CN111238396A - Transient digital moire phase-shifting interferometry device and method - Google Patents
Transient digital moire phase-shifting interferometry device and method Download PDFInfo
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Abstract
A transient digital moire phase shift interference measuring device and method solves the defect that instantaneous vibration resistance needs to be sacrificed to replace a measuring range when a two-step carrier splicing method is used, the measuring range of a traditional digital moire phase shift method is expanded, and meanwhile the instantaneous vibration resistance of the digital moire phase shift method is kept. The device comprises: the device comprises a light source (1), a first spectroscope (2), a reference mirror (3), a polarization grating (4), a measured mirror (5), a lambda/4 wave plate (6), a second spectroscope (7), a first linear polarizer (8), a first imaging objective lens (9), a first camera (10), a second linear polarizer (11), a second imaging objective lens (12) and a second camera (13); different carrier waves are loaded through the light splitting performance of the polarization grating, the polarization grating is used for separating the two beams of interference light, and two actual interference patterns are obtained at the same time.
Description
Technical Field
The invention relates to the technical field of photoelectric detection, in particular to a transient digital moire phase-shifting interference measuring device and a method adopted by the transient digital moire phase-shifting interference measuring device.
Background
The digital Moire phase-shifting interference measuring method is an aspheric surface detection method, belongs to one of partial compensation interference methods, is an instantaneous vibration-resistant interference measuring method, and can realize high-precision measurement without a phase-shifting mechanism.
Because the digital moire phase-shifting interferometry needs low-pass filtering, the situation of frequency spectrum aliasing occurs when the residual wave front is large or the carrier wave is large, so that the phenomenon of solving an error region occurs in the digital moire phase-shifting interferometry, and the position of the error region is related to the size of the loaded space carrier wave. This results in a limited residual wavefront bandwidth when using digital moire phase shifting interferometry. Resulting in a residual wavefront bandwidth using the digital moire phase shifting interferometry method that is only 0.707 of the residual wavefront bandwidth of the conventional multi-step phase shifting interferometry method.
Because the position of the error region solved by the digital moire phase-shifting interferometry is related to the size of the loaded space carrier under the condition of spectrum aliasing, in order to solve the problem that the residual wavefront bandwidth of the digital moire phase-shifting interferometry is limited, the applicant's patent (patent No. 201810067710.4, invention name: the digital moire phase-shifting interferometry based on the two-step carrier splicing method) provides the two-step carrier splicing method based on the digital moire phase-shifting interferometry, and two surface errors with different error regions to be solved are obtained by collecting two interferograms added with different carriers. And then extracting the correct areas of the two surface shape errors for splicing to finally obtain the complete surface shape error.
The two-step carrier splicing method expands the measurement range of the traditional digital moire phase-shifting method, eliminates the limitation of the residual wavefront bandwidth of the traditional digital moire phase-shifting method, and enables the residual wavefront bandwidth of the digital moire phase-shifting interferometry to be equivalent to that of the traditional phase-shifting interferometry, but the existing two-step carrier splicing method needs to load the space carrier f in sequenceR1Collecting corresponding first interferogram and loading spatial carrier fR2The acquisition of the corresponding second interferogram, i.e. the acquisition of the two interferograms, requires a time interval, which means that the two-step carrier splicing method loses the instantaneous vibration resistance of the digital moire phase shifting method.
A polarization grating is a diffractive optical element that achieves selective splitting based on the polarization state of incident light, the diffraction angle depending on the spatial period of the grating. When the incident light of the polarization grating is linearly polarized light, the emergent light thereof is +1 order diffraction light and-1 order diffraction light, wherein the +1 order diffraction light is left circularly polarized light, and the-1 order diffraction light is right circularly polarized light; when the incident light of the polarization grating is right-handed circularly polarized light, the emergent light is + 1-order diffracted light, and the polarization state of the diffracted light is left-handed circularly polarized light; when the incident light of the polarization grating is left-handed circularly polarized light, the emergent light is-1 order diffraction light, and the polarization state of the diffraction light is right-handed circularly polarized light.
