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CN-122027784-A - Calibration module and calibration method for calibrating line scanning camera array combined imaging system

CN122027784ACN 122027784 ACN122027784 ACN 122027784ACN-122027784-A

Abstract

The invention belongs to the field of image processing, and discloses a calibration module for calibrating a line scanning camera array combined imaging system, which comprises a calibration plate; the calibration plate is provided with a stripe grid area, wherein the stripe grid area comprises a plurality of stripe grids which are arranged at equal intervals from top to bottom and used for calibrating distortion parameters of the line scanning camera, and the chessboard grid area is formed by arranging a plurality of grids with identical specifications in a grid array mode and used for calibrating an inclination angle of the line scanning camera in the moving direction of the calibration plate. The calibration module is used for calibrating the self distortion and the inclination angle of the line scanning cameras through the stripe grid area and the chessboard grid area, so that the images obtained by the line scanning cameras can be integrated into a complete image without distortion after distortion correction and inclination angle correction. Meanwhile, the invention also discloses a calibration method based on the calibration module.

Inventors

  • ZHANG YAO

Assignees

  • 麓光科技(广州)有限公司

Dates

Publication Date
20260512
Application Date
20251225

Claims (11)

  1. 1. The calibration module for calibrating the line scanning camera array combined imaging system is characterized by comprising a calibration plate; The calibration plate is provided with: The stripe grid area comprises a plurality of stripe grids which are arranged at equal intervals from top to bottom and is used for calibrating distortion parameters of the line scanning camera; The checkerboard grid area is formed by arranging a plurality of grids with consistent specifications in a grid array mode and is used for enabling the line scanning camera to calibrate the inclination angle in the moving direction of the calibration plate.
  2. 2. The calibration module for calibrating the combined imaging system of the line scanning camera array according to claim 1, wherein the calibration board is further provided with a color band and/or a lattice grid area for calibrating the relative position of the image of each line scanning camera on the horizontal plane; The included angle between the extending direction of the color ribbon and the advancing direction of the calibration plate is an acute angle; the lattice grid area is formed by arranging a plurality of spots with consistent specification in a grid array mode.
  3. 3. The calibration module for calibration of a line scan camera array combined imaging system of claim 2, wherein the color bars extend from edges of the calibration plate to a position near the striped grid areas, and wherein the checkerboard grid areas and the dot matrix grid areas are disposed on both sides of the color bars.
  4. 4. The calibration module for calibrating a line scanning camera array combined imaging system according to claim 2, wherein the number of the chessboard grid area, the lattice grid area and the color bands is two, and the chessboard grid area, the lattice grid area and the color bands are symmetrically arranged on two sides of the stripe grid area.
  5. 5. The calibration module for calibrating the line scanning camera array combined imaging system according to claim 1, wherein the calibration plate is further provided with staggered grid areas, the staggered grid areas are composed of a plurality of grids which are arranged at equal intervals from top to bottom, and the grids are arranged in a staggered manner periodically.
  6. 6. The calibration module for calibrating a line scan camera array combined imaging system according to claim 1, wherein a starting color band and/or an auxiliary grid area are further arranged on the calibration plate; the initial color band extends from top to bottom; the auxiliary grid area is formed by arranging a plurality of auxiliary grids from top to bottom in sequence, and the density of the auxiliary grids of the auxiliary grid area is greater than that of the stripe grids of the stripe grid area; The starting color band and/or the auxiliary grid area are arranged at the edge of the calibration plate.
  7. 7. Calibration module according to any of claims 1 to 6, characterized in that there are at least not less than 3 striped grids, not less than 2 rows of grids in the field of view of the line scan camera array, preferably at least not less than 6 striped grids, not less than 5 rows of grids in the field of view of the line scan camera array.
  8. 8. The calibration module of claim 1, wherein the striped grid region is further configured to adjust a height of the line scan camera and an offset angle in a direction perpendicular to a direction of movement of the calibration plate such that a resolution of the line scan camera is consistent with a precision of movement of the calibration plate.
  9. 9. A calibration method of a line scanning camera array combined imaging system, which is characterized by comprising a line scanning camera array, a calibration module according to any one of claims 1 to 8 and a mobile device, wherein the line scanning camera array consists of a plurality of line scanning cameras; The method comprises the following steps: step 1, a calibration plate is arranged on a mobile device and positioned below a line scanning camera array, so that the length direction of a stripe grid is consistent with the movement mode of the calibration plate; Step 2, adjusting the height of the line scanning camera and the offset angle in the moving direction perpendicular to the calibration plate so as to enable the resolution of the line scanning camera to be consistent with the moving precision of the calibration plate; step 3, obtaining an image through a line scanning camera, and obtaining distortion parameters of the image through the central positions of different stripe grids in the image; Correcting the images obtained by each line scanning camera according to the distortion parameters and the offset angles of each line scanning camera; Step 5, adjusting and splicing the corrected images obtained by the line scanning cameras according to the relative positions of the line scanning cameras in the horizontal plane to obtain the images of the calibration plate; and (5) confirming that the image is an accurate undistorted imaging result, and taking the relative position, the inclination angle, the distortion parameter and the resolution of each line scanning camera on the horizontal plane as the parameters of subsequent imaging.
  10. 10. The method of claim 9, wherein the distortion parameter is determined by: step 310, obtaining the central positions of a plurality of stripe grids in an image, and obtaining an actual central position coordinate sequence E '= { y' 1 , y' 2 , y' 3 , …, y' n }; step 311, selecting m stripe grids positioned in the center of the plurality of stripe grids, and calculating an adjacent point spacing array D= { D ' 1 , d' 2 , d' 3 , …, d' m-1 }, so as to obtain an average value D' 0 of the array D; Step 312, calculating a plurality of center position coordinate sequences E= { y 1 , y 2 , y 3 , …, y n } of the stripe grids which are theoretically undistorted according to the mean value d' 0 ; step 313, constructing a distortion model based on theoretical undistorted coordinates y and distortion coordinates y ' by using an actual center position coordinate sequence E ' = { y ' 1 , y' 2 , y' 3 , …, y' n } and an undistorted center position coordinate sequence E= { y 1 , y 2 , y 3 , …, y n }, wherein the distortion model is n multiple one-time equations; The distortion model is n 2-degree polynomials or n 3-degree polynomials; The 2 nd order polynomial is y' =a 0 y+ a 1 y+a 2 y 2 ; the 3 rd order polynomial y' =a 0 + a 1 y+a 2 y 2 +a 3 y 3 ; a 0 、a 1 、a 2 、a 3 is a coefficient of the distortion model, which is a constant; when the constructed distortion model is a polynomial of degree 2, m is more than or equal to 3, and when the distortion model is a polynomial of degree 3, m is more than or equal to 4.
  11. 11. The method according to claim 9, wherein the method for determining the inclination angle is: Step 320, obtaining vertex coordinates of grids of the chessboard grid area in the image; Step 321, fitting coordinates of vertexes of the same side of the grid of the same row into a straight line in a direction perpendicular to the movement direction of the calibration plate, and calculating the slope of the straight line; step 322, repeating step 321, obtaining the slope of the straight line formed by the grids of different rows, and calculating to obtain the average slope of a plurality of straight lines; step 323, calculating to obtain the inclination angle of the line scanning camera according to the average slope; The method for acquiring the relative position of each line scanning camera on the horizontal plane comprises the following steps: Adopting an image matching method, taking color bands and/or lattice grid areas in images of two adjacent line scanning cameras as objects of image superposition, and determining the horizontal relative positions of the two adjacent line scanning cameras; when the horizontal relative positions of any two line scanning cameras are obtained, the position of the first line scanning camera is taken as a zero point, and the relative coordinate value of each line scanning camera is obtained; When the images are spliced, the positions of the images are adjusted according to the relative coordinate values.

