Coincident Illumination Optical Detector
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
A NxM array of light sensitive diodes or photodiodes provides a fast and efficient optical detector for a coincident detection system. When multiple sources of illumination are used in microscope versions of inspection tools, parallel images result wherein the relative intensities of said images from the different light sources are compared to detect if scattered light is present from all sources and hence indicative of particulates being present. In addition, the detector must be able to differentiate between light sources and have low noise for sensitivity. A detector array, which satisfies these criteria, is shown in the figure. It consists of a N by M (12x2) array of light-sensitive diodes or photodiodes, where N is the number of area elements that are passed to the detector and M is the number of illumination sources.