Double-mirror-surface calibration plate and calibration method of common-reference double-mirror-surface phase deflection measurement system based on calibration plate

Abstract

The invention discloses a double-mirror-surface calibration plate and a calibration method of a common-reference double-mirror-surface phase deflection measurement system based on the calibration plate. The double-mirror-surface calibration plate is composed of a double-mirror-surface calibration plate A surface, a double-mirror-surface calibration plate B surface and a substrate. The mirror surface calibration plate A surface and the double-mirror surface calibration plate B surface are respectively arranged on two surfaces of the substrate; the double-mirror-surface calibration plate A surface and the double-mirror-surface calibration plate B surface are both provided with the same circular ring arrays, and the circular ring arrays are in mirror symmetry about the substrate; the circular ring array is composed of same circular rings which are distributed in rows and columns; the distances between the circle centers of every two adjacent circular rings are the same in the row direction and the column direction. The system calibration method and the double-mirror-surface calibration plate for system common-reference calibration are provided for a double-mirror-surface element surface shape and pose measurement system, the design is ingenious, a new thought and method are provided for calibration of a double-mirror-surface element three-dimensional shape measurement system, and the practical application value is achieved.

Description

Technical Field

[0001] The invention relates to the field of optical three-dimensional shape measurement, in particular to a double-mirror calibration plate and a calibration method for a common reference double-mirror phase deflection measurement system based on the calibration plate. Background Art

[0002] Phase deflectometry is an optical three-dimensional shape measurement technology suitable for mirror surface shape. Based on the principle of fringe reflection, the standard sinusoidal fringes generated by the computer are transmitted to the display screen to display the standard sinusoidal fringes. The mirror to be measured and the mirror calibration plate are imaged through reflection in succession. The standard sinusoidal fringes displayed on the display screen are deformed by the modulation of the mirror surface shape, and then the virtual image of the deformed fringes is collected from another direction by the CCD camera and transmitted back to the computer for demodulation calculation. By calculating and comparing the phase information in the sinusoidal fringes reflected by the mirror calibration plate and the phase information in the sinusoidal fringes reflected by the mirror to be measured, the depth of each point on the measured mirror relative to the reference position of the calibration plate is solved, and then the three-dimensional shape of the mirror is restored.

[0003] In principle, traditional phase deflectometry can only measure a single mirror, but there are many important dual-mirror components in military weapons and equipment, astronomical telescopes, and aerospace equipment. In order to ensure the functionality of such components, it is necessary to simultaneously obtain the dual-mirror surface shape and the position and posture between the two mirrors, which poses a huge challenge to existing precision measurement technology. For the simultaneous measurement of the surface shape and posture of such dual-mirror components, effective deflectometry theory and methods are required. System calibration is the most important step, but the existing calibration methods cannot meet the calibration requirements of dual-mirror component measurement systems. The existing calibration methods are specifically shown below:

[0004] The paper "Deng Xiaoting, Gao Nan, Zhang Zonghua. System parameter calibration method based on direct phase measurement [J]. Laser & Optoelectronics Progress, 2018, 55(06): 230-237" proposes a method to obtain unknown parameters in the system model based on phase information, establish a direct relationship between phase and depth, and use phase data to calibrate the position of the LCD display in the camera coordinate system. The accuracy of the external parameters of the display screen calibrated using phase information and traditional geometric feature identification points chessboard is compared, proving that this method can accurately calibrate system parameters and obtain high-precision three-dimensional measurement data. However, in the implementation of the method, the proposed model requires the two displays to remain parallel, which has a great impact on the accuracy of the entire system and has a large error. At the same time, it cannot provide an effective solution for the measurement of dual-mirror elements.

[0005] The document "Li Yue. Research on deflection measurement technology based on dual-screen transmission display [D]. Tianjin: Hebei University of Technology, 2021." proposes a system parameter calibration method for the three-dimensional shape measurement technology of non-continuous mirror objects. The circular pattern on the plane mirror and the transparent screen is captured by the camera, and the spatial position relationship between the two planes relative to the camera coordinate system is obtained, and the distance from the reference plane mirror to the transparent display screen is obtained. This method can be used for three-dimensional shape measurement of non-continuous mirrors and has certain practical application value. However, this method can only measure single-mirror components and cannot meet the three-dimensional shape measurement and system calibration of dual-mirror components.

[0006] In summary, the above measurement method or calibration method can solve the common single-mirror three-dimensional shape measurement, but cannot meet the three-dimensional shape measurement and calibration of dual-mirror components. Therefore, providing a method for solving the surface shape measurement and system calibration of dual-mirror components is an urgent problem to be solved. Summary of the invention

[0007] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a dual-mirror calibration plate and a calibration method for a common-reference dual-mirror phase deflection measurement system based on the calibration plate.

[0008] The technical solution of the present invention to solve the technical problem of the calibration plate is to provide a double-mirror calibration plate, characterized in that the double-mirror calibration plate is composed of a double-mirror calibration plate surface A, a double-mirror calibration plate surface B and a substrate;

[0009] The mirror calibration plate surface A and the double mirror calibration plate surface B are respectively arranged on the two surfaces of the substrate; the double mirror calibration plate surface A and the double mirror calibration plate surface B are parallel to each other and the normal angles are both 180°; the double mirror calibration plate surface A and the double mirror calibration plate surface B are both provided with the same circular ring array and the circular ring array is mirror-symmetrical about the substrate; the circular ring array is composed of the same circular rings distributed in rows and columns; along the row direction and the column direction, the distance between the centers of two adjacent circular rings is the same.

