CN109579776B - High-precision anti-interference large working distance self-collimation device and method - Google Patents
High-precision anti-interference large working distance self-collimation device and method Download PDFInfo
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Abstract
本发明属于精密测量技术领域和光学工程领域，具体涉及高精度抗干扰大工作距自准直装置与方法；该装置由光源、第一偏振片、反馈成像单元、第一透射式准直镜、组合式反射镜、第二偏振分光镜、角漂移量反馈测量单元以及波前畸变反馈测量单元组成。该方法通过增加角漂移量反馈测量单元和波前畸变反馈测量单元，分别测量并实时补偿自准直光束受空气扰动引入的角漂移和波前畸变，减小自准直光束在复杂空气环境、长工作距离下受空气扰动的影响，提高自准直仪的工作距离、稳定性和抗干扰能力；此外，该装置实现对空气扰动引入的角漂移量和波前畸变相互分离并分别测量，提高测量与补偿精度，进而具有在同等使用环境和距离下，提高自准直仪测量精度的优势。
The invention belongs to the technical field of precision measurement and the field of optical engineering, in particular to a high-precision anti-interference large working distance self-collimation device and method; the device comprises a light source, a first polarizer, a feedback imaging unit, a first transmission collimating mirror, It is composed of a combined reflecting mirror, a second polarization beam splitter, an angular drift feedback measurement unit and a wavefront distortion feedback measurement unit. By adding an angular drift feedback measurement unit and a wavefront distortion feedback measurement unit, the method measures and compensates in real time the angular drift and wavefront distortion of the self-collimated beam caused by air disturbance, respectively, so as to reduce the self-collimated beam in complex air environment, Under the influence of air disturbance at long working distance, the working distance, stability and anti-interference ability of the autocollimator are improved; in addition, the device realizes the separation and measurement of the angular drift and the wavefront distortion introduced by the air disturbance. The measurement and compensation accuracy has the advantage of improving the measurement accuracy of the autocollimator under the same use environment and distance.
Description
Technical Field
The invention belongs to the technical field of precision measurement and the field of optical engineering, and particularly relates to a high-precision anti-interference large-working-distance auto-collimation device and method.
Background
With the increasing level of technology, manufacturing and machining show a trend of high precision and large size, wherein precise small angle measurement is an important component. The instrument commonly used for precise small-angle measurement is a laser autocollimator taking an optical autocollimation principle as a core, and plays an important role in precise and ultra-precise positioning detection, manufacturing and installation of high-end large-scale equipment and attitude detection of large scientific engineering instruments.
The laser autocollimator has the advantages of high resolution, high precision, long measuring distance, high measuring speed, non-contact, convenient adjustment and movement and the like, and has very wide application in the fields.
In the precise and ultra-precise positioning detection, the laser autocollimator is combined with optical elements such as a plane mirror and a polygon prism to carry out angle measurement, flatness measurement, straightness measurement and the like, and the resolution can reach 0.1 arc second to 0.001 arc second; in the manufacturing and installation process of high-end large equipment, such as the manufacturing precision of large aircraft parts, the installation and torsional deformation of hull parts and the like, the laser autocollimator is matched with a cooperative target for measurement, and the measurement distance can reach several meters or even tens of meters; in the attitude detection of a large scientific engineering instrument, if a laser autocollimator is used for detecting the yaw angle and the pitch angle of an astronomical telescope in real time, measuring the initial azimuth angle before rocket launching and the like, the laser autocollimator is required to carry out remote measurement work in outdoor, workshop and other non-laboratory complex environments.
At present, the measurement requirements of precise small angles are not limited in detection rooms and laboratory environments, the distance measurement is not only short-distance measurement, and a laser autocollimator capable of carrying out real-time high-precision remote measurement in manufacturing factories, processing workshops and even field environments is needed. The method has higher requirements on performance indexes of the laser autocollimator, such as precision, measuring distance, stability, stray light interference resistance, external air disturbance resistance and the like.
