Bar Code Scanning Technology types: Common hand held scanning technologies include wands, lasers, CCDs (charge coupled displays), and linear imagers. While they all share the same task - reading a bar code - each scanner type offers both advantages and disadvantages. The following discussion outlines how each technology works and the relative advantages/disadvantages of each.

Lasers: Hand held laser scanners are the most expensive of the scanning devices, but offer the largest depth of field making them an appropriate choice for scanning past distances of 14 feet.

How Lasers Work: Hand held laser scanners use a laser diode to create a scan line by projecting a beam of energy off a rotating prism or oscillating mirror. The beam is reflected out the scanner window onto the bar code, where light energy from the bars and spaces is reflected back to the scanner, collected on a mirror, focused, and read by a photo detector. The resulting signal may then be read using decoding software within the scanner or at the terminal or host.

Laser technology is a choice for non-contact applications, and the only choice for applications that require reading distances of a 14 feet or more.  Because they are non-contact devices, lasers will not wear out  scanned labels.

There are several disadvantages inherent in laser scanning: durability, cost and safety. Because lasers use both moving parts and mirrors, they are not as rugged as CCDs, Linear Imagers or wands. The reality is that hand held scanners will be dropped no matter how diligent the operator, and even if the internal parts do not break, misalignment of the laser can easily reduce performance or render the scanner unusable. Second, laser technology is the most expensive, both in terms of initial purchase price and product life costs. Finally, if not used properly laser beam initiated by laser scanner may cause damage to eyes if somebody happens to look directly into the beam.

CCDs: Charge coupled devices (CCDs) are extremely durable scanners for near contact and contact applications. Less expensive than their laser counterparts, CCDs having no moving parts to wear out or break.

How CCDs and Linear Imagers Work: CCD scanners use one or more LEDs to flood the bar code area with light, and an image of the code is transferred to an array of photo detectors. The characteristics of the bar code are determined by electronically sampling each individual photo detector which interprets each bar and space by the number of adjacent detectors sensing black or white. In other words, instead of reading each bar and space in succession, the CCD "takes a picture" of a very thin portion of the complete bar code which it then converts into a signal that may be decoded.

CCDs offer numerous advantages over competing technologies. Though less expensive than lasers CCDs also read various code densities, are easy to use, and require very little training. They are lighter and more rugged than lasers and, unlike wands, may be used for non-contact applications. New models offer depth of field that is well suited for most retail, banking and manufacturing applications.

Limitations to CCD technology include depth of field and scan width. While CCDs are an excellent choice for the applications listed above, they are not appropriate for long range scanning applications such as warehousing. CCDs are also not the best technology choice for applications in which a wide variety of label lengths and formats are used. Long messages or very low density codes can easily result in bar codes that exceed the width of the scan head, rendering them unreadable.

Linear Imagers

Linear imagers use CCD technology and an advanced optical design to provide a brighter, sharper aiming line, enhanced depth of field and faster performance than other scanning technologies. Exceptionally durable, linear imager are a cost-effective alternative to standard laser scanners.

How Linear Imagers Work: Linear imagers are technically similar to a CCD scanner. LEDs are used to flood the bar code area with light, and an image of the code is transferred to an array of photo detectors. The characteristics of the bar code are determined by electronically sampling each individual photo detector which interprets each bar and space by the number of adjacent detectors sensing black or white. What makes the linear imager unique is the speed at which the scanner is sampling the bar code. Where CCD scanners typically sample at 35 - 50 scans per second, a linear imager works at 270 scans per second. This allows for faster decoding, and better performance on poor quality codes.

Linear imagers offer numerous advantages over competing technologies. Though less expensive than lasers, linear imagers offer comparable depth of field  to a standard laser, are lighter and more rugged, and generally provide faster performance. Further, the brighter aiming line makes linear imagers the only choice when reading in full sunlight.

Linear imagers do not have any moving parts, which makes them very reliable. If the operator happens to drop the unit, the scanner will continue to function without any problem. HHP Scanners carry a 5 year warranty which basically covers them for the life of the scanner. 

Linear imagers are limited only by depth of field for extreme range scanning over 14ft..   New, extra-long range models are available, that can read out to 14 feet on large low density barcodes, making the linear imager an appropriate choice for mid to long range scanning applications such as inventory control in warehousing and logistics.

Connection interfaces

The devices above offer various connections to computer methods. Our applications, including TimeLegal supports the keyboard wedge type of interface. Serial connection is also available and used on our Pocket PC (Hand held) software. This runs on any Windows CE operating system. These system can be found on Dell Axiom, and HP IPAQ hand held computers and others.

At TimeLegal we offer a complete line of scanners and support, contact your representative for pricing and availability.