CN115994954A - High-precision large-field near infrared optical camera calibration device and calibration method - Google Patents
High-precision large-field near infrared optical camera calibration device and calibration method Download PDFInfo
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Abstract
The invention belongs to the technical field of optical navigation, and discloses a high-precision large-visual-field near-infrared optical camera calibration device and a calibration method. According to the invention, the distance and the angle of the calibration display screen are automatically controlled through the calibration support and the mobile device, the pictures of the calibration objects with different pixel sizes are displayed according to the distance from the optical navigation camera to the calibration display screen, the circle center of the calibration object is marked by adopting the two-dimension code, and the calibration can be accurately identified and performed even if the calibration pictures are not fully acquired.
Description
Technical Field
The invention belongs to the technical field of optical navigation, and particularly relates to a high-precision large-visual-field near-infrared optical camera calibration device and a calibration method.
Background
One navigation mode in the surgical robot field is to use an optical navigation camera for navigation, and the working principle is as follows: the optical positioning system forms a group of binocular vision systems through two near infrared cameras, infrared LEDs are fixed on the peripheries of optical axes of the two cameras for illumination, and infrared light emitted by the infrared LEDs is reflected back into a camera photosensitive chip through a marking ball on the surgical instrument. The image of the marking ball is acquired through the camera, the marking point is identified and positioned through a digital image processing technology under the assistance of a computer, and the coordinate and the direction of the surgical instrument can be calibrated according to the three-dimensional coordinate of the marking point, so that the accurate navigation of the operation is realized.
Before the optical navigation camera is used, camera calibration needs to be carried out, and the working precision of the optical camera is directly affected by the camera calibration precision. In the binocular camera calibration process, small-field camera calibration is common. The small-view calibration has the advantages that the small-view calibration does not need a large calibration plate, and obvious uneven illumination can not occur. In the small-view calibration, people usually only need to hold the calibration plate by hand to shoot a plurality of positions of the calibration picture, and the small-view camera pixel can reach high pixel size resolution in the small-view range, so that the requirement on the marker precision in the calibration plate is greatly reduced. However, in the field of medical robot navigation, the accuracy of any point in the whole operation space needs to be guaranteed, so that the robot needs to be subjected to position navigation in a large range, such as calibration of near infrared light in a large range of length, width, depth 3m 2m 3 m.
In addition, in the process of camera calibration, the pictures of the calibration plates are required to be acquired at the near position and the far position respectively, in the process, as the calibration plates are of fixed sizes, the camera shoots all calibration points of the incomplete marker patterns at the near position, so that the shot calibration points cannot be identified, the markers of the calibration plates shot at the far position are displayed too small, and the extraction precision is reduced.
Secondly, white light interference needs to be eliminated in long-distance shooting, and no good means is available at present for realizing high-precision calibration of near infrared light under a large visual field.
Disclosure of Invention
The invention aims to provide a high-precision large-visual-field near-infrared optical camera calibration device and a calibration method, so as to solve the technical problems.
In order to solve the technical problems, the specific technical scheme of the high-precision large-visual-field near-infrared optical camera calibration device and the calibration method is as follows:
the utility model provides a high accuracy large visual field near infrared optical camera calibration device, includes calibration display screen, calibration support, mobile device and calibration control host computer, the calibration display screen is installed on the calibration support, the calibration support is installed on the mobile device, calibration support, calibration display screen are connected with the calibration control host computer electricity, and optical navigation camera is fixed to be placed at mobile device front end and be in same central line height with the calibration display screen, optical navigation camera is connected with the calibration control host computer electricity, the calibration display screen is used for showing the calibration thing pattern, the calibration support is used for fixing and adjusting the left and right sides and the every single move angle of calibration display screen, mobile device is used for removing the calibration thing pattern of calibration display screen, the calibration control host computer is used for controlling mobile device to remove the calibration display screen in the calibration process, controls the left and right sides and every single move angle of calibration display screen, and the distance according to calibration display screen and optical navigation camera's distance control calibration display screen display different resolution's calibration thing pattern, control optical navigation camera automatic acquisition thing pattern coordinate to calculate reference position according to the calibration thing pattern.
