Introduction to Scanners
Bar code scanners are electro-optical systems that include a means of illuminating the symbol and measuring reflected light. The light waveform data is converted from analog to digital, then processed by a decoder which is either built into the scanner or a separate plug-in device. The data is then transmitted to the computer-based application software. There are two basic types of scanners — handheld and fixed-mount.
Handheld Scanners
Handheld scanners are used to read bar codes on stationary items. There are three technology choices: contact wand, CCD (charge-coupled device) or laser.
Contact Wand
 A wand scanner is a hand-held device shaped like a pencil that is used to read bar codes. Proper scanning technique involves starting with the pen tip lightly touching the label, and moving across all the bars to the other side of the bar code in one continuous motion. There is virtually no depth of field to a wand scanner, but they work as well as any other type of scanner with the exception of scan rate, and it may cost as little as one-tenth the price of other manual scanning devices.
 CCD
Today, CCD and imaging technology is the next trend in barcode data collection and can read a barcode from distances up to six feet away. Some CCD readers are faster, more accurate and less expensive than other laser technologies. Also, these types of scanners are considered to be more reliable because they have no moving parts susceptible to damaged or malfunction. Finally, only CCD readers can read popular 2D Symbologies, such as RSS, Datamatrix and QRCode. It can also decode PDF417 and Composite.
Laser
When contact with the bar code is awkward or if the nature of the application makes contact impossible, the hand-held laser gun is an alternative scanning device to consider. The general design of a laser scanner incorporates a solid state laser diode, creating a scan line by projecting a beam of energy off a rotating prism or oscillating mirror. While a device of this sophistication is about six times more costly than a wand scanner, it is useful and worth the premium. Scanning a bar code on a curved or irregular surface or through multiple layers of stretch wrapping requires a non-contact device such as a laser scanner.
Fixed-Mount Scanners
Fixed-mount scanners are used to read bar codes on items that pass by a scanner. The items are either scanned by hand as in retail scanning applications or by conveyor belt as in industrial applications.
Fixed-mount scanners use moving-beam laser or CCD technology (referred to as "machine vision" or "vision-based" technology). Although fixed-mount laser scanners are widely used at grocery checkouts, they are now also used for work-in-process (WIP) manufacturing applications, warehousing and distribution sortation, and shipping applications.
Very small fixed-mount scanners are used in laboratory and process control applications. For high-speed sortation applications. the fixed-mount vision-based scanners are preferred. Overhead or side-mounted laser scanners are used across all industries. |
