From: "Richard F.L.R. Snashall" 
To: Atm 
Reply-To: "Richard F.L.R. Snashall" 




CSC wrote:
 >      I like the recent OSLO triplet designs provided by Rick.  The pure
apo ray
 > trace results are exceptional. The files did not have the airy disk
included
 > in the spot diagrams, which I think is a good gauge for optical
performance.
 > Do you guys use it? It's easy to switch on using Update/Operating
 > Conditions/Spot Diagram/Show Spot.
 >

I'm using version 6.1.  If I set the parameters on the spot display to show
the Airy disk, then attempt to exit, it asks me if I want to update with
the changes.  Apparently, this information is stored with the OSLO .len
file.  I don't really use it too often, though, personally preferring to
use Strehl ratio as a measure.

 >      The matching radii are a nice feature, and would make it easier to make
 > these lenses.  I notice the f/ ratio went longer to control
abberation, and
 > the spot eventually fell inside the airy disk.
 >

Thinking of it another way, I generated the set "optimizing within the
field".  For this, I zeroed in on the off-axis angle where the Strehl
ratio is 0.8 and optimized for that angle.  The URLs for these is the same,
except using 6 instead of 4:

        http://users.rcn.com/rflrs/ed_trip6-08x.len
        http://users.rcn.com/rflrs/ed_trip6-09x.len
        http://users.rcn.com/rflrs/ed_trip6-10x.len
        http://users.rcn.com/rflrs/ed_trip6-11x.len
        http://users.rcn.com/rflrs/ed_trip6-12x.len

As I mentioned, the lateral color was reasonably good, but for those that
would want to that last 0.1 percent (and it was about that amount), I
adjusted the thicknesses of the negative elements to null the off-axis
color of the centroid:

        http://users.rcn.com/rflrs/ed_trip5-08x.len
        http://users.rcn.com/rflrs/ed_trip5-09x.len
        http://users.rcn.com/rflrs/ed_trip5-10x.len
        http://users.rcn.com/rflrs/ed_trip5-11x.len
        http://users.rcn.com/rflrs/ed_trip5-12x.len

(I know... a bit of overkill, but I'm sometimes good at that.;-)


 >      Below I include the basic design for a 5" f/15 which is nicely
diffraction
 > limited, and as close to apo as one would need. Far better than a
Standard
 > doublet. The cost should be low and the deep curves may not be too bad.
 >
 >      This was rendered in notepad, and I hope it translates back into a
*.len
 > file.
 >

With some cut-n-paste, I was able to get this into OSLO.  A question: At
565 nm, the P-V wavefront error at mid-field is better than lambda/40. 
Would you use this information to test the final result or would you find
the predicted result at another wavelength and test against that?

        Rick S.

--- BBBS/NT v4.00 MP