[Raytrace] Schupmann in OSLO LT

[Anthony Stillman]

A short while back Ellen Mackenzie asked about the Schupmann Medial
Telescope, its prescription, and entering it into OSLO LT.

Recently I've once again been experimenting with OSLO LT.  I determined to
assist.  I started by searching the archive to find the link she
referenced.  Instead I found a post I had written.  Oh yea, I thought while
reading it.  I guess that means I've got a .len file somewhere.

After several searches (check the spelling) "shup04.len" surfaced.  It's
text is below.

This model takes advantage of the non-physical quality of ray tracing.
Namely, surfaces interact with the rays only where they are called out.  A
ray passing through a lens and then reflected by a mirror back toward the
lens will not interact with that previously called out lens.  It is as if
it isn't there.   Consequentially, there is no need to tilt the optical
axis at the field mirror or mangin.  Instead I send the light back on its
self and in turn place the mangin where it appears to be in the income
light cone.  The tilt required in a real schupmann only slightly perturbs
the behavior of the instrument and can be ignored.

Yea, I couldn't either.  To add tilt to the OSLO LT model open the surface
data spread sheet (F5).  The third surface is the field mirror.  Click on
the "Special" button and select "Coordinates" in the pull down menu.  There
set "TLA" to 3 or so degrees and set "Tilt and Bend" to "Yes"  Finally,
click the green check at the top left corner of the "tilt/decenter" data
window.  You can now run through the available metrics and see that the
effect of the this tilt is negligible.

Tilting the mangin proceeds similarly.  Tilt the refractive surface
(surface four) as as you did the field mirror.  For the reflective surface
(surface five) use the minus pick up function in the "tilt/decenter" window
to tie it to the previous surface.

Tilt in the mangin strongly effects the behavior of the instrument and it
should be kept to a minimum.  With out a fold flat just shy of the focal
plane to kick the image out of the way of the field mirror, that minimum is
around -0.5 degrees.  With the fold flat -0.3 degrees looks doable.

Tilting the mangin seems to mess with OLSO LT's autofocus function.   With
the mangin tilted the best focus moves back a couple tenths of a millimeter.


Anthony


scientia est potentia.
Knowledge is power.






// OSLO 5.31  8046     0     0
LEN NEW "Schupmann Medial" -2310.1 8
EBR  76.2
ANG  0.25
DES  "OSLO"
UNI  1.0
// SRF 0
AIR
TH   1.0e+20
AP  4.3633508207e+17
NXT  // SRF 1
GLA BK7
RD   1295.3238
TH   15.875
NXT  // SRF 2
AIR
RD   -13513.5112
TH   2272.284
NXT  // SRF 3
RFL
RD   -1618.107
TH   -1240.9932
NXT  // SRF 4
GLA BK7
RD   339.6742
TH   -11.43
NXT  // SRF 5
RFL
RD   664.0068
PK THM  -1 0.0
NXT  // SRF 6
AIR
PK CV   -2 0.0
TH   1245.9462
NXT  // SRF 7
AIR
NXT  // SRF 8
AIR
TH   10.4158133927215
CBK  1
WV 0.58756 0.48613 0.65627
WW 1.0 1.0 1.0
END  8