Re: SEM follow-on question

[T3D Andrew Woods <andrew@xxxxxxxxxxxxxxxxxxxxx>]

John Bercovitz <bercov@xxxxxxxxxxx> wrote:
> OK, so now we know George is right and you don't get
> distortion in an SEM pair by using a tilt table.

WHOA!  Hang on here.  

Am I right in assuming that a SEM images from the top of the specimen? 
and the tilt table is nominally sitting in the horizontal plane?
and the tilt axis is parallel to the SEM camera's imaging plane?
Am I also right in assuming that a SEM images in a similar manner to
the way a conventional camera operates (and not for example like
the way an Xray is taken)?

If these assumptions are correct, then this scenario is very similar
to taking a stereo pair with one camera (and shifting to the side)
and achieving convergence by toe-in.  Therefore keystone distortion and 
depth plane curvature will be present.

What has to be kept in mind however is, "What is the amount of distortion"?
Sometimes the amount of distortion isn't noticable and may not be a
problem.  Also some images are easier to spot distortion in than others.

If I'm thinking correctly, a distortionless way to achieve a stereo pair
with an SEM would be to shift the specimen from side to side.  
The equivalent of shifting the camera from side to side.

On an adminny note.  Shouldn't this list be called tech-3d and not
tech3d, the same way that photo-3d is titled...?  :-)

Andrew.


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