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From: "Dave VanHorn"
Subject: Re: Designing a barcode reader
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Date: Sat, 28 Sep 2002 21:21:30 GMT
> A lens will focus the resulting barcode onto
> a phototransistor with a metal sheet wrapped around it with a small
> in the middle.
This is typical of imaging optics. Lots of light, and basically a camera.
Many pens are non-imaging, with offset emitters and detectors focussed
through a spherical sapphire lens. If I were you, I'd buy the optics from
someone. Lots of mess there you don't want to get into.
>Is this how most barcode wands work, or do they use fiberoptics to route
the light around?
I haven't seen any commercial units using fibers.
> Main programming problem to watch out for is varying stripe timing as
> the pen is tracked across the label. Can lead to 2:1 black/white
> timing variations over even just one character (wrist accel/deccel,
> muscle tremor ect).
I've never seen this, at least not to that degree.
Were you working with physically large codes?
I think the most I've seen has been about 25% within a couple chars, and
that was when we were trying hard to get the effect.
> The projects complexity is in the machine code, decoding algorithms.
> There are about 5 patented decoding methods out there. They are
> pretty much all the same and of course designed to be incomprehensible
> to anyone reading them.
:) Mine's just convoluted because I had to fit it into a kword.
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