CN113720279B - Nanoradian-scale three-dimensional angle measurement method and device based on spatial light modulation - Google Patents

Abstract

The invention belongs to the technical field of precision measurement and the field of optical engineering, and in particular relates to a method and a device for measuring a three-dimensional angle of nanoradian level based on spatial light modulation. It consists of a mirror, a turning mirror, a transmissive spatial light modulator, a collimating objective lens group, an area array CCD, a four-quadrant position detector, a fixed plane mirror and a reflective target; this method gives the reflective target asymmetry in the direction of the optical axis , so that the measuring beam carries the information of the pitch angle and yaw angle of the measured object, and is sensitive to the change of the roll angle of the measured object, so that the instrument device has the ability to detect the three-dimensional angle change of the measured object; because the present invention uses the collimating objective lens The group greatly improves the focal length of the objective lens, so it has the technical advantage that the angular limit resolution reaches the nanoradian level under the same measurement range; it uses a convex lens and a multi-slit aperture, and uses a four-quadrant position detector and a transmission-type spatial light modulation. The drift feedback of the device improves the stability of the system to the order of ten nanoradians, thereby solving the problem that the beam drift limits the limit resolution of the autocollimator. In addition, the system device designed by the present invention has the technical advantages of small volume, high measurement accuracy and high measurement frequency response.

Description

Method and device for three-dimensional angle measurement at nano-arc level based on spatial light modulation

technical field

The invention belongs to the technical field of precision measurement, and in particular relates to a method and device for measuring three-dimensional angles at the nano-arc level based on spatial light modulation.

Background technique

In the fields of precision measurement technology, optical engineering, cutting-edge scientific experiments, and high-end precision equipment manufacturing, there is an urgent need for high-resolution, high-precision, and high-stability self-collimation angle measurement technology in a large working range. It supports the development of technology and equipment in the above fields.

In the field of precision measurement technology and instruments, the combination of autocollimator and circular grating can measure any line angle; the combination of autocollimation technology and polyhedral prism can measure surface angle and circular division; the maximum working distance is from several meters Up to hundreds of meters; resolution from 0.1 arcsecond to 0.01 arcsecond.

In the field of optical engineering and cutting-edge scientific experiments, the combination of an autocollimator and two circular gratings that are perpendicular to each other can measure the spatial angle; Measurement of axis angle or parallelism. The angular working range is from tens of arcseconds to tens of arcminutes.

In the field of cutting-edge scientific experimental devices and high-end precision equipment manufacturing, the use of autocollimators can measure the angular rotation accuracy of cutting-edge scientific experimental devices and high-end precision equipment rotary motion benchmarks, and measure the spatial straight line accuracy of linear motion benchmarks and the parallelism of pairwise motion benchmarks. degree and verticality.

Self-collimation technology has the advantages of non-contact, high measurement accuracy, and convenient use, and has been widely used in the above fields.

A traditional autocollimator is shown in Figure 1. The device includes a laser light source 1, a first convex lens 41, a first beam splitter 2, and an image sensor 3; Incident to the reflective surface of the measured object 51 ; the light beam reflected from the reflected surface of the measured object 51 is collected and imaged by the image sensor 3 . Under this structure, the light beam reflected from the surface of the measured object 51 only carries the spatial angle information of the measured object's two axes; At the same time, due to the large drift of the laser light source, the instability of the measurement seriously affects the limit resolution of the measurement. These conditions limit that when the device measures the spatial angle information of the measured object, it cannot measure the angle information of the measured object rotating around the optical axis, but can only measure the angle information of the other two axes; at the same time, the device is measuring the measured object. When measuring the spatial angle information of an object, it is difficult to break through the resolution bottleneck of 0.003 arc seconds (ten nano-rad scale).

In summary, the system has the following three problems:

First, since the reflective target of the autocollimator is only sensitive to the spatial angle information of the two axes of the measured object, the measuring beam does not carry the roll angle information of the rotation around the optical axis, so the device does not have the ability to measure the three-dimensional angular information of the object space ;

Second, due to the short focal length of the collimating objective lens group of the autocollimator and the low limit displacement resolution of traditional displacement sensors in a large range, it is difficult for this device to achieve a high angular resolution of 0.001 arc seconds (nano-arc scale);

Third, the laser light source with traditional autocollimation technology has beam drift. The angular drift and flat drift of the beam seriously affect the stability of the autocollimator, which in turn limits the ultimate resolution of the autocollimator. After the laser light source is collimated by the convex lens, the collimation accuracy can only reach the order of 10 ^-7 arcs (hundreds of nano-arcs) due to the existence of its drift. The noise caused by the instability of the light source seriously limits the improvement of the ultimate resolution of the autocollimator.

Therefore, while the traditional autocollimation technology does not have the ability to measure three-dimensional angle information, it cannot achieve high angular resolution at the nano-rad scale within the traditional measurement range.

Contents of the invention

Aiming at the problem that the traditional self-collimation angle measurement device cannot achieve the high angle resolution of nano-arc level in the traditional measurement range and does not have the ability to measure three-dimensional angle information, the present invention discloses a nano-arc measure based on spatial light modulation Level three-dimensional angle measurement method and device.

