Investigation into the Precision of a Digital Camera

摘要

The point positioning precision of a CCD camera and a least squares matching technique was assessed using bundle block adjustment tests. A precision of 0.03 pixels (= 0.8 micrometer for a pixel size of 27 micrometers) is obtained for large symbols. The precision of small symbols is 0.04 pixel (1.1 micrometers). The only significant camera deformation is a difference in x- and y-scale, caused by the different pixel sizes in column and row direction of the sensor array. The principal distance of the camera is 57.54 mm. The principal point could not be determined. After the adjustments, the residuals of the image coordinates of several images were plotted. Although they seemed to be random at the first sight, the residual patterns of certain images show large similarities. These correspondencies are not caused by possible differences in the distances between the individual sensors of the camera and are independent of the method of coordinate calculation, since the same phenomenon is observed after the adjustment of the coordinates of the symbols in the binary images. The precision of these centers of gravity in binary images is good: 0.04 pixel for large symbols and 0.05 pixel (1.4 micron) for small symbols.