The Impact of Control Point Dispersion on Measurement Accuracy in a New Type of Light-pen Coordinate Measuring System

Light-pen coordinate measuring machines are widely used due to their portability; however, the measurement accuracy is affected by camera calibration, light-pen probe calibration, control points, etc. To study the influence of control point dispersion on measurement accuracy, a light-pen coordinate measuring system is constructed in this paper. In this system, a new type of control point distribution is designed. Based on this distribution, five light-pens with different control point dispersions are created and an algorithm is proposed to match control points with their images. The experimental repeatability results for the five light-pen probes indicate satisfactory repeatability, which ensures the effectiveness of the measurement results. The experimental measurement results for five light-pens demonstrate that the measurement error decreases with the decline of the control point dispersion at first, but begins to increase when the control point dispersion reaches a certain value.