| 摘要 |
The invention provides a surveillance system comprising a number of infra-red detectors in an array, each of which is arranged to view a different portion of a field of view in order to discriminate between targets of different veiwed sizes at a target range. Each infra-red detector has in its output a threshold detector, the threshold level of which is determined by the mean output levels of adjacent detectors in the array. In a preferred example, for a given threshold detector in the output of a given infra-red detector the mean output level of two adjacent, but not immediately adjacent, infra-red detectors on one side and two adjacent, but not immediately adjacent detectors, on the other side are summed and the result divided by four to provide the reference level for the threshold detector concerned. |
