CN108362222B - Non-zero novel point diffraction interference measurement system based on multidirectional inclined carrier frequency - Google Patents
Non-zero novel point diffraction interference measurement system based on multidirectional inclined carrier frequency Download PDFInfo
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- CN108362222B CN108362222B CN201810083474.5A CN201810083474A CN108362222B CN 108362222 B CN108362222 B CN 108362222B CN 201810083474 A CN201810083474 A CN 201810083474A CN 108362222 B CN108362222 B CN 108362222B
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- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
Abstract
The invention provides a non-zero novel point diffraction interferometry system based on multidirectional tilted carrier frequencies, which comprises a linear polarization laser source, an optical fiber coupler module, an optical fiber array, a piece to be measured and an interference image acquisition system, wherein the polarization laser source, the optical fiber coupler module and the optical fiber array are sequentially arranged on a first optical axis, the piece to be measured is positioned on a second optical axis, an included angle between the second optical axis and the first optical axis is one fourth of the divergence angle of each optical fiber emergent beam, and the best-fit spherical curvature center of the piece to be measured is coincided with the center of the end face of the optical fiber array. The invention uses the optical fiber array to form a point diffraction array, generates wave surface of multidirectional inclined carrier frequency to compensate the surface gradient of the measured piece, and solves the problems that the interference fringe density is too high and the solution cannot be realized when the complex surface-shaped element is measured by an interference method.
Description
Technical Field
The invention relates to the technical field of a complex surface shape optical element surface shape measuring system, in particular to a non-zero novel point diffraction interference measuring system based on multidirectional inclined carrier frequency.
Background
In recent years, as the performance of optical systems in various fields is required to be higher and higher, optical elements having a complex surface shape are widely used. Compared with the traditional optical element, the complex surface-shaped optical element has more degrees of freedom, can correct aberration more conveniently in an optical system, and greatly simplifies the system structure. However, the surface shape of the complex surface-shaped optical element is free and complex, the gradient change is large, and a plurality of problems are brought to the high-precision measurement of the surface shape, so that the bottleneck for limiting the further application of the large-caliber complex surface-shaped element in the fields of aerospace, national defense, astronomy, photoetching and the like is formed.
The detection method of the complex curved surface is mainly divided into a contact type and a non-contact type. The contact detection method is a method which can be applied in the optical element processing unit, and mainly comprises a three-coordinate measuring machine method, a contourgraph method and a swing arm type contourgraph method. The contact type measuring method adopts a point-by-point scanning mode, the single-point measuring precision can reach the nanometer level, but the measuring efficiency is low, the full-field morphology of a measured piece cannot be obtained at one time, and the surface of an optical element can be damaged in the measuring process. Non-contact detection methods include microlens array methods, structured light three-dimensional measurements, and interferometry. Among them, the interferometry is currently recognized as the most accurate and effective method for measuring the surface shape of an optical element. However, when a traditional interferometric measurement system is used for measuring a complex surface-shaped element, interference fringes are often too dense, and the surface shape of the optical element cannot be calculated through fringe information.
The Osten professor at Stuttgart Germany invented a multiple tilted wavefront interferometry based on an array of point sources. When the system is used for measuring a complex surface shape, the surface gradient of 10 degrees can be compensated to the maximum extent, and the measurement precision is superior to lambda/30. In the method, standard spherical waves are generated by a standard compensation spherical lens group, and because the system is a non-zero interference system and most of light paths are positioned outside an axis, a large amount of wave aberration is introduced into the standard compensation spherical lens group, so that the system error is overlarge, and the measurement precision of the method is limited; and the standard compensation spherical lens group with large caliber is very high in cost due to the limitation of processing level, so that the caliber of the whole system is limited, and the measurement of the surface shape with large caliber is difficult to realize.
Disclosure of Invention
The invention aims to provide a non-zero novel point diffraction interferometry system based on multidirectional tilted carrier frequency, and solves the problem that the prior art cannot realize high-precision measurement and generalized measurement of a large-caliber complex-surface-shaped optical element.
