receiver mounted on the object under test exhibits a roll angle, the position of the light received by the four-quadrant photodiodes 10 and 11 will change accordingly. The roll angle of the object under test can be measured based on the difference in position between the two photodiodes and the received light position. This method has high accuracy, but due to environmental factors, there may be an angle between the two collimated beams incident on the four-quadrant photodiodes 10 and 11, introducing roll angle measurement error. Photodiodes 6 and 7 are designed to compensate for this error. By adjusting the polarization beam splitter 14 to set the vibration direction of its incident light, when the receiver exhibits a roll angle, the polarization vector of the incident light changes accordingly. After being split by the beam splitter 4, the light intensity illuminating photodiodes 6 and 7 changes accordingly. Therefore, the roll angle can be measured and the angle between the two collimated beams incident on the four-quadrant photodiodes 10 and 11 can be calculated based on the light intensity relationship on photodiodes 6 and 7. Finally, the calculated angle is used to compensate for the roll angle measured by the four-quadrant photodiodes 10 and 11, achieving high-precision roll angle measurement.

[0041] This embodiment also provides a roll angle measurement method with self-compensated dual-beam angle, based on the above-mentioned roll angle measurement device, including:

[0042] (1) First, roll angle measurement is performed based on the dual collimated beams directed at the four-quadrant photodiodes 10 and 11: As shown in Figure 2, the two collimated beams are respectively irradiated on the four-quadrant photodiodes 10 and 11. When the receiver generates a roll angle ε dz At that time, the four-quadrant photodiodes 10 and 11 respectively produce a vertical straightness δ in the Y-axis direction. yr and δ yl The light spot is offset by -Δy in the Y-axis direction of photodiodes 10 and 11 in the four quadrants, respectively. QD1 and -Δy QD2 The distance between the two collimated beams along the X-axis is denoted as L, and the roll angle error measured by this method is denoted as ε. droll Then the roll angle can be expressed as:

[0043]

[0044] (2) The roll angle measurement method based on dual collimated beams has high accuracy, but when the laser drifts, the angle between the two collimated beams also changes, thus introducing roll angle measurement error. Assume there is an angular drift θ between the two collimated beams. up This will cause a shift Δε in the Y-axis direction of photodiodes 10 and 11 in the four quadrants. droll :

[0045]

[0046] The roll angle measurement error Δε caused by visible laser angle drift drollThe error introduced by the linear variation with the measurement distance D in long-distance measurements cannot be ignored and needs to be compensated.

[0047] (3) Next, the roll angle is measured based on polarization: such as Figure 3 As shown, firstly, the vibration direction of the incident light from the beam splitter 4 is set by adjusting the polarizing beam splitter 14. Figure 1 When the X-axis is parallel, the receiver generates a roll angle ε. dz The light intensity measured by photodiodes 6 and 7 is:

[0048]

[0049] in The light intensity measured by photodiode 6 is... The light intensity measured by photodiode 7 is I0, the total intensity of the two beams is I0, and the light intensity difference ΔI is:

[0050]

[0051] Since the roll angle is small, based on the principle of equivalent infinitesimals, the roll angle ε calculated by photodiodes 6 and 7 can be obtained. proll for:

[0052]

[0053] (4) Finally, the roll angle ε measured in step (1) droll Perform compensation calibration: After starting calibration, the roll angle measurement value of the dual collimated beam structure in step (1) is ε. droll The measured value of the roll angle of the polarization structure in step (3) is ε. proll The receiver is moved to a certain position, and continuous measurement is performed over a time period t seconds, with one result obtained per second, denoted as ε. proll,t Then, the average of these t measured results is taken to eliminate random errors, resulting in...

[0054]

[0055] According to formulas (1) and (6), measurements were taken at different locations A and B at the receiving end to obtain ε. droll_A , and ε droll_B , The angle drift θ is calculated after differentiation. up for:

[0056]

[0057] Where D AB Let θ be the distance between points A and B. upThe introduced roll angle measurement error increases with the increase of the measurement distance. Within the measurement range, the larger the distance between A and B, the greater the roll angle measurement error. The larger the value, the smaller the relative error, and the more accurate the result. Therefore, the measured roll angle ε after compensation and calibration... cdroll for:

[0058]

[0059] Where D is the distance between the transmitter and receiver, i.e., the measurement distance.

[0060] Specifically, this embodiment conducted a roll angle measurement experiment based on the above-described apparatus and method. The results of the roll angle measurement method without polarization compensation based on dual collimated beams (referred to as Method 1) and the roll angle measurement method with self-compensated dual-beam angle provided by this invention (referred to as Method 2) within the measurement distance range of 0.75m to 2m are shown in the table below.

[0061]

[0062] Experimental results show that, within the measurement range of 0.75 meters to 2 meters, the measurement error of Method 2 is reduced by an average of 88.97% compared to Method 1. The high-precision, miniaturized roll angle measurement device and method with self-compensation of dual-beam angle provided by this invention can effectively improve the accuracy of roll angle measurement based on dual collimated beams.

