Subject: [interferometry] Digest Number 1027
From: interferometry@yahoogroups.com
Date: 2/9/2008, 7:27 AM
To: interferometry@yahoogroups.com

interferometry
interferometry

Messages In This Digest (11 Messages)

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Messages

1a.

Re: OpenFringe 8.3  already

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Fri Feb 8, 2008 9:09 am (PST)

I think I talked about that comparison when it happened. It was
qualitative and not quanitative. James Mulherin may be able to
comment beter. What I remember him saying is that strehl looked
similar and the Foucault simulations from OpenFringe data looked like
what he saw in actual autocollimation.

Dale Eason

--- In interferometry@yahoogroups.com, Michael Peck <mpeck1@...>
wrote:
>
> At 08:50 AM 2/8/2008, Barry Jensen wrote:
>
> >Work around for wavefront averaging concern at cost of resolution
> >would be to save Zernike files from fft and average those?
>
> It's pretty straightforward to rotate a wavefront described by its
> Zernike coefficients, and it can have any resolution you want.
> OpenFringe just doesn't have the capability yet to fit arbitrary
sets
> of Zernike polynomials to a wavefront.
>
>
> >Finally, I sent my mirror out to professional optician who tested
> >using interferometry (not Bath, not OpenFringe) in autocollimation
> >and got good enough agreement to validate FFT/OpenFringe for the
>
> There might be some interest in seeing a detailed comparison.
>
> >
>
> ------
> Michael Peck
> mpeck1@...
>

1b.

Re: OpenFringe 8.3  already

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Fri Feb 8, 2008 9:21 am (PST)

--- In interferometry@yahoogroups.com, "Barry Jensen"
<barryjensen@...> wrote:
>
> This problem with averaging different mirror sizes due to defocus
or
> zoom camera settings exists when averaging wavefront files? This
is
> because pixels do not map 1:1 at edge and therefore some wft files
> lack pixel data where other wft files have them?
>
That is a very close statement of the problem complicated by tilt and
defocus removal.

> Crop and resize does not make all images same number of pixels for
> analysis? Probably, I miss the point entirely.
>

I had forgotten about that. It should in fact keep all of them at
the same size and translation. Maybe I did not use that for all
analysis of John's Igrams since they were close to being small enough
in the first place. Glad you remembered more about the program than
I did.

> I think it will be difficult to do rotations on stand and get
> exactly same diameter of image. Problem is worse for me because
> camera shuts off after a minute of non-use and I have to refocus
and
> rezoom camera. My camera has no setting to disable this "feature".
>
> Work around for wavefront averaging concern at cost of resolution
> would be to save Zernike files from fft and average those?
>

OpenFringe only knows how to rotate Fringes and Wavefronts. Rotating
Zernike terms is a little more complex and I have never implemented
it. This only becomes an issue when the mirror is so fast that one
cannot get a small number of fringes to trace.

As I said one work around is using the ignore edge controls and then
save the zern file. I have not tested that to make sure it works.
Another option is to counter rotate the igram before analysis and
then save the zernike file from that for averaging.

....
> Barry
>
>
>

1c.

Re: OpenFringe 8.3 already

Posted by: "Stephen Koehler" s.c.koehler@gmail.com   steve_koehler

Fri Feb 8, 2008 9:56 am (PST)

Dale,

> OpenFringe only knows how to rotate Fringes and Wavefronts. Rotating
> Zernike terms is a little more complex and I have never implemented
> it. This only becomes an issue when the mirror is so fast that one
> cannot get a small number of fringes to trace.

If you're motivated to do this, I can help with Zernike rotation. I
have had that in my code for a long time, and it's not difficult.
Here's my rather dense implementation in R. In C, I'm sure it's a bit
larger. :-)

zern.rotate.mat <- function (s, angle) {
A <- outer (s$m, s$m, "==");
B <- outer (s$n, s$n, "==");
C <- outer (s$s, s$s, "-")
A * B * cos (C*pi/2 + s$m*angle)
}

zern.rotate <- function (Z, s, angle)
# Rotate zernike coefficients clockwise by the specified angle.
as.vector (zern.rotate.mat (s, angle) %*% Z)

--
Steve Koehler

2a.

Averaging fft on same image

Posted by: "John Abrahamian" imas1@aol.com   owl1820002000

Fri Feb 8, 2008 12:41 pm (PST)

Since I'm not totally sure when my fft models are turning out
correctly is there any value in saving wavefronts from the same image
with different ellipse tracings?
John

2b.

Re: Averaging fft on same image

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Fri Feb 8, 2008 1:36 pm (PST)

Slightly different ellipse tracings change the SA terms if they are
different in diameter otherwise it only changes coma which we ignore
anyway.

Save only what you think is the best you can do.

Dale Eason

--- In interferometry@yahoogroups.com, "John Abrahamian" <imas1@...>
wrote:
>
> Since I'm not totally sure when my fft models are turning out
> correctly is there any value in saving wavefronts from the same image
> with different ellipse tracings?
> John
>

3a.