This method uses a four-quadrant position detector as a feedback detection module at the light source output end to detect the drift of the light source in the device in real time and with high precision; uses the spatial light modulator as a feedback execution module, according to the measured The drift of the light source is controlled by closed-loop feedback in real time, and the light spot emitted by the light source is always controlled at the center of the four-quadrant position detector. At the same time, the spatial amplitude distribution of the light intensity of the light source is programmable, thereby directly reducing the drift of the light source and improving The stability of the light intensity of the light source in the spatial distribution. Experiments show that this method can control the flat drift and angular drift of the light source to ten nano-rad levels in real time, and solve the problem that the limit resolution of the autocollimator is limited by the drift of the beam;

At the same time, the method utilizes the collimating objective lens group to expand the focal length of the collimating objective lens of the angle measuring device to 3-4 times, thereby increasing the limit angular resolution of the overall system to the nano-rad scale. Experiments show that this method can achieve an angular resolution of one thousandth of an arcsecond in the range of 300 arcseconds, which solves the problem that the autocollimator cannot achieve high angular resolution of the nano-ardian scale in the traditional measurement range;

The invention utilizes a reflective target and a fixed plane mirror as a three-dimensional corner detection unit in object space. This structural setting endows the reflective target with asymmetry in the direction of the optical axis, so that the measurement beam carries the information of the pitch angle and yaw angle of the measured object, and at the same time is sensitive to the roll angle of the measured object around the optical axis direction, so that The instrument device has the ability to measure the three-dimensional angle of the object's roll angle around the optical axis and the pitch angle and yaw angle of the vertical optical axis, which solves the problem that the autocollimator does not have the ability to measure three-dimensional angle information;

Therefore, compared with the traditional self-collimation measurement device, the invention has the technical advantages of high angle resolution of nano-arc level and three-dimensional angle information measurement capability under the same measurement range.

The purpose of the present invention is achieved like this:

A three-dimensional angle measurement device based on spatial light modulation in the nano-arc range, including a semiconductor laser light source, a first convex lens, a fourth convex lens, a first concave lens, a multi-slit diaphragm, a polarizer, a first beam splitter, a second beam splitter, The first polarization beam splitter, the second polarization beam splitter, the first turning mirror, the second turning mirror, the first area CCD, the second area CCD, the four-quadrant position detector, the plane mirror, the fixed plane mirror and the transmission type spatial light modulator; the semiconductor laser light source is collimated by the fourth convex lens, and after being transmitted by the transmission type spatial light modulator, it is parallel incident on the multi-slit aperture; with the multi-slit aperture as the object plane, the emitted measuring light is polarized the linearly polarized light reflected by the second beam splitter is vertically incident on the four-quadrant position photodetector as the drift amount feedback detection unit; the linearly polarized light transmitted by the second beam splitter passes through the first After turning by the turning mirror and the second turning mirror, it is vertically incident on the collimating objective lens group and collimated into a parallel beam, which is incident on the reflective target; all the way through the first polarizing beam splitter in the reflective target, and incident on the planar reflection of the reflective target On the mirror, the reflected beam is transmitted by the first polarized beam splitter in the reflective target, returns along the original path of the optical path, and is transmitted by the second polarized beam splitter at the measurement end, and then is collected and imaged by the first area array CCD; the other path is reflected by the target Reflected by the first polarized beam splitter in the reflector, it is incident on the fixed plane mirror, and the reflected beam is reflected by the first polarized beam splitter in the reflection target, returns along the original path of the optical path, and then reflected by the second polarized beam splitter at the measuring end The imaging is collected by the second area array CCD;

The transmissive spatial light modulator is used to modulate the measuring light so that the measuring light is vertically incident on the multi-slit aperture;

The multi-slit aperture is a transmissive aperture composed of two sets of three straight line slits with equal distance and equal width. The two sets of straight line slits are perpendicular to each other. The slit diaphragm, so two groups of three parallel, equidistant and equal-width straight-line spots perpendicular to each other are an object of the device, and the beam emitted by it is the measuring light of the device;

or

The multi-slit aperture is a transmissive aperture composed of two groups of four straight line slits with equal distance and equal width. The two sets of straight line slits are perpendicular to each other. The slit diaphragm, so two groups of four parallel equidistant and equal-width straight-line spots perpendicular to each other are an object of the device, and the beam emitted by it is the measuring light of the device;

The polarizer can adjust the polarization direction of the laser light source, and the polarization direction of the light source passing through the polarizer is different from the two mutually perpendicular polarization directions of the first polarization beam splitter in the reflection target. The polarizer can adjust the light intensity of the measurement light spot received by the first area array CCD and the second area array CCD, so that the two channels of the measurement end are consistent;

The reflective target includes a first polarizing beam splitter and a plane reflector, which is installed on the measurement surface of the measured object; and the fixed plane reflective mirror is independent of the reflective target, which is not connected with the reflective target and the measured object, and is fixed on the It is fixed on the same measurement base as the light source, beam splitter, sensor and collimator lens group. When the measured object rotates in a three-dimensional angle, the reflective target rotates with the object in the same three-dimensional angle, while the fixed mirror and other parts of the measuring device are fixed on the measuring base without movement;

The four-quadrant position detector collects the real-time drift of the semiconductor laser light source, corrects the measurement results, and further improves the stability of the system device;

The collimating objective lens group is composed of a first convex lens and a first concave lens, forming a telephoto objective lens group, whose focal length is much larger than that of the first convex lens, thereby improving the limit angle resolution of the autocollimator;

The first turning mirror and the second turning mirror are placed parallel to each other, and both have a fixed small angle with the main optical axis, so that the telephoto optical path of the system device can be folded, thereby reducing the space size of the system.

