Arbitrary Phase Shifting in Diffraction Common Path Interferometry

Quantitative phase imaging (QPI) has made a tremendous contribution to microbiology and medicine. Recently, QPI has been used for in-vitro fertilization optimization, and cell culture monitoring, among others. These accomplishments have been made using phase measurements. QPI is based on well-known optical metrology techniques. The challenge in QPI is developing phase measuring systems that can be used in the medical or microbiological environment. For such applications, two-beam interferometers are not suitable. In this context, we propose a common path interferometric system that provides quantitative phase measurements. The method combines the diffraction phase microscopy with the arbitrary phase shifting technique. The phase-shifted images are obtained by means of a shifted diffraction grating and an amplitude filter that allows interference between the undiffracted light and the first spatial frequency at the Fourier plane. The results show a reduction in the noise of the resultant phase when using the arbitrary phase shifting technique. This system can potentially be used to quantify nanoscale motions in living cells.