Optical inspection of punches: flat surfaces

Optical inspection techniques for estimation of surface roughness and surface quality of flat punches, which are used in the pharmaceutical industry for tablet compression, were studied. It was observed that a simple specular reflection technique is useful for surface roughness assessment of flat punches. A diffractive element based sensor was used for the surface quality detection, such as mirror property or flatness, with the aid of image information of a test pattern. It was observed that a new punch may have a poorer surface quality than a used one.