Multiwavelength (045–106 μm) angle-resolved scatterometer or how to extend the optical window

An apparatus to record scattered light in whole space over a large range of visible and infrared wavelengths (0.45-10.6 µm) is described. Parasitic light, calibration, and dynamic range are discussed to point out performances and limits of the experimental setup. Angular measurements at several wavelengths give access to bidimensional roughness spectra of polished samples in different frequency bandwidths. The results show overlap of the spectra at the intersection of the bandwidths, which provides an extended view of surface microroughness. In the midinfrared, measurements are more difficult, and specific problems such as thermal emission are analyzed.