Frame Grabbers:

An essential component of an image acquisition system that
utilizes analog video sources is an analog/digital converter. 
This hardware device superimposes a grid (256x256, 512x512, etc.)
over each image frame, and translates each grid unit of the image
frame into binary values called pixels (picture elements)
according to the brightness value of each unit.  The pixels
represent a digital format, enabling the transformed image to be
manipulated in a computer environment.  Pixels may be square or
rectangular, with their shape corresponding to the ratio of the
horizontal dimension to the vertical dimension (aspect ratio) of
the image.  The spatial resolution of a digitized image is
expressed as the ratio of lines to pixels per line (horizontal
rows x vertical columns).  

The digitization process must be synchronized with the speed of
the analog video (30 frames per second) for the system to capture
images in real-time.  The frame grab board must also have a
resident memory capacity that can accommodate one or more frames
of digitized video.  The memory requirements for a frame grab
system can be extensive, with image file size depending on
factors of image resolution, number of gray levels, and color
capabilities. 

<cfile11>   Information Organization
<cfile48>   Frame Grab Equipment
<cfile49>   Scanners