Another stupid question- which is more difficult to grind and figure: a very thin spherical element (or two or three depending on achro/apo, etc.) to make a high focal ratio lens, or an optical window with two parallel high quality flat faces?
Secondly, I understand the issues involved with mirrors of different focal ratios in terms of need to parabolize with fast ones, etc. How is this with lenses? Which are easier to make/figure- slow, medium, or fast ones?
All of this is with regard to my gradient index work- it may not be necessary to use a flat window, and if spherical elements are cheaper anyway (such as corrector plates) then one might want to just build on those rather than reinvent the wheel.
Thanks again.
Jess Tauber
Secondly, I understand the issues involved with mirrors of different focal ratios in terms of need to parabolize with fast ones, etc. How is this with lenses? Which are easier to make/figure- slow, medium, or fast ones?
All of this is with regard to my gradient index work- it may not be necessary to use a flat window, and if spherical elements are cheaper anyway (such as corrector plates) then one might want to just build on those rather than reinvent the wheel.
Thanks again.
Jess Tauber
