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

Tue Feb 16, 2010 3:37 am   

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

Tue Feb 16, 2010 5:05 pm   

On Mon, 15 Feb 2010 18:28:31 -0800 (PST), jcomeau_ictx
<john.comeau_at_gmail.com> wrote:


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

Tue Feb 16, 2010 7:43 pm   

In article <db5d5e4f-b14e-4871-be74-3c6db24cfd58_at_m35g2000prh.googlegroups.com>,
jcomeau_ictx <john.comeau_at_gmail.com> wrote:

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 mzenier_at_eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Tue Feb 16, 2010 7:47 pm   

jcomeau_ictx wrote:


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

Wed Feb 17, 2010 12:36 am   

On 17/02/2010 5:47 AM, John Sutter wrote:


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.