Enhancement of low quality reconstructed digital hologram images based on frequency extrapolation of large objects under the diffraction limit
2016
During the reconstruction of a digital hologram, the reconstructed image is usually
degraded by speckle noise, which makes it hard to observe the original object pattern. In this
paper, a new reconstructed image enhancement method is proposed, which first reduces the
speckle noise using an adaptive Gaussian filter, then calculates the high frequencies that
belong to the object pattern based on a frequency extrapolation strategy. The proposed
frequency extrapolation first calculates the frequency spectrum of the Fourier-filtered image,
which is originally reconstructed from the +1 order of the hologram, and then gives the initial
parameters for an iterative solution. The analytic iteration is implemented by continuous
gradient threshold convergence to estimate the image level and vertical gradient information.
The predicted spectrum is acquired through the analytical iteration of the original spectrum
and gradient spectrum analysis. Finally, the reconstructed spectrum of the restoration image is
acquired from the synthetic correction of the original spectrum using the predicted gradient
spectrum. We conducted our experiment very close to the diffraction limit and used low
quality equipment to prove the feasibility of our method. Detailed analysis and figure
demonstrations are presented in the paper.
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