Microscope Illumination: LEDs are the Future
lamps are inconvenient to use and their bulbs require regular replacement. LEDs are set to replace incandescent and discharge
lamps because they offer better characteristics in illumination intensity, lifetime, wavelength specificity, and ease-of-use. Te environmental and safety benefits of LEDs are also persuasive. No mercury is used, and there are no replacement and disposal issues to address. Lower power consumption satisfies the ever-increasing demand for a “greener” laboratory.
References [1] Carl Zeiss, “Microscopy Campus,” http://zeiss-campus.
magnet.fsu.edu/.
[2] Olympus America, Inc., “Microscopy Resource Center,”
http://www.olympusmicro.com/primer/anatomy/ illumination.html.
[3] Nikon, “MicroscopyU,”
http://www.microscopyu.com/. [4]
http://zeiss-campus.magnet.fsu.edu/articles/lightsources/ leds.html.
Figure 3: LEDs are easily controlled from a control pad. Instant On/Off and intensity control make shutters and ND filters redundant.
common fluorophore stains. For more complex applications such as dual staining of live cells and FRET [8], the absence of UV, fast-switching, and temporal stability are highly attractive.
Environmental Considerations Tere are three main areas where the type of microscope
illumination used is affected by environmental considera- tions: (a) health and safety relating to eye damage from UV radiation, (b) the safe use and disposal of mercury products, and (c) energy consumption. UV light is known to damage the human eye. Broad-spectrum incandescent or discharge lamps generate mostly unwanted UV light, which needs to be filtered out. Tese lamps are safe when fitted to microscopes that have a UV filter installed to reduce this risk. Care must be taken when operating the lamp if no filters are in place or when it is not fitted to the microscope. Because LEDs only generate specific wavelengths of light, only those LEDs intended to illuminate in the UV region can cause UV damage. Where mercury is used, consideration must be given
to the risk of a bulb exploding and releasing mercury vapor into the air. Health and safety requirements for mercury are becoming ever more onerous because it must now be treated as a hazardous material. Tere are also strict rules for the safe disposal of spent mercury bulbs. Laboratories are being encouraged to reduce their energy
consumption. With the higher efficiencies of LEDs, about six times less energy is consumed in comparable usage. Because many conventional lamps are leſt on all day to overcome warm-up requirements, the actual reduction in energy by using instant on/off LEDs can be significant.
Conclusions Conventional incandescent and discharge lamp illumi-
nation offers the benefit of broadband illumination. Tis reduces the need to ensure that the optical filters are correctly matched to the light source being used. A single light source can satisfy most microscopy applications. However, these
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[5] A Zukauskas, M Shur, and R Gaska, Introduction to Solid State Lighting, John Wiley & Sons, New York, 2002.
[6] CoolLED, “Why LEDs,”
http://www.coolled.com/ Life-Sciences-Analytical.
[7] EF Schubert, Light-Emitting Diodes, Cambridge University Press, New York, 2006.
[8] K Aoki and M Matsuda, Nature Protocols 4 (2009) 1623–31.
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