CN113847880B - High-precision measurement method for three-dimensional deformation of mirror surface - Google Patents
High-precision measurement method for three-dimensional deformation of mirror surface Download PDFInfo
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- G—PHYSICS
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/165—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of a grating deformed by the object
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Abstract
The application provides a high-precision measurement method for three-dimensional deformation of a mirror surface, and relates to the technical fields of material testing and optical experiments. The method comprises the following steps: s1, arranging a measuring system; s2, adjusting an imaging system and calibrating; s3, acquiring an image sequence; s4, calculating. The application carries out channel separation on each picture acquired by the color camera, and each group of single-channel pictures is obtained under the same angle and the same state at the same time without considering the problems of synchronous triggering, environment and the like, so the method eliminates all factors possibly influencing the measurement result, greatly improves the measurement precision, and can realize non-contact nondestructive three-dimensional measurement on the mirror surface measured object by adopting a single camera.
Description
Technical Field
The application relates to the technical field of material testing and optical experiments, in particular to a high-precision measurement method for three-dimensional deformation of a mirror surface.
Background
With the development of scientific technology, mirror objects are widely applied to the fields of optical reflector manufacturing, semiconductor industry, polishing mold manufacturing and the like, so that the detection requirement on the mechanical properties of the mirror objects is more and more urgent.
At present, the detection methods of the mirror deformation adopted by various optical processing detection centers at home and abroad mainly comprise a contour measurement method and an interferometry method, wherein the contour measurement method has the defects of low sampling density, long detection time and the like, and cannot meet engineering requirements; while interferometer detection has high accuracy, the requirements on the measuring environment are high, and common industrial application is difficult to realize. In addition, the measured mirror surface has the problems that the surface is smooth, speckle spraying is not suitable, the reflectivity of light is high, the mirror surface is easy to damage after contact and the like, so the measured mirror surface has certain difficulty in measuring the displacement and deformation of a mirror surface object.
In the prior art, at least two cameras are needed for three-dimensional measurement of the deformation of the mirror surface, and the measurement is performed by using a binocular vision method. However, the method needs to solve the problems of camera calibration, overlapping view field adjustment, synchronous triggering of multiple cameras and the like. If the single-phase machine can perform three-dimensional measurement on the deformation of the mirror surface, the problems of synchronous triggering, environment and the like do not need to be considered, and the measurement accuracy can be greatly improved.
However, currently, a single camera is used to measure a specular object, and only in-plane displacement/deformation measurement is possible, but out-of-plane displacement/deformation cannot be measured. Therefore, a single camera cannot reconstruct the three-dimensional object to be measured, cannot acquire three-dimensional point cloud information, cannot recover the three-dimensional shape of the object to be measured, and cannot perform three-dimensional measurement on mirror deformation.
Disclosure of Invention
(one) solving the technical problems
Aiming at the defects of the prior art, the application provides a high-precision measurement method for three-dimensional deformation of a mirror surface, which solves the problem that a single-phase camera cannot perform nondestructive and non-contact three-dimensional measurement on the deformation of the mirror surface.
(II) technical scheme
In order to achieve the above purpose, the application is realized by the following technical scheme:
a method for high-precision measurement of three-dimensional deformation of a mirror surface, the method comprising the steps of:
s1, arranging a measuring system:
placing a diffuse reflection plate right in front of a detected mirror surface, aligning a DLP projector with the diffuse reflection plate, and aligning a color camera with the detected mirror surface;
s2, adjusting an imaging system and calibrating:
the DLP projector projects a composite image formed by speckles and sinusoidal gratings to the diffuse reflection plate and then reflects the composite image to the mirror surface to be measured, so that the color camera can acquire the composite image on the surface of the mirror surface to be measured, and the aperture and focal length of the color camera are adjusted, so that after the speckles image and the grating image in the composite image can be clearly imaged, the calibration of the color camera and the projector is carried out, and the classical Zhang's checkerboard calibration method is adopted, and as the single camera is adopted for acquisition, only any channel of the 3CCD color camera is required to be calibrated;
s3, acquiring an image sequence:
acquiring a composite image of the measured mirror surface when the deformation is not loaded by a color camera as a reference composite image, and acquiring a composite image sequence of the measured mirror surface in each loading state;
s4, calculating:
s4.1, separating and extracting a speckle image and a grating image from a composite image acquired by a color camera through a channel;
s4.2, tracking characteristic points through a digital image correlation algorithm to obtain in-plane displacement (d) after mirror deformation x ,d y ) Further obtaining in-plane deformation through further calculation;
s4.3, measuring height information h recorded by the projection grating by utilizing an optical triangulation method, subtracting the height information after deformation from the height information of the reference grating image to obtain out-of-plane displacement, further obtaining out-of-plane deformation, and finally realizing three-dimensional deformation measurement of the single-camera mirror surface.
