Use of Fresnel diffraction for the measurement of rotational symmetrical workpieces

The shadow projection method is used in industrial applications for quality control of turned workpieces. The workpiece is illuminated with collimated laser radiation, and the shadow of the workpiece is detected by a scan using CCD lines without lenses. The movement and rotation of the workpiece allow the control diameters and lengths at different positions, and the determination of eccentricity. Together with the measurement of surface roughness by analysis of the diffraction pattern, the complete monitoring of turned workpieces is possible, using only one scan. Results show how the extension of the shadow projection method for roughness measurement can be done.