I am a problem imaging with  the Olympus LWD (long working distance) objectives 
on an IX81 frame. I have image well with the  high NA objectives (oil and air),
which are used when imaging through thin coverslips. However, with the LWD 
objectives, I cannot raise the turret enough to get an image.
This is puzzling, because I thought that the objectives were designed to be 
parfocal, so that if I have focus for one objective, I will have focus for the 
other at the same turret position. Yet, if I put a regular slide with a coverlip 
on the scope, I can image it with the 20x close focus air objective, but then 
when I switch to the LWD objective ( and set the cover thickness ring 
appropriately for a coverslip, I cannot even get close to an in-focus image.

The stage is a LUDL motorized stage, and it may be higher than the regular 
mechanical stage, but this does not explain why the close focus high NA 
objectives can focus, and the LWD objective dont.

Thanks in advance  for putting me straight on what is probably something obvious.

--aryeh
-- 
Aryeh Weiss
School of Engineering
Bar Ilan University
Ramat Gan 52900 Israel

Ph:  972-3-5317638
FAX: 972-3-7384050