The purpose of this paper is to develop a non-contact 3-D digitizing system using an NC machine tool which can measure and free-form surfaces such as 3-D model shapes for injection molds speedily and accurately. The proposed 3-D digitizing sensor has a major advantage in that the location of a light spot obtained by passing laser light scattered from a target surface through a unique lens system is linearly proportional to the displacement of the surface in optical axis. This sensor, with a measuring range of 20 mm and resolution of 11 μm/pixel, can measure the displacement of a target surface within an accuracy of ±50 μm for a steep inclined surface up to ± 75 degrees without causing a dead angle called the shadow effect. The 3-D digitizing system which can measure 3-D model shapes at high measuring speed of more than 4 m/min is developed, in which the sensor is automatically moved up and down by servomechanism as the light spot to be detected exists always within the measuring range of sensor during the traversing of the NC machine tool. Moreover, the profiles of a 3-D model shape can be observed in real time.
