2-DIRECTIONAL SCANNING METHOD FOR REDUCING THE SHADOW EFFECTS IN LASER TRIANGULATION

A two-directional scanning method has been developed to reduce the sha dow effects in laser triangulation probes. This method, which we call 2DS, uses an acousto-optic deflector (AOD) as a scanner to allow a dif fracted beam to scan an object from two directions, and a position sen sor to detect the shift of a spot projected from these two directions alternately by a time-sharing technique. The shadow effects are thereb y reduced by this two-direction projection. First we determined the ac curacy of the 2DS method by measuring the displacement of a plastic pl ate along the x- and y-axes and then comparing the results with those obtained using a linear gauge. Then we confirmed the capability of the method by using it to measure the cross sectional shape of a half-bal l button, and then comparing the results with those obtained using a c onventional one-directional scanning laser triangulation method. A rel ative uncertainty of 0.8% was obtained.