As shown in fig. 1, the conventional autocollimator includes a light source 1, a transmissive collimator 2, a target reflector 3, and a feedback imaging unit 4; the light beam emitted by the light source 1 is collimated into parallel light beams by the transmission type collimating mirror 2 and then enters the target reflecting mirror 3; the light beam reflected by the target reflector 3 is a measuring light beam, the feedback imaging unit 4 collects displacement information of the imaging light spot, and the yaw angle and the pitch angle of the target reflector 3 can be obtained through calculation. Under the structure, if the target reflector 3 is far away from the transmission type collimating mirror 2, the reflected light beam has extra angle information, namely angle drift, due to the existence of air disturbance, and meanwhile, the wavefront of the reflected light beam is distorted, so that the quality of an imaging light spot is poor, the energy of the light spot is uneven, the position of the light spot detected by the photoelectric sensor is inaccurate, and the measurement precision and the measurement stability are reduced. Therefore, the laser autocollimator of the conventional structure has the following problems:
firstly, the use environment of the laser autocollimator cannot be too severe, otherwise, the long-distance transmission of the light beam in the air can cause unstable light beam transmission, so that the measurement result is unstable, and the autocollimator cannot realize stable measurement in an environment with complicated air conditions;
secondly, the measurement distance between the target reflector and the laser autocollimator cannot be too far, otherwise, the autocollimator cannot realize high-precision measurement in an environment with complicated air conditions due to angular drift and wavefront distortion in the light beam transmission process caused by the influence of air disturbance.
The two problems enable the traditional autocollimator to realize high-precision and high-stability measurement only in a stable air environment at a short distance.
Disclosure of Invention
Compared with the traditional autocollimator, the high-precision anti-interference large-working-distance autocollimator can measure under a more complex air environment condition, and improves the measurement precision, anti-interference capability and stability of the laser autocollimator in the measurement process.
The purpose of the invention is realized as follows:
the high-precision anti-interference large-working-distance auto-collimation device comprises a light source, a first polaroid, a feedback imaging unit, a first transmission type collimating mirror, a combined reflector, a second polarizing beam splitter, an angle drift amount feedback measuring unit and a wavefront distortion feedback measuring unit.
The first polaroid and the feedback imaging unit are arranged between the light source and the first transmission type collimating mirror, and the feedback imaging unit comprises a first feedback spectroscope and a first photoelectric sensor arranged at the focus of the first transmission type collimating mirror; the measuring light beam reflected by the semi-reflecting and semi-transmitting mirror is transmitted by the second polarizing beam splitter and the first transmission type collimating mirror in sequence, reflected by the first feedback beam splitter, and the imaging light spot displacement information is collected by the first photoelectric sensor. Under the condition that the reflecting surface of the half-reflecting and half-transmitting mirror is vertical to the optical axis, the converged light spot is imaged at the central position of the first photoelectric sensor.
The combined reflector is composed of a half-reflecting and half-transmitting mirror, a quarter-wave plate and a pyramid prism. The light beam obtained by reflection of the reflecting surface of the semi-reflecting and semi-transmitting mirror is a measuring light beam, the polarization direction is not changed, and the feedback imaging unit acquires imaging light spot displacement information; the light beam transmitted by the semi-reflecting and semi-transmitting mirror is used as a reference light beam, is transmitted by the quarter-wave plate, is reflected by the pyramid prism, is transmitted by the quarter-wave plate and the semi-reflecting and semi-transmitting mirror, changes in polarization direction, is opposite to the original direction in transmission direction, and collects light spot information through the incident angle drift amount feedback measurement unit and the wavefront distortion feedback measurement unit.
The angle drift amount feedback measuring unit consists of a third feedback spectroscope, a second transmission type collimating mirror and a second photoelectric sensor arranged on the focal plane of the second transmission type collimating mirror; the wavefront distortion feedback measuring unit consists of a fourth feedback reflecting mirror with an angle adjusting unit and a third wavefront sensor. The angle drift amount feedback measuring unit and the wavefront distortion feedback measuring unit jointly form a disturbance feedback measuring unit.
