Patent ID: 6842258

Claim:
A method of measuring the geometry of grooves in an elongated element, which grooves extend as continuous grooves over the whole length of the elongated element, circling around the element, in which method a surface of the elongated element is scanned by means of a camera, comprising: arranging the elongated element to travel through an opening at a vertex of an annular conical mirror, and through a plane mirror structure arranged at an oblique angle relative to the direction of travel of the elongated element; directing an annular light beam to the plane mirror structure; reflecting the light beam from the plane mirror structure onto a surface of the elongated element through an outer surface of the conical mirror; reflecting an image of a surface profile of the elongated element, produced from the surface of the elongated element by means of the conical mirror, into the camera by means of the plane mirror structure; forming the conical mirror from a biconical mirror or a biconical bevelled mirror including several plane mirrors; and arranging the image of the surface profile of the elongated element, to allow the study of the groove geometry, by means of the an inner surface of the biconical mirror or the biconical bevelled mirror.