Disclosure of Invention
In order to overcome the defects of the prior art, the technical problem to be solved by the invention is to provide a transient digital moire phase-shifting interference measuring device, which overcomes the defect that the instantaneous vibration resistance needs to be sacrificed to replace the measuring range when a two-step carrier splicing method is used, expands the measuring range of the traditional digital moire phase-shifting method, and simultaneously reserves the instantaneous vibration resistance of the digital moire phase-shifting method.
The technical scheme of the invention is as follows: the transient digital moire phase shifting interferometry device comprises: the device comprises a light source (1), a first spectroscope (2), a reference mirror (3), a polarization grating (4), a measured mirror (5), a lambda/4 wave plate (6), a second spectroscope (7), a first linear polarizer (8), a first imaging objective lens (9), a first camera (10), a second linear polarizer (11), a second imaging objective lens (12) and a second camera (13);
the light source emits monochromatic linear polarized light, the polarization azimuth angle is 45 degrees, after the monochromatic linear polarized light is split by the first beam splitter, one part of the monochromatic linear polarized light is reflected to the surface of the reference mirror, one part of the monochromatic linear polarized light is transmitted to the polarization grating, the monochromatic linear polarized light incident to the surface of the reference mirror is reflected by the reference mirror and enters the second beam splitter as reference light, as the polarization azimuth angle is 45 degrees, half of the monochromatic linear polarized light penetrates through the second beam splitter, half of the monochromatic linear polarized light is reflected by the second beam splitter, the splitting performance of the monochromatic linear polarized light incident to the polarization grating is divided into + 1-grade left-handed circularly polarized diffracted light serving as a first light beam and-1-grade right-handed circularly polarized diffracted light serving as a second light beam, the two beams of light respectively form two included anglesR1、fR2The different space carriers are incident on the surface of the measured mirror and are reflected to a lambda/4 wave plate, after passing through the lambda/4 wave plate, the first light beam and the second light beam are converted into two linearly polarized light beams with orthogonal polarization directions, and both the two linearly polarized light beams reach a second spectroscope, wherein one light beam is completely reflected by the second spectroscope, and the light beam and the part which is reflected by the reference mirror and then penetrates through the second spectroscope pass through a first linear polarizer with a polarization azimuth angle of 45 degrees together to generate first interference light; the other beam of light completely penetrates through the second beam splitter, and passes through a second linear polarizer with the polarization azimuth angle of 45 degrees together with the part reflected by the second beam splitter after being reflected by the reference mirror to generate second interference light; the first interference light is converged by the first imaging objective lens and then enters the first camera to obtain a first interference pattern, the second interference light is converged by the second imaging objective lens and then enters the second camera to obtain a second interference pattern, the first interference pattern is determined to be the first interference pattern or the second interference pattern according to the placement position of the lambda/4 wave plate, and the second interference pattern is the other one of the first interference pattern and the second interference pattern.