The reference beam reflected by the pyramid prism changes the polarization direction because of passing through the quarter-wave plate twice, is reflected by the second polarizing beam splitter, then sequentially passes through the beam splitting reflection of the third feedback beam splitter and the transmission of the second transmission type collimating mirror, and the light beams are converged and the light spot displacement information is measured by the second photoelectric sensor; and the other beam splitting light beam is transmitted by the third feedback spectroscope, reflected by the fourth feedback reflector and collected by the third wavefront sensor. Under the condition that the reflecting surface of the half-reflecting and half-transmitting mirror is vertical to the optical axis, the converged light spot is imaged at the central position of the second photoelectric sensor; meanwhile, the optical axis of the light beam reflected by the fourth feedback reflecting mirror is vertical to the plane of the third wavefront sensor.
The angle adjusting unit is arranged on the fourth feedback reflecting mirror and comprises a first angle deflection driver, a second angle deflection driver, an angle adjusting mirror frame and a universal shaft. The first angle deflection driver is perpendicular to the line connecting the second angle deflection driver and the cardan shaft.
The high-precision anti-interference large-working-distance auto-collimation method realized on the high-precision anti-interference large-working-distance auto-collimation device comprises the following steps of:
step a, placing a combined reflector on a measured object, and aligning a laser autocollimator to a reflecting surface of a half-reflecting and half-transmitting mirror of the combined reflector;
step b, lighting the light source, feeding back the imaging unit to work, if:
(1) if the light spot is imaged outside the detection area of the first photoelectric sensor, adjusting the position and the direction of the laser autocollimator to enable the light spot to be imaged in the detection area of the first sensor, and entering the step c;
(2) if the light spot is imaged in the detection area of the first photoelectric sensor, entering the step c;
c, feeding back the work of an imaging unit to obtain displacement information delta x1 and delta y1 of the measuring beam imaging light spot on the first photoelectric sensor, wherein the displacement information is deviated from the center; meanwhile, the disturbance feedback measurement unit works to obtain displacement information delta x2 and delta y2 of the reference beam imaging light spot on the second photoelectric sensor of the angle drift amount feedback measurement unit, and reference beam wavefront data w0 measured by a third wavefront sensor in the wavefront distortion feedback measurement unit;
d, driving the first angle deflection driver and the second angle deflection driver by using the angle adjusting unit according to the delta x2, the delta y2 and the w0, enabling the reflected light beam of the fourth feedback reflector to vertically enter the third wavefront sensor, and obtaining reference light beam wavefront data w1 measured by the third wavefront sensor again;
e, calculating the yaw angle and the pitch angle delta theta and delta theta of the measured object and the combined reflecting mirror according to the delta x1, the delta y1, the delta x2, the delta y2 and the w1
Wherein Δ θ ═ f1(Δ x1, Δ x2, w1),
f1, f2 represent two functions.
Has the advantages that:
compared with the traditional autocollimator, the invention is additionally provided with an angle drift amount feedback measuring unit and a wavefront distortion feedback measuring unit. The structure enables the laser autocollimator to work under the conditions of complicated air environment and long working distance in a non-laboratory. For errors introduced by air disturbance, the light beam angle drift error can be obtained through measurement of the second photoelectric sensor, errors caused by wavefront distortion through measurement of the third wavefront sensor are resolved and compensated in real time, and the result obtained through calculation of data measured by the first photoelectric sensor is obtained. Therefore, the invention can obviously increase the anti-interference capability of the laser autocollimator, effectively reduce the influence caused by air disturbance, and improve the anti-interference capability and the measurement and compensation precision of the instrument.
In addition, the invention has the following technical advantages:
firstly, the combined reflector is selected, so that the laser autocollimator receives the measuring beam and also receives the reference beam reflected by the corner cube prism. The reference beam imaging light spot comprises angle drift and wavefront distortion information caused by air disturbance influence in the transmission process, and both the angle drift and the wavefront distortion information have influence on the displacement information of the detection imaging light spot; in addition, under the condition of small-angle deflection of the combined reflecting mirror, the spatial positions of the reference light path and the measurement light path are basically coincident, and the air disturbance on the reference light path and the measurement light path is basically the same. Therefore, the method can realize compensation of disturbance errors of the measurement result of the measurement beam by measuring the displacement information and the wavefront distortion information of the imaging light spot of the reference beam, and has the advantage of improving the measurement precision of the laser autocollimator under the same working distance.
