Scatterometer for measuring the 3D distribution of transmitted energy from coatings in IR imaging systems

A non-goniometric infrared scatterometry technique that measures the transmitted energy scattered within defined annular-aperture zonal volumes by optics such as bandpass filter coatings is described. The measured annulus-resolved scattered (AnRS) energy directly corresponds to the distribution within the focal cone of imaging optics. AnRS applies to optical systems that require minimizing image contrast reduction that can be caused by scatter from coated optics located near image sensor arrays. The prototype AnRS instrument demonstrates the proof of concept on sample IR filter coatings. The technique is limited in spectral applicability only by the properties of the detector and optics.