Following an impulse I went to what we here in Canada call a “Dollar Store” and bought a simple single-LED pen flashlight for $2.00 (2 AA batteries included). Under a stereomicroscope it appears to have a hemispherical glass lens of 4.5mm diameter in front. The two AA batteries are supposed to last for 100 hours of operation.

Next I machined an adapter sleeve for my Gfl microscope from a wooden dowel as per Fig. 1 to replace the original lamp socket. The pencil light fits in snugly so that I can push it in or out as required for even illumination. I arranged it so that the LED occupies exactly the position of the original bulb filament.

Surprisingly I can get bright, even illumination from the 2.5x to the 40x objective with very natural colours – no correction filter required.

Fig. 2 shows the original low voltage bulb socket with its precentred filament bulb side by side with my LED adapter.

Fig. 3 shows the microscope converted to LED light. And all that for $ 2.00. No power supply, no cables to bother with. You can’t beat that!

The micrographs show that the light is sufficient even for oil immersions (just).

Fig. 4 mouse liver section Zeiss Achromat 40/065.

Fig. 5 sunflower stem Zeiss Achromat 40/0.65 Ph.

Fig. 6 mouse liver section Zeiss Achromat 100/1.25 oil*.

Fig. 7 sunflower stem Zeiss Neofluar 100/1.3 oil Ph*.

Fig. 8 sunflower stem Zeiss Achromat 25/0.45 Ph

*The camera’s exposure correction compensated to a degree the dark phase-contrast image.

If you plan to use a green filter to improve the contrast, the light will not be enough.

Taken with a Nikon Coolpix 995 in conjunction with a Leitz Periplan high-eyepoint eyepiece 10x.

The condenser was a Zeiss Phase-contrast condenser VZ 1.4 (dry).

Considering the minimal expense involved, this modification is adequate for the average hobby microscopist. Of course, it may not be as easy or efficient for different types of microscopes.

As a friend of mine likes to say: Try it, you’ll like it!

PS: In another store I saw an LED penlight for $7.50 listed as giving 11 lumen of light. This one had a small “parabolic” mirror around the LED. I can’t say how many lumen my $2 version offers.

Fritz Schulze

Vineland, ON, Canada

All comments to the author Fritz Schulze are welcomed.

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