CN114322838B - Small coincidence field multi-eye phase deflection measurement method - Google Patents
Small coincidence field multi-eye phase deflection measurement method Download PDFInfo
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Abstract
The application provides a small coincidence view field multi-eye phase deflection measuring device and method. The foregoing apparatus, comprising: a phase object, an imaging system and a control computer; the phase object and the imaging system are respectively connected with the control computer through a data link; a phase object for projecting first phase information; the imaging system is used for acquiring second phase information of the phase object display; and the control computer is used for calibrating the geometric relationship between the phase object and the imaging system, controlling the phase object and the imaging system to operate, acquiring second phase information, and generating the surface shape of the curved surface to be detected in the phase object based on the geometric relationship and the second phase information. The application provides a little coincidence field of vision many meshes phase deflection measuring device can be under the unknown condition of the curved surface design face that need not just design with the help of the priori knowledge of design face shape and await measuring, can carry out alone measurement or full field of vision to unknown curved surface respectively with the help of many meshes imaging system coincidence field of vision and many meshes imaging system field of vision.
Description
Technical Field
The application relates to the technical field of precision vision measurement, in particular to a small coincidence view field multi-eye phase deflection measurement method.
Background
The phase measurement deflection technology is a mirror surface shape method which has a large dynamic range and can realize non-contact measurement on a free-form surface without a compensation mirror. The phase measurement deflection technique is divided into monocular phase measurement deflection technique and monocular phase measurement deflection technique.
The working principle of the phase measurement deflection technology is that firstly, structured light coding information containing phase information is projected to a measured surface through a phase object, and after the coding information is modulated and reflected by the measured surface, a camera shoots a deformed structured light coding pattern through an imaging system; secondly, recovering absolute phase information according to a corresponding decoding algorithm, and acquiring a corresponding relation between a camera pixel and a phase object coordinate; and finally, acquiring the surface shape of the surface to be measured according to the geometric relation and constraint conditions among the camera pixels, the phase object, the vector height of the surface to be measured and the normal vector. In the common monocular phase measurement, the method based on Delaunay triangulation and
-performing reconstruction iteration of the curved surface by means of Trumbore line-surface intersection. However, the multi-view phase-shift technique can calculate the surface shape of the curved surface to be measured by constraining the geometrical relationship among the plurality of imaging systems, the phase object, the vector height of the object to be measured and the normal vector.
The above conventional phase measurement deflection techniques have disadvantages or shortcomings including: the monocular measurement of the measured surface shape is realized by means of the prior knowledge of the designed surface shape; meanwhile, the technology of respectively carrying out independent measurement or full-field measurement on the superposed view field of the multi-view imaging system and the view field of the multi-view imaging system without the need of surface shape prior knowledge of the curved surface to be measured does not exist.
Disclosure of Invention
Aiming at the problems in the prior art, the embodiment of the application provides a small coincidence field multi-view phase deflection measuring method.
The application provides a little coincidence field of view many meshes phase deflection measuring device includes: a phase object, an imaging system and a control computer;
the phase object and the imaging system are respectively connected with the control computer through data links;
the phase object is used for projecting first phase information;
the imaging system is used for acquiring the second phase information displayed by the phase object;
the control computer is used for calibrating the geometric relationship between the phase object and the imaging system, controlling the phase object and the imaging system to operate, acquiring the second phase information, and generating the surface shape of the curved surface to be detected in the phase object based on the geometric relationship and the second phase information.
According to the small coincidence field multi-view phase deflection measuring device provided by the application, the number of the phase objects is not less than one.
According to the utility model provides a little coincidence field of view multiocular phase deflection measuring device, phase place object includes: a planar phase object and/or a curved phase object with a surface shape.
According to the present application, the small coincidence field of view multiocular phase deflection measuring device, the first phase information projected by the phase object includes: visible light information, infrared light information, and/or ultraviolet light information.
According to the multiocular phase deflection measuring device with the small coincidence view field, the number of the imaging systems is not less than two, and the view field coincidence exists between the imaging systems.
According to the application provides a little coincidence field of view multiocular phase deviation measuring device, imaging system includes: a non-telecentric imaging system and/or a telecentric imaging system.
The present application further provides a small coincidence field multi-view phase deflection measuring method, which is used for any one of the small coincidence field multi-view phase deflection measuring devices, and includes:
calibrating the geometric relation between the phase object and the imaging system;
controlling the phase object to project first phase information, and controlling the imaging system to acquire second phase information displayed by the phase object;
and acquiring the second phase information, and generating the surface shape of the curved surface to be detected in the phase object based on the geometric relationship and the second phase information.
