METHOD AND APPARATUS FOR MEASURING THE HEIGHT OF A SURFACE

A measuring device includes an illuminating unit arranged to project an illuminating light beam on a surface of a target object so as to form an illuminated region on the surface, an image sensor, and focusing optics arranged to form a focused spot on the image sensor by focusing light reflected from the illuminated region such that the position of the spot depends on the height of the surface with respect to a reference plane, wherein the device is configured to determine a height of the surface from a detected position of the focused spot, and wherein the normal of the image sensor is inclined with respect to the optical axis of the focusing optics.