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Another no-platen approach

Built a scanner? Started to build a scanner? Record your progress here. Doesn't need to be a whole scanner - triggers and other parts are fine. Commercial scanners are fine too.
bgalbrecht
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Re: Another no-platen approach

Post by bgalbrecht »

How well does this work with paperback books? I'm looking at a paperback that has about 1/4" top margin, and I think that would be too small a margin for a platenless frame.
sdati

Re: Another no-platen approach

Post by sdati »

Smallest margin I could find on a paperback of mine is about 5/16" - this works out ok with my latest design. It's a little tight, but as long as you look at the page before you shoot a picture, you can make any minor adjustment needed pretty quickly.

Here are the changes I made:

1) Moved to 3 "V"s instead of just two - this adds some stability and allows me to make the two support pieces ("wings" as I called them earlier) out of smaller/lighter material. So now there are 2 fixed V's and 1 adjustable.

2) Changed the fulcrum mechanism to be a little less clunky (2 bolts, one beneath each fixed-position "V")

3) Added 2 guides to help keep the whole apparatus in a fixed position relative to the book stand

4) Ran self-adhesive velcro along the bottom of the V's - this lets me then easily adjust the positioning of the side-of-page hold-down, and now I can also add equal-thickness pieces to hold down the top and bottom edges of the page. This reduces the page distortion, though there still is a little bit. I haven't compared the distortion with this method to what I might get using a glass platen

With the 2 fixed V's, it would be easy to swap in a glass platen if I wanted - I haven't done that yet, but I do have a piece from my earlier experiments that is the right dimensions - I may try it out just to compare performance with/without.

The "hinge" mechanism seems to work very well overall - it takes me about 4 seconds per page turn, and then another 3 seconds to move to the camera, shoot, and move back to turn the page again. If I had some sort of trigger mechanism, I could probably get down to about 5 seconds per page turn... so really pretty quick.

The whole new setup:

Image

Velcro under the "V" to hold on the extra pieces:

Image

Adjustable fulcrum points, rubber-band hinges, and guide posts to keep things aligned (I'm still not sure whether the guides are useful/necessary - right now there's too much slop between the posts and the "V"s, so they don't do much. I can see them being useful for the narrow-margin case though):

Image
Tim

Re: Another no-platen approach

Post by Tim »

This is really a great idea, and pretty much exactly what I was looking for. I'm not really excited about the complexities of building a glass platen or dealing with the reflection issues. I never would have thought the rubber band hinges would work, but from your video it sure seems to. Your design certainly has the advantages of being very cheap and less complex than some of the others, and I really like that aspect.

For the cost of some extra cost and complexity you could go with the vertical drawer slide design to pick up the top platen and more drawer slides to allow the bottom platform to slide sideways to accommodate moving through the book. That would eliminate having to adjust the rubber bands, but the extra complexity may not be worth it for that unless you plan on doing a lot of books.

You may want to consider manual focus and settings so that you don't have to rely on and wait for autofocus, etc each time. The camera will remain the same distance from the page, so you shouldn't need to change the settings. I'm no expert but I've read many good suggestions here on the forums about that and white balance, exposure, etc. even on point and shoot cameras.
StevePoling
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Re: Another no-platen approach

Post by StevePoling »

the jury is still out on my theft/implementation of your idea. I've scanned one book so far using it and it is better than my last platenless approach, but I'm still unsatisfied with it.

However, there's one thing that's worked out very well I should tell you about. I bought a sheet of Teflon from SmallParts.com and cut it into 3/4" strips of 3-4" in length. I glued each strip onto the v-shaped members right where they go into the gutter of the book. The slippery nature of Teflon helps the pages slide out of the way. Scuff up one side of the Teflon to give the glue something to bite into, and then use contact cement on it and the v-shaped members.

I didn't think of using Velcro for the additional hold-downs. I tried adhesive-backed rubberized-magnet strips and steel flat stock, but I couldn't get strong enough magnets and thin enough steel. I did without the additional hold-downs and just smoothed pages by hand.

