Multi-sensor system for surface inspection and 3D-geometry assessment

This paper addresses an installed application in quality control where a 100 % inspection of geometry (3D) and surface of cuboid (parallelepiped) and ring-shaped magnets is done using a system of 2 CCD matrix cameras, one of which is equipped with on-board processing components and a transmitted-light sensor with microcontroller based data processing for the measurement of the height of the objects. The geometry and surface properties are measured with a diffuse indirect IR-LED flash, mounted in a ring around the object and a telecentric lens to avoid perspective distortions due to different heights of the measured objects. The surface inspection looks for broken pieces, surface faults due to spalling/chipping and for cracks. The second CCD camera uses the same illumination and algorithm to inspect the surface of the other side of the objects after it has been turned around in a return conveyor belt. All components are triggered by separate light barriers and perform their tasks independently. The integration of the results of each measurement is done by an SPC which also controls the actors that handle the three different classes of objects (good, bad, rework). These actors are valves and the objects are separated by pressurized air. The main concern of this paper is the system aspect, Row the measurements results are evaluated and combined to achieve a correct classification of the objects which are inspected by three independent sensors and arrive at unpredictable time intervals.