Abstract: The invention refers to a method for determining the position of an elongated narrow object relative the surface of an obstructing disk-like body in front of said object and oriented at an angle thereto, by means of electromagnetic ionizing radiation, for guidance of the movement of an associated laser welding equipment For providing the carrying out of this method with high speed and greatest precision when manufacturing sandwich elements with conical or double-curved surface it is suggested according to the invention that from the side of the body remote from the object is directed, under approximate movement in the longitudinal direction of the object one precisely collimated radiation beam obliquely to the object under simultaneous scanning motion at right angles thereto, that the radiation back-scattered from the object is collected at the same side of the body and is brought to form a signal which is compared with memory-stored predetermined preference signals for the desired correct position of the obj

Abstract: A method of determining the density profile of a plate-shaped material M, the density of which varies discretely or continuously across the plate thickness, whereas the density at a specific depth of the plate M is preferably assumed to be constant. The inventive method employs X-rays or .gamma.-rays from a source K. The latter source K is placed on one side of the plate M, whereas at least two detectors T, F are arranged on the opposite side of the endless plate being advanced during the measuring in the longitudinal direction. A first detector T is preferably placed in the radiating direction of the source and measures the transmittent radiation through the plate M, and the second detector F is placed outside the radiating direction of the source K and measures the scattered radiation on partial volumes along the radiating direction of the source. Based on the signals measured by the detectors it is possible to measure the density in each individual partial volume.

Abstract: A method of non-destructively, on-line determining the density profile in a plate-shaped material with a density which varies discretely or continuously over the plate thickness, while the density at a specific depth of the plate is assumed to be constant, such as for instance plates based on wood, by means of X-rays or gamma rays from a source placed on one side of the plate. Two detectors are placed on the other side of the plate, one detector measuring in the emitting direction of the source and the other detector measuring in the other direction and being movable relative to the plate. The counting number of the second detector is adjusted by means of the counting number of the first detector. By a suitable choice of emitting direction and detecting direction it is possible to provide a measurement of the density in a specific measuring volume merely by dividing the counting number of the second detector by the counting number of the first detector.