Patent ID: 8268385

Claim:
A method of compensating for layer thickness errors during deposition of a multilayer coating on a substrate, comprising the steps of: (1) providing a coating design specifying a substrate material and a layer material and a layer design thickness for each layer of the multilayer coating; (2) calculating an expected ending optical admittance for each layer of the multilayer coating, said expected ending optical admittance for a currently deposited layer serving as an expected beginning optical admittance for a next deposited layer of the multilayer coating; (3) monitoring a reflectance parameter as a function of time for light of a predetermined wavelength during deposition of a first coating layer on the substrate and during deposition of each currently deposited layer on a previously deposited layer to form the multilayer coating; (4) depositing a predetermined fraction of the currently deposited layer of the multilayer coating on the previously deposited layer of the multilayer coating and recording the reflectance parameter as a function of time to provide a measured reflectance curve; (5) determining an actual thickness of the previously deposited layer by comparing an expected reflectance curve based on an adjusted previous layer thickness with the measured reflectance curve of step (4); (6) adjusting the design thicknesses for the currently deposited layer and a next deposited layer to compensate for any difference between the actual thickness and the layer design thickness for the previously deposited layer; (7) completing deposition of the currently deposited layer to the adjusted design thickness from step (6); and (8) repeating steps (4)-(7) for the next deposited layer until all of the layers of the multilayer coating are deposited.