Two-dimensional phase unwrapping algorithm is the important step and key technology of three-dimensional shape
measurement. In order to obtain the appearance characteristics of the object more accurately, a new phase unwrapping
algorithm based on unweighted least-squares is presented in this paper, which is an improvement of discrete cosine
transform (DCT) phase unwrapping algorithm. The advantage of this method is not only because of the global
algorithms, processing the image as a whole, each pixel's value in the image is uniquely determined by solving the
Discrete Poisson's equation with Newman boundary conditions which makes the least-squares solution of the wrapped
and unwrapped phase difference minimum, but also can reduce the residues effectively. Through computer simulation,
this new method and the original DCT algorithm were compared. Theoretical analysis and the results prove the validity
of this method .The improved algorithm can eliminate the residues in the wrapped phase pictures more effectively. The
phase information of the object can be reconstructed more accurately.
In this paper, a method of reduction speckle noise in digital holography is presented. This method can suppress the
speckle noise effectively. First, a series of digital holograms are recorded with different titled plane wave illuminations.
Then each of the complex amplitude is reconstructed. The speckle noise is suppressed by incoherent superposition of the
reconstructed intensity image fields. One of the advantages of this method is that the procedure is very simple and
effective. We make computer simulation by applying Fresnel transform algorithm and multiple reconstructed intensity
images of a picture with different titled plane wave as illuminating object light. The simulation results show that the
more the superposition of reconstructed intensity images, the better the reduction of speckle noise. And it also
demonstrates the validation of the present method.
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