CCD Scanners

CCD scanners are a low-cost, non-contact bar code reading technology, well suited to close-range scanning of moderately sized codes.

Of the two "non-contact" technologies (CCD and laser), CCD scanners are generally the lower-cost option.

CCDs use technology similar to that found in modern video cameras; they "scan" the bar code by capturing a complete image of the code at once. CCD scanners are usually recognisable by their wide heads and the way they illuminate the bar code, typically in red light. You have probably seen these scanners in use at check-outs in places such as DIY stores.

Although technically a non-contact technology, most CCD scanners have a depth of field — i.e. reading distance — of only one or two centimetres. Recent advances in optics, though, now allow some CCDs to work at longer distances, in some cases five centimetres or more. Generally, CCD scanning remains a close-proximity reading technology.

CCD scanners come with a variety of output and interface types, depending on the individual model and manufacturer. Because CCD scanners already contain a built-in microprocessor, the output is usually already decoded. Common output types are RS232 serial, TTL serial, or keyboard wedge interface.

Apart from the need for close proximity, the main drawback of CCD scanners is the need to match the maximum reading width of the scanner head to the bar codes being read. A CCD scanner with a maximum head and reading width of 60mm, for example, cannot read a bar code that is 70mm wide. Generally, the widest head width for regular-style CCD scanners is around 80mm.

It might seem logical, therefore, to always choose the widest-head scanner available. However, there is sometimes a marginal trade-off between a wider CCD head and first-time read rate, since narrower heads can occasionally have a slight performance advantage. Care should therefore be taken when selecting a CCD scanner with the optimum head width. For much larger bar codes, it is usually necessary to move up to laser scanners. One further limitation concerns curved surfaces: while CCD scanners can handle modest curvature much better than a wand can, they are not usually designed to cope with the optical effects of curvature.

CCD scanners probably represent the best value-for-money option for close-proximity scanning, and many are sold as wand upgrades. If getting close to the code is not a problem and the throughput requirement is medium-volume, CCD scanners are a popular choice.