Preferably, the horizontal included angle beta epsilon (25 degrees, 35 degrees) between the shooting direction of the color camera and the normal direction of the detected mirror surface.
Preferably, the speckle image is a blue speckle image; the grating image is a green sine grating image.
Preferably, in the step S3, four composite images are acquired in each loading state, then blue-green channel separation is performed, the obtained speckle image and the grating image with the phase difference pi/2 are respectively calculated, three-dimensional point cloud information of each step is obtained, and finally three-dimensional measurement and three-dimensional shape reconstruction of mirror deformation are completed.
Preferably, in the step S4, the feature point tracking includes: finding a point P (x) on the reference speckle image in the deformed speckle image 0 ,y 0 ) And Q (x) 1 ,y 1 ) Point P' (x) where correlation coefficient is maximum 0 ',y 0 ') and Q' (x) 1 ',y 1 ' s); selecting square subregions with the size of (2m+1) x (2m+1) from the reference speckle images as calculation subregions, and searching out the position with the largest correlation coefficient with each point on the reference speckle images from each deformed speckle image through a matching function, wherein the matching function is as follows:
wherein f (x) i ,y j ) Representing the sub-region gray scale distribution, g (x' i ,y' j ) Representing the sub-region gray scale distribution of the deformed speckle image,and->Representing the average gray values of the sub-regions of the reference speckle image and the deformed speckle image, respectively, wherein a closer C value to the value 1 indicates a greater correlation of the two points.
Preferably, in S4, the in-plane displacement P (d x ,d y )＝(x 0 '-x 0 ,y 0 '-y 0 ) In-plane displacement of point Q (d x ,d y )＝(x 1 '-x 1 ,y 1 '-y 1 )。
Preferably, in the step S4, the measured mirror surface is disposed on a reference plane of XOY, and the Z direction represents the height direction of the measured mirror surface, wherein O C 、O P The method comprises the steps that the center of a compound image on a light center of a color camera and a diffuse reflection plate is respectively, T is any point on the surface of a detected mirror, T' is the projection of a point T on a reference surface, k is the geometric distance between the light center of the color camera and the center of the compound image on the diffuse reflection plate, n is the vertical distance between the center of the compound image on the diffuse reflection plate and the reference surface, and A, B two points refer to that a light beam originally projected at a point B moves to the point A due to deformation of the surface of the detected mirror; the following formula is adopted for the projection grating measurement height information:
wherein p is the fringe spacing,comprising and quiltThe highly correlated phase information of the mirror surface is measured,
for the four projected patterns, the phase formula solved according to the sinusoidal grating is as follows:
wherein I is e (x, y) represents the light intensity of the acquired e-th phase shift map.
(III) beneficial effects
The application provides a high-precision measurement method for three-dimensional deformation of a mirror surface. Compared with the prior art, the method has the following beneficial effects:
the application carries out channel separation on each picture acquired by the color camera, and each group of single-channel pictures is obtained under the same angle and the same state at the same time without considering the problems of synchronous triggering, environment and the like, so the method eliminates all factors possibly influencing the measurement result, greatly improves the measurement precision, and can realize non-contact nondestructive three-dimensional measurement on the mirror surface measured object by adopting a single camera.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a measurement system according to an embodiment of the present application;
FIG. 2 is a composite image, a speckle image and a raster image after separation of channels, wherein a is the composite image, b is the speckle image, and c is the raster image;
FIG. 3 is a schematic diagram of a digital image correlation measurement in an embodiment of the application;
FIG. 4 is a schematic diagram of depth information measurement by a projection grating triangulation method according to an embodiment of the present application;
fig. 5 is a diagram showing the geometry of in-plane deformation measurement according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application are clearly and completely described, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The embodiment of the application solves the problem that a single-phase camera cannot perform nondestructive non-contact three-dimensional measurement on the mirror surface deformation by providing the high-precision measurement method for the mirror surface three-dimensional deformation.
