CN103940348A - Device and method for detecting movement errors of working platform in multiple degrees of freedom - Google Patents

Abstract

The invention discloses a device and method for multi-degree-of-freedom detection of workbench motion errors. The reflected light of the invention is reflected on three reflectors fixed on the workbench through an optical path adjustment reflector, and is sequentially reflected by the three reflectors. , return to the optical path to adjust the reflector, and reflect to the second beam splitter, enter the beam expander after being reflected by the second beam splitter, and project on the detector; the transmitted light enters the beam expander after being transmitted by the second beam splitter , projected onto the detector. The two beams of light interfere on the detector, and the adjustment of the shape of the interference fringe and the measurement of the phase shift can realize the measurement of the deflection and motion displacement of the worktable; the present invention can be used to measure the swing angle, pitch angle and The synchronous real-time measurement of the axial movement displacement enables real-time compensation through the measurement results to eliminate the influence of movement errors, thereby improving the measurement accuracy and manufacturing accuracy. The measurement range of the angle is within ±3mrad, which meets the measurement requirements of the workbench.

Description

Device and method for multi-degree-of-freedom detection of workbench motion error

the

technical field

The invention relates to a workbench multi-degree-of-freedom detection device, which can realize the synchronous measurement of the workbench's swing angle, pitch angle and linear motion displacement.

the

Background technique

The precision table is a key component of surface topography measurement and precision machining, and its movement accuracy directly determines the measurement accuracy and machining accuracy. Therefore, research and design are of great significance to the real-time on-line measurement method of the angle deviation and line deviation of the work table.

Among the current measurement methods for the motion error of the workbench, the high-precision measurement method has few degrees of freedom or can only measure a single degree of freedom; in the multi-degree-of-freedom measurement method, the measurement accuracy is low, or a combined measurement method is used The measurement accuracy is high, but the cost is high and the volume is bulky.

There are several existing worktable motion error measurement methods: one is to use laser interferometry, that is, an interferometric method based on the principle of laser interference, which uses various combinations of optical components on the workbench, through the reflection and refraction of laser light etc. to form the optical path difference related to the movement error of the worktable, and then calculate the phase difference caused by the optical path difference to obtain the movement error of the worktable. Since the laser wavelength is used as the standard, the measurement accuracy can meet higher requirements, but generally it can only meet the requirements of a single degree of freedom. When multi-degree-of-freedom measurement is required, multiple similar laser interferometers must be used at the same time, which leads to system structure too large. The second is to measure the two-dimensional angle based on the principle of laser collimation, directly use the four-quadrant detector or CCD to obtain the center of gravity of the light spot, and measure the straightness of the guide rail or worktable. In addition to the need for strict collimation of the laser beam, this method is difficult to meet the high-precision requirements due to the influence of the laser spot divergence angle and beam drift; the third is other multi-sensor combination measurement methods, including the use of capacitors, gratings and other sensors to measure different parts of the workbench to calculate its motion error. Generally, this method has a complex structure and is only suitable for the research and analysis of the motion error of a special workbench. Moreover, the installation requirements are very high, the environmental requirements are also very strict, and the cost is relatively high.

the

Contents of the invention

In order to solve the above technical problems, the present invention provides a device and method for multi-degree-of-freedom detection of worktable motion errors, which are used for synchronous detection of precision worktable motion errors.

The technical solution adopted by the device of the present invention is: a device for multi-degree-of-freedom detection of workbench motion errors, which is controlled by a host computer; it is characterized in that it includes a laser light source unit, a laser light path direction adjustment and interference modulation unit, and a three-sided mirror Measuring the target surface unit and the photoelectric receiving and converting unit; a part of the laser light generated by the laser light source unit is used as a reference optical path light to pass through the laser optical path direction adjustment and interference modulation unit in a straight line, and then projected to the photoelectric receiving and converting unit In the unit, the other part is used as the light of the measuring optical path—after being sequentially reflected by the laser optical path direction adjustment and interference modulation unit, the three-mirror measuring target surface unit, and the laser optical path direction adjustment and interference modulation unit, it is projected onto the described In the photoelectric receiving and converting unit, the measurement optical path light and the reference optical path light interfere in the photoelectric receiving and converting unit; The receiving and conversion unit is connected to control the adjustment of the laser light path direction and the interference modulation unit and the photoelectric receiving and conversion unit; the three-mirror measuring target surface unit is fixed on the workbench, with the workbench Movement and deflection change the optical path and direction of the optical path. At the same time, the laser optical path direction adjustment and interference modulation unit adjusts the optical path direction in real time according to the shape of the interference fringe signal to ensure that there is a relatively fixed angle between the measurement optical path and the reference optical path. Ensure that the shape of the interference fringe signal is basically stable; the photoelectric receiving and converting unit is used to complete the photoelectric receiving, fringe counting and fringe shape recognition of the interference fringe signal, and control the adjustment of the laser light path direction and the interference modulation unit through the recognition result, while the upper The machine also completes the adjustment of the direction of the laser optical path, the drive control of the interference modulation unit and the modulation of the optical path difference, and realizes the measurement of multiple degrees of freedom on the workbench.

