CN116379959A - Method and system for measuring three-dimensional surface shape of mirror surface - Google Patents

Method and system for measuring three-dimensional surface shape of mirror surface Download PDF

Info

Publication number
CN116379959A
CN116379959A CN202310395978.1A CN202310395978A CN116379959A CN 116379959 A CN116379959 A CN 116379959A CN 202310395978 A CN202310395978 A CN 202310395978A CN 116379959 A CN116379959 A CN 116379959A
Authority
CN
China
Prior art keywords
mirror
surface shape
color
camera
measured
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202310395978.1A
Other languages
Chinese (zh)
Inventor
郝群
胡摇
王子琛
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beijing Institute of Technology BIT
Original Assignee
Beijing Institute of Technology BIT
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beijing Institute of Technology BIT filed Critical Beijing Institute of Technology BIT
Priority to CN202310395978.1A priority Critical patent/CN116379959A/en
Publication of CN116379959A publication Critical patent/CN116379959A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/50—Depth or shape recovery
    • G06T7/521—Depth or shape recovery from laser ranging, e.g. using interferometry; from the projection of structured light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/60—Analysis of geometric attributes
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10024—Color image
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/30—Subject of image; Context of image processing
    • G06T2207/30108—Industrial image inspection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/30—Subject of image; Context of image processing
    • G06T2207/30108—Industrial image inspection
    • G06T2207/30156—Vehicle coating

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Theoretical Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Geometry (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The method and the system for measuring the three-dimensional surface shape of the mirror surface can realize nondestructive, in-place and transient three-dimensional surface shape measurement of the mirror surface, have few used devices, improve the measuring speed and reduce the requirement on the measuring environment. The method comprises the following steps: (1) performing system calibration; (2) constructing a color speckle pattern; (3) Displaying the color speckle pattern on an LCD screen, and separating channels to obtain speckles of red, green and blue channels respectively; (4) Respectively matching images of a red channel and a green channel and images of a red channel and a blue channel to obtain the displacement field sizes of each pixel along an x axis and a y axis in a speckle pattern; (5) Calculating the position of each point corresponding to the sampling point on the measured mirror according to the calibration relation; (6) obtaining the rough surface shape of the detected mirror through gradient integration; (7) The rough surface shape is taken as the surface shape of the mirror to be measured, the gradient of each point on the mirror surface of the mirror to be measured along the x direction and the y direction is recalculated, and the mirror surface shape to be measured is obtained through gradient integration; and (8) repeating the step (7) for iteration.