Secondly, by adding a disturbance feedback measurement unit, the air disturbance error separation of the measurement result of the laser autocollimator is realized; according to the autocollimation measurement principle, the measuring beam returns and carries the angle information of the deflection of the measured object, and meanwhile, due to the influence of air disturbance, the measuring beam also comprises angular drift and wavefront distortion information. The angle drift amount feedback measuring unit can measure the angle drift error, and realize the measurement and separation of the macroscopically measured light beam return direction error caused by air disturbance; the wavefront distortion feedback measurement unit of the system can detect wavefront information, and measurement and separation of spot displacement measurement errors caused by poor imaging spot quality and uneven energy due to wavefront distortion are achieved. Therefore, the invention realizes the measurement and separation of errors introduced by air disturbance by adding the disturbance feedback measurement unit, and can improve the measurement precision of the laser autocollimator under the same working environment and distance.
And thirdly, a fourth feedback reflector in the wavefront distortion feedback measuring unit is provided with an angle adjusting unit, the unit can control the deflection of the reflector through an angle deflection driver according to the angle drift data and the wavefront distortion data obtained by measurement, so that the reflected reference beam is normally incident to the wavefront sensor, the influence of the integral inclination of the beam generated by the angle drift on the wavefront measurement is avoided, the error caused by the angle drift and the wavefront distortion is further realized, and the measurement compensation precision of the laser autocollimator is favorably improved. In addition, in the angle adjusting unit, a fourth feedback reflecting mirror is fixed on the angle adjusting mirror frame, and a connecting line of the first angle deflection driver and the universal shaft is vertical to a connecting line of the second angle deflection driver and the universal shaft; the two connecting lines are perpendicular to each other, complex decoupling operation is not needed in angle control, the calculation process is simplified, and the response speed is improved.
Drawings
Fig. 1 is a schematic structural diagram of a conventional auto-collimation angle measurement system.
Fig. 2 is a schematic structural diagram of a first embodiment of the high-precision anti-interference large-working-distance auto-collimation device of the present invention.
Fig. 3 is a schematic structural view of the angle adjusting unit.
Fig. 4 is a schematic structural diagram of a second embodiment of the high-precision anti-interference large-working-distance auto-collimation device of the present invention.
In the figure: the device comprises a light source 1, a transmission type collimating mirror 2, a feedback imaging unit 4, a first feedback spectroscope 41, a first photoelectric sensor 42, a combined type reflector 5, a half-reflection half-transmission mirror 51, a quarter-wave plate 52, a pyramid prism 53, a first polarizing film 6, a second polarizing spectroscope 7, an angular drift amount feedback measuring unit 8, a second photoelectric sensor 81, a second transmission type collimating mirror 82, a third feedback spectroscope 83, a wavefront distortion feedback measuring unit 9, a third wavefront sensor 91, a fourth feedback reflector 92, an angle adjusting unit 93, a first angle deflection driver 931, a second angle deflection driver 932, a universal shaft 933, an angle adjusting mirror holder 934, a second transmission type collimating mirror 94 and a second polarizing film 95.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The following describes in further detail specific embodiments of the present invention with reference to the accompanying drawings.
Detailed description of the preferred embodiment
The embodiment is an embodiment of a high-precision anti-interference large-working-distance auto-collimation device.
The high-precision anti-interference large-working-distance auto-collimation device of the embodiment has a schematic structural diagram as shown in fig. 2. The auto-collimation device comprises a light source 1, a first polaroid 6, a feedback imaging unit 4, a first transmission type collimating mirror 2, a combined type reflecting mirror 5, a second polarizing beam splitter 7, an angle drift amount feedback measuring unit 8 and a wavefront distortion feedback measuring unit 9.
The first polarizer 6 and the feedback imaging unit 4 are arranged between the light source 1 and the first transmissive collimator lens 2. The feedback imaging unit 4 includes a first feedback beam splitter 41 and a first photosensor 42. The first photoelectric sensor 42 is located on the focal plane of the first transmission collimator lens 2, and the optical axis is perpendicular to the sensor detection plane area center position.
