Advances in Phase Retrieval by Transport of Intensity Equation

There are many factors in the calculations of Transport of Intensity Equation, which may lead to the uncertainty of the retrieved phase. In this paper, effect of these parameters such as defocus distance, focus plane and magnification, on the results is studied. It is hoped that this would provide a more robust and reliable method for phase and optical height measurement. Furthermore, the effect of intensity derivatives calculated using two defocussed images as opposed to multiple images is also considered. A microlens array is chosen as the test sample in a commercial transmissive Transport of Intensity Equation system. From this study, it is concluded that the biggest factor influencing the result is the magnification, which is seen to provided totally different phase value for the same shape. Incorrect defocus distance or in-focus plane also lead to inaccurate reconstruction results while higher order differential provides better and more stable results than traditional two image differential.