The Shack-Hartmann wavefront sensor is composed of a lenslet array generating the spot images from which local slope
is calculated and overall wavefront is measured. Generally the principle of wavefront reconstruction is that the spot
centroid of each lenslet array is calculated from pixel intensity values in its subaperture and then overall wavefront is
reconstructed by local slope of wavefront obtained by deviations from reference positions. Hence the spot image of each
lenslet array has to remain in its subaperture for exact measurement of wavefront. However the spot of each lenslet array
deviates from its subaperture area when wavefront with large local slopes enters the Shack-Hartmann sensor.
In this research, we propose the spot image searching method that finds area of each measured spot image flexibly and
determine the centroid of each spot in its area. Also the algorithms that match these centroids to their reference points
unequivocally even if some of them are situated off the allocated subaperture are proposed. Finally we verify the
proposed algorithm with the test of a defocus measurement through experimental setup for the Shack-Hartmann
wavefront sensor. It has been shown that the proposed algorithm can expand the dynamic range without additional
devices.
The continuous thin-plate type with discrete actuators is widely used for active or adaptive mirrors in the medium size range from about 10cm up to 2m in diameters. The performance of a thin-plate deformable mirror could be characterized by the influence function of an actuator and the layout of the actuators. This paper first derives an equation which estimates influence functions of thin-plate deformable mirrors based on the analytic calculation and finite element analysis. Then the performance analysis for the case of equi-spaced actuators is presented.
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