A method for measuring three-dimensional angles at the nano-arc scale based on spatial light modulation implemented on the above-mentioned nano-arc scale three-dimensional angle measuring device based on spatial light modulation, comprising the following steps:

Step a, fixing the reflective target to the surface of the measured object, placing the fixed reflector so that its mirror surface is parallel to the exit surface of the first polarizing beam splitter in the reflective target;

Step b. Turn on the semiconductor laser light source, adjust the position of the measured object and the fixed reflector, so that the light spots received by the first area array CCD and the second area array CCD are at the center of the sensor, and the position of the fixed reflector is fixed;

Step c. Observe the brightness of the light spots of the first area array CCD and the second area array CCD, and adjust the polarizer rotation angle so that the light intensity received by the two image sensors is consistent;

Step d. When the four-quadrant position detector outputs the spot displacement and drift amounts E1 and E2 of the semiconductor laser light source, the transmissive spatial light modulator adjusts the beam direction of the semiconductor laser light source so that the spot displacement drift E1 and E2 are always 0;

Step e, the reflective target produces a three-dimensional spatial rotation with the measured object, the first surface array CCD outputs the displacement value of the beam spot reflected by the plane mirror in the reflective target, where the distance from the light spot to the center of the sensor is decomposed into S1, S2, and the second surface The array CCD outputs the displacement value of the beam spot reflected by the fixed plane mirror, where the distance between the spot and the center of the image sensor is S3;

Step f, using the displacements S1 and S2 of the first area array CCD light spot, calculate and obtain β and γ according to S1=f tan(2β), S2=f tan(2γ), wherein β and γ are the measured object The angle of clockwise rotation of the y and z axes;

Step g, using the displacement S3 of the second area array CCD light spot, calculate and obtain θ according to S3=f tan (θ), wherein θ is the angle between the return light and the optical axis of the light beam reflected by the first polarizing beam splitter;

Step h, calculate and obtain ɑ according to ɑ=G(θ, β, γ), where ɑ is the angle of clockwise rotation of the measured object around the x-axis, and G represents a function. Finally, the angles α, β, and γ of the clockwise rotation of the measured object around the x, y, and z axes are obtained.

Beneficial effect:

1. Aiming at the problem that the traditional self-collimation angle measurement device does not have high measurement stability, a nano-arc three-dimensional angle measurement method based on spatial light modulation is proposed. This method uses a four-quadrant position detector as a feedback detection module at the light source output end to detect the drift of the light source in the device in real time and with high precision; uses the spatial light modulator as a feedback execution module, according to the measured The drift of the light source is controlled by closed-loop feedback in real time, and the light spot emitted by the light source is always controlled at the center of the four-quadrant position detector. At the same time, the spatial amplitude distribution of the light intensity of the light source is programmable, thereby directly reducing the drift of the light source and improving The stability of the light intensity of the light source in the spatial distribution; finally realize the control of the flat drift and angular drift of the light source to the level of ten nano-rads, and solve the problem that the limit resolution of the autocollimator is limited by the drift of the beam. This is One of the innovative points that the present invention is different from the prior art;

2. Compared with the traditional measuring device, the device of the present invention utilizes the collimating objective lens group to expand the focal length of the collimating objective lens of the angle measuring device to 3-4 times, thereby increasing the limit angular resolution of the overall system to the nano-ardian level. Solve the problem that the autocollimator cannot achieve high angular resolution of nano-arc scale in the traditional measurement range, which is the second innovative point of the present invention that is different from the prior art;

3. In view of the problem that the traditional self-collimation angle measurement device does not have the ability to measure three-dimensional angle information, the present invention uses a reflective target and a fixed plane mirror as a three-dimensional corner detection unit in object space. This structural setting endows the reflective target with asymmetry in the direction of the optical axis, so that the measurement beam carries the information of the pitch angle and yaw angle of the measured object, and at the same time is sensitive to the roll angle of the measured object around the optical axis direction, so that The instrument device has the three-dimensional angle measurement ability of measuring the roll angle of the object around the optical axis and the pitch angle and yaw angle angle of the vertical optical axis, and solves the problem that the autocollimator does not have the ability to measure three-dimensional angle information. This is the difference between the present invention and The third innovation point of the prior art.

In addition, the present invention also has the following several technical advantages:

First, choose the first turning mirror and the second turning mirror to fold the telephoto optical path of the system twice, which reduces the volume of the system device and is more suitable for the on-site measurement environment, while avoiding air fluctuations caused by the oversized system device impact on measurement results;

Second, the multi-slit aperture is selected as the object of the angle measurement device, and two sets of three-stripe light spots on each area array CCD are positioned at the same time to improve the measurement stability of the system, and also improve the measurement accuracy of the angle measurement device;

Third, the fixed plane reflector is selected as the third-dimensional angle sensing device, which has a simple structure and is basically consistent with the sensing principle around the two axes perpendicular to the optical axis, so that the direction around the optical axis and the two axes perpendicular to the optical axis of the present invention The rotation angles in the other two axis directions maintain the high measurement accuracy of the same magnitude.

Description of drawings

Fig. 1 is a schematic structural diagram of a traditional self-collimation angle measuring device.

Fig. 2 is a schematic structural diagram of Embodiment 1 of a nano-arc scale three-dimensional angle measuring device based on spatial light modulation of the present invention.