The combined reflector 5 comprises a half-reflecting and half-transmitting mirror 51, a quarter-wave plate 52 and a corner cube 53.
The angle drift amount feedback measuring unit 8 consists of a third feedback spectroscope 83, a second transmission type collimating mirror 82 and a second photoelectric sensor 81 arranged on the focal plane of the second transmission type collimating mirror 82, and the optical axis of the unit is vertical to the detection center of the second photoelectric sensor 81; the wavefront distortion feedback measuring unit 9 is composed of a fourth feedback mirror 92, an angle adjusting unit 93, and a third wavefront sensor 91. The fourth feedback mirror 92 is fixed to the angle adjusting unit 93. The angle drift amount feedback measuring unit 8 and the wavefront distortion feedback measuring unit 9 jointly form a disturbance feedback measuring unit.
The measurement principle of this embodiment is as follows:
the light beam emitted by the light source 1 is transmitted by the first polaroid 6 to become linearly polarized light, and is transmitted by the first feedback spectroscope 41 and collimated by the first transmission collimating mirror 2 to become parallel light; the parallel light is transmitted by the second pbs 7 and then enters the reflective surface of the transflective mirror 51 of the combined reflector 5, and at this time, the light beam is divided into a reflected light beam and a transmitted light beam: the reflected light beam is a measuring light beam, the transmission direction is changed, the polarization direction is not changed, so that the reflected light beam can sequentially pass through the second polarization beam splitter 7, the first transmission type collimating mirror 2 for transmission and the first feedback beam splitter 41 for reflection, and the incident first photoelectric sensor 42 acquires imaging light spot displacement information delta x1 and delta y 1; the transmitted beam is a reference beam, continues to propagate forwards, and is transmitted through the quarter-wave plate 52, reflected by the corner cube 53, transmitted through the quarter-wave plate 52 and the half-reflecting and half-transmitting mirror 51 in sequence. As can be seen from the reflection characteristic of the corner cube prism, the propagation direction of the light beam is opposite to the original direction, and is independent of the deflection angle of the combined reflector 5. And because of passing through the quarter-wave plate 52 twice, the beam polarization direction is perpendicular to the original polarization direction. The beam is thus reflected by the second pbs 7 as a reference beam into the disturbance feedback measurement unit.
The reference beam reflected by the second pbs 7 is first split into two reference beams by the third pbs 83, the angle of incidence drift feedback measuring unit 8: one path is a reflected reference beam, is transmitted by the second transmission type collimating mirror 82 and is converged on the second photoelectric sensor 81 to acquire imaging light spot displacement information delta x2 and delta y 2; the other path is a transmission reference beam, is reflected by a fourth feedback reflector 92 and enters a third wavefront sensor 91 to acquire reference beam wavefront information w 0; meanwhile, the angle adjusting unit 93 adjusts the angle of the fourth feedback mirror 92 by driving the first angle deflection driver 931 and the second angle deflection driver 932, so that the light beam is normally incident on the third wavefront sensor 91, and the wavefront information w1 of the reference beam is obtained by re-measurement, thereby avoiding the influence of the integral wavefront inclination caused by the angular drift on the wavefront distortion measurement. The yaw angle and pitch angle Δ θ of the combined reflector 5 and the surface of the measured object can be obtained by calculation as f1(Δ x1, Δ x2, w1),
f1, f2 represent two functions.
