Optical measuring apparatus for measuring the thickness of metals, plastic, paper and textile, the speed of metal strips, plastic ribbons, paper strips and textile bands, the length of metal strips, plastic ribbons, paper strips and textile bands, the flow of fluids and bulks, the level of liquids, the roughness and flatness of surfaces and the density of fluids and bulks; Laser-optical measuring apparatus for measuring the thickness of metals, plastic, paper and textile, the speed of metal s...