Optronic Laboratories Inc.’s OL 771 is a photodiode array-based spectroradiometer system that measures LEDs and LED clusters and chips. A rugged and portable enclosure houses the control electronics, the internal spectrograph and the detector. The system has RS-232 and USB interfaces. Optical input to the spectrograph, which is based on an aberration-corrected, concave, flat-field diffraction grating, is via a fiber optic cable. Wavelength range is from 380 to 780 nm, with accuracy of ±0.5 nm. Optical bandwidth with a 100-μm slit is 2 nm, spectral resolution is ∼0.4 nm, optical focus length is 140 mm, and the optical aperture is f/2. Operating temperature is from 0 to 40 °C.