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

Words of wisdom

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.
Karyudo
Posts: 35
Joined: 14 Jun 2009, 01:51
E-book readers owned: iPod Touch
Number of books owned: 0
Location: Vancouver, Canada

Re: Words of wisdom

Post by Karyudo » 18 Jun 2009, 14:13

From a geometry point of view, I really like the idea of the cameras being mounted rigidly wrt (with respect to) the platen.

Right now, it seems like people are using camera adjustments that can't separate aiming point (i.e. centre of the page) and image size explicitly, and without introducing some skew. To get the sort of acceptable aim/angle/size wanted, people are looking at 6DOF arms. Obviously this produces good results when set up right, but it seems fiddly to get the camera aimed properly, and it doesn't seem very repeatable. Also, any skew has to be removed by software.

To have the best possible scans (ignoring reflections of the camera itself for the moment), I would expect that you'd want to position the camera exactly square to the centre of the page, so that any spherical aberration (barrel distortion?) affects the edges about the same all around. Also, it's got to be best to move the camera as far away from the page as possible, and then zoom in—optical zoom only, of course—to get the view with the squarest possible edges (i.e. smallest amount of spherical aberration). This is what I'm pursuing by tabulating view angles and heights for the A590.

To put this into practice and get fine adjustment on the size of the page, you'd really want the camera to travel along an axis perpendicular to the centre (or pretty close to centre) of the book. To have the ability to accommodate different size books, you'd also have to be able to move the axis closer to or further away from the bottom of the platen V. If I'm counting right, that's only 2DOF, and it implies a 2D orthogonal coordinate system that's 45° to what everybody has been using thus far.

I'm guessing it would be somewhat more difficult to implement my alternative take on this, but I have to imagine it will pay dividends down the road, in terms of setup time and repeatable scan quality.

In my purely conceptual design thus far, I'd have a linearly-moving platen cantilevered with drawer slides from a central light-and-platen support at the back, and adjustable camera mounts following my rotated coordinate system fixed rigidly to the sides of the platen. Whaddya think?

(I realize I'll have no credibility at all until I can either draw or build something to illustrate my points, and gain some cred as a builder...)

spamsickle
Posts: 596
Joined: 06 Jun 2009, 23:57

Re: Words of wisdom

Post by spamsickle » 18 Jun 2009, 14:48

In theory, I expect I'll want the "film plane" of the camera to parallel the "page plane" of the book it's photographing, so I'm currently planning on using a couple of angle brackets to give me the same 45-degree pitch the sides of the platen will have.
bracket.jpg
bracket.jpg (52.66 KiB) Viewed 4649 times
But your "fixed so they don't move" comment made me think -- I probably don't need that screw between the brackets. There isn't any need to adjust this angle that I can see. Six degrees of awesomeness? Pfffft. I'll take no degrees of awesomeness, if it will give me consistent, reliable, repeatable rectilinear page pics. If I had a welder, I could just tack those brackets together, but since I don't, there's probably some kind of epoxy or bondo that will do as well.

I"ll probably go with the screw initially (because there's likely something I'm overlooking), but this is my plan right now.

spamsickle
Posts: 596
Joined: 06 Jun 2009, 23:57

Re: Words of wisdom

Post by spamsickle » 18 Jun 2009, 14:53

daniel_reetz wrote:I really need to email Ian from the BKRPR group again. A book scanner with cameras mounted on the platen would represent a kind of hardware middleground for our designs.
Yeah, it's too bad they don't have a forum there, the lack of one severely limits collaboration.

User avatar
daniel_reetz
Posts: 2786
Joined: 03 Jun 2009, 13:56
E-book readers owned: Used to have a PRS-500
Number of books owned: 600
Country: United States
Contact:

Re: Words of wisdom

Post by daniel_reetz » 18 Jun 2009, 17:51

They have a Google Group but it's pretty quiet. I think (and I suppose this is now obvious) that a forum is a much better approach.

jradi

Re: Words of wisdom

Post by jradi » 18 Jun 2009, 18:45

I almost forgot about that laser thing. Hmm.... Now I want to think of cool laser projects...

jradi

Re: Words of wisdom

Post by jradi » 16 Jul 2009, 07:05

My design for the arms used two ultrapods (http://pedcopods.com/) that attached to vertical arms. I've had great luck with these as pocket tripods and I used to love them. That is, until this project.

My cameras mount is located off to the side, which makes it want to tilt down against the base and unscrew itself. No matter what I do, I can't get these things to hold firmly enough for the course of 10-15 minutes. I think they just weren't designed for that. They're great little pocket tripods for a quick shot, but not so great over a long period of time. Hopefully, I'm going to try that double L-bracket idea (shown above) a shot. If that doesn't work, I'll just have to redesign my arms before I do any more scanning... (6DOAA?)

Post Reply