High-grade uniform light source for radiometric and photometric applications

Abstract

Versatile applications in radiometry and photometry require uniform light source systems with a highly Lambertian radiance/luminance output. Examples for this kind of requirements include different applications such as calibration of photometers and radiometers, testing of electronic imaging devices like CCDs or similar array detectors or the use as a homogenous light source in, for instance, gonioreflectometric measurements. At the Physikalisch-Technische Bundesanstalt (PTB) a homogenous sphere radiator consisting of a medium sized integrating sphere (ϕ = 150 mm) with an internal reflector in the equatorial plane was developed. In its first stage of development it was equipped with an internal 250 W quartz tungsten halogen lamp. This sphere radiator had a radiance homogeneity of 99.8% of the emitted radiation measured in the plane of the limiting aperture (ϕ = 40 mm) at the output of the device. In the latest design of the system the radiative output power could be increased by a factor of about 3 by the use of an internal 400 W quartz tungsten halogen lamp while nearly maintaining homogeneity.