The monochromatic linear polarized light of the incident polarization grating is divided into + 1-order left-handed circularly polarized diffraction light serving as a first light beam and-1-order right-handed circularly polarized diffraction light serving as a second light beam by the light splitting performance of the polarization grating, the two light beams respectively form two included angles with the incident light in the same size and opposite directions, and the frequency is f in the methodR1、fR2The different space carriers are incident on the surface of the measured mirror and are reflected to a lambda/4 wave plate, after passing through the lambda/4 wave plate, the first light beam and the second light beam are converted into two linearly polarized light beams with orthogonal polarization directions, and both the two linearly polarized light beams reach a second spectroscope, wherein one light beam is completely reflected by the second spectroscope, and the light beam and the part which is reflected by the reference mirror and then penetrates through the second spectroscope pass through a first linear polarizer with a polarization azimuth angle of 45 degrees together to generate first interference light; the other beam of light completely penetrates through the second beam splitter, and passes through a second linear polarizer with the polarization azimuth angle of 45 degrees together with the part reflected by the second beam splitter after being reflected by the reference mirror to generate second interference light; the first interference light is converged by the first imaging objective lens and then enters the first camera to obtain a first interference pattern, the second interference light is converged by the second imaging objective lens and then enters the second camera to obtain a second interference patternReferring to the diagram, a first interference diagram is determined to be a first interference diagram or a second interference diagram according to the arrangement position of the lambda/4 wave plate, a second interference diagram is determined to be the other one of the first interference diagram and the second interference diagram, therefore, two different carriers can be loaded on the measured surface at the same time, thereby shortening the measuring process, saving the measuring time, leading the measurement to have the instantaneous anti-vibration characteristic, when the waves are loaded to the measured surface, any element in the measuring device does not need to be moved, and the waves only need to be adjusted to the position when the measuring device is constructed, thereby avoiding the adjustment error caused by moving elements when loading waves in the existing two-step carrier splicing method, reducing error sources, improving measurement precision, therefore, the defect that the instantaneous vibration resistance needs to be sacrificed to replace the measurement range when a two-step carrier splicing method is used is solved, the measurement range of the traditional digital moire phase shifting method is expanded, and the instantaneous vibration resistance of the digital moire phase shifting method is kept.
The transient digital moire phase shift interferometry method is also provided, and comprises the following steps:
(1) constructing a virtual interference measuring device to obtain the residual wavefront of an ideal system on an image surface
(2) Constructing an actual interference measurement device according to the virtual interference measurement device;
(3) the +1 st order diffraction light and the-1 st order diffraction light are respectively taken as the frequency f by the light splitting performance of the polarization gratingR1、fR2The two beams of interference light are separated by utilizing the polarization beam splitting characteristic of the polarization beam splitting prism, two interference patterns are acquired at one time, and the space carrier f is loadedR1The obtained interference pattern is defined as a first interference pattern, and a space carrier f is loadedR2Defining the obtained interference pattern as a second interference pattern;
(4) and solving a complete error-free measured surface shape by adopting a digital Moire phase-shifting interferometry based on a two-step carrier splicing method, thereby realizing the measurement of the measured surface shape.
Drawings
FIG. 1 is a schematic structural diagram of a transient digital moire phase shifting interferometry device according to the present invention.
FIG. 2 is a flow chart of a transient digital moire phase shifting interferometry method in accordance with the present invention.
Wherein: the system comprises a light source 1, a first beam splitter 2, a reference mirror 3, a polarization grating 4, a measured mirror 5, a wave plate 6-lambda/4, a second beam splitter 7, a first linear polarizer 8, a first imaging objective 9, a first camera 10, a second linear polarizer 11, a second imaging objective 12 and a second camera 13.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the term "comprises/comprising" and any variations thereof in the description and claims of the present invention and the above-described drawings is intended to cover non-exclusive inclusions, such that a process, method, apparatus, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As shown in fig. 1, the transient digital moire phase shift interferometry device comprises: the system comprises a light source 1, a first spectroscope 2, a reference mirror 3, a polarization grating 4, a measured mirror 5, a lambda/4 wave plate 6, a second spectroscope 7, a first linear polarizer 8, a first imaging objective lens 9, a first camera 10, a second linear polarizer 11, a second imaging objective lens 12 and a second camera 13;
the light source emits monochromatic linear polarized light, the polarization azimuth angle is 45 degrees, after the light is split by the first spectroscope, one part of the light is reflected to the surface of the reference mirror, one part of the light is transmitted to the polarization grating, the monochromatic linear polarized light incident on the surface of the reference mirror is reflected by the reference mirror,the monochromatic linear polarized light of the incident polarization grating is divided into + 1-order left-handed circularly polarized diffraction light serving as a first light beam and-1-order right-handed circularly polarized diffraction light serving as a second light beam by the light splitting performance of the polarization grating, the two light beams respectively form two included angles with the incident light in the same size and opposite directions, and the frequencies are respectively f in the method provided by the inventionR1、fR2The different space carriers are incident on the surface of the measured mirror and are reflected to a lambda/4 wave plate, after passing through the lambda/4 wave plate, the first light beam and the second light beam are converted into two linearly polarized light beams with orthogonal polarization directions, and both the two linearly polarized light beams reach a second spectroscope, wherein one light beam is completely reflected by the second spectroscope, and the light beam and the part which is reflected by the reference mirror and then penetrates through the second spectroscope pass through a first linear polarizer with a polarization azimuth angle of 45 degrees together to generate first interference light; the other beam of light completely penetrates through the second beam splitter, and passes through a second linear polarizer with the polarization azimuth angle of 45 degrees together with the part reflected by the second beam splitter after being reflected by the reference mirror to generate second interference light; the first interference light is converged by the first imaging objective lens and then enters the first camera to obtain a first interference pattern, the second interference light is converged by the second imaging objective lens and then enters the second camera to obtain a second interference pattern, the first interference pattern is determined to be the first interference pattern or the second interference pattern according to the placement position of the lambda/4 wave plate, and the second interference pattern is the other one of the first interference pattern and the second interference pattern.
