Hello fellows,

I am doing some thinking about the temperature dependence of the conic
constant of a non-spherical surface. Can anybody recommand literature about
this topic or knows how it behaves? I would like to know if the concic
constant changes when e.g. a hyperbolic mirror is heated homogenously.

Florian wrote:
Hello fellows,

I am doing some thinking about the temperature dependence of the conic
constant of a non-spherical surface. Can anybody recommand literature
about this topic or knows how it behaves? I would like to know if the
concic constant changes when e.g. a hyperbolic mirror is heated
homogenously.

There is no change in the conic conic constant when the mirror is
heated homogeneously. The only parts that change is the [central]
radius of curvature and the size/thickness.

Hello Richard,

thank you very much for the answer. Can you also tell me some literature
where I can find information about the thermal analysis of optical elements?

Your first question was simple enough to be demonstrable.

thank you very much for the answer. Can you also tell me some literature
where I can find information about the thermal analysis of optical elements?

Greetings

Florian

Florian:

thank you very much for the answer. Can you also tell me some literature
where I can find information about the thermal analysis of optical
elements?

Greetings

Florian

Florian:

You can find some info in Chapter 39 Thermal Compensation Techniques
by Phillip Rodgers and Michael Roberts in Hdbk of Optics Vol I
They talk about the active and passive athermalization of optical
system.

For thermal analysis of optics mounts see Paul Yoder's book on
Mounting Optics in Optical Instruments
and also Chap 9 by Victor Genberg in Hdbk of Optomechanical
Engineering by Anees Ahmad
Genberg and Co also have a book on thermal modeling FEA of optical
systems

For optical design specifics look up athermalization in Applied
Optics, JOSA A&B and SPIE Proceedings

Thanks for asking the question, I had not thought about this and had
to think back to my calculus of conic section and ellipses &
hyperbolas.
Right now I am not sure I agree with the answer given yet, can you
tell us more about the rest of the system?

Are these mirrors in a telescope or hyperbolic lens surfaces?

Thanks,

Michael
www.oscintl.com

Right now I am not sure I agree with the answer given yet, can you
tell us more about the rest of the system?

Are these mirrors in a telescope or hyperbolic lens surfaces?

Hello fellows,

I am doing some thinking about the temperature dependence of the conic
constant of a non-spherical surface. Can anybody recommand literature about
this topic or knows how it behaves? I would like to know if the concic
constant changes when e.g. a hyperbolic mirror is heated homogenously.

I've recently created a software that can help to evaluate the thermal
behavior of a telescope mirror. Here's a screen shot of the application:
www.cruxis.com/scope/img/MirrorCooling_1.gif .

The application simulates the temperature evolution in a mirror subject
to varying ambient temperature and chosen heat transfer conditions on
the front and back surface. It displays a plot of the temperature
profile at every time step, and a graph of the evolution of the mirror
core, optical surface and air temperature.

You can download the software:
www.cruxis.com/scope/download/MirrorCooling.zip . The archive contains a
single executable file MirrorCooling.exe.
The following parameters are used by the program:
- Mirror Thickness
- Initial Mirror Temperature
- Initial and Final Air Temperature (varying linearly between start and
end)
- Film Coefficients for front and back (recommended values are between 5
and 15 without fans, between 20 and 100 with fans)
- Radiation Coefficients for front and back (0.04 for aluminum coating
on front surface)
- Simulation duration and time step

It's amazing to see how slowly a 2" thick mirror cools if no fans are
installed. And with thinner mirrors you can see how the temperature
drops below the ambient air temperature because of the heat radiation to
the sky.

Any comments, questions or suggestions about the software are welcome.
Cheers,

Robert Houdart
www.cruxis.com/scope