Patent ID: 8068234
Filing Date: 2011-11-29
Classification: G01B

Abstract:
1. An interferometer apparatus for measuring shape or thickness information of a substrate including in combination: first and second spaced apart reference flats having corresponding first and second parallel reference surfaces forming an optical cavity therebetween for placement of the substrate; a substrate holder configured to place the substrate in the cavity between the reference flats such that first and second surfaces of the substrate are substantially parallel with corresponding first and second reference surfaces of the first and second reference flats and such that the first or second surface of the substrate is 3 millimeters or less from a corresponding one of the first or second reference flat, the proximity between the first or second surface of the substrate and the corresponding reference surface of the first or second reference flat being sufficiently close to shield the substrate from vibration; and first and second interferometer devices located on diametrically opposite sides of the cavity and optically coupled thereto, the first and second interferometers being respectively operable to map variations in spacing between the first and second surfaces of the substrate and the first and second reference surfaces, respectively through interference of light optically coupled to and from to the cavity via the first and second interferometer devices.