robot capable of distinguishing individual pages

I have a question that could be rather far out, but potentially doable as well. I am building a robotic book scanner and I plan on using
some kind of arm to pick up an individual page in order to turn it. However, because of the nature of pages sometimes wanting to stick together, it might occur frequently that I end up picking up more than one page with my arm. I was wondering if there was a way of sensing if more than one page was lifted up. I made a rough measurement and calculation and determined that the average page thickness is .02 mm, so my sensor would need to be able to distinguish something that minuscule. Is this something that should be done optically, or would it be better to use infrared or ultrasonic methods for measurement? Even better would be a consistent method of lifting up a page that would yield an error rate of 1% and then manually rescan the few pages that were missed.
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snipped-for-privacy@keenebroadband.com wrote:

http://www.canon.com/technology/canon_tech/explanation/compact_interferometer.html Overkill? Maybe.
You could just use OCR to check the page numbers...
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On Aug 1, 4:00 pm, snipped-for-privacy@keenebroadband.com wrote:

Some ideas:
1. Hold an LED against one side of the page. Hold a sensor against the other side. Measure how much light shines through. Most paper is somewhat translucent, but two pages will block much more light than one.
2. Hold a metal plate against each side of a page. Measure the capacitance between the two plates. If you picked up two pages, the capacitance should be about half of normal.

Look at the mechanism in printers. They need to be able to pick up one page at a time from the feed tray. But they don't work perfectly, and the quality of paper they deal with is probably better than you will get from a random book.
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snipped-for-privacy@keenebroadband.com wrote:

There are many page-turning mechanisms, most of which sort of work. Nobody has one that works a very high percentage of the time and reliably self-adjusts to the books being scanned. The Internet Archive book scanning people have struggled with this.
The better mechanisms usually involve a vacuum. See, for example,
    http://www.freepatentsonline.com/20030172795.html
                    John Nagle
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Do you know if anyone has tried using a mild adhesive, like on a Post-It note? It seems like that would pick up a page fairly reliably, and if a second page was detected sticking to the first, it could be pulled loose with another sticky finger coming from the other side.
The major downside that I can see is that the adhesive would wear out after a few thousand pages, so you would need to have some way to automatically renew the adhesive if manual intervention is to be avoided.
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Bob wrote:

Yes. I found that with Google within fifteen seconds.
Please do some homework before posting questions. Thanks.
                    John Nagle
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The idea of using an adhesive might work. I read an article which described using Polydimethylsiloxane, the main ingredient in silly putty. I had previously considered using suction to lift a page, but there might be the possibility of bleedthrough picking up extra pages with the suction. Any suggestions about which of these two methods would be the best?
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--snip--
I probably missed it, since _someone_ must have posted a suggestion to use spot-vacuum-pressure to lift a page... but I'll second it anyway. <grin!>
Imagine placing a soda straw on the page and sucking on the other end. Now imagine using a flexible plastic hose, say 1/8" or 1/16" with an air pump motor on the other end and valved via a solenoid. I wouldn't think you'd need all that much suction, unless you were using 100lb paper.
Want to be sure you only have one page and not two or three? Use a copy of the same not-appearing-in-this-picture mechanism you used to guide the first hose against the page to be turned, only touch this second hose to the _back_ of the just-lifted page. If you can lift the second "hose" away from the page-or-multiple-pages without breaking the vacuum on the first hose, you just separated an extra page from the first. Repeat as necessary.
The details (and variants) are left as an exercise for the reader (translation: I think I'll step off this limb before I _completely_ cut it off <grin!>).
-- Do not follow where the path may lead. Go instead where there is no path and leave a trail. -- Ralph Waldo Emerson -- Frank McKenney, McKenney Associates Richmond, Virginia / (804) 320-4887 Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)
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Frnak McKenney wrote:

Vacuum based paper handling systems are common and reliable, but noisy, which is why they're not seen much in office environments. Large sheet fed printing presses, check sorters, mark sense readers, and similar machinery usually have vacuum feeders.
The robotics part of the problem would be to build something that looks at the book with a camera or two and figures out where and how the picking and holding devices should be placed. That would be an advance over current technology, which usually takes too much manual adjustment and watching.
Here's one made from Lego:
    http://www.geocities.jp/takascience/lego/fabs_en.html
                    John Nagle
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On Wed, 01 Aug 2007 23:00:33 -0000, snipped-for-privacy@keenebroadband.com wrote:

The usual suggestion is to use a light vacuum device to lift the page. To get the other pages to let go of the first page, put an electrostatic charge on the page being picked up.
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