Source improves colour calibrations

Researchers at NIST have developed a new portable ‘rainbow’ source for calibrating colour measurement instruments.

Researchers at NIST have developed a ‘rainbow source’ that can be tuned across the entire visible light spectrum, from red to blue light. This unique source exploits recent materials advances in light-emitting diodes (LEDs) of different colours.

By mixing exact percentages of LEDs at different wavelengths of visible light with the desired brightness, the optical properties of the source (such as the colour) can be changed and tailored for a particular application. To develop the device, NIST researchers characterised commercial LEDs and developed the packaging, electronics and software.

The tuneable light source is highly portable. It is a sphere about 30 cm (1 foot) in diameter and weighs about two kilograms (5 pounds). Battery operated versions have been developed for field applications.

NIST researchers described the invention on April 14 at the Ocean Color Research Team Meeting in Washington, DC.

The National Oceanic and Atmospheric Administration has ordered a simplified version of the source to reduce uncertainties in calibrations of a satellite that measures ocean colour, as part of a program that monitors the carbon balance between the ocean and atmosphere.

The source could also simplify colour calibrations in industrial and other research applications.

Additional details will be presented at a meeting at NIST in Gaithersburg, MD on May 10-14.

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