CN108303038B - Reflection type surface shape measuring method and device based on two-dimensional optical dot matrix - Google Patents
Reflection type surface shape measuring method and device based on two-dimensional optical dot matrix Download PDFInfo
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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
- G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
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- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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Abstract
The method utilizes emergent light modulated by a spatial light modulator and subjected to Fourier transform of two lenses to respectively form optical lattices on a reflection-type measured surface and a reference plane, the optical lattices on the measured surface are subjected to surface shape modulation and then are shifted relative to the reference plane, and the surface shape of the measured surface is reconstructed according to the shift and a mode reconstruction algorithm based on a Zernike polynomial. And further provides a measuring device for implementing the method and application of the method in measuring deformation of an object. The method simplifies the measurement process and realizes quick measurement.
Description
Technical Field
The disclosure relates to the field of optical measurement, and in particular to a reflection-type surface shape measuring method and device based on a two-dimensional optical dot matrix.
Background
The reflecting device is widely applied in the fields of large-scale scientific facilities, microelectronics, modern national defense, medical machinery, scientific instruments, high-end consumer goods and the like, and the influence of the surface shape precision on the performance of equipment is not ignored, so that the precise measurement of the reflecting device is concerned. The advantages of non-contact, high precision, high efficiency and the like of the optical measurement method make the optical measurement method become one of important techniques for surface shape measurement.
The optical non-contact measurement method obtains information on a surface shape of a measured surface by receiving an optical signal modulated by an object, and is classified into an interferometry, an optical probe method, a phase measurement deflection technique, a Hartmann wavefront measurement method, and the like in principle. The interferometry method has the advantages of high longitudinal resolution, high measurement speed and high precision, is easily influenced by a measurement environment, has low transverse resolution and small vertical measurement range, and is not suitable for measuring complex curved surfaces with large surface shape fluctuation; the optical probe method is similar to the traditional mechanical probe method, utilizes the focused light beam to replace a physical probe, has the advantages of no damage, high reliability, high vertical resolution and high precision, but has smaller vertical measurement range and low measurement speed, can only be used for measuring the nano-scale or sub-nano-scale smooth continuous surface, and is not suitable for measuring large-area complex surfaces; the phase measurement deflection technology can be divided into a moire fringe profilometry, a Fourier transform profilometry, a phase shift method and the like according to a phase extraction method, the measured surface shape information is solved through the phase, the speed is high, the stability and the precision are high, the large-field global three-dimensional topography measurement can be realized, but the phase expansion is influenced by factors such as discontinuity of the measured surface shape, noise, lack of fringe sampling and the like, so that the phase expansion has errors, the obtained surface shape information is distorted, and although a plurality of phase expansion algorithms are provided, the phase expansion algorithm is usually only aimed at one kind of interference and cannot meet the general requirements. The Hartmann wavefront measurement method has the advantages of simple structure, high measurement speed, strong environmental interference resistance and the like, and is widely used for measuring large-caliber optical elements. However, since the microlens structure is fixed, the measurement range is also limited, and the measurement flexibility is not high.
Disclosure of Invention
The present disclosure provides a reflection type surface shape measuring method and apparatus based on two-dimensional optical lattice to at least partially solve the above-mentioned technical problems.
According to one aspect of the disclosure, a reflection type surface shape measurement method based on a two-dimensional optical lattice is provided, which includes: enabling emergent light modulated by the spatial light modulator and subjected to Fourier transform of two lenses to form a two-dimensional optical dot matrix on a reference plane reflector, and acquiring a reference two-dimensional optical dot matrix image by an image acquisition element; enabling the same emergent light to form a two-dimensional optical dot matrix on a reflection-type tested surface, and acquiring a tested two-dimensional optical dot matrix image by an image acquisition element; calculating the offset of the optical lattice centroid in the test two-dimensional optical lattice image relative to the optical lattice centroid in the reference two-dimensional optical lattice image in the x direction and the y direction in the rectangular coordinate system; and reconstructing the surface shape of the measured surface by using a mode reconstruction algorithm based on Zernike polynomial according to the calculated offset.
