What is the best type of microscope light source?

The microscope light source is a crucial component of every microscope, and the light hitting the sample can make all the difference between a breakthrough discovery and inconclusive results. Yet this component is not often given much consideration as long as it functions correctly. In fact, to many scientists it might be a surprise to realise that modern microscope light source technologies can have an incredible impact on performance, ease of use – and even sustainability.

To answer the question ‘what is the best type of microscope light source’, it first depends on the type of imaging performed, such as widefield fluorescence, transmitted illumination (such as brightfield) or calcium imaging. For these techniques, choices have previously been limited to light sources such as mercury and halogen. However, microscope light source technology has since undergone a revolution and scientists around the globe now recognise LEDs as the best option across the board.

CoolLED and the microscope light source

CoolLED designs and manufactures cutting edge microscope light source solutions for researchers and clinicians using the latest LED technology.

Since our team of four introduced the first commercially available LED microscope light source for fluorescence microscopy in 2006, we have led the way in harnessing this 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 www.OEMIllumination.com.

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    What is the best microscope light source for fluorescence microscopy?

    For widefield fluorescence microscopy, mercury and metal halide lamps have been the most popular microscope light source for a number of years. However, this is no longer the case owing to the many benefits offered by LED illumination systems:

    microscopy illumination performance

    Performance: Being solid-state, LEDs can be easily controlled, and this translates to enhanced performance. 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. In fact, speeds of under 7 µs can be achieved with TTL triggering and inline filters. LED irradiance can also be modulated electronically, balancing brightness while minimising phototoxicity and photobleaching, without the need for neutral density filters.

    When precision is important, LEDs provide the best microscope light source since they are much more stable over time, whereas irradiance declines over the lifetime of a mercury or metal halide lamp.

    microscopy illumination cost

    Cost: Since the upfront cost is higher when purchasing an LED microscope light source, continuing to replace the mercury or metal halide lamp is the best budget-friendly option in the short term. When considering cost in the long term, LEDs then become the best option with possible savings of £30,000 (read our third party report here). This is due to the longer lifetime of LEDs, lack of consumable replacements needed as in the case of lamps, and avoiding specialist disposal charges due to the high-pressure lamp and mercury content.

    microscopy illumination convenience

    Convenience: LEDs are long-lived and do not require frequent replacement like lamps. The alignment required after replacing lamps is tricky, but an LED microscope light source can be factory aligned and ready to fit the microscope. It is becoming increasingly difficult and expensive to dispose of mercury and metal halide lamps. In fact, some countries are banning mercury.

    microscopy illumination safety env

    Safety and the environment: Choosing to rely on an LED microscope light source can help laboratories become more sustainable, by saving energy and reducing the carbon footprint when compared with using mercury or metal halide lamps. This is because mercury in lamps is hazardous to people and the environment. Lamps also waste energy when they must be 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. From the environmental perspective, there is no doubt that LED microscope light source technology is the best option for widefield fluorescence microscopy.

    It is also worth considering confocal microscopy, where lasers remain the go-to technology. However, when using widefield capability to locate a region of interest prior to analysis with confocal microscopy, the same benefits as widefield systems still apply. Using gentle illumination during observation is important to avoid damaging the sample before the confocal experiment has even begun – and the controllability of LEDs makes this much easier.

    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.

    What is the best microscope light source for calcium imaging?

    Traditional arc lamps with a monochromator were previously the go-to approach for calcium imaging. This has now changed, and like other imaging techniques such as widefield fluorescence, LEDs have become the best microscope light source available due to their many benefits compared to lamps (see above). For ratiometric calcium experiments such as Fura-2 imaging, switching speed is an especially crucial factor. LED Illumination Systems such as the CoolLED pE-800fura feature 340 nm and 380 nm wavelengths and can switch with industry-leading speeds of <7 µs with TTL triggering, maximising the accuracy of measuring ratio pairs. LED microscope light source technology now provides the best solution, due to being powerful, flexible, cost-effective and controllable.

    TTL triggering graph

    TTL triggering graph

    What is the best microscope light source for transmitted illumination?

    Halogen lamps have been the traditional option for many years, however LED technology offers many benefits, with the top three being reproducibility, safety and the availability of narrow-band systems.

    Reproducibility: A key difference between LEDs and halogen is that colour temperature remains constant as LED irradiance is increased or decreased, which makes colour balancing unnecessary and improves standardisation between sessions (and labs). Samples will appear identical even though irradiance could be up to five times greater. This is particularly beneficial for pathology applications, allowing samples to be compared even under varying light exposures.

    Safety: Halogen lighting emits wavelengths in the UV, where modern LED illumination systems such as the pT-100-WHT are designed to reduce unwanted light in the UV which makes it safer and more comfortable, as risk of eye damage is significantly lower.

    Narrow-band microscope light source technology: Unlike halogen lamps, LED illumination systems enable the optimisation of image quality through narrower spectrum wavelengths, and three narrow-bandwidth CoolLED pT-100 Transmitted Illumination Systems are available. For example, the CoolLED pT-100-770 illuminates at 770 nm, providing deeper sample penetration in techniques that require the use of infrared light, such as IR-DIC.

    CoolLED pT100 narrow bandwidths - Microscope Illumination SystemLike LEDs for fluorescence applications, microscope light source technology for transmitted illumination offers many benefits in addition to the three listed above – including long lifetime, energy efficiency, instant on/off and irradiance control in 1% steps, allowing the user to easily optimise sample exposure.

    Interested? Try it out!

    If you’re not sure whether an LED microscope light source 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.