Further, the calibration display screen sequentially comprises a frosted glass layer, an LED liquid crystal display screen layer, a light diffusion film layer, a light guide plate layer, an infrared light-emitting layer, a light reflecting plate layer, a liquid crystal display screen control panel, a radiator and a light reflecting plate rear shell from outside to inside.
Further, the infrared light-emitting layer comprises a near infrared lamp bead strip array and a liquid cooling layer, and the near infrared lamp bead strip array is clung to the liquid cooling layer.
Further, the radiator comprises radiating fins, radiating pipes and a circulating water pump, the radiating pipes are arranged on the radiating fins in a back-and-forth spiral mode, each radiating pipe corresponds to one infrared lamp bead strip, the radiating pipes are provided with the circulating water pump, the circulating water pump circularly conveys cooling liquid in the radiating pipes, and the liquid crystal display control panel is arranged on one side of the radiator and used for controlling the LED liquid crystal display screen layer to display calibration object patterns with different resolutions.
Further, the calibration control host comprises an operation module, a movement control module, a display screen angle control module and a display module, wherein the movement control module is used for controlling the movement device to move the calibration display screen up and down and left and right in the calibration process; the display screen angle control module is used for controlling the left and right and pitching angles of the calibrated display screen; the display module controls the calibration display screen to display the calibration object patterns with different resolutions according to the distance between the calibration display screen and the optical navigation camera; and the operation module calculates the camera reference position according to the calibration object coordinates acquired by the optical navigation camera.
The invention also discloses a calibration method of the calibration device, which comprises the following steps:
step 1: before calibration, an optical navigation camera is placed at the forefront end of a front-back moving sliding rail of a moving device;
step 2: calculating the pixels of the calibration object: the calibration control host calculates the distance from the current optical navigation camera to the calibration display screen according to the position of the current calibration display screen at the sliding rail moving forwards and backwards, and calculates the required pixel diameter of the calibration object pattern according to the distance;
step 3: and (3) generating a calibration pattern: the calibration control host generates calibration object patterns according to the calculated diameter of the calibration object pixels in the step 2, and simultaneously, each calibration object pattern generates a unique coding mark;
step 4: and acquiring a group of calibration object pictures at fixed distance: a front-view calibration object picture is acquired by controlling a front-back moving sliding rail of a moving device to move to a fixed distance through a preset program of a main control module of a calibration control host, 4 pictures of overlooking, upward looking, leftward looking and rightward looking are acquired in total by controlling a calibration display screen through a calibration support, 5 pictures are acquired in each group, the calibration display screen is moved up and down and leftward and rightward according to the visual field range of an optical navigation camera, and full visual field range pictures are acquired;
step 5: and acquiring a plurality of groups of calibration object pictures at different distances: controlling the moving device to control the front-back moving sliding rail to move to different distances, and repeating the steps 3-4;
step 6: the calibration control host inputs the acquired pixel coordinates and world coordinate systems of the calibration object into calibration codes, and internal and external parameters of the optical navigation camera are calculated by utilizing the double-target calibration codes.
Further, the step 2: calculating the required diameter p of the pixel of the calibration object according to the distance from the current optical navigation camera to the calibration display screen, and the formula: p=d×c, the unit is mm, d is the distance from the optical navigation camera to the calibration display screen, and c is the constant coefficient of the conversion of the distance into pixels.
Further, a two-dimensional code is generated in the middle of the calibration object in the step 3, the unique number of the marker, the actual physical size s of the marker and a homogeneous coordinate system (n x s, m x s, 1) on the calibration display screen are recorded in the two-dimensional code information, n is the number of pictures of the calibration plate from left to right, m is the number of pictures from top to bottom, and 1 is a homogeneous coordinate expression mode.
Further, the step 5: and acquiring a plurality of groups of calibration object pictures at different distances: each time the distance is reduced by sin (30 °) which marks the short side of the display screen.