Description

Method and system for measuring three-dimensional surface shape of mirror surface
Technical Field
The invention relates to the technical field of photoelectric detection, in particular to a method for measuring the three-dimensional surface shape of a mirror surface, and also relates to a system for measuring the three-dimensional surface shape of the mirror surface, which can carry out nondestructive transient measurement on the three-dimensional surface shape of the mirror surface with a small curvature radius and can also be used for in-situ measurement in the processing process.
Background
With the development of materials and processing technology, shapes with smaller curvature radius are increasingly used in the aspects of mirror design, automobile appearance and the like. With the development of automobile sheet metal technology, the shape of the outer surface of the automobile is not a plane and a simple curved surface, more and more complicated sheet metal models are used in the appearance design of the automobile, wherein the curved surface with a small curvature radius is a majority, the automobile paint is a bright surface, the influence of tiny scratches on the appearance is large, and the space reserved for a measuring system is small due to the fact that the environment of a paint spraying workshop is complex, larger vibration and oil mist are generated in the processing process, and the workpiece is measured quickly and on a processing station. Therefore, the requirements of small curvature radius measurement, nondestructive measurement, transient measurement and in-situ measurement are put forward on the measurement of the three-dimensional surface shape.
Currently, the commonly used three-dimensional shape detection technology of high-reflection objects is mainly divided into a contact type and a non-contact type. The contact measurement is carried out by adopting a probe as the traditional three-coordinate measuring machine and the profilometer, so that the tiny and soft thin measured object is easy to deform, scratch and even damage the measured object, and nondestructive measurement cannot be realized; in non-contact measurement, the measurement accuracy of the interferometry is highest, but the interferometry is relatively large in size, relatively high in cost, relatively sensitive to vibration and air disturbance, and inconvenient to arrange on a processing machine for in-situ measurement. The traditional deflection technique uses sine stripes as structured light, and supposing that 2×n pictures are required to be taken by using an N-step phase shift rule, the measurement duration is prolonged, and the transient measurement capability is not provided.
Disclosure of Invention
In order to overcome the defects of the prior art, the technical problem to be solved by the invention is to provide a method for measuring the three-dimensional surface shape of the mirror surface, which can realize nondestructive, in-place and transient three-dimensional surface shape measurement of the mirror surface, has few devices, improves the measuring speed and reduces the requirement on the measuring environment.
The technical scheme of the invention is as follows: the method for measuring the three-dimensional surface shape of the mirror surface comprises the following steps:
(1) Performing system calibration, calibrating internal parameters and external parameters of a camera, and constructing a 3D-LUT (3D-Look-Up-Table) for color crosstalk correction;
(2) Constructing a color speckle pattern, randomly generating a binary speckle pattern, and along the x-axis and y-axis
The axes are respectively translated by n pixels to obtain an original speckle pattern, a speckle pattern moving along the x axis and a speckle pattern moving along the y axis;
(3) Displaying the color speckle pattern on an LCD screen, collecting speckle patterns reflected by a tested mirror by using a color camera, eliminating the influence of color crosstalk and color unbalance, and respectively obtaining speckle of red, green and blue channels through channel separation;
(4) Respectively carrying out digital image Correlation matching based on ZNCC (Zero Mean Normalized Cross-Correlation, zero mean normalized cross Correlation) on images of a red channel, a green channel, a red channel and a blue channel to obtain displacement field sizes of pixels in a speckle pattern along an x axis and a y axis;
(5) Calculating the coordinates of each point on the LCD screen, which is separated by n times the pixel width of the screen, corresponding to the CCD of the camera according to the displacement field, and calculating the position of each point corresponding to the sampling point on the measured mirror according to the calibration relation;
(6) Firstly, assuming that a measured mirror is a plane mirror, calculating gradients along the x direction and the y direction at each sampling point on the mirror surface of the measured mirror according to a calibrated geometric relationship and a formula derived by an optical reflection law, and obtaining a rough surface shape of the measured mirror through gradient integration;
(7) The obtained surface shape is taken as the surface shape of the mirror to be measured, the gradients of each point on the mirror to be measured along the x direction and the y direction are recalculated according to the formula in the step (6), and the mirror surface shape to be measured is obtained through gradient integration;
(8) And (3) repeating the step (7) for iteration, and stopping iteration when the difference between the surface shapes obtained by the previous gradient integration and the next gradient integration is smaller than a certain threshold value, wherein the finally obtained surface shape of the measured mirror is the required surface shape of the measured mirror.
