Abstract
A viewing-zone control technique has been realized by use of polarization modulation. This paper
reviews fundamentals of polarization encryptions by use of retarder fi lms and their application for the
viewing-zone control of an information display. Optical encryption with two shared patterns enables
secure display, which prevents eavesdropping of a displayed information and peeping at the decoded
result. Optical encryption with stacking position as an additional key enables dual-view display, which
provide two different displayed images without decreasing of image resolution. Thus, a multi-functional
information display can be realized by renewing spatial codes for polarization modulation.