The technical scheme in the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
according to the embodiment of the application, each picture acquired by the color camera is subjected to channel separation, and each group of single-channel pictures are obtained under the same angle and the same state at the same time, and the problems of synchronous triggering, environment and the like are not needed to be considered, so that the method eliminates all factors possibly influencing the measurement result, greatly improves the measurement precision, and can realize non-contact nondestructive three-dimensional measurement on a mirror surface measured object by adopting a single camera.
In addition, the DLP projector projects a composite image consisting of speckles and sinusoidal gratings to the diffuse reflection plate and then reflects the composite image to the detected mirror surface, the channels are separated after the color camera collects the image reflected by the detected mirror surface, the three-dimensional deformation measurement of the detected mirror surface can be realized by the speckle measurement in-plane deformation and the grating measurement out-of-plane deformation through the single color camera, the system has simple structure, the method is simple and easy to implement, the utilized optical measurement method can realize full-field, non-contact and nondestructive detection, and the three-dimensional shape reconstruction of the detected mirror surface can be completed according to the projection gratings.
Moreover, the image size can be adaptively adjusted according to the size of the measured object by adopting a projector to project the image, the measurement is completed under the condition of not losing the resolution, the measurement precision is improved, and the screen refractive index error when the traditional LCD screen projects the image can be avoided by adopting the diffuse reflection plate.
In order to better understand the above technical solutions, the following detailed description will refer to the accompanying drawings and specific embodiments.
Examples:
as shown in fig. 1 and 2, the present application provides a high-precision measurement method for three-dimensional deformation of a mirror surface, which comprises the following steps:
s1, arranging a measuring system:
placing a diffuse reflection plate right in front of a detected mirror surface, aligning a DLP projector with the diffuse reflection plate, and aligning a color camera with the detected mirror surface;
s2, adjusting an imaging system and calibrating:
the DLP projector projects a composite image formed by speckles and sinusoidal gratings to the diffuse reflection plate and then reflects the composite image to the mirror surface to be measured, so that the color camera can acquire the composite image on the surface of the mirror surface to be measured, and the aperture and focal length of the color camera are adjusted, so that after the speckles image and the grating image in the composite image can be clearly imaged, the calibration of the color camera and the projector is carried out, and the classical Zhang's checkerboard calibration method is adopted, and as the single camera is adopted for acquisition, only any channel of the 3CCD color camera is required to be calibrated;
s3, acquiring an image sequence:
acquiring a composite image of the measured mirror surface when the deformation is not loaded by a color camera as a reference composite image, and acquiring a composite image sequence of the measured mirror surface in each loading state;
s4, calculating:
s4.1, separating and extracting a speckle image and a grating image from a composite image acquired by a color camera through a channel;
s4.2, tracking characteristic points through a digital image correlation algorithm to obtain in-plane displacement (d) after mirror deformation x ,d y ) Further obtaining in-plane deformation through further calculation;
s4.3, measuring height information h recorded by the projection grating by utilizing an optical triangulation method, subtracting the height information after deformation from the height information of the reference grating image to obtain out-of-plane displacement, further obtaining out-of-plane deformation, and finally realizing three-dimensional deformation measurement of the single-camera mirror surface.
The method can realize the three-dimensional deformation measurement of the measured mirror surface by adopting a single color camera, has simple system structure and simple and easy method, can realize full-field, non-contact and nondestructive detection by using the optical measurement method, and can also finish the three-dimensional shape reconstruction of the measured mirror surface according to the projection grating.
Compared with the method for measuring three-dimensional deformation by multi-vision, the method performs channel separation on each picture acquired by the color camera, and each group of single-channel pictures are obtained at the same angle and in the same state at the same time, and the problems of synchronous triggering, environment and the like do not need to be considered, so that the method eliminates all factors possibly influencing the measurement result, and greatly improves the measurement precision.
As shown in fig. 1, the horizontal included angle beta epsilon (25 degrees, 35 degrees) between the shooting direction of the color camera and the normal direction of the detected mirror surface. The positioning can calculate depth information by utilizing an optical trigonometry to complete calculation of deformation information and complete three-dimensional information reconstruction.
As shown in fig. 2, the speckle image is a blue speckle image, and in-plane displacement information is recorded; the grating image is a green sine grating image, and out-of-plane displacement information is recorded. The method is used for comprehensively calculating three-dimensional deformation information and three-dimensional morphology reconstruction, and effectively avoiding the mutual interference of gray information among image channels acquired by a color camera.
