Spatial phase filtering with a porphyrin derivative as phase filter in an optical image processor

A robust, self-aligned, polarization independent, pure phase filter was obtained using the intensity dependent refractive index (IDRI) medium, zinc tetraphenyl porphyrin (ZnTPP), a metalloporphyrin. An optical image processor with ZnTPP as the phase filter was designed so that both weak and strong phase objects can be tested with no appreciable design modification. A good phase contrast image with negligible amplitude reduction of the input beam was achieved and the porphyrin as phase filter was found to have several specific advantages over other IDRI media.