FIG. 3 is a schematic structural diagram of two kinds of multi-slit diaphragms 8 in the first embodiment.

Fig. 4 is a schematic structural diagram of Embodiment 2 of a nano-arc scale three-dimensional angle measuring device based on spatial light modulation of the present invention.

FIG. 5 is a schematic structural diagram of Embodiment 3 of a nano-radometric three-dimensional angle measuring device based on spatial light modulation in the present invention.

In the figure: 1 laser light source, 2 first beam splitter, 3 image sensor, 4 collimating objective lens group, 41 first convex lens, 42 first concave lens, 43 second concave lens, 44 second convex lens, 45 third convex lens, 5 reflection Target, 51 plane mirror, 52 first polarizing beam splitter, 6 semiconductor laser light source, 7 fourth convex lens, 8 multi-slit diaphragm, 9 polarizer, 10 second polarizing beam splitter, 11 first area array CCD, 12 The second area array CCD, 13 the second beam splitter, 14 four-quadrant position detector, 15 the first turning mirror, 16 the second turning mirror, 17 the fixed plane mirror, 18 the transmissive spatial light modulator.

specific embodiment

The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Specific embodiment one

This embodiment is an embodiment of a three-dimensional angle measurement device based on spatial light modulation.

The structural diagram of the three-dimensional angle measurement device based on spatial light modulation in this embodiment is shown in FIG. 2 . The angle measuring device comprises a first beam splitter 2, a collimating objective lens group 4 (a first convex lens 41, a first concave lens 42), a reflection target 5 (a plane mirror 51, a first polarizing beam splitter 52), a semiconductor laser light source 6, The fourth convex lens 7, the multi-slit diaphragm 8, the polarizer 9, the second polarizing beam splitter 10, the first area array CCD11, the second area array CCD12, the second beam splitter 13, the four-quadrant position detector 14, the first A turning mirror 15 , a second turning mirror 16 , a fixed plane mirror 17 , and a transmissive spatial light modulator 18 .

The semiconductor laser light source 6 is collimated by the second convex lens 7, and after being transmitted by the transmission spatial light modulator 18, it is incident on the multi-slit diaphragm 8 in parallel; with the multi-slit diaphragm 8 as the object surface, the measuring light emitted Transmitted through the polarizer 9; the linearly polarized light reflected by the second beam splitter 13 is vertically incident on the photodetector 14 at the four-quadrant position as a drift feedback detection unit; the linearly polarized light transmitted by the second beam splitter 13 passes through the first After the turning of the first turning mirror 15 and the second turning mirror 16, it is vertically incident on the collimating objective lens group 4 and collimated into a parallel light beam, which is incident on the reflective target 5; all the way through the first polarizing beam splitter 52 in the reflective target 5, the incident On the plane reflector 51 in the reflective target 5, the reflected light beam is transmitted through the first polarizing beam splitter 52 in the reflective target 5, returns along the original path of the optical path, and is transmitted by the second polarizing beam splitter 10 at the measuring end. One side array CCD11 collects imaging; the other way is reflected by the first polarized beam splitter 52 in the reflective target, and is incident on the fixed plane reflector 17. After the reflected light beam is reflected by the first polarized beam splitter 52 in the reflective target, The optical path returns to the original path and is reflected by the second polarizing beam splitter 10 at the measuring end, and then collected and imaged by the second area array CCD12;

The multi-slit aperture 8 is a transmissive aperture composed of two groups of three straight-line slits of equal distance and equal width. The two groups of straight-line slits are perpendicular to each other. Based on the multi-slit diaphragm 8, two groups of three parallel equidistant and equal-width straight-line spots perpendicular to each other are an object of the device, and the light beam emitted by it is the measuring light of the device;

or

The multi-slit aperture 8 is a transmissive aperture composed of two groups of four straight line slits of equal distance and equal width. The two groups of straight line slits are perpendicular to each other. Based on the multi-slit diaphragm 8, two groups of four parallel equidistant and equal-width straight-line spots perpendicular to each other are an object of the device, and the light beam emitted by it is the measuring light of the device;

The transmissive spatial light modulator 18 is placed between the fourth convex lens 7 and the multi-slit diaphragm 8, and is used to modulate the measuring light so that the measuring light is vertically incident on the multi-slit diaphragm 8;

The reflective target 5 includes a first polarization beam splitter 52 and a plane reflector 51, which are installed on the measurement surface of the measured object, so the three-dimensional spatial angle change of the cooperative target 5 is the spatial three-dimensional angular change of the measured object; and The fixed plane mirror 17 is independent of the reflective target, it is not connected with the reflective target 5 and the measured object, and it is fixed on the measurement base;

Described collimating objective lens group 4 is made up of the first convex lens 41 and the first concave lens 42; Conjugate; under the condition that the reflective target 5 does not produce a three-dimensional angle change, the spot centers collected by the first area array CCD11 and the second area array CCD12 are all at the geometric center of the sensor; the four-quadrant position detector 14 is arranged at the second After the four beam splitters 13, collect the real-time drift of the semiconductor laser light source 6;

The first turning mirror 15 and the second turning mirror 16 are placed parallel to each other, and both have a fixed small angle with the main optical axis.