According to the invention, three color channels of the display are used for respectively displaying a speckle pattern, and the mirror surface shape is calculated in an iterative optimization mode, compared with the traditional stripe deflection operation, only one picture is required to be acquired, so that the measurement speed is greatly improved, the system has transient measurement capability, meanwhile, the problem that the error of measuring the small curvature radius surface shape is large in the traditional measurement principle is solved, nondestructive, in-place and transient measurement can be realized on the small curvature radius mirror surface, the number of used devices is small, the measurement speed is improved, and the requirement on the measurement environment is reduced.
There is also provided a system for specular three-dimensional surface shape measurement, comprising: the device comprises a detected mirror surface (1), a flat beam splitter (2), a COMS camera (3), an industrial lens (4), a computer (5) and an LCD color display screen (6);
the LCD color display screen is connected with the computer, the computer controls and displays the color speckle patterns, the LCD color display screen and the detected mirror surface are placed face to face, a flat beam splitter is placed on the middle inclined side of the LCD color display screen and the detected mirror surface by 45 degrees, the beam splitter reflects the pattern beam on the detected mirror surface to a CMOS camera combined with an industrial lens, the COMS camera is connected with the computer, the computer records the result acquired by the COMS camera, and performs image processing and data analysis on the result; the method comprises the steps of enabling a color speckle pattern generated randomly to pass through a beam splitter placed at an inclined angle of 45 degrees through an LCD color display screen, enabling a pattern with half brightness to be shot on a detected mirror surface, enabling the detected mirror surface to receive the speckle pattern, modulating surface information of the detected mirror surface to the speckle pattern when mirror reflection occurs, then reflecting the speckle pattern back to the beam splitter, enabling the beam splitter to split again, reflecting the pattern with half brightness to a COMS camera assembled with an industrial lens, enabling the COMS to acquire the pattern of information of a modulated surface shape and transmit the pattern to a computer, finally processing the acquired information through the computer to obtain the slope of the detected surface, obtaining the detected mirror surface shape through gradient integration, enabling the obtained surface shape to be replaced into a gradient integration formula for iteration, stopping iteration until the difference between the surface shape obtained through gradient integration at the front and the back is smaller than a certain threshold value, and enabling the obtained detected mirror surface shape to be the required.
Drawings
FIG. 1 is a schematic structural view of a coaxial orthojet speckle deflection measuring device according to the present invention.
FIG. 2 is a flow chart of a method for measuring the three-dimensional surface shape of a mirror surface according to the present invention.
Wherein: 1-measured mirror surface, 2-flat beam splitter, 3-COMS camera, 4-industrial lens, 5-computer and 6-LCD color display screen.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the term "comprising" and any variations thereof in the description of the invention and the claims and in the above-described figures is intended to cover a non-exclusive inclusion, such that a process, method, apparatus, article, or device comprising a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or device, but may include other steps or elements not expressly listed.
The deflection operation is developed from fringe projection, a sinusoidal fringe pattern is projected on an object, the fringe pattern on the object can be acquired by a camera at all angles due to diffuse reflection of the object, when the measured object is changed into a mirror surface, the light irradiates on the mirror surface to generate specular reflection, the emitting form of the structured light needs to be changed, so that the deflection operation is generated, fringes are displayed on a display screen, each point on the measured mirror can be covered by the fringes no matter the area of the display screen is large enough, but the three-dimensional surface shape is calculated by using the fringe structured light, 2 multiplied by n pictures are acquired by n steps of phase shifting, and the camera takes a photograph for a long time. In the color speckle deflection operation, the camera can acquire the original 3 speckle patterns at one time by using the color speckle, the acquisition time is shortened to the level as short as the exposure time of the camera, and transient measurement can be performed.
The invention uses a set of coaxial normal incidence light paths to increase the measurable curvature radius range of the system. The method used in the invention is speckle deflection technique, and can complete transient measurement of small curvature radius mirror surface shape by using color speckle and iteration method.
As shown in fig. 2, the method for measuring the three-dimensional surface shape of the mirror surface comprises the following steps:
(1) Performing system calibration, calibrating internal parameters and external parameters of a camera, and constructing a 3D-LUT (3D-Look-Up-Table, 3D display lookup Table) for color crosstalk correction;
(2) Constructing a color speckle pattern, randomly generating a binary speckle pattern, and respectively translating n pixels along an x-axis and a y-axis to obtain an original speckle pattern, a speckle pattern moving along the x-axis and a speckle pattern moving along the y-axis;
(3) Displaying the color speckle pattern on an LCD screen, collecting speckle patterns reflected by a tested mirror by using a color camera, eliminating the influence of color crosstalk and color unbalance, and respectively obtaining speckle of red, green and blue channels through channel separation;
