RE: flatbed scanhead in rotating camera

[JCR <jcr@xxxxxxxxxxxxxxx>]

Hi Mike,
I think you have sent this message to me by mistake.
Best wishes,
John

-----Original Message-----
From: Mike Sinclair [mailto:sinclair@xxxxxxxxxxxxx]
Sent: 22 June 2000 07:32
To: 'panorama-l@xxxxxxxxxxxxxxxxx'
Subject: RE: flatbed scanhead in rotating camera

I think you're on the right track but may run into some problems. To get
scanner software/firmware to move the sensor head farther than the factory
length of the bed itself is next to impossible (but if you do, PLEASE share
it!). As one vendor put it to me "why would you want to do this? It will
just bang the motor against the stops (he was speaking about the factory
flatbed use)". One solution is to re-gear the timing belt so the total
traversal of the equivalent length of the flatbed is never exceeded. There
are a number of vendors that carry these small parts for a reasonable price
(Sterling, Small Parts, Inc, Stock Drive, etc). Most use an 80 pitch belt.
Just calculate the gear ratio required for a full traversal of the film
plane or 360+ in the case of a rotating lens camera.

Another thing that probably won't work that was suggested is putting the
flatbed scanner "as is" in the film plane - you don't have a real image!
You'll need something for the camera to produce a real image like ground
glass....but this is a BAD way to do it. Instead, put the tricolor CCD
sensor physically in the image plane (without the 5+ mirrors that are in the
image path of most flatbed scanners) and mechanically scan it across the
film plane. Of course this will only digitize a 42mm wide path in the image.
Use different gearing to move it the required distance to give you square
pixels - for the case of a rectilinear camera with a flat film plane.

Most linear CCDs are TRUE RGB sensors, usually with a 42mm long image
length, with SEPARATE red, green and blue strips - no bayer patterns to mess
with cross-chroma-luma artifacts!). As for IR, use an IR-cut filter (Edmond
Scientific, Inc) somewhere in the optics path. Be careful that the total
angle subtended by the image passing through the filter at this location is
not very wide as these filters are usually angle dependent (dichroic or thin
film interference type) and will yield a color shift from center to edge of
the image on the CCD.

Hope this helps.

-Mike-

> -----Original Message-----
> From: Clayton Tume [mailto:tume@xxxxxxxxxxxxxxx]
> Sent: Tuesday, June 20, 2000 5:41 PM
> To: panorama-l@xxxxxxxxxxxxxxxxx
> Subject: Re: flatbed scanhead in rotating camera
>
>
> Andrew D and Joe.....thanks for the replies...I've got my
> computer friends
> looking into the aspect problem, they don't think it will be
> too much of a
> problem telling the scanner software driver to run past where
> it thinks the
> page ends......but we'll wait and see!
>
> I'll keep you informed
>
> Clayton
>