Camera Calibration
Function Overview
Camera lenses inevitably have some distortion, which affects image processing, especially in high-precision measurement applications. Therefore, it is often necessary to calibrate the camera parameters to improve calculation accuracy using the calibrated camera parameters. This function allows using the calibrated camera parameters as initial parameters in image alignment.
Usage
- Select the image project that needs camera calibration. Only image project files that have been opened in the software are supported.
- Switch to the camera group that needs to set camera parameters on the left.
- You can manually edit the source data, including various parameters such as pixel size, focal length, camera intrinsic parameters, installation angles, and installation errors.
- If the image alignment operation has been completed for the image project, the optimized parameters will be filled in the optimization column.
- Camera intrinsic parameters support import and export operations. Importing intrinsic parameters will fill in the source parameters, and exporting intrinsic parameters can choose to export source parameters or optimized parameters.
- If the selected image project file is multispectral data, the main band of the project can be set here.
Camera Parameters
The camera model determines the transformation relationship between the image space coordinate system and the image plane coordinate system. The origin of the image space coordinate system is at the projection center. The Z-axis points in the direction of the camera's line of sight, the X-axis points to the right, and the Y-axis points downward. The origin of the image plane coordinate system is at the top-left corner of the image plane, with the center coordinate of the top-left pixel being (0.5, 0.5). The X-axis points to the right, and the Y-axis points downward. The image plane coordinate system is measured in pixels.
The variables involved are as follows:
(X, Y, Z) - Coordinates of a point in the image space coordinate system
(u, v) - Coordinates of the projection point in the image plane coordinate system (in pixels)
(cu, cv) - Principal point offset
(K1, K2, K3) - Radial distortion parameters of the camera
(P1, P2) - Tangential distortion parameters of the camera
(b1, b2) - Affine and non-orthogonal parameters
(w, h) - Width and height of the image (in pixels)
f - Focal length of the camera (in pixels)
The transformation formula is as follows:
x = X ⁄ Z
y = Y ⁄ Z
r = √( x^2+y^2 )
x' = x(1+K r + K r + K r ) + P ( r + 2x ) + 2P xy
y' = y(1+K r + K r + K r ) + P (r + 2y ) + 2P xy
u = w*0.5 + c + x'f + x' b + y'b
v = h*0.5 + c + y'f