The measurement procedure of this example is as follows:
step a, placing a combined reflector 5 on a measured object, and aligning a laser autocollimator to a reflecting surface of a half-reflecting and half-transmitting mirror 51 of the combined reflector 5;
step b, lighting the light source 1, and feeding back the imaging unit 4 to work, if:
(1) if the light spot is imaged outside the detection area of the first photoelectric sensor 42, adjusting the position and the direction of the laser autocollimator to image the light spot in the detection area of the first photoelectric sensor 42, and entering step c;
(2) if the light spot is imaged in the detection area of the first photoelectric sensor 42, entering the step c;
step c, feeding back the operation of the imaging unit 4 to obtain displacement information Δ x1 and Δ y1 of the measuring beam imaging light spot on the first photoelectric sensor 42 deviating from the center; meanwhile, the disturbance feedback measurement unit works to obtain displacement information delta x2 and delta y2 of the reference beam imaging light spot off-center on the second photoelectric sensor 81 of the angle drift amount feedback measurement unit 8; obtaining reference beam wavefront data w0 measured by the third wavefront sensor 91 of the wavefront distortion feedback measuring unit 9;
step d, according to Δ x2, Δ y2 and w0, driving the first angular deflection driver 931 and the second angular deflection driver 932 by the angle adjustment unit 93, so that the reflected light beam of the fourth feedback mirror 92 vertically enters the third wavefront sensor 91, and obtaining reference beam wavefront data w1 measured by the third wavefront sensor 91 again;
e, calculating the yaw angle and the pitch angle delta theta and delta theta of the measured object and the combined reflecting mirror 5 according to the delta x1, the delta y1, the delta x2, the delta y2 and the w1
Wherein Δ θ ═ f1(Δ x1, Δ x2, w1),
f1, f2 represent two functions.
It should be noted that according to the structure and measurement principle of the conventional laser autocollimator device, the yaw and pitch angles Δ θ 1 and Δ θ 32 of the combined reflector 5 can be calculated by using the displacement information Δ x1 and Δ y1 of the measurement beam imaging spot reflected by the half-reflecting and half-transmitting mirror 51
However, when the laser autocollimator works in a large working distance and non-laboratory ideal air environment, due to the existence of air disturbance, the measuring beam not only contains the information of the measured angle, but also contains the information of angle drift and beam wavefront distortion, and the information can cause errors in the measuring result and influence the measuring stability and measuring precision of the instrument.
Therefore, on the basis of the structure of the traditional laser autocollimator device, the invention can realize the measurement of the error caused by the angle drift and wave surface distortion caused by air disturbance by measuring the light beam transmitted by the semi-reflecting and semi-transmitting mirror 51, wherein the light beam returns in the original path and does not contain the information of the yaw angle and the pitch angle of the combined reflector 5. The angle drift error can be measured by the angle feedback measuring device 8, and the error caused by wave surface distortion can be measured by the wavefront feedback measuring device 9, so that error separation and measurement are realized. Through a compensation algorithm, error compensation is carried out on the combined reflector 5 yaw angle and pitch angle information obtained by calculating the imaging light spot displacement information of the measuring light beam, the influence of angle drift and wave surface distortion on the final measuring result is reduced, the measuring result is more accurate, the anti-interference capability of the instrument under the same working distance is improved, and the measuring precision of the instrument is improved.
Detailed description of the invention
The embodiment is a second embodiment of the high-precision anti-interference large-working-distance auto-collimation device.
The high-precision anti-interference large-working-distance auto-collimation device of the embodiment has a schematic structural diagram as shown in fig. 4. In the first embodiment, the second transmissive collimating mirror 82 is removed, and the third transmissive collimating mirror 94 and the second polarizer 95 are added. The optical path structures of the angular drift amount feedback measuring unit 8 and the wavefront distortion feedback measuring unit 9 are adjusted, the volumes of the optical path and the optical element are reduced, and the whole structure is compact and stable and has the design advantage of portability.
The auto-collimation device of the embodiment comprises a light source 1, a first polarizing film 6, a feedback imaging unit 4, a first transmission type collimating mirror 2, a combined reflecting mirror 5, a third feedback beam splitter 83, an angular drift amount feedback measuring unit 8 and a wavefront distortion feedback measuring unit 9.
The first polarizer 6 and the feedback imaging unit 4 are arranged between the light source 1 and the first transmissive collimator lens 2. The feedback imaging unit 4 comprises a first feedback beam splitter 41 and a first photosensor 42 arranged at the focal plane of the first transmissive collimator lens 2. The first photoelectric sensor 42 is located on the focal plane of the first transmission collimator lens 2, and the optical axis is perpendicular to the sensor detection plane area center position.
The combined reflector 5 comprises a half-reflecting and half-transmitting mirror 51, a quarter-wave plate 52 and a corner cube 53.