Further, the method for calculating the internal and external parameters in the step 6 is as follows:
(U, V) is the coordinates of the corner points of the calibration plate in the pixel coordinate system, (U, V) is the coordinates of the corner points of the calibration plate in the world coordinate system, the pixel coordinates (U, V) of the corner points of the calibration display screen are obtained through an image recognition algorithm, the world coordinate system of the calibration display screen is defined artificially, the size of each pixel on the calibration display screen is known, the (U, V) in the world coordinate system is obtained through calculation,
the camera calibration model formula can be known:
wherein ,
for affine transformation +.>
For perspective projection the projection is performed in a perspective view,
is an internal reference matrix>
Is rigid body transformation, namely an external parameter matrix;
the camera calibration process is to restrain the product homography H of the following internal reference matrix and external reference matrix through calibrating pixel coordinate points and corresponding world coordinate points which are acquired by mark points on a display screen to solve:
due to scale invariance of homogeneous coordinate system, Z is eliminated, and the following is obtained:
in the calculation process, as the homogeneous coordinates are unchanged, a non-zero coefficient is multiplied to enable H33 to be 1, H is a homogeneous matrix, only 8 independent unknown elements are finally solved, each calibration plate corner point provides two constraint equations, therefore, when the number of the calibration display screen corner points on one picture is equal to 4, a matrix corresponding to the picture is obtained, when the number of the calibration display screen corner points on one picture is greater than 4, the optimal matrix is regressed by using a least square method, and then the constraint relation of the H matrix to the internal reference is used for continuously solving the internal reference K and the external reference transformation matrix T respectively.
The high-precision large-visual-field near-infrared optical camera calibration device and the calibration method have the following advantages: according to the invention, the distance and the angle of the calibration display screen are automatically controlled through the calibration support and the mobile device, and the calibration display screen is controlled to display the calibration object patterns with different pixel sizes according to the distance from the optical navigation camera to the calibration display screen, the calibration object patterns can be clearly collected in the near or far places, the circle center is marked by adopting the two-dimension code, and the calibration can be accurately performed by accurately identifying the calibration object patterns even if the calibration object patterns are not fully collected. The problems of fixed pattern and low precision of the calibration plate in the prior art are solved, and enough brightness is provided for the calibration of the large-field camera.
Drawings
FIG. 1 is a schematic diagram of a calibration device for a high-precision large-field near infrared optical camera;
FIG. 2 is a schematic view of the calibration stand structure of the present invention;
FIG. 3 is a schematic diagram of a calibration display screen according to the present invention;
FIG. 4 is a schematic diagram of an infrared light emitting layer structure according to the present invention;
FIG. 5 is a schematic diagram of a heat sink according to the present invention;
FIG. 6 is a schematic diagram of a two-dimensional code at the center of a calibration object displayed by a calibration display screen;
the figure indicates: 1. calibrating a display screen; 11. a frosted glass layer; 12. an LED liquid crystal display screen layer; 13. a light diffusion film layer; 14. a light guide plate layer; 15. an infrared light emitting layer; 151. an array of infrared light bead strips; 152. a liquid cooling layer; 16. a light reflecting plate layer; 17. a liquid crystal screen control board; 18. a heat sink; 181. a heat sink; 182. a heat radiating pipe; 183. a circulating water pump; 19. a rear housing of the reflector; 2. calibrating a bracket; 21. fixing the main shaft; 22. a rotating shaft; 221. a side arm; 23. A rotating electric machine; 24. an electric push rod; 3. a mobile device; 31. moving the slide rail back and forth; 32. moving the slide rail left and right; 33. moving the slide rail up and down; 4. calibrating a control host; 5. an optical navigation camera.
Detailed Description
In order to better understand the purpose, structure and function of the present invention, the present invention provides a calibration device and a calibration method for a high-precision large-field near infrared optical camera, which are described in further detail below with reference to the accompanying drawings.
