There seems to be no commercial source of scatterplates (Edmund Sci.) used
to sell them 20 yrs ago.

Anyone ever used this type or constructed one?
Any professionals can make me one?

NS

I've used one that was made by Larry Rubin when he was a grad student
at the University of Arizona. To make a scatter plate, you take a
glass photographic plate and expose it to laser speckle, then flip it
180 degrees and expose again. You can probably get the details from
his dissertation, ca 1980. (Many dissertations are available from
University Microfilms). Let me know if you make some; I'd gladly pay
$25 for one. I assume that you know that the problem with
scatterplate interferometers is the central hot spot. The advantages
are that they don't require (or like) coherent light and that they
require minimal precision parts.

In article <vplq8bau89t38b@corp.supernews.com>, Neal@nospam.com says...

There seems to be no commercial source of scatterplates (Edmund Sci.)
used
to sell them 20 yrs ago.

Anyone ever used this type or constructed one?
Any professionals can make me one?

NS

I've used one that was made by Larry Rubin when he was a grad student at
the
University of Arizona. To make a scatter plate, you take a glass
photographic
plate and expose it to laser speckle, then flip it 180 degrees and expose
again. You can probably get the details from his dissertation, ca 1980.
(Many dissertations are available from University Microfilms). Let me
know if
you make some; I'd gladly pay $25 for one. I assume that you know that
the
problem with scatterplate interferometers is the central hot spot. The
advantages are that they don't require (or like) coherent light and that
they
require minimal precision parts.
--
Best regards,
Steve Eckhardt
skeckhardt at mmm dot com

I wonder if the hot spot in the center could be reduced by careful
design of the scatter plate, by making it pseudo-random.

Around 1980 there were some scatter plate interferograms on the walls
at OSC (Tucson) that didn't have too bad a central hot spot.

With current technology it would be easy to calculate a pattern, print
it to film, then make a reduced size hologram to a plate. Bleach as
usual.

regards-
Elliot Burke
Sounds like a good idea.

"Elliot Burke" <elliot@nospamhitide.com> wrote in
news:3f9da54d@newsfeed.netlojix.com:

I wonder if the hot spot in the center could be reduced by careful
design of the scatter plate, by making it pseudo-random.

Around 1980 there were some scatter plate interferograms on the walls
at OSC (Tucson) that didn't have too bad a central hot spot.

With current technology it would be easy to calculate a pattern, print
it to film, then make a reduced size hologram to a plate. Bleach as
usual.

regards-
Elliot Burke
Sounds like a good idea.
What is the size of the "holes" in the final pattern?
Would regular film work or does it require hologaphic type?

NS

While you're at it, try to do some holographic interferometry. That
is a very entertaining process!

regards-
Elliot Burke

It will be expensive to use hologaphic film.
How about using a ground microscope slide and a very small mirror in the
center as a scatterplate? With this placed at the COC of a parabolic
mirror
it should make an
interference pattern.

NS
While you're at it, try to do some holographic interferometry. That
is a very entertaining process!

regards-
Elliot Burke

It is required of a scatterplate that it have a particular type of
symmetry: in a radial coordinate system,
phase(r,theta)=phase(r,theta+pi). Thus a point on one side of the
optical axis when imaged by the optical system will see the same phase
on the other side.

Ground glass will not do this.

But how accurate does the symmetry need to be?

"Elliot Burke" <elliot@nospamhitide.com> wrote in
news:3f9f3484@newsfeed.netlojix.com:

It is required of a scatterplate that it have a particular type of
symmetry: in a radial coordinate system,
phase(r,theta)=phase(r,theta+pi). Thus a point on one side of the
optical axis when imaged by the optical system will see the same phase
on the other side.

Ground glass will not do this.

But how accurate does the symmetry need to be?
Say I might be able to flip the exposures within 0.2mm and 180 +/-1/2
degree. Would this be sufficient?

NS

The 180° flip should be accurate to a fraction of the diffraction limited
spot size at the scatterplate.
For the f/2 example before, the position error should be <1 µm.

Assuming a scatterplate radius of 2 mm, 1 µm corresponds to an angle of
0.001/2 or a little under 2 arc minutes.

Kinematic fixturing can achieve this easily.

regards-
Elliot Burke

Not sure where I would get my handson the Kinematic fixture.

I ready to try to make the scatterplate.
Where would one get a kinematic mount?
Would it be possible to duplicate them by contract printing the hologram?

NS

The scatterplate is usually made as a phase hologram. It probably
could be made just conventional film processing, but the efficiency
would be much less. Considering how bright the images are, maybe this
wouldn't be a problem.

The film would have to have adequate resolving power.
For example, say you want to look at a f/2 optic with the
scatterplate, the speckles would be about 2µm in diameter. The film
would need high MTF beyond 500 cy/mm.
Most consumer photographic films will have no response at these
spatial frequencies, their emulsions are too thick and grain too
large.

Holographic plate might be the best source for high resolution
emulsions.

It is harder to get holographic materials than it used to be, but
there must still be sources around somewhere. Call your local
photography store or search the internet.

If you really want to do this, look at a book on holography and see
what is involved. The scatterplate is very similar in requirements.

While you're at it, try to do some holographic interferometry. That
is a very entertaining process!

regards-
Elliot Burke

I ready to try to make the scatterplate.
Where would one get a kinematic mount?
Would it be possible to duplicate them by contract printing the hologram?

NS