A high spatial resolution long-range surface shape detection device and detection method

Abstract

The invention discloses a high spatial resolution long-distance surface shape detection device and a detection method. The device includes a scanning optical head, which is characterized in that the scanning optical head includes a small-hole array plate, a beam splitter, a lens array, and an array detector; wherein, the small-hole array plate divides the input parallel beam into several The parallel thin beams are incident on the beam splitter; the beam splitter transmits each of the thin beams into the lens array, and the lens units in the lens array respectively transmit the corresponding thin beams Focusing on the surface of the object to be measured, the light beam reflected by the surface of the object to be measured is incident on the array detector through the lens array and the beam splitter in sequence. The device has simple structure and stable performance, and can perform high spatial frequency sampling measurement of the surface to be tested; it can expand the measurement of surface shape errors at higher frequencies (>1 line / mm); generally it can reach 10 lines / mm, or even higher.

Description

technical field [0001] The invention relates to the surface shape detection of large-scale mirror objects, in particular to a high-spatial resolution long-range surface shape detection system based on shear measurement. Background technique [0002] The surface error of the optical element surface has a very important impact on the performance of the optical system. According to the distribution of the spatial frequency of the surface error, it can be divided into high spatial frequency, medium spatial frequency and low spatial frequency error. The existing research results show that different frequency errors have different effects on the imaging system. For example, the refraction effect of high-frequency errors and the scattering effect of low-frequency errors will not significantly change the shape of the point spread function on the image plane, but will only cause the focus energy to change. Divergence, reduction of imaged contrast and signal-to-noise ratio, in contras...

AI Technical Summary

Problems solved by technology

However, the following two problems generally exist: (1) Since LTP uses a collimated beam to scan the sample, limited by the size of the scanning beam, the spatial frequency of the sampling point is relatively low (up to 1 line per millimeter (line per millimeter)), Obviously, some high-frequency surface shape error information cannot be effectively measured at present; (2) During the scanning process of the optical head, there are rotation errors of the air-bearing transmission table and laser pointing errors, although the reference optical path corresponding to the external mirror in LTP These errors can be partially eliminated, but because the reference optical path is slender, it is greatly affected by air disturbance, which reduces the accuracy of reference optical path correction

Images