Non-contact testing of optical surfaces by multiple-wavelength light scattering measurement

An instrument is described which enables the detection of backscattered light within a wide spectral region. The apparatus is based on a Coblentz sphere and is equipped with light sources from the UV to IR spectral region (248 nm - 10.6 mu m).Results are reported of measurements on samples with different surface qualities such as supersmooth Si-wafers with sub-Angström surface roughness, glass substrates, thin film optical components and machined surfaces. The set-up complies with a corresponding ISO project