I'll post some pictures...
sdati

Re: Another no-platen approach

Post by sdati »

Tim - I don't think I'll go with the drawer-slide approach, because I want this to be very portable and lightweight. I don't have room (well, technically I do, but I'm trying not to fill it up) for a vertical riser or a heavy/larger base. I'm still thinking about this a bit though, and I may come around eventually. Every piece that I add also adds the possibility of more shadows, which is one of the nice things with the current design - the only shadows come from the "V"s and they are small enough that they don't usually cause trouble. As far as manual focus, I'd love to - but my point-and-shoot camera doesn't even give that as an option. I do disable the flash and turn on macro mode in order to allow it to focus well at such close distance. In the last book I scanned (about 550 pages), I only came across two that were visibly out of focus.
sdati

Re: Another no-platen approach

Post by sdati »

Steve - what do you find to be better about pictures with the glass platen vs. without? I'm going to try with the glass myself, but I'm curious what your experience was. Everything I tried with glass came up with terrible glare, or required me to add more light sources - without the glass, I can shine a light almost directly on the page if I want, and don't have to fight the reflections... so I just set up directly beneath my living room light and away I go.

There definitely is more page warping than I'd expect - things look very good until I get the pictures off the camera, and then it's obvious that there are little uneven areas on the page - I'm thinking the glass platen may really help with that, although if you take the images from bookliberator.org as representative of what you can get with a platen, I'm already way ahead of them... (http://www.flickr.com/photos/bkrpr/sets ... 057232393/)

So I'd be curious to see what sorts of images you get with and without the glass, if you have any images that you can share.

My main goal is to eventually run OCR on a lot of the texts I scan, so I can generate a clean PDF or text file that's easy to read on my iPod Touch - so the quality of the images is only interesting to me inasmuch as it affects OCR (been looking at Ocropus and Tesseract - both of which require some fiddling for best results).
StevePoling
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Re: Another no-platen approach

Post by StevePoling »

I have not yet built a platen, but I've got the plexiglass, etc. So, I can't compare image quality with the competing systems.

My platenless bookholder in action:
Image

Here's a side view:
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I think this Teflon is a good idea. But the black adhesive rubber-magnet is too weak to be any good:
Image

I have a problem with keystoning. I think it is that I have to hold the cameras high enough to clear the two 1x2s on each side.
Image

You can see here that ScanTailor does a great job of taking this old text and cleaning it up, but it leaves the keystoning.
Image

I haven't tried to OCR this book, but on another book I noticed that the OCR tended to go off the rails at the bottom of pages like this one. Thus I think it important that some extra de-skew is needed.
sdati

Re: Another no-platen approach

Post by sdati »

Curiousity got the better of me... tried a little bit of comparison between glass platen and no-platen, tried to keep all other variables the same. I had a lot of trouble finding a location where I wasn't getting nasty reflections off the glass. I don't notice much difference on this book, but there may be some bigger differences on floppier softcover books... still tweaking:

Original pages - with glass:
Image
Image

Pages under glass after Scan Tailor (couldn't get the page header due to shadows where I set up):
Image
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Original pages - no glass:
Image
Image

Pages - no glass, after Scan Tailor (left off the page header for fair comparison with previous):
Image
Image

Here's a link to my flickr stream if you want to look at these images in larger size: http://www.flickr.com/photos/46810237@N08/
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Misty
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Re: Another no-platen approach

Post by Misty »

I've also found that it's very difficult to get good, reflection-free images with glass. I've minimized it using the angle, but I haven't found a really foolproof solution. When I have the chance to build mine, I'm looking at using a) acrylic, which has much less reflection compared to glass, and b) a polarizing filter for my camera, which can eliminate the remaining reflection. The polarizing filter probably isn't an option for the camera you're using, but acrylic may help. It's more expensive than glass, but it's also lighter in addition to having lower reflectibity.
The opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.
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daniel_reetz
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Re: Another no-platen approach

Post by daniel_reetz »

Really love what you guys are doing.
As far as manual focus, I'd love to - but my point-and-shoot camera doesn't even give that as an option. I do disable the flash and turn on macro mode in order to allow it to focus well at such close distance.
You might want to check if your camera has an "Auto Focus Lock". That's how I set my focus. Auto focus once, then lock it forever. Super-convenient, and makes the cameras more responsive.
You can see here that ScanTailor does a great job of taking this old text and cleaning it up, but it leaves the keystoning.
I hope that at some point someone can help take care of keystoning in Scan Tailor, maybe automatically as a part of the skew step. That would really improve results from all scanners.

Another thing I want to say -- I am really excited about removing the glass, but it is perfectly possible to get glare-free images with glass. The glass itself isn't the problem, really. In this case, sdati's open setup means that all the light from the room can cause glare and image issues if glass was covering the book. To get glare-free images, one either has to work in a dark room or one must cover their scanner so outside light isn't a problem. As I noted in the copystand thread, another contributing factor is the light above the platen. If you have a light up there illuminating the page, it is also illuminating the camera. Shading it from the lamp will seriously reduce glare and images of the lamp.

All that said, I think the glass-free approach is really smart and I'm really excited to see it.
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