As shown in fig. 1, the high-precision large-view near infrared optical camera calibration device comprises a calibration display screen 1, a calibration support 2, a mobile device 3 and a calibration control host 4, wherein the calibration display screen 1 is arranged on the calibration support 2, the calibration support 2 is arranged on the mobile device 3, and the mobile device 3, the calibration support 2 and the calibration display screen 1 are electrically connected with the calibration control host 4. The optical navigation camera 5 is fixedly arranged at the front end of the mobile device 3 and is positioned at the same central line height with the calibration display screen 1, and the optical navigation camera 5 is electrically connected with the calibration control host 4. The optical navigation camera 5 is used for acquiring calibration object patterns on the calibration display screen 1, the calibration control host 4 is used for controlling the mobile device 3 to move the calibration display screen 1 in the calibration process, controlling the calibration support 2 to adjust the left and right and pitching angles of the calibration display screen 1, controlling the calibration display screen to display the calibration object patterns with different resolutions according to the distance between the calibration display screen 1 and the optical navigation camera 5, controlling the optical navigation camera 5 to automatically acquire the calibration object coordinates, and calculating the camera reference position according to the acquired calibration object coordinates.
The moving device 3 can adopt any mechanical structure with the function of moving up and down, back and forth, left and right and up and down in the prior art, and is used for driving the calibration display screen fixed on the moving device to move up and down, back and forth, left and right and up and down, so as to collect the coordinates of the calibration objects at different positions. As shown in fig. 1, the moving device 3 in the embodiment of the present invention includes two front-back moving rails 31, a left-right moving rail 32 and a up-down moving rail 33, where the two front-back moving rails 31 are placed in parallel, the left-right moving rail 32 is disposed across the front-back moving rail 31, the up-down moving rail 33 is vertically disposed on the left-right moving rail 32, the calibration support 2 is disposed on the up-down moving rail 31, the calibration display screen 1 is fixedly disposed on the calibration support 2, the front-back moving rail 31 has a front-back moving motor for controlling the left-right moving rail 32 to move along the front-back direction, the left-right moving rail 32 has a left-right moving motor for controlling the left-right moving rail 33 to move up-down, and the up-down moving rail 33 has a up-down moving motor for controlling the up-down moving of the calibration support 2. The front-back moving motor, the left-right moving motor and the up-down moving motor are all electrically connected with the calibration control host. The external world supplies power to the calibration control host 4 through a power line. The calibration control host 4 controls the calibration display screen 1 to move in xyz three directions by controlling the operation of the front-back moving motor, the left-right moving motor and the up-down moving motor.
The calibration support 2 may adopt any structure with fixed and controlled pitching and left and right rotation angles in the prior art, as shown in fig. 2, the calibration support 2 in the embodiment of the invention comprises a fixed main shaft 21, a rotating shaft 22, a rotating motor 23 and an electric push rod 24, wherein the fixed main shaft 21 is in sliding connection with an up-down moving slide rail 33 through a sliding piece, the rotating motor 23 is arranged in the fixed main shaft 21, an output shaft of the rotating motor is fixedly connected with the rotating shaft 22, the rotating motor 23 is used for controlling the left and right rotation angles of the rotating shaft 22, one side of the rotating shaft 22 is connected with a back shaft of the calibration display screen 1 through a side arm 221 extending out, one end of the electric push rod 24 is connected with an upper end shaft of the rotating shaft 22, the other end of the electric push rod 24 is connected with a back shaft of the calibration display screen 1, the rotating motor 23 and the electric push rod 24 are electrically connected with the calibration control host 4, and the calibration control host 4 controls work.
