Patent ID: 6639682
Filing Date: 2003-10-28
Classification: G01B

Abstract:
A process for determining variations in optical thickness over the working surface area of two plane parallel optical surfaces, comprising:predefining at least two points on one of the optical surfaces, each of the at least two predefined points having a respective corresponding point on the other of the optical surfaces; transmitting light, having a wavelength, through the two optical surfaces; measuring the intensity or light transmitted through said optical surfaces at each of the at least two points and its corresponding point; calculating an optical thickness between each or the at least two points and its corresponding point by comparing the wavelength and measured intensity of said light transmitted trough tat point and its cot-responding point to a model optical performance, assuming the refractive index of said piano parallel optical surfaces is constant across said working surface area; and determining the variation in the optical thickness over the working surface area, based on differences in the calculated optical thickness.