microscopy in the home shop
Let There Be Light - The Sequel.
Good Bye Lamp House!
Okay, I confess, the first installment of Let There Be Light did not end leaving
expectations of a sequel! However, I have found a simpler way to
convert old illumination to fibre optics. It’s one that I felt was worth
passing along. While cruising eBay I came across a Zeiss fibre optic to
Axiomat adapter. No lamphousing just a “plug and play” adapter? In short
order I cobbled together a prototype, using junk from my spare parts drawer
(only one after “Zenifying” my work area). It worked just fine but not
exactly an off-the-shelf conversion, ergo I explored the local hardware
store; one of the joys of being retired! Per usual, I zeroed in on the
plumbing section and lucked out. I purchased and left with the perfect
fitting for my Zeiss 60 watt lamp house/Schott-Fostec fibre cable.
The fitting is a PVC device your local plumber might
call a “dishwasher adapter”, and should cost no more then a couple of
dollars. The conversion should be relatively straight forward for most
lighting systems designed for Köhler illumination.
First, you need to remove the lamp condenser lens assembly (lens and frame).
This assembly is then remounted to the fitting after making the cuts shown
in the Figure 1. As Figure 2 illustrates, a spacer of some sort may be
needed (my lamp condenser, or "collector lens", is mounted in
a circular frame, the rim of which protrudes about 2 mm; hence the need
for a 2 mm spacer). I hate to admit this, but in this version the three
components are held together by carpet tape (amazingly it’s very sticky
on both sides and has a million uses).
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click image to enlarge (121K)
Figure 3 shows the completed device coupled to my
Zeiss PM2. I will, likely, have an adapter machined at some point; not
an essential step, but one that would bring the coupler assembly more
in line with the "look" of the PM2. Figure 4 is a cross-section
drawing illustrating the relative positions of the collector lens assembly
and fibre cable, within the PVC adapter. You achieve Köhler illumination
in exactly the same manner as the earlier, bulb assembly adapter, by sliding
the ferrule in and out. As the picture illustrates, the cable ferrule
can be secured in position by means of a coarsely-threaded wood screw
with the tip ground flat to avoid marking the cable finish.
click image to enlarge (97K)
click image to enlarge (110K)
This solution affords an easy way to develop the right configuration
for your system, without the cost and trouble of experimental machine work.
Although, the "plumber's special" does the job perfectly; I will, as
noted earlier, have an adapter machined as a more permanent solution.
Please send inquiries to my e-mail address by clicking my name in the
title bar of this article.