Abstract: Presented is a proximity monitoring apparatus and method.

Abstract: A method of determining the optical quality of a glazing which includes at least one area having a reduced light transmission, involves producing a shadowgraph image of the glazing and measuring the illumination of the glazing at a plurality of measurement points arranged in an array extending over the glazing. The deviation in illumination from a desired value at each measurement point is determined and the at least one area of reduced light transmission is omitted from the array of measurement points.

Abstract: A method of forming a shadowgraph image is described, comprising the steps of illuminating a glazing (52), e.g., a vehicle windscreen, with light from a localised light source (50), said light being expanded and collimated by a lens optical system (54) or a mirror optical system, forming a virtual shadowgraph image of the glazing in a virtual image plane (56), which may be positioned behind or in front of the glazing: and imaging the virtual image onto a CCD camera (62). The glazing may be moving relative to the light source or may be stationary.

Abstract: A multifilament sheet, tow or web of acrylonitrile precursor fibres are passed through a pre-heat zone at a temperature at least 100.degree. C below the critical temperature. The material is then passed through a two-stage oxygenation zone comprising a first stage at 220.degree. to 250.degree. C and a second stage at 260.degree. to 300.degree. C. The material passes straight through the oxygenation zone and is held in sufficient uniform tension to stretch the fibres during heating and oxygenation. The oxygenated material is then passed through a carbonizing zone comprising at least one stage at 1050.degree. to 1600.degree. C under non-oxidizing conditions. The resulting carbon fibre has a mean Young's modulus of at least 25 .times. 10.sup.6 p.s.i. and a mean tensile strength of at least 250,000 p.s.i.