[ATM] Re: Aplantic Gregorian

[vladimir sacek <vladis.2@juno.com>]

Matt Tudor wrote:

>I have not seen yet any reference to a Gregorian Mersenne arrangement .
Is
>there any book, article, publication that treats it in detail ?

I'm not aware of such, but the design is basically simple. 
Any two mirror system where both mirrors are paraboloids 
sharing common nominal focus produces collimated beams, 
free from 3rd order coma, astigmatism and field curvature.
Secondary mirror acts as aperture stop, through which collimated
beams diverge toward primary. Axial beam is parallel to optical axis,
while beams off off-axis points diverge, according to their 
field angle. Original Mersenne uses primary mirror to 
form final image from the bundle of collimated beams
formed by secondary, but imaging element can also be refracting 
objective or (for larger apertures) a smaller 
all-reflecting or catadioptric system. 

Final aberrations in any case are determined by those of the 
imaging element. Size of aberrations will be more or less 
different than those for imaging element used alone, because
of the entrance pupil displacement.


Vlad
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