(4) Digital image Correlation matching based on ZNCC (Zero Mean Normalized Cross-Correlation, zero-mean normalized cross Correlation) is respectively carried out on images of a red channel, a green channel, a red channel and a blue channel, so as to obtain the x-direction of each pixel in the speckle pattern
Displacement field magnitudes of the axis and the y-axis;
(5) Calculating the coordinates of each point on the LCD screen, which is separated by n times the pixel width of the screen, corresponding to the CCD of the camera according to the displacement field, and calculating the position of each point corresponding to the sampling point on the measured mirror according to the calibration relation;
(6) Firstly, assuming that a measured mirror is a plane mirror, calculating gradients along the x direction and the y direction at each sampling point on the mirror surface of the measured mirror according to a calibrated geometric relationship and a formula derived by an optical reflection law, and obtaining a rough surface shape of the measured mirror through gradient integration;
(7) The obtained surface shape is taken as the surface shape of the mirror to be measured, the gradients of each point on the mirror to be measured along the x direction and the y direction are recalculated according to the formula in the step (6), and the mirror surface shape to be measured is obtained through gradient integration;
(8) And (3) repeating the step (7) for iteration, and stopping iteration when the difference between the surface shapes obtained by the previous gradient integration and the next gradient integration is smaller than a certain threshold value, wherein the finally obtained surface shape of the measured mirror is the required surface shape of the measured mirror.
According to the invention, three color channels of the display are used for respectively displaying a speckle pattern, and the mirror surface shape is calculated in an iterative optimization mode, compared with the traditional stripe deflection operation, only one picture is required to be acquired, so that the measurement speed is greatly improved, the system has transient measurement capability, meanwhile, the problem that the error of measuring the small curvature radius surface shape is large in the traditional measurement principle is solved, nondestructive, in-place and transient measurement can be realized on the small curvature radius mirror surface, the number of used devices is small, the measurement speed is improved, and the requirement on the measurement environment is reduced.
Preferably, in the step (1), the world coordinates of the camera pinhole and a certain point on the LCD screen and their positions on the CCD are determined during calibration.
Preferably, in the step (2), the three speckle patterns are respectively used as images in three color channels of red, green and blue of the image, so as to obtain one color speckle pattern.
Preferably, in the step (3), the colors collected by the camera when different colors are displayed in the LCD screen are calibrated by constructing a 3D-LUT, and when the camera is used for taking a picture, the original colors displayed on the LCD screen are found by using a lookup table in an inverse manner, so that the influence of color crosstalk and color imbalance is eliminated. In the step (3), distortion correction is performed on the image according to the step (1), and preprocessing operations such as denoising are performed.
Preferably, in the step (4), sub-pixel interpolation based on newton interpolation is used, so that the calculation accuracy is increased. In the step (4), a gradient is firstly required for the photographed speckle pattern, and then digital image correlation matching is carried out on the result of the gradient requirement, so that the displacement field size of each pixel in the speckle pattern along the x axis and the y axis is obtained.
Preferably, in the step (7), interpolation is performed on the surface shape of the previous iteration, and then the position of the sampling point where the emergent light intersects with the mirror surface of the detected mirror is calculated.
As shown in fig. 1, there is also provided a system for mirror three-dimensional surface shape measurement, comprising: the device comprises a measured mirror surface 1, a flat beam splitter 2, a COMS camera 3, an industrial lens 4, a computer 5 and an LCD color display screen 6;
the LCD color display screen is connected with the computer, the computer controls and displays the color speckle patterns, the LCD color display screen and the detected mirror surface are placed face to face, a flat beam splitter is placed on the middle inclined side of the LCD color display screen and the detected mirror surface by 45 degrees, the beam splitter reflects the pattern beam on the detected mirror surface to a CMOS camera combined with an industrial lens, the COMS camera is connected with the computer, the computer records the result acquired by the COMS camera, and performs image processing and data analysis on the result; the method comprises the steps of enabling a color speckle pattern generated randomly to pass through a beam splitter placed at an inclined angle of 45 degrees through an LCD color display screen, enabling a pattern with half brightness to be shot on a detected mirror surface, enabling the detected mirror surface to receive the speckle pattern, modulating surface information of the detected mirror surface to the speckle pattern when mirror reflection occurs, then reflecting the speckle pattern back to the beam splitter, enabling the beam splitter to split again, reflecting the pattern with half brightness to a COMS camera assembled with an industrial lens, enabling the COMS to acquire the pattern of information of a modulated surface shape and transmit the pattern to a computer, finally processing the acquired information through the computer to obtain the slope of the detected surface, obtaining the detected mirror surface shape through gradient integration, enabling the obtained surface shape to be replaced into a gradient integration formula for iteration, stopping iteration until the difference between the surface shape obtained through gradient integration at the front and the back is smaller than a certain threshold value, and enabling the obtained detected mirror surface shape to be the required.
