Patent ID: 6166808
Filing Date: 2000-12-26
Classification: G01B,G03F

Abstract:
An optical height meter for measuring the height of a first surface of a transparent object having a second reflective surface facing the first surface, said height meter comprising a radiation source for supplying a converging measuring beam whose chief ray extends at a first angle to the normal on the first surface, and a position-sensitive detection unit for detecting a radiation beam reflected by the first surface and forming a focus spot on the surface of the detector unit, said position-sensitive detection unit producing an output signal dependent upon the position of the focus spot on its surface, the chief ray of said radiation beam extending at a second angle to said normal, which angle is opposite to the first angle, and a single-apertured diaphragm being arranged between the first surface and the detection unit in the radiation path of the reflected radiation beam, characterized in that the diaphragm is arranged at such a position and has such an aperture that only said, first, reflected radiation beam can pass through said aperture and reach the detection unit, forming a single focus spot thereupon, and that a second radiation beam reflected by the second surface is blocked by the diaphragm.