Patent ID: 6674058
Filing Date: 2004-01-06
Classification: G02B

Abstract:
A method for determining an optimal focal distance, said method comprising,changing a distance along an optical axis between an objective and a substrate to establish a plurality of focal distances, transmitting laser light through said objective at said plurality of focal distances onto said substrate at each of a plurality of locations, wherein the substrate has a periphery and at least one of the plurality of locations is within the periphery of the substrate, receiving a plurality of reflected components of said laser light through said objective at each of said plurality of locations, wherein each of said plurality of reflected components is received at a corresponding one of said plurality of focal distances and from a corresponding one of said plurality of locations, processing said plurality of reflected components corresponding to each of said plurality of focal distances at each of said plurality of locations to determine said optimal focal distance for each of said plurality of locations, and wherein said laser light and said objective also enable measurement of characteristics of a test sample placed on said substrate.