Preferably, the spatial light modulator modulates the incident light according to an optical lattice phase diagram with a periodic structure and outputs the emergent light.
Preferably, the image acquisition element is a CCD camera or a CMOS light sensing element.
Preferably, the offset is calculated by: obtaining the optical lattice centroid coordinates in the reference two-dimensional optical lattice image and the test two-dimensional optical lattice image through a connected region marking algorithm and a weighted pixel average algorithm; marking the optical dot matrix centroid positions of the reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image according to the optical dot matrix centroid coordinates; eliminating the mass centers with incomplete unit cells marked at the image edges of the reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image; and arranging the centroids of the reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image in the same image according to position distribution, and calculating the offset of the centroids of the optical dot matrices.
Preferably, the pattern reconstruction algorithm comprises:
the surface shape W (x, y) of the measured surface is expressed by a linear combination of Zernike polynomials as:
wherein, aiIs the coefficient of a zernike polynomial, ZiIs the i term Zernike polynomial, and k is the term number of the Zernike polynomial;
taking W (x, y) as the derivative of x and y, respectively, yields:
respectively taking the offsets of the m optical lattice centroids generated in the x direction and the y direction as Wx(xj，yj)、Wy(xj，yj) J is 1, 2, 3, L m, and Zernike polynomial coefficients [ α ] are calculated in formula (2)1，α2，Lαk](ii) a And
will be calculated to obtainZernike polynomial coefficient substituted formula
And reconstructing the surface shape of the measured surface.
Preferably, the coefficients of the Zernike polynomials are solved by a least squares method.
As still another aspect of the present invention, there is provided a use of the reflection type surface shape measuring method as described above in measuring deformation of an object.
As still another aspect of the present invention, there is provided a reflection type surface shape measuring apparatus based on a two-dimensional optical lattice, including a spatial light modulator, two lenses, an image pickup element, and a data processing unit, wherein: incident light is subjected to phase modulation by the spatial light modulator and then is output to the two lenses, after Fourier transformation of the two lenses, two-dimensional optical lattices are respectively formed on the reference plane reflector and the tested surface, the reference two-dimensional optical lattice image and the test two-dimensional optical lattice image are respectively collected by the image collecting element,
and the data processing unit is electrically connected to the image acquisition element and used for calculating the offset of the test two-dimensional optical dot matrix image relative to the optical dot matrix centroid in the reference two-dimensional optical dot matrix image according to the acquired reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image and reconstructing the surface shape of the tested surface based on a Zernike polynomial mode reconstruction algorithm.
According to the technical scheme, the reflection type surface shape measuring method and device based on the two-dimensional optical dot matrix have at least one of the following beneficial effects:
(1) the surface shape of the measured surface is calculated by directly utilizing the deformation quantity generated after the optical lattice structure is modulated by the surface shape of the measured surface, the surface shape information does not need to be solved through phase, the measuring process is simplified, and the rapid measurement is realized.
(2) The surface shape of the measured surface can be obtained only by acquiring the reference two-dimensional optical dot matrix image once and acquiring the test two-dimensional optical dot matrix image of the measured surface once in the subsequent measurement process, so that the measurement process is simplified, and the rapid measurement is realized.
(3) The modulation parameters of the spatial light modulator can be changed according to different measurement requirements, so that the pattern and the size of the optical lattice projected onto the measured surface can be changed, the experimental light path does not need to be changed, and the adaptability is strong.
(4) The high-resolution detection of submicron level is realized, the precision is higher, the resolution and the measurement range of the system can be changed by changing the period of the optical lattice, and the design requirement of high-precision and rapid measurement of the reflection surface shape is met.
Drawings
Fig. 1 is a schematic view of a reflection-type surface shape measurement optical path based on a two-dimensional optical lattice according to an embodiment of the disclosure.
FIG. 2 is a diagram of the optical lattice phase input to a spatial light modulator according to an embodiment of the disclosure.
Fig. 3 is a geometric model diagram of a surface shape measurement method according to an embodiment of the present disclosure.
