Abstract

Many surveillance applications require electronic imagers to provide real time or near real time pictures. An example might involve the security system of a sensitive facility where the monitoring of entering and exiting traffic is important. Since the objects of interest in this scenario are vehicles, it is possible to use a one-dimensional line scanner and let the vehicle self scan via its motion. The resulting image is two-dimensional with the vertical representing a spatial displacement and the horizontal time. The system consists of a Reticon 1 × 128 array, 8-bit Flash A/D, and TMS320 digital signal processor. The amount of light incident on a photodiode and integrated over time determines the value read by the A/D for that pixel. To achieve optimal operating range, the average value of all the pixels in the scan should be at the midpoint of the intensity range. This is accomplished by adjusting the integration time or the amount of time light is allowed to strike the element before it is interrogated. The adjustment procedure involves having two valid reads that occur at a fixed time interval. Between these two valid scans is a “dummy” read which has an adjustable time preceeding the next valid read.

© 1987 Optical Society of America