Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Footsie Bookscanner

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.
dpc
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Location: Issaquah, WA

Re: Footsie Bookscanner

Post by dpc » 18 Jun 2015, 15:04

That looks much better Malcolm.

Camera alignment is slightly off as noted by the slight skew at the top of the page.

I see what appears to be an overly bright spot near the bottom of the page over the word "brusquely" but perhaps that's actually on the page? Tip: if you put a solid black piece of paper over that page (under the platen) and take another shot you should be able to easily identify any sort of reflections making their way to the platen surface.

wmalcolmk
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Number of books owned: 500
Country: England

Re: Footsie Bookscanner

Post by wmalcolmk » 25 Jun 2015, 10:51

Camera Aiming

I've decided that my scanner must be able to fill the camera image from books of all sizes upto A4. This means that the camera must be adjustable in six degrees of freedom - up/down, left/right, in/out, roll, pitch, yaw (thinking rotation in aircraft terms). My current design has two adjustments missing - up/down, and roll. I've changed the design to give this capability, as can be seen from these photos.
C Bracket1.JPG
C Bracket1.JPG (48.99 KiB) Viewed 3500 times
C Bracket2.JPG
C Bracket2.JPG (71.22 KiB) Viewed 3500 times
Malcolm

duerig
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Re: Footsie Bookscanner

Post by duerig » 25 Jun 2015, 11:16

One suggestion that I have is that you use cameras that get you a dpi you are happy with and then adjust them once and never touch them again. Changing zoom level and all the other adjustments based on the book size will quickly become very time consuming. And it is much nicer to get things absolutely right just once.

-D

wmalcolmk
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Joined: 12 May 2015, 04:39
Number of books owned: 500
Country: England

Re: Footsie Bookscanner

Post by wmalcolmk » 25 Jun 2015, 13:07

Thanks for the advice. Which part of the adjustments do you find the most time consuming? I expect to disassemble my scanner fairly frequently, because of space constraints, and for demonstrations off site. I would like to design it so that the most awkward adjustments can be done quickly.
Malcolm

duerig
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Re: Footsie Bookscanner

Post by duerig » 25 Jun 2015, 13:35

For me, the whole process was incredibly awkward. Especially looking at a tiny screen and trying to see if all the lines really seem to line up. One thing that I found particularly difficult was the last finetuning of keystoning and the rotation of the camera. It was really hard to tell whether the straight line was not quite horizontal because I needed to rotate the camera one way or another. Especially on a tiny screen on the back of the camera at an awkward angle.

I have thought that it might be nice to come up with a software package that takes pictures of a callibration sheet (chessboard, maybe), and then give hints about how to adjust the camera based on that. I did something similar for callibrating laser lines and it was much easier and more accurate than eyeballing it.

*Take picture*
'Move the camera 0.1" right and rotate it 1.4 degrees clockwise around the tripod anchor axis and 0.5 degrees clockwise around the parallel axis."
*Take picture*
'Move the camera 0.02" left and rotate it..."

-D

dpc
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Location: Issaquah, WA

Re: Footsie Bookscanner

Post by dpc » 25 Jun 2015, 16:48

Look at the method described by the third post in this thread.

If your camera has a zoom lens then you can build a camera mount pretty easily that will allow a vertical translation of the camera position. Once the angle is set so that the camera direction vector is perpendicular to the platen surface it won't change as you translate the camera along that vertical axis. In this regard you won't have to worry any more about keystoning than you would with a scanner that had a static mounting position.

wmalcolmk
Posts: 24
Joined: 12 May 2015, 04:39
Number of books owned: 500
Country: England

Re: Footsie Bookscanner

Post by wmalcolmk » 26 Jun 2015, 10:24

Camera aiming using a Mirror

Thanks for the advice dpc (third post in
http://www.largeformatphotography.info/ ... lat-object )
explaining how to use a mirror for alignment.
I put together a quick test. Here are the results...
Mirror1.JPG
Mirror1.JPG (59.58 KiB) Viewed 3468 times
Mirror2.JPG
Mirror2.JPG (89.35 KiB) Viewed 3468 times
This looks a very promising technique for quick setting up after disassembly of my scanner.

Thanks - Malcolm

duerig
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Country: United States of America

Re: Footsie Bookscanner

Post by duerig » 04 Jul 2015, 23:54

dpc, thank you so much for that link! I was eagerly waiting for my mirror to arrive so I could try it out and just had a chance tonight.

The mirror-dot-lens alignment technique worked out pretty well for me as well. I played around with it for a long time, trying to get a feel for exactly what it aligned and how. Aligning the dot and lens-in-mirror gives you a pretty good rough alignment. And then aligning both of those to the exact center of the viewfinder (made much easier by CHDK grids) provides an additional fine-tuning. This then locks 4 of the degrees of freedom of your camera.

The two remaining degrees of freedom is the 'z' (distance of the camera from the platen) and the 'roll' (rotation of the camera in its plane parallel to the plane of the platen). Luckily, that degree of motion is the easiest and most reliable to correct in post-processing. But I realized that with a slight tweak to the setup, you could lock in the 'roll' as well. Instead of a dot at the center of the mirror, paint a thick crosshair on it with the lines vertical and horizontal to the platen. This lets you both exactly align the center and make sure that those lines align with the CHDK grid so that the 'roll' is aligned as well. It looks like wmalcolmk was able to align the 'roll' pretty well based on the lines they drew to center the mirror. But I think you can align it slightly better with the lines on the mirror itself.

I will play around with this some more. I need to find some permanent paint that will stick to the glass surface of the mirror. :-)

But regardless, I have one of my cameras aligned better than it ever has been now.

-D

dtic
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Re: Footsie Bookscanner

Post by dtic » 06 Jul 2015, 06:50

I haven't tried it but CHDK supports custom grids, http://chdk.wikia.com/wiki/Grids . It might help this mirror method to also put a grid line cross in the centre of the camera screen.
A fine tip CD/DVD marker pen would probably work well on the mirror.

dpc
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Location: Issaquah, WA

Re: Footsie Bookscanner

Post by dpc » 06 Jul 2015, 14:23

I'd make my own cross hairs using black thread and epoxy them to the back of the mirror.

Get a piece of cardboard (like what is on the back of a tablet) and cut it about 1/8" larger in diameter than your mirror. Draw cross hairs on the cardboard and then cut in from the outside edge of the cardboard 1/8" along the each cross hair line toward the center. These cuts will comprise the guides for your thread and ensure they are in the correct position. Put the thread across the front, through the guides and tie them in the back. Put a drop of epoxy on the knot and also drops of epoxy where the thread goes across the edge of the mirror through the guide.

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