Re: [ATM] Luri-Houghton prescriptions.

[Richard <cnc@cncservo.co.uk>]

Hi Bob,

Thursday, October 13, 2005, 1:52:15 AM, you wrote:

BM> I've been playing with the Lurie-Houghton prescription on the two
BM> lenses and seem to find that the equal radius pairs of curves
BM> doesn't seem to do the best job.

No, obviously not, but the point of the the LH design is to
minimise the amount of work and complexity to achieve a
reasonable result, but with only 2 degrees of freedom for
optimisation. If you allow 4 radii rather than 2, an air gap,
and different glasses for the two parts, then an optimiser now
has 7 degrees of freedom to get its teeth into. Once you allow
those DOF's, the thickness of the elements come into play and
you have 9 DOF's.

-- 

Best regards,
  Richard in the UK

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