Digital Image Processing: Corrections, Enhancement and Stitching

Detector corrections

Before an image is shaped for viewing, the raw detector signal is cleaned up. The analog-to-digital converter turns each detector element's signal into a number, a step called quantization, and the bit depth sets how many shades of gray are possible. Flat-field correction, also called gain and offset calibration, evens out small differences in how each element responds, so a uniform exposure produces a uniform image. Dead pixel correction fills in elements that no longer respond by averaging their neighbors. These corrections depend on detector calibration, which is why calibration is part of routine QC. After that come histogram analysis, rescaling to a standard brightness, and the look-up table that sets contrast for the body part.