In the step S3, four composite images are acquired in each loading state because four-step phase shift images of the green grating are required to be obtained, then blue-green channel separation is carried out, the obtained speckle images and the grating images with the phase difference of pi/2 are respectively calculated, three-dimensional point cloud information of each step is obtained, and finally three-dimensional measurement and three-dimensional morphology reconstruction of mirror deformation are completed.
As shown in FIG. 3In S4, the feature point tracking includes: finding a point P (x) on the reference speckle image in the deformed speckle image 0 ,y 0 ) And Q (x) 1 ,y 1 ) Point P' (x) where correlation coefficient is maximum 0 ',y 0 ') and Q' (x) 1 ',y 1 ' s); because the single-point matching can possibly generate the phenomenon of mismatching during calculation, generally, a square subarea with the size of (2m+1) x (2m+1) is selected as a calculation subarea on a reference speckle image, and the position with the largest correlation coefficient with each point on the reference speckle image is searched out for matching by a matching function for each deformed speckle image, wherein the matching function is as follows:
wherein f (x) i ,y j ) Representing the sub-region gray scale distribution, g (x' i ,y' j ) Representing the sub-region gray scale distribution of the deformed speckle image,and->Representing the average gray values of the sub-regions of the reference speckle image and the deformed speckle image, respectively, wherein a closer C value to the value 1 indicates a greater correlation of the two points.
In S4, the in-plane displacement P (d x ,d y )＝(x 0 '-x 0 ,y 0 '-y 0 ) In-plane displacement of point Q (d x ,d y )＝(x 1 '-x 1 ,y 1 '-y 1 )。
As shown in FIG. 4, the mirror surface to be measured is placed on the reference plane of XOY, and the Z direction represents the height direction of the mirror surface to be measured, wherein O C 、O P The center of the composite image on the optical center and the diffuse reflection plate of the color camera respectively, T is any point on the surface of the detected mirror surface, T' is the projection of the point T on the reference surface, and k is the color cameraThe geometric distance between the center of the composite image on the diffuse reflection plate and the center of the composite image on the diffuse reflection plate, n is the vertical distance between the center of the composite image on the diffuse reflection plate and the reference surface, and A, B two points refer to that the light beam originally projected at the point B moves to the point A due to the deformation of the surface of the detected mirror surface;
the following formula can be used for measuring height information of the projection grating:
wherein p is the fringe spacing,contains phase information relating to the height of the mirror surface being measured,
for the four projected patterns, the phase formula solved according to the sinusoidal grating is as follows:
wherein I is e (x, y) represents the light intensity of the acquired e-th phase shift map.
As shown in FIG. 5, in S4.2, the in-plane deformation is calculated by deriving a mirror deformation formula by using a projection speckle pattern, and any speckle pattern Q projected onto the mirror surface 1 Regarded as a point P in an image projected into a diffuse reflection plate by a DLP projector 0 The image on the mirror surface is L is a CCD upper lens, C is a CCD target surface, the distance between L and C is L, M is a measured mirror surface, O is the optical center of the lens, and point P 0 P finally imaged on CCD by plane mirror reflection 1 ' on top of it, however, mirror distortion causes displacement of the feature points to cause P on the CCD 0 The imaging position of the point shifts by delta u, so that the characteristic point imaging shift caused by the local loading deformation of the mirror surface is equivalent to one facet M on the mirror surface to be point Q for the convenience of calculation 1 For the imaging offset of the feature point, theta, caused by the tiny rotation of the rotation center to the M' position x Or theta y Is equal to the local normal direction change in the x or y direction and the angle of rotation about the x and y axes. We have established a coordinate system to better describe the rotation of the mirror, where the normal is the z-axis direction, the y-axis direction coincides with the mirror direction, and the x-axis direction is perpendicular to the y-z plane, thus θ in fig. 5 x For an equivalent rotation angle of rotation about x, M' is an equivalent rotating mirror.
The mirror surface to be measured is placed perpendicular to the optical axis of the camera, meanwhile, the projector image can be adjusted to be completely and clearly displayed on the diffuse reflection plate, the mirror surface is placed parallel to the diffuse reflection plate, the speckle image on the diffuse reflection plate can completely cover the mirror surface, and the focal length and the aperture of the camera lens are adjusted to enable the camera lens to be clearly imaged on the CCD.