The invention uses a coaxial normal incidence light path to enable the image of the measured mirror in the flat beam splitter to be opposite to the CMOS camera, so that the incidence angles of the light of the speckle pattern on the left side and the right side of the measured mirror are similar, and under the condition that the size of the color speckle pattern is fixed, the field of view shot by the camera is the largest and concentric with the optical axis of the measured mirror.
Preferably, the focus of the camera is focused on the LCD display screen, so that the speckle on the screen is shot clearly as much as possible; the industrial lens is a lens with small aperture size, and under the condition that the focal length of the lens is fixed, the smaller the aperture, the larger the depth of field, the more clearly the surface of the measured lens is shot when focusing on the LCD display screen, and the spatial resolution of the surface of the measured lens is improved.
Preferably, the brightness, size and resolution of the LCD display screen are selected in combination with practical situations, and the brightness thereof enables the lens to collect a clear speckle image when using a small-size aperture, the size thereof enables the image reflected by the display screen through the measured mirror to be not smaller than the field of view of the camera, and the resolution thereof ensures that one pixel on the display screen can be collected by a plurality of pixels on the camera at the same time.
Preferably, the speckle pattern is randomly generated, is bright high-contrast binary random speckle, the duty cycle of the speckle is close to 50%, and the size of the speckle characteristic points is selected and set according to the resolution of the LCD display screen and the distance between the camera and the display screen.
One embodiment of the present invention is described in detail below.
In this example, a mirror having a caliber of 25.4cm was used as the mirror to be measured. The resolution of the LCD display screen is 1920 multiplied by 1200 pixels, the caliber of the flat beam splitter is 50.8mm, and the resolution of the camera unit of the COMS camera is 3088 multiplied by 2064 pixels.
The measurement steps are as follows:
step one: performing system calibration;
calibrating internal parameters and external parameters of the camera, calibrating the internal parameters and the external parameters of the camera, and constructing a 3D-LUT for correcting color crosstalk. During calibration, it is necessary to determine the world coordinates of the camera pinhole and a certain point on the LCD screen, and their position on the CCD.
Step two: constructing a color speckle pattern;
and randomly generating a binary speckle pattern, respectively translating the pattern along the x-axis and the y-axis by 6 pixels to obtain an original speckle pattern, a speckle pattern moving along the x-axis and a speckle pattern moving along the y-axis, and respectively taking the three speckle patterns as images in red, green and blue color channels of the image to obtain a color speckle pattern.
Step three: the LCD display screen displays the color speckle pattern, and the camera collects the speckle pattern reflected by the tested mirror and separates the speckle patterns in different channels;
the constructed color speckle pattern was prepared as 1:2, namely a characteristic point in the speckle pattern is displayed by 4 pixel points on the display screen, a color CMOS camera is used for shooting the speckle pattern reflected by the detected mirror, each pixel in the interested area is input into the 3D-LUT constructed in the step one, the corresponding source color is obtained through searching, and the speckle patterns of the red, green and blue channels are obtained through channel separation.
Step four: and respectively carrying out digital image correlation matching based on ZNCC on the images of the red channel and the green channel as well as the images of the red channel and the blue channel, wherein the formula of the ZNCC algorithm is as follows:
Figure BDA0004177639130000091
selecting 21×21 pixels with sub-region size, searching 41×41 pixels, and calculating to obtain displacement field sizes of each pixel along x-axis and y-axis in the speckle pattern;
step five: calculating the coordinates of each point on the LCD screen, which is separated by n x the screen pixel width, on the CCD of the camera according to the displacement field, and calculating the position (x m ,y m )；
Step six: assume that the mirror to be measured is a plane mirror, namely W old (x m ,y m ) =0, a formula derived from the calibrated geometry and the law of optical reflection
Figure BDA0004177639130000092
Calculating gradients along the x direction and the y direction at each sampling point on the mirror surface of the measured mirror, and obtaining the rough surface shape of the measured mirror through gradient integration;
step seven: the obtained surface shape is taken as the surface shape of the mirror to be measured, the gradients of each point on the mirror surface of the mirror to be measured along the x direction and the y direction are recalculated according to the formula (2) in the step six, and the mirror surface shape to be measured is obtained through gradient integration;
step eight: and repeating the step seven for iteration, and stopping iteration when the difference PV between the surface shapes obtained by the previous gradient integration and the next gradient integration is smaller than 1um, wherein the finally obtained surface shape of the measured mirror is the required surface shape of the measured mirror.
The present invention is not limited to the preferred embodiments, but can be modified in any way according to the technical principles of the present invention, and all such modifications, equivalent variations and modifications are included in the scope of the present invention.