The technical solution for realizing the invention is as follows: a novel non-zero point diffraction interferometry system based on multidirectional tilted carrier frequencies comprises a linear polarization laser source, an optical fiber coupler module, an optical fiber array, a to-be-detected piece and an interference image acquisition system, wherein the polarization laser source, the optical fiber coupler module and the optical fiber array are sequentially arranged on a first optical axis, the to-be-detected piece is positioned on a second optical axis, an included angle between the second optical axis and the first optical axis is one fourth of the divergence angle of emergent light beams of each optical fiber, and the center of curvature of a best-fit spherical surface of the to-be-detected piece is coincided with the center of an end face of the optical fiber array;
the linear polarization laser emitted by the fiber laser is guided into the fiber coupler module by the fiber, the fiber coupler module divides one laser beam into a plurality of laser beams, the plurality of laser beams are guided into the fiber array to generate a plurality of standard spherical waves, one part of the standard spherical waves are used as reference light to enter the interference pattern acquisition system, the other part of the standard spherical waves are used as test light to enter a tested piece, the test light is reflected by the tested piece and the fiber array in sequence to enter the interference pattern acquisition system, and the reference light and the test light form a phase-shifting interference pattern in the interference pattern acquisition system.
Preferably, the interferogram collecting system comprises a collimating objective, a long cylinder diaphragm, a spatial polarization phase-shifting module, an imaging lens and a CCD camera, wherein the collimating objective, the long cylinder diaphragm, the spatial polarization phase-shifting module, the imaging lens and the CCD camera are arranged with a third optical axis, the reference light and the test light form a plurality of parallel beams through the collimating lens, the parallel beams pass through the spatial polarization phase-shifting module after being filtered and scattered by the long cylinder diaphragm, the spatial polarization phase-shifting module divides each beam into four diffracted lights with phase difference, and four spatial phase-shifting interferograms with phase differences of pi/2 are formed on a target surface of the CCD camera through the imaging lens.
Preferably, the spatial polarization phase-shifting module comprises a phase grating, a converging lens and a micro-polarizer array, wherein the parallel light which is filtered and scattered by the long-tube diaphragm 6 is split by the phase grating to obtain diffracted light, and the diffracted light passes through different areas of the micro-polarizer array respectively after passing through the converging lens.
Preferably, the second optical axis of the detected piece and the third optical axis of the interference pattern acquisition system are symmetrically distributed on two sides of the first optical axis.
Preferably, the several laser beams of the fiber coupler module are guided into the fiber array through optical fibers.
Compared with the prior art, the invention has the following remarkable advantages: (1) the invention utilizes the section of the thin optical fiber as a point diffraction device to generate nearly ideal point diffraction spherical waves, so that a standard compensation spherical lens group is not required to be added in a light path, the introduction of a large amount of wave aberration by the standard compensation spherical lens group is avoided, and the limit of the standard compensation spherical lens group on the measurement aperture of the interference system is broken through. (2) The invention uses the optical fiber array to form a point diffraction array, generates wave surface of multidirectional inclined carrier frequency to compensate the surface gradient of the measured piece, and solves the problems that the interference fringe density is too high and the solution cannot be realized when the complex surface-shaped element is measured by an interference method.
The present invention is described in further detail below with reference to the attached drawings.
Drawings
FIG. 1 is a schematic diagram of a novel non-zero point diffraction interferometry system based on multidirectional tilt according to the present invention.
Detailed Description
A novel non-zero point diffraction interferometry system based on multidirectional tilted carrier frequencies comprises a linear polarization laser source 1, an optical fiber coupler module 2, an optical fiber array 3, a piece to be measured 4 and an interference image acquisition system, wherein the polarization laser source 1, the optical fiber coupler module 2 and the optical fiber array 3 are sequentially arranged on a first optical axis, the piece to be measured 4 is located on a second optical axis, an included angle between the second optical axis and the first optical axis is one fourth of a divergence angle of emergent light beams of each optical fiber, and the best-fit spherical curvature center of the piece to be measured 4 is coincided with the end face center of the optical fiber array 3;
the linear polarization laser emitted by the optical fiber laser 1 is guided into the optical fiber coupler module 2 by an optical fiber, one laser beam is divided into a plurality of laser beams by the optical fiber coupler module 2, the plurality of laser beams are guided into the optical fiber array 3 to generate a plurality of standard spherical waves, one part of the standard spherical waves are used as reference light to enter the interference pattern acquisition system, the other part of the standard spherical waves are used as test light to enter the tested piece 4, the test light is reflected by the tested piece 4 and the optical fiber array 3 in sequence to enter the interference pattern acquisition system, and the reference light and the test light form a phase-shifting interference pattern in the interference pattern acquisition system.
