Progressive scan
Progressive Scan simply means an non-interlacing scan, or sequential, line by line scan of the image.
CCD matrices do not scan the image but it is easier to visualise the output as if it did. For the scientific or industrial applications, it is sometimes named “slow scan”.
The main advantage of slow scan is that the whole image is captured in a given instant, unlike interlacing systems which collect each field sequentially. Each vertical image motion from field to field disturbs the interlaced image in a very complex manner. Horizontal movements make a sawtooth cut of the vertical lines. If the movement is too important, the two fields will show images which are too staggered one from another. By using stroboscopic light to freeze the movement, the image will only appear on the active field during the light pulse. Because of these movement effects, only one data field can be used for image processing. It reduces the vertical resolution by 50% and increases the vertical aliasing of the image.
As a full frame is collected, slow scan systems do not suffer the same effects due to the image movements as in interlacing systems. Thus, slow scan systems are said to have an enhanced resolution compared to interlacing systems. For scientific applications, the progressive output is captured by an (on-board or external) acquisition card (of a computer). A post-processor reformats the data according to the desired display.