An Efficient Implementation of a Phase Unwrapping Kernel on Reconfigurable Hardware

The optical quadrature method of microscopy (OQM) was developed at Northeastern University for the purpose of non-invasively capturing phase data to image the sample being studied. This phase data need to be unwrapped before it can be of use. Phase unwrapping is the process by which an integer multiple of 2¿ is added to a measured, wrapped phase value in order to generate a continuous function. The algorithm used is the minimum L^P norm method which uses a two dimensional discrete cosine transform (2-D DCT) to solve the discrete Poisson equation. This calculation forms the most computationally expensive part of the minimum L^P norm method. This paper presents an implementation on reconfigurable hardware that performs the 2-D DCT over the entire image, solves the Poisson equation and then performs the two dimensional inverse discrete cosine transform (2-D IDCT) using a novel FPGA implementation of the DCT with a semi-floating point data representation.