According to the small coincidence view field multi-view phase deflection measurement method provided by the application, before controlling the imaging system to acquire the second phase information displayed by the phase object, the method comprises the following steps:
defining pixel coordinates of a first pixel point in the imaging system, acquiring a plurality of target points on the curved surface to be detected based on the pixel coordinates, and constructing a basic point set based on the target points;
selecting a second pixel point in the basic point set, determining the second pixel point as an anchor point, determining an initial solution of the curved surface to be detected based on the anchor point, and acquiring a corresponding relation of the first pixel point to a pixel position point based on the first phase information and the initial solution;
determining an intersection point of the incident ray corresponding to the first pixel point and the initial solution, and determining the pixel position point corresponding to the first pixel point based on the corresponding relation; performing region reconstruction based on the first pixel point, the intersection point and the pixel position point to generate a first height map;
forming the second phase information based on the first height map.
According to the small coincidence field multi-view phase deflection measurement method provided by the application, the generating of the surface shape of the curved surface to be measured based on the geometric relationship and the second phase information comprises the following steps:
determining a second height map of the curved surface to be measured after the region reconstruction is executed based on the first height map contained in the second phase information;
based on the geometric relationship, the second height map is brought into a straight line where the incident ray is located to obtain a first coordinate set and a second coordinate set, and a target point set is formed based on the second height map, the first coordinate set and the second coordinate set;
constructing a predicted surface shape of the curved surface to be measured based on the target point set; repeatedly executing the step of constructing the predicted surface shape of the curved surface to be detected to obtain the nth predicted surface shape, and determining the nth predicted surface shape as the surface shape of the curved surface to be detected under the condition that the difference value between the nth predicted surface shape and the (n-1) th predicted surface shape is smaller than a preset surface shape threshold value; wherein n is a positive integer.
According to the small coincidence field multi-view phase deflection measurement method provided by the application, the algorithm for acquiring the second phase information comprises the following steps: a temporal phase unwrapping algorithm, a spatial phase unwrapping algorithm, a fourier phase unwrapping algorithm, and/or a least squares phase unwrapping algorithm.
According to the small coincidence view field multi-view phase deflection measuring device and method, a phase object and an imaging system in the small coincidence view field multi-view phase deflection measuring device are respectively connected with a control computer through data links; projecting first phase information by using the phase object, and acquiring second phase information displayed by the phase object by using an imaging system; and calibrating the geometric relationship between the phase object and the imaging system by using the control computer, controlling the phase object and the imaging system to operate to obtain second phase information, and generating the surface shape of the curved surface to be detected in the phase object based on the geometric relationship and the second phase information. The application provides a little coincidence field of vision many meshes phase place deflection measuring device can be in need not with the help of the priori knowledge of design shape of face and under the unknown condition of the curved surface design shape of awaiting measuring, can carry out the independent measurement or the full field of vision measurement to unknown curved surface respectively with the help of many meshes imaging system coincidence field of vision and many meshes imaging system field of vision.
Drawings
In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a small coincidence field multi-view phase deflection measuring apparatus provided in an embodiment of the present application;
fig. 2 is a schematic flowchart of a small coincidence field multi-view phase deviation measurement method according to an embodiment of the present application;
fig. 3 is a schematic view of a working scenario of the small coincidence field multi-view phase deflection measuring apparatus provided in the embodiment of the present application;
FIG. 4 is a schematic diagram illustrating a region reconstruction performed according to an embodiment of the present disclosure;
fig. 5 is a schematic diagram of a result of the reconstruction convergence of the curved surface region to be measured according to the embodiment of the present application;
fig. 6 is a schematic diagram of an error measurement result provided in an embodiment of the present application.
Reference numerals are as follows:
1: a first camera; 2: a second camera; 3: an FA lens;
4: a telecentric lens; 5: a liquid crystal display; 6: a control computer;
7: and (5) a curved surface to be measured.
Detailed Description
To make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below with reference to the drawings in the present application, and it is obvious that the described embodiments are some, but not all embodiments of the present application. 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 application.
The figures are purely diagrammatic and not drawn to scale. As used herein, the term "preferred," and similar terms, are used as table approximations and not as table degrees, and are intended to account for inherent deviations in measured or calculated values that will be recognized by those of ordinary skill in the art. It should be noted that in the present description the expressions "first", "second", "third", etc. are only used to distinguish one feature from another, and do not represent any limitation of the features, in particular any precedence.
It will be further understood that terms such as "comprising," "including," and/or "containing," when used in this specification, are open-ended and not closed-ended, and specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to examples or illustrations.
Unless otherwise defined, all terms (including engineering and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In order to solve the problems in the prior art, embodiments of the present application provide a small coincidence field multi-view phase deflection measurement apparatus and method.
Fig. 1 is a schematic structural diagram of a small coincidence field of view multi-eye phase deviation measuring device according to an embodiment of the present application. Fig. 1 shows a small coincidence field of view multi-ocular phase deflection measurement device 100, a phase object 110, an imaging system 120, and a control computer 130.
