Barcode Readers
Each digit in a barcode is represented by seven equal-sized vertical blocks. These are coloured in either black or white to represent the decimal numbers 0–9. Every number ultimately consists of four fat or thin black and white stripes and its pattern is designed so that, even if you turn it upside down, it can't be confused with any other number.
A barcode reader works by directing a beam of light across the bar code and measuring the amount of light that is reflected back. (The dark bars on a barcode reflect less light than the white spaces between them.) The scanner converts the light energy into electrical energy, which is then converted into data by the decoder and forwarded to a computer.
Barcode Reader Types
|
Pen Wand Reader |
CCD Scanner |
Image Scanner |
Laser Scanner |
|
- Simplest Reader. Durable because of the lack of moving parts and cost effective. - Harder to use as the code needs to be scanned at a certain speed and angle by the user. - Can be used in shops but outdated and slow. |
- Relatively cheap and durable as no moving parts. - Scanner is stationary, often on a wall, and barcode is moved past it. - Generally used as ID scanners. Barcode has to be within visible range. |
- Uses a camera to take an image of the barcode presented to it and uses image processing techniques to decode the bar code. - Longer range and more reliable but more expensive. Can be handheld or stationary. |
- Uses a system of mirrors and lenses to allow the scanner to read bar codes so they can read much further away and when in different orientations. - Much more expensive and less likely to be used in shops, more specialised uses. |
A laser scanner, either hand-held or stationary, does not have to be close to the bar code in order to do its job. It uses a system of mirrors and lenses to allow the scanner to read the bar code regardless of orientation, and can easily read a bar code up to 24 inches away. To reduce the possibility of errors, a laser scanning may perform up to 500 scans per second. Specialized long-range laser scanners are capable of reading a bar code up to 30 feet away.
Source: http://www.waspbarcode.com/buzz/how-barcode-scanners-work/