Automated calibration of graduated scales

Abstract

microscope 0 Optical E D interface -0 Reference camera and -USB L u --0 encoder ISAAbstract -In the geometrical metrology field, calibration of graduated scaies is performed by comparison of the scale under inspection against a length standard at specific intervals. The procedure can take a long time due to the human intervention as a part of an observation process at each measurement interval. For example, the calibration o f a scale of l m can be divided in intervals of lcm, which results in a process with around 100 measurements. This paper describes a fully automated measurement instrument used in the calibration of graduated scales. The instrument avoids the human intervention by means of computer vision hardware and software and automated control. The measurement acquisition is done in known length intervals by the accurate positioning of an observation device and then applying computer vision techniques in order to recognize the magnitude in the scale. The measurements are compared against those reported by the length standard to complete a caIibration chart. The system described here improves the overall performance in relation to the manual method.