[0010] The technical solution of the present invention to solve the technical problem of the method is to provide a calibration method for a common reference dual-mirror phase deflection measurement system based on the dual-mirror calibration plate, characterized in that the calibration method comprises the following steps:

[0011] 1) Design of double mirror calibration plate:

[0012] Take the center of the circle in the lower left corner of the circle array on the double mirror calibration plate A surface as the origin, and establish the coordinate system O with the double mirror calibration plate A surface as the reference plane. A -X A Y A Z A; The ring array is p columns × q rows; along the row direction and the column direction, the distance between the centers of two adjacent rings is r; then the center of the ring on the A surface of the double mirror calibration plate is in the coordinate system O A -X A Y A Z A The coordinates in are ((p-1)r,(q-1)r,0);

[0013] Take the center of the lower left corner of the circular ring array on the double mirror calibration plate B as the origin, and establish the coordinate system O with the double mirror calibration plate B as the reference plane. B -X B Y B Z B ; The ring array is p columns × q rows; along the row direction and the column direction, the distance between the centers of two adjacent rings is r; then the center of the ring on the B surface of the double mirror calibration plate is in the coordinate system O B -X B Y B Z B The coordinates in are ((p-1)r,(q-1)r,0);

[0014] The distance between the double mirror calibration plate surface A and the double mirror calibration plate surface B is D;

[0015] 2) Calibrate the internal parameters of the camera;

[0016] 3) Build a common reference dual-mirror phase deflection measurement system:

[0017] The system includes a double-mirror calibration plate, a computer, a first CCD camera, a second CCD camera, a first high-precision horizontal moving guide rail, a second high-precision horizontal moving guide rail, a third high-precision horizontal moving guide rail, a first display screen and a second display screen;

[0018] The first high-precision horizontal moving guide rail is fixed on the optical platform; the first display screen is slidably mounted on the first high-precision horizontal moving guide rail, is perpendicular to the optical platform and parallel to the A surface of the double-mirror calibration plate, and can be linearly moved along the first high-precision horizontal moving guide rail to the initial position of the first display screen and the moving position of the first display screen;

[0019] The second high-precision horizontal moving guide rail is fixed on the optical platform; the second display screen is slidably mounted on the second high-precision horizontal moving guide rail, perpendicular to the optical platform and parallel to the B surface of the double-mirror calibration plate, and can be linearly moved along the second high-precision horizontal moving guide rail to the second display screen initial position and the second display screen moving position;

[0020] The third high-precision horizontal moving guide rail is fixed on the optical platform, the double-mirror calibration plate is placed on the third high-precision horizontal moving guide rail, the double-mirror calibration plate is perpendicular to the optical platform and can move linearly along the third high-precision horizontal moving guide rail; the first CCD camera is located on one side of the double-mirror calibration plate surface A, and the first CCD camera, the first display screen and the double-mirror calibration plate surface A are in a triangular measurement relationship in space; the second CCD camera is located on one side of the double-mirror calibration plate surface B, and the second CCD camera, the second display screen and the double-mirror calibration plate surface B are in a triangular measurement relationship in space;

[0021] The computer, the first CCD camera, the first high-precision horizontal moving guide rail, the first display screen and the double-mirror calibration plate surface A constitute the A-side subsystem; the computer, the second CCD camera, the second high-precision horizontal moving guide rail, the second display screen and the double-mirror calibration plate surface B constitute the B-side subsystem;

[0022] The computer is respectively connected to the first display screen, the second display screen, the first CCD camera, the second CCD camera, the first high-precision horizontal moving guide rail, the second high-precision horizontal moving guide rail and the third high-precision horizontal moving guide rail;

[0023] 4) Common reference calibration of the system:

[0024] In order to realize the common reference calibration of the A-side subsystem and the B-side subsystem, the coordinate system O A -X A Y A Z A and coordinate system O B -X B Y B Z B The conversion relationship is derived:

[0025] Assume coordinate system O B -X B Y B Z B To coordinate system O A -X A Y A Z A The rotation matrix is The translation vector is The transformation matrix is In coordinate system O A -X A Y A Z A Assume that a feature point P on the B surface of the double-mirror calibration plate is in the coordinate system O B -X B Y B Z B The coordinates below are In the coordinate system OA -X A Y A Z A The coordinates below are Then we have:

[0026]

[0027] In formula (1), the transformation matrix

[0028] 5) Obtain the system parameters that need to be calibrated:

[0029] For the A-side subsystem, the distance between the initial position of the first display screen and the moved position of the first display screen is Δd A The distance between the initial position of the first display screen and the double mirror calibration plate A when it is at the system reference position is d A , the coefficients of the relationship of the A-side subsystem obtained by lateral calibration are (a0, a1, a2, b0, b1, b2) A ;

[0030] For the B-side subsystem, the distance between the initial position of the second display screen and the moved position of the second display screen is Δd B The distance between the initial position of the second display screen and the double mirror calibration plate B when it is at the system reference position is d B , the coefficients of the relationship of the B-side subsystem obtained by lateral calibration are (a0, a1, a2, b0, b1, b2) B ;

[0031] 6) Perform system calibration: first perform depth calibration, then perform lateral calibration.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The present invention proposes a system calibration method and a dual-mirror calibration plate for system common reference calibration for a dual-mirror element surface shape and posture measurement system. The design is ingenious, providing a new idea and method for the calibration of a dual-mirror element three-dimensional shape measurement system, which has practical application value. At the same time, the calibration method adopts non-contact measurement, directly establishes the relationship between phase and depth, and has high measurement accuracy.

[0034] 2) Clever design: For the measurement of the three-dimensional morphology of a dual-mirror component, at least two systems are required to measure the two mirrors respectively. The present invention utilizes this feature to design the calibration plate as a double-sided calibration plate, which is simple in concept and easy to implement.

[0035] 3) A dual-mirror calibration plate is introduced into the calibration process to realize common reference calibration: two phase deflection measurement systems share a dual-mirror calibration plate for calibration. According to the conversion relationship between the two coordinate systems of the dual-mirror calibration plate obtained by calibration, the three-dimensional morphology data of the two phase deflection measurement systems are converted to the same coordinate system to realize common reference calibration of the two phase deflection measurement systems, thereby achieving the purpose of simultaneously and accurately measuring the three-dimensional morphology of the two surfaces of the dual-mirror element, ensuring the uniformity of the reference and the reliability of the calibration results, and providing technical support for the rapid and high-precision acquisition of the dual-mirror surface shape and posture.

[0036] 4) High measurement accuracy: By utilizing the spatial geometric relationship and imaging principle of the components in the system, a direct mapping relationship between phase and depth is established, avoiding the error accumulation in traditional methods. This method can be used for three-dimensional morphology measurement of non-continuous, large curvature and complex mirror objects, and has a wider range of applications.

[0037] 5) Non-contact measurement and non-destructive testing: This method is an optical three-dimensional topography measurement method. It does not contact the surface being measured and will not damage the surface being measured.

