Measurement of a birefringent sample based on ptychographical iterative engine using planar polariscope

Although it is a simple and convenient birefringence analysis instrument, the traditional planar polariscope is difficult to use for the quantitative measurement of phase retardation and azimuth angle. A novel 2D quantitative birefringence measurement method based on ptychographic iterative engine (PIE) in a planar polariscope is proposed. The birefringent sample is placed in the parallel probe-forming path. By inserting an isotropic diffractive object with good modulation property for the probe, the ptychographic scan measurements are performed under two different dark-field states. The amplitudes and phases of the two probes containing different birefringence information were reconstructed, and the phase retardation and azimuth angle obtained with a simple and straightforward extraction approach. The approach was verified using a classic diametrically compressed disc. The proposed method solves the problem of quantitative birefringence measurement in planar polariscopes by introducing the phase information. It reduces the PIE scans and shortens the data collection time, which provides a practical measurement means for birefringence in materials, biophysics and opto-mechanical system.