Aviation Electronics Technician 1 - Historic Naval Ships Association

achieve maximum resolution. A large number ofdetector elements can be grouped together to form anarray (fig. 6-8, view A). The elements of this arrayare packed closely together in a regular pattern. Thus,the image of the scene is spread across the array like apicture or a mosaic. Each detector element views asmall portion of the total scene. The disadvantage ofthis type of system is that each detector elementrequires a supporting electronic circuit to process theinformation that it provides. Also, each detectorelement requires a preamplifier to boost the signal toa usable level.SINGLE DETECTOR.— Another method that isused to provide the operator with information is thesingle detector (fig. 6-8, view B). Here, there is onedetector requiring one set of supporting circuitry. Inthis type of system, the detector is scanned across theimage so that the detector can see the whole image.An optical system is required that can supply thescanning. This type of system is adequate if real-timeinformation is not needed, or if the object of interest isstationary or not moving quickly.Scene Dissection SystemThe scene dissection system is used to scan thescene image. There are many types of scanning-oneassociated with each type of detector array. When asingle detector with one axis of fast scan and one axisof slow scan is used, the scene is scanned rapidly inthe horizontal direction and slowly in the verticaldirection. As a result, the line is scanned horizontally;then the next line is scanned horizontally, etc.A vertical linear array is scanned rapidly in thehorizontal direction (fig. 6-8, view C). Onedetector element scans one line of the image. In thelinear array, there is a space, one element wide,between each element. The scan is one axis with aninterlace being used. A vertical linear array isscanned rapidly in the horizontal direction. Aftereach horizontal scan, the mechanism shifts theimage upward or downward one detector elementwidth so that on the next scan, the lines that weremissed are covered.Each system has an optimum configuration ofdetector array and image dissection. If the number ofelements in the detector increases, the systembecomes more complicated. Also, the cost of theFigure 6-8.-Detector arrays.6-6