Description

Calibration module and calibration method for calibrating line scanning camera array combined imaging system Technical Field The invention belongs to the field of image processing, and particularly relates to a calibration module and a calibration method for calibrating a line scanning camera array combined imaging system. Background The line scanning camera is an imaging device widely applied to machine vision systems, such as imaging and detecting systems of continuous or long-size targets of printed matters, plates, films and the like. The working principle of the printer is similar to that of common printers for copying and printing. The method comprises the steps of collecting at high speed, collecting the next line after collecting one line each time, and splicing all images into a picture after the scanning of all images is completed. The linear scanning imaging system mainly comprises a linear array sensor, a motor, a driver, a motion control card or PLC, a mechanical unit and the like, and the components work cooperatively to ensure that the acquired images are synchronous with the conveying belt. However, due to the resolution requirements of the inspection target, a single line scan camera typically cannot cover the entire product inspection area. Therefore, it is often necessary for a plurality of line scan cameras to form an imaging array to complete. Because of a series of interferences such as machining errors, assembly errors and the like, the imaging resolution (unit: mm/pixel), the spatial position, the mounting angle, the mounting height and the imaging distortion degree of each line scanning camera are different. This presents great difficulties for the application of line scan camera arrays in precision optical metrology. The existence of the above problems makes large format line scan array imaging systems difficult and heavy in precision optical measurement and detection applications. Disclosure of Invention Based on the above, a first object of the present invention is to provide a calibration module for calibrating a line scanning camera array combined imaging system, wherein the calibration module performs self distortion calibration and inclination angle calibration by using a line scanning camera through a stripe grid area and a checkerboard grid area, so that images obtained by each line scanning camera can be integrated into a complete image without distortion after distortion correction and inclination angle correction. Meanwhile, the invention also discloses a calibration method based on the calibration module. In order to achieve the aim of the invention, the invention adopts the following technical scheme: a calibration module for calibrating a line scanning camera array combined imaging system comprises a calibration plate; The calibration plate is provided with: The stripe grid area comprises a plurality of stripe grids which are arranged at equal intervals from top to bottom and is used for calibrating distortion parameters of the line scanning camera; The checkerboard grid area is formed by arranging a plurality of grids with consistent specifications in a grid array mode and is used for enabling the line scanning camera to calibrate the inclination angle in the moving direction of the calibration plate. In the calibration module for calibrating the line scanning camera array combined imaging system, the calibration board is also provided with a color band and/or a lattice grid area for calibrating the relative position of the image of each line scanning camera on the horizontal plane; The included angle between the extending direction of the color ribbon and the advancing direction of the calibration plate is an acute angle; the lattice grid area is formed by arranging a plurality of spots with consistent specification in a grid array mode. In the calibration module for calibrating the line scanning camera array combined imaging system, the color bars extend from the edge of the calibration plate to a position close to the stripe grid area, and the chessboard grid area and the lattice grid area are arranged on two sides of the color bars. In the calibration module for calibrating the line scanning camera array combined imaging system, the chessboard grid area, the lattice grid area and the color bands are respectively two and are respectively arranged at two sides of the stripe grid area. In the calibration module for calibrating the line scanning camera array combined imaging system, the calibration plate is further provided with staggered grid areas, the staggered grid areas are composed of a plurality of grids which are arranged at equal intervals from top to bottom, and the grids are arranged in a staggered mode periodically. In the calibration module for calibrating the line scanning camera array combined imaging system, the calibration plate is also provided with an initial color band and/or an auxiliary grid area; the initial color band extends from top to botto