In a further embodiment, the interference pattern acquisition system comprises a collimating objective 5, a long tube diaphragm 6, a spatial polarization phase-shifting module, an imaging lens 10 and a CCD camera 11, the collimating objective 5, the long tube diaphragm 6, the spatial polarization phase-shifting module, the imaging lens 10 and the CCD camera 11 are arranged with a common third optical axis, a reference light and a test light form a plurality of parallel beams through the collimating lens 5, the parallel beams pass through the spatial polarization phase-shifting module after being filtered and scattered by the long tube diaphragm 6, the spatial polarization phase-shifting module divides each beam into four diffracted lights with phase differences, and four spatial phase-shifting interference patterns with each phase difference of pi/2 are formed on a target surface of the CCD camera 11 through the imaging lens 10.
In a further embodiment, the spatial polarization phase shift module includes a phase grating 7, a converging lens 8, and a micro-polarizer array 9, wherein the parallel light after being filtered and scattered by the long-tube diaphragm 6 is split by the phase grating 7 to obtain diffracted light, and the diffracted light passes through different areas of the micro-polarizer array 9 after passing through the converging lens 8.
In a further embodiment, the second optical axis of the detected piece 4 and the third optical axis of the interferogram collecting system are symmetrically distributed on two sides of the first optical axis.
In a further embodiment, several laser beams of the fiber coupler module 2 are guided into the fiber array 3 through optical fibers.
In the invention, the test light emitted by each optical fiber in the optical fiber array 3 can cover the whole surface shape of the piece to be tested 4. The system is a non-zero interference system, and the test light does not need to completely return to the center of the end face of the optical fiber array 3 after being reflected by the piece to be tested 4, as long as the requirement that the fringe density of an interference pattern does not exceed the resolution of the CCD11 is met.
In order to eliminate the influence of stray light, only reference light emitted by an axial optical fiber and test light reflected to the center of the end face of the optical fiber array 3 by the to-be-tested piece 4 can pass through the long cylinder diaphragm 6, and the rest stray light can be absorbed by the inner wall of the long cylinder diaphragm 6.
In order to avoid mutual interference of interference patterns generated by adjacent point light sources, each optical fiber in the optical fiber array 3 can be switched on and off by a corresponding optical switch in the optical fiber coupler module 2.
And finally, obtaining sub-interferograms corresponding to different local surface shapes of the piece to be detected by controlling the on-off of the light paths corresponding to different point light sources, and splicing and fusing the sub-interferograms to obtain an interferogram corresponding to the surface shape of the whole piece to be detected. The spliced interference pattern is settled to obtain the surface shape data of the piece to be detected
The following is a more detailed description with reference to examples.
Example 1
Referring to fig. 1, a novel non-zero point diffraction interferometry system based on multidirectional inclination, wherein an optical path is an improved reflective point diffraction interferometry optical path system, and the system comprises a linear polarization laser source 1, an optical fiber coupling module 2, an optical fiber array 3, a to-be-detected element 4, a collimating objective 5, a long cylinder diaphragm 6, a phase grating 7, a converging lens 8, a micro-polarizer array 9, an imaging lens 10 and a CCD camera 11; the optical fiber array 3 is a gradient compensation module, and the phase grating 7, the convergent lens 8 and the micro-polaroid array 9 form a space polarization phase-shifting module; the linear polarization laser light source 1, the optical fiber coupling module 2 and the optical fiber array 3 are sequentially arranged in a coaxial manner, and the optical axis is a first optical axis; the optical axis of the tested piece 4 is a second optical axis, and the included angle between the second optical axis and the first optical axis is one fourth of the divergence angle of each optical fiber emergent beam; the collimator objective 5, the long cylinder diaphragm 6, the phase grating 7, the converging lens 8, the micro-polarizer array 9, the imaging lens 10 and the CCD camera 11 are sequentially arranged in a coaxial mode to form an interference pattern acquisition system, the optical axes of the collimator objective 5, the long cylinder diaphragm 6, the phase grating 7, the converging lens 8, the micro-polarizer array 9, the imaging lens 10 and the CCD camera 11 are a third optical axis, and a second optical axis where the detected piece 4 is located and the third optical axis where the interference pattern acquisition system is located are symmetrically distributed on two sides of the first optical axis; the linear polarization laser emitted by the fiber laser 1 is guided into the fiber coupling module 2 by the fiber, the fiber coupling module 2 divides a laser beam into a plurality of laser beams, then the plurality of laser beams are guided into the fiber array 3 by the fiber, a plurality of standard spherical waves are diffracted by the fiber array 3, wherein, one part of standard spherical wave as reference light enters the interference pattern collecting system, the other part of standard spherical wave as test light enters the tested piece 4, the test light is reflected by the tested piece 4 and the optical fiber array 3 in turn and enters the interference pattern collecting system, the reference light and the test light form a plurality of parallel beams in the interference pattern collecting system through the collimating lens 5, and after stray light is filtered by the long-tube diaphragm 6, the light beam is split by the phase grating 7 to obtain four beams of diffraction light, the four beams of diffraction light pass through different areas of the micro-polaroid array 9 respectively after passing through the converging lens 8, and then form a phase-shifting interference pattern on the CCD11 through the imaging objective lens 10.