Preferably, the laser light source unit includes a high-frequency stable laser and a beam expander collimator, and the laser light generated by the high-frequency stable laser is input to the laser light path direction adjustment after being passed through the beam expander collimator. In the interferometric modulation unit; so as to ensure that the laser has high frequency stability, long coherence length, small divergence angle of the spot output by the beam expander collimator, and the spot diameter should be greater than 5mm to meet the requirements of wide enough interference fringes.

Preferably, the laser light path direction adjustment and interference modulation unit includes a first beam splitter, a second beam splitter, a three-degree-of-freedom PZT device, an optical path adjustment mirror or a deflection mirror, a beam expander, and a deflection driver. One end of the yaw driver is connected to the host computer, and the other end is connected to the three-degree-of-freedom PZT device, which is used to control the three-degree-of-freedom PZT device to perform three-degree-of-freedom adjustment. The laser Part of the laser light generated by the light source unit passes through the first beam splitter, the second beam splitter and the beam expander in a straight line as a reference optical path and then projects into the photoelectric receiving and conversion unit, and the other part is used as a measurement optical path respectively through After the first beam splitter, optical path adjustment mirror or deflection mirror, three-sided mirror measuring target surface unit, optical path adjustment mirror or deflection mirror and the second beam splitter are sequentially reflected, after passing through the beam expander projected into the photoelectric receiving and converting unit. The three-degree-of-freedom PZT device can complete the adjustment of θ _x , θ _y and z directions, and the adjustment ranges are ±3mrad, ±3mrad and 30μm respectively.

Preferably, the three-degree-of-freedom PZT device is composed of a two-dimensional deflection device and a one-dimensional displacement device. The two-dimensional yaw realizes the swing and pitch angle adjustment of the optical path to ensure that the direction of the incident optical path coincides with the normal line of the middle mirror during the measurement process; the one-dimensional displacement drive is along the normal direction of the mirror to modulate the optical path difference and facilitate dynamic interference fringes collection.

As a preference, the three-mirror measuring target surface unit is composed of three plane mirrors, the angle between the middle plane mirror and the incident or exit plane mirrors on both sides is 120°, and the light of the measurement optical path is reflected by the three plane mirrors sequentially and then projected onto the In the laser light path direction adjustment and interference modulation unit; and during the measurement process, it is required that the normal line of the intermediate mirror coincides with the light path. The three-sided mirror is fixed on the workbench as the target surface and placed in the optical path of the measuring arm of the laser interferometer system. When the workbench swings, pitches and moves axially, the beam direction and optical path difference of the returned measuring light path change accordingly. , while changing the shape and phase shift of the interference fringes. The method of reflecting the light path through three-sided mirrors is different from the reflection method of conventional corner cubes. It retains the deflection information of the worktable, and at the same time avoids the problem of returning along the original light path after reflection by a single plane mirror, so that the measurement system does not need Under the condition of optical separation, the laser feedback phenomenon is avoided.

Preferably, the photoelectric receiving and conversion unit includes a detector, a photoelectric conversion circuit, an A/D sampling circuit, and a shaping and fine resolution circuit, and the A/D sampling circuit and the shaping and fine resolution circuit are connected in parallel , connected in series with the host computer, detector and photoelectric conversion circuit, used to receive the light projected by the laser optical path direction adjustment and interference modulation unit, and perform photoelectric conversion and sampling, the sampled signal undergoes differential shaping, and performs Subdivision counting of interference fringes, using ellipse fitting or trigonometric function method to realize the identification of interference fringe shape.

