fbonomi's build

[fbonomi]

I still do not have a clear project, but I am starting to think about building a scanner.

My main guideline is: I want a simple design.
- I don't have too much time to spend on the project.
- whenever possible I scan using a ADF scanner cutting the books' pages (faster and higher resolution pictures), so I won't be using it the camera-based scanner that much.

I am at a very early phase, for the moment I will just post here the material I collect and the ideas I have...

What I already have:
- Two Canon A570IS. I already happen to have two of them because they are my workhorses for fiddling with CHDK
- A remote trigger. I will either split it to use two cameras, or build another one...

[fbonomi]

Other things that I (almost) have.

1) A video-to-USB interface (on its way from Hong Kong)

At $11.31, it seems the cheapest way to connect the two cameras to my laptop that will be used as a display for the cameras
(it actually connects 4 video inputs, I will only use 2 of them)

2) glass for the platen

The glass from two clip frames seemed the simplest way to have a pair of nicely-finished glass plates.
I went for the size of 24cmX30cm (abt 10"x12") so that I would be able to scan up to an A4 page

[Cabe]

I have that exact USB interface, bought for the exact same purpose (once I get my cameras) it seems to do the job nicely but gets a little laggy with all 4 inputs running (goes down to about 5FPS).

But that's not too much of a problem.

[daniel_reetz]

Cabe, what kind of software is used to display the video? Do you think it would work on an old 900mhz Pentium laptop?

[fbonomi]

Cabe, what kind of software is used to display the video? Do you think it would work on an old 900mhz Pentium laptop?

I think it requres USB 2.0 ... do you have that?

Otherwise, the thing is bought here:

http://www.dealextreme.com/details.dx/sku.11127

I have read this should be its software:
http://www.szforwardvideo.com/support/Supp_7_3.html

If it's really the same thingy (excap002 vs easycap002), then you can find here its requirements:
http://www.szforwardvideo.com/product/Pro_15_6.html (website only works in IE)
it says "P4 1.7GHz CPU or above"

On the other hand, it seems you can use it with other sofware (i.e. just install drivers, and use another, lightweight software)

I have that exact USB interface, bought for the exact same purpose (once I get my cameras) it seems to do the job nicely but gets a little laggy with all 4 inputs running (goes down to about 5FPS).

That's even more than I expected. Judging from comments on that site. I thought one had to switch from one input to the other. See for example:
http://www.dealextreme.com/forums/Defau ... adid.96939
and
http://www.dealextreme.com/forums/Defau ... adid.65249

[Cabe]

Havnt tried it but anything with the words video in the title need USB2.0 and just throws a fit.

WTR to the software its note hugely resource intensive but because it uses USB that hits the CPU as well.

[fbonomi]

At the moment, I am thinking about a structure similar to this one:

[fbonomi]

Trying to size the thing up, I have ran into two conceptual but very basic problems...

A: 2 degres of freedom.
This structure gives me two degrees of freedom, allowing to
1) move the camera nearer/farther away from the platen
2) move it laterally to be directly over the center of the scanned page

On this point I have seen wildly different opinions, ranging from 6DOF to much simpler structure where you even can't move the camera nearer/closer to the page.

Do you think this structure has obvious drawbacks I haven't thought of?

Is it too basic in its lack of flexibility?

B: Zoom level
The zoom level changes the way the pages are formed. Without having done any practical test, I guess that we have:
- Zooming out gives less (barrel/cushion) distortion but might give less crisp images
- Zooming in gives again less crisp images
- A mid-way zoom gives highest detail in images.

On the other hand, you can't really play with zoom if you can't move the camera closer/farther away from the page, which (if Iunderstand correctly) isn't a problem many feel as important.

For example, here: viewtopic.php?f=1&t=87#p843
you1 doesn't consider zoom/field of view factors...

What do you think about this? Am I being overzealous?

thanks for any advice.

[fbonomi]

Interesting stuff here:
http://www.imaging-resource.com/PRODS/A ... 70ISA4.HTM

(tests being made with an A570 at 35 and 140 mm..)

[spamsickle]

I'm one of those with the "One degree of freedom" setup, and I'm very satisfied with it.

My camera is attached to the platen, and moves side-to-side only. The distance to the page being photographed is the same from one book to the next, which means the focus doesn't have to be adjusted. I load the book, center the camera, adjust the zoom to get a good page image with a bit of black around the edges, and start shooting.

I don't have video monitors attached to the cameras, and depend on the tiny LCD display to do the setup, so having fixed focus every time is important to me. I haven't noticed any barrel distortion in any of the images, but I don't think I'm the kind of person who would. The big problem I'm noticing is with getting the pages evenly lit, but that doesn't have anything to do with the camera setup.