can an iPod Touch screen be recognized by a laser scanner?

I had this maybe-brilliant idea to consolidate all my cards with barcodes (Safeway, 24-hour Fitness, Petaluma Library, etc) by making the barcodes display on my iPod Touch. I got the barcode program working, but went to the gym today and the guy tried to scan it... no luck. Double-checked the barcode itself against the one on my membership card, it seems to be correct. So the problem is more likely that the laser scanner does not see the black-and-white on the iTouch screen the same way my eye does.

So... the question is: is there a way to make this work, say by using red/green instead of black/white? Or is the whole idea unfeasible due to the characteristics of the hardware and optics, of which I know next to nothing?

Thanks in advance for any clues! -- jc

Reply to
jcomeau_ictx
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Bar code reading depends on the size/spcing of the bars and the contrast ratio. If you can set the iPod screen to a hard black/white contrast with little or no gray (think: lumps of coal on fresh snow), then it *might* work. I tried this some years ago with Palm devices and never achieved satisfactory results.

John

Reply to
news

A scanner that uses an array of photosensors may work, you'd probably need use black/same color as the bar code unit's illuminator.

Bar code units that use a scanning laser and a single photosensor will F-UP when they try to read an actively illuminated display where the display refresh has no relationship to the laser scan.

An externally illuminated E-ink display might work. Got a Kindle?

Scanned bar code readers usually show a sharp (red) line, array based ones just general illumination (usually red, too).

Mark Zenier snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

Reply to
Mark Zenier

Generally speaking, scanning barcodes on displays that give off their light does not work for laser barcode scanners, though it will work with imaging scanners. You can scan barcodes from reflective LCD displays using laser scanners.

Laser barcode scanners work by analyzing the reflected laser light which is modulated by the barcode as the laser scans across. Other light is filtered out.

You could always print out the barcodes and stick them to the back of your device. Sort lacks the coolness factor though.

-- John

Reply to
John Sutter

Some work both ways. We have scanners here in Australia at one of our convention centres that can deal with either printed barcodes, or barcodes sent to your cellphone. Yes, the cellphone issue is a bit 'iffy', but it works frequently enough to warrant using it as a selling point.

Reply to
John Tserkezis

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