The monochromatic linear polarized light of the incident polarization grating is divided into + 1-order left-handed circularly polarized diffraction light as a first light beam and-1-order right-handed circularly polarized diffraction light as a second light beam by the light splitting performance of the polarization grating, the two light beams respectively form two included angles with the incident light in the same size and opposite directions, and the frequency is f respectively in the method provided by the inventionR1、fR2The different space carrier waves are incident on the surface of the measured mirror and reflected to the lambda/4 wave plate, after passing through the lambda/4 wave plate, the first light beam and the second light beam are converted into two linearly polarized light beams with orthogonal polarization directions, both of which reach the second beam splitter, one of the light beams is totally reflected by the second beam splitter and passes through the reference mirrorAfter being reflected, the parts which penetrate through the second spectroscope pass through a first linear polarizer with a polarization azimuth angle of 45 degrees together to generate first interference light; the other beam of light completely penetrates through the second beam splitter, and passes through a second linear polarizer with the polarization azimuth angle of 45 degrees together with the part reflected by the second beam splitter after being reflected by the reference mirror to generate second interference light; the first interference light is converged by the first imaging objective lens and enters the first camera to obtain a first interference pattern, the second interference light is converged by the second imaging objective lens and enters the second camera to obtain a second interference pattern, the first interference pattern is determined to be the first interference pattern or the second interference pattern according to the placement position of the lambda/4 wave plate, and the second interference pattern is the other one of the first interference pattern and the second interference pattern, so that two different carrier waves can be loaded on the measured surface at the same time, the measurement process is shortened, the measurement time is saved, the measurement has instantaneous vibration resistance, any element in the measurement device does not need to be moved when the measured surface is loaded, the adjustment to the position is only needed when the measurement device is constructed, the adjustment error caused by the movement of the element when the wave is loaded in the existing two-step carrier splicing method is avoided, the error source is reduced, the measurement precision is improved, and the defect that the measurement range is required to be obtained by sacrificing the instantaneous vibration resistance when the two-step carrier splicing method is used is solved, the measuring range of the traditional digital moire phase shifting method is expanded, and the instantaneous vibration resistance of the digital moire phase shifting method is kept.
Preferably, the light source emits monochromatic linear polarized light, the polarization azimuth angle is 45 degrees, the specific wavelength is determined according to the actual measurement condition, and the beam caliber is selected according to the caliber of the measured range on the measured surface.
Preferably, the first beam splitter is a non-polarizing beam splitter, the working wavelength range of the first beam splitter is selected according to the light source, and the clear aperture of the first beam splitter is selected according to the aperture of the measured range on the measured surface.
Preferably, the specific surface shape and the surface flatness of the reference mirror are determined according to actual measurement conditions, and the caliber of the reference mirror is not less than the caliber of the measured range on the measured surface.
