Measurement of normalized spectral responsivity of digital imaging devices by using a LED-based tunable uniform source

We present an instrumentation solution for measurement of normalized spectral responsivity of digital imaging sensors and cameras. The instrument consists of multiple light-emitting diodes (LEDs), a single-grating monochromator, and a small-size integrating sphere. Wavelength tuning is achieved by a proper selection of LED in accordance with the monochromator setting in a range from 380 to 900 nm. High spectral purity with a bandwidth of 5 nm is realized without using double gratings and order-sorting filters. Experimental characteristics and calibration of the instrument are described with the related error and uncertainty sources. The performance is demonstrated by measuring a monochrome charge-coupled device and a trichromatic complementary metal-oxide-semiconductor device. The measurement uncertainty is evaluated to be less than 1% (k = 2) except several wavelengths with low LED power. (C) 2013 Optical Society of America