| abstract |
Apparatus for the inspection of the surface of a cylindrical object which comprises means (41, 42) for rotating the object to be inspected about its axis, projection means (1) for projecting an incident beam (3) of radiation to form a spot on the surface of the object (5, 47) whilst the object is rotating, means (79, 83) for providing relative to the object when being rotated translation of the spot formed by the projection means, detector means (9) for detecting a scattered beam (6) of radiation which comprises radiation of the incident beam after scattering by the surface of the object and means (13, 15, 17) for deriving from the detection by the detection means of the scattered beam information about the depth of the surface of the inspected object in the region where the incident beam spot is applied. n The incident beam provided by the projection means and the scattered beam detected by the detector means are desirably at an angle to one another, whereby the position of incidence of the scattered beam on the detector means provides a measure of the depth of the surface of the object from which the incident beam spot is scattered, the detector means comprising a position sensitive detector which produces an output which represents the lateral position of the detected spot formed by the scattered beam which itself is a measure of the depth of the object reflecting surface relative to a datum value. |