Non-binding-breaking Book scanners (Was: Looking for PDP handbook

[Fred Cisin]

>> http://www.diybookscanner.org/ :)
> Ooh, that's pretty cool.

Yes, but, . . .
I've participated in building a few similar devices.
Instead of the two sides MEETING in a V, there should be an open area 
right at the spine to accomodate the greater thickness of the spine 
itself.  Having the two side panels able to slide up and down, with pegs, 
a few inches would accomodate that and permit a varying amount of spine 
clearance.

Lighting.  Ideally, lighting for copy work should be at a 45 degree 
(1/4PI) angle.  That way specular reflection (glare) from glass cover 
(still needed occasionally!) or even just glossy paper, is not going 
towards the camera.  If the trough faces north/south, then that can be 
done with light(s) north and south of the unit.  Using two lights makes it 
much easier to get acceptably even illumination. Some people prefer 
various forms of diffuse light, or coaxial lighting ("ring" light).

Having the camera at a fixed position relative to the work holder is great 
IFF you are doing consistent size.  Different sizes could be dealt with 
through variable focal length ("zoom") lenses, but that is not always the 
ideal solution.  I like to use FLAT-FIELD lenses, which are generally 
fixed focal length (sometimes called "primary lenses").  Enlarger lenses 
are an extremely cheap source for those.  Being able to move the 
camera/work distance closer/farther requires a movable mount to change 
distance, but keep the camera centered relative to the work.  North/south 
motion can be easily handled by moving the book along the trough, 
preferably with a fence, or simple bench-dog stops.  The other motion 
generally requires the camera mount to be a pole at a 45 degree (1/4PI 
radians) angle relative to the work.  Since the work is at a 45 degree 
angle from vertical, that means that the pole can be VERTICAL, with the 
camera mount aimed at a 45 degree angle. The post should be offset 
slightly from the north/south center, with the movable camera mounts 
holding the cameras at 45 degree angle (preferably with the focal node 
close to that central plane).

Positioning of the book would require placing it so that it is centered 
north/south (calibration marks, as well as fence or bench-dogs, are very 
helpful!) and moving the camera up and down and focussing for distance.


NOTE: use of other than 90 degree (1/2 PI radians) for the book holder 
would require further changes!


--
Grumpy Ol' Fred     		cisin at xenosoft.com