Patent ID: 7877227
Filing Date: 2011-01-25
Classification: G01B

Abstract:
1. A surface measurement instrument for obtaining surface characteristic data of a sample surface, the apparatus comprising: an adjustable sample support; a beam splitter operable to direct light along a sample light path towards a region of a surface of a sample mounted on the adjustable sample support and along a reference light path towards a reference surface such that light reflected by the region of the sample surface and light reflected by the reference surface interfere; a mover operable to effect relative movement along a measurement path between the adjustable sample support and the reference surface; a sensor operable to sense light representing the interference fringes produced by each of a plurality of surface pixels of a sample surface region during said relative movement; a controller operable, in order to effect a measurement operation, to cause said mover to effect said relative movement while said sensor senses light intensity at intervals along a scan path to provide a series of intensity values representing interference fringes produced by a region of a sample surface during said relative movement; and a data processor operable to process provided intensity values to derive surface characteristic data for the surface pixels, wherein the adjustable sample support is translatable in a plane perpendicular to and tiltable relative to the direction in which light is incident on the sample surface region and wherein an adjustor is provided which is operable to tilt the adjustable support and to translate the adjustable support to compensate for movement of the surface region in said plane so that, during a measurement operation, light is incident normally of the sample surface region; and wherein the adjustor comprises a tilt determiner operable to determine the tilt of the sample surface region relative to the sample light path and a mover determiner operable to determine from the determined tilt the degree by which the adjustable sample support needs to be tilted and the amount by which the adjustable sample support needs to be translated so that, during a measurement operation, light is incident normally of the sample surface region.