Since 2006 when CoolLED introduced the first LED Illumination System, LED technology has really taken off and is quickly surpassing the performance of traditional mercury and metal halide-based illumination options.

This section is where you can find out why LED microscope Illumination Systems are perfectly suited to fluorescence imaging applications, and how CoolLED LED Illuminators for microscopes have become crucial components of modern life science research and clinical laboratories.

When Light Emitting Diode (LED) technology for fluorescence microscopy arrived on the scene, it brought with it a host of benefits over traditional microscopy illumination methods such as mercury and metal halide bulbs.

LEDs are semiconductor devices which emit photons around a specific peak wavelength when an electrical current is passed through them, and as solid-state electronic devices they have introduced a range of benefits for microscopy illumination:


Irradiance declines over the lifetime of a mercury or metal halide bulb, whereas LEDs are stable over time, providing reliable and consistent results. LEDs also offer excellent uniformity over the field of view.


LEDs can be easily controlled. They can be switched on and off with precise microsecond timing, which removes the need for a mechanical shutter and improves the temporal resolution of experiments for capturing high-speed events. LED irradiance can also be modulated electronically in 1% steps (0-100%), removing the need for neutral density filters and protecting samples from phototoxicity and photobleaching.

Improved image contrast

With a broad spectrum of “white” light from traditional microscopy illumination, the majority of light is unwanted and must be removed using optical filters. As individual LED peaks can be controlled independently, a microscope LED light source can be set to illuminate only the desired wavelength peaks matching a particular fluorophore’s excitation spectrum, increasing the signal to noise ratio and improving image contrast.


Bulbs frequently need replacing, whereas LEDs are long-lived. The alignment required after frequently replacing bulbs is tricky, but LEDs can be factory aligned and are ready to be fitted to the microscope.


In addition to the short lifetime of bulbs adding to the long-term cost, they also require specialist disposal due to the high-pressure bulb and mercury content.

Safety and the environment

Mercury in bulbs is hazardous to people and the environment. Bulbs are also left on for days during experiments, whereas LEDs can be switched off easily when not in use, which reduces energy consumption. In addition to this, LEDs are more energy efficient and emit much less heat.

The latest LED microscope lighting technology

LED microscope lighting technology has matured to provide many powerful LEDs covering the full visible spectrum, from the UV across the visible range and into the IR.

Common LED myths explained:

Research and Development efforts have overcome many of the initial limitations and we want to update a few common misconceptions.

“LEDs don’t provide enough intensity for fluorescence microscopy”: Intensity, or irradiance, has come a long way from the first system, thanks to CoolLED’s R&D team who are always innovating. And GYR irradiance is improving all the time. It is also important to remember that higher irradiance is not always beneficial, and lower levels protect against photobleaching and phototoxicity.

“I need a broader range for my fluorophores”: Only a few wavelength options existed in 2006, and now the CoolLED pE-4000 has 16, spanning 365 nm-770 nm. This can excite in the UV region and right through to fluorophores at the IR end of the spectrum (which is ideal for imaging thick samples while protecting against phototoxicity). Beyond this, our OEM illumination can offer additional wavelengths. Interestingly, this has even made way for the development of new fluorophores which no longer depend on the emission spectrum of a mercury bulb.

“I don’t have the budget for a new piece of kit; bulbs are a consumable item”: Simple, low cost models are available such as the pE-300lite, which can be purchased under the laboratory’s consumable budget.

LED technology is still evolving, and you can keep up with new developments in microscopy illumination by signing up to our newsletter.

Why CoolLED?

1) Superior technology

Our systems are dedicated to generating bright, high-contrast images to enhance data generation and interpretation for researchers and clinicians.

We achieve this through expert LED assembly and unique active cooling technology, enabling irradiance levels up to five times greater than other LED microscopy illumination systems. By holding the LEDs at a constant temperature through thermal management, we can drive them more powerfully to increase irradiance, stability, reliability and lifetime while offering the lowest energy consumption on the market.

There’s also the option to work without a liquid light guide, with Direct Fit microscope LED Light Sources offering the most efficient means of light delivery to a microscope. Only CoolLED provides this option, and our most popular type of illumination system harnesses more power whilst keeping total cost to a minimum thanks to fewer consumables.

You can choose from a range of products with a variety of LEDs and different levels of control, from single wavelength models and simple white light, through to the latest systems for advanced research applications.

2) Lifetime support

We are renowned for customer commitment and offer local support through our global network of resellers and our Global Sales Team, which means there is always an expert available to help.

We have a record of >99% on-time delivery in full against acknowledged delivery dates. Our LED microscope lighting products are reliable, but our support goes beyond the product and we pride ourselves on friendly and expert advice whenever it is needed. You will also be covered by our market-leading warranty, which includes three years as standard for all products and a 12 month in-for-out swap if we cannot fix an issue. For extended cover, we also offer a market-leading warranty extension programme.

3) Not sure? Try it out!

If you’re not sure whether a CoolLED Microscope Illumination System is right for you, we can provide a free loan unit for testing, with no obligation to purchase.

Please contact us at [email protected] for more information.