Re: Converging fields of view

[P3D Andrew Woods <andrew@xxxxxxxxxxxxxxxxxxxxx>]

Larry Berlin (lberlin@xxxxxxxxx) wrote:
> For a wonderfully detailed and revealing discussion of this topic visit
> Andrew Woods' web pages where he discusses his underwater stereo video
> system. One system uses cameras that DO converge. He evidently worked up the
> exact distortions so that the stereo scenes could be corrected for viewing.
> He has some interesting charts to illustrate the specific distortions that
> result from "converged" fields of view. The URL is:
> 
>         http://info.curtin.edu.au/~iwoodsa

Thanks for the plug Larry.  I've developed two underwater 
stereoscopic video cameras.  The first one (completed in 1991) does,
as Larry says, use converged cameras (toed-in cameras - the lens and CCD
of each camera are rotated inwards together so that their optical
axes intersect at the convergence distance).  The second camera (finished
last september) uses parallel lenses (and CCDs) and CCD offset to avoid 
the problems of keystone distortion and another distortion I called depth 
plane curvature.  (see the paper "Image Distortions in Stereoscopic Video 
Systems" at my web site for a detailed discussion).

The first camera does exhibit some keystone distortion but the amount
can be tolerated.  I can't remember any numbers off hand.  
I have not developed any equipment to actually reverses the distortion.
It is theoretically possible but much more difficult to achieve in 
practice with video images.  Some very fast digital video hardware would
be required.

It is amazing how much easier the job of aligning the stereoscopic camera
is with parallel axis cameras.  The new underwater stereoscopic video
camera with parallel axis lenses can be seen on my web site at
"http://info.curtin.edu.au/~iwoodsa/cscs" - There is also an animated
gif of the camera rotating if you can spare the time to wait for it
to download.  Have a coffee... :-)

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|  Andrew Woods   | Centre for Marine Science and Technology,      |
|                 | Curtin University of Technology,               |
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