| 摘要 |
<p>A height meter for measuring the height of a first surface (1) of a transparent object (5) is described, which height meter comprises a radiation source for supplying a converging measuring beam (11) whose chief ray extends at an angle (α) to the normal on the surface, and a radiation-sensitive detection unit (30) for detecting a radiation beam (13) reflected by the surface (1) to be measured. Since a diaphragm (40) is arranged in the path of this beam (13), it is prevented that radiation (14) reflected by a second surface (3) situated opposite the first surface can reach the detection unit. The height meter is notably suitable for an inspection device for a lithographic mask (5).</p> |
