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LED Light Sources for Microscopes

Halogen lamps have been used as light sources in microscopes in the past, but LEDs have now become mainstream. LEDs for microscopes support different lighting methods, including transmitted illumination and reflected illumination (coaxial illumination).

Learn more about these lighting methods and get tips on how to select a light source for your equipment.

Transmitted vs. Reflected Illumination: What’s the Difference?

You may need a microscope that supports either transmitted or reflected illumination.

Transmitted illumination is used with a biological microscope to observe objects that transmit light, such as thin sections of biological tissues, cells, and bacteria.

On the other hand, reflected illumination is used for observing objects that reflect light, such as metal surfaces and semiconductors with a metallurgical microscope. Reflected illumination is used in many instruments, including Raman spectrophotometers, semiconductor inspection equipment, and 3D measuring machines.

One big difference between LEDs for transmitted illumination and LEDs for reflected illumination is the size of the diameter of emitted light flux.

Since different types of condensers are used with LEDs for transmitted illumination, a larger diameter of light flux is required to illuminate things equally. The LED for reflected illumination uses one objective lens to perform the role of both an objective and condenser, so the necessary light flux diameter is smaller. The numerical aperture (NA) is perfectly matched with this design. This creates optimal focusing of light and collection of light at the sample plane.

Comparing Light Sources for Microscopy: LED vs. Halogen

LEDs benefit microscopy in many ways. Think about how these light sources stack up against halogen lamps. Despite having the same brightness as a halogen bulb, LEDs perform better than halogens in many ways.

Lifespan: It’s common knowledge that LEDs last a long time. A halogen lamp’s lifespan is around 2,000 hours, while an LED’s lifespan is around 60,000 hours, while Fewer bulb replacements and reduces environmental waste are just a few of the benefits of a longer lifespan, saving both time and money.

Heat: LEDs also have don’t heat up like halogen and have a more stable output. A hot lamp can harm samples and heat up your workspace. LEDs enable comfortable, long-term observation as a cool and stable light source. Responsiveness: The high responsiveness of LEDs lets you immediately start observation, compared to halogen lamps that are much slower to emit bright light.

Color temperature change: LEDs maintain a consistent color temperature when you adjust the light intensity, unlike halogen lamps. The ability to freely control the light intensity reduces potential damage to the sample from strong light. Consistent color temperatures reduce eye strain, as your eyes don’t have to adapt to the changes in color.

Size: LEDs are usually more compact than halogen lamps, making them easy to integrate even as devices become smaller.

Color Rendering Performance in LEDs vs. Halogen

For general white LEDs, such as BX3M-LEDR or BX3M-LEDT, color rendering is lower than halogen lamps. On the other hand, True Color LEDs, such as our U-LHLEDC/U-LHLEDC100 LEDs, have color rendering similar to halogen lamps. True Color LEDs are best for applications where high color rendering is required, such as observing biological specimens with transmitted illumination.

Spectral Characteristics of a Halogen Lamp and an LED

In transmitted illumination applications, light intensity across the visible spectrum is important for accurately reproducing the colors in stained biological samples. Halogens used to outperform LEDs in this area, as the light intensity of general white LEDs can vary at different wavelengths. However, True Color LEDs closely match the spectral characteristics of halogen for accurate color representation.

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