The measurement principle is as follows:

To measure the spatial three-dimensional rotation angle of the measured object, the spatial coordinate system of the three-dimensional rotation angle of the reflective target 5 needs to be defined first: set the optical axis direction as the x-axis, the downward direction as the y-axis, and the outward direction of the vertical reflection target 5 surface as z axis; and define the three-dimensional rotation angles of the reflective target 5 as α, β, and γ that rotate clockwise around the x-axis, y-axis, and z-axis, respectively.

Secondly, the reflective target 5, including the first polarizing beam splitter 52 and the plane reflector 51, is fixed on the surface of the measured object, so the spatial three-dimensional angle change of the reflective target 5 is the spatial three-dimensional angle change of the measured object. The fixed plane reflector 17 is not connected with the reflective target 5, but is fixed on the measurement base.

When the measured object rotates clockwise around the x-axis, y-axis, and z-axis by α, β, and γ angles to generate a three-dimensional angular rotation in space, the reflective target 5 also rotates clockwise around the x-axis, y-axis, and z-axis respectively. The α, β, and γ angles are defined, while the spatial position of the fixed plane reflector 17 remains unchanged.

The four-quadrant position detector 19 measures the drift of the semiconductor laser light source 6 in real time, and the beam spot and the center position of the four-quadrant position detector 14 produce displacement drift E1 and E2 respectively; Displacement drift E1, E2 is always 0.

The light beam incident on the plane reflector 51 in the reflective target 5 is transmitted through the first polarizing beam splitter 52. Since the plane reflector 51 rotates with the three-dimensional angle of the measured object, the light beam reflected by the plane reflector 51 is different from the original light beam. Deflection of 2β, 2γ angles. Consistent with the principle of traditional autocollimator measurement, this beam converges on the first area array CCD11, and the beam spot and the center position of the image sensor generate displacements S1 and S2 respectively.

And satisfy the following relationship, S1-E1=f·tan(2β), S2-E2=f·tan(2γ), f is the focal length of the collimating objective lens group 4 .

Therefore, according to the displacements S1 and S2 between the light spot on the first area array CCD11 and the center position of the sensor, the angles β and γ of the object to be measured around the y-axis and z-axis can be calculated.

The light beam incident on the fixed plane reflector 17 is reflected by the first polarized beam splitter 52. Since the first polarized beam splitter 52 rotates with the three-dimensional angle of the measured object, the light beam reflected by the fixed plane reflector 17 is then passed through the first polarized beam splitter. The polarization beam splitter 52 reflects and deflects the original beam at an angle of θ, and this beam converges on the second area array CCD12, and the beam spot is displaced by S3 from the center position of the sensor.

And satisfy the following relationship, S3-E1=f·tan(θ), f is the focal length of the collimating objective lens group 4 .

According to the spatial geometric relationship, θ=F(ɑ, β, γ), and similarly, ɑ=G(θ, β, γ), where F and G represent two functions respectively.

Therefore, according to the displacement S3 between the light spot on the second area array CCD12 and the center position of the sensor, the space angle θ between this beam and the original beam can be calculated; and then according to the formula ɑ=G(θ, β, γ) and before The β, γ values can be solved to calculate the α angle, so as to obtain the angle α, β, γ angle of the measured object rotating around the x-axis, y-axis, and z-axis, and obtain the spatial three-dimensional rotation angle information of the measured object.

The embodiment of the three-dimensional angle measurement method based on spatial light modulation in this embodiment includes the following steps:

Step a, fixing the reflective target 5 to the surface of the measured object, placing the fixed plane mirror 17 so that its mirror surface is parallel to the exit surface of the first polarizing beam splitter 52 in the reflective target 5;

Step b, turn on the semiconductor laser light source 6, adjust the position of the measured object and the fixed plane reflector 17, so that the light spots received by the first area array CCD11 and the second area array CCD12 are at the center of the sensor, so that the fixed plane reflector 17 fixed position;

Step c, observing the brightness of the light spots of the first area array CCD11 and the second area array CCD12, adjusting the rotation angle of the polarizer 9 so that the light intensity received by the two image sensors is consistent;

Step d, when the four-quadrant position detector 14 outputs the light spot displacement and drift amounts E1 and E2 of the semiconductor laser light source 6, the transmissive spatial light modulator 18 adjusts the beam direction of the semiconductor laser light source 6 so that the light spot displacement and drift amounts E1 and E2 are always is 0;

Step e, the reflective target 5 rotates three-dimensionally with the measured object, and the first area CCD11 outputs the displacement value of the beam spot reflected by the plane reflector in the reflective target, wherein the distance between the light spot and the center of the sensor is decomposed into S1, S2, and the second The area array CCD12 outputs the displacement value of the beam spot reflected by the fixed plane mirror, where the distance between the spot and the center of the image sensor is S3;

Step f, using the displacements S1 and S2 of the light spot of the first area array CCD11, calculate and obtain β and γ according to S1=f tan(2β), S2=f tan(2γ), wherein β and γ are the measured objects around The angle of clockwise rotation of the y and z axes;

Step g, utilizing the displacement S3 of the second area array CCD12 light spot, calculate and obtain θ according to S3=f tan (θ), wherein θ is the angle between the return light and the optical axis of the light beam reflected by the first polarization beam splitter 52;

Step h, calculate and obtain ɑ according to ɑ=G(θ, β, γ), where ɑ is the angle of clockwise rotation of the measured object around the x-axis, and G represents a function. Finally, the angles α, β, and γ of the clockwise rotation of the measured object around the x, y, and z axes are obtained.