In fig. 1, specifically, the small coincidence field multi-view phase deviation measuring apparatus 100 includes: a phase object 110, an imaging system 120, and a control computer 130.
The phase object 110 and the imaging system 120 are each connected to a control computer 130 via a data link.
A phase object 110 for projecting first phase information. An imaging system 120 for acquiring second phase information of the phase object display. And the control computer 130 is configured to calibrate a geometric relationship between the phase object 110 and the imaging system 120, control the phase object 110 and the imaging system 120 to operate, obtain second phase information, and generate a surface shape of a curved surface to be measured in the phase object 110 based on the geometric relationship and the second phase information.
Based on the above embodiments, the small coincidence field multi-view phase deflection measuring device provided by the application can perform independent measurement or full view field measurement on an unknown curved surface respectively by means of the coincidence field of the multi-view imaging system and the field of view of the multi-view imaging system without the need of prior knowledge of the designed surface shape and under the condition that the designed surface shape of the curved surface to be measured is unknown.
Further, the number of phase objects 110 is not less than one. Meanwhile, the phase object 110 includes: a planar phase object and/or a curved phase object with a curved surface. And, the first phase information projected by the phase object 110 includes: visible light information, infrared light information, and/or ultraviolet light information.
In addition, the number of the imaging systems 120 is not less than two, and the fields of view of the imaging systems 120 are overlapped. Meanwhile, the imaging system 120 includes: a non-telecentric imaging system and/or a telecentric imaging system.
It should be noted that the fact that there is a field of view coincidence between the imaging systems 120 means that it is necessary to ensure that there is a field of view coincidence between at least two imaging systems during the process of installing the imaging systems 120.
To sum up, the small coincidence view field multi-eye phase deflection measuring device provided by the application has the following remarkable characteristics:
firstly, the surface shape is not designed based on the curved surface to be measured, the prior knowledge of the designed surface shape of the curved surface to be measured is not needed, and the curved surface with unknown surface shape can be measured or reversely measured.
And secondly, full-field measurement can be performed by using the imaging systems, and the full-field measurement result of each imaging system can still be obtained only under the condition that a plurality of imaging systems have partially overlapped fields of view, so that the waste of the measurement range of the imaging systems is avoided, and a larger surface shape measurement caliber is provided.
Finally, the small coincidence field multi-view phase deflection measuring device has novelty, feasibility, usability and universality.
Fig. 2 is a schematic flow chart of a small coincidence field multi-view phase deviation measurement method according to an embodiment of the present application. The small coincidence field multi-view phase deflection measuring method is used for the small coincidence field multi-view phase deflection measuring device in any one of the embodiments. As shown in fig. 2, the method includes:
Specifically, the geometric relationship refers to the stereoscopic position coordinates at which the phase object and the imaging system are respectively located and the positional relationship therebetween.
Correspondingly, before the geometric relationship between the phase object and the imaging system is calibrated, at least two, namely two or more imaging systems and the phase object are respectively connected with the control computer, partial view field coincidence between the imaging systems is ensured in the installation process, and the coincidence view field area can be small.
Specifically, if the number of phase objects is one, the first phase information may be any one of visible light information, infrared light information, or ultraviolet light information. If the number of the phase objects is more than one, the first phase information may be any one or more of visible light information, infrared light information, or ultraviolet light information.
Correspondingly, the second phase information refers to the collection of various types of information displayed by the phase object.
And 203, acquiring second phase information, and generating the surface shape of the curved surface to be measured in the phase object based on the geometric relationship and the second phase information.
Specifically, the surface shape representation of the curved surface to be measured in the phase object is a measurement result obtained by performing multi-view phase deflection measurement on the curved surface to be measured.
Based on the above embodiments, the small coincidence field multi-view phase deflection measurement method provided by the application can perform independent measurement or full view field measurement on an unknown curved surface respectively by means of the coincidence field of the multi-view imaging system and the field of view of the multi-view imaging system without the need of prior knowledge of a designed surface shape and under the condition that the designed surface shape of the curved surface to be measured is unknown.
Further, before controlling the imaging system to acquire the second phase information of the phase object display, the method further comprises the following steps:
the method comprises the steps of S1, defining pixel coordinates of a first pixel point in an imaging system, obtaining a plurality of target points on the curved surface to be detected based on the pixel coordinates, and constructing a basic point set based on the target points.
Exemplarily, pixel coordinates (U, v) of a first pixel point existing in any imaging system are defined, and the pixel coordinates (U, v) form a pixel coordinate set U in a coincidence view field region formed by at least two imaging systems, as shown in formula (1):
U＝{ui,vi} (1)
wherein i =1,2,3, \8230, N.
Based on pixel coordinates (U, v), a pixel coordinate set U is formed, a plurality of target points on the curved surface to be detected are obtained through consistency of normal vectors of the curved surface to be detected under a multi-view imaging system, and a basic point set Z is constructed according to the obtained target points, wherein the basic point set Z is as shown in a formula (2):
Z＝{Xi(ui,vi),Yi(ui,vi),Zi(ui,vi)} (2)
wherein i =1,2,3, \8230, N.