Fig. 4 is a flowchart of a method for measuring a reflection-type surface shape based on a two-dimensional optical lattice according to an embodiment of the disclosure.
Fig. 5(a) is a diagram of an optical lattice being captured by a CCD camera after being irradiated onto a reference plane mirror according to an embodiment of the present disclosure.
Fig. 5(b) is a diagram collected by the CCD camera when the optical lattice is irradiated to the measured inclination.
Fig. 6 is a flow chart of optical dot matrix image processing according to an embodiment of the disclosure.
Fig. 7 is a centroid distribution diagram of an optical lattice of a reference plane and a measured plane acquired by a CCD camera according to an embodiment of the present disclosure.
Fig. 8 is a variation of the optical lattice centroid position in the x-direction for an embodiment of the present disclosure.
FIG. 9 is a variation of the optical lattice centroid position in the y-direction for an embodiment of the present disclosure.
FIG. 10(a) is a measurement profile detected using a zygo interferometer.
Fig. 10(b) is a measurement profile of a reflection-type profile measurement method based on a two-dimensional optical lattice according to an embodiment of the present disclosure.
FIG. 10(c) is a graph showing the difference between the two measured surface profiles of FIGS. 10(a) and 10 (b).
[ description of main reference numerals in the drawings ] of the embodiments of the present disclosure
1-a laser; 2. 3, 7, 10, 12-lens;
4-a spatial light modulator; 5-a half-wave plate;
6-polarization beam splitter prism; 8-mask plate;
9-a polarization beam splitter prism; 11-measured or reference plane;
13-CCD camera.
Detailed Description
The invention discloses a reflection-type surface shape measuring method and a device based on a two-dimensional optical lattice, and the inventive idea is as follows: emergent light modulated by the spatial light modulator and subjected to Fourier transform of the two lenses respectively forms optical lattices on the reflection-type measured surface and the reference plane, the optical lattices on the measured surface are subjected to surface shape modulation of the measured surface and then are shifted relative to the reference plane, and the surface shape of the measured surface is reconstructed according to the shift and a mode reconstruction algorithm based on a Zernike polynomial.
The principle of the optical lattice-based surface shape measurement is as follows:
FIG. 3 is a geometric model diagram of a surface shape measuring method according to an embodiment of the disclosure, and as shown in FIG. 3, a measured surface is first placed horizontally, a point M is a point on the measured surface, and a point H is β having a height change H relative to the point M and inclining in the x directionxPoint (2) of (c). The incident light is normally incident on the measured surface, if the measured surface is a horizontal surface, the reflected light returns in the original path, the light reflected by the point M exits along the HB, is projected to a point B 'on the CCD camera after passing through the imaging system, and the light HA reflected by a point H on the measured surface is projected to a point A' on the CCD camera after passing through the imaging system. Therefore, the theoretical amount of deformation of the optical lattice modulated by the surface profile on the camera imaging plane is a "B". The theoretical deformation quantity A 'B' can be calculated as:
A″B″＝M1M2x·tanβx·tan(2βx)＝ΔSx(ii) a Formula (1)
In the formula (1), x represents the distance between the measured point and the point O.
The point M tilt β in the x-direction was discussed abovexWhen the optical lattice is deformed in the x-direction by the surface-shape modulation, the point M is tilted β in the y-directionyThen, the amount of deformation of the optical lattice received by the CCD camera in the y direction is:
ΔSy＝M1M2x·tanβy·tan(2βy) (ii) a Formula (2)
In the formula (2), x represents the deformation amount of the measured point relative to the O point in the x and y directions, namely the gradient distribution in the x and y directions of the optical lattice, and the surface shape of the measured surface can be obtained by a mode reconstruction method based on Zernike polynomials.
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
As an exemplary embodiment, the reflective surface shape measuring apparatus based on the two-dimensional optical lattice of the present disclosure includes a measuring optical path as shown in fig. 1, and thus the measuring optical path will be described in detail first.