As shown in fig. 5, it is assumed that the rotation amount in the x-direction is θ x According to the law of reflection, then corresponds to P 1 Around Q 1 Point rotation 2 theta x To P 2 Then < P- 1 Q 1 P 2 ＝2θ x Let P be 1 ' and P 2 The included angle between imaging rays isThen according to the geometric relationshipSince the mirrors M to M' are rotated, P is set 0 Q 1 ＝P 1 Q 1 ＝P 2 Q 1 ＝t，OQ 2 S, wherein the values of t and s can be obtained by physical measurement and camera calibration, and can be obtained from a simple geometric relationship
The focal length of the lens L is f, the gaussian imaging formula can be expressed as:
since the mirror plane M rotates around the x-axis, the equivalent rotation angle θ can be obtained according to the formulas (1) (2) x The relation of (2) is:
2tf*θ x ＝r(t+s-f)Δu (3)
where r is a scaling factor, which can be determined by camera calibration. Equivalent mirror surface rotation theta around y-axis y When the imaging offset of the light source point on the CCD is Deltav, the same can be obtained:
2tf*θ y ＝k(t+s-f)Δv (4)
the meaning of the remaining parameters in equation (4) is the same as that of equation (3).
Since we already know θ x And theta y If the value of (2) is set to a deformation gradient (DeltaS ') in the x, y direction' x ，ΔS' y ) Let the surface shape before and after the mirror deformation be S 1 (x, y) and S 2 (x, y), then Δs=s 2 -S 1 . Taking into account the properties of deformed mirror surfaces, S 1 And S is 2 Are all microminiaturizable, so S 1 And S is 2 The normal vector of (2) can be expressed as:
due to the included angle theta between the two planes x S is therefore 1 And S is 2 The normal vector included angle of (2) is also theta x The method comprises the following steps:
due to DeltaS y ＝S' 1y -S' 2y And due to the rotation angle theta x And theta y The value is small, so that the formula (6) is simplified, and the simplified result is brought into the formula (3) and the formula (4) to obtain:
the deformation Δs is constructed from the partial derivative of Tikhonov deconvolution as:
wherein F { } and F -1 { } sum is fourier transform and inverse fourier transform, respectively, λ and μ are frequency domain coordinates, and i is complex unit of fourier transform.
In summary, compared with the prior art, the application has the following beneficial effects:
1. compared with multi-vision measurement of three-dimensional deformation, the method provided by the embodiment of the application has the advantages that each image acquired by the color camera is subjected to channel separation, and each group of single-channel images are acquired at the same angle and in the same state at the same time, and the problems of synchronous triggering, environment and the like are not needed to be considered, so that the method eliminates all factors possibly influencing the measurement result, greatly improves the measurement precision, and can realize non-contact nondestructive three-dimensional measurement on a mirror surface measured object by adopting a single camera.
2. In the embodiment of the application, the DLP projector projects a composite image consisting of speckles and sinusoidal gratings to the diffuse reflection plate and then reflects the composite image to the detected mirror, the channels are separated after the color camera collects the image reflected by the detected mirror, the in-plane deformation is measured through the speckles, the out-of-plane deformation is measured through the grating, the three-dimensional deformation measurement of the detected mirror can be realized through only a single color camera, the system structure is simple, the method is simple and easy, the utilized optical measurement method can realize full-field, non-contact and nondestructive detection, and the three-dimensional shape reconstruction of the detected mirror can be completed according to the projection gratings.
