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A Very Low Bandwidth, Unattended Imager For Surveillance Applications

The need arises in certain vehicular surveillance applications for an electronic imager that can perform without human interaction and can transmit definitive images over very low bandwidth channels. The investigators have found that line scan imagers offer particular advantages toward these ends. Specifically, the use of a line scan imager facilitates the following processing steps: 1) Segmentation of the vehicle from the background, 2) Auto-matic exposure control, 3) Light level equalization prior to quantization, and 4) Implementation of an adaptive sampling scheme. These processing steps together with the source encoder may be implemented on a relatively low throughput processor and achieve near real time operation. The specific encoding method used here is an extended differential pulse code modulation (DPCM). A prototype system has been developed, producing medium resolution images at less than 10K bits per frame.