Abstract: An apparatus for checking linear dimensions of a workpiece (10) according to the shadow casting technique, including a bed (1), a first support structure (5, 6) sustained by the bed for supporting the workpiece, a second support structure (4), optical sources (22-25) coupled to the second support structure (4) for generating associated beams of light, a plurality of linear photosensitive devices (26-29) coupled to the second support structure (4) for receiving the beams of light after they have been intercepted by the workpiece, and detecting circuits (20, 21) connected to the photosensitive devices (26-29). The optical sources (22-25) are arranged in two units (22, 23; 24, 25) at opposite sides with respect to the workpiece, and the photosensitive devices (26-29) are also arranged in two units (26, 27; 28, 29) located at opposite sides with respect to the workpiece.

Abstract: The detection of surface defects in mechanical parts is effected by the analysis of diffracted light coming from these defects. The detection method includes the steps of illuminating the surface of the part to be examined with incoherent light and forming a flat image of the said surface in a transparent photosensitive layer of a spatial light modulator. The spatial distribution of the intensity of the incoherent light reflected by the said surface produces a corresponding and proportional spatial distribution of values of refractive index in the photosensitive layer. This layer is illuminated with plane polarized, coherent light by frame scanning in elementary areas. During the scanning operation, the variations in at least one of the polarization components of the coherent light are detected by a matrix of converters after the light has traversed the said transparent photosensitive medium.

Abstract: A process for inspecting and checking the internal surface of a hollow cylindrical workpiece which has undergone mechanical working, particularly finishing by grinding or the like following which the internal surface has two sets of intersecting, helical score lines, consists in the examination of the diffraction pattern generated by laser radiation incident normally on the internal surface of the workpiece, so as to obtain a series of indications related to the characteristics of the two sets of intersecting helical score lines. The device for carrying out the process includes, as well as means for detecting the said diffraction pattern, means for providing an indication of the degree of roughness of and the presence of possible surface defects on the internal surface of the workpiece.

Abstract: Quality control inspection of the surface of a workpiece is effected by scanning a coherent monochromatic light beam over the workpiece surface. Photomultipliers are used to generate two electrical signals respectively indicative of the magnitude of the specular component of light reflected from the workpiece and of the component of light scattered in a predetermined direction off the workpiece. These two signals are combined in a manner which serves to eliminate noise due to surface roughness of the workpiece. The combined signal is compared with a threshold value to provide an indication of surface defects. The inspection apparatus can incorporate a laser for producing the light beam which can be conveniently scanned across the workpiece surface using an oscillating mirror.

Abstract: Surface roughness is tested by an optical probing method which involves scanning a beam of light from a laser over a specimen workpiece via a semi-reflecting mirror and a cylindrical lens and detecting the specular component of the light reflected back through the lens and the semi-reflecting mirror to a photomultiplier the output from which is fed to an electronic processor circuit which derive a numerical value representing the mean intensity of the reflected radiation. A workpiece to be tested is then substituted for the specimen workpiece and a new numerical value derived. The two numerical values are compared, as by division or subtraction to obtain an output signal representing the relative surface roughness of the workpiece under test with respect to that of the specimen.