And S2, selecting a second pixel point in the basic point set, determining the second pixel point as an anchor point, determining an initial solution of the curved surface to be detected based on the anchor point, and acquiring the corresponding relation of the first pixel point to the pixel position point based on the first phase information and the initial solution.
Illustratively, the pixel coordinates (u) in the set of base points Z are determined A ,v A ) Corresponding point Z A Is the second pixel point, and the point Z is A As anchor points, with over-anchor points Z in any imaging system A The plane of the curve is the initial solution S of the curved surface to be measured 0 . Using first phase information projected by phase object and initial solution S 0 Obtaining a first pixel point x i (u, v) corresponds to the screen pel position point M i (u, v) corresponding relationship between them.
S3, determining an intersection point of the incident light corresponding to the first pixel point and the initial solution, and determining a pixel position point corresponding to the first pixel point based on the corresponding relation; and performing region reconstruction based on the first pixel point, the intersection point and the pixel position point to generate a first height map.
Specifically, the first height map refers to the updated relative height map.
Illustratively, a first pixel point x is determined i (u, v) corresponding incident light and initial solution S of curved surface to be measured 0 Has a cross point of P 0i Point of intersection P 0i As shown in formula (3):
P 0i (u,v) ＝ (X 0 (u,v),Y 0 (u,v),Z 0 (u,v)) (3)
wherein i =1,2,3, \8230, N.
Determining a first pixel point x of the imaging system based on the corresponding relation i (u, v) corresponding screen pixel location point M i (u, v). Using point of intersection P 0i And the position point M of the picture element of the screen i (u, v) and the intersection point P 0i And the first pixel point x i (u, V) normal vector V of curved surface formed by bisector of angle between connecting lines 0 (u, v) set, and performing region reconstruction to obtain an updated relative height map H 1 (u,v)。
Note that the problem of the default size of 1 in the region reconstruction using the normal vector of the curved surface means that X is a maximum 0 (u,v),Y 0 (u, V) and vector V 0i (u, v) can sufficiently restore the curved surface shape, howeverAs a result, there are 1 degree of freedom in the height direction z.
And S4, forming second phase information based on the first height map.
Based on the above embodiment, the algorithm for acquiring the second phase information includes: a temporal phase unwrapping algorithm, a spatial phase unwrapping algorithm, a fourier phase unwrapping algorithm, and/or a least-squares phase unwrapping algorithm.
Further, generating the surface shape of the curved surface to be measured based on the geometric relationship and the second phase information, specifically comprising:
and S1, determining a second height map of the curved surface to be measured after the regional reconstruction is executed based on the first height map contained in the second phase information.
Specifically, the second height map is an absolute height map after the region reconstruction.
Illustratively, according to the relative height map H 1 (u, v) translation in height direction z by a distance T 1 Let the pixel coordinate (u) A ,v A ) Corresponding anchor point Z A As shown in formula (4):
Z A ＝H 1 (u A ,v A )+T 1 (4)
wherein H 1 (u, v) is a relative height map, T 1 Is a relative height diagram H 1 (u, v) the distance of the translation in the height direction z.
Further, according to the anchor point Z A Can obtain an absolute height map Z after regional reconstruction 1 (u, v) is represented by the formula (5).
Z 1 (u,v) ＝H 1 (u,v)+T 1 (5)
And S2, based on the geometric relation, bringing the second height map into a straight line where the incident ray is located to obtain a first coordinate set and a second coordinate set, and forming a target point set based on the second height map, the first coordinate set and the second coordinate set.
Illustratively, the absolute height map Z is generated based on the calibration results of the imaging system contained in the obtained geometric relationship 1 (u, v) into the straight line of the incident ray corresponding to the pixel coordinate (u, v)Obtaining a first coordinate set X 1 (u, v) and a second set of coordinates Y 1 (u, v); note that the first coordinate set X 1 (u, v) and a second set of coordinates Y 1 (u, v) are updated values. From absolute height map Z 1 (u, v), first set of coordinates X 1 (u, v) and a second set of coordinates Y 1 (u, v), forming a set of target points P 1 (u, v) is represented by the formula (6).
P 1 (u,v)＝{X 1 (u,v),Y 1 (u,v),Z 1 (u,v)} (6)
S3, constructing a predicted surface shape of the curved surface to be measured based on the target point set; repeatedly executing the step of constructing the predicted surface shape of the curved surface to be measured to obtain the nth predicted surface shape, and determining the nth predicted surface shape as the surface shape of the curved surface to be measured under the condition that the difference value between the nth predicted surface shape and the (n-1) th predicted surface shape is smaller than a preset surface shape threshold value; wherein n is a positive integer.
