Special lenslet array with long focal length range for Shack-Hartmann Wavefront Sensor

Since its emergence in the early 1970s, Shack-Hartmann Wavefront Sensing technology has been investigated and explored world-widely by the researchers and engineers. However, there are few papers or reports to study the system performance and key factors to affect the performance of a Shack-Hartmann Wavefront Sensor (SHWS), in this paper, through experimental study of the system stability of a SHWS, it is found that the image sensor and detector, normally a CCD, should be placed exactly at the focal plane of the lenslet array, otherwise it will bring in significant wavefront measurement error. In order to improve the system performance, a special lenslet array with long focal range is designed, and it is functioned by a spatial light modulator for sampling wavefront in a SHWS. Diffractive lenses with long focal length range can provide pseudo-nondiffracting beams, and a long range of focusing plane. The performances and effects of the modified SHWS with such a special lenslet array generated by a programmable SLM, are investigated, and the experimental results show that the system stability and measurement repeatability are not sensitive to the sensing distance, and can keep at a good level in a long range.