Looking for Barcode Scanner Information

Thread Starter

odm4286

Joined Sep 20, 2009
243
Hello everyone. I'm looking for information on how a barcode scanner works. I've found some explanations that state the reflected light is measured using a photo-transistor. From there, the signal is sent to an ADC which is processed in an algorithm to determine the barcodes data.

The part that confuses me is how does the scanner read the individual "bits" of data when every explanation I can find says the reflected light is processed as a whole. I hope that wasn't too confusing. Thanks for the help in advance!

P.S.
I'm mostly concerned with UPC codes
 

Marley

Joined Apr 4, 2016
369
Basically two ways. One way uses a scanner - possibly a rotating mirror or hologram. Often seen at Supermarket checkouts. A digital filter detects the unique signature of the code in the amplitude variation of the reflected beam. Usually uses a laser so the reflected beam can be phase compared with the outgoing beam. This cancels out any interference from ambient light. 1D (bar codes).

The other type uses a camera and takes an image of the code as a whole. Then uses image analysis software to decode the data. 2D matrix codes (QR codes and similar).

More information.
 
Top