Illustratively, the set of target points P may be based on 1 (u, v), constructing the predicted surface shape S of the curved surface to be measured 1 . Proceed to predict the profile S 1 As the initial solution of the curved surface to be measured, repeating the execution for n times to construct the predicted surface shape S of the curved surface to be measured 1 To obtain the predicted surface shape S of the nth curved surface to be measured n Determining that the difference value between the nth predicted surface shape and the (n-1) th predicted surface shape is smaller than a preset surface shape threshold value, namely, determining that the adjacent two iteration results S n -S n-1 Less than a preset surface shape threshold value delta S 1 Or the iteration number n reaches a set threshold value n threshold Stopping iteration and determining the nth predicted surface shape S n Is the surface shape of the curved surface to be measured. Wherein n is a positive integer.
In summary, the small coincidence view field multi-view phase deflection measurement method provided by the application has the characteristic of rapid updating of the surface shape of the curved surface. In the iterative process of the curved surface reconstruction, the x, y and z coordinates of the curved surface are updated without using the triangulation algorithm to perform intersection with a line surface. The area reconstruction and the anchor point are firstly used for obtaining a z coordinate, and the z coordinate is substituted to obtain corresponding x and y according to a linear equation where the incident ray corresponding to the pixel obtained from the imaging system calibration result is located, so that the surface shape of the curved surface is updated.
Preferably, the anchor point Z is reduced in order to improve the accuracy and robustness of the system A Self-calculated error pair for reconstructing curved surface shape S n Based on the above embodiments, the small coincidence field multi-view phase deviation measurement method provided by the present application may be further optimized.
Exemplarily, the base point set Z = { X =setof base points described in the above embodiment may be used i ,Y i ,Z i Using it as anchor point set, let the relative height map H n (u, v) distance T of translation in height direction z n+1 As shown in formula (7):
T n+1 ＝(Z i (u i ,v i )-H n (u i ,v i ))/N (7)
then according to T shown in formula (7) n+1 An updated absolute height map can be obtained as shown in equation (8):
Z n+1 (u,v)＝H n (u,v)+T n+1 (8)
based on the calibration result of the imaging system, the height Z is determined n+1 (u, v) substituting the incident ray into the straight line corresponding to the pixel (u, v) to obtain the updated first coordinate set X n+1 (u, v) and a second set of coordinates Y n+1 (u, v). Further, the target point set P is expressed by the formula (9) n+1 (u, v), the surface shape S of the reconstructed curved surface to be measured can be determined n+1 。
P n+1 (u,v)＝{X 1 (u,v),Y 1 (u,v),Z 1 (u,v)} (9)
Further, based on the above embodiment, the relative height map H is acquired n+2 (u, v) translation distance T in height direction Z n+2 As shown in equation (10):
T n+2 ＝(Z i (u i ,v i )-H n+2 (u i ,v i ))/N (10)
combining the formula (10) to obtain an absolute height chart Z of the reconstructed curved surface to be measured n+2 (u, v) is represented by formula (11):
Z n+2 (u,v)＝H n+2 (u,v)+T n+2 (11)
based on the calibration result of the imaging system, the height Z is determined n+2 (u, v) are substituted into the straight line where the incident ray corresponding to the pixel coordinate (u, v) is located to obtain the updated first coordinate set X n+2 (u, v) and a second set of coordinates Y n+2 (u, v). Further, according to the target point set P as shown in the formula (12) n+2 (u, v), the surface shape S of the reconstructed curved surface to be measured can be determined n+2 。
P n+2 (u,v)＝{X n+2 (u,v),Y n+2 (u,v),Z n+2 (u,v)} (12)
Proceed to predict the profile S n+2 As the initial solution of the curved surface to be measured, repeating the step of constructing the predicted surface shape of the curved surface to be measured for n times to obtain the predicted surface shape S of the (m + 1) th curved surface to be measured m+1 Determining that the difference value between the m +1 th predicted surface shape and the m th predicted surface shape is smaller than a preset surface shape threshold value, namely, determining that the difference value between the m +1 th predicted surface shape and the m th predicted surface shape is smaller than the preset surface shape threshold value in the adjacent two iteration results S m+1 -S m Less than a preset surface shape threshold value Delta S 2 Or the number of iterations m reaches a set threshold value m threshold Stopping iteration, and determining the m +1 th predicted surface shape S m+1 The surface shape S of the curved surface to be measured under the field of view of the imaging system is finally obtained m+1 . Wherein n is a positive integer.
It should be further noted that, based on the above embodiments, the surface shape of the curved surface to be measured in the fields of view of the multiple imaging systems can be obtained.
Preferably, based on the above embodiments, the working scenario of the small coincidence field multi-view phase deviation measurement apparatus provided by the present application may be described with reference to a specific application example.