[0038] 6) The dual-mirror calibration plate and calibration method of the present invention are universal and easy to promote: in practical applications, they play an important application value in accurately measuring the surface shape and position of important dual-mirror components on military weapons and equipment, astronomical telescopes, and aerospace equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the three-dimensional structure of the double-mirror calibration plate of the present invention;

[0040] Figure 2 It is a schematic diagram of the arrangement of the circular ring array of the double-mirror calibration plate of the present invention;

[0041] Figure 3 It is a structural schematic diagram of the common reference dual-mirror phase deflection measurement system of the present invention;

[0042] Figure 4 A schematic diagram of the positions of the first display screen and the second display screen of the measurement system of the present invention;

[0043] Figure 5 It is a schematic diagram of the common reference calibration structure of the present invention;

[0044] Figure 6 The surface texture image of the double-mirror calibration plate A side collected from the double-mirror calibration plate A side of the present invention;

[0045] Figure 7 This is a surface texture image of the double-mirror calibration plate B collected from the double-mirror calibration plate B side of the present invention.

[0046] In the figure, double mirror calibration plate A surface 1, double mirror calibration plate B surface 2, circular array 3, computer 4, first CCD camera 5, second CCD camera 6, first display screen initial position 7, second display screen initial position 8, first display screen moving position 9, second display screen moving position 10, double mirror calibration plate 11, first high precision horizontal moving guide rail 12, second high precision horizontal moving guide rail 13, third high precision horizontal moving guide rail 14, first display screen 15, second display screen 16. DETAILED DESCRIPTION

[0047] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the present invention.

[0048] The present invention provides a high-precision double-mirror calibration plate (referred to as double-mirror calibration plate), characterized in that the double-mirror calibration plate 11 is composed of a double-mirror calibration plate A surface 1, a double-mirror calibration plate B surface 2 and a substrate;

[0049] The mirror calibration plate A surface 1 and the double mirror calibration plate B surface 2 are respectively arranged on the two sides of the substrate; the double mirror calibration plate A surface 1 and the double mirror calibration plate B surface 2 are parallel to each other and the normal angles are both 180°; the double mirror calibration plate A surface 1 and the double mirror calibration plate B surface 2 are both provided with the same circular ring array 3 (see Figure 2 ) and the circular ring array 3 is mirror-symmetrical about the substrate; the circular ring array 3 is composed of identical circular rings distributed in rows and columns; along the row direction and the column direction, the distance between the centers of two adjacent circular rings is the same.

[0050] Preferably, the substrate is a glass plate coated with a silver reflective film.

[0051] Preferably, the circular ring array 3 is centrally arranged on the double-mirror calibration plate surface A 1 and the double-mirror calibration plate surface B 2 .

[0052] The present invention also provides a calibration method (hereinafter referred to as calibration method) for a common reference dual-mirror phase deflection measurement system based on the dual-mirror calibration plate 11, characterized in that the calibration method comprises the following steps:

[0053] 1) Design of double mirror calibration plate 11:

[0054] Take the center of the circle in the lower left corner of the circle array 3 of the double mirror calibration plate A surface 1 as the origin, and establish a coordinate system O with the double mirror calibration plate A surface 1 as the reference plane. A -X A Y A Z A ; The ring array 3 is p columns × q rows; along the row direction and the column direction, the distance between the centers of two adjacent rings is r; then the center of the ring on the A surface 1 of the double mirror calibration plate is in the coordinate system O A -XA Y A Z A The coordinates in are ((p-1)r,(q-1)r,0);

[0055] Take the center of the circle in the lower left corner of the circle array 3 of the double mirror calibration plate B surface 2 as the origin, and establish a coordinate system O with the double mirror calibration plate B surface 2 as the reference plane. B -X B Y B Z B ; The ring array 3 is p columns × q rows; along the row direction and the column direction, the distance between the centers of two adjacent rings is r; then the center of the ring on the B surface 2 of the double mirror calibration plate is in the coordinate system O B -X B Y B Z B The coordinates in are ((p-1)r,(q-1)r,0);

[0056] The distance between the double-mirror calibration plate A surface 1 and the double-mirror calibration plate B surface 2 (i.e., the thickness of the double-mirror calibration plate 11) is D;

[0057] 2) Calibrate the internal parameters of the camera;

[0058] Preferably, step 2) specifically includes: fixing the first CCD camera 5 on an optical platform, selecting a plurality of camera calibration positions within the depth of field of the first CCD camera 5, placing a camera calibration plate in different postures at each camera calibration position, the first CCD camera 5 collects the camera calibration plate image at each camera calibration position, extracting the pixel coordinates of the corner points of the camera calibration plate, the distance between the corner points is known, and using the Zhang Zhengyou camera calibration method to determine the internal parameters of the first CCD camera 5 to correct the fringe image distortion;

[0059] The same method is used to determine the internal parameters of the second CCD camera 6 to correct the fringe image distortion.

[0060] Preferably, in step 2), the camera calibration plate adopts a checkerboard calibration plate.

[0061] 3) Build a common reference dual-mirror phase deflection measurement system (referred to as the system, see Figure 3 ):

[0062] The system includes a double mirror calibration plate 11, a computer 4, a first CCD camera 5, a second CCD camera 6, a first high-precision horizontal moving guide rail 12, a second high-precision horizontal moving guide rail 13, a third high-precision horizontal moving guide rail 14, a first display screen 15 and a second display screen 16;

[0063] The first high-precision horizontal moving guide rail 12 is fixed on the optical platform; the first display screen 15 is slidably mounted on the first high-precision horizontal moving guide rail 12, perpendicular to the optical platform and parallel to the double-mirror calibration plate A surface 1, and can be linearly moved along the first high-precision horizontal moving guide rail 12 to the first display screen initial position 7 and the first display screen moving position 9;

[0064] The second high-precision horizontal moving guide rail 13 is fixed on the optical platform; the second display screen 16 is slidably mounted on the second high-precision horizontal moving guide rail 13, perpendicular to the optical platform and parallel to the double-mirror calibration plate B surface 2, and can be linearly moved along the second high-precision horizontal moving guide rail 13 to the second display screen initial position 8 and the second display screen moving position 10;

