Imaging polarimetry with an micro-retarder array

We developed a 92×70 micro retarder array for an imaging polarimetry. The micro retarder array consists of polyimide subwavelength-period gratings of 300 nm period with different orientations. The phase retardance is caused by the form birefringence of the subwavelength structure. The gratings were fabricated with the direct-writing electron-beam lithography and the reactive ion etching. The phase retardance was 0.57 π for the 550 nm light wavelength. We have observed a birefringence image of a tensed plastic film by using the imaging polarimetry system.