7. Computer methods for processing signals and images

A.V. Kraiski, T.V. Mironova
P.N.Lebedev Physical Institute, Russian Academy of Sciences, Russia

Distortion and chromatic characteristics of some cameras and removable lenses

The correlation method is used to compare the digital calibration object with the digital image obtained with optical system under test. For a set of cameras and removable lenses the distortion matrices and chromatic aberration data are obtained. For the absolute majority of cameras, the displacement between the red and the blue channels of images is maximal in the corners of the frame and is less than one pixel. Distortion of most fixed-focus lenses is very small, about 0.5%. Distortion of zoom lenses and cameras is in the range of 2% - 4.5%. For some cameras and lenses the dependence of distortion on the focal length is shown. Measurements are extremely simple, without the use of precision systems and stands. We make no prior assumptions about the properties of the function of distortion (eg, radial symmetry). We do not get a polynomial approximation of the distortion matrix, but measure directly the value of the displacement at any point of the frame.
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