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iPod based prototype

Posted: 06 Nov 2011, 16:36
by JellyRobotics
** EDITED POST - Since posting this, I've given up on my one-camera scanner quest. I really like the aluminum design (http://diybookscanner.org/forum/viewtopic.php?f=1&t=495) and have ordered parts to begin a build similar that **

I've looked through many (not all) of the projects to see if anyone else has tried this. Seems like my proof of concept works. This project uses a single iPod or iPhone with it's built in front and back facing cameras. I'm not that handy with hardware so this is a very early stage proof of concept mostly glued together. Cost so far is under $30 (not including iPod). I need to re-mount the mirrors so I can fine tune the horizontal and vertical tilt but the alignment images I've done so far look promising. Since I've been developing iOS apps for about 3 years, writing an app that will transfer the images to a mac for OCR or builds a PDF directly from images during the scan will be pretty easy.

Re: iPod based prototype

Posted: 06 Nov 2011, 20:30
by vitorio
The iPod/iPhone in the middle is actually taking pictures of the mirrors, which have a reflected image of the book?

You mention the front-facing camera; remember that that's only VGA resolution, not the 5MP (iPhone 4) or 8MP (4S) of the rear-facing one. Photos taken with the front-facing camera won't be good enough for reproduction or OCR, or even reading in some cases.

Older iPhones and iPods have fixed-focus rear-facing cameras, needing 18" or more space between the lens and the subject.

You might also look at some document scanner designs for reference:

Re: iPod based prototype

Posted: 06 Nov 2011, 22:05
by JellyRobotics
Very good points. The images looked OK with my alignment pages but I bet if I was photographing text I'd see what you are talking about. Oh well, what about the more traditional design (without mirrors) and 2 iPods instead of cameras? Is 5MP high enough resolution because it would still be easy for me to code an app on the iPhone/iPod to take the images and transfer them or build a pdf.

Re: iPod based prototype

Posted: 06 Nov 2011, 23:12
by vitorio
JellyRobotics wrote:Oh well, what about the more traditional design (without mirrors) and 2 iPods instead of cameras? Is 5MP high enough resolution because it would still be easy for me to code an app on the iPhone/iPod to take the images and transfer them or build a pdf.
I think there are other threads talking about recommended resolutions, but it really depends on what you're trying to do with the scans. If you don't need OCR or to republish the scans, lower resolution is often fine.

What about swiveling the iPod so the rear camera can take one photo of one mirror, and then rotate around and take a photo of the other mirror?

Re: iPod based prototype

Posted: 06 Nov 2011, 23:19
by JellyRobotics
I went with the mirrors because I thought it would be more stable than rotating the iPod but I think that's what I'll try next. I'll still ditch the mirrors and just rotate the iPod with a servo. I wanted to use servo's for a page turner anyway so one more on the iPod mount won't hurt. Thanks for the input...would have sucked to go too far with this to find out it really wouldn't be very good.

Re: iPod based prototype

Posted: 07 Nov 2011, 11:18
by Tim
Have a look at pagescanner. It's an app that was developed for iOS devices to more or less automate the book scanning process and even do some ocr. It makes pdfs too. Since it can assemble right and left pages after they are taken all you would need to do is scan the left pages first, move your camera once, then scan the right pages. Of course that doubles your page flipping so your servo method could eliminate that, but it might introduce a bit of misalignment.

Here's the thread on pagescanner:
http://www.diybookscanner.org/forum/vie ... ?f=3&t=451

Re: iPod based prototype

Posted: 07 Nov 2011, 15:39
by darrinjk
I have though before of using mirrors to eliminate one camera, but to maintain fast speeds. The idea I had was to use one mirror on the left, and to have the camera on the right in its usual position, but that also moves up to take a shot at the opposing mirror. This of course has problems (constant refocusing, the right page at this mirrored angel would not be a perpendicular shot, etc.) but also helps with the lighting problem you would have with the above model. The model you have with two mirrors would make it difficult to place lighting so that your not casting shadows or uneven light. I suppose with stable, automated camera movements, good refocusing, and dewarping software could make it possible, but it would probably be more trouble than it's worth and not an ideal solution just to avoid a second camera.

Re: iPod based prototype

Posted: 07 Nov 2011, 15:59
by JellyRobotics
I've also ordered 45deg prism just to experiment with other possible single camera ideas

Re: iPod based prototype

Posted: 07 Nov 2011, 16:10
by darrinjk
It would be awesome if through the use of prisms/mirrors we could get the 45 degree angle of the book pages to a virtual 180 degree image for the camera to take one shot of. the mirrors them selves would not be 180, but the perceived image would be.

Re: iPod based prototype

Posted: 08 Nov 2011, 20:04
by JellyRobotics
The prism doesn't do me any good. It does allow for a much smaller amount of movement to shift from page to page but it still warps the pages on the edges. A prism large enough to avoid that would probably cost more than a second camera. I'm going to ditch the mirrors and give up on my one-camera quest. Hopefully I'll post again after giving my best shot at an aluminum build similar to http://diybookscanner.org/forum/viewtopic.php?f=1&t=495.