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Charge-Coupled Scanned IR Imaging Sensors

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Semiannual rept. no. 3, 1 Jul 1974-30 Apr 1975

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A charge-coupled imager sensitive to infrared light as far out as 3.5 micrometers has been fabricated and operated. It consists of a linear array of 64 Pdp-Si Schottky-barrier detectors adjacent to a three-phase charge-coupled shift register. The design has a single level of metallization with gaps. A single transmission gate, when pulsed on, coupled each detector to its associated shift register gate thus reverse-biasing the detectors. The charges transferred to the shift register are then read out sequentially to produce the video signal. Operation is similar to that of a vidicon. The shift register had transfer losses as low as 0.0005 per transfer as measured with an electrical input. Visible images were sensed directly by illumination of the shift register through the gaps as well as through the unthinned substrate. Infrared images 1. 1 micrometers wavelengths 3.5 micrometers were sensed by the Schottky- barrier detectors illuminated through the transparent substrate. The two imaging modes could be easily distinguished by their spectral sensitivities as well as by their response to changes in their separate integration times. All IR measurements were made at 77 K. Uniformity was within a few percent, and objects at 110 C could be detected. A scheme for observing low-contrast, thermal scenes without requiring the charge-coupled shift register to carry the entire background signal has been implemented in the design of this chip. Operation in this mode was also demonstrated.

Subject Categories:

  • Electrical and Electronic Equipment
  • Infrared Detection and Detectors
  • Solid State Physics

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