Based on the above embodiments, fig. 3 is a schematic view of a working scenario of a small coincidence field multi-view phase deviation measurement apparatus provided according to an embodiment of the present application. Fig. 3 shows a first camera 1, a second camera 2, an FA lens 3, a telecentric lens 4, a liquid crystal display 5, a control computer 6 and a curved surface to be measured 7. The curved surface 7 to be measured is a curved surface to be measured in the phase object.
Correspondingly, the focal length of the FA lens 3 is 8mm, the magnification of the telecentric lens 4 is 0.061, and the control computer 6 comprises a 24-inch white light plane liquid crystal display 5; meanwhile, the FA lens 3 and the telecentric lens 4 are respectively fastened on the first camera 1 and the second camera 2 through standard C interfaces. After the equipment is calibrated, phase-shifted sine stripes are projected on the liquid crystal display 5, the first camera 1 and the second camera 2 are further controlled, phase information of the sine stripes projected by the liquid crystal display 5 is acquired, and the stripe phase information modulated by reflection of the curved surface 7 to be measured is acquired, and finally the surface shape of the curved surface 7 to be measured is calculated.
Specifically, the first camera 1 and the FA lens 3 constitute a first imaging system, and the second camera 2 and the telecentric lens 4 constitute a second imaging system. During the process of installing the first imaging system and the second imaging system, the first imaging system and the second imaging system need to ensure that partial fields of view are overlapped. And calibrating the internal reference of the first imaging system, the internal reference of the second imaging system and the geometric relationship among the first imaging system, the second imaging system and the phase object by using a three-coordinate measuring machine and a point light source microscope. By combining a preset absolute phase information acquisition method, the corresponding relation between the target surface pixels of the first imaging system and the second imaging system 2 and the pixels of the liquid crystal display 5 can be obtained.
It should be noted that the predetermined absolute phase information obtaining method includes, but is not limited to, a time phase unwrapping algorithm.
Further, pixel coordinates (u, v) in the first imaging system are defined, and the pixel coordinates (u, v) form a location set in the region of the coincidence field of view as shown in equation (13):
U＝{u i ,v i } (13)
wherein i =1,2,3, \8230;, N.
According to the geometric relationship among the first imaging system, the second imaging system and the phase object, determining a pixel position point x corresponding to pixel coordinates (u, v) in a known coincidence view field region according to the obtained calibration result 1 Pixel location point x 1 Corresponding ray and pixel location point x 1 Corresponding screen point M 1 Searching for different heights P on the ray i ,P i+1 ,P i+2 ........ According to the calibration result corresponding to the second imaging system, different pixel position points x corresponding to the second imaging system under different heights are obtained 2i ,x 2i+1 ,x 2i+2 A.. Once. 2i Corresponding screen point M 2i Pixel x 2i+1 Corresponding screen point M 2i+1 Pixel x 2i+2 Corresponding screen point M 2i+2 ...... In summary, at the height P i And P i+2 At the position, the normal vector of the curved surface calculated based on the first imaging system is inconsistent with the normal vector of the curved surface calculated based on the second imaging system; thus, P i And P i+2 Not pixel location point x 1 The height of the corresponding curved surface 7 to be measured. At a height P i+1 At the position, the normal vector of the curved surface calculated based on the first imaging system is consistent with the normal vector of the curved surface calculated based on the second imaging system, namely the height P i+1 Is a pixel location point x 1 The height of the corresponding curved surface 7 to be measured. Definition P i As shown in formula (14):
P i ＝X i (u i ,v i ),Y i (u i ,v i ),Z i (u i ,v i ) (14)
and, according to definition P i A point set Z may be constructed. Correspondingly, point set Z is as shown in equation (15):
Z＝{X i (u i ,v i ),Y i (u i ,v i ),Z i (u i ,v i )} (15)
wherein i =1,2,3, \8230, N.
Further, the pixel coordinate (u) in the point set Z is selected A ,v A ) Corresponding point Z A As an anchor point, with the pupil center of the first imaging system and the anchor point Z A The entire system is rotated until the line is parallel to the z-axis, using the line of (a) as a reference.
It should be noted that the above steps are performed to ensure robustness of subsequent surface reconstruction and avoid the occurrence of a condition that a point set in the surface reconstruction is not monotonous in the x direction or the y direction.
Correspondingly, the adjusted results are shown in fig. 4. Fig. 4 is a schematic diagram of a region reconstruction provided according to an embodiment of the present application.
In particular, as shown in connection with fig. 4, with an over-anchor point Z in the first imaging system A The plane is the initial solution S of the curved surface to be measured 0 . Obtaining a pixel x in a first imaging system using absolute phase information i (u, v) and its corresponding picture element position point M in the liquid crystal display 5 i (u, v) corresponding relationship between them.