Preferably, the polarization grating is a grating with a larger period, and an included angle between two beams of diffracted light obtained by splitting after linearly polarized light is incident is smaller, so that the carrier wave size of the polarization grating ensures that the residual wave front bandwidth is within a limited range; the working wavelength is selected according to the light source, and the caliber is selected according to the caliber of the measured range on the measured surface.
Preferably, the measured mirror is a plane, a spherical surface or an aspherical surface.
Preferably, the fast axis direction of the λ/4 wave plate ensures that the linearly polarized light converted by one of the left-handed circularly polarized light and the right-handed circularly polarized light after passing through the wave plate is not penetrated by the second spectroscope, the other linearly polarized light converted by the wave plate is not reflected by the second spectroscope, and the aperture thereof is selected according to the aperture of the measured range on the measured surface.
Preferably, the second beam splitter is a polarizing beam splitter, one of the p-direction polarized light and the s-direction polarized light is totally transmitted through the second beam splitter, and the other is totally reflected by the second beam splitter; the aperture is selected according to the aperture of the measured range on the measured surface.
Preferably, the polarization directions of the first linear polarizer and the second linear polarizer and the p direction or the s direction form 45 degrees, and the calibers of the first linear polarizer and the second linear polarizer are selected according to the calibers of a measured range on a measured surface; the first imaging objective lens and the second imaging objective lens have the same parameters and indexes, the focal length is selected according to an allowable distance range, the imaging quality comprehensive measurement precision requirement and camera parameters are selected, the working wavelength is selected according to a light source, and the caliber is selected according to the emergent light caliber of the polarization grating; the first camera and the second camera have the same parameters and indexes, the performance of the first camera and the second camera is selected according to the measurement precision requirement, the working wavelength range of the first camera and the second camera is selected according to the light source, and the image surface size of the first camera and the second camera is selected according to the emergent light caliber of the polarization grating and the imaging objective lens parameters.
As shown in fig. 2, there is also provided a transient digital moire phase shift interferometry method, which includes the following steps:
(1) constructing a virtual interference measuring device to obtain the residual wavefront of an ideal system on an image surface
(2) Constructing an actual interference measurement device according to the virtual interference measurement device;
(3) the +1 st order diffraction light and the-1 st order diffraction light are respectively taken as the frequency f by the light splitting performance of the polarization gratingR1、fR2The two beams of interference light are separated by utilizing the polarization beam splitting characteristic of the polarization beam splitting prism, two interference patterns are acquired at one time, and the space carrier f is loadedR1The obtained interference pattern is defined as a first interference pattern, and a space carrier f is loadedR2Defining the obtained interference pattern as a second interference pattern;
(4) and solving a complete error-free measured surface shape by adopting a digital Moire phase-shifting interferometry based on a two-step carrier splicing method, thereby realizing the measurement of the measured surface shape.
Specific examples of the present invention are described in detail below.
The plane shape error of the plane mirror is measured by adopting an instantaneous digital moire phase-shifting interferometry based on a two-step carrier splicing method, and the measuring device is the instantaneous digital moire phase-shifting interferometry based on the two-step carrier splicing method and comprises a 1-light source, a 2-first spectroscope, a 3-reference mirror, a 4-polarization grating, a 5-measured mirror, a 6-lambda/4 wave plate, a 7-second spectroscope, an 8-first linear polarizer, a 9-first imaging objective lens, a 10-first camera, an 11-second linear polarizer, a 12-second imaging objective lens and a 13-second camera, wherein the 8-first linear polarizer, the 9-first imaging objective lens, the 10-first camera, the 11-second linear polarizer and the 12-second imaging. The polarization grating is a diffraction optical element which realizes selective light splitting based on the polarization state of incident light, and the diffraction angle depends on the number of grating lines. By controlling the polarization state of the incident light, the polarization grating can regulate the energy distribution between the positive first order and the negative first order. Compared with the traditional mechanical deflection device, the polarization grating has the advantages that the required space is small, and the increased system weight can be ignored. Applications for polarization gratings include beam deflection in Augmented Reality (AR) systems (e.g., AR headsets), telecommunication equipment, and optical systems, among others. Some mainstream manufacturers provide standard polarization gratings with a period of 5 μm and operating wavelengths of 520nm, 650nm, 780nm, 850nm and 940nm, and some manufacturers provide various customized services including customizing indexes such as specific size, design wavelength, grating period and diffraction angle in addition to the standard polarization gratings.
