Comparing microscope illumination systems

Whether using fluorescence microscopy or transmitted light methods, the light hitting a sample can make the difference between a breakthrough discovery and inconclusive results. Selecting the optimal microscope illumination system is therefore crucial. Until recently, choices were limited to mercury or metal halide for widefield fluorescence or halogen lamps for transmitted light. Since LED microscope illumination systems arrived on the market, scientists around the globe are increasingly moving towards this technology due to its many benefits. We look at where the technology is today and compare LED microscope illumination systems, to help microscopists select the optimum system for their needs.

CoolLED and microscope illumination systems

CoolLED designs and manufactures cutting edge LED microscope Illumination Systems for researchers and clinicians using the latest LED technology.

Since our team of four introduced the first commercially available LED microscope illumination system for fluorescence microscopy in 2006, we have led the way in illumination technology for fluorescence and transmitted applications. Now we are a fast-growing company in Hampshire, UK, with a vast product range and technical expertise spanning optical engineering and the life sciences.

We also understand that something out of the ordinary is sometimes required, and manufacturers wishing to gain a competitive advantage can now access our world-renowned LED technology in customised configurations at

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    LED versus mercury and metal halide microscope illumination systems

    For widefield fluorescence microscopy, LED microscope illumination systems offer many benefits compared to conventional mercury and metal halide lamps:

    microscopy illumination performance

    Performance: LEDs are much more stable over time, whereas irradiance declines over the lifetime of a mercury or metal halide lamp. Historically, the irradiance of LEDs was considered low, and although this can still haunt its reputation, the technology has now matured and LEDs are equivalent or brighter in many areas of the spectrum. As the growing efficiency of LEDs leads to irradiance gains, 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 LED Illumination Systems, 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.

    microscopy illumination cost

    Cost: Although the upfront cost is higher for switching to LED microscope illumination systems, the long-term cost is lower and a saving of £30,000 could be made (read our third party report here). This is due to the longer lifetime of LEDs and lack of consumable replacements needed as in the case of lamps. Specialist disposal charges due to the high-pressure lamp and mercury content are also avoided.

    microscopy illumination controls

    Control: Being solid-state, 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. With TTL triggering and inline filters, speeds of up to 10 µs can be achieved. LED irradiance can also be modulated electronically, balancing brightness while minimising phototoxicity and photobleaching, without the need for neutral density filters.

    microscopy illumination convenience

    Convenience: Lamps frequently need replacing, whereas LEDs are long-lived. The alignment required after replacing lamps is tricky, but LED microscope illumination systems can be factory aligned and are ready to be fitted to the microscope. It is becoming increasingly difficult to dispose of mercury and metal halide lamps. In fact, some countries are banning mercury.

    microscopy illumination safety env

    Safety and the environment: Mercury in lamps is hazardous to people and the environment. Lamps 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. Adopting LED microscope illumination systems can help laboratories become more sustainable, saving energy and reducing the carbon footprint when compared with using mercury or metal halide lamps.

    Since the energy cost is just a fraction of that used by mercury and metal halide, many institutions offer “Green Grants” to support the purchase of energy-efficient equipment. If you want to find out more about the sustainable benefits, watch this interview from Anna Lewis at the University of Bristol:

    CoolLED’s Microscope Illumination System 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 illumination systems for transmitted illumination

    As is the case with fluorescence microscopy, LED microscope illumination systems also offer improved control when compared to traditional halogen lamps for transmitted light applications, with instant on/off and irradiance control in 1% steps.

    Laboratories familiar with halogen lamps will find that the broad white of modern LED microscope illumination systems, such as the CoolLED pT-100 WHT achieves results which make the move to LEDs simple and apparent, and this reproducibility is ideal for pathology applications.

    Colour temperature remains constant as irradiance is increased which makes colour balancing unnecessary and improves standardisation between sessions. Samples will appear identical even though irradiance could be up to five times greater.

    CoolLED pT 100 WHT colour temperature comparison - Microscope Illumination System

    In addition, these microscope illumination systems do not produce unwanted light in the UV which makes it safer and more comfortable especially for long hours spent at the microscope, as risk of eye damage is significantly lower.

    Unlike halogen, with LED microscope illumination systems the availability of narrow bandwidth options optimises image quality through increased contrast. These even range up to 770 nm, which enables visualising through thick tissue samples.

    CoolLED pT100 narrow bandwidths - Microscope Illumination System

    Find out more

    There are many benefits to adopting the latest LED microscope illumination systems. For more information on choosing the right microscope illumination system for your needs, contact us or find your local CoolLED reseller.