Claims (10)

1. A method for measuring the three-dimensional surface shape of a mirror surface is characterized by comprising the following steps: which comprises the following steps:
(1) Performing system calibration, calibrating internal parameters and external parameters of a camera, and constructing a three-dimensional display lookup table 3D-LUT for color crosstalk correction;
(2) Constructing a color speckle pattern, randomly generating a binary speckle pattern, and respectively translating n pixels along an x-axis and a y-axis to obtain an original speckle pattern, a speckle pattern moving along the x-axis and a speckle pattern moving along the y-axis;
(3) Displaying the color speckle pattern on an LCD screen, collecting speckle patterns reflected by a tested mirror by using a color camera, eliminating the influence of color crosstalk and color unbalance, and respectively obtaining speckle of red, green and blue channels through channel separation;
(4) Respectively carrying out zero-mean normalized cross-correlation ZNCC-based digital image correlation matching on images of a red channel, a green channel, a red channel and a blue channel to obtain the displacement field sizes of each pixel along an x axis and a y axis in a speckle pattern;
(5) Calculating the coordinates of each point on the LCD screen, which is corresponding to the CCD of the camera, with the interval n times the pixel width of the screen according to the displacement field, and calculating the position of each point corresponding to the sampling point on the measured mirror according to the calibration relation;
(6) Firstly, assuming that a measured mirror is a plane mirror, calculating gradients along the x direction and the y direction at each sampling point on the mirror surface of the measured mirror according to a calibrated geometric relationship and a formula derived by an optical reflection law, and obtaining a rough surface shape of the measured mirror through gradient integration;
(7) The obtained surface shape is taken as the surface shape of the mirror to be measured, the gradients of each point on the mirror to be measured along the x direction and the y direction are recalculated according to the formula in the step (6), and the mirror surface shape to be measured is obtained through gradient integration;
(8) And (3) repeating the step (7) for iteration, and stopping iteration when the difference between the surface shapes obtained by the previous gradient integration and the next gradient integration is smaller than a certain threshold value, wherein the finally obtained surface shape of the measured mirror is the required surface shape of the measured mirror.
2. The method for three-dimensional surface shape measurement of a mirror surface according to claim 1, wherein: in the step (1), during the calibration process, the world coordinates of the camera pinhole and a certain point on the LCD screen and their positions on the CCD are determined.
3. A method of specular three-dimensional surface shape measurement according to claim 2, wherein: in the step (2), the three speckle patterns are respectively used as images in the red, green and blue color channels of the image, so as to obtain a color speckle pattern.
4. A method of specular three-dimensional surface shape measurement according to claim 3, wherein: in the step (3), the colors acquired by the camera when different colors are displayed in the LCD screen are calibrated by constructing a 3D-LUT, and the original colors displayed by the LCD screen are found out by using a lookup table in an inverse way when the camera is used for shooting pictures, so that the influence of color crosstalk and color imbalance is eliminated.
5. The method for three-dimensional surface shape measurement of a mirror surface according to claim 4, wherein: in the step (4), the sub-pixel interpolation by the newton interpolation method is used, so that the calculation accuracy is increased.
6. A method of specular three-dimensional surface shape measurement according to claim 5, wherein: in the step (7), interpolation is firstly carried out on the surface shape of the last iteration, and then the position of the sampling point where the emergent light ray intersects with the mirror surface of the detected mirror is calculated.
7. The system of the method for measuring the three-dimensional surface shape of a mirror surface according to claim 1, wherein: it comprises the following steps: the device comprises a detected mirror surface (1), a flat beam splitter (2), a COMS camera (3), an industrial lens (4), a computer (5) and an LCD color display screen (6);
the LCD color display screen is connected with the computer, the computer controls and displays the color speckle patterns, the LCD color display screen and the detected mirror surface are placed face to face, a flat beam splitter is placed on the middle inclined side of the LCD color display screen and the detected mirror surface by 45 degrees, the beam splitter reflects the pattern beam on the detected mirror surface to a CMOS camera combined with an industrial lens, the COMS camera is connected with the computer, the computer records the result acquired by the COMS camera, and performs image processing and data analysis on the result; the method comprises the steps of enabling a color speckle pattern generated randomly to pass through a beam splitter placed at an inclined angle of 45 degrees through an LCD color display screen, enabling a pattern with half brightness to be shot on a detected mirror surface, enabling the detected mirror surface to receive the speckle pattern, modulating surface information of the detected mirror surface to the speckle pattern when mirror reflection occurs, then reflecting the speckle pattern back to the beam splitter, enabling the beam splitter to split again, reflecting the pattern with half brightness to a COMS camera assembled with an industrial lens, enabling the COMS to acquire the pattern of information of a modulated surface shape and transmit the pattern to a computer, finally processing the acquired information through the computer to obtain the slope of the detected surface, obtaining the detected mirror surface shape through gradient integration, enabling the obtained surface shape to be replaced into a gradient integration formula for iteration, stopping iteration until the difference between the surface shape obtained through gradient integration at the front and the back is smaller than a certain threshold value, and enabling the obtained detected mirror surface shape to be the required.
8. The system of claim 7, wherein the method for measuring the three-dimensional surface shape of the mirror surface comprises: focusing the focus of the camera on the LCD display screen, and shooting the speckles displayed on the screen as clearly as possible; the industrial lens is a lens with small aperture size, and under the condition that the focal length of the lens is fixed, the smaller the aperture, the larger the depth of field, the more clearly the surface of the measured lens is shot when focusing on the LCD display screen, and the spatial resolution of the surface of the measured lens is improved.
9. The system of claim 8, wherein the method for measuring the three-dimensional surface shape of the mirror surface comprises: the brightness, the size and the resolution of the LCD display screen are selected in combination with the actual situation, the brightness ensures that a clear speckle image can be acquired when the lens uses a small-size aperture, the size ensures that the image reflected by the display screen through the measured mirror is not smaller than the field of view of the camera, and the resolution ensures that one pixel on the display screen can be acquired by a plurality of pixels on the camera at the same time.
10. The system of claim 9, wherein the method for measuring the three-dimensional surface shape of the mirror surface comprises: the speckle pattern is randomly generated and is bright high-contrast binary random speckle, the duty ratio of the speckle is close to 50%, and the size of the speckle characteristic points is selectively set according to the resolution of an LCD display screen and the distance between a camera and the display screen.
CN202310395978.1A 2023-04-13 2023-04-13 Method and system for measuring three-dimensional surface shape of mirror surface Pending CN116379959A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310395978.1A CN116379959A (en) 2023-04-13 2023-04-13 Method and system for measuring three-dimensional surface shape of mirror surface

