|Figure 1: With an LED light source, light from the excitation spectrum will spill into the emission spectrum.|
|Figure 2: The sharp bandwidth of a laser does not require an excitation filter lowering complexity and cost.|
- Unlike a laser light source, the half-bandwidth of an LED is large, requiring extra filtering for fluorophore excitation.
With an LED light source, light from the excitation spectrum will spill into the emission spectrum. An additional filter, called an excitation filter, has to be added to an LED light source in order to ensure valid results, adding costs that are often not accounted for when assessing light sources.
On the other hand, the sharp bandwidth of a laser does not require an excitation filter, which lowers complexity and system cost.
- LEDs force design compromises for product manufacturers serving the life sciences industry.
The automotive industry and general lighting applications commonly use LED light sources. Demand is so high that LED manufacturers are focused on these markets. These applications do not require the wavelengths to be as narrowly defined as in life sciences. As a result, it can be hard to order the specific LED wavelength necessary for life science applications.
Compared to automotive and general lighting, the scale of demand for light sources within life sciences is small. Therefore, LED manufacturers have to resort to cost saving measures to serve this industry with practices like the wavelength binning process.
Manufacturers produce LEDs within their specified ranges (or “bins”) of wavelengths. This is not the case for laser manufacturers. Laser wavelengths have a much narrower range. The LED wavelength binning process forces product designers in the life sciences to amend their designs to fit the LED manufacturers’ specifications.
The higher numerical aperture (NA) of an LED light source requires a larger investment in optics and power rating.
Given the diffuse nature of an LED beam, 2 additional investments are needed that are not necessary for a laser light source:
- The investment in optics required for an LED to successfully focus on its target is significantly larger than that required of a laser light source.
- Due to the less efficient beam, an LED requires a higher power rating than a laser to achieve the same illumination. As a result, the LED drive circuitry is larger, more costly and generates additional heat.
These points were originally made following my return from The Vision Show in Boston on April 15, 2014