A Spectroscopic Reflectometer is a type of optical instrument used to measure the reflectance of a material. It works by shining a light beam onto a sample surface and measuring the amount of light that is reflected back into a detector. The instrument is then able to measure the reflectance of the material for different wavelengths of light, giving a spectrum of reflectance values. This data can be used to determine the optical characteristics of the material and can be used to identify different substances, detect surface defects and monitor the quality of surfaces.