Fig. 1 is a schematic view of a reflection-type surface shape measurement optical path based on a two-dimensional optical lattice according to an embodiment of the disclosure. As shown in fig. 1, a light beam emitted from a laser 1 is expanded and collimated by a lens 2 and a lens 3, and then passes through a polarization beam splitter prism 6 and a half-wave plate 5 to irradiate a spatial light modulator 4, the spatial light modulator 4 modulates and outputs the light beam according to an optical lattice phase diagram (shown in fig. 2) with a certain period and lattice unit size input to the spatial light modulator 4 by a computer, the output light beam is subjected to fourier transform twice by the lens 7 and the lens 10, light of other diffraction orders except for first-order diffracted light is filtered by a mask plate 8 arranged between the lens 7 and the lens 10, an optical lattice is formed on a measured surface or a reference plane 11, and the optical lattice is imaged by the lens 10, the polarization beam splitter prism 9 and the lens 12 and then received by a CCD camera 13.
In this embodiment, the reflection-type surface shape measuring apparatus further includes a data processing unit electrically connected to the CCD camera 13, and configured to calculate, according to the collected reference two-dimensional optical lattice image and the test two-dimensional optical lattice image, an offset of the test two-dimensional optical lattice image with respect to a centroid of the optical lattice in the reference two-dimensional optical lattice image, and reconstruct a surface shape of the measured surface based on a pattern reconstruction algorithm of a Zernike polynomial.
In the present embodiment, based on the above-mentioned reflection-type surface shape measuring apparatus, the present disclosure also provides a reflection-type surface shape measuring method based on a two-dimensional optical lattice, and the following describes the reflection-type surface shape measuring method based on a two-dimensional optical lattice in detail.
Fig. 4 is a flowchart of a method for measuring a reflection-type surface shape based on a two-dimensional optical lattice according to an embodiment of the disclosure. Referring to fig. 4, a method for measuring a reflection-type surface shape based on a two-dimensional optical lattice includes the following steps:
step A: emergent light modulated by the spatial light modulator and subjected to Fourier transform of the two lenses forms a two-dimensional optical dot matrix on the reference plane reflector, and is collected by the CCD camera to obtain a reference two-dimensional optical dot matrix image.
In this embodiment, after a deformable mirror is reset, the surface of the deformable mirror is a plane, and the surface of the deformable mirror is used as a reference plane mirror, and the CCD camera 13 collects a reference optical dot matrix image of the reference plane mirror as shown in fig. 5 (a).
And B: and forming a two-dimensional optical dot matrix on the tested surface by the same emergent light, and acquiring a tested two-dimensional optical dot matrix image by a CCD camera.
In this embodiment, the surface of the deformable mirror is adjusted to be inclined by a certain angle in the x direction, and the surface is used as a surface to be measured, and a CCD camera collects a test optical lattice image of the surface to be measured as shown in fig. 5 (b).
And C: and calculating the offset of the optical lattice centroid in the test two-dimensional optical lattice image relative to the optical lattice centroid in the reference two-dimensional optical lattice image in the x direction and the y direction in a rectangular coordinate system, wherein the offset is equivalent to the gradient distribution of the measured surface in the x direction and the y direction.
In this embodiment, the acquired optical dot matrix image is processed by MATLAB software, so as to obtain the offset of each centroid, which is not limited to using the MATLAB software for image processing, but other general image processing software may also be used, fig. 6 is a flowchart of the optical dot matrix image processing in the embodiment of the present disclosure, please refer to fig. 6, and this step specifically includes the following operations:
firstly, carrying out binarization processing on a reference optical lattice image and a test optical lattice image acquired by a CCD camera by a self-adaptive threshold processing method;
then, finding all connected areas in the binarized image by using a connected component marking algorithm, obtaining position information of a centroid by applying a geometric distance calculation algorithm to each connected area, marking the centroid position, and removing the centroid of an incomplete unit cell marked at the edge of the image;
and finally, arranging the optical dot matrix centroids of the successively collected reference optical dot matrix image and the test optical dot matrix image in the same image according to position distribution, and calculating the offset of the centroid coordinates of each point in the x direction and the y direction.
Referring to fig. 7, fig. 7 is a distribution diagram of the centroids of the optical lattice of the reference plane and the measured plane collected by the CCD camera according to the embodiment of the disclosure, and it can be seen that the centroids of the optical lattice are integrally translated in the x direction and are not changed in the y direction.
