Source de lumière froide [ebay]

[G4Lab]

For gemological purposes, I have helped several people, start to use medical xenon arc illuminators.

The standard for viewing , photographing, and examining, gemstones is the GIA Gemolite. This is an item, which is very well designed, to do what it does. It consists, of an ellipsoidal reflector, with a 30 or 35 watt lamp at one focus, and the gem at the other. It also has the ability, to switch quickly, from bright field to dark field. At the flip of a lever.

Many jewelers and gemologists spend a whole career using these, and are satisfied 99+ % of the time.

But there are two persistent complaints. One is, if a stone is very dark, there is not quite enough light. And two, the well gets very hot.
If you drop the stone into the well, you must use tweezers. You can get a very bad burn.

The idea to use a fiber optic darkfield is not new. A 150 watt quartz halogen illuminator driving it solves both of the above problems.
But, I started playing with xenon illuminators, for spectroscopic use ,and had the idea to use them, to drive the dark field fiber cable.

The best one to use, is an illuminator based on, either a 175 or 300 watt Cermax lamp. This solves all blue deficiency complaints.
Quartz halogens are a little weak in the blue. Xenon arcs have a temperature of 5,000 tp 6,600, depending on how they are driven , the optics etc. And they render color better than any artificial light. And more repeatably than real daylight which is quite variable.

[Gérard Weiss]

Hello Gene,

It consists, of an ellipsoidal reflector, with a 30 or 35 watt lamp at one focus, and the gem at the other.

Pour avoir un éclairage puissant en épiscopie, on peut effectivement utiliser un miroir ellipsoïdal avec la source lumineuse dans un foyer et l'objet à observer dans l'autre. Le rendement lumineux peut être très important. L'objet observé peut être éclairé sous tous les angles : devant, derrière, sur les cotés, etc.

J'aimerais savoir comment cet éclairage est réalisé concrètement. As-tu des photos ou des documents ?

Merci d'avance.

[G4Lab]

http://www.gemproducts.com/microscopes.html

http://www.ebay.com/itm/GEM-Instruments ... 4ac2b66a1b

http://www.ebay.com/itm/GEM-Instruments ... 7675.l2557

http://www.ebay.com/itm/GEM-Instruments ... 7675.l2557

On the above pages you can see a the truncated ellipsoidal reflector. The newer models from the Gemological Institute of America actually have a toric reflector which is made of plastic and chrome plated. As long as you do not try to increase the lamp wattage this works OK. The toric mirror makes it not as deep. More convenient on the bench.

http://www.ebay.com/itm/GiaGem-GEMOLITE ... 27d00dca82


Photon Technology International made a lamphouse that works the way you mentioned. It had a 75 or 150 xenon arc with the arc located on one focus and the slit or fiber optic located on the other focus and a right angle mirror in between.