Measuring the reflectance spectrum of an object can be accomplished in numerous ways, including a single-point spectrometer coupled to a two-dimensional scanning system, a linescan spectrograph combined with a digital camera, a colored filter wheel and a monochrome camera, or a digital camera and a liquid-crystal tunable filter, among others. These numerous multispectral imaging systems all have tradeoffs in terms of measurement speed and spectral and spatial resolution; however, each of them has in common a rather expensive and complex optical illumination system.
Researchers at the University of Eastern Finland (Kuopio, Finland) have instead developed a simplified multispectral imaging system that pairs 17 light-emitting diodes (LEDs) synchronously switched with a digital monochrome CMOS camera for image acquisition at a high frame rate. The approach is only applicable to objects with smooth spectra. Spanning a wavelength range from 400 to 700 nm, the system was able to accurately reproduce the reflectance spectra of red, yellow, and blue color-chip samples from the Munsell book with magnitudes that deviated from the original spectra by less than 10%. The system is a fast, simple, and low-cost solution for the measurement of reflection/absorption spectra and its dynamics. Multispectral imaging of various objects including biological samples is underway.
Contact Laure Fauch atlaure.fauch@uef.fi.
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