Infinity corrected lenses

From: Copepod (copepod_at_blueyonder.co.uk)
Date: 10/17/04 

Date: Sun, 17 Oct 2004 09:50:45 GMT

Some help requested please from those who know, from someone who is still
finding out.

I have been offered a compound microscope which has infinity corrected IOS
lenses. I am not entirely sure about whether, or not, these are necessary
for my purposes. I am primarily interested freshwater / marine microbiology.
I understand that such optics permit the easy insertion of filters including
polarising filters. This is of interest to me as I spend much time watching
and identifying ciliates. Further down the line when funds permit I
understand that DIC illumination would be available should I wish.

I have read that the objectives are neither parcentral nor parfocal, but I
have no way of knowing whether this is the case, or not. Is anyone able to
advise.

Searches which I have made have taken me to manufacturers' websites. But I
have been unable to find any objective or critical appraisal of the feature.

Any help / observations would be much appreciated.

Philip