Preferably, the detector adopts a symmetrical four-quadrant detector in the shape of a square.

As a preference, the photoelectric conversion circuit is completed by four NPN triodes and four resistors, using four transistors with the same magnification and four resistors of the same size to complete by current amplification to ensure that the detector signals have the same of magnification.

Preferably, the shaping and fine resolution circuit is composed of a differential circuit, a comparison circuit and a fine resolution circuit to complete the counting process of the interference fringes to obtain the displacement in the Z direction.

Preferably, the A/D sampling circuit is composed of a high-speed synchronous A/D conversion circuit, and the synchronous speed is above 100k.

The technical solution adopted by the method of the present invention is: a method for multi-degree-of-freedom detection of workbench motion error, characterized in that it comprises the following steps:

Step 1: Before the measurement, debug the device to ensure that the incident light of the measurement light path is parallel to the outgoing light, that is, the incident light is parallel to the normal line of the middle mirror of the three-sided mirror measurement target unit, and then adjust the laser light path direction adjustment and The interference modulation unit ensures that a small angle is formed between the measuring light and the reference light, and that suitable interference fringes appear on the photoelectric receiving and converting unit, so that the difference of the differential signals of the interference fringes is as close as possible to 90°, which is convenient for the interference fringe signal Subdivided orientation and counting processing;

Step 2: Start the workbench, start the measurement, drive the laser optical path direction adjustment and the Z-direction movement of the interference modulation unit within a wavelength, and at the same time as the interference modulation is performed, the photoelectric signal detected by the photoelectric receiving and converting unit is differentiated on the one hand. Processing to obtain the original signal used for counting; on the other hand, the accurate signal phase difference is calculated by ellipse fitting or sine-cosine function multiplication algorithm, which is used for the calculation of the adjustment parameter of the deflection angle of the optical path direction;

Step 3: Through the calculated phase difference and deflection angle parameters, on the one hand, the deflection angle is displayed, and on the other hand, the laser light path direction adjustment and the interference modulation unit are controlled to adjust the angle so that the size of the interference fringe is not affected by the movement error of the workbench.

The present invention is characterized in that:

(1) According to the principle that the deflection and movement of the three-sided mirror with the worktable affect the beam direction and optical path, resulting in the change of the shape and phase shift of the interference fringe, the measurement of the multi-degree-of-freedom of the workbench is realized;

(2) The method of reflecting the light path through three-sided mirrors is different from the reflection method of conventional corner cubes. It retains the deflection information of the worktable, and at the same time avoids the problem of returning along the original light path after reflection by a single plane mirror, making the measurement system Under the condition of no need for optical separation, the laser feedback phenomenon is avoided;

(3) Using the two-dimensional yaw device, according to the feedback processing of the shape of the interference fringe, the optical path is adjusted in real time to ensure that the shape of the interference fringe is basically stable and does not affect the simultaneous measurement of large-scale motion displacement;

(4) The modulation of the optical path difference is realized by using the piezoelectric micro-displacement device, which improves the accuracy of the phase extraction of the fringe signal;

(5) The symmetrical four-quadrant detector is used to receive the fringe signal to realize the extraction of the shape of the fringe signal, and its sampling and processing speed is far superior to that of the CCD.

Compared with the prior art, the present invention can be used in precision surface measurement and precision machining to measure the sway angle, pitch angle and axial movement displacement of the worktable in real time synchronously, so that real-time compensation can be performed through the measurement results to eliminate motion errors influence, thereby improving the measurement accuracy and manufacturing accuracy, the measurement range of the angle of the present invention is within the range of ±3mrad, which meets the measurement requirements of the workbench.

the

Description of drawings

Fig. 1: is the device structure diagram of the embodiment of the present invention.

Fig. 2: is the flow chart of the method of the embodiment of the present invention.

the

Detailed ways

In order to facilitate those of ordinary skill in the art to understand and implement the present invention, the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the implementation examples described here are only used to illustrate and explain the present invention, and are not intended to limit this invention.

