At 09.23 AM 2/11/97 +0000, Mark Tobin wrote:

>1.    What is the common method of z-translation in commercial instruments?
> Piezoelectric, or stepper motor control of the focus wheel? I have seen the
>piezo objective mounts on some Noran instruments....are they any good?

Leica has a piezo microscope stage whereas many others, including Zeiss and
BioRad, use a stepper motor to drive the focus knob. Nominally, the Leica
stage has a much better precision than the stepper motor drives, but in
practical biological microscopy, the difference is neglible. I have
experience with the Leica stage, and vibrations were not a problem in
biological microscopy. I am equally satisfied with our BioRad/Nikon focus drive.

>2.    When you wish to view the sample by phase contrast, do the scanning
>mirrors have to be flipped out of the beam?  In my current set up, the second
>scan mirror is about 15mm above the back aperture of the objective.

Probably not if you are using a conventional phase contrast setup in an
upright microscope. You then need a somewhat bulky condenser below your
specimen, but nothing extra above the objective.

Regards,

Berndt Ehinger


__________________________________

Berndt Ehinger
Department of Ophthalmology
Lund University Hospital
S-221 85 Lund, Sweden
Phone +46 46 17 16 90
Fax +46 46 211 50 74
__________________________________