CN112284299A - Five-degree-of-freedom simultaneous measurement interference device - Google Patents
Five-degree-of-freedom simultaneous measurement interference device Download PDFInfo
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- CN112284299A CN112284299A CN202010918713.1A CN202010918713A CN112284299A CN 112284299 A CN112284299 A CN 112284299A CN 202010918713 A CN202010918713 A CN 202010918713A CN 112284299 A CN112284299 A CN 112284299A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
- G01B11/272—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes using photoelectric detection means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
Abstract
The invention relates to a five-degree-of-freedom simultaneous measurement interference device which comprises a laser, wherein a beam expanding system, a polarization beam splitting plate, a quarter wave plate, a conical prism and a conical reflector are sequentially arranged in the direction of a collimated light beam emitted by the laser, the included angle between the polarization beam splitting plate and the direction of the collimated light beam emitted by the laser is 135 degrees, a second concave lens is arranged in the direction of reflecting the light beam by the polarization beam splitting plate, and the light beam is imaged onto a photoelectric detector by the second concave lens. The invention can simultaneously measure the errors of five degrees of freedom including linear positioning error, horizontal straightness error, vertical straightness error, yaw angle error and pitch angle error; the influence of environmental factors on linear displacement is negligible, and the method is suitable for complex detection environments; the system structure is simple; the measuring stroke and the measuring range are large.
Description
Technical Field
The invention relates to the technical field of optics, in particular to a five-degree-of-freedom simultaneous measurement interference device.
Background
Advanced manufacturing technology has become a key research object in the manufacturing industry as one of the priority subjects of the national compendium for long-term scientific and technical development (2009-2020). At present, the displacement control precision in various precision positioning devices is generally in the nanometer level, while in high-performance precision numerical control machine tools, three-coordinate measuring machines and photoetching machines, the displacement measurement precision reaches the nanometer level, wherein the rapid machining technology is also the main trend of development. Therefore, high-precision simultaneous measurement of multiple degrees of freedom is an important means for ensuring the machining precision and the machining efficiency.
At present, a multi-degree-of-freedom detection method mostly adopts a combined measurement method based on laser collimation and laser interference. The laser collimation method is suitable for dynamic measurement, and the commonly used light spot detectors are position sensitive detectors and four-quadrant detectors, and the measurement precision is related to the structure of the measurement system and the position resolution of the photoelectric detector. And various geometric motion errors of the linear guide rail are directly measured based on laser interference, the measurement precision is higher, and the nanometer level can be achieved. However, the laser interferometer is a single-parameter measuring instrument, only one error parameter can be measured in each installation and adjustment, different measuring accessories are required to be replaced and the interferometer needs to be readjusted in the measurement of different error parameters, and meanwhile, the measurement precision is difficult to guarantee due to the change of the surrounding environment in the detection process and the installation deviation in the multiple installation and adjustment processes of the interferometer. The ball bar instrument method is also commonly used for detecting geometric motion errors of the rapid numerical control machine tool, two ends of the ball bar instrument are respectively provided with a precise ball which is connected by a connecting rod internally provided with a displacement sensor, and the two precise balls are respectively adsorbed on a machine tool workbench and a machine tool spindle in a mechanical positioning mode. The comprehensive error of the machine tool is reflected through the reading of the sensor, and various geometric motion errors are obtained through error identification. The measuring method is simple and convenient to install and adjust, obtains more information in a single measurement compared with a laser interferometer, but is limited by the sizes of the ball rod instrument and the plane grating, cannot measure the whole working space of the numerical control machine tool, and is low in measuring resolution.
The prior art also relates to a method for simultaneously measuring two degree-of-freedom errors based on laser interference, for example, a chinese patent application with application number 201910056987.1 discloses a scheme called "micro-roll angle and straightness synchronization high-precision measurement interferometer and measurement method", however, the scheme is to detect two degree-of-freedom errors by increasing the complexity of an optical path system, and there is no effective optical path adjustment scheme yet.
Disclosure of Invention
The five-degree-of-freedom simultaneous measurement interference device comprises a laser, wherein a beam expanding system, a polarization beam splitting plate, a quarter wave plate, a conical prism and a conical reflector are sequentially arranged in the direction of a collimated light beam emitted by the laser, the included angle between the polarization beam splitting plate and the direction of the collimated light beam emitted by the laser is 135 degrees, a second concave lens is arranged in the direction of reflecting the light beam by the polarization beam splitting plate, and the light beam is imaged onto a photoelectric detector by the second concave lens.
Preferably, the beam expanding system includes a first concave lens and a first convex lens, the first concave lens is close to the laser, the second convex lens is close to the polarization beam splitting plate, and the first concave lens and the second convex lens are located in the direction of the collimated light beam emitted by the laser.
