Abstract: In an optical distance sensor for measuring object surfaces with high precision and comprising an objective lens for focusing a measuring beam to a measuring spot on the surfaces, measuring errors due to tilt of an object surface can be detected by using a pupil monitor, which senses the radiation intensity distribution of the reflected measuring beam effectively in the pupil of the objective lens to generate a tilt signal, which can be supplied to a correction/calibration table to obtain a correction signal, which is suitable for correcting the primary distance measuring signal of the sensor. Especially for a differential confocal distance sensor having pinholes arranged in front of radiation-sensitive detectors, a further order of correction can be obtained by determining optimum position and diameter of these pinholes.

Abstract: In a optical sensor (30) for measuring object surfaces (2) with high precision, measuring errors due to tilt of an object surface can be corrected by using a pupil monitor (72), which senses the intensity distribution of the reflected measuring beam (b?) in combination with a correction/calibration table (76) and use the monitor signal to correct the primary measuring signal (FES) of the sensor. Especially for a differential confocal sensor, a further order of correction can be obtained by determining optimum position and diameter of the pinholes. The measurement beam is directed to an object via a beams splitter cube and an objective that focuses the beam on an object surface. Light is received back from the object surface through the objective and split off by the splitter, from where it is directed to a sensor. In order to increase the measurement range the objective is mounted on an actuator. An interferometer is used to measure the position of the objective.

Abstract: The invention relates to a method of reconstructing a surface topology of a surface (1) of an object (2). Conventional methods such as interferometry, or methods which acquire measurement values which represent slopes of the surface profile (slope values), show only a limited height resolution in the case of large flat objects such as wafers. In order to overcome this problem the surface of the object is sub-divided into smaller areas, and from each area slope values are obtained at optimum apparatus parameters. Then the areas are stitched together and the 3D topography is reconstructed.

Abstract: The invention refers to an apparatus for mapping a surface profile of a surface of an object, by which the apparatus yields slope data. The slope data of the apparatus may comprise measurement errors, which according to the invention shall be detected and corrected for. It is suggested that a computational entity calculates for all measurement values the curl of the slope data for determining surface locations at which the measurement values exhibit measurement errors. In a second step the proposal is given with which the measurement values can be corrected.

Abstract: A post-objective scanning device using a rotatable polygon mirror has a correction system for achieving telecentric scanning with a well-corrected scanning spot. A mirror facet tracker is provided to obtain high radiation efficiency and optimum use of the correction system. The facet tracker may be an active device including an additional beam deflector or a passive device including a facet tracking mirror.