  Shack Hartmann Sensor (SHS) is inflicted with significant background noise
that deteriorates the wave-front reconstruction accuracy. In this paper, a
simple method to remove the back ground noise with the use of Zernike
polynomials is suggested. The images corresponding to individual array points
of the SHS at the detector, placed at the focal plane are independently
reconstructed using Zernike polynomials by the calculation of Zernike moments.
Appropriate thresholding is applied on the images. It is shown with
computational experiments that using Zernike Reconstructor along with usual
thresholding improves the centroiding accuracy when compared to direct
thresholding. A study was performed at different Signal to Noise ratio by
changing the number of Zernike orders used for reconstruction. The analysis
helps us in setting upper and lower bounds in the application of this denoising
procedure.