[0065] The third high-precision horizontal moving guide rail 14 is fixed on the optical platform, and the double-mirror calibration plate 11 is placed on the third high-precision horizontal moving guide rail 14. The double-mirror calibration plate 11 is perpendicular to the optical platform and can move linearly along the third high-precision horizontal moving guide rail 14; the first CCD camera 5 is located on one side of the double-mirror calibration plate A surface 1, and the first CCD camera 5, the first display screen 15 and the double-mirror calibration plate A surface 1 are in a triangular measurement relationship in space; the second CCD camera 6 is located on one side of the double-mirror calibration plate B surface 2, and the second CCD camera 6, the second display screen 16 and the double-mirror calibration plate B surface 2 are in a triangular measurement relationship in space;

[0066] The computer 4, the first CCD camera 5, the first high-precision horizontal moving guide rail 12, the first display screen 15 and the double-mirror calibration plate A surface 1 constitute the A side subsystem (i.e., the A side phase deflection measurement subsystem); the computer 4, the second CCD camera 6, the second high-precision horizontal moving guide rail 13, the second display screen 16 and the double-mirror calibration plate B surface 2 constitute the B side subsystem (i.e., the B side phase deflection measurement subsystem); the A side subsystem and the B side subsystem share a computer;

[0067] The computer 4 is connected to the first display screen 15 and the second display screen 16 via the HDMI interface, and controls the first display screen 15 and the second display screen 16 to respectively display three groups of sinusoidal stripes that meet the best three-stripe selection method; the computer 4 is connected to the first CCD camera 5 and the second CCD camera 6 via the USB3.0 interface, and controls the first CCD camera 5 and the second CCD camera 6 to collect stripe images; the computer 4 is connected to the first high-precision horizontal moving guide rail 12, the second high-precision horizontal moving guide rail 13 and the third high-precision horizontal moving guide rail 14, and controls the first display screen 15, the second display screen 16 and the double-mirror calibration plate 11 thereon to move precisely;

[0068] 4) Common reference calibration of the system:

[0069] In order to realize the common reference calibration of the A-side subsystem and the B-side subsystem of the double mirror calibration plate 11, the coordinate system O A -X A Y A Z A and coordinate system O B -X B Y B Z B The conversion relationship is derived (such as Figure 5 shown):

[0070] Assume coordinate system O B -X B Y B Z B To coordinate system O A -X A Y A Z A The rotation matrix is The translation vector is The transformation matrix is In coordinate system O A -X A Y A Z A Assume that a feature point P on the B surface 2 of the double-mirror calibration plate is in the coordinate system O B -X B Y B Z B The coordinates below are In the coordinate system O A -X A Y A Z A The coordinates below are Then we have:

[0071]

[0072] In formula (1), the transformation matrix

[0073] Preferably, in step 4), the conversion matrix The calculation method includes the following steps:

[0074] 4.1) With the double-mirror calibration plate A surface 1 as the reference plane coordinate system, it is denoted as boardA, with the double-mirror calibration plate B surface 2 as the reference plane coordinate system, it is denoted as boardB, the first CCD camera 5 coordinate system is denoted as camera1, and the second CCD camera 6 coordinate system is denoted as camera2; the conversion relationship from coordinate system boardB to coordinate system boardA is: The conversion relationship from coordinate system camera1 to coordinate system camera2 is: The conversion relationship from coordinate system boardB to coordinate system camera2 is: The conversion relationship from coordinate system boardA to coordinate system camera1 is: (like Figure 5 shown);

[0075] The relative positions of the double-mirror calibration plate A surface 1 and the double-mirror calibration plate B surface 2 remain unchanged, and the positions of the first CCD camera 5 and the second CCD camera 6 remain unchanged, ensuring that the double-mirror calibration plate A surface 1 is within the depth of field of the first CCD camera 5 and the double-mirror calibration plate B surface 2 is within the depth of field of the second CCD camera 6. The double-mirror calibration plate 11 is transformed into n different postures (n>3), and the first CCD camera 5 and the second CCD camera 6 take a group of surface texture images for each posture of the double-mirror calibration plate 11 (each group consists of two surface texture images, one for each CCD camera, such as Figure 6 and Figure 7 As shown), extract the circular array 3 of the surface texture map, calculate the conversion matrix of the double mirror calibration plate A surface 1 and the double mirror calibration plate B surface 2 relative to the first CCD camera 5 and the second CCD camera 6 in each posture of the double mirror calibration plate 11; for each surface texture map in each group, there is:

[0076]

[0077] In formula (2), The surface texture image of the double-mirror calibration plate A surface 1 captured by the first CCD camera 5 is directly solved; The surface texture image of the double-mirror calibration plate surface B 2 captured by the second CCD camera 6 is directly solved; is an unknown quantity, but since there is no relative motion between the first CCD camera 5 and the second CCD camera 6, for each set of surface texture images, are the same; Formula (2) is transformed to obtain:

[0078]

[0079] M1 represents the first posture of the dual-mirror calibration plate 11, and M2 represents the second posture of the dual-mirror calibration plate 11. From formula (3), we can get:

[0080]

[0081] Multiply both sides of equation (4) by And multiply right get:

[0082]

[0083] For all n sets of surface texture images corresponding to n different postures collected, n-1 equations are obtained:

[0084]

[0085] For equation (5), Then we get:

[0086] A×X=X×B (7)

[0087] 4.2) Since A and B in A×X=X×B can be obtained through camera calibration, X (i.e., the transformation matrix ) is transformed into the problem of solving the hand-eye calibration equation AX = XB, and the rotation matrix is ​​obtained using a two-step method. with translation vector The transformation matrix can be obtained

[0088] 5) Obtain the system parameters that need to be calibrated:

[0089] For the A-side subsystem, the distance between the first display screen initial position 7 and the first display screen moving position 9 is Δd A , the distance between the initial position 7 of the first display screen and the double mirror calibration plate A surface 1 when it is at the system reference position is d A , the coefficients of the relationship of the A-side subsystem obtained by lateral calibration are (a0, a1, a2, b0, b1, b2) A ;

[0090] For the B-side subsystem, the distance between the second display screen initial position 8 and the second display screen shift position 10 is Δd B The distance between the initial position 8 of the second display screen and the double mirror calibration plate B surface 2 when it is at the system reference position is d B , the coefficients of the relationship of the B-side subsystem obtained by lateral calibration are (a0, a1, a2, b0, b1, b2) B ;

[0091] 6) Perform system calibration: first perform depth calibration, then perform lateral calibration;

