Method of testing transparent sheets of material

摘要

In testing window glass and other transparent sheets of material for defects included in the sheet, the sheet of material is scanned across its width with a flying light spot and the transmitted or reflected radiation is collected. The radiation is converted into electrical signals and evaluated, radiation emerging laterally from the sheet being additionally detected during the scanning cycle and converted into electrical pulses which are used to control the sensitivity of the evaluation. This detects foreign bodies or gas bubbles which are included in the sheet of material and which do not manifest themselves in the surface. The flying light spot is produced by a laser beam generator which emits radiation of a wavelength equivalent to the colouration of the sheet of material.