3. In the embodiment of the application, the image size can be adaptively adjusted according to the size of the measured object by adopting a projector to project the image, the measurement is completed under the condition of not losing the resolution, the measurement precision is improved, and the screen refractive index error when the image is projected by adopting the diffuse reflection plate can also be avoided when the image is projected by adopting the traditional LCD screen.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (5)
1. A method for measuring three-dimensional deformation of a mirror surface with high precision, the method comprising the steps of:
s1, arranging a measuring system:
placing a diffuse reflection plate right in front of a detected mirror surface, aligning a DLP projector with the diffuse reflection plate, and aligning a color camera with the detected mirror surface;
s2, adjusting an imaging system and calibrating:
the DLP projector projects a composite image formed by speckles and sinusoidal gratings to the diffuse reflection plate and then reflects the composite image to the detected mirror surface, so that the color camera can acquire the composite image on the detected mirror surface, and the aperture and focal length of the color camera are adjusted, so that after the speckles image and the grating image in the composite image can be clearly imaged, the color camera and the projector are calibrated;
s3, acquiring an image sequence:
acquiring a composite image of the measured mirror surface when the deformation is not loaded by a color camera as a reference composite image, and acquiring a composite image sequence of the measured mirror surface in each loading state;
s4, calculating:
s4.1, separating and extracting a speckle image and a grating image from a composite image acquired by a color camera through a channel;
s4.2, tracking characteristic points through a digital image correlation algorithm to obtain in-plane displacement (d) after mirror deformation x ,d y ) Further obtaining in-plane deformation through further calculation;
s4.3, measuring height information h recorded by a projection grating by utilizing an optical triangulation method, subtracting the height information after deformation from the height information of a reference grating image to obtain out-of-plane displacement, further obtaining out-of-plane deformation, and finally realizing three-dimensional deformation measurement of a single-camera mirror surface;
in the step S4, the feature point tracking includes: finding a point P (x) on the reference speckle image in the deformed speckle image 0 ,y 0 ) And Q (x) 1 ,y 1 ) Point P' (x) where correlation coefficient is maximum 0 ',y 0 ') and Q' (x) 1 ',y 1 ' s); selecting square subregions with the size of (2m+1) x (2m+1) from the reference speckle images as calculation subregions, and searching out the position with the largest correlation coefficient with each point on the reference speckle images from each deformed speckle image through a matching function, wherein the matching function is as follows:
wherein f (x) i ,y j ) Representing the sub-region gray scale distribution, g (x i ',y' j ) Representing the sub-region gray scale distribution of the deformed speckle image,and->Respectively representing average gray values of a sub-region of the reference speckle image and a sub-region of the deformed speckle image, wherein the closer the C value is to the value 1, the larger the correlation between the two points is;
in S4, the in-plane displacement P (d x ,d y )＝(x 0 '-x 0 ,y 0 '-y 0 ) In-plane displacement of point Q (d x ,d y )＝(x 1 '-x 1 ,y 1 '-y 1 )。
2. The method for measuring three-dimensional deformation of a mirror surface according to claim 1, wherein a horizontal included angle β∈ (25 °,35 °) between a photographing direction of the color camera and a normal direction of the mirror surface to be measured.
3. A method for high-precision measurement of three-dimensional deformation of a mirror surface according to claim 1, wherein the speckle image is a blue speckle image; the grating image is a green sine grating image.
4. The method for measuring three-dimensional deformation of a mirror surface according to claim 1, wherein in the step S3, four composite images are obtained in each loading state, then blue-green channel separation is performed, the obtained speckle image and the grating image with the phase difference of pi/2 are respectively calculated, three-dimensional point cloud information of each step is obtained, and finally three-dimensional measurement and three-dimensional morphology reconstruction of the mirror surface deformation are completed.
5. The method for measuring three-dimensional deformation of a mirror surface according to claim 4, wherein in S4, the mirror surface to be measured is placed on a reference plane of XOY, and the Z direction represents a height direction of the mirror surface to be measured, wherein O C 、O P The center of the composite image on the optical center and the diffuse reflection plate of the color camera respectively, T is any point on the surface of the detected mirror surface, T' is the projection of the point T on the reference surface, and k is the color cameraThe geometric distance between the center of the composite image on the diffuse reflection plate and the center of the composite image on the diffuse reflection plate, n is the vertical distance between the center of the composite image on the diffuse reflection plate and the reference surface, and A, B two points refer to that the light beam originally projected at the point B moves to the point A due to the deformation of the surface of the detected mirror surface; the following formula is adopted for the projection grating measurement height information:
wherein p is the fringe spacing,contains phase information relating to the height of the mirror surface being measured,
for the four projected patterns, the phase formula solved according to the sinusoidal grating is as follows:
wherein I is e (x, y) represents the light intensity of the acquired e-th phase shift map.
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| CN102607466A (en) * | 2012-03-29 | 2012-07-25 | 天津大学 | Grating projection rapid non-contact measurement method and device for high-reflectance free-form curved-surface parts |
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| CN112097670A (en) * | 2020-08-27 | 2020-12-18 | 江苏科技大学 | Method and equipment for measuring three-dimensional surface shape of high-reflectivity object |
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| CN102607466A (en) * | 2012-03-29 | 2012-07-25 | 天津大学 | Grating projection rapid non-contact measurement method and device for high-reflectance free-form curved-surface parts |
| WO2016188068A1 (en) * | 2015-05-27 | 2016-12-01 | 珠海真幻科技有限公司 | Method and system for stereoscopic vision three-dimensional measurement taking computing laser speckles as texture |
| CN112097670A (en) * | 2020-08-27 | 2020-12-18 | 江苏科技大学 | Method and equipment for measuring three-dimensional surface shape of high-reflectivity object |
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