CoolLED offers the most extensive range of LED wavelengths for fluorescence microscopy. Excitation starts at 365nm (matching common DAPI filter sets) and goes all the way to 770nm (for deeper cell penetration). These are provided in CoolLED’s various illumination systems as single wavelengths or combined to provide broad spectrum illumination. In addition, there is a white illumination (pE-100wht) system matched to the halogen spectrum for transmitted light illumination.

The chart below shows the standard range of single LED wavelengths used in the pE-100 series of illumination systems.

LED Fluorescence

Recent developments in LED technology have enabled increased intensity in what was historically the weaker green-yellow-red (“GYR”) region of the LED spectrum. A new wide spectrum GYR LAM is now supplied as standard in the pE-300white and pE-4000 systems. It can be specified (or fitted retrospectively) in the pE-2 illumination systems.

Microscopy Illumination

Common LED wavelengths for live cell and fixed cell applications

LEDs only excite desired wavelengths – explanation of benefits of discrete LED wavelengths

Why LEDs?
Why LEDs for Life Sciences?
Why CoolLED LEDs for Life Sciences?

Why LEDs?

LEDs (Light Emitting Diodes) are semiconductor devices which emit photons around a specific peak wavelength when an electrical current is passed through them. As semiconductors, they are:

  • Fast switching
  • Reliable
  • Stable
  • Long lasting

Microscopy Illumination

High light intensities are achievable. Although LEDs are around six times more efficient than conventional incandescent bulbs, they are still only 20 – 30% efficient. High brightness results in high heat flux densities so it is essential to provide the appropriate cooling to ensure that the LEDs do not overheat, resulting in spectral drift and premature failure.

Why LEDs for Life Sciences?

The conventional illuminator for fluorescence was historically a high pressure mercury or metal halide bulb with multiple wavelength peaks creating a broad spectrum of “white” light. The majority of this light was unwanted and needed to be removed using optical filters. As individual LED peaks can be controlled independently, an LED illumination system can be operated so that only the desired wavelength peaks are illuminated for any particular stain(s) requiring excitation.

The benefits of LEDs can be considered from three aspects


  • Instant on/offNo shutters required, no warm up or cool down
  • Simple to fit, simple to use – no alignment, a once only adjustment
  • Stable & repeatable – reliable and consistent results
  • Precise intensity control in 1% steps (0-100%) – no ND filters required
  • Excellent uniformity over field of view – fixed and stable, no alignment necessary
  • Long lifetime – expected to exceed 25,000 hours of operating time
  • Mercury-free
  • Energy Efficient: 80% less power

Why CoolLED LEDs for Life Sciences?

Only CoolLED uses active cooling of LEDs in all their illumination systems. As discussed above, LEDs are more efficient than conventional illuminators but still produce heat. By holding the LEDs at a constant temperature through thermal management of the LEDs, CoolLED can drive them more powerfully. This results in greater intensities. In addition, this increases stability, reliability, and lifetime of the LEDs.

It is CoolLED’s expertise in LED assembly and the use of active cooling which means that it can offer intensities up to five times greater than other LED illumination systems which use commercially available packaged LED parts.