"average igrams" in file menu

Posted by: "John Abrahamian" imas1@aol.com   owl1820002000

Fri Feb 8, 2008 9:53 pm (PST)

I've been saving igram wavefronts for several images and have achieved
an average set of data from these. I have a few sets completed then I
noticed "Average Igrams" in file menu options.

How exactly is the " average igrams" used in the file menu? It asks
for "images" in bitmap. After I averaged 4 igrams I simply saved the
wavefront and zernike file. Is this different than File>Average Igrams
in the menu?
John

3b.

Re: "average igrams" in file menu

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Sat Feb 9, 2008 6:10 am (PST)

Averaging igrams is not very useful in your case. Don't worry about it.
You want to average wavefronts or zernikes instead.

I'm starting a drive to Oklahoma today but I will be back on the net
tonight I think.

Dale Eason

--- In interferometry@yahoogroups.com, "John Abrahamian" <imas1@...>
wrote:
>
> I've been saving igram wavefronts for several images and have achieved
> an average set of data from these. I have a few sets completed then I
> noticed "Average Igrams" in file menu options.
>
> How exactly is the " average igrams" used in the file menu? It asks
> for "images" in bitmap. After I averaged 4 igrams I simply saved the
> wavefront and zernike file. Is this different than File>Average Igrams
> in the menu?
> John
>

4a.

25" Final Results from 5th Figuring Session in OpenFringe

Posted by: "John Abrahamian" imas1@aol.com   owl1820002000

Sat Feb 9, 2008 12:31 am (PST)

I've uploaded my final results from fft analysis. I make no claim as
to it's accuracy. The results depicted are not related to the actual
mirror orientation and are reversed. I do not know how to flip the
results to show
them in real world configuration. This was more of a practice session
for me to learn the software procedures. I used images labeled:
3009,10,11,12
3001,02,03,04
3018,19,20,21
3030,31,32,33

I averaged 4 tilts for each rotation of 0,45,90,135 degrees.
I counter rotated wavefronts and combined with 0 degree wavefront and
got an average of these. My final results are derived from these.

I hope I can generate correct real world orientation in the models
easily. Otherwise I'll have to do them all over again. It would go
faster now though I believe.

The results are here:
http://tech.groups.yahoo.com/group/interferometry/files/John%20Abrahamian/25%22%20Averaged%20Igram%20Data%20Result/

Thanks, John Abrahamian

4b.

Re: 25" Final Results from 5th Figuring Session in OpenFringe

Posted by: "Dale Eason" atmpob@yahoo.com   atmpob

Sat Feb 9, 2008 6:15 am (PST)

It looks reasonable to me. You have astig value turned off both in
the zernike and wavefront zernike menus. Probably want to turn that
one. I will look closer at all of it tonight. The astig value shown
in the report is much lower hopefully that is a true value.

Dale

--- In interferometry@yahoogroups.com, "John Abrahamian" <imas1@...>
wrote:
>
> I've uploaded my final results from fft analysis. I make no claim as
> to it's accuracy. The results depicted are not related to the actual
> mirror orientation and are reversed. I do not know how to flip the
> results to show
> them in real world configuration. This was more of a practice
session
> for me to learn the software procedures. I used images labeled:
> 3009,10,11,12
> 3001,02,03,04
> 3018,19,20,21
> 3030,31,32,33
>
> I averaged 4 tilts for each rotation of 0,45,90,135 degrees.
> I counter rotated wavefronts and combined with 0 degree wavefront
and
> got an average of these. My final results are derived from these.
>
> I hope I can generate correct real world orientation in the models
> easily. Otherwise I'll have to do them all over again. It would go
> faster now though I believe.
>
> The results are here:
> http://tech.groups.yahoo.com/group/interferometry/files/John%
20Abrahamian/25%22%20Averaged%20Igram%20Data%20Result/
>
> Thanks, John Abrahamian
>

4c.

Re: 25" Final Results from 5th Figuring Session in OpenFringe

Posted by: "Stephen Koehler" s.c.koehler@gmail.com   steve_koehler

Sat Feb 9, 2008 6:19 am (PST)

John,

> I've uploaded my final results from fft analysis.

I notice that the report shows the two astigmatism terms as being
disabled. I think you want to enable the astig terms. I'm wondering
if astig is off, by default, in OpenFringe. To enable the x and y
astig terms, bring up the Wavefront Zernikes box from the Zernikes
menu and uncheck the two boxes.
--
Steve Koehler

5.

camera for Bath interferometry

Posted by: "Vladimir Galogaza" vladimir.galogaza1@zg.t-com.hr   vgalogaza

Sat Feb 9, 2008 5:21 am (PST)

Dale, John,

You are using same or similar cameras, Canon Digital Rebel,
and John has EF 75_300 f/4.5-5.6 lens.
I have two cameras one has 6 x zoom and f/2.8-3.0 lens while
another one has 12 times zoom, f/2.8 in fool zoom range.
Both have manual aperture priority setting capability.
John has mirror 640 mm diameter, f/3.8, my mirror is only f/4, 152 mm dia.
I wander why I can not get full interferogram without vigneting,
while John and Dale have no problems in making their wonderful
interferograms. We are using same right angle variant of Bath.

Please can somebody discuss the problem and give me advice.

Thanks in advance and regards,
Vladimir.
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