Abstract: A method and device for measuring the distance between first and second positions on an inside surface of a metal part that includes locating a metal probe within the part, applying a voltage across the probe and part, measuring the capacitance between the probe and part, moving the probe toward the first position until a predetermined capacitance is measured, moving the probe toward the second position until the predetermined capacitance is measured, determining the distance travelled by the probe between the first and second positions, and adding to the determined distance a known value to compensate for the width of the probe and the distance between the probe and part when the predetermined capacitance is measured.

Abstract: A device for measuring an object includes a laser beam, a translator for moving the object with respect to the beam, an object reference plane which is the plane perpendicular to the beam that is first entered by the object, a lens system for imaging a light pattern formed in a second plane onto a first plane, wherein the second plane is adjacent to the object reference plane, and the light pattern includes a diffraction pattern caused by interaction of the beam and the object, a slit interposed at the first plane for limiting the extent of the beam that passes through the first plane, and a photodetector that emits a signal representative of the light received behind the slit for detecting the portion of the beam that passes through this slit. The slit is sufficiently small so as to enable resolution of the diffraction pattern by the photodetector. The device further includes a circuit for calculating a dimension of the object in response to the signal emitted by the photodetector.

Abstract: The present invention relates to a method of and apparatus for measuring the width of an object. The object is moved across a first beam and a photodetector produces a signal indicating when the object is eclipsing the beam. An interferometer is trained on a device for moving the object across the beam and is used to calculate the distance the moving device travels while the object is eclipsing the beam. From that distance, the width of the object can be calculated.