At 03.31 em 98-09-02 -0400, you wrote:
>Hi,

Hi, Anand,

I must confess that I do not quite understand your problem.
What I understand is that you try to inspect a ceramic coating using a
confocal scanning laser microscope in the reflection mode. Using the 488nm
line of the Argon ion laser you managed to get information out of an
approx. 30 micron thick layer of the coating close to its surface.

Is your problem now, that you would like to penetrate deeper into the
specimen while still working in the reflection mode?

If yes, then you will have to find out a wavelength which is not so
strongly absorbed or scattered by the coating material as is the 488nm line
but which is nevertheless reflected or scattered to a sufficient degree to
get back a sufficient amount of light. This will always be a trade-off.

As a general rule one can state that the  rate of absorption and scattering
is strongly decreasing with increasing wavelength (this is why IR astronomy
or radioastronomy is much easier than UV-astrononmy). I do not have the
slightest idea which kind of reflection or scattering your specimen
produces, but as we know from basic physics, the cross section for Rayleigh
scattering is dependent on the inverse of the fourth power of the
wavelength!!!!!

If your microscope is exclusively fitted with a little Ar-laser, then you
will hardly have any wavelength available but 488nm and 514nm and perhaps
456nm and 526nm. I do not know which kind of CSLM you have and whether it's
a big deal to couple in an external laser. If not I suggest that you get
hold of a HeNe-laser for 632nm or a diode-laser, both devices which are
cheap and small.

Hope this helps.

Best greetings,


Johannes
>
>        My name is Anand Kulkarni and i am doing my Ph. D in the Dept. of
>Materials Science and Engineering at State University of New York at Stony
>Brook. I am basically working on plasma sprayed ceramic coatings and
>am studying porosity and pore structure determination in them. I am trying
>to use Confocal Scanning Laser Microscopy for that.
>        I need a favour from you. I tried to do Confocal Scanning Laser
>Microscopy that we have in our University hospital and could scan only
>upto 30 microns depth. That was by reflection microscopy and not by epoxy
>impregnation. The wavelength of the laser was 488 nm.
>        Can you suggest a way to solve my problem to get a greater depth
>response for my ceramics coatings. I work on ceramic coatings viz.
>Alumina, Titania, Spinel and Zirconia. Do reply my mail.
>        Awaiting your response. Bye for now and take care.
>
>Regards,
>Anand.
>
>
--
********************************************************
Paul Johannes Helm

Mail Address:           Institute of Basic Medical Sciences
                        Department of Anatomy
                        P.O. Box 1105 - Blindern
                        N-0317 Oslo
                        Norway

Visiting Address:       Institute of Basic Medical Sciences
                        Department of Anatomy
                        Sogsnvannsveien 9 / 0245
                        N-0372 Oslo
                        Norway

Voice:                  +47 22851159
Fax:                    +47 22851278
Email:                  [log in to unmask]
WWW:                    http://www.uio.no/~jhelm

********************************************************