The Silicon Diode Array Camera Tube

A new electronic camera tube has been developed for Picturephone® visual telephone applications; with minor modifications it should also be suitable for conventional television systems. The image sensing target of the new camera consists of a planar array of reversed biased silicon photodiodes which are accessed by a low energy scanning electron beam similar to that used in a conventional vidicon. This paper presents a description of the operating principles and an analysis of the sensitivity and resolution capabilities of the new silicon diode array camera tube. We also give the detailed experimental results obtained with the tubes. The gamma of a silicon diode array camera tube is unity and its spectral response is virtually uniform over the wavelength range from 0.45 to 0.90 micron with an effective quantum yield greater than 50 percent. For a 13.4 millimeter square target the silicon diode array camera tube's sensitivity is 20 μamp foot-candles of faceplate illumination with normal incandescent illumination or 1.3 μamp per foot-candle with fluorescent illumination; with a center-to-center diode spacing of 15 micron it's modulation transfer function is greater than 60 percent for a spatial frequency of 14 cycles per millimeter. Typical dark currents for a 13.4 millimeter square target are in the range of 5 to 50 nanoamperes.