Inspecting Scattering Pattern Carriers With Enhanced Optical Contrast
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
Absorbing patterns on a scattering substrate, such as metal conductors on a ceramic carrier, have an improved optical contrast when they are illuminated with polarized light and observed through a crossed analyzer. According to Fig. 1, the polarization state of light remains unaltered upon reflection at the surface of substrate 2, whereas light scattered within the substrate is completely depolarized ( a '-' sign and an asterisk indicating a polarized light ray and depolarized light, respectively). This effect can be exploited to generate a quasi-transmission image of the pattern 1 by using only the depolarized light, reemanating from the substrate, and the suppressing light, reflected at the surface with suitably arranged analyzers. Fig.