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310395978.1A CN116379959A (en) 2023-04-13 2023-04-13 Method and system for measuring three-dimensional surface shape of mirror surface

Publications (1)

Publication Number Publication Date
CN116379959A true CN116379959A (en) 2023-07-04

Family

ID=86976728

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202310395978.1A Pending CN116379959A (en) 2023-04-13 2023-04-13 Method and system for measuring three-dimensional surface shape of mirror surface

Country Status (1)

Country Link
CN (1) CN116379959A (en)

Similar Documents

Publication Publication Date Title
CN110392252B (en) Method for generating correction model of camera to correct aberration
US8432395B2 (en) Method and apparatus for surface contour mapping
US11619485B2 (en) Hybrid 3D optical scanning system
CN107084794B (en) Flame three-dimensional temperature field measuring system and method based on light field layered imaging technology
US8582824B2 (en) Cell feature extraction and labeling thereof
CN109883391B (en) Monocular distance measurement method based on digital imaging of microlens array
WO2013119455A1 (en) Shape reflector and surface contour mapping
JP2015534091A (en) Method for controlling the linear dimension of a three-dimensional object
CN107271445B (en) Defect detection method and device
CN104197846B (en) Method for measuring displacement of reflector based on characteristic pattern reflection
CN108955555B (en) High-precision high-temperature deformation measuring method
Traxler et al. Experimental comparison of optical inline 3D measurement and inspection systems
Rachakonda et al. Sources of errors in structured light 3D scanners
CN112489109A (en) Three-dimensional imaging system method and device and three-dimensional imaging system
CN108399640A (en) A kind of speculum relative pose measurement method based on camera calibration
JP5956296B2 (en) Shape measuring apparatus and shape measuring method
CN110322561A (en) 3D camera and its measurement method for the unordered sorting of robot
CN112815846A (en) 2D and 3D composite high-precision vision device and measuring method
CN116379959A (en) Method and system for measuring three-dimensional surface shape of mirror surface
KR101555027B1 (en) Appapatus for three-dimensional shape measurment and method the same
RU125335U1 (en) DEVICE FOR MONITORING LINEAR SIZES OF THREE-DIMENSIONAL OBJECTS
US20160349045A1 (en) A method of measurement of linear dimensions of three-dimensional objects
CN109741384A (en) The more distance detection devices and method of depth camera
CN113160393A (en) High-precision three-dimensional reconstruction method and device based on large field depth and related components thereof
CN114674244B (en) Coaxial normal incidence speckle deflection measurement method and device

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination