Patent ID: 7699236
Filing Date: 2010-04-20
Classification: G06K,G07D

Abstract:
1. A bi-directional image capturing system for detecting a spatially varying refractive index pattern applied to a substrate, comprising: a light source directed along an optical path for illuminating the pattern being imaged and detected; a slit aperture, positioned to receive light from the light source and to illuminate a set of angles one azimuth at a time in a range of angles to ensure one illumination direction is measured for each position; a polarizer, positioned to receive filtered light from the slit aperture and to polarize the received light; a first concave parabolic mirror having an optical axis disposed parallel to the optical path, positioned to intercept the polarized light from the polarizer and to focus the intercepted polarized light to form an incident ray that strikes the pattern at a selected angle of incidence; a second concave parabolic mirror for intercepting the light that reflects from the pattern at an angle θ and directing it into a second optical path; and an image capturing device for receiving the light from the second optical path.