Abstract: A method for evaluating the optical quality of a glazing using a projection technique in which the shadow of glazing (3) projected with a localized light source (2, 15) is analyzed by a camera (6) assisted by a computer. The illumination at a point (M) of screen (4) is compared to the illumination at same point (M) in the absence of glazing (3) and the measurement is weighted by the optical and geometric parameters of corresponding point (m) of glazing (3). The resolving power in one direction is adjustable by the modification of the dimension of the source in this direction. Application is to the inspection of windshields on a production line.

Abstract: The invention relates to the measurement of stresses in float glass. In a process, the stresses in the glass are continuously determined by scanning the glass over its entire width and simultaneously measuring the temperature of the glass at each location scanned. A measurement of double refraction representing stresses is combined with the temperature measurement to establish values of the permanent stresses in the glass. The invention includes apparatus for carrying out the process.