The measured range of the measured mirror plane mirror of the embodiment is a circular area with the diameter of 25 mm. In the measuring process, a light source emits monochromatic linear polarized light with the central wavelength of 632.8nm, and the aperture of the light beam is 20 mm. The first beam splitter is a non-polarizing beam splitter. The light transmission apertures of the first spectroscope and the second spectroscope are both 25.4 mm. The reference mirror is a standard plane mirror, the surface flatness is lambda/10, and the caliber is 25.4 mm. The space period of the polarization grating is 363 μm, the working wavelength is 633nm, the 1-order diffraction angle is about 0.1 degrees, and the aperture is 25.4 mm. The fast axis direction of the lambda/4 wave plate ensures that the left-handed circularly polarized light is converted into s-direction linearly polarized light after passing through the wave plate, the left-handed circularly polarized light is converted into p-direction linearly polarized light after passing through the wave plate, and the caliber is 25.4 mm. The second spectroscope is a polarization spectroscope, reflects s-direction linearly polarized light and transmits p-direction linearly polarized light. The focal length of the first imaging objective lens and the focal length of the second imaging objective lens are 50mm, the working wavelength is 350nm-700nm, and the caliber is 25 mm. The first camera and the second camera have a resolution of 1024 × 1024 and a pixel size of 5 μm. The interferogram acquired by the first camera is a first interferogram, and the interferogram acquired by the second camera is a second interferogram.
The measurement steps are as follows:
(1) constructing a virtual interference measuring device to obtain the residual wavefront of an ideal system on an image surface
(2) And constructing an actual interference measuring device according to the virtual interference measuring device.
(3) By the light splitting performance of the polarization grating, the polarization grating 1 with the spatial period of 363 μm is used for light splitting, and +1 st order diffraction light and-1 st order diffraction light are respectively taken as frequency fR1＝70/1024λ/pixel、fR2Different space carriers of-70/1024 lambda/pixel, separating two interference lights by using polarization splitting characteristic of polarization splitting prism, acquiring two interference patterns at one time, and loading space carrier fR1To obtainIs defined as an interference pattern I, and a space carrier f is loadedR2The interferogram obtained is defined as interferogram II.
(4) According to the method proposed in the patent 201810067710.4, two-step carrier splicing is adopted according to the third step to the seventh step, so that the complete error-free measured surface shape is solved, and the measurement of the measured surface shape is realized.