Still further, using the pixel location point x of the first imaging system i (u, v) x as shown in formula (16) i (u, v) corresponding incident ray and plane initial solution S 0 Intersection point P 0i (u, v), imaging system pixel x i (u, v) corresponding to the screen picture element position point M i (u, v) using the intersection P 0i And the position point M of the picture element of the screen i (u, v) line P 0i (u,v)-M i (u, v), and intersection point P 0i And the first pixel point x i (u, v) line P 0i (u,v)-x i Normal vector V of curved surface formed by angular bisector between (u, V) 0 (u, v) set, and performing region reconstruction to obtain an updated relative height map H 1 (u,v)。
P 0i (u,v) ＝ (X 0 (u,v),Y 0 (u,v),Z 0 (u,v)) (16)
Note that the problem of the default size of 1 in the region reconstruction from the normal vector of the surface is that X means 0 (u,v)，Y 0 (u, V) and vector V 0i (u, v) can sufficiently restore the curved surface shape, but as a result, there is 1 degree of freedom in the height direction z.
Further, let the relative height chart H 1 (u, v) translation in height direction z by a distance T 1 Let the pixel coordinate (u) A ,v A ) Corresponding anchor point Z A As shown in equation (17):
Z A ＝H 1 (u A ,v A )+T 1 (17)
the absolute height of the reconstructed curved surface can be obtained from the equation (17)Drawing Z 1 (u, v) is represented by formula (18):
Z 1 (u,v) ＝H 1 (u,v)+T 1 (18)
from the calibration result of the imaging system included in the obtained geometric relationship, an absolute height map Z shown by equation (18) is obtained 1 (u, v) is substituted into the straight line where the incident ray corresponding to the pixel coordinate (u, v) is located to obtain a first coordinate set X 1 (u, v) and a second set of coordinates Y 1 (u, v); note that the first coordinate set X 1 (u, v) and a second set of coordinates Y 1 (u, v) are updated values. From absolute height map Z 1 (u, v), first set of coordinates X 1 (u, v) and a second set of coordinates Y 1 (u, v), forming a set of target points P 1 (u, v) is represented by the formula (19).
P 1 (u,v)＝{X 1 (u,v),Y 1 (u,v),Z 1 (u,v)} (19)
Can be based on the target point set P 1 (u, v), constructing the predicted surface shape S of the curved surface to be measured 1 。
Still further, proceed to predict the profile S 1 As the initial solution of the curved surface to be measured, repeating the execution for n times to construct the predicted surface shape S of the curved surface to be measured 1 To obtain the predicted surface shape S of the nth curved surface to be measured n Determining that the difference value between the nth predicted surface shape and the (n-1) th predicted surface shape is smaller than a preset surface shape threshold value, namely the adjacent two iteration results S n -S n-1 Less than a preset surface shape threshold value Delta S 1 Or the iteration number n reaches a set threshold value n threshold Stopping iteration and determining the nth predicted surface shape S n Is the surface shape of the curved surface to be measured. Wherein n is a positive integer.
Preferably, based on the above embodiment, in order to improve the accuracy and robustness of the system, the anchor point Z is reduced A Self-calculated error pair to reconstruct curved surface S n The base point set Z = { X described in the above embodiments i ,Y i ,Z i Using it as anchor point set, let the relative height map H n (u, v) distance T of translation in height direction z n+1 As shown in equation (20):
T n+1 ＝(Z i (u i ,v i )-H n (u i ,v i ))/N (20)
then according to T shown in formula (20) n+1 An updated absolute height map can be obtained as shown in equation (21):
Z n+1 (u,v)＝H n (u,v)+T n+1 (21)
based on the calibration result of the imaging system, the height Z is determined n+1 (u, v) substituting the incident ray into the straight line corresponding to the pixel (u, v) to obtain the updated first coordinate set X n+1 (u, v) and a second set of coordinates Y n+1 (u, v). Further, the target point set P is expressed by the equation (22) n+1 (u, v), the surface shape S of the reconstructed curved surface to be measured can be determined n+1 。
P n+1 (u,v)＝{X 1 (u,v),Y 1 (u,v),Z 1 (u,v)} (22)
Further, based on the above embodiment, the relative height map H is acquired n+2 (u, v) translation distance T in height direction Z n+2 As shown in equation (23):
T n+2 ＝(Z i (u i ,v i )-H n+2 (u i ,v i ))/N (23)
combining formula (23) to obtain an absolute height chart Z of the reconstructed curved surface to be measured n+2 (u, v) is represented by formula (24):
Z n+2 (u,v)＝H n+2 (u,v)+T n+2 (24)
based on the calibration result of the imaging system, the height Z is determined n+2 (u, v) substituting the straight line where the incident ray corresponding to the pixel coordinate (u, v) is located to obtain an updated first coordinate set X n+2 (u, v) and a second set of coordinates Y n+2 (u, v). Further, according to the target point set P as shown in formula (25) n+2 (u, v), the surface shape S of the reconstructed curved surface to be measured can be determined n+2 。
P n+2 (u,v)＝{X n+2 (u,v),Y n+2 (u,v),Z n+2 (u,v)} (25)
Proceed to predict the profile S n+2 As the initial solution of the curved surface to be measured, repeating the step of constructing the predicted surface shape of the curved surface to be measured for n times to obtain the predicted surface shape S of the (m + 1) th curved surface to be measured m+1 Determining that the difference value between the m +1 th predicted surface shape and the m th predicted surface shape is smaller than a preset surface shape threshold value, namely, determining that the difference value between the m +1 th predicted surface shape and the m th predicted surface shape is smaller than the preset surface shape threshold value in the adjacent two iteration results S m+1 -S m Less than a preset surface shape threshold value Delta S 2 Or the number of iterations m reaches a set threshold value m threshold Stopping iteration, and determining the m +1 th predicted surface shape S m+1 The surface shape S of the curved surface to be measured under the field of view of the imaging system is finally obtained m+1 . Wherein n is a positive integer.
