Reduction of speckle in digital holography by discrete Fourier filtering

Abstract

We present a digital signal processing technique that reduces the speckle content in reconstructed digital holograms. The method is based on sequential sampling of the discrete Fourier transform of the reconstructed image field. Speckle reduction is achieved at the expense of a reduced intensity and resolution, but this tradeoff is shown to be greatly superior to that imposed by the traditional mean and median filtering techniques. In particular, we show that the speckle can be reduced by half with no loss of resolution (according to standard definitions of both metrics).

Quantization noise and its reduction in lensless Fourier digital holography

“…When N statistically independent intensities are added together, the variance of the sum increases N times and the standard deviation increases ffiffiffiffi ffi N p times but the mean value of the sum increases N times. Thus the coefficient of variation, also called the speckle index [47][48][49], which is the ratio of the standard deviation to the mean, in this case decreases as 1= ffiffiffiffi ffi N p . We experimentally prove this by capturing a number of different statistically independent speckle patterns of the object.…”

Speckle reduction of reconstructions of digital holograms using three dimensional filtering

“…Here we present results of a comparison between the best performing filter from this paper, the 2D filter and other standard speckle reduction techniques including the mean and median filters, the discrete Fourier filter (DFF) [41] and the best performing wavelet from a previous paper of ours [42]. Table 5 provides a comprehensive set of results and reveals that 2D filtering has outperformed the other techniques, achieving a similar level of speckle reduction but maintaining a higher resolution.…”

Binocular Holographic Three-Dimensional Imaging System Using Optical Scanning Holography

“…이렇게 획득된 실제 물체의 홀로그램은 스펙클 잡음에 오염되어 복원된 영상이 깨끗하지 않다. 홀로그램 정보 획득 과정에서 스펙클 잡음에 오염되는 것을 방지하거나 획득된 홀로그램 정보의 스펙클 잡음을 제거하는 방법에 대한 연구가 진행되었다 [11][12][13][14][15]. 하 지만 이러한 접근 방법은 스펙클 잡음 제거와 함께 물체의 홀로그램 정보도 훼손되는 한계가 있으며, 스펙클 잡음의 제 거 정도가 크지 않다.…”