Re: [ATM] Exit pulil and brightnees

[Alexis Cousein <al@sgi.com>]

George Nikolidakis wrote:
>> Theirs. *All* the parallel ray bundles for all of the objects
>> in the field pass through the exit pupil, and all are vignetted
>> by the eye's pupil.
> I thought that the parallel rays simply form the central part of the field
> view thus there is no vignetting for them. 
> 
You think wrongly. The on-axis object has a light bundle that
is parallel at the entrance pupil, is focused to the no-axis
focal point, and becomes a parallel light bundle again behind
the eyepiece.

An off-axis object has a light bundle that is parallel at the entrance
pupil but entering at angle A, is focused to a point on the focal plane
some distance away from the axis , and exits the eyepiece as a parallel
bundle again, but ideally at an angle A*magnification or tan(A)*magnification
(depending on whether you want to correct for zero angular magnification 
distortion or zero pincushion distortion).

All the exit bundles (the infinite number of exit bundles, one for each point in 
the field, *all* parallel ray bundles) have the same width,
and they all pass through the exit pupil.

That's where you place your eye's pupil to catch all the parallel ray bundles,
and then the eye lens focuses each ray bundle with a given angle to a point
on the retina.

I don't know how to explain it better. There are tons of drawings showing the
principles, but I can't write them in ASCII text.


-- 
Alexis Cousein                                  al@sgi.com
Senior Systems Engineer/Solutions Architect     SGI/Silicon Graphics
--
<If I have seen further, it is by standing on reference manuals>

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