Comparing microscope LED light sources

LEDs offer many benefits over conventional light sources, and a variety of microscope LED light source solutions are now available on the market. Each application places specific demands on the light source, and for the highest quality images and data it is crucial to select the system which offers the optimum wavelength selection, irradiance and control options for individual requirements.

CoolLED and microscope LED light sources

We design and manufacture cutting edge microscope LED light sources for researchers and clinicians using the latest LED technology, and were the first company to bring LEDs to fluorescence microscopy in 2006.

Since then, we have led the way in transforming light source technology for fluorescence microscopy and transmitted illumination. Now we are a fast-growing company in Hampshire with a vast product range and technical expertise spanning optical engineering and the life sciences.

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What to look out for when comparing microscope LED light sources?

  • Irradiance – the amount of light reaching the sample plane varies greatly from budget LED light rings to modern microscope LED light sources for fluorescence microscopy.
  • Spectral coverage – simple microscope LED light sources may combine wavelengths to produce white light, but the ability to choose individual wavelengths greatly enhances the signal to noise ratio. In fluorescence microscopy, it is also crucial to ensure coverage for the fluorophore of choice.
  • Control – this is where modern microscope LED light sources come into their own. The latest USB and TTL control functions are not only convenient, but also enable high-speed imaging and minimise photobleaching and phototoxicity.
  • Light delivery – many microscope LED light sources offer the choice between liquid light guide delivery, fibre delivery and direct fit options to best suit individual applications.
  • Support – access to technical support over the lifetime of the system is an important factor in getting the most out of the latest microscope LED light source technology available.

CoolLED’s Microscope LED Light Source Product Range

LED lighting systems are available for fluorescence microscopy and transmitted light applications.
Take a look at our product range to discover which system is best suited to your requirements.

Comparing Microscope LED light sources: Irradiance

The amount of light reaching the sample significantly impacts the brightness and contrast of fluorescence microscopy images and therefore data quality. Microscope LED light sources are therefore often compared by their ‘intensity’ or ‘power’. This has been a hot topic since LED illumination systems for fluorescence microscopy arrived on the market, as LEDs have been catching up (and in some areas of the spectrum, surpassing) conventional light sources.

The growing efficiency of LEDs leads to irradiance gains, and LEDs now typically exhibit above 30% efficiency, whereas traditional lamps are mostly below 10%. As efficiency increases this also reduces heat output, which has an added benefit, since reducing operating temperature is known to increase LED lifetime. Boosting irradiance and extending the lifetime through thermal management is such a significant factor when designing microscope LED light sources, CoolLED’s work focuses on a range of innovations in this area – for example, reducing LED temperatures through unique heatsink designs which conduct heat away from the LED much more efficiently.

When it comes to comparing microscope LED light sources, this topic has been surrounded by complex, confusing and sometimes inaccurate measurements and terminology. Even the term “intensity” is inaccurate. A key issue has been an industry-wide lack of a standardised approach to measure illumination, and we created a white paper to shed light on this topic. We have not only put forward the more accurate term of irradiance, but introduced a protocol whereby microscopists can quantify the amount of light at the sample plane and therefore directly compare microscope LED light sources to find their ideal solution.

Read our white paper to find out:

What is meant by illumination intensity and why we use the term irradiance instead

Why quantifying irradiance is crucial for fluorescence microscopy

Where irradiance should be measured and why

How to accurately and precisely measure irradiance with our method

Microscope LED Light Source White Paper

Comparing Microscope LED light sources: Spectral coverage

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).

CoolLED pE-4000 colour spectrum graph

Spectral coverage is no longer a limitation of modern microscope LED light sources. For example, our most popular range of microscope LED light sources for everyday fluorescence imaging, the pE-300 Series, provides a broad spectrum of illumination with three wavelengths and covers the excitation bands of common fluorophores such as DAPI, CFP, Aqua, FITC, TRITC, TxRed, Cy5 and many more.

Comparing Microscope LED light sources: Control

The solid-state nature of microscope LED light sources opens the way to an unprecedented level of control, which has had more impact on acquiring the perfect image than we could ever have imagined. Microscope LED light sources 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.

Some microscope LED light sources combine discrete wavelengths to produce white light, for example the CoolLED pE-300lite for everyday fluorescence imaging, and the pT-100 WHT for transmitted light applications. These can present a cost-effective option, and irradiance can still be precisely controlled in 1% steps (0-100%), allowing the illumination to be optimally matched to the experiment, balancing brightness while protecting against photobleaching and phototoxicity.

More advanced microscope LED light sources which feature individual channel control of LED wavelengths have many benefits in fluorescence imaging, as the system 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. This can be further enhanced with excitation filters, and some microscope LED light sources such as the pE-300ultra allow inline excitation filters. This is ideal for high-speed imaging applications, replacing the latency and expense of a filter wheel.

Other features to look out for are USB control and software integration, which allows the microscope LED light source to be seamlessly controlled via imaging software for convenience and speed. For high-speed imaging application, TTL control is vital, allowing the microscope LED light source to be triggered by a TTL-out on a device such as a scientific camera. With speeds up to 10 µs, such high-speed synchronisation enables the highest temporal resolution while also vastly minimising phototoxicity and photobleaching.

LED illuminator for microscope pE300 ultra light diagramComparing Microscope LED light sources: Light delivery

CoolLED is also the only company to provide direct fit products as an alternative to light delivery using a liquid light guide. This is the most efficient means of light delivery to a microscope and is our most popular type of microscope LED light source. It harnesses more power, while also reducing total cost of ownership thanks to fewer consumables. Liquid light guide delivery is available for microscope LED light sources which must be placed remotely from a microscope, for example outside of a Faraday cage. For some of our microscope LED light sources, fibre-coupling is also possible.

Comparing Microscope LED light sources: 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.

Our microscope LED light sources are renowned for their reliability, but our support goes beyond this 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.

CoolLED Team

Try it out!

If you’re interested in seeing how a microscope LED light source can enhance your microscopy illumination, we can provide a free loan unit for testing, with no obligation to purchase. Please contact us at for more information.