A complete procedure to reconstruct part shape using a 3-light photometric stereo technique is investigated and
experimentally verified. The part reflectance parameters are initially estimated and then the photometric stereo technique
is applied at selected illumination directions. Finally, the recovered surface normals are integrated to reconstruct the part
shape.
The light sources are placed at 120° azimuth angle spacing while the slant angle is optimized according to the range of
slopes found in the part surface. For a free form surface with small radii of curvature, a 45° light source slant angle is
found to give better results on the global scale, with relatively lower accuracy. For a near-flat surface, a light source slant
angle of 25° may be used to attain more accurate results. For surfaces having slopes less than 40° the mean surface
normal recovery error is experimentally found to be less than 5°.
In part I of this study a laser-based system for automatic measurement of spur gears' tooth thickness and pitch was introduced. The developed system provides an inaccuracy value on the order of 5 µm, and the measurement time, for all gear teeth, was just about 1 min. In this part the experimental work is further extended to measure the tooth flank profile of spur gears. Flank profile is one of the most important factors that affect gear performance. In gear meshing, motion is transferred through contact along gear flanks. Deviations in flank profile due to errors in manufacturing or nonuniform wear result in variations in gear movement. Measurement of the flank profile can help in adjusting the gear manufacturing process, control the quality of manufactured gears, and monitor the wear of gears during action. The proposed flank profile measurement system is based on the principle of optical triangulation. The flank profile measurement setup is integrated with that of the tooth thickness and pitch, and hence tooth thickness, pitch, and profile measurements are performed simultaneously, and the measurement time for the three parameters for all gear teeth remains less than 1 min. Software is developed to graph the actual tooth profile and evaluate its deviation from nominal shape. The flank profiles measured using the developed system are in good agreement with those obtained from a well-established measurement method.
Gears of all types and sizes are widely used in machinery and equipment. Spur gears represent the largest percentage of all gears in use, and automating their measurement has become a common goal. In this paper a new computer-assisted noncontact laser-based spur-gear measurement system is developed. The technique is based on optical obscuration and is used to measure the thickness and pitch of the test gear at a predetermined tooth height. The developed system has an inaccuracy on the order of 5 µm, and the time required to measure a whole gear is 1 min. The system can measure gears with different modules and numbers of teeth. The measured dimensions were compared with those obtained with a well-established technique and are in good agreement.
Scattering techniques are mostly used to investigate rough surfaces with rms values less than lambda 'the wavelength of the illumination beam.' An investigation was made on the scattering of laser light from rough surfaces having amplitudes larger than the wavelength of the illumination beam. A numerical solution of the Beckmann's scattering model, based on the facet model approach, was applied for the assessment of surface roughness. The proposed model was used to calculate the amplitude and wavelength of a number of periodic rough surfaces. A special scattering geometry was adopted in which the illumination beam was parallel to the roughness lay and the grazing angle was small. The numerical investigation included a number of periodic rough surfaces with a wide range of roughness amplitudes. The facet model was also used to calculate the characteristics of the investigated surfaces using their digitized profile coordinates. Numerical results were compared with the results obtained experimentally from real periodically rough surfaces. The facet model approach makes it possible to study wider range of rough surfaces with profiles that do not follow a defined mathematical form. Experimental results show a very good agreement with those obtained from the numerical solution using the facet model approach.
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