Please see Fig. 1, the technical solution adopted by the device of the present invention is: a device for detecting motion errors of a worktable with multiple degrees of freedom, controlled by a host computer; including a laser light source unit 1, a laser light path direction adjustment and interference modulation unit 2, The three-sided mirror measures the target surface unit 3 and the photoelectric receiving and converting unit 4; the laser light source unit 1 includes a high-frequency stable laser 101 and a beam expander collimator 102, and the laser optical path direction adjustment and interference modulation unit 2 includes a first beam splitter 201, The second beam splitter 202, the three-degree-of-freedom PZT device 203, the optical path adjustment mirror or the yaw mirror 204, the beam expander 205, and the yaw driver 206, one end of the yaw driver 206 is connected to the host computer, and the other end is connected to the three-degree-of-freedom The PZT device 203 is connected to control the three-degree-of-freedom PZT device 203 to perform three-degree-of-freedom adjustment. The three-degree-of-freedom PZT device 203 is composed of a two-dimensional deflection and a one-dimensional displacement device, and a three-sided mirror measures the target surface unit 3 Composed of three plane mirrors, the angle between the middle plane mirror and the incident or exit plane mirrors on both sides is 120°, the photoelectric receiving and converting unit 4 includes a detector 401, a photoelectric conversion circuit 402, an A/D sampling circuit 403 and shaping and fine resolution Circuit 404; after the laser light generated by the high-frequency stable laser 101 passes through the beam expander collimator 102, a part of it passes through the first beam splitter 201, the second beam splitter 202 and the beam expander 205 as a reference optical path, and then projects into the detector 401 , the other part is used as the measurement optical path respectively—through the first beam splitter 201, the optical path adjustment reflector or the deflection mirror 204, the three-sided reflector measuring the three-plane mirror of the target surface unit 3, the optical path adjustment reflector or the deflection mirror 204 and the second After the beam splitter 202 is sequentially reflected, it is projected into the detector 401 after passing through the beam expander 205; after the A/D sampling circuit 403 is connected in parallel with the shaping and fine resolution circuit 404, it is connected with the host computer, the detector 401 and the photoelectric conversion circuit 402 Connected in series to receive the light projected by the beam expander 205, and perform photoelectric conversion and sampling, the sampled signal is differentially shaped, and the interference fringes are subdivided and counted, and the shape of the interference fringes is recognized by ellipse fitting or trigonometric function method .

The detector 401 of the present embodiment adopts a symmetrical 'square' four-quadrant detector, and the photoelectric conversion circuit 402 is completed by four NPN triodes and four resistors, utilizing four transistors with the same magnification and four resistors of the same size, It is completed by means of current amplification to ensure that the signal of the detector 401 has the same amplification factor. The shaping and fine resolution circuit 404 is composed of a differential circuit, a comparison circuit and a fine resolution circuit to complete the counting process of interference fringes and obtain the Z direction displacement. , The A/D sampling circuit 403 is composed of a high-speed synchronous A/D conversion circuit, and the synchronous speed is above 100k.

The technical scheme adopted by the method of the present invention is: a method for detecting a multi-degree-of-freedom motion error of a workbench, comprising the following steps:

Step 1: Before formal measurement, try to ensure that the incident ray of the measurement light path is parallel to the outgoing ray, that is, the incident ray is as parallel as possible to the normal of the three-sided combined measurement intermediate mirror. Then adjust the angle of the second beam splitter 202 to ensure that a small angle is formed between the measuring light and the reference light, and suitable interference fringes appear on the detector, so that the difference of the differential signals of the interference fringes is as close as possible to 90°, which is convenient Fine resolution and counting processing of fringe signals;

Step 2: Start the workbench and start measuring. Drive the three-degree-of-freedom PZT device 203 to move in the Z direction within one wavelength, while performing interference modulation. On the one hand, the photoelectric signal detected by the four-quadrant detector 401 is sent to the differential circuit of the shaping and fine resolution circuit 404 for differential processing to obtain the original signal for counting; on the other hand, it is sent to the high-speed synchronous A signal of the A/D sampling circuit 403 The /D conversion circuit calculates the accurate signal phase difference through ellipse fitting or multiplication of sine and cosine functions, and is used for the calculation of the adjustment parameters of the deflection angle of the optical path direction;

Step 3: Through the calculated phase difference and deflection angle parameters, on the one hand, display the deflection angle, and on the other hand, control the three-degree-of-freedom PZT device 203, adjust the angle of the deflection mirror, so that the size of the interference fringe is not affected by the motion error of the workbench .