Claims (5)
1. The non-zero novel point diffraction interferometry system based on the multidirectional tilted carrier frequency is characterized by comprising an optical fiber laser (1), an optical fiber coupler module (2), an optical fiber array (3), a piece to be measured (4) and an interference image acquisition system, wherein the optical fiber laser (1), the optical fiber coupler module (2) and the optical fiber array (3) are sequentially arranged on a first optical axis, the piece to be measured (4) is positioned on a second optical axis, the included angle between the second optical axis and the first optical axis is one fourth of the divergence angle of each optical fiber emergent beam, and the best-fit spherical curvature center of the piece to be measured (4) is coincided with the end face center of the optical fiber array (3);
the linear polarization laser emitted by the optical fiber laser (1) is guided into the optical fiber coupler module (2) by an optical fiber, one laser beam is divided into a plurality of laser beams by the optical fiber coupler module (2), the laser beams are guided into the optical fiber array (3) to generate a plurality of standard spherical waves, one part of the standard spherical waves enter the interference pattern acquisition system as reference light, the other part of the standard spherical waves enter a tested piece (4) as test light, the test light is reflected into the interference pattern acquisition system sequentially through the tested piece (4) and the optical fiber array (3), and the reference light and the test light form a phase-shifting interference pattern in the interference pattern acquisition system.
2. The non-null novel point-diffraction interferometry system based on multi-directional tilted carrier frequency according to claim 1, it is characterized in that the interference pattern acquisition system comprises a collimating objective (5), a long-tube diaphragm (6), a space polarization phase-shifting module, an imaging lens (10) and a CCD camera (11), the collimating objective lens (5), the long-tube diaphragm (6), the spatial polarization phase-shifting module, the imaging lens (10) and the CCD camera (11) are arranged on a common third optical axis, the reference light and the test light form a plurality of beams of parallel light through the collimating lens (5), the plurality of beams of parallel light pass through the spatial polarization phase-shifting module after being filtered and scattered by the long-tube diaphragm (6), the spatial polarization phase-shifting module divides each beam of light into four beams of diffracted light with phase difference, and four spatial phase-shifting interferograms with phase differences of pi/2 are formed on a target surface of the CCD camera (11) through the imaging lens (10).
3. The nonzero-digit novel point diffraction interferometry system based on multidirectional tilted carrier frequencies according to claim 2, wherein the spatial polarization phase shifting module comprises a phase grating (7), a converging lens (8) and a micro-polarizer array (9), wherein stray parallel light filtered by the long-tube diaphragm 6 is split by the phase grating (7) to obtain diffracted light, and the diffracted light passes through different areas of the micro-polarizer array (9) respectively after passing through the converging lens (8).
4. The nonzero-digit novel point diffraction interferometry system based on multidirectional tilted carrier frequencies according to claim 1, wherein a second optical axis in which the measured piece (4) is located and a third optical axis in which the interferogram acquisition system is located are symmetrically distributed on two sides of the first optical axis.
5. The nonzero-digit novel point-diffraction interferometry system based on multi-directional tilted carrier frequencies according to claim 1, wherein a plurality of laser beams of the fiber coupler module (2) are guided into the fiber array (3) through optical fibers.
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| CN109458944A (en) * | 2018-12-17 | 2019-03-12 | 南京理工大学 | The absolute verifying attachment of plane and its detection method based on synchronous conjugation differential interferometry |
| CN113203357B (en) * | 2021-04-09 | 2022-08-09 | 中国科学院上海光学精密机械研究所 | Bilateral Fizeau interferometer detection device |
| CN113251949B (en) * | 2021-06-18 | 2021-11-30 | 三代光学科技（天津）有限公司 | Method for generating single-point optical measurement path of micro-lens array surface shape |
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