In order to observe the rule that the centroid of the lattice in the optical lattice image changes in the x and y directions more clearly, the optical lattice image measured when the height of the measuring reflection surface is 10 μm is selected, the optical lattice corresponding to the 181 th, 194 th, 206 th, 219 th, 232 th and 245 th rows is selected from the optical lattice image, and the change in the centroid position is shown in fig. 8 and 9 by comparing the change in the x and y directions of the centroid position of the optical lattice before and after the inclination of the measured surface.
The comparison shows that the centroid of the optical lattice corresponding to the inclined plane is shifted by a certain distance in the x direction integrally relative to the centroid position of the optical lattice corresponding to the plane, and basically no displacement is generated in the y direction, which is consistent with the inclined plane of the measured plane in the x direction. The offset of the centroid of the optical lattice reflects the gradient distribution of the measured surface, and the surface shape of the measured surface can be reconstructed by using a mode reconstruction method based on Zernike polynomials.
Step D: and reconstructing the surface shape of the measured surface by using a mode reconstruction algorithm based on Zernike polynomials according to the offset of the centroid of the optical lattice of the measured surface in the x direction and the y direction, namely the gradient distribution of the measured surface in the x direction and the y direction.
In this embodiment, the pattern reconstruction algorithm includes the following steps:
first, the surface shape of the measured surface is expressed as a linear combination of Zernike polynomials:
wherein, aiIs the coefficient of a zernike polynomial, ZiIs the i term Zernike polynomial, and k is the term number of the Zernike polynomial;
then, the above formula (3) is differentiated for x and y to obtain
The following equations (4) and (5) are simplified: w ═ Ma; formula (6)
Wherein W ═ Wx(x，y)，Wy(x，y)]′，
α＝[a1，α2，…ak]′，i＝i＝1，2，L k；
Then, the deformation quantities of the known m optical lattices in the x and y directions are respectively delta Sx、ΔSyIs Wx(xj，yj)，Wy(xj，yj) J is 1, 2, 3, … m, is substituted into formula (6),
also known, the Zernike polynomial coefficient [ α ] can be found1，α2，Lαk]；
Finally, the obtained polynomial coefficient is substituted into formula (3) to reconstruct the surface shape of the measured surface, and fig. 10(b) is a measured surface shape of the reflection type surface shape measurement method based on the two-dimensional optical lattice according to the embodiment of the present disclosure.
To better verify the measurement method proposed herein, the surface shape reconstructed by the optical lattice deformation method of this example and a commercial interferometer (GPI of Zygo corporation) were usedTMXP/D, surface shape data measured with a measurement accuracy λ/10 of mean square error RMS, λ 632.8nm (shown in fig. 10 (a)), were compared, and the surface shape difference obtained by subtracting the surface shape data measured by the two measurement methods is shown in fig. 10 (c). It can be seen from the figure that the reconstructed surface shape is consistent with the surface shape measured by a commercial interferometer, and the mean square error RMS of the surface shape obtained by subtracting the surface shape data measured by the two measuring methods is 0.131 μm and is less than one wavelength. Therefore, the feasibility and the accuracy of the surface shape measuring method provided by the disclosure are verified.
It can be understood that the reflection type surface shape measuring method based on the two-dimensional optical lattice can be applied to measuring object deformation, and can carry out quick and accurate measurement.
So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. Furthermore, the above definitions of the various elements and methods are not limited to the particular structures, shapes or arrangements of parts mentioned in the examples, which may be easily modified or substituted by one of ordinary skill in the art, for example: the CCD camera may also be replaced with other image pickup elements such as a CMOS camera or the like.
In summary, the present disclosure provides a method and an apparatus for measuring a reflective surface shape based on a two-dimensional optical lattice, which calculate a surface shape of a measured surface by using a deformation amount generated after an optical lattice structure is modulated by the surface shape of the measured surface.
