| 摘要 |
An arrangement for coating a surface preparatory to optical inspection. The surface to be inspected for geometrical, physical or chemical characteristics, is cooled to a temperature below freezing. The surface is then sprayed with water and a layer of frost is allowed to form on the surface. The cooling procedure may be achieved by refrigeration coils or by cold air applied to surfaces of objects to be inspected, as the objects proceed along a conveyor belt on a path to an optical inspection station. The water spray may be in the form of low pressure water vapor whereby a thin layer of frost or water droplets coat the objects. The objects are kept cool during the inspection process, and they are not allowed to warm up to room temperature until the inspection process is completed. The frost or water droplets disappear after the objects are permitted to warm up, so that the coating applied prior to the optical inspection, is removed in an efficient manner at negligible cost. The frost or water droplets provide support to optical inspection methods which are best satisfied by lambertian reflectance characteristics.
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