Decentration Error Analysis Using Optical Centering Device and Skew Ray Tracing

Any small decentering of a lens's surface can be resolved into an angular tilt of the surface about its intersection with the optical axis. The decentration error of an optical lens has a significant effect on the quality of the image it produces. This paper presents a simple method based on skew ray tracing and an optical centering device to calculate the decentration error resulting from the surface tilt of an optical lens. The results reveal that the decentration error and the radius of the spot circle traced out on the detector of the optical centering device as the sample of interest is rotated are related via a linear approximation when the decentration error is small. Furthermore, it is found that for small surface tilt angles, an approximate value of the decentration error can be obtained simply by taking the first-order differentiation of the mathematical expression for the decentration error.