It is noted that the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify a corresponding element does not by itself connote any ordinal number of the element or any ordering of one element from another or the order of manufacture, and the use of the ordinal numbers is only used to distinguish one element having a certain name from another element having a same name.
In addition, unless steps are specifically described or must occur in sequence, the order of the steps is not limited to that listed above and may be changed or rearranged as desired by the desired design. The embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e., technical features in different embodiments may be freely combined to form further embodiments.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (8)
1. A reflection type surface shape measuring method based on a two-dimensional optical lattice comprises the following steps:
enabling emergent light modulated by the spatial light modulator and subjected to Fourier transform of two lenses to form a two-dimensional optical dot matrix on a reference plane reflector, and acquiring a reference two-dimensional optical dot matrix image by an image acquisition element;
enabling the same emergent light to form a two-dimensional optical dot matrix on a reflection-type tested surface, and acquiring a tested two-dimensional optical dot matrix image by an image acquisition element;
calculating the offset of the optical lattice centroid in the test two-dimensional optical lattice image relative to the optical lattice centroid in the reference two-dimensional optical lattice image in the x direction and the y direction in the rectangular coordinate system; and
and reconstructing the surface shape of the measured surface by using a mode reconstruction algorithm based on Zernike polynomial according to the calculated offset.
2. The reflection type surface shape measuring method according to claim 1, wherein the spatial light modulator modulates incident light according to an optical lattice phase pattern having a periodic structure and outputs outgoing light.
3. The reflection type surface shape measuring method according to claim 1, wherein the image pickup element is a CCD camera or a CMOS photosensitive element.
4. The reflection type surface shape measurement method according to claim 1, wherein the offset amount is calculated by:
obtaining the optical lattice centroid coordinates in the reference two-dimensional optical lattice image and the test two-dimensional optical lattice image through a connected region marking algorithm and a weighted pixel average algorithm;
marking the optical dot matrix centroid positions of the reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image according to the optical dot matrix centroid coordinates;
eliminating the mass centers with incomplete unit cells marked at the image edges of the reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image; and
and arranging the centroids of the reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image in the same image according to position distribution, and calculating the offset of the centroids of the optical dot matrices.
5. The reflective surface shape measurement method of claim 1, wherein the pattern reconstruction algorithm comprises:
the surface shape W (x, y) of the measured surface is expressed by a linear combination of Zernike polynomials as:
wherein, aiIs the coefficient of a zernike polynomial, ZiIs the i term Zernike polynomial, and k is the term number of the Zernike polynomial;
taking W (x, y) as the derivative of x and y, respectively, yields:
respectively taking the offsets of the m optical lattice centroids generated in the x direction and the y direction as Wx(xj，yj)、Wy(xj，yj) J is 1, 2, 3, L m, and Zernike polynomial coefficients [ α ] are calculated in formula (2)1，α2，Lαk](ii) a And
substituting the Zernike polynomial coefficient obtained by calculation into formula
And reconstructing the surface shape of the measured surface.
6. The reflection type surface shape measurement method according to claim 5, wherein the coefficients of Zernike polynomials are solved by a least square method.
7. Use of the reflection type surface shape measuring method according to any one of claims 1 to 6 for measuring deformation of an object.
8. A reflection-type surface shape measuring device based on a two-dimensional optical lattice comprises a spatial light modulator, two lenses, an image acquisition element and a data processing unit, wherein:
incident light is subjected to phase modulation through the spatial light modulator and then is output to the two lenses, after Fourier transformation of the two lenses, two-dimensional optical lattices are respectively formed on the reference plane reflecting mirror and the tested surface, and the reference two-dimensional optical lattice image and the test two-dimensional optical lattice image are respectively collected by the image collecting element;
and the data processing unit is electrically connected to the image acquisition element and used for calculating the offset of the test two-dimensional optical dot matrix image relative to the optical dot matrix centroid in the reference two-dimensional optical dot matrix image according to the acquired reference two-dimensional optical dot matrix image and the test two-dimensional optical dot matrix image and reconstructing the surface shape of the tested surface based on a Zernike polynomial mode reconstruction algorithm.
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| CN108303038A (en) | 2018-07-20 |
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