Abstract: A biological sample is scanned with Time-Delay Integration (TDI) by a CCD camera having columns and rows. When the light from a location of the sample falls onto a picture element (pixel) on the camera, the photons of the light are converted to electrons. The electrons within that pixel are shifted down one row to the pixel directly beneath it. The shifts occur in the columnar direction of the camera while the sample is moved synchronously with the electrons. The electrons shifted off the bottom row of the camera are measured and converted into a digital value for that picture element in the sample image.