The innovation point of the present invention is to use the fourth convex lens 7 to collimate the light emitted by the semiconductor laser light source 6, and simultaneously the multi-slit diaphragm 8 modulates the measuring light, with the multi-slit diaphragm 8 as the object of the system device, Further reduce the influence of angular drift and flat drift;

At the same time, the four-quadrant position detector 14 is used as a feedback detection module to detect the drift amount of the flat drift and angular drift produced by the light source in the device in real time with high precision; the transmissive spatial light modulator 18 is used as a feedback execution module, and according to the measured drift Real-time closed-loop feedback control, the light spot emitted by the light source is always controlled at the center position of the four-quadrant position detector 14; thereby the flat drift and angular drift of the light source are controlled to ten nano-rad levels in real time, and the drift caused by the light beam is solved. The limit resolution of the autocollimator is limited by the amount of light; compared with the technical means of using the deflection mirror as the feedback execution module, the spatial light modulator can not only reduce the output drift of the light source, but also control the spatial amplitude distribution of the light intensity of the light source. Perform programmable control, thereby improving the stability of the light intensity of the light source in the spatial distribution, and further improving the measurement stability of the device of the present invention;

In the present invention, the plane mirror target is replaced by the reflective target 5 and the fixed plane mirror 17 as the object space three-dimensional rotation angle detection unit. This structural setting endows the reflective target 5 with asymmetry in the direction of the optical axis, making the measurement beam carry information on the pitch angle and yaw angle of the measured object while being sensitive to the roll angle of the measured object rotating around the optical axis direction. The instrument device has the three-dimensional angle measurement capability of measuring the roll angle of the object around the optical axis and the pitch angle and yaw angle of the vertical optical axis;

At the same time, the device of the present invention utilizes the first convex lens 41 and the first concave lens 42 to form the collimating objective lens group 4 . In this structure, the collimating objective lens group expands the focal length of the collimating objective lens of the angle measuring device to 3-4 times, and then improves the limit angular resolution of the overall system to the nano-rad scale, and finally realizes that the system can reach nano-rad within the traditional measurement range. High angular resolution on the order of arcs.

Therefore, compared with the traditional self-collimation angle measuring device, the present invention not only has the capability of measuring three-dimensional angle information, but also has the technical advantages of angle limit resolution reaching nano-arc level and high measurement stability.

Specific embodiment two

This embodiment is an embodiment of a three-dimensional angle measurement device based on spatial light modulation.

The structural diagram of the three-dimensional angle measurement device based on spatial light modulation in this embodiment is shown in FIG. 4 . On the basis of the first embodiment, in this embodiment, a second concave lens 43 , a second convex lens 44 and a third convex lens 45 are added to the collimating objective lens group 4 , as shown in FIG. 4 .

The embodiment of the three-dimensional angle measurement method based on spatial light modulation in this embodiment includes the following steps:

Step a, fixing the reflective target 5 to the surface of the measured object, placing the fixed plane mirror 17 so that its mirror surface is parallel to the exit surface of the first polarizing beam splitter 52 in the reflective target 5;

Step b, turn on the semiconductor laser light source 6, adjust the position of the measured object and the fixed plane reflector 17, so that the light spots received by the first area array CCD11 and the second area array CCD12 are at the center of the sensor, so that the fixed plane reflector 17 fixed position;

Step c, observing the brightness of the light spots of the first area array CCD11 and the second area array CCD12, adjusting the rotation angle of the polarizer 9 so that the light intensity received by the two image sensors is consistent;

Step d, when the four-quadrant position detector 14 outputs the light spot displacement and drift amounts E1 and E2 of the semiconductor laser light source 6, the transmissive spatial light modulator 18 adjusts the beam direction of the semiconductor laser light source 6 so that the light spot displacement and drift amounts E1 and E2 are always is 0;

Step e, the reflective target 5 rotates three-dimensionally with the measured object, and the first area CCD11 outputs the displacement value of the beam spot reflected by the plane reflector in the reflective target, wherein the distance between the light spot and the center of the sensor is decomposed into S1, S2, and the second The area array CCD12 outputs the displacement value of the beam spot reflected by the fixed plane mirror, where the distance between the spot and the center of the image sensor is S3;

Step f, using the displacements S1 and S2 of the light spot of the first area array CCD11, calculate and obtain β and γ according to S1=f tan(2β), S2=f tan(2γ), wherein β and γ are the measured objects around The angle of clockwise rotation of the y and z axes;

Step g, utilizing the displacement S3 of the second area array CCD12 light spot, calculate and obtain θ according to S3=f tan (θ), wherein θ is the angle between the return light and the optical axis of the light beam reflected by the first polarization beam splitter 52;

Step h, calculate and obtain ɑ according to ɑ=G(θ, β, γ), where ɑ is the angle of clockwise rotation of the measured object around the x-axis, and G represents a function. Finally, the angles α, β, and γ of the clockwise rotation of the measured object around the x, y, and z axes are obtained.

The innovation of the present invention is that a second concave lens 43 , a second convex lens 44 and a third convex lens 45 are added to the collimating objective lens group 4 to form a new collimating objective lens group 4 . The optimized parameters of the new collimating objective lens group can reduce the influence of the aberration of the optical system of the device on the measurement results, and reduce the systematic error of the whole device.

Specific embodiment three

This embodiment is an embodiment of a three-dimensional angle measurement device based on spatial light modulation.

