Does anyone know how physics is related to bar code scanners?

This is for a paper in my conceptual physics class. I cannot have too much information. I've already searched google, yahoo, and looked on wikipedia. I have found some basic info about bar code scanners but I am looking for the physics behind the bar code scanner more than anything.

Does anyone know how physics is related to bar code scanners?
It is a HeNe laser that reads the barcode... that's a pretty strong physics connection.





Aloha
Reply:Scanners or barcode readers used with the correct software can 'input' text, numbers near enough anything.





They do this by using Optical Character Recognition (OCR) software which allows the computer to convert the 'image of text' into the actual text.





Top of the range OCR software, used in conjunction with a quality scanner can scan a page of standard text in a matter of seconds to a very high degree of accuracy, which makes a great time saving in comparison to typing.








How OCR software works.


When the scanner scans the document, it is read as a series of black and white pixels.


The OCR software interprets the bitmap of pixels created, identifying each character's


outline.





The OCR software tries to match each character's outline in the bit map against 'character templates' stored on disc.





With unidentified characters, the OCR software uses other information such as the character's height, number of lines, curves and from this, it best-guesses the characters.





For the remaining characters which the OCR software cannot recognize, it substitutes the unknown character with a distinctive symbol such as ~ or @.





The finished information is normally able to be saved in a number of different file formats so that different applications packages can read it.





Scanners come in other forms that are used in a variety of circumstances.





For example at Supermarket's Point Of Sales (Checkouts) the data on bar codes is quickly and easily extracted using a scanner.





Each bar code is made up from a set of bars of varying thickness and separation distances. The numeric data coded in encoded in these characteristics of the bar.





The light source sends out the light and the light detector senses it 'bouncing' back, produce a corresponding set of binary pulses which give the numeric data that the bar code represents.





Bar codes are easily and quickly re-scanned should there be an error. Although error rates are very low, unwanted marks or blemishes on the bar code can cause errors.
Reply:The simple answer is that barcode scanners work by sweeping a laser across the barcode to detect the pattern based on where the light is reflected back; black bars reflect less light than the white spaces. Once the barcode is read, product information is retrieved from a computer database. The physics involved is spectrography using only black and white rather than the full spectrum of colors. This way different patterens and combinations of black and white lines can denote different product codes.





I hope that was what you were looking for.


Good luck!!