Although this article uses a lot of laser light source unit 1, laser light path direction adjustment and interference modulation unit 2, three-sided mirror measurement target unit 3, photoelectric receiving and conversion unit 4, high-frequency stable laser 101, and beam expander collimator 102 , a first beam splitter 201, a second beam splitter 202, a three-degree-of-freedom PZT device 203, an optical path adjustment mirror or a yaw mirror 204, a beam expander 205, a yaw driver 206, a detector 401, a photoelectric conversion circuit 402, A/D sampling circuit 403 and shaping and subdivision circuit 404 are terms, but the possibility of using other terms is not excluded. These terms are only used to describe the essence of the present invention more conveniently, and it is against the spirit of the present invention to interpret them as any additional limitation.

It should be understood that the above-mentioned descriptions for the preferred embodiments are relatively detailed, and should not therefore be considered as limiting the scope of the patent protection of the present invention. Within the scope of protection, replacements or modifications can also be made, all of which fall within the protection scope of the present invention, and the scope of protection of the present invention should be based on the appended claims.

Claims (11)

1. the device that working table movement error multiple degrees of freedom detects, passes through PC control, it is characterized in that: comprise that LASER Light Source unit (1), the adjustment of laser optical path direction are measured target surface unit (3) with interference modulations unit (2), thrihedral reflector and photoelectricity receives and converting unit (4), a laser part for described LASER Light Source unit (1) generation is as passing with reference to light path light straight line after the described adjustment of laser optical path direction and interference modulations unit (2), project in described photoelectricity reception and converting unit (4), another part one is adjusted and interference modulations unit (2) once described laser optical path direction respectively as optical path light, thrihedral reflector is measured target surface unit (3), after the adjustment of laser optical path direction and interference modulations unit (2) order-reflected, project in described photoelectricity reception and converting unit (4), described optical path light and reference path light produce and interfere in described photoelectricity reception and converting unit (4), described host computer is adjusted with interference modulations unit (2) and photoelectricity and is received and be connected with converting unit (4) respectively at described laser optical path direction, receives and converting unit (4) with interference modulations unit (2) and photoelectricity for controlling described laser optical path direction adjustment, described thrihedral reflector is measured target surface unit (3) and is fixed on described worktable, with motion and the deflection of worktable, change light path light path and direction, described laser optical path direction is adjusted with interference modulations unit (2) according to interferometric fringe signal shape simultaneously, adjust in real time optical path direction, ensure to have relatively-stationary angle between optical path and reference path, thereby ensure that interferometric fringe signal shape is basicly stable, described photoelectricity receives with converting unit (4) for completing photoelectricity reception, fringe count and the shape of stripes identification of interferometric fringe signal, and adjust and interference modulations unit (2) by the output control laser optical path direction of identification, host computer also completes the adjustment of laser optical path direction and the driving control of interference modulations unit (2) and the modulation of optical path difference simultaneously, realizes the multivariant measurement of worktable.

2. the device that working table movement error multiple degrees of freedom according to claim 1 detects, it is characterized in that: described LASER Light Source unit (1) comprises high frequency stabilized laser (101) and beam-expanding collimation device (102), the laser that described high frequency stabilized laser (101) produces is input in the described adjustment of laser optical path direction and interference modulations unit (2) after described beam-expanding collimation device (102).

3. the device that working table movement error multiple degrees of freedom according to claim 1 detects, it is characterized in that: described laser optical path direction is adjusted with interference modulations unit (2) and comprised the first light splitting piece (201), the second light splitting piece (202), the PZT device (203) of Three Degree Of Freedom, light path is adjusted catoptron or beat mirror (204), beam expanding lens (205) and beat driver (206), described beat driver (206) one end is connected with described host computer, the other end is connected with the PZT device (203) of described Three Degree Of Freedom, carry out Three Degree Of Freedom adjustment for the PZT device (203) of controlling described Three Degree Of Freedom, the laser part that described LASER Light Source unit (1) produces is as passing described the first light splitting piece (201) with reference to light path straight line, after the second light splitting piece (202) and beam expanding lens (205), project in described photoelectricity reception and converting unit (4), another part distinguishes one once described the first light splitting piece (201) as optical path, light path is adjusted catoptron or beat mirror (204), thrihedral reflector is measured target surface unit (3), light path is adjusted after catoptron or beat mirror (204) and the second light splitting piece (202) order-reflected, after described beam expanding lens (205), project in described photoelectricity reception and converting unit (4).