[0063] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A roll angle measuring device with self-compensating dual-beam included angle, characterized in that, It consists of a transmitter and a receiver. The transmitter includes a laser (1), a first beam splitter (2), a second beam splitter (4), a third beam splitter (9), a first reflector (3), a second reflector (8), a Wollaston prism (5), a first four-quadrant photodiode (10), a second four-quadrant photodiode (11), a first photodiode (6), and a second photodiode (7). The receiving end includes a polarizing beam splitter (14), a third reflecting mirror (13), a first right-angle prism (12), and a second right-angle prism (15); The laser emitted from the laser (1) is split into two beams, transmitted and reflected, by the first beam splitter (2). The transmitted beam from the first beam splitter (2) is directed to the first reflecting mirror (3), and after being reflected by the first reflecting mirror (3), it is directed to the third beam splitter (9), and then split into two beams, transmitted and reflected, by the third beam splitter (9). The reflected beam from the third beam splitter (9) reaches the second reflecting mirror (8) and is reflected to the first right-angle prism (12). After being reflected twice by the first right-angle prism (12), it is received by the first four-quadrant photodiode (10). The transmitted beam from the third beam splitter (9) is directed to the second right-angle prism (8). The light from the first beam splitter (2) is reflected twice by the second right-angle beam splitter (15) and then received by the second four-quadrant photodiode (11). The reflected light from the first beam splitter (2) is split into two beams, transmitted light and reflected light, by the second beam splitter (4). The reflected light from the second beam splitter (4) is received by the first photodiode (6) and the second photodiode (7) after passing through the Wollaston prism (5). The transmitted light from the second beam splitter (4) passes through the polarizing beam splitter (14) and the third reflector (13) in sequence, and is reflected by the third reflector (13) and then returns to the second beam splitter (4) along the original path.

2. The roll angle measuring device with self-compensating dual-beam included angle according to claim 1, characterized in that, The receiving end is installed on the object under test. According to the first quadrant photodiode (10) and the second quadrant photodiode (11), when the receiving end generates a roll angle, the polarization vector of the incident light changes accordingly. After being split by the second beam splitter (4), the light intensity illuminating the first photodiode (6) and the second photodiode (7) changes accordingly. The roll angle is measured by the light intensity relationship on the first photodiode (6) and the second photodiode (7), and the angle between the double collimated beams incident on the first quadrant photodiode (10) and the second quadrant photodiode (11) is calculated. Finally, the roll angle measured by the first quadrant photodiode (10) and the second quadrant photodiode (11) is compensated by the calculated angle, so as to realize the roll angle measurement.

3. A roll angle measurement method with self-compensated dual-beam angle, based on the roll angle measurement device with self-compensated dual-beam angle as described in any one of claims 1-2, characterized in that, include: (1) Roll angle measurement is performed based on the dual collimated beams directed at the first four-quadrant photodiode (10) and the second four-quadrant photodiode (11); when the receiver generates a roll angle ε dz At that time, the first four-quadrant photodiode (10) and the second four-quadrant photodiode (11) respectively generate vertical straightness δ in the Y-axis direction. yr and δ yl The light spot is offset by -Δy in the Y-axis direction of the first and fourth quadrant photodiode (10) and the second and fourth quadrant photodiode (11), respectively. QD1 and -Δy QD2 The distance between the two collimated beams along the X-axis is denoted as L, and the measured roll angle error is denoted as ε. droll The roll angle is then expressed as: (2) Introduce roll angle measurement error; assume that there is an angular drift θ in the double collimated beam. up The two four-quadrant photodiodes are offset by Δε in the Y-axis direction. droll for: Roll angle measurement error Δε caused by laser angle drift droll It varies linearly with the measurement distance D; (3) Roll angle measurement based on polarization: By adjusting the polarizing beam splitter (14), the vibration direction of the incident light from the second beam splitter (4) is set to be parallel to the X-axis. Then, when the receiver generates a roll angle ε pz At that time, the light intensities measured by the first photodiode (6) and the second photodiode (7) were respectively: in It is the light intensity measured by the first photodiode (6). I0 is the light intensity measured by the second photodiode (7), and I0 is the total intensity of the two beams. The intensity difference ΔI between the two beams is: By equating the roll angle to an infinitesimal, we obtain the roll angle ε measured by the first photodiode (6) and the second photodiode (7). proll for: (4) The roll angle ε measured in step (1) droll Compensation calibration: After starting the calibration, the roll angle measured by the first four-quadrant photodiode (10) and the second four-quadrant photodiode (11) in step (1) is ε. droll In step (3), the roll angle measured by the first photodiode (6) and the second photodiode (7) is ε. proll The receiver is moved to a certain position, and continuous measurement is performed over a time period t seconds, with one result obtained per second, denoted as ε. proll,t Then, the average of these t measured results is taken to eliminate random errors, resulting in... Based on the above formulas (1) and (6), measurements are taken at different locations A and B at the receiving end to obtain ε. droll_A , and ε droll_B , The angle drift θ is calculated after differentiation. up for: Where D AB The distance between points A and B; the measured roll angle ε after compensation and calibration. cdroll for: Where D is the distance between the transmitter and receiver, i.e., the measurement distance.

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