Further, the cone angle of the conical prism is controlled to be 170-179 degrees.
Preferably, the laser is a He — Ne laser, a solid laser, or a semiconductor laser.
Further, the polarization beam splitting plate is a wedge-shaped plate plated with a polarization film.
The application also provides a measuring method of the interference device, after collimated light beams emitted by the laser pass through the beam expanding system, the light beams are completely transmitted through the polarization beam splitting plate, the polarization state of the light beams after passing through the quarter-wave plate is in a circular polarization state, the light beams are divided into two parts, namely reference light beams and measuring light beams after being incident to the conical prism, and the reference light beams are reflected and returned in an original path; the measuring beam generates a corner, the corner is incident to the conical surface reflector and then returns in the original path, the measuring beam passes through the conical prism again and then is superposed with the light path of the reference beam to generate interference, the reference beam and the measuring beam pass through the quarter-wave plate and then are deflected in the vertical polarization state, the reference beam and the measuring beam are reflected by the polarization beam splitting plate and then are diverged after passing through the concave lens II, and interference patterns of the reference beam and the measuring beam are imaged on the photoelectric detector.
Preferably, the photoelectric receiver is an area array CCD or two line CCD arrays arranged in a cross.
Further, the second concave lens is used for imaging the interference light on the photoelectric detector.
Has the advantages that: the invention can simultaneously measure the errors of five degrees of freedom including linear positioning error, horizontal straightness error, vertical straightness error, yaw angle error and pitch angle error; the influence of environmental factors on linear displacement is negligible, and the method is suitable for complex detection environments; the system structure is simple; the measuring stroke and the measuring range are large.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic diagram of a photoelectric receiver of the present invention in an area array CCD configuration;
FIG. 3 is a schematic diagram of a photoelectric receiver of the present invention comprising two cross-shaped linear CCD arrays;
FIG. 4 is a diagram of interference fringes at the initial moment of the conical mirror of the present invention;
FIG. 5 is a diagram of interference fringes after the conical reflector of the present invention is displaced by 50nm along the optical axis;
FIG. 6 is a diagram of interference fringes when the conical mirror of the present invention is moved 20 μm horizontally;
FIG. 7 is a diagram of interference fringes when the conical mirror of the present invention is moved vertically by 20 μm;
FIG. 8 is a graph of interference fringes at 0.01 around the x-axis for a conical reflector of the present invention;
FIG. 9 is a graph of interference fringes at 0.01 around the y-axis for a conical mirror according to the present invention;
FIG. 10 is a schematic view of the displacement of the conical mirror of the present invention along the z-direction;
FIG. 11 is a schematic view of the displacement of the conical reflector of the present invention along the x-direction;
FIG. 12 is a schematic diagram of the rotation of the conical reflector of the present invention along a direction perpendicular to the xz plane; 1. a laser; 2. a first concave lens; 3. a convex lens; 4. a polarization beam splitting plate; 5. a quarter wave plate; 6. a conical prism; 7. a conical mirror; 8. a second concave lens; 9. a photodetector.
Detailed Description
Example one
The utility model provides a five degree of freedom simultaneous measurement interference device, includes laser instrument 1, be equipped with beam expanding system, polarization beam splitting flat board 4, quarter wave plate 5, conical prism 6 and conical mirror 7 in proper order in the direction that laser instrument 1 sent collimated light beam, polarization beam splitting flat board 4 with laser instrument 1 sends the contained angle of collimated light beam direction and is 135, polarization beam splitting flat board 4 will be equipped with concave lens two 8 in the direction of light beam reflection, concave lens two 8 will light beam formation of image is to photoelectric detector 9 on.
The beam expanding system comprises a concave lens 2 and a convex lens 3, wherein the concave lens 2 is close to the laser 1, the convex lens 3 is close to the polarization beam splitting flat plate 4, and the concave lens 2 and the convex lens 3 are located in the direction of a collimated light beam emitted by the laser 1.
The cone angle of the conical prism 6 is controlled to 170-179 degrees.
The laser 1 is a He-Ne laser, a solid laser, or a semiconductor laser.
The polarization beam splitting plate 4 is a wedge-shaped plate plated with a polarization film.
