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Originally Posted by KenWittlief
but I know I have seen it 'used' in tv shoes with video from a survalince camera. Video is 640x480 at best, what you see is all that is there - you cant zoom in and see what was between the scan lines of the video camera (theres nothing there)
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Not to hijack the thread, but that is incorrect. There is more "there" there than is there.
In simple terms, the pixel represents a region of data in the source image, and not just an infinitely small single point at the center of the pixel region. The information assigned to a pixel is based on the aggregation of the image properties across the entire image region assigned to the pixel. Using techniques such as superresolution processing, cascading image enhancement, multiframe quiver analysis, and multiscale morphological smoothers (typically nonlinear smoothing filters for detail enhancement at large scales), information can be extracted from a digital image "from between the pixels."
For example, imagine that there is a region that is composed of a white square surrounding an inner red square. The outer white square completely fills the region that comprises the pixel. If the center of the region mapped directly to the pixel, then the CCD pixel would just "see" a point at the center of the inner red square, and record "red." No other information would be recorded, or available. However, in the real world, as the light from the region passes through the optical system and impacts the pixel on the CCD it is aggregated together and the pixel records "pink." When this happens, some of that information about the source region is available to be extracted. This also holds true for a series of adjacent pixels. Using this property, it is possible to determine precisely where dissimilar regions fall between pixel coordinates. From that information, image details and geometry that is not readily visible in the original image can be reconstructed.
Image processing labs have been using advanced versions of these techniques for years to extract information from digital images. The techniques are commonly used at places like The Multimission Image Processing Laboratory at the NASA Jet Propulsion Lab, the previous Intelligent Mechanisms Group at the NASA Ames Research Center, and many of the intelligence community facilities. Details on the fundamental algorithms associated with digital image enhancement are found in virtually every set of proceedings of the annual SPIE Conference or any of the several photonics society newsletters.
-dave