As shown in fig. 3, the calibration display screen 1 of the present invention includes, in order from the outside to the inside, a frosted glass layer 11, an LED liquid crystal display screen layer 12, a light diffusion film layer 13, a light guide plate layer 14, an infrared light emitting layer 15, a light reflecting plate layer 16, a liquid crystal display screen control board 17, a heat sink 18, and a light reflecting plate rear housing 19. The frosted glass layer 11 is arranged on the surface of the calibration display screen 1 and is used for avoiding mirror reflection when the camera collects pictures. The LED lcd layer 12 is a 4K high definition, preferably 92cm by 52cm, which is a preferred size selected based on the cost of the display and the pixels required for calibration, and is not limiting of the invention. To increase the black-and-white contrast, this can be achieved by superimposing a plurality of LED liquid crystal display layers 12. The plurality of light diffusion film layers 13 serve to make the light irradiated from the rear uniform. The light guide plate layer 14 allows the vertically irradiated light to pass therethrough, enhancing light efficiency. As shown in fig. 4, the infrared light emitting layer 15 includes a near infrared bead strip array 151 and a liquid cooling layer 152, where the near infrared bead strip array 151 is composed of near infrared beads LEDs, the near infrared bead strip array 151 is attached to the liquid cooling layer 152, preferably, the wavelength of the near infrared beads LEDs is in the range of 800nm to 900nm, and the interval between each infrared bead LED is 20 x 20mm, and total 46 x 31=1426 beads. The reflector layer 16 is configured to reflect non-perpendicularly passing infrared light back to the light guide layer 16. Because the number of the infrared lamp beads LED is large, the liquid cooling layer 152 can not meet the heat dissipation requirement, therefore, the radiator 18 is added behind the infrared luminous layer 15, as shown in fig. 5, the radiator 18 comprises the radiating fins 181, the radiating pipes 182 and the circulating water pump 183, the radiating fins 181 are made of aluminum alloy, the radiating pipes 182 are spirally arranged on the radiating fins 181 back and forth, each radiating pipe 182 corresponds to one infrared lamp bead strip, the circulating water pump 183 is arranged on the radiating pipe 182, and the cooling liquid is circularly conveyed in the radiating pipe 182 through the circulating water pump 183. The liquid crystal screen control board 17 is arranged on one side of the radiator 18 and is used for controlling the LED liquid crystal display screen layer 12 to display the calibration object patterns with different resolutions. The reflector rear housing 19 is used to secure all of the above layers.
The calibration control host 4 comprises an operation module, a movement control module, a display screen angle control module and a display module. The mobile control module is used for controlling the mobile device 3 to move the calibration display screen 1 up and down and left and right in the calibration process; the display screen angle control module is used for controlling the left and right and pitching angles of the calibrated display screen 1; the display module is electrically connected with the liquid crystal screen control board 17, and the calibration display screen 1 is controlled to display the calibration object patterns with different resolutions according to the distance between the calibration display screen 1 and the optical navigation camera 5; the operation module calculates a camera reference position according to the coordinates of the calibration object acquired by the optical navigation camera.
The calibration method of the invention comprises the following steps:
step 1: before calibration, the optical navigation camera 5 is placed at the forefront end of the front-back moving sliding rail 31 of the moving device 3;
step 2: calculating the pixels of the calibration object: the calibration control host 4 calculates the distance from the current optical navigation camera 5 to the calibration display screen 1 according to the position of the current calibration display screen 1 moving the sliding rail 31 forwards and backwards, calculates the required calibration object pixel diameter p according to the distance, and adopts the formula: in this embodiment, c is 0.05, p is the size of a marker pixel, for example, the initial distance is 3m, the diameter of the pixel of the calibration object is collected to be 150 pixels, the actual physical size formula of the calibration object is s=p×r (p is the size of the pixel of the calibration object, r is the actual size of a single pixel of the LED liquid crystal display screen layer 12), the length of the calibration display screen 1 in this embodiment is 92cm, and the pixels in the direction are 3820 pixels, so the calculated pixel size is 0.24mm;
step 3: generating a calibration picture: the calibration control host 4 generates a calibration picture according to the pixel diameter of the calibration object calculated in the step 2, generates a calibration object containing unique codes, generates a two-dimensional code with the size of 100 x 100 pixels in the middle of the calibration object, records the unique number of the calibration object, the actual physical size s of the marker and a homogeneous coordinate system (n x s, m x s, 1) on the calibration display screen 1, wherein n is the number of the calibration plate picture from left to right, m is the number of the calibration plate picture from top to bottom, and 1 is a homogeneous coordinate expression mode. As shown in fig. 6, the calibration object in this embodiment is a circular graphic array, the calculation accuracy of the circular calibration object is highest, the circle center position can be accurately calculated, the size of the circle and the distance between the circles are calculated according to the distance from the optical navigation camera 5 to the calibration display screen 1, so that the camera can acquire the circle center with enough proper size and high accuracy at a far distance, and can acquire the circle center with proper size at a near position, and the optical navigation camera 5 cannot shoot the whole calibration display screen 1 due to the reduced field of view, but can know which circle center corresponds even if the generated picture has unique code.