The working principle is as follows: after collimated light beams emitted by the laser 1 pass through the beam expanding system, the light beams are completely transmitted through the polarization beam splitting plate 4, the light beams are polarized in a circular polarization state after passing through the quarter-wave plate 5, the light beams are split into two parts, namely reference light beams and measuring light beams after entering the conical prism 6, and the reference light beams are reflected and returned in the original path, wherein 35% of incident light is reflected as an example in the embodiment; the measurement beam generation rotation angle is described in this embodiment by taking 65% of light transmission as an example, without considering light loss, the measurement beam is refracted outward at a small angle γ with the horizontal direction, enters the conical surface mirror, returns to the original path, passes through the conical prism 6 again, coincides with the optical path of the reference beam, and interferes, the reference beam and the measurement beam are polarized and shifted to the vertical polarization state after passing through the quarter-wave plate 5, are reflected by the polarization splitting plate 4, then pass through the concave lens two 8, and are diffused, and the interference pattern of the reference beam and the measurement beam is imaged onto the photodetector 9. The second concave lens 8 is used for imaging the interference light on the photoelectric detector 9.
As shown in fig. 2 and 3, the photoelectric receiver is an area CCD or two line CCDs arranged in a cross.
The judging method comprises the following steps:
when the conical mirror 7 is linearly displaced in the optical axis direction, the interference fringes appear as 'invaginations' or 'spits', see fig. 4 for the interference pattern at the initial position of the conical mirror 7, and fig. 5 for the interference fringe pattern after the conical mirror 7 is displaced by 50nm in the optical axis direction.
When the conical reflector 7 is linearly displaced in the direction perpendicular to the optical axis, the interference fringes appear to change toward or away from the moving direction of the conical reflector 7, and the interference fringes are symmetrically distributed, the axis of symmetry is along the displacement changing direction, for example, fig. 4 shows the interference fringes at the initial moment, fig. 6 shows the interference fringes when the conical reflector 7 moves 20 μm horizontally, and fig. 7 shows the interference fringes when the conical reflector 7 moves 20 μm vertically. It can be found that the period of the interference fringes is not changed, and the phase change magnitude and direction of the interference fringes represented by each pixel point are the same on two sides of the photoelectric receiver which are symmetrical with the center of the light beam.
When the conical reflector 7 generates a yaw angular displacement and a pitch angular displacement, the interference fringes are represented by different phase changes at the inner ring and the outer ring of the interference fringes, and the size of the yaw angle error and the pitch angle error can be obtained by measuring the difference between the optical path phase changes at specific positions of the inner ring and the outer ring, for example, fig. 4 is the interference fringes at the initial moment of the conical reflector 7, fig. 8 is the interference fringes when the conical reflector 7 rotates around the x axis by 0.01 degrees and about 175 μ rad, and fig. 9 is the interference fringes when the conical reflector 7 rotates around the y axis by 0.01 degrees and about 175 μ rad.
The positioning error measurement principle in the optical axis direction is described in detail below:
the basic principle of the system is that based on the interference between the reflected light of the A surface of the conical prism 6 and the reflected light of the conical reflector 7, when the conical prism 6 has five-degree-of-freedom errors of linear displacement (along the Z-axis direction), horizontal straightness (along the X-axis direction), vertical straightness (along the Y-axis direction), pitch angle (rotating around the X-axis) and yaw angle (rotating around the Y-axis), the interference fringes change specifically in corresponding areas.
Referring to fig. 10, after passing through the conical prism 6, the light beam is deflected outward at a certain angle, and then enters the conical mirror 7 and returns. Wherein alpha is the wedge angle of the conical prism 6, gamma is the angle of deflection of the light after passing through the conical prism 6, and beta is the cone angle of the conical reflector 7. The light path of the light propagating at the initial time and the position of the conical reflector 7 are shown as dotted lines, if the conical reflector 7 is displaced dz along the z direction, the position of the conical reflector 7 and the light beam path are shown as solid lines, and it can be found by comparison that the propagation distance of the left light and the right light in the air is reduced by Lp, and the refractive index of the air is assumed to be approximately 1, and since the light travels back and forth once, the change Δ L of the optical path of the left light and the right light can be expressed as:
ΔL＝2*LP＝2dz*cosβ (1)
after the left and right light rays finally interfere with the reference beam, the phase change Δ Φ p of the interference fringes can be expressed as:
in this system, the wavelength λ of incident light is 650nm, α is 2 °, and γ is 1 °, and if the phase resolution of interference fringes is 2 pi/1024, the measurement resolution of the straight line positioning error is about 0.31 nm.
