Abstract: Apparatus for adjusting the position of an edge between two surface porti of a moving belt with different spectral reflectivities where required in connection with work or treatment needed along the edge of one of the two surface portions while the belt is moving. It is a pre-requisite condition that the mutually adjacent surfaces of the belt are sufficiently significantly optically detectable which is impaired, for example, in the presence of surface contamination by dirt and the like. In order to obtain a significant signal in such circumstances, the edge region is illuminated and an imaging or focussing lens associated with a beam splitter is arranged in the focus beam. Following the beam splitter the two part-beams pass through one filter each to impinge on in each case a photodiode receiver, each filter blocking passage in that wavelength range in which the other filter is transmissive.

Abstract: Apparatus is disclosed for determining the position of a surface in which radiation from an optical radiant source is applied to the surface and, by means of a lens system, an image of the radiation is produced on a photoelectric receiver. A laser serves as the radiant source, and is aimed at an angle of inclination relative to an optical axis of the lens system at a point of a surface which, by virtue of its temperature, emits visible radiation in the same wavelength range as the Laser. The surface extends approximately perpendicularly of the optical axis and is subject to positional variations along the said optical axis. The beam is directed from the irradiated point to the photoelectric receiver through a narrow-band optical filter of which the pass band includes the laser wavelength.

Abstract: In measuring the width of rolled stock, a photo-sensitive diode array overlying an edge of the stock is scanned to provide an indication of the position of the edge of the stock, the outputs of the diodes appearing serially to provide a waveform. To find the step in this waveform which represents the edge, the waveform is filtered to replace falling edges by shallow slopes and rising edges are detected in a peak rectifier/capacitor arrangement which can only discharge slowly. An output comparator is triggered in each cycle (except the first) by any rising edge signal which causes charging of the peak storage capacitor. The output comparator signal indicates the position in the scanning cycle of the article edge.