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Interlace and dither reduce sensor sampling intervals without increasing detector count. A high-resolution frame image is comprised of two or more lower resolution fields or sub-images taken sequentially in time. Between each field or sub-image, a nodding mirror or other mechanical means is used to move the locations where the scene is sampled. Interlace and dither achieve high resolution while minimizing focal plane array complexity.
The mechanical operation of a dither or microscan mirror is illustrated in Figure 5.1. A mirror is inserted between the objective lens and the FPA. The angular motion of the mirror about the scan axis is very small. Image translation on the FPA is sub-pixel (that is, less than a sample spacing). The figure indicates a horizontal translation of the image, but the mirror can be made to scan about any axis. The sub-pixel image translation provided by the scan mirror allows changing the sample phase of the FPA relative to the scene.
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