Step 4: and acquiring a group of calibration object pictures at fixed distance: through the procedure preset by the main control module of the calibration control host 4, the front and back moving slide rail 31 of the moving device 3 is controlled to move to the position of 3 meters (the initial distance from the optical navigation camera 5 to the calibration display screen 1), then a front view calibration picture is collected, and then the electric push rod 24 and the rotating motor 23 of the calibration support 2 are used for controlling the calibration display screen 1 to perform pitching rotation and left and right swinging (the pitching and left and right swinging angles are 30 degrees, because the calibration process needs to perform calibration display screen pose rotation, the rotation amount of 30 degrees is the optimal identification angle, the industry calibration experience can ensure that the calibration plate collects the circle center or circle, and because of non-front view, the plane circle can become elliptical under the camera view angle, enough gesture conversion accords with the requirements of Zhang Zhengyou calibration method), 4 pictures of looking down, 5 pictures are collected in each group, and because the optical navigation camera module at the position of 3m has the length and the width of 3m, the required length and the width of 1m of the calibration plate are 1m, the right and left and right moving slide rail 32 need to be controlled to perform up and down movement, and the optical navigation data can be collected at the position of 3m, and the position of 3 is equal to the position of 9m, and the position of the optical navigation data can be collected at the position of the slide rail is required to be equal to 9.
Step 5: and acquiring a plurality of groups of calibration object pictures at different distances: the moving device 3 controls the front-back moving sliding rail 31 to move to 2.70m, 2.40m, 2.10m, 1.80m, 1.50m, 120m and 0.9m (after that, the binocular common view of the optical navigation camera is not used, and therefore the pictures are not required to be acquired), and the steps 3-4 are repeated, namely, each time the distance is reduced by 0.3m (sin (30 degrees) of the short side of the calibration display screen), so that the high-precision near infrared light large-view calibration device performs an automatic calibration flow in a special calibration room, 9 groups are required to be acquired before 2.40m because the common view is mostly, the 2.10m to 1.50m of the common view is reduced, only 4 groups are required to be smaller, and only 1 group is required to be smaller than 1.20m to be required to be smaller than 1 group, and thus (45 x 3+20 x 3+5 x 2) calibration pictures are acquired in total. Thus, the damage of high-power near infrared light to human eyes is avoided.
Step 6: the calibration control host 4 inputs the acquired pixel coordinates and world coordinate systems of the calibration object into the calibration codes, and performs internal and external parameter calculation of the optical navigation camera by using common opencv double-target calibration codes, so that good calibration accuracy can be achieved through testing.
(U, V) is the coordinates of the corner points of the calibration plate in the pixel coordinate system, and (U, V) is the coordinates of the corner points of the calibration plate in the world coordinate system. Through an image recognition algorithm, pixel coordinates (U, V) of the corner points of the calibration display screen can be obtained, and as the world coordinate system of the calibration display screen is defined artificially, the size of each pixel on the calibration display screen is known, and the (U, V) under the world coordinate system can be obtained through calculation.
The camera calibration model formula can be known:
wherein ,
for affine transformation +.>
For perspective projection the projection is performed in a perspective view,
is an internal reference matrix>
Is a rigid body transformation, namely an extrinsic matrix.
The camera calibration process is mainly to restrain the product homography H of the following internal reference matrix and external reference matrix through calibrating pixel coordinate points and corresponding world coordinate points which are acquired by mark points on a display screen to solve:
due to scale invariance of homogeneous coordinate system, Z is eliminated, and the following is obtained:
in the calculation process, due to invariance of homogeneous coordinates, H33 is 1 by multiplying a non-zero coefficient by default, wherein H is a homogeneous matrix, and finally only 8 independent unknown elements need to be solved. Each calibration plate corner point can provide two constraint equations, so that when the number of the calibration display screen corner points on one picture is equal to 4, a matrix corresponding to the picture can be obtained. When the number of the corner points of the calibrated display screen on one picture is larger than 4, the optimal matrix is regressed by using a least square method. And then, the constraint relation of the H matrix on the internal parameters is utilized to respectively solve the internal parameter K and the external parameter transformation matrix T.
