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.
Laser scanners provide excellent scanning productivity and accuracy; this allows operators to achieve high productivity in high-throughput areas of business. Laser scanners are capable of decoding barcodes over wide ranges and can achieve 50% more range than digital imagers. Because laser scanning technology has been refined, scanners are less expensive than comparable digital imagers. Although laser scanners are incapable of reading 2D symbologies, they are capable of reading a 2D-like symbology, PDF417. Laser scanners offer a number of advantages for a multitude of applications and should be considered the technology of choice for:
? Decoding at long distance ? Decoding UPC/EAN and other 1D barcodes used in retail ? Applications that require motion tolerance ? Self-Service shopping
While laser scanners prove to be advantageous in certain applications, other markets are better suited for digital imagers or a combination of both technologies.