HIGH PRECISION RING LOCATION FOR A NEW ROTATIONALLY SYMMETRIC TRIANGULATION SENSOR

Abstract

For a growing range of optical measurement task, like gap measurement in automotive industry, traditional triangulation sensors have several disadvantages due to the fact that the measurement result is dependent on the orientation of the sensor because of the non-rotational symmetry of the optics. Consequently a design method was proposed recently for a new class of rotationally symmetric triangulation sensors. Such designs can be realized with aspheric reflection optics and area detectors, such as CCD or CMOS. The optics of the sensor can be extended by an imaging optics which allows at the same time image capturing and distance measurement. In this paper we show the first prototype. This system is based on an optical system of one part manufactured by commercially available diamond turning. The layout of the optical system for distance measurement consists of two reflecting aspheric surfaces. The high precision algorithm for ring location was needed because the performance of the sensor is based on the detection of ring, especially the radius of the ring. In this paper, we try to give the different evaluation function for high precision location of ring. Then we used various methods to solve it and got optimized result. The comparison of algorithms for simulation was listed in the paper. And the measurement result for the real image got by the prototype was also presented. It seems the algorithm meets the precision demand of the sensor.