The structural diagram of the three-dimensional angle measurement device based on spatial light modulation in this embodiment is shown in FIG. 5 . On the basis of the specific embodiment one, the present embodiment adds a second beam splitter 13 and a four-quadrant position detector 14 as a feedback detection module between the collimating objective lens group 4 and the reflective target 5; in the collimating objective lens group 4 , adding a second concave lens 43 , a second convex lens 44 and a third convex lens 45 , as shown in FIG. 5 .

The embodiment of the three-dimensional angle measurement method based on spatial light modulation in this embodiment includes the following steps:

Step a, fixing the reflective target 5 to the surface of the measured object, placing the fixed plane mirror 17 so that its mirror surface is parallel to the exit surface of the first polarizing beam splitter 52 in the reflective target 5;

Step b, turn on the semiconductor laser light source 6, adjust the position of the measured object and the fixed plane reflector 17, so that the light spots received by the first area array CCD11 and the second area array CCD12 are at the center of the sensor, so that the fixed plane reflector 17 fixed position;

Step c, observing the brightness of the light spots of the first area array CCD11 and the second area array CCD12, adjusting the rotation angle of the polarizer 9 so that the light intensity received by the two image sensors is consistent;

Step d, when the four-quadrant position detector 14 outputs the light spot displacement and drift amounts E1 and E2 of the semiconductor laser light source 6, the transmissive spatial light modulator 18 adjusts the beam direction of the semiconductor laser light source 6 so that the light spot displacement and drift amounts E1 and E2 are always is 0;

Step e, the reflective target 5 rotates three-dimensionally with the measured object, and the first area CCD11 outputs the displacement value of the beam spot reflected by the plane reflector in the reflective target, wherein the distance between the light spot and the center of the sensor is decomposed into S1, S2, and the second The area array CCD12 outputs the displacement value of the beam spot reflected by the fixed plane mirror, where the distance between the spot and the center of the image sensor is S3;

Step f, using the displacements S1 and S2 of the light spot of the first area array CCD11, calculate and obtain β and γ according to S1=f tan(2β), S2=f tan(2γ), wherein β and γ are the measured objects around The angle of clockwise rotation of the y and z axes;

Step g, utilizing the displacement S3 of the second area array CCD12 light spot, calculate and obtain θ according to S3=f tan (θ), wherein θ is the angle between the return light and the optical axis of the light beam reflected by the first polarization beam splitter 52;

Step h, calculate and obtain ɑ according to ɑ=G(θ, β, γ), where ɑ is the angle of clockwise rotation of the measured object around the x-axis, and G represents a function. Finally, the angles α, β, and γ of the clockwise rotation of the measured object around the x, y, and z axes are obtained.

The innovation of the present invention is that between the collimating objective lens group 4 and the reflective target 5, a second beam splitter 13 and a four-quadrant position detector 14 are added as a feedback detection module, which not only measures the drift of the light source beam in real time, but also real-time The beam drift caused by optical system instability is measured, and the light source drift is compensated in real time through closed-loop control deflection mirrors, which solves the problem of measurement instability caused by light source drift and optical system instability.

Claims (4)

1. The device for measuring the nanoradian-level three-dimensional angle based on the spatial light modulation is characterized by comprising a first spectroscope (2), a collimating objective group (4), a reflection target (5), a semiconductor laser source (6), a fourth convex lens (7), a multi-slit diaphragm (8), a polaroid (9), a second polarization spectroscope (10), a first area array CCD (11), a second area array CCD (12), a second spectroscope (13), a four-quadrant position detector (14), a first turning mirror (15), a second turning mirror (16), a fixed plane reflector (17) and a transmission-type spatial light modulator (18); the collimation objective lens group (4) consists of a first convex lens (41) and a first concave lens (42); the reflecting target (5) comprises a first polarizing beam splitter (52) and a plane reflector (51), and the first polarizing beam splitter and the plane reflector are arranged on the measuring surface of the measured object, so that the spatial three-dimensional angle change of the reflecting target (5) is the spatial three-dimensional angle change of the measured object; the fixed plane reflector (17) is independent of the reflection target, is not connected with the reflection target (5) and the measured object, and is fixed on the measuring base;

the semiconductor laser light source (6) is collimated by the fourth convex lens (7), and after being transmitted by the transmission type spatial light modulator (18), the semiconductor laser light source is incident to the multi-slit diaphragm (8) in parallel; the multi-slit diaphragm (8) is used as an object plane, and emitted measuring light is transmitted through the polaroid (9) and the first spectroscope (2) in sequence; linearly polarized light reflected by the second spectroscope (13) vertically enters a four-quadrant position detector (14) to serve as a drift amount feedback detection unit; linearly polarized light transmitted by the second spectroscope (13) is vertically incident on the collimating objective lens group (4) and collimated into parallel light beams after being refracted by the first refracting mirror (15) and the second refracting mirror (16), and the parallel light beams are incident on the reflecting target (5); one path of light passes through a first polarization spectroscope (52) in the reflection target (5) and is incident on a plane reflector (51) in the reflection target (5), and the reflected light beam returns along the original path of the light path after being transmitted by the first polarization spectroscope (52) in the reflection target (5) and is then transmitted by a second polarization spectroscope (10) at the measuring end and is collected and imaged by a first planar array CCD (11); the other path is reflected by a first polarization spectroscope (52) in the reflection target and enters a fixed plane reflector (17), and the reflected light beam is reflected by the first polarization spectroscope (52) in the reflection target, returns along the original path of the light path, is reflected by a second polarization spectroscope (10) at the measuring end and is collected and imaged by a second planar array CCD (12);

