How Does a Barcode Scanner Work?

By: Archibald Rockwealth

CCD barcode scanners compete with laser scanners in point of sale and similar applications of the like. The CCD barcode scanners typically have the advantage over laser scanners in several applications. CCD scanners have no moving parts which make the CCD scanners less prone to failure. The laser scanners have oscillating mirrors which are subject to wear and mechanical failure, unlike CCD scanners. CCD scanners use LEDs for light illumination and last about ten times as long as laser light diodes.

Lasers typically have a warning label associated with direct viewing and safety precautions need to be taken. Because CCD scanners do not use lasers, there are no precautions that need to be taken for a safe viewing distance. The CCD scanners have scan rates of 45 scans per second or faster, which is comparable in speed to the laser scanners. CCD scanners are also much lighter and less expensive than laser scanners.

Laser scanners also exhibit some advantages over CCD scanners. Laser scanners have a more powerful light emission which means they can be used further from the barcode. The laser scanners have a greater depth of field or operating range. For this reason, the laser barcode scanners are good when used by a particularly untrained worker. The laser scanners, depending on the model, can be operated several feet away from the barcode, while the CCD scanner needs to be within several inches in order to work effectively. Laser scanners can read longer bar codes than CCD scanners. CCD units are usually limited to a barcode length of three or four inches.

The interfaces for CCD scanners have caused confusion between buyer and user. The keyboard wedge interface is the most common for CCD scanners. After the scanner has read a code, the scanner copies the keyboard.

A CCD scanner uses an array of hundreds of tiny light sensors lined up in a row in the head of the sensor. We have all seen a CCD scanner at the supermarket. The CCD reader is extremely sensitive and small because of the hundreds of sensors. A voltage pattern commensurate with the pattern in the bar code is created in the reader by measuring voltages across each sensor in a row. The most important difference to remember when using a CCD scanner is that it is measuring ambient light versus the use of a laser.

There are wireless barcode scanners which are wireless and operate on the same frequency as wireless Internet. The 802.11 radio frequency allows the freedom of the person using the scanner to move around and still have the functionality of having a cordless scanner. The downside to having a cordless scanner is the fact that you are limited to the battery life of the scanner. The scanner must be charged after a shift or the next worker must wait for the scanner to be available for usage. The cordless scanners tap into usually a USB port on the computer. The barcode scanner works in conjunction with the keyboard to emulate keyboard key strokes given to the computer, but are actually sent from the wireless scanner.

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