Patent ID: 9746316
Date: 2017-08-29
CPC Classifications: G01B,G01N

Claim:
1. A method of testing a substrate for defects in-line while traveling on a roller in a roll-to-roll processing operation, the method comprising the following steps: providing an interferometer including a reference surface and a camera, said interferometer having an illumination path directed to said substrate; selecting a portion of a field of view of said camera to define a size of a measurement field of view (FOV) in a longitudinal direction of the camera FOV; tilting the interferometer along a direction of substrate travel so as to enable detection of best-fringe signals within said measurement FOV; selecting an initial longitudinal position of the measurement FOV within the camera FOV based on an expected location of an initial interferometric best-fringe signal; beginning acquisition of fringe data detected by the camera during successive data acquisition steps; at selected acquisition steps following an initial acquisition step, updating a longitudinal position of the measurement FOV within the camera FOV based on a best-fringe-signal location within the camera FOV acquired during a previous step; profiling the substrate using data acquired from a current measurement FOV; analyzing profiles so generated to identify locations of defects in the substrate; and stopping further processing of the substrate at said locations of defects in the substrate.