Optical distance sensor with tilt error correction

摘要

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.

主权项

1. An optical sensor for measuring a distance to an object surface, the optical sensor comprising:
an illumination system including a radiation source for supplying a measuring beam; a focusing unit for focusing the measuring beam to a spot on the object surface; a detection system comprising:
a radiation-sensitive detector for converting measuring beam radiation reflected from the object surface into an electrical signal representing a measured distance, anda signal processing circuit for processing the electrical signal; and a pupil-sensing system configured to determine tilt of the object surface from a pupil radiation distribution and comprising:
a beam splitter, arranged between the focusing unit and the radiation-sensitive detector, for splitting a reflected measuring beam into a pupil-sensor beam and a distance measuring beam, anda position-sensitive detector, arranged in a path of the pupil-sensor beam such that the pupil-sensor beam incident on the position-sensitive detector is a collimated beam and the position-sensitive detector converts the pupil-radiation-distribution into pupil-sensor electrical signals that represent tilt of the object surface, the pupil-sensor electrical signals being suited for comparing with values of a look-up table obtained from calibration and finally for coupling to the signal processing circuit to correct the measured distance for tilt of the object surface area being measured.