Goniometric scanning radiometer

Abstract

A gonioradiometric scanning apparatus and method for measuring the near and/or far field radiation pattern of radiating optical sources such as laser diodes (LD), light emitting diodes (LED), optical fibers, flat panel displays, and luminaires is described. The scanning apparatus incorporates a deflector for selecting an azimuth angle through the optical source to be measured, a rotating apparatus which collects light while scanning about the source, an optical commutator, and a detector. The rotating apparatus comprises a cylindrical hub and an optical collector using either an optical fiber or a train of reflectors, such as mirrors or retro-reflectors. The optical collector provides a means for both collecting light and for directing the beam emanating from the deflector to a place opposite the detector at which optical commutation occurs. The reflector optical train, when employed, folds the optical path and increases the effective radius of measurement, so that large radius scans can be obtained in an instrument with compact geometry. Depending on the source geometry and the effective optical path, the light collection can be either in the near field or the far field of the source radiation pattern. For the case of the far field radiation pattern, it will also be possible to measure the near field radiation patterns by imaging the source onto the light collection surface.