Abstract: A method and apparatus of photoelectrically scanning a moving web material is described which comprises scanning the web with a narrow light beam sweeping across and beyond the edges of the web, directing light reflected or transmitted by the web to a light receiver of a light measuring unit so generating a corresponding electrical signal, and optically or electronically simulating the optical reflexion or transmission property of the web for two auxiliary scanning zones adjacent the lateral edges of the web in such manner that the average strength of said electrical signal remains constant over substantially the whole scanning sweep.By use of this method abrupt changes in electronic signals received by the receiver when the scanning beam traverses the edges of the web are minimized. The effect of flare is also reduced.

Abstract: An enlarger head for multigrade paper is described which comprises a light mixing system for mixing light from two sources.The system comprises disposed along a longitudinal axis a solid light-mixing member of an optically clear material which has as a light-input face a generally planar sulcated face having grooves therein of equilateral triangular cross-section and a substantially smooth light-output face, said two light sources being diametrically opposed relative to the longitudinal axis and each being adapted to direct light onto said light-mixing member from an angle substantially 60.degree.

Abstract: This invention relates to an apparatus for the detection of downlines on coated web material. The web material is transported past an inspection zone which consists of a means for projecting a narrow beam of light onto the web, means for deflecting the beam of light to scan the web repeatedly in a direction transverse to the direction of web motion, a photocell responsive to light transmitted by the web, an optical diffusing element arranged between the inspection zone and the light sensitive apparatus, and means for moving the diffusing element along a path at least partly transverse to the direction of web transport. Faults are detected by fluctuations in the photocell output.The diffuser is used so that false signals from scratches on the photocell or slight defects in the web are eliminated and it is moved so as to eliminate defects in the diffuser element surface.

Abstract: This invention relates to a method of inspecting coated web material in order to detect the presence of downlines. The coated web material is transported past an inspection station and is inspected transversely point by point across the web width. Data signals are produced responsive to variations in coated thickness. The inspection operation is repeated as the web pass the inspection station and the data signals from points at the same distance across the web width are summed to produce an average signal waveform. Any abnormal excursions of the averaged signal waveform are registered as faults.