For my microscope system I need me some white light. At first I went with a high power LED from thorlabs, and instead of paying some hundreds of dollars for their driver, I built one myself for much less. The central element was the current regulator, the 1000mA, externally dimmable “buck puck” from luxeon star LEDs, along with a wiring harness for easy interfacing with the wiring from the Thorlabs LED. At that time there were no 4-pin female mounted LED mating connectors on the thorlabs site, so I just chopped the connector off that would go to the TL driver and connected it to the wires from the wiring harness attached to the buckpuck.
This compact light works quite well for brightfield illumination, but not as well for darkfield illumination with an annulus. Another approach to darkfield involves using an axicon, which is a lens that creates a ring through diffraction, whereas an annulus simply blocks a central region of the beam, creating the darkfield ring to be sent to the back aperture of the objective lens in the case of epi- (or back-) illumination. Haven’t checked other vendors, but thorlabs axicons sell for more than $1,000, so a more affordable approach would be preferable. But currently it seems the light from the annulus with only the high power LED is too weak, less than 1W. So it’s time to look at other lighting options.
Flashlamps seem like both the most affordable and also a widely used option. Here’s one vendor: interlight.biz. I’ve seen xenon flashlamps used scientific applications, maybe because the xenon spectrum is a little bit flatter than the others (spectrum link is to jpeg found in wikipedia article on “flashlamps“.