The angle drift amount feedback measuring unit 8 consists of a second polarization beam splitter 7 and a second photoelectric sensor 81 arranged on the focal plane of the first transmission type collimating mirror 2; the wavefront distortion feedback measuring unit 9 is composed of a third wavefront sensor 91, a fourth feedback reflecting mirror 92, an angle adjusting unit 93, a third transmissive collimating mirror 94, and a second polarizing plate 95. The angle drift amount feedback measuring unit 8 and the wavefront distortion feedback measuring unit 9 jointly form a disturbance feedback measuring unit.
The second pbs 7 is disposed between the first feedback beamsplitter 41 and the first photosensor 42; the third feedback beam splitter 83 is disposed between the first feedback beam splitter 41 and the first transmissive collimating mirror 2. The third transmissive collimator 94 and the second polarizer 95 are disposed between the third wavefront sensor 91 and the fourth feedback reflector 92, the optical axis is perpendicular to the geometric center of the detection plane area where the optical axis is located, the focal plane of the third transmissive collimator 94 coincides with the focal plane of the first transmissive collimator 2, and the two collimators are on the same side of the focal plane.
The measurement principle of this embodiment is as follows:
the light beam emitted by the light source 1 is transmitted by the first polaroid 6 to become linearly polarized light, transmitted by the first feedback spectroscope 41 and the third feedback spectroscope 83, and collimated into parallel light by the first transmission type collimating mirror 2; the parallel light is incident on the reflecting surface of the half mirror 51 of the combined reflector 5, and the light beam is divided into a reflected light beam and a transmitted light beam: the reflected light beam is a measuring light beam, and the polarization direction of the measuring light beam cannot be changed, so that the light beam returns to pass through the first transmission type collimating mirror 2, the third feedback beam splitter 83 for transmission, the first feedback beam splitter 41 for reflection, the second polarization beam splitter 7 for transmission and the incident first photoelectric sensor 42 for collecting imaging light spot displacement information delta x1 and delta y1 in sequence; the yaw and pitch angles of the combined mirror 5 and the object to be measured are Δ θ 1 ═ f1(Δ x1),
wherein f1 and f2 represent two functions. The transmitted beam is a reference beam, and will continue to propagate forward, and pass through the quarter-wave plate 52, the corner cube 53 for reflection, the quarter-wave plate 52, and the half-reflecting and half-transmitting mirror 51 in turn. The reflection characteristic of the pyramid prism shows that the propagation direction of the light beam is opposite to the original direction and is irrelevant to the deflection angle of the combined reflector 5; while the beam polarization direction changes as a result of passing twice through quarter-wave plate 52. The beam is thus incident as a reference beam into the disturbance feedback measurement unit.
The returned reference beam is transmitted by the first transmission type collimating mirror 2, split-reflected by the third feedback beam splitter 83, reflected by the fourth feedback reflecting mirror 92, collimated into parallel light by the third transmission type collimating mirror 94, passes through the second polarizing film 95 with the same polarization direction, and enters the third wavefront sensor 91 to collect the wavefront distortion information w0 of the reference beam; the other divided reference beam is transmitted by the third feedback beam splitter 83, then reflected by the first feedback beam splitter 41, reflected by the second polarization beam splitter 7, and converged at the second photosensor 81 to acquire imaging light spot displacement information Δ x2 and Δ y 2;
through Δ x2, Δ y2 and w0 obtained by measurement, the angle of the fourth feedback reflecting mirror 92 is adjusted by driving the first angle deflection driver 931 and the second angle deflection driver 932 by the angle adjusting unit 93, so that the reference beam reflected by the fourth feedback reflecting mirror 92 is collimated by the third transmissive collimating mirror 94 and then vertically enters the third wavefront sensor 91, and at this time, the wavefront information w1 of the reference beam is obtained by re-measurement, thereby avoiding the influence of the whole wavefront inclination caused by angular drift on wavefront distortion measurement. The sum of the yaw angle and the pitch angle delta theta of the combined reflector 5 and the surface of the measured object can be obtained through calculation
Where Δ θ ═ f4(Δ θ 1, Δ x2, w1),
f4, f5 represent two functions.
