Hand
held scanners usually come in two forms, 3D and document scanners. Hand held
scanners are manual devices/units which are passed over the surface of the image
which requires scanning. Hand held scanners when used in this way require a
steady hand, as any uneven movements of the scanning rate will result in the
distortion of the scanned image. For this reason, most Hand held scanners will
usually have a small light or indicator, to notify the user if the scanning
action is too fast. A typical hand held scanner will have a small viewing
window, through which the document being scanned can be viewed. Hand held
scanners were popular in the 1990s but has since waned, but the use of 3D
scanners still remains popular for many applications such as inspection and
analysis, reverse engineering and medical applications.