Laser Scanning Technology
During "scanning" process, a rotating-type mirror within the scanner causes the laser beam to sweep back and forth across the bar code at an arc of about 50-55° at a rate of about 50 times per second. An electronic sensor reads the reflected laser light, constantly searching for patterns of white and black and comparing these patterns to those used by various bar code symbologies to represent numbers and letters. Each sweep of the laser is an independent scan attempt, and to ensure accuracy, the system is normally configured to declare a “good scan” only after two or three consecutive scans read matching data.

Laser scanners are powerful enough to scan large bar codes at long distances, such as in warehouse applications. With the addition of “fuzzy logic” technology included in some products, they are also more able to read worn or damaged bar codes. Laser scanners are also versatile because the laser beam itself illuminates the target bar code. This greatly reduces the need for auxiliary lighting, making laser scanners more effective for scanning in low ambient lighting conditions. Because of the large amount of “competing” red light in sunlight (unlike artificial light sources), a laser scanner may have difficulty reading bar codes in direct sunlight.

CMOS Linear Imaging
Scanners based on "CMOS linear imaging" technology are generally less expensive than laser scanners, but they also offer somewhat limited performance. They do not have the range or "depth-of-field" that a "laser" scanner may have. A CMOS linear imager is basically a camera that captures rectangular digital images about 1 degree high and 40 degrees wide. Each digital image is analyzed for black and white bar code patterns and processed by decoding algorithms in the engine processor.The fact that the Linear Imager is based on camera-type technology, that means that there are no moving parts as compared to the rotating mirror of laser scanners, making them much more reliable in harsh conditions when the application will allow the use of this technology. With this technology, linear imagers have the potential of "faster scanning" operation than the laser counterpart.

Like all cameras, the CMOS engine has a "focal length" (depth-of-field or distance from the bar code target) where the captured image will be the clearest. While the depth-of-field of a laser engine can be quite large, the depth-of-field of the linear imager is much smaller. While the range of the laser scanner may be measured in "feet", the scanning range for the linear imager is generally measured in "inches" - often less than 20". However, this range still satisfies a lot of applications.