Methods and apparatus for measuring a thickness of a coating on an moving object are provided. Light is directed toward the object at a predetermined location on the object such that a portion of the light interacts with the object. A I D and/or 2D maximum intensities for at least one wavelength channel is captured that is produced by the portion of the light interacting with the object. A measured average intensity of the wavelength channel and/or intensities and their arithmetic derivatives of multi wavelength channel geometries is converted into I D (averaged) and/or 2D thickness values. Based on these values an acceptability of the coating is evaluated and thickness calculated.