Patent ID: 7570372

Claim:
An optical device for measuring a thickness of a first medium that is at least partially transparent for an incident beam and covers a second medium, the device comprising: means for generating the incident light beam so as to form a reflected beam reflected by the surface of the first medium and a scattered beam scattered by a surface of the second medium; detection means for detecting the reflected beam and the scattered beam; processing means connected to the detection means, the processing means having means for measuring a gap between the reflected beam and the scattered beam and means for determining the thickness of the first medium according to the measured gap, wherein the detection means has means for measuring a position of at least one of the reflected beam and scattered beam, the processing means has means for determining the distance between the detection means and the surface of the second medium, according to the measured position, and means for correcting the value of the thickness of the first medium, according to said distance, the position is a point at which the at least one of the reflected beam and the scattered beam impacts the detection means, and the gap is the distance between a point of impact of the reflected beam and a point of impact of the scattered beam on the detection means.