Criteria and methods for focusing high-precision optical measuring systems

Abstract

The article discusses the features and methods of focusing the optical systems of star sensors using test images of a single star. The purpose of focusing is to set the photodetector plane to the desired position relative to the best image plane of the lens. Such a required position should provide the optimal shape and size of the star image over the entire image field taking into account the shift of the focal plane when the calibration and operation environment changes. Estimating the shape and size of a star can be done in a variety of ways. The most complete information is provided by the analysis of the point spread function by approximating the image by two-dimensional functions. The preservation of the shape of the image of the star over the entire field is ensured by the absence of an inclination between the two considered planes. The value of the maximum allowable tilt can be determined by analyzing the depth of field of the image. Tilt correction is carried out constructively with the help of adjusting elements. Changing the calibration and operating environment will shift the best image plane and should be taken into account as a correction when focusing. The correction value can be calculated during lens design and verified experimentally. The article also describes bench equipment that allows focusing various optical systems, taking into account the considered criteria.