4. the device that working table movement error multiple degrees of freedom according to claim 3 detects, is characterized in that: the PZT device (203) of described Three Degree Of Freedom is made up of two-dimentional beat and one dimension displacement mobile device.

5. the device and method that working table movement error multiple degrees of freedom according to claim 1 detects, it is characterized in that: described thrihedral reflector is measured target surface unit (3) and combined by three level crossings, mid-plane mirror and both sides incident or exit plane mirror angle are 120 °, described optical path light, after three level crossings reflect successively, projects in the described adjustment of laser optical path direction and interference modulations unit (2).

6. the device that working table movement error multiple degrees of freedom according to claim 1 detects, it is characterized in that: described photoelectricity receives with converting unit (4) and comprises detector (401), photoelectric switching circuit (402), A/D sample circuit (403) and shaping and segmentation sensing circuit (404), after described A/D sample circuit (403) and shaping and segmentation sensing circuit (404) are connected in parallel, with described host computer, detector (401) and photoelectric switching circuit (402) are connected in series, adjust for receiving described laser optical path direction the light projecting with interference modulations unit (2), and carry out opto-electronic conversion post-sampling, the signal of sampling is through difference shaping, carry out the subdivision and count of interference fringe, application ellipse fitting or trigonometric function method realize the identification of shape of interference fringe.

7. the device that working table movement error multiple degrees of freedom according to claim 6 detects, is characterized in that: described detector (401) adopts symmetrical ' matrix pattern ' 4 quadrant detector.

8. the device that working table movement error multiple degrees of freedom according to claim 6 detects, it is characterized in that: described photoelectric switching circuit (402) is completed by four NPN triodes and four resistance, utilize four triodes and four resistance that size is identical that enlargement factor is consistent, the mode of amplifying by electric current completes, and ensures that detector (401) signal has identical enlargement factor.

9. the device that working table movement error multiple degrees of freedom according to claim 6 detects, it is characterized in that: described shaping is made up of difference channel, comparator circuit and segmentation sensing circuit with segmentation sensing circuit (404), complete the counting processing of interference fringe, obtain Z-direction displacement.

10. the device that working table movement error multiple degrees of freedom according to claim 6 detects, is characterized in that: described A/D sample circuit (403) is made up of high-speed synchronous A/D change-over circuit, more than synchronous speed reaches 100k.

11. 1 kinds of devices that utilize profit to require the working table movement error multiple degrees of freedom described in 1 to detect carry out the method that working table movement error multiple degrees of freedom detects, and it is characterized in that, comprise the following steps:

Step 1: before measurement, the device that debugging is described, ensure that optical path incident ray is parallel to emergent ray, it is the intermediate mirror normal that incident ray is parallel to thrihedral reflector measurement target surface unit (3), then adjusting described laser optical path direction adjusts and interference modulations unit (2), between guarantee measurement light and reference ray, form a very little angle, photoelectricity receives the interference fringe suitable with the upper appearance of converting unit (4), the differing of differential signal of interference fringe tried one's best near 90 °, be convenient to like this subdivide with distinguished and count processing of interferometric fringe signal;

Step 2: start described worktable, start to measure, driving laser optical path direction is adjusted the motion of the Z-direction in a wavelength with interference modulations unit (2), when carrying out interference modulations, photoelectricity receives the photosignal of surveying with converting unit (4) and carries out difference processing on the one hand, obtains the original signal for counting; Calculate signal phase difference accurately by ellipse fitting or sin cos functions phase multiplication algorithm on the other hand, adjust the calculating of parameter for optical path direction deflection angle;

Step 3: by phase differential and the deflection angle parameter calculated, show deflection angle on the one hand, control on the other hand laser optical path direction and adjust and interference modulations unit (2), adjust angle, make the size of interference fringe not be subject to the impact of working table movement error.