Process and apparatus for the detection of flaws in transparent sheets of glass

An apparatus for permitting the examination of transparent sheets for detecting flaws in a sheet and for discriminating between the flaws and opaque foreign bodies deposited on the transparent sheet, comprising means for moving the sheets, a light source located below the transparent sheet to be checked, said light source being thin and linear and arranged at a 45.degree. angle in relation to the direction of movement of the sheet, said light source being parallel to the horizontal plane of said sheet and being parallel to a vertical plane containing an optical axis of a convergent optical system and a linear network of photodiodes which constitute a receiving organ for the light from the light source, said light source being located at a distance (x) relative to the vertical plane such that the linear network is externally tangent to a fringe of a fuzzy real image produced by the optical system in a plane of the network of photodiodes, the lengths and positions of the light source and of the network of photodiodes being such that the fuzzy real image which the optical system produces of the light source in the plane of the network, covers the length of this network whereby sweeping of the whole of the surface of the sheet is accomplished without any moving mechanical element interposed between the light source and the network of photodiodes, adjustment means for maintaining constant both the distance (x) at which the light source is located from the vertical plane containing both the optical axis of convergent optical system and the linear network of photodiodes and the parallelism of the light source with the vertical plane such that the optical gain will always be optimal over the whole length of the linear network in spite of the variations in either the nature of the transparent sheet to be checked or dimensional variations of a chassis of the apparatus, said adjustment means includes a plate for mounting the linear network of photodiodes, said plate being provided with two toothed circular sectors diametrically opposed on each side of the network and a worm screw associated with each of the circular sectors activating the circular sectors either simultaneously or individually at equal or different speeds and in the same direction or in opposite directions, said worm screws being driven by two motors step by step controlled independently from each other in response to the amount of light received by each one of photodiodes, whereby the network can be moved automatically either in a direction parallel to itself or at an angle and the network may be subjected to two simultaneous movements so as to be moved on the resultant of the movement to a desired value (kx), K being the coefficient of reduction of the optical system.

An apparatus for permitting the examination of transparent sheets for detecting flaws in a sheet and for discriminating between the flaws and opaque foreign bodies deposited on the transparent sheet, comprising means for moving the sheets, a light source located below the transparent sheet to be checked, said light source being thin and linear and arranged at a 45.degree. angle in relation to the direction of movement of the sheet, said light source being parallel to the horizontal plane of said sheet and being parallel to a vertical plane containing an optical axis of a convergent optical system and a linear network of photodiodes which constitute a light receptor element for the light from the light source, said light source being located at a distance (x) relative to the vertical plane such that the linear network is externally tangent to a fringe of a fuzzy real image produced by the optical system in a plane of the network of photodiodes, said plane also containing a clear, real image of the sheet, the lengths and positions of the light source and of the network of photodiodes being such that the fuzzy real image which the optical system produces of the light source in the plane of the network, covers the length of this network whereby scanning of the whole of the surface of the sheet is accomplished without any moving mechanical element interposed between the light source and the network of photodiodes with a frequency of said scanning determined by computer control.

An apparatus for permitting the examination of transparent sheets for detecting flaws in a sheet and for discriminating between the flaws and opaque foreign bodies deposited on the transparent sheet, comprising means for moving the sheets, a light source located below the transparent sheet to be checked, said light source being thin and linear and arranged at a 45.degree. angle in relation to the direction of movement of the sheet, said light source being parallel to the horizontal plane of said sheet and being parallel to a vertical plane containing an optical axis of a convergent optical system and a linear network of photodiodes which constitute a light receptor element for the light from the light source, said light source being located at a distance of (x) relative to the vertical plane such that the linear network is externally tangent to a fringe of a fuzzy real image produced by the optical system in a plane of the network of photodiodes, the lengths and positions of the light source and of the network of photodiodes being such that the fuzzy real image which the optical system produces of the light source in the plane of the network, covers the length of this network whereby sweeping of the whole of the surface of the sheet is accomplished without any moving mechanical element interposed between the light source and the network of photodiodes, electric signals provided by each of the photodiodes of the detecting network are sent, after being amplified, to a comparator, said comparator also receiving data relating both to a light threshold of the fringe of the fuzzy image and to a fault threshold indicative of illumination level indicative of the refraction of the light beam, a captor computer for individually memorizing and analyzing the data, said captor computer providing results for a transmitter receiving station which also receives data from a tachometer which provides data concerning the speed of movement of the transparent sheet for aiding in the determination of the coordinates of the flaw detected, a decision computer receiving results from the transmitter receiver station, said decision computer providing orders to elements of the apparatus including a power amplifier for adjusting the intensity of the light source in order to maintain constant the light intensity in the linear network, a device for electronic adjustment of the sweeping frequency of the photodiodes in relation to the speed data received by the tachometer, and a marking device which marks the location of any detected flaws in the glass, said captor computer controlling adjustment means for maintaining constant both the distance (x) of the photodiode network in relation to the image of the light source as well as the parallelism of the network in relation to the light source.