Pen-type Reader
Laser Scanner
Laser scanners work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or
a rotating prism to scan the laser beam back and forth across the bar code. As
with the pen type reader, a photodiode is used to measure the intensity of the
light reflected back from the bar code. In both pen readers and laser scanners,
the light emitted by the reader is rapidly varied in brightness with a data
pattern and the photodiode receive circuitry is designed to detect only signals
with the same modulated pattern.CCD Reader
CCD readers
use an array of hundreds of tiny light sensors lined up in a row in the head of
the reader. Each sensor measures the intensity of the light immediately in
front of it. Each individual light sensor in the CCD reader is extremely small
and because there are hundreds of sensors lined up in a row, a voltage pattern
identical to the pattern in a bar code is generated in the reader by
sequentially measuring the voltages across each sensor in the row. The
important difference between a CCD reader and a pen or laser scanner is that
the CCD reader is measuring emitted ambient light from the bar code whereas pen
or laser scanners are measuring reflected light of a specific frequency
originating from the scanner itself.Camera-based Reader
Two-dimensional imaging scanners are the fourth and newest type of bar code reader. They use a camera and image
processing techniques to decode the bar code.Video camera readers use small video cameras with the same CCD technology as in a CCD bar code reader except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two dimensional array so that they can generate an image.
Omni-directional barcode scanner