Wherein, the convergence result of the iterative process of the curved surface region to be measured is shown in fig. 5. Fig. 5 is a schematic diagram of a result of the reconstruction convergence of the curved surface region to be measured according to an embodiment of the present application.
It should be further noted that, errors corresponding to the measured surface shapes obtained by the curved surface to be measured in the large field of view corresponding to the first imaging system and the small field of view corresponding to the second imaging system are shown in fig. 6. FIG. 6 is a graphical illustration of error measurements provided by an embodiment of the present application.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (3)
1. A small coincidence field multi-eye phase deflection measurement method is characterized by comprising the following steps:
calibrating the geometric relationship between the phase object and the imaging system;
controlling the phase object to project first phase information, and controlling the imaging system to acquire second phase information displayed by the phase object;
acquiring the second phase information, and generating the surface shape of the curved surface to be measured in the phase object based on the geometric relationship and the second phase information;
before the controlling the imaging system to acquire the second phase information displayed by the phase object, the method comprises the following steps:
defining pixel coordinates of a first pixel point in the imaging system, acquiring a plurality of target points on the curved surface to be detected based on the pixel coordinates, and constructing a basic point set based on the target points;
selecting a second pixel point in the basic point set, determining the second pixel point as an anchor point, determining an initial solution of the curved surface to be detected based on the anchor point, and acquiring a corresponding relation of the first pixel point to a pixel position point based on the first phase information and the initial solution;
determining an intersection point of the incident light corresponding to the first pixel point and the initial solution, and determining the pixel position point corresponding to the first pixel point based on the corresponding relation; performing region reconstruction based on the first pixel point, the intersection point and the pixel position point to generate a first height map;
forming the second phase information based on the first height map;
the device for implementing the method comprises: a phase object, an imaging system and a control computer;
the phase object and the imaging system are respectively connected with the control computer through a data link;
the phase object is used for projecting first phase information;
the imaging system is used for acquiring the second phase information displayed by the phase object;
the control computer is used for calibrating the geometric relationship between the phase object and the imaging system, controlling the phase object and the imaging system to operate, acquiring the second phase information, and generating the surface shape of the curved surface to be measured in the phase object based on the geometric relationship and the second phase information;
the number of the phase objects is not less than one;
the phase object includes: a planar phase object and/or a curved phase object with a surface shape;
the first phase information projected by the phase object includes: visible light information, infrared light information, and/or ultraviolet light information;
the number of the imaging systems is not less than two, and the imaging systems have field of view coincidence;
the imaging system includes: a non-telecentric imaging system and/or a telecentric imaging system.
2. The small coincidence field of view multi-purpose phase deflection measurement method according to claim 1, wherein the generating the surface shape of the curved surface to be measured based on the geometric relationship and the second phase information includes:
determining a second height map of the curved surface to be detected after region reconstruction is performed based on the first height map contained in the second phase information;
based on the geometric relationship, the second height map is brought into a straight line where the incident ray is located to obtain a first coordinate set and a second coordinate set, and a target point set is formed based on the second height map, the first coordinate set and the second coordinate set;
constructing a predicted surface shape of the curved surface to be measured based on the target point set; repeatedly executing the step of constructing the predicted surface shape of the curved surface to be detected to obtain the nth predicted surface shape, and determining the nth predicted surface shape as the surface shape of the curved surface to be detected under the condition that the difference value between the nth predicted surface shape and the (n-1) th predicted surface shape is smaller than a preset surface shape threshold value; wherein n is a positive integer.
3. The small coincidence field of view multi-objective phase deflection measurement method according to claim 1, wherein the algorithm for obtaining the second phase information comprises: a temporal phase unwrapping algorithm, a spatial phase unwrapping algorithm, a fourier phase unwrapping algorithm, and/or a least squares phase unwrapping algorithm.
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