[0092] Preferably, in step 6), the specific steps of depth calibration are as follows:

[0093] S1, placing the dual-mirror calibration plate 11 at the system reference position and parallel to the first display screen 15 and the second display screen 16;

[0094] The first CCD camera 5 captures the double-mirror calibration plate A surface 1, extracts the pixel coordinates of the center of each circle in the circle array 3, and the center of the circle is in the coordinate system O A -X A YA Z A The coordinates in the coordinate system O are obtained by the known distance r between the centers of the circular array 3, and then the conversion relationship between the world coordinates and the pixel coordinates is calculated to obtain the coordinate system O when the double mirror calibration plate 11 is located at the system reference position. A -X A Y A Z A The coordinate system conversion relationship between the first CCD camera 5 and R Af ,T Af ];

[0095] The second CCD camera 6 captures the double-mirror calibration plate B surface 2, extracts the pixel coordinates of the center of each circle in the circle array 3, and the center of the circle is in the coordinate system O A -X A Y A Z A The coordinates in the coordinate system O are obtained by the known distance r between the centers of the circular array 3, and then the conversion relationship between the world coordinates and the pixel coordinates is calculated to obtain the coordinate system O when the double mirror calibration plate 11 is located at the system reference position. B -X B Y B Z B The conversion relationship between the coordinate system of the second CCD camera 6 and R Bf ,T Bf ];

[0096] S2, the computer 4 generates a circular ring array 3 with a known radius and a known distance between the centers of two adjacent circular rings in the row and column directions;

[0097] The generated circular array 3 is displayed on the first display screen 15 located at the initial position 7 of the first display screen. The circular array 3 displayed on the first display screen 15 is reflected by the double-mirror calibration plate A surface 1, and the circular array 3 imaged on the double-mirror calibration plate A surface 1 is photographed by the first CCD camera 5. At this time, the image contains the circular array 3 displayed on the first display screen 15 and the circular array 3 imaged on the double-mirror calibration plate A surface 1. The circular array 3 displayed on the first display screen 15 is screened out, and the pixel coordinates of the center of each circle in the circular array 3 are extracted. The coordinates of the center of the circle are known in the coordinate system of the first display screen 15. Through the conversion relationship between the world coordinates and the pixel coordinates, the conversion relationship between the coordinate system of the first display screen 15 and the coordinate system of the first CCD camera 5 is calculated [R A ,T A ];

[0098] The generated circular array 3 is displayed on the second display screen 16 located at the initial position 8 of the second display screen. The circular array 3 displayed on the second display screen 16 is reflected by the double-mirror calibration plate B surface 2, and the circular array 3 imaged on the double-mirror calibration plate B surface 2 is photographed by the second CCD camera 6. At this time, the image contains the circular array 3 displayed on the second display screen 16 and the circular array 3 imaged on the double-mirror calibration plate B surface 2. The circular array 3 displayed on the second display screen 16 is screened out, and the pixel coordinates of the center of each circle in the circular array 3 are extracted. The coordinates of the center of the circle in the coordinate system of the second display screen 16 are known. Through the conversion relationship between the world coordinates and the pixel coordinates, the conversion relationship between the coordinate system of the second display screen 16 and the coordinate system of the second CCD camera 6 is calculated [R B ,T B ];

[0099] S3. According to formula (8), calculate the distance d between the initial position 7 of the first display screen and the double mirror calibration plate A surface 1 when it is located at the system reference position: A According to formula (9), calculate the distance d between the initial position 8 of the second display screen and the double mirror calibration plate B surface 2 when it is located at the system reference position B :

[0100] d A =R Af -1 (T Af -T A ) (8)

[0101] d B =R Bf -1 (T Bf -T B ) (9)

[0102] The first display screen 15 located at the first display screen initial position 7 is moved a distance to the first display screen moving position 9 by the first high-precision horizontal moving guide rail 12. The first display screen 15 is always located within the depth of field of the first CCD camera 5. The distance Δd between the first display screen initial position 7 and the first display screen moving position 9 is A Obtained by a first high-precision horizontal moving guide rail 12;

[0103] The second display screen 16 located at the second display screen initial position 8 is moved a distance to the second display screen moving position 10 by the second high-precision horizontal moving guide rail 13. The second display screen 16 is always located within the depth of field of the second CCD camera 6. The distance Δd between the second display screen initial position 8 and the second display screen moving position 10 is B This is achieved by the second high-precision horizontal motion guide rail 13 .

[0104] Preferably, in step 6), the conversion relationship between the world coordinates and the pixel coordinates is as shown in formula (10):

[0105]

[0106] In formula (10), Z c is the coordinate in the camera coordinate system, (u,v,1) is the coordinate in the pixel coordinate system, (X W ,Y W ,Z W ) is the coordinate in the world coordinate system, and A is the camera intrinsic parameter matrix.

[0107] Preferably, in step 6), the lateral calibration is specifically:

[0108] After the depth calibration is completed, the A-side subsystem obtains the phase of the measured mirror reflection fringe in the coordinate system O A -X A Y A Z A The depth Z1 (i.e., the distance h1 between the measured position and the double mirror calibration plate A surface 1 when it is located at the system reference position) coordinates are obtained by the B-side subsystem according to the phase of the measured mirror reflection fringe in the coordinate system O B -X B Y B Z B Then, the double-mirror calibration plate 11 is moved n positions (n>6) along the third high-precision horizontal moving guide rail 14 within the common depth of field range of the first CCD camera 5 and the second CCD camera 6, and the depth Z2 of the double-mirror calibration plate surface 1 in the coordinate system O is recorded. A -X A Y A Z A The depth Z1 coordinate under the double mirror calibration plate B surface 2 in the coordinate system O B -X B Y B Z B The first CCD camera 5 and the second CCD camera 6 at each position collect the circular array 3 respectively; according to the pixel coordinates and the depth Z1 coordinates of the center of the circular ring in the circular array 3 extracted by the first CCD camera 5, the coefficients (a0, a1, a2, b0, b1, b2) of the relationship between the pixel coordinates and the horizontal coordinate XY are solved by formula (11): A , complete the XY direction coordinate calibration of the A side subsystem, i.e., the lateral calibration; according to the pixel coordinates and depth Z2 coordinates of the center of the ring in the ring array 3 extracted by the second CCD camera 6, the coefficients (a0, a1, a2, b0, b1, b2) of the relationship between the pixel coordinates and the lateral coordinates XY are solved by formula (11): B, complete the XY coordinate calibration of the B-side subsystem, i.e., lateral calibration;

[0109]

[0110] In formula (11), a0, a1, a2, b0, 1b, and b2 represent the coefficients of the relationship, including the coefficients of the relationship of the subsystem on the A side (a0, a1, a2, b0, b1, and b2) A The relationship coefficients of the B-side subsystem (a0, a1, a2, b0, b1, b2) B ; Z represents depth, including the depth Z1 of the A-side subsystem and the depth Z2 of the B-side subsystem.