It will be understood that the invention has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. The utility model provides a high accuracy large visual field near infrared optical camera calibration device, its characterized in that includes calibration display screen (1), calibration support (2), mobile device (3) and calibration control host computer (4), calibration display screen (1) are installed on calibration support (2), calibration support (2) are installed on mobile device (3), calibration support (2), calibration display screen (1) are connected with calibration control host computer (4) electricity, optical navigation camera (5) are fixed to be placed in mobile device (3) front end and be in same central line height with calibration display screen (1), optical navigation camera (5) are connected with calibration control host computer (4) electricity, calibration display screen (1) are used for showing the calibration thing pattern, calibration support (2) are used for fixing and adjusting the left and right sides and the pitch angle of calibration display screen (1), mobile device (3) are used for moving calibration display screen (1), optical navigation camera (5) are used for gathering the calibration thing pattern on the calibration display screen (1), calibration control host computer (4) are used for carrying out the adjustment in mobile device (3) and control the pitch angle of calibration display screen (1) in the process of moving left and right side (1), and controlling the calibration display screen to display the calibration object patterns with different resolutions according to the distance between the calibration display screen (1) and the optical navigation camera (5), controlling the optical navigation camera (5) to automatically acquire the coordinates of the calibration object patterns, and calculating the reference position of the camera according to the acquired coordinates of the calibration object patterns.
2. The high-precision large-view-field near infrared optical camera calibration device according to claim 1, wherein the calibration display screen (1) sequentially comprises a frosted glass layer (11), an LED liquid crystal display screen layer (12), a light diffusion film layer (13), a light guide plate layer (14), an infrared light emitting layer (15), a reflecting plate layer (16), a liquid crystal screen control panel (17), a radiator (18) and a reflecting plate rear shell (19) from outside to inside.
3. The high-precision large-field near infrared optical camera calibration device according to claim 2, wherein the infrared light emitting layer (15) comprises a near infrared lamp bead strip array (151) and a liquid cooling layer (152), and the near infrared lamp bead strip array (151) is closely attached to the liquid cooling layer (152).
4. The high-precision large-field near infrared optical camera calibration device according to claim 3, wherein the radiator (18) comprises radiating fins (181), radiating pipes (182) and a circulating water pump (183), the radiating pipes (182) are arranged on the radiating fins (181) in a back-and-forth spiral mode, each radiating pipe (182) corresponds to one infrared lamp bead strip, the circulating water pump (183) is arranged on each radiating pipe (182), the circulating water pump (183) circularly conveys cooling liquid in the radiating pipe (182), and the liquid crystal screen control board (17) is arranged on one side of the radiator (18) and is used for controlling the LED liquid crystal display screen layer (12) to display calibration object patterns with different resolutions.
5. The high-precision large-field near infrared optical camera calibration device according to claim 1, wherein the calibration control host (4) comprises an operation module, a movement control module, a display screen angle control module and a display module, and the movement control module is used for controlling the movement device (3) to move the calibration display screen (1) up and down and left and right in the calibration process; the display screen angle control module is used for controlling the left and right and pitching angles of the calibrated display screen (1); the display module controls the calibration display screen (1) to display the calibration object patterns with different resolutions according to the distance between the calibration display screen (1) and the optical navigation camera (5); and the operation module calculates a camera reference position according to the coordinates of the calibration object acquired by the optical navigation camera (5).
