"Daniel C. Focht" <[log in to unmask]> wrote:
> What is the frequency & amplitude of the z axis displacement you are
> encountering?

Tom Donnelly <[log in to unmask]> wrote:
> I am not totally clear on the problem.
> Does the focus drift out or just change from x to x +/- 0.5um?

Thanks for your replies so far.
I'll make THE PROBLEM more clear now.

The frequency of the z axis displacement is between 2 and 6 minutes,
depending on the insulation of the objective (better insulation,
longer period). During such period the focus position first changes slowly
down (to the objective) and than quickly changes to the first position.
The amplitude of the shift is between .2 and .5 um. When I swich off
either heater-controller (objective-heater or warm-table)  the focus
shifts dramatically towards the objective.

Again, I do not believe that the heater-controllers are not OK. They
have an accuracy of less than 0.1 C. It must be something else.

This week I'll try the other suggestions. You will hear from me.

Erik Manders
CRC Nuclear Structure and Function Group
Sir William Dunn School of Pathology
Oxford University
South Parks Road, Oxford OX1 3RE, UK
Tel: (+44/0) 1865 275529 (/275500)
Fax: (+44/0) 1865 275501
E-Mail: [log in to unmask]