RFID Barcode Reader
A barcode reader (or barcode scanner) is a computer peripheral for reading barcodes printed on various surfaces. Like a flatbed scanner, it generally consists of a light source, a lens and a photo conductor translating optical impulses into electrical ones. Additionally, nearly all barcode readers currently produced contain decoder circuitry analyzing the barcode's image data provided by the photo conductor and sending the barcode's content to the scanner's output port. The performance of the scanner is a function of:
Photo by Jim DeLillo
- the signal to noise ratio (determined by the laser power, the size of the laser spot, refectivity/transmittivity of the optical parts, receiving light collection area, distance to the barcode, the level of optical noise such as sunlight, fluorescent light as well as the ability to filter out that noise, etc). The laser power is usually limited by CDRH Class I/II safety requirements.
- the scan speed of the device. Basically a trade-off between decode speed and the size of the decode zone.
- the barcode (determined by difference in refectance of the barcode's alternating black & white stripes--print contrast ratio, defects, the size of the barcode, and the barcode's orientation in relation to the scanner). Generally, the laser has to pass a certain amount of the 'quiet zone' on the barcode before it hits the line patterns, in order to decode.
- the decoding circuit's ability to decode and to handle errors in the barcode, optical noise as well as the range of frequencies at which the signal is modulated.
Today's barcode scanners handle all popular barcode symbologies like EAN/UPC, Code 39, Interleaved 2 of 5 or Code 128. A special type of barcode reader is the area imager reader or 2D reader that typically uses LED illumination and a CCD or CMOS imager that operates much like a digital camera. These are necessary for decoding two-dimensional matrix codes such as Datamatrix, QR Code, Aztec Code and MaxiCode in addition to linear and stacked symbologies.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Barcode Scanner".