6. A method of calibrating a calibration device according to any of claims 1-5, comprising the steps of:
step 1: before calibration, the optical navigation camera (5) is placed at the forefront end of a front-back moving sliding rail (31) of the mobile device (3);
step 2: calculating the pixels of the calibration object: the calibration control host (4) calculates the distance from the current optical navigation camera (5) to the calibration display screen (1) according to the position of the current calibration display screen at the front-back moving slide rail (31), and calculates the required pixel diameter of the calibration object pattern according to the distance;
step 3: and (3) generating a calibration pattern: the calibration control host (4) generates calibration object patterns according to the calculated diameter of the calibration object pixels in the step (2), and simultaneously, each calibration object pattern generates a unique coding mark;
step 4: and acquiring a group of calibration object pictures at fixed distance: a program preset by a main control module of a calibration control host (4) controls a front-back movement sliding rail (31) of a mobile device (3) to move to a fixed distance to acquire a front-view calibration object picture, then a calibration display screen (1) is controlled by a calibration support (2) to perform pitching rotation and left-right swinging, 4 pictures of overlooking, upward viewing, leftward viewing and rightward viewing are acquired altogether, 5 pictures are acquired altogether in each group, the calibration display screen (1) is moved up, down, leftward and rightward according to the visual field range of an optical navigation camera (5), and full visual field range pictures are acquired;
step 5: and acquiring a plurality of groups of calibration object pictures at different distances: the control moving device (3) controls the front-back moving sliding rail (31) to move to different distances, and the steps 3-4 are repeated;
step 6: the calibration control host (4) inputs the acquired calibration object pixel coordinates and the world coordinate system into a calibration code, and performs internal and external parameter calculation of the optical navigation camera by using the double-target calibration code.
7. The method according to claim 6, wherein the step 2: according to the calculated distance from the current optical navigation camera (5) to the calibrated display screen (1), calculating the required calibrated object pixel diameter p, and the formula: p=d×c, the unit is mm, d is the distance from the optical navigation camera (5) to the calibration display screen (1), and c is the constant coefficient of the conversion of the distance into pixels.
8. The method according to claim 6, wherein a two-dimensional code is generated in the middle of the calibration object in the step 3, the information of the two-dimensional code records the unique number of the marker, the actual physical size s of the marker and the homogeneous coordinate system (n×s, m×s, 1) on the calibration display screen 1, n is the number of pictures of the calibration plate from left to right, m is the number of pictures from top to bottom, and 1 is the homogeneous coordinate expression mode.
9. The calibration method according to claim 6, wherein the step 5: and acquiring a plurality of groups of calibration object pictures at different distances: and (3) reducing the sin (30 degrees) of the short side of the calibration display screen (1) each time.
10. The calibration method according to claim 6, wherein the internal and external parameter calculation method in step 6 is as follows:
(U, V) is the coordinates of the corner points of the calibration plate in the pixel coordinate system, (U, V) is the coordinates of the corner points of the calibration plate in the world coordinate system, the pixel coordinates (U, V) of the corner points of the calibration display screen are obtained through an image recognition algorithm, the world coordinate system of the calibration display screen is defined artificially, the size of each pixel on the calibration display screen is known, the (U, V) in the world coordinate system is obtained through calculation,
the camera calibration model formula can be known:
wherein ,
for affine transformation +.>
For perspective projection the projection is performed in a perspective view,
is an internal reference matrix>
Is rigid body transformation, namely an external parameter matrix;
the camera calibration process is to restrain the product homography H of the following internal reference matrix and external reference matrix through calibrating pixel coordinate points and corresponding world coordinate points which are acquired by mark points on a display screen to solve:
due to scale invariance of homogeneous coordinate system, Z is eliminated, and the following is obtained:
in the calculation process, as the homogeneous coordinates are unchanged, a non-zero coefficient is multiplied to enable H33 to be 1, H is a homogeneous matrix, only 8 independent unknown elements are finally solved, each calibration plate corner point provides two constraint equations, therefore, when the number of the calibration display screen corner points on one picture is equal to 4, a matrix corresponding to the picture is obtained, when the number of the calibration display screen corner points on one picture is greater than 4, the optimal matrix is regressed by using a least square method, and then the constraint relation of the H matrix to the internal reference is used for continuously solving the internal reference K and the external reference transformation matrix T respectively.
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