Using biological microscope for metals without additional light source

[kit1980]

I came up with a very simple technique for using a biological microscope with a transmitted light source for metals and other opaque objects without additional light sources (maybe it's a well-known technique, I'm not sure).

Just put the object (which size needs to be large than field of view, but much smaller than ping-pong ball diameter) on a slide, put a ping-pong ball half with a hole for objective on top.
Remove any condensers, remove or fully open the field diaphragm, increase illuminator brightness to maximum.
The opaque object will block any transmitted light, so direct light will only illuminate the ball half, and the object itself will be illuminated by the light bounced of the ball half.

Here is unedited (except resizing) picture of a 1 cent coin with 10x objective using this technique. Exposure time was about 0.77 sec.

[Yann E.]

Congratulations on re-inventing the Descartes-Lieberkühn reflector, in a much simpler and very cost-effective version !

This "ping-pong ball illuminator" is a well known technique for high-magnification macrophotography, and yours is an interesting transposition to microscopy. The result is very similar to epi-darkfield, very nice !

The only drawback IMHO is that unless one uses LWD objectives it would probably be difficult to achieve good results with objectives above 10x.

Although I'm fully equiped for epi-darkfield many of my entomologist colleagues are not so I'm going to give it a try to let them know what works and what doesn't. This should prove especially useful for students who work on a tight budget and often can't afford high-end equipment.

I may need your full name for due credit though...

[Crater Eddie]

Cool! I'm going to have to try that.
CE

[zzffnn]

Thank you, kit1980, for sharing this technique.