A brief review of the formulas for radial and decentering lens distortion is presented, with emphasis on the currently accepted representation of the decentering distortion. Recent technological advances, which include the large format close range camera, CRC-1, and the automated precision mono-comparator, AutoSet, caused the authors to reinvestigate the analytical plumb-line method of lens calibration. With AutoSet, measurements of 1000 images of points on plumb-lines are performed in under one hour and RMS plate residuals of one micrometer or less are produced. Brown's (1972) extension of Magill's formula for the variation of radial distortion with focusing is experimentally reverified with data of much higher precision than in previous investigations. The quality of the data allowed a more sensitive examination of the formula for decentering distortion, which led to the finding that decentering distortion also varies with focusing. A reinvestigation of the theory of decentering distortion extends the 1966 formulation by Brown to account for the variation experimentally observed. It is shown that decentering coefficients P1 and P2 for the lens focused at infinity need merely be appropriately rescaled in order to apply finite focusing. Implications of this discovery for close-range photogrammetry are explored.
Photogrammetric Engineering and Remote Sensing
- Pub Date:
- January 1986
- Instrumentation and Photography