Patent ID: 7746478

Claim:
A method for interferometric measurement of an optical characteristic of a measurement area of a specimen of transparent material having two opposing main surfaces, said method comprising: (a) arranging the specimen in a measurement light beam of an interferometer such that the measurement light beam of the interferometer passes through the main surfaces of the specimen in a first surface portion of the measurement area, and performing a first interferometric measurement to obtain a first group of measurement data; (b) arranging the specimen in the measurement light beam such that the measurement beam passes through the main surfaces of the specimen in a second surface portion of the measurement area which is offset from the first surface portion and overlaps therewith in an overlap region, and performing a second interferometric measurement to obtain a second group of measurement data; (c) matching the measurement data of the first group of measurement data and the second group of measurement data using redundant information obtained in the overlap region for preparing a total interferogram on the measurement area, wherein the measurement area is fully covered with immersion fluid film, which is formed between the main surfaces of the specimen and contact bodies of transparent material.