[Raytrace] Waineo Null
John D. Upton
jd-upton@texas.net
Fri, 18 Jan 2002 12:35:27 -0600
Jim,
At 03:22 PM 1/17/02 -0600, you wrote:
>Just trying to learn Oslo LT. Can someone help me set it up to calculate
>spacing for the Waineo Null? An example setup would be:
>
>Pinhole (fiber optic pointing to user's right toward sphere) diameter .010
>Reference sphere (facing left) Dia = 12.5"
>Reference sphere RC=132.72"
>Knife edge is 7" behind surface of sphere
>Paraboloid (facing right) Dia = 17.5"
>Paraboloid RC= 157.37"
I had never tried to work out the Waineo Null Test in OLSO before, so
this was something of a trial and error (mostly error) exercise to get
approximate initial spacings. I only vaguely recalled the setup, but I
entered the information you gave in your note. I have no idea if this is a
correct setup. At least I got some results that looked reasonable.
I used a monochromatic source of 546 nM wavelength. I optimized the
setup for minimizing total spherical aberration. I also played with the
spacings to try to get close to your requirement that the knife edge be 7"
behind the reference surface.
(Everyone, please forgive me for continuing to use English units. I
tend to work in the units originally specified. This brings up a point
about OSLO-LT 6.x vs. OSLO-LT 5.4. In addition to supporting fewer
surfaces, they also removed the "scale" command which made it very simple
to switch between units once the design was entered. That is only one of
several reasons I keep both versions installed on my system.) Now, back to
the task at and...
The setup says that the 12.5" reference sphere is large enough -- only
an 11" element is required to cover your 17.5" mirror. The optical fiber
source needs to be set just under 48" from the reference sphere and the
spacing from reference sphere to your mirror is about 103". This set of
values gives a knife edge position of about 7" as requested.
Here is the setup in human-readable form:
*LENS DATA
No name
SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPE NOTE
OBJ -- 47.998151 V 0.005000 AIR
AST -132.720000 -102.950000 5.484369 AS REFL_HATCH
2 157.370000 109.996872 S 8.750000 S REFL_HATCH *
IMS -- 0.000417 0.007224 S
*CONIC AND POLYNOMIAL ASPHERIC DATA
SRF CC AD AE AF AG
2 -1.000000 -- -- -- --
After refocusing for minimum on-axis RMS OPD error, the results said
that the best residual P-V error was better than 1/100 wave (at the
wavefront) with an RMS error of about 0.002. The Strehl ratio was reported
to be 0.999+. If I did the setup correctly, it looks like a very good null
for this mirror.
*WAVEFRONT RS
WAVELENGTH 1
PKVAL OPD RMS OPD STREHL RATIO RSY RSX RSZ
0.008762 0.002133 0.999813 -- -- --
If anyone finds errors in what I did, please point them out. I am
still learning this stuff, too. If there are other setups which might
satisfy the general requirements Jim stated, let's see them also.
If anyone would like to play with the OSLO file, here it is in text
form. Just cut out the lines between the "Cut Here" lines and paste them
into a text file which you can then rename "WaineoNull.len". That file
should then read into OSLO okay.
==================== Cut Here =======================
// OSLO 6.04 3087 49397 53247
LEN NEW "Waineo Null" 124.04 3
NAO 0.1135234203395
OBH -0.005
DES "OSLO"
UNI 25.4
SNO1 "17.5\" mirror with 12.5\" reference sphere."
// SRF 0
AIR
TH 47.9981512511403
AP 0.005
NXT // SRF 1
RFH
RD -132.72
TH -102.95
NXT // SRF 2
RFH
RD 157.37
PY 0.0
CC -1.0
NXT // SRF 3
AIR
TH 0.0004167548447
WV 0.546
WW 1.0
END 3
DLRS 3
OPDF 1.0e-08
OPOC "*opabrs"
VAR NEW
V 1 0 0 TH 0.1 10000.0 1.0 0.0005484368988
END
OPE NEW
O 1 "OCM41" 1.0 ""
END
==================== Cut Here =======================
Sincerely,
John D. Upton
Georgetown, TX
<http://www.atm-workshop.com/> "The ATM's Workshop Page"
<http://members.aol.com/RonWin20/> "Ronchi For Windows Software Page"