| 摘要 |
<p>A television system and method for monitoring and indicating changes in a scene from which electromagnetic radiation, such as visible light, emanates. A television system including a televison camera (10) scans the scene in known raster fashion in a series of image frames, producing an amplitude modulated video signal describing the energy intensity distribution of the scene. Clocking and gating circuitry (42, 44) triggered in synchronism with television camera synchronization signals defines a set of predetermined discrete spaced locations of the raster during each image frame and samples video signal amplitude at each of the defined locations. The same discrete locations a re sampled during each frame. Video selection circuitry (20) during a succession of sampling periods, inputs in real time a representation of each video amplitude sample to one of several storage channels (24, 26, 28) of a multi-channel memory system including a multi-channel counter. The video amplitude samples are allocated among the channels as a function of their amplitude values. The collection of stored amplitude samples in the multi-channel memory system thus constitutes a profile of the amplitude distribution of the video samples made during the frame. This first amplitude profile is then stored. The scanning, allocating and counting operation is repeated. Subsequently, comparison circuitry, (114, 116) in response to the development of a subsequent amplitude distribution profile, corresponding to a selected later frame, actuates an alarm (30) in response to the occurrence of a predetermined threshold difference between (1) the earlier and (2) a succession of later developed amplitude distribution profiles. Circuitry (132) is also provided for modifying characteristics of the threshold difference required to trigger the alarm. It has been found that even a single channel counter, responsive to video count samples in only a single amplitude range, can often provide enough information for a workable and inexpensive surveillance system. </p> |