The measurement procedure of this example is as follows:
step a, placing a combined reflector 5 on a measured object, and aligning a laser autocollimator to a reflecting surface of a half-reflecting and half-transmitting mirror 51 of the combined reflector;
step b, lighting the light source 1, and feeding back the imaging unit 4 to work, if:
(1) if the light spot is imaged outside the detection area of the first photoelectric sensor 42, adjusting the position and the direction of the laser autocollimator to enable the light spot to be imaged in the detection area of the first photoelectric sensor 42, and entering the step c;
(2) if the light spot is imaged in the detection area of the first photoelectric sensor 42, entering the step c;
step c, feeding back the operation of the imaging unit 4 to obtain displacement information Δ x1 and Δ y1 of the measuring beam imaging light spot on the first photoelectric sensor 42 deviating from the center; the yaw and pitch angles of the combined mirror 5 and the object to be measured are Δ θ 1 ═ f1(Δ x1),
wherein f1, f2 represent two functions;
d, working the disturbance feedback measurement unit to obtain displacement information delta x2 and delta y2 of the reference beam imaging light spot off-center on the second photoelectric sensor 81 of the angular drift amount feedback measurement unit 8; obtaining reference beam wavefront data w0 measured by the third wavefront sensor 91 of the wavefront distortion feedback measuring unit 9;
step e, according to Δ x2, Δ y2 and w0, driving the first angular deflection driver 931 and the second angular deflection driver 932 by the angle adjustment unit 93, so that the reflected light beam of the fourth feedback mirror 92 vertically enters the third wavefront sensor 91, and obtaining reference beam wavefront data w1 measured by the third wavefront sensor 91 again;
step f, according to the delta theta 1,
Δ x2, Δ y2 and w1, and yaw and pitch angles Δ θ and Δ θ of the measured object and the combined mirror 5 are calculated
Where Δ θ ═ f4(Δ θ 1, Δ x2, w1),
f4, f5 represent two functions.
What needs to be added to the above embodiments is:
firstly, a disturbance feedback measurement unit is added on the basis of the structure of the traditional laser autocollimator, and the measurement of beam angle drift and wavefront distortion information caused by air disturbance influence is realized. By adopting the idea of error separation, the disturbance feedback measurement unit respectively measures the measurement errors introduced by air disturbance according to different formation mechanisms and detection modes, so that the accurate measurement and compensation of the measurement result errors can be realized. The disturbance feedback measurement unit can reduce the influence of environmental factors such as air disturbance on the measurement result of the laser autocollimator, and obviously improve the measurement accuracy, stability, measurement distance and other indexes of the laser autocollimator.
Secondly, in the angular drift amount feedback measuring unit, displacement information Δ x2 and Δ y2 of the imaging light spot off-center are collected as compensation data by using a second photoelectric sensor 81, and the detection process is similar to the conventional autocollimator measurement process except that the detection object is a reference beam. The measurement result has direct and obvious influence on the error compensation of the measurement result of the laser autocollimator. But also has the problems of unsatisfactory spot imaging quality, uneven spot energy and measurement error caused by wavefront distortion. Therefore, when the autocollimator measurement results are compensated by Δ x2 and Δ y2, the autocollimator measurement results are compensated by the measurement results of the third wavefront sensor 91, and the compensated results are closer to the angular drift error of the light beam.
Third, the reference beam passes through a plurality of optical elements during the process of returning to the laser autocollimator and entering the third wavefront sensor 91, which causes the wavefront distortion information of the beam to change again during this process. After the optical system is built, the optical element is not changed. Therefore, the difference between the wavefront distortion when the reference beam is incident on the laser autocollimator and the wavefront distortion when the reference beam is incident on the third wavefront sensor 91 can be regarded as constant, and is a systematic error. Before the experiment is carried out, the combined type reflecting mirror 5 can be close to the position close to the first transmission type collimating mirror 2, the reflecting surface of the semi-reflecting and semi-transmitting mirror 51 is perpendicular to the optical axis, the wave front information of the reference light beam at the moment is detected by the third wave front sensor 91, and the wave front information can be regarded as a reference datum plane of wave front measurement when no air disturbance exists. The wavefront measurement information when the measurement is subsequently carried out is wavefront distortion information relative to the reference datum.
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