Steps three to seven of the method proposed in patent 201810067710.4 are as follows:
step three: respectively solving the interference pattern I and the interference pattern II by adopting a digital moire phase-shifting interference method: method for solving loaded carrier f by adopting digital Moire phase-shifting interference methodR1Measured surface shape SFE of time1(ii) a Method for solving loaded carrier f by adopting digital Moire phase-shifting interference methodR2Measured surface shape SFE of time2；
Step four: pre-marking error regions and comparing whether the error regions overlap;
step 4.1: SFE (surface shape to be measured) solved in step three1Using spatial carriers f as basisR1Tested surface shape SFE solved by pre-marking1Solving the error region ω1，ω1∈SFE1；
Step 4.2: SFE (surface shape to be measured) solved in step three2Using spatial carriers f for the substrateR2Tested surface shape SFE solved by pre-marking2Solving the error region ω2，ω2∈SFE2；
Step 4.3: checking for error regions omega1And error region omega2Whether the carrier waves are completely separated and not overlapped, if the carrier waves have an overlapped area, the carrier waves loaded in the step two need to be changed;
step five: according to the tested surface SFE obtained in the step 4.11Solving the error region ω1Extracting the solved SFE of the measured surface shape2At omega1Area SFE without error2'；
Step six: SFE (surface shape to be measured) solved according to the third step1The solved SFE of the measured surface shape2Calculating and solving splicing vector tau ═ delta a, delta b and delta c]T；
In the formula
For solving SFE of measured surface shape1The phase of (a) is determined,
for solving SFE of measured surface shape2The phase of (d);
step seven: adjusting the surface shape SFE without errors obtained in the step five by using the splicing vector tau2The relative position and amount of tilt of'; and using the solved error-free area SFE2' alternative solved SFE of measured surface shape1Solving error region ω in1Obtaining the final complete tested surface shape SFE without errors, and defining the phase of the solved tested surface shape SFE without errors as
Then there is
The final complete tested surface shape SFE without errors is obtained, namely the problem of solving errors in the large residual wavefront by adopting a digital moire phase-shifting interference method is solved, the measurement range of the traditional digital moire phase-shifting method is expanded, the residual wavefront bandwidth limitation of the traditional digital moire phase-shifting method is eliminated, and the residual wavefront bandwidth of the digital moire phase-shifting interference method is equivalent to that of the traditional phase-shifting interference method; namely, the measurement of the measured surface shape is realized.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.
Claims (10)
1. The utility model provides a transient state digit moire phase shift interferometry device which characterized in that: it includes: the device comprises a light source (1), a first spectroscope (2), a reference mirror (3), a polarization grating (4), a measured mirror (5), a lambda/4 wave plate (6), a second spectroscope (7), a first linear polarizer (8), a first imaging objective lens (9), a first camera (10), a second linear polarizer (11), a second imaging objective lens (12) and a second camera (13);
the light source emits monochromatic linear polarized light, the polarization azimuth angle is 45 degrees, after the monochromatic linear polarized light is split by the first beam splitter, one part of the monochromatic linear polarized light is reflected to the surface of the reference mirror, one part of the monochromatic linear polarized light is transmitted to the polarization grating, the monochromatic linear polarized light incident to the surface of the reference mirror is reflected by the reference mirror and enters the second beam splitter as reference light, as the polarization azimuth angle is 45 degrees, half of the monochromatic linear polarized light penetrates through the second beam splitter, half of the monochromatic linear polarized light is reflected by the second beam splitter, the monochromatic linear polarized light incident to the polarization grating is divided into + 1-grade left-handed circularly polarized diffracted light serving as a first light beam and-1-grade right-handed circularly polarized diffracted light serving as a second light beam by the light splitting performance of the polarizationR1、fR2The different space carriers are incident on the surface of the measured mirror and are reflected to a lambda/4 wave plate, after passing through the lambda/4 wave plate, the first light beam and the second light beam are converted into two linearly polarized light beams with orthogonal polarization directions, and both the two linearly polarized light beams reach a second spectroscope, wherein one light beam is completely reflected by the second spectroscope, and the light beam and the part which is reflected by the reference mirror and then penetrates through the second spectroscope pass through a first linear polarizer with a polarization azimuth angle of 45 degrees together to generate first interference light; the other beam of light completely penetrates through the second beam splitter, and passes through a second linear polarizer with the polarization azimuth angle of 45 degrees together with the part reflected by the second beam splitter after being reflected by the reference mirror to generate second interference light; the first interference light is converged by the first imaging objective lens and then enters the first camera to obtain a first interference pattern, the second interference light is converged by the second imaging objective lens and then enters the second camera to obtain a second interference pattern, and the first interference pattern and the second interference pattern are obtained according to the first interference pattern and the second interference patternThe arrangement position of the lambda/4 wave plate determines that the first interference pattern is the first interference pattern or the second interference pattern, and the second interference pattern is the other one of the first interference pattern and the second interference pattern.
