ASPHERIC MIRRORS AND LENS SURFACES
and HYPER FAST CASSEGRAINS
Surfaces good right to the edge!
Industry demands for increasingly compact systems has resulted in improved fabrication techniques that allow us to produce high accuracy hyper fast systems at faster speeds than formerly considered practicable. Recent work as resulted in larger size parabolic mirrors (10" to 14" diameter) as short as f/1.3 with nominal wavefronts of Lambda/4 and better. These also lead to complete Cassegrain systems of f/4.5 and possibly even shorter. We are ready to tackle these and other assignments where extreme asphericity as well as accuracy are of critical importance.
Inasmuch this is an emerging art we encourage our customers to call and make general inquiries as well specific requirements. Often, it is through considered discussion that the best results are obtained. The question of optical speed vs. accuracy is a delicate balance. Pushing the threshold is sometimes risky and results can not guarantied. But the optician's art is a constantly evolving one and through teamwork what was impossible, or considered impossible, today is tomorrow's new horizon reached.
And that good right to the edge thing is important when designing very fast mirrors. Many makers rely on grinding off the outer 1/2 or 3/4 inch to get a good edge. Very deep mirrors like this can create additional problems. For example, when making a 10" f/1.3 out to the natural edge the departure at the vertex is 196 waves. If that mirror is extended out 1/2" on the edge, making the mirror 11" in diameter, the departure increases to 289 waves; an increase of 93 waves or 53%! Put another way, one has to make a bad f/1.18 mirror to get a good f/1.3 mirror.
Additionally, our techniques do not require excessive or significant weight in working, so mirrors with conical cross-sections having thin edges can be manufactured without incurring distortion.
Finally, we work with modifications of conventional methods - unique modifications, but still just modifications. That means we work with fairly normal pitch laps on glass, not diamond turning or tiny computer controlled micro polishers that make lumpy, groovy surfaces resembling a phonograph record. Our surfaces are smooth; as smooth as any conventional optical surface.
If you have an interest in this type of optic you are encouraged to call and discuss needs and desires.
For more information please go to our Science and Industry Section