The measurement principle of the horizontal straightness error and the vertical straightness error in the vertical optical axis direction is described in detail below:
referring to fig. 11, at the initial time, the position of the conical mirror 7 and the propagation path of the light beam are shown by dashed lines, and when the conical mirror 7 is displaced by dx along the x direction, the position of the conical mirror 7 and the propagation path of the light beam are shown by solid lines, as can be seen by comparison, the optical path of the left-side light ray is reduced, the optical path of the right-side light ray is increased, and the absolute value of the optical path change is equal to 2Ls, the phase change of the interference fringes can be shown as:
in the formula (3), λ is 650nm, α is 2 °, and β is 1 °, and if the phase resolution of the interference fringe is 2 pi/1024, the measurement resolution of the straightness error is about 18 nm. And the sum of the absolute values of the phase changes of the interference fringes on the left side and the right side can be averaged by using a mathematical method, so that the measurement resolution of the straightness error can be doubled.
The principle of measurement of yaw angle error and pitch angle error is described in detail below:
referring to fig. 12, at the initial time, the position of the conical mirror 7 and the propagation path of the light beam are shown by dotted lines, when the conical mirror 7 has a rotation angle error θ yaw in the direction perpendicular to the xz plane, the position of the conical mirror 7 and the propagation path of the light beam are shown by solid lines, and when observing the left side of the conical mirror 7, it can be found that the optical path length at the position of the outer ray B is changed more than that at the position of the inner ray a, and if LAB is 4mm, the optical path length difference at the positions of the points a and B can be expressed as:
in the formula (4), λ is 650nm and LAB is 4mm, and if the phase resolution of the interference fringe is 2 pi/1024, the measurement resolution of the yaw angle and pitch angle errors is about 0.16 μ rad. And the sum of the absolute values of the phase changes of the interference fringes on the left side and the right side can be averaged by using a mathematical method, so that the measurement resolution of the errors of the yaw angle and the pitch angle is doubled.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. The five-degree-of-freedom simultaneous measurement interference device is characterized in that: including laser instrument (1), be equipped with beam expanding system, polarization beam splitting flat board (4), quarter wave plate (5), conical prism (6) and conical mirror (7) in proper order in the direction that laser instrument (1) sent collimated light beam, polarization beam splitting flat board (4) with laser instrument (1) sends the contained angle of collimated light beam direction and is 135, polarization beam splitting flat board (4) will be equipped with concave lens two (8) in the direction of beam reflection, concave lens two (8) will beam imaging is to photodetector (9) on.
2. The five-degree-of-freedom simultaneous measurement interferometer apparatus of claim 1, wherein: the beam expanding system comprises a first concave lens (2) and a second concave lens (3), wherein the first concave lens (2) is close to the laser (1), the second convex lens (3) is close to the polarization beam splitting flat plate (4), and the first concave lens (2) and the second convex lens (3) are located in the direction of a collimated light beam emitted by the laser (1).
3. The five-degree-of-freedom simultaneous measurement interferometer apparatus of claim 1, wherein: the cone angle of the conical prism (6) is controlled to be 170-179 degrees.
4. The five-degree-of-freedom simultaneous measurement interferometer apparatus of claim 1, wherein: the laser (1) is a He-Ne laser, a solid laser or a semiconductor laser.
5. The five-degree-of-freedom simultaneous measurement interferometer apparatus of claim 1, wherein: the polarization beam splitting plate (4) is a wedge-shaped plate plated with a polarization film.
6. A measurement method using an interferometric device according to any one of claims 1 to 5, characterized in that: after collimated light beams emitted by the laser (1) pass through the beam expanding system, the light beams are completely transmitted through the polarization beam splitting plate (4), the light beams are polarized in a circular polarization state after passing through the quarter-wave plate (5), the light beams are divided into two parts, namely reference light beams and measuring light beams after being incident to the conical prism (6), and the reference light beams are reflected and returned in an original path; the measuring beam generates a corner, the measuring beam enters the conical surface reflector after the corner is turned, then returns to the original path, passes through the conical prism (6) again, then is superposed with the light path of the reference beam, generates interference, the reference beam and the measuring beam are deflected in a vertical polarization state after passing through the quarter-wave plate (5), are reflected by the polarization beam splitting plate (4), then are diffused by the concave lens II (8), and interference patterns of the reference beam and the measuring beam are imaged on the photoelectric detector (9).
7. The measuring method of the five-degree-of-freedom simultaneous measurement interference device according to claim 6, characterized in that: the photoelectric receiver is an area array CCD or two linear array CCDs arranged in a cross way.
8. The measuring method of the five-degree-of-freedom simultaneous measurement interference device according to claim 6, characterized in that: the second concave lens (8) is used for imaging the interference light on the photoelectric detector (9).
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010918713.1A CN112284299A (en) | 2020-09-04 | 2020-09-04 | Five-degree-of-freedom simultaneous measurement interference device |
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| CN202010918713.1A CN112284299A (en) | 2020-09-04 | 2020-09-04 | Five-degree-of-freedom simultaneous measurement interference device |
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