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New LEDs for your microscope - tardigrade friendly cold light! (I)
From 230V tardigrade barbecue to clever LED microscope illumination

All of us do know that most technical innovations take their time and that their step-wise development will be financed partially by the consumer. Just think about those bizarre mercury loaded energy saving lamps (cf. spectrum in fig. 1) and the "halogen" bulbs which were recommended to museums, churches and private consumers a few decades ago. Nowadays, everybody is trying to replace those intermediate products by state of the art LEDs or even going back to old fashioned, classical filament bulbs.

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Fig. 1: The spectrum of a typical old-fashioned "energy saving" lamp ("energy saving", before the LEDs came up finally). It goes without saying that the distribution of wavelengths is discontinuous, resulting in very "special" colors. As can be seen in the figure, many intermediate wavelengths have actually intensity zero and therefore cannot interact with the illuminated objects.

When comparing the above spectrum with the spectrum of natural daylight (see below) it becomes clear that the light of the energy saving lamp is very artificial and that its color rendering ability must be miles away from natural daylight:

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Fig. 2: The spectrum of natural daylight has its energy distributed rather smothly over a large range of wavelengths. Besides, you might note those interesting small "shark tooth" indents called Fraunhofer lines which were reporting the sun's chemistry to our scientists almost two centuries ago.

The color rendering is not so much a problem for the microscopist. Nevertheless modern LEDs can combine perfect color rendering with low heat diffusion, the latter being very much important for tardigrades studies. Please remember that we do not want to boil our live tardigrades under the microscope!

But there is even more: LEDs are small, so they can be easily fitted in old-fashioned housings, like those of high voltage E14 (14 mm thread) bulbs. As a consequence some microscope LED adapations can be performed by simply replacing E14 filament bulbs with E14 LED bulbs. No soldering, no additional wiring, reversible changes to (some, not all - sorry) historical microscopes. Let's have a look at the respective technical development:

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Fig. 3: The metamorphosis of ancient high voltage bulbs to high performance LED lights
(1)  Classical E14 thread 230 V bulb with a power of 25 W. Be warned: this is a tardigrade (heat) killer! (109)
(2)  An early E14 LED lamp, unluckily with the light radiating to all sides (10 ... 20)
(3)  A more modern, matte LED light with a little bit more power (30)
(4)  Our present favorite - a LED lamp with 24 tiny LEDs. It directs most of its light into the microscope optics - perfect! (112)
The red numbers in brackets are indicating the approximate light output of the respective products.

We will demonstrate the practical usability of those E14 replacements in the next issue of our magazine.

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
The Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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