Patent ID: 8126246

Claim:
A system for determining a surface shape of a test object, comprising: a pattern including a plurality of first elements disposed about a central axis and defining an aperture containing the central axis, the first elements including a plurality of common elements having a common form and a reference element having a reference form that is different than the common form, the first elements further including a first reference element and a second reference element each having a same reference form that is different than the common form; a detector array; an optical system adapted to provide an image of the first elements when light reflects off a surface of a test object, passes through the aperture, and is received by the detector array; and a processor including an electronically readable memory, the electronically readable memory containing instructions to: identify a plurality of element images on the detector array, each of the element images corresponding to the first reference element, the second reference element, or one of the plurality of common elements; and determine a surface shape of the test object based on locations of the element images on the detector array.