2. The transient digital moire phase shifting interferometry device of claim 1, wherein: the light source emits monochromatic linear polarized light, the polarization azimuth angle is 45 degrees, the specific wavelength is determined according to the actual measurement condition, and the beam caliber is selected according to the caliber of the measured range on the measured surface.
3. The transient digital moire phase shifting interferometry apparatus as defined in claim 2, wherein: the first spectroscope is a non-polarizing spectroscope, the working wavelength range of the first spectroscope is selected according to a light source, and the light transmission aperture of the first spectroscope is selected according to the aperture of the measured range on the measured surface.
4. The transient digital moire phase shifting interferometry device of claim 3, wherein: the specific surface shape and the surface flatness of the reference mirror are determined according to actual measurement conditions, and the caliber of the reference mirror is not less than the caliber of a measured range on a measured surface.
5. The transient digital moire phase shifting interferometry device of claim 4, wherein: the polarization grating is a grating with a larger period, and an included angle between two beams of diffracted light obtained by splitting after linearly polarized light is incident is smaller, so that the carrier wave size of the polarization grating ensures that the residual wave front bandwidth is within a limited range; the working wavelength is selected according to the light source, and the caliber is selected according to the caliber of the measured range on the measured surface.
6. The transient digital moire phase shifting interferometry device as defined in claim 5, wherein: the measured mirror is a plane, a spherical surface or an aspheric surface.
7. The transient digital moire phase shifting interferometry device of claim 6, wherein: the fast axis direction of the lambda/4 wave plate ensures that the linearly polarized light converted by one of the left-handed circularly polarized light and the right-handed circularly polarized light after passing through the wave plate is not penetrated by the second spectroscope, the linearly polarized light converted by the other wave plate is not reflected by the second spectroscope, and the caliber of the lambda/4 wave plate is selected according to the caliber of a measured range on a measured surface.
8. The transient digital moire phase shifting interferometry apparatus as defined in claim 7, wherein: the second spectroscope is a polarization spectroscope, one of p-direction polarized light and s-direction polarized light completely penetrates through the second spectroscope, and the other one of the p-direction polarized light and the s-direction polarized light is completely reflected by the second spectroscope; the aperture is selected according to the aperture of the measured range on the measured surface.
9. The transient digital moire phase shifting interferometry apparatus as defined in claim 8, wherein: the polarization directions of the first linear polarizer and the second linear polarizer and the p direction or the s direction form 45 degrees, and the calibers of the first linear polarizer and the second linear polarizer are selected according to the calibers of the measured range on the measured surface; the first imaging objective lens and the second imaging objective lens have the same parameters and indexes, the focal length is selected according to an allowable distance range, the imaging quality comprehensive measurement precision requirement and camera parameters are selected, the working wavelength is selected according to a light source, and the caliber is selected according to the emergent light caliber of the polarization grating; the first camera and the second camera have the same parameters and indexes, the performance of the first camera and the second camera is selected according to the measurement precision requirement, the working wavelength range of the first camera and the second camera is selected according to the light source, and the image surface size of the first camera and the second camera is selected according to the emergent light caliber of the polarization grating and the imaging objective lens parameters.
10. A transient digital moire phase shift interferometry method is characterized in that: which comprises the following steps:
(1) constructing a virtual interference measuring device to obtain the residual wavefront of an ideal system on an image surface
(2) Constructing an actual interference measurement device according to the virtual interference measurement device;
(3) the +1 st order diffraction light and the-1 st order diffraction light are respectively taken as the frequency f by the light splitting performance of the polarization gratingR1、fR2The two beams of interference light are separated by utilizing the polarization beam splitting characteristic of the polarization beam splitting prism, two interference patterns are acquired at one time, and the space carrier f is loadedR1The obtained interference pattern is defined as a first interference pattern, and a space carrier f is loadedR2Defining the obtained interference pattern as a second interference pattern;
(4) and solving a complete error-free measured surface shape by adopting a digital Moire phase-shifting interferometry based on a two-step carrier splicing method, thereby realizing the measurement of the measured surface shape.
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