Patent ID: 7633046

Claim:
A method for estimating thread parameters of a part which moves relative to a stage and a plurality of sensors which measure the amount of radiation contained in directed planar portions of radiation unobstructed by the part wherein the amount of radiation is representative of a respective geometric dimension of the part, the method comprising: obtaining calibrated part data from an inspection region between position limits of the stage, the calibrated part data including calibrated sensor data for each sensor of the system and its corresponding coordinate system, the calibrated sensor data being based on amount of radiation contained in directed planar portions of radiation unobstructed by the part; processing the calibrated part data to obtain intermediate data including crossing data wherein the step of processing includes the step of correlating a thread model with the calibrated sensor data within the inspection region to obtain the crossing data; and analyzing the intermediate data including the crossing data to produce estimates of the thread parameters of the part without the need to measure radiation reflected by the part.