How do handheld barcode scanners read barcodes?

[KingNothing]

Does anyone know the workings behind those little scanners that department stores use...you know, the ones that they can take off and aim at the barcodes on heavy things?

I know the barcodes themselves with the thickness of the lines and stuff represent the number that usually appears right below them.

How do the scanners pick that up so well? Also, why when something won't scan, does it always work best to aim at the barcode and slowly draw your 'scanner' away from it?

 

[pallidin]

In general, a laser beam is emitted from the scanner, and that beam is rapidly swept back and forth against the barcode using electronics/mirrors internal to the scanner.
Hand-held scanners typically(I believe) need to be in a general perpendicular orientation with the barcode in order to read it. I have seen counter-embedded scanners that use rapidly rotating mirrors to create a scan field of 6-12 different angular "lines" which seems to handle nearly any orientation of the barcode.
The "aim at the barcode and slowly draw you scanner away from it" is an issue I am not certain about, though I suspect that it can work in hand-held scanners that lack sufficiently sophisticated circuitry to deal with some barcode printing/package overlay(plastic wrap) situations.

 

[PRodQuanta]

Yeah, they are usually just your eveyday HeNe laser.

Paden Roder

 

[KingNothing]

I am hoping the 'draw slowly away' can be explained at some point. It works the best even when there's no plastic whatsoever. I don't quite get why...I'm looking online for explanations.

 

[KingNothing]

Alright, here is what I came up with.

It works better that way, because when you go from close to far, it slowly allows more light and therefore better reflectivity onto the barcode.

Hell if I know. Right now its basically a phenomenon.