Saturday, July 30, 2005

Camera Parameters

The extrinsic parameters are the parameters that define the location and orientation of the camera reference frame with repect to a known world reference frame.
The intrinsic parameters are the parameters necessary to link the pixel coordinates of an image point with the corresponding coordnates in the camera reference frame.
The camera extrinsic parameters are the translation vector. T, and the rotation matrix, R(or, better, its free parameters), which specify the transformation between the camera and the world reference frame.
For a pinhole camera, we need 3 sets of intrinsic parameters:
1. perspective projection, for which the only parameter is the focal length, f;
2. transformation between camera frame coordinates and pixel coordinates;
3. geometric dostortion introduced by optics.
Camera 2 Pixel coordinates: (x_im, y_im) the image point in pixel units, (x,y) the same point in camera reference frame.
x = -(x_im - ox)sx;
y = -(y_im - oy)sy;
(ox,oy) in pixel of the image center. (sx,sy) the effective size of the pixel(in mm) in the h&v direction.
Therefore, the intrinsic parameter is: f, ox, oy, sx,sy

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