Integrated arrays of silicon photodetectors for image sensing

Development of linear and area arrays of silicon photodetectors operating in a photon flux integration mode is described. This mode of operation, which permits the trade of gain for bandwidth, is reviewed. It is possible to obtain full frame storage at commercial TV frame rates from area arrays of silicon phototransistors. Practical integrated structures of both diode and transistor arrays will be shown, and a method of coincidence sampling of an area array of photodetectors, which eliminates the need for isolation by the use of integrated MOST AND gates in the detector array, is described. This structure provides the following advantages: 1) High sensitivity and broad spectral response--photons absorbed far below the surface are not lost because of isolation barriers. 2) Reduced cross modulation. 3) A single video output terminal is required, thus avoiding the need to switch externally a large number of video channels to a common load, as is the case where isolation of photoelements is employed.