Application of constrained least squares filtering technique to focal plane detection in digital holography

To accurately locate the focal plane of the object in digital holography, the constrained least squares filter which can effectively eliminate the effect of noise on the focal plane determination, is introduced for digital holography. It not only overcomes the limitations of average filter (losses of details), min filter (excessive noise amplification) and wiener filter (estimation of the noise-to-signal power ratio) but also improves image's visibility and perceptibility. Finally, this filter is applied to the real holograms of calibration target and sprays. The experiment results demonstrate that this filter is an effective tool for enhancing the quality of hologram and improving the precision of focal plane determination and works well in the sprays.