looking for a polarizing filter

From: Denis de Castro (nospam_at_somewhere.invalid)
Date: 09/30/04 

Date: Thu, 30 Sep 2004 20:38:00 +1200

Hi, looking for a circular polarising filter, about 43mm diameter, screw
mount, but diameter and mounting not critical as we can machine a
mount. What's important is high light transmission.

The lens came from a Leitz Diaplan 20 (a condenser stage held two of
these lenses which could be moved relative to each other), but is now
used in a laboratory 'composite' microscope used to study single live
neurons with calcium ratio imaging. Apparently a layer of polarising
material is sandwiched between layers of glass, and the film comes away
from the glass causing an oil-slick interference pattern (we originally
thought the lens was broken until I learnt this). We soon found a
polarising filter at a camera shop, but apparently photographers'
polarising filters all block a considerable amount of light ('2
stops'), and we need a lens that allows plenty of transmitted light.

Local agents of microscopy companies haven't been able to help
satisfactorily. If anyone could provide a pointer to where a
replacement could be found we'd be most grateful.

cheers and thanks in advance,

Denis de Castro

neurophysiology lab, Auckland NZ

(www.health.auckland.ac.nz/physiology/neurophysiology)

(my email address is dfkx2001 and the domain is sneakemail.com) 

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