Analysis of measurement error depending on aperture shape of lenslets in wavefront sensor

Measurement error is discussed in a wavefront sensor consisting of lenslets and CCD. It is supposed that the center of gravity in a binary image, obtained through binarization from an analog image on the detection plane of the CCD, is used for estimation of the positions of focused spots on the detection plane. The standard deviation of the estimation error is analyzed for two kinds of focused spot shapes; circular and square. It is shown that the standard deviation of the estimation error is smaller in the case of the circular shape than that in the case of the square shape and also that the standard deviation in the case of the circular shape decreases significantly as the diameter of the circular increases.