the multi-slit diaphragm (8) is a transmission diaphragm consisting of two groups of three parallel equidistant equal-width linear slits, the two groups of linear slits are perpendicular to each other, and a semiconductor laser light source (6) is collimated by a fourth convex lens (7) and then irradiates the multi-slit diaphragm (8), so that two groups of perpendicular three parallel equidistant equal-width linear light spots are an object of the device, and light beams emitted by the light spots are measuring light of the device;

or

The multi-slit diaphragm (8) is a transmission diaphragm consisting of two groups of four parallel equidistant equal-width linear slits, the two groups of linear slits are perpendicular to each other, and the semiconductor laser light source (6) is collimated by the fourth convex lens (7) and then irradiates the multi-slit diaphragm (8), so that two groups of perpendicular four parallel equidistant equal-width linear light spots are an object of the device, and light beams emitted by the light spots are measuring light of the device;

the first area array CCD (11) and the second area array CCD (12) are arranged at the focal plane of the collimating objective lens group (4) and are conjugated with the position of the multi-slit diaphragm (8); when the reflecting target (5) does not generate three-dimensional angle change, the centers of light spots collected by the first area array CCD (11) and the second area array CCD (12) are both at the geometric center position of the sensor; the four-quadrant position detector (14) is arranged behind the second spectroscope (13) and is used for collecting the real-time drift amount of the semiconductor laser light source (6); the transmission type spatial light modulator (18) is arranged between the fourth convex lens (7) and the multi-slit diaphragm (8) and is used for modulating the measuring light to enable the measuring light to vertically enter the multi-slit diaphragm (8);

the first turning mirror (15) and the second turning mirror (16) are arranged in parallel, and a fixed small angle exists between the normal direction of the mirror surface and the incident direction of the light beam.

2. The spatial light modulation-based nanoradian-scale three-dimensional angle measurement device according to claim 1, further comprising a second concave lens (43), a second convex lens (44) and a third convex lens (45);

the second concave lens (43), the second convex lens (44), the third convex lens (45), the first convex lens (41) and the first concave lens (42) jointly form a collimation objective lens group (4).

3. The spatial light modulation-based nanoradian-scale three-dimensional angle measurement device according to claim 1, further comprising a second concave lens (43), a second convex lens (44) and a third convex lens (45);

the second concave lens (43), the second convex lens (44), the third convex lens (45), the first convex lens (41) and the first concave lens (42) jointly form a collimation objective lens group (4);

the second spectroscope (13) is arranged between the collimating objective lens group (4) and the reflecting target (5); the measuring light is split by the second beam splitter (13), the reflected light beam is reflected to the four-quadrant position detector (14) through the second beam splitter (13) to be collected and imaged, and the transmitted light beam is transmitted through the second beam splitter (13) to continue to propagate.

4. The method for measuring the three-dimensional angle of the magnitude of nanoradian based on the spatial light modulation, which is realized on the three-dimensional angle measuring device of the magnitude of nanoradian based on the spatial light modulation according to claim 1, 2 or 3, is characterized by comprising the following steps:

a, fixing a reflection target (5) to the surface of a measured object, and placing a fixed plane reflector (17) to enable the mirror surface of the reflector to be parallel to the emergent surface of a first polarization spectroscope (52) in the reflection target (5);

b, lighting a semiconductor laser light source (6), adjusting the positions of a measured object and a fixed plane reflector (17), enabling light spots received by a first area array CCD (11) and a second area array CCD (12) to be positioned at the center of a sensor, and enabling the position of the fixed plane reflector (17) to be fixed;

c, observing the light spot brightness degree of the first area array CCD (11) and the second area array CCD (12), and adjusting the rotation angle of the polaroid (9) to enable the light intensity received by the two image sensors to be consistent;

d, when the four-quadrant position detector (14) outputs the light spot displacement drift amounts E1 and E2 of the semiconductor laser light source (6), the transmission type spatial light modulator (18) adjusts the light beam direction of the semiconductor laser light source (6) to enable the light spot displacement drift amounts E1 and E2 to be 0 all the time;

step e, the reflection target (5) rotates three-dimensionally along with the measured object, the first area array CCD (11) outputs the displacement value of the light beam and the light spot reflected by the plane reflector in the reflection target, wherein the distance between the light spot and the center of the sensor is decomposed into S1 and S2, the second area array CCD (12) outputs the displacement value of the light beam and the light spot reflected by the fixed plane reflector, and the distance between the light spot and the center of the image sensor is S3;

step f, calculating beta and gamma according to S1= f · tan (2 beta) and S2= f · tan (2 gamma) by using the displacements S1 and S2 of the light spot of the first area array CCD (11), wherein the beta and the gamma are angles of clockwise rotation of the measured object around the axes y and z;

step g, calculating to obtain theta according to S3= f · tan (theta) by using the displacement S3 of the light spot of the second area array CCD (12), wherein theta is an included angle between the return light of one path of light beam reflected by the first polarization beam splitter 52 and the optical axis;

step h, calculating and obtaining alpha according to alpha = G (theta, beta, gamma), wherein alpha is an angle of clockwise rotation of the object to be detected around an x axis, and G represents a function; and finally obtaining angles alpha, beta and gamma of the clockwise rotation of the measured object around the x, y and z axes.

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