[0111] Example

[0112] In this embodiment, the double mirror calibration plate 11 is selected as a cuboid of 215mm×160mm×6mm, and the double mirror calibration plate A surface 1 and the double mirror calibration plate B surface 2 are both provided with the same circular ring array 3; the circular ring array 3 is composed of 9 rows and 12 columns of the same circular rings; the outer circle radius of the circular ring is 2.5mm, the inner circle radius is 2mm, and the center distance r=15mm. The number of sinusoidal fringes generated by the computer 4 is 36, 35, and 30.

[0113] The calibration method of the common reference dual-mirror phase deflection measurement system based on the dual-mirror calibration plate 11 comprises the following steps:

[0114] In step 3), the computer 4 is installed with software for generating fringe images and image processing (MATLAB software in this embodiment), as well as software for controlling the camera to collect and store images. These software are well-known technologies and can be commercially obtained.

[0115] The first CCD camera 5 and the second CCD camera 6 are both black-and-white industrial area array cameras produced by Daheng Image, model MER2-501-79U3M, with a resolution of 2448×2048 and a pixel size of 3.45μm×3.45μm.

[0116] The first display screen 15 and the second display screen 16 both adopt Zhixianda G1316, with a resolution of 1920×1080 and a single pixel physical size of 153.16μm×153.70μm.

[0117] The first high-precision horizontal moving guide rail 12, the second high-precision horizontal moving guide rail 13, and the third high-precision horizontal moving guide rail 14 are all GCD203300M produced by Daheng Optoelectronics Company, with a total stroke of 300mm, a single pulse resolution of 0.001mm, and a repeated positioning error of no more than 0.005mm.

[0118] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A double mirror calibration plate, characterized in that: The double-mirror calibration plate (11) is composed of a double-mirror calibration plate surface A (1), a double-mirror calibration plate surface B (2) and a substrate; A mirror calibration plate surface A (1) and a double mirror calibration plate surface B (2) are respectively arranged on two surfaces of a substrate; the double mirror calibration plate surface A (1) and the double mirror calibration plate surface B (2) are in a parallel relationship and the normal angles are both 180°; the double mirror calibration plate surface A (1) and the double mirror calibration plate surface B (2) are both provided with the same circular ring array (3), and the circular ring array (3) is mirror-symmetrical with respect to the substrate; the circular ring array (3) is composed of the same circular rings distributed in rows and columns; along the row direction and the column direction, the distance between the centers of two adjacent circular rings is the same.

2. The method according to claim 1, characterized in that: The circular ring array (3) is centrally arranged on the double-mirror calibration plate surface A (1) and the double-mirror calibration plate surface B (2).

3. A calibration method for a common reference dual-mirror phase deflection measurement system based on the dual-mirror calibration plate according to claim 1 or 2, characterized in that: The calibration method includes the following steps: 1) Design of double mirror calibration plate (11): With the center of the lower left corner of the circular ring array (3) of the double mirror calibration plate A surface (1) as the origin, a coordinate system O is established with the double mirror calibration plate A surface (1) as the reference plane. A -X A Y A Z A ; The ring array (3) is p columns × q rows; along the row direction and the column direction, the distance between the centers of two adjacent rings is r; then the center of the ring on the A surface (1) of the double mirror calibration plate is in the coordinate system O A -X A Y A Z A The coordinates in are ((p-1)r,(q-1)r,0); With the center of the lower left corner of the circular ring array (3) of the double mirror calibration plate B surface (2) as the origin, a coordinate system O is established with the double mirror calibration plate B surface (2) as the reference plane. B -X B Y B Z B ; The ring array (3) is p columns × q rows; along the row direction and the column direction, the distance between the centers of two adjacent rings is r; then the center of the ring on the B surface (2) of the double mirror calibration plate is in the coordinate system O B -X B Y B Z B The coordinates in are ((p-1)r,(q-1)r,0); The distance between the double mirror calibration plate A surface (1) and the double mirror calibration plate B surface (2) is D; 2) Calibrate the internal parameters of the camera; 3) Build a common reference dual-mirror phase deflection measurement system: The system comprises a double-mirror calibration plate (11), a computer (4), a first CCD camera (5), a second CCD camera (6), a first high-precision horizontal moving guide rail (12), a second high-precision horizontal moving guide rail (13), a third high-precision horizontal moving guide rail (14), a first display screen (15) and a second display screen (16); The first high-precision horizontal moving guide rail (12) is fixed on the optical platform; the first display screen (15) is slidably mounted on the first high-precision horizontal moving guide rail (12), is perpendicular to the optical platform and is parallel to the A surface (1) of the double-mirror calibration plate, and can be linearly moved along the first high-precision horizontal moving guide rail (12) to the first display screen initial position (7) and the first display screen moving position (9); The second high-precision horizontal moving guide rail (13) is fixed on the optical platform; the second display screen (16) is slidably mounted on the second high-precision horizontal moving guide rail (13), is perpendicular to the optical platform and is parallel to the double-mirror calibration plate B surface (2), and can be linearly moved along the second high-precision horizontal moving guide rail (13) to the second display screen initial position (8) and the second display screen moving position (10); The third high-precision horizontal moving guide rail (14) is fixed on the optical platform, the double-mirror calibration plate (11) is placed on the third high-precision horizontal moving guide rail (14), the double-mirror calibration plate (11) is perpendicular to the optical platform and can move linearly along the third high-precision horizontal moving guide rail (14); the first CCD camera (5) is located on one side of the double-mirror calibration plate surface A (1), and the first CCD camera (5), the first display screen (15) and the double-mirror calibration plate surface A (1) are in a triangular measurement relationship in space; the second CCD camera (6) is located on one side of the double-mirror calibration plate surface B (2), and the second CCD camera (6), the second display screen (16) and the double-mirror calibration plate surface B (2) are in a triangular measurement relationship in space; The computer (4), the first CCD camera (5), the first high-precision horizontal moving guide rail (12), the first display screen (15) and the double-mirror calibration plate surface A (1) constitute the A-side subsystem; the computer (4), the second CCD camera (6), the second high-precision horizontal moving guide rail (13), the second display screen (16) and the double-mirror calibration plate surface B (2) constitute the B-side subsystem; The computer (4) is respectively connected to the first display screen (15), the second display screen (16), the first CCD camera (5), the second CCD camera (6), the first high-precision horizontal moving guide rail (12), the second high-precision horizontal moving guide rail (13) and the third high-precision horizontal moving guide rail (14); 4) Common reference calibration of the system: In order to realize the common reference calibration of the A-side subsystem and the B-side subsystem, the coordinate system O A -X A Y A Z A and coordinate system O B -X B Y B Z B The conversion relationship is derived: Assume coordinate system O B -X B Y B Z B To coordinate system O A -X A Y A Z A The rotation matrix is The translation vector is The transformation matrix is In coordinate system O A -X A Y A Z A Assume that a feature point P on the B surface (2) of the double-mirror calibration plate is in the coordinate system O B -X B Y B Z B The coordinates below are In the coordinate system O A -X A Y A Z A The coordinates below are Then we have: In formula (1), the transformation matrix 5) Obtain the system parameters that need to be calibrated: For the A-side subsystem, the distance between the first display screen initial position (7) and the first display screen shift position (9) is Δd A , the distance between the initial position (7) of the first display screen and the double mirror calibration plate A surface (1) when it is located at the system reference position is d A , the coefficients of the relationship of the A-side subsystem obtained by lateral calibration are (a0, a1, a2, b0, b1, b2) A ; For the B-side subsystem, the distance between the second display screen initial position (8) and the second display screen moving position (10) is Δd B , the distance between the initial position (8) of the second display screen and the double mirror calibration plate B surface (2) when it is located at the system reference position is d B , the coefficients of the relationship of the B-side subsystem obtained by lateral calibration are (a0, a1, a2, b0, b1, b2) B ; 6) Perform system calibration: first perform depth calibration, then perform lateral calibration.

