Evaluation of internal defects in optical component via modified-3PIE

Sparsely and randomly distributed internal defects in the optical component can cause an inferior signal quality and serious measurement errors. A modified three-dimensional extend ptychographic iterative engine (modified-3PIE), which splits a sample into axial sections with known positions, is proposed to evaluate and reconstruct internal defects. The axial positions of internal defects are calculated to reduce the number of axial sections. There are only several axial sections with defects that are located at the calculated positions, and other sections are free-propagation parts. The complex amplitude transmittances of internal defects at different axial section positions are simultaneously retrieved. Simulation and experiments are conducted to verify the performance of the proposed method. Our proposed method does not require a reference beam and imaging system, and it can be applied to reconstruct a large area of the sample.