Surface characteristic determining apparatus

Abstract

A wavelength selector () selects a wavelength of a broadband light source (). A light director (BS, BS) directs light from the wavelength selector along a measurement path towards a region of a sample surface and along a reference path towards a reference surface, such that light reflected by the region of the sample surface and light reflected by the reference surface interfere to produce an interferogram. A controller () controls the wavelength selector to change the wavelength selected by the wavelength selector. A recorder () records successive images, each image representing the interferogram produced by a respective one of the wavelengths selected by the wavelength selector. A data processor () processes the recorded images to produce at least one of a surface profile and a surface height map of at least a part of the sample surface. The reference path may be controlled to compensate for environmental effects such as vibration, thermal effects and air turbulence. The data processor may use a graphics processing unit to enable pixel data to be processed in parallel.