4. The calibration method of the common reference dual-mirror phase deflection measurement system according to claim 3, characterized in that: Step 2) specifically comprises: fixing the first CCD camera (5) on an optical platform, selecting a plurality of camera calibration positions within the depth of field of the first CCD camera (5), placing a camera calibration plate in different postures at each camera calibration position, collecting the camera calibration plate image at each camera calibration position by the first CCD camera (5), extracting the pixel coordinates of the corner points of the camera calibration plate, the distance between the corner points being known, and using the Zhang Zhengyou camera calibration method to determine the internal parameters of the first CCD camera (5) to correct the fringe image distortion; The same method is used to determine the internal parameters of the second CCD camera (6) to correct the fringe image distortion.

5. The calibration method of the common reference dual-mirror phase deflection measurement system according to claim 4, characterized in that: In step 2), the camera calibration plate uses a checkerboard calibration plate.

6. The calibration method of the common reference dual-mirror phase deflection measurement system according to claim 3, characterized in that: In step 4), the transformation matrix The calculation method includes the following steps: 4.1) The double mirror calibration plate A surface (1) is used as the reference plane coordinate system and is denoted as boardA. The double mirror calibration plate B surface (2) is used as the reference plane coordinate system and is denoted as boardB. The first CCD camera (5) coordinate system is denoted as camera1. The second CCD camera (6) coordinate system is denoted as camera2. The conversion relationship from coordinate system boardB to coordinate system boardA is: The conversion relationship from coordinate system camera1 to coordinate system camera2 is: The conversion relationship from coordinate system boardB to coordinate system camera2 is: The conversion relationship from coordinate system boardA to coordinate system camera1 is: The relative positions of the double mirror calibration plate surface A (1) and the double mirror calibration plate surface B (2) remain unchanged, and the positions of the first CCD camera (5) and the second CCD camera (6) remain fixed, ensuring that the double mirror calibration plate surface A (1) is within the depth of field of the first CCD camera (5) and the double mirror calibration plate surface B (2) is within the depth of field of the second CCD camera (6). The double mirror calibration plate (11) is transformed into n different postures, n>3, and the first CCD camera (5) and the second CCD camera (6) shoot a group of surface texture images for each posture of the double mirror calibration plate (11), each group consists of two surface texture images, one for each CCD camera, and a circular ring array (3) of the surface texture images is extracted. The conversion matrix of the double mirror calibration plate surface A (1) and the double mirror calibration plate surface B (2) relative to the first CCD camera (5) and the second CCD camera (6) in each posture of the double mirror calibration plate (11) is calculated; for each surface texture image in each group, there is: In formula (2), Directly solving the surface texture image of the double-mirror calibration plate A surface (1) photographed by the first CCD camera (5); Directly solving the surface texture map of the double-mirror calibration plate surface B (2) photographed by the second CCD camera (6); is an unknown quantity, but since there is no relative motion between the first CCD camera (5) and the second CCD camera (6), for each set of surface texture images, are the same; Formula (2) is transformed to obtain: M1 represents the first pose of the double mirror calibration plate (11), and M2 represents the second pose of the double mirror calibration plate (11). From formula (3), we can get: Multiply both sides of equation (4) by And multiply right get: For all n sets of surface texture images corresponding to n different postures collected, n-1 equations are obtained: For equation (5), Then we get: A×X=X×B (7) 4.2) Since A and B in A×X=X×B can be obtained through camera calibration, the problem of solving X is transformed into the problem of solving the hand-eye calibration equation AX=XB. The rotation matrix is ​​obtained using the two-step method with translation vector The transformation matrix can be obtained 7. The calibration method of the common reference dual-mirror phase deflection measurement system according to claim 3, characterized in that: In step 6), the specific steps of depth calibration are as follows: S1, placing the double-mirror calibration plate (11) at a system reference position and parallel to the first display screen (15) and the second display screen (16); The first CCD camera (5) photographs the double-mirror calibration plate A surface (1), extracts the pixel coordinates of the center of each circle in the circle array (3), and the center of the circle is in the coordinate system O A -X A Y A Z A The coordinates in are obtained by the known distance r between the centers of the circular array (3), and then the coordinate system O is calculated when the double mirror calibration plate (11) is located at the system reference position through the conversion relationship between the world coordinates and the pixel coordinates. A -X A Y A Z A The conversion relationship between the coordinate system of the first CCD camera (5) and Af ,T Af ]; The second CCD camera (6) photographs the double-mirror calibration plate B surface (2) and extracts the pixel coordinates of the center of each circle in the circle array (3). A -X A Y A Z A The coordinates in are obtained by the known distance r between the centers of the circular array (3), and then the coordinate system O is calculated when the double mirror calibration plate (11) is located at the system reference position through the conversion relationship between the world coordinates and the pixel coordinates. B -X B Y B Z B The conversion relationship between the coordinate system of the second CCD camera (6) and Bf ,T Bf ]; S2, a computer (4) generates a circular ring array (3) with a known radius and a known distance between the centers of two adjacent circular rings in the row and column directions; The generated circular ring array (3) is displayed on a first display screen (15) located at an initial position (7) of the first display screen. The circular ring array (3) displayed on the first display screen (15) is reflected by the double-mirror calibration plate A surface (1), and the circular ring array (3) imaged on the double-mirror calibration plate A surface (1) is photographed by the first CCD camera (5). At this time, the image contains the circular ring array (3) displayed on the first display screen (15) and the circular ring array (3) imaged on the double-mirror calibration plate A surface (1). The circular ring array (3) displayed on the first display screen (15) is selected, and the pixel coordinates of the center of each circle in the circular ring array (3) are extracted. The coordinates of the center of the circle in the coordinate system of the first display screen (15) are known. The conversion relationship between the coordinate system of the first display screen (15) and the coordinate system of the first CCD camera (5) is calculated through the conversion relationship between the world coordinate and the pixel coordinate. A ,T A ]; The generated circular ring array (3) is displayed on a second display screen (16) located at an initial position (8) of the second display screen. The circular ring array (3) displayed on the second display screen (16) is reflected by the double-mirror calibration plate B surface (2). The circular ring array (3) imaged on the double-mirror calibration plate B surface (2) is photographed by a second CCD camera (6). At this time, the image contains the circular ring array (3) displayed on the second display screen (16) and the circular ring array (3) imaged on the double-mirror calibration plate B surface (2). The circular ring array (3) displayed on the second display screen (16) is selected, and the pixel coordinates of the center of each circular ring in the circular ring array (3) are extracted. The coordinates of the center of the circle in the coordinate system of the second display screen (16) are known. The conversion relationship between the coordinate system of the second display screen (16) and the coordinate system of the second CCD camera (6) is calculated through the conversion relationship between the world coordinate and the pixel coordinate. B ,T B ]; S3. According to formula (8), calculate the distance d between the initial position (7) of the first display screen and the double mirror calibration plate A surface (1) when it is located at the system reference position: A According to formula (9), calculate the distance d between the initial position (8) of the second display screen and the double mirror calibration plate B surface (2) when it is located at the system reference position B : d A =R Af -1 (T Af -T A ) (8) d B =R Bf -1 (T Bf -T B ) (9) A first display screen (15) located at a first display screen initial position (7) is moved a distance to a first display screen moving position (9) by using a first high-precision horizontal moving guide rail (12), the first display screen (15) is always located within the depth of field of the first CCD camera (5), and the distance Δd between the first display screen initial position (7) and the first display screen moving position (9) is A Obtained by a first high-precision horizontal moving guide rail (12); A second high-precision horizontal moving guide rail (13) is used to move a second display screen (16) located at a second display screen initial position (8) to a second display screen moving position (10), wherein the second display screen (16) is always located within a depth of field range of a second CCD camera (6), and a distance Δd between the second display screen initial position (8) and the second display screen moving position (10) is B This is achieved by a second high-precision horizontal motion guide rail (13).

8. The calibration method of the common reference dual-mirror phase deflection measurement system according to claim 7, characterized in that: In step 6), the conversion relationship between world coordinates and pixel coordinates is shown in formula (10): In formula (10), Z c is the coordinate in the camera coordinate system, (u,v,1) is the coordinate in the pixel coordinate system, (X W ,Y W ,Z W ) is the coordinate in the world coordinate system, and A is the camera intrinsic parameter matrix.

9. The calibration method of the common reference dual-mirror phase deflection measurement system according to claim 3, characterized in that: In step 6), the lateral calibration is specifically: After the depth calibration is completed, the A-side subsystem obtains the phase of the measured mirror reflection fringe in the coordinate system O A -X A Y A Z A The depth Z1 coordinate under the measured mirror reflection fringe phase is obtained by the B-side subsystem in the coordinate system O B -X B Y B Z B Then, the double-mirror calibration plate (11) is moved along the third high-precision horizontal movable guide rail (14) to n positions within the common depth of field of the first CCD camera (5) and the second CCD camera (6), where n>6, and the double-mirror calibration plate A surface (1) is recorded in the coordinate system O A -X A Y A Z A The depth Z1 coordinate under the double mirror calibration plate surface B (2) in the coordinate system O B -X B Y B Z B The first CCD camera (5) and the second CCD camera (6) at each position respectively collect the circular ring array (3); according to the pixel coordinates and the depth Z1 coordinates of the center of the circular ring in the circular ring array (3) extracted by the first CCD camera (5), the coefficients (a0, a1, a2, b0, b1, b2) of the relationship between the pixel coordinates and the horizontal coordinate XY are solved by equation (11) A , complete the lateral calibration of the A side subsystem; according to the pixel coordinates and depth Z2 coordinates of the center of the ring in the ring array (3) extracted by the second CCD camera (6), the coefficients (a0, a1, a2, b0, b1, b2) of the relationship between the pixel coordinates and the lateral coordinates XY are solved by equation (11) B , complete the lateral calibration of the B-side subsystem; In formula (11), a0, a1, a2, b0, b1, and b2 represent the coefficients of the relationship, including the coefficients of the relationship of the subsystem on the A side (a0, a1, a2, b0, b1, and b2) A The relationship coefficients of the B-side subsystem (a0, a1, a2, b0, b1, b2) B ; Z represents depth, including the depth Z1 of the A-side subsystem and the depth Z2 of the B-side subsystem.

Images