High-Precision Rotation Axis Calibration of Line-Structured Light Measurement System Using a Stepped Cylinder.

Line-structured light sensors have the advantages of simple structure, low cost, and high precision. Integrating the sensor with a turntable is an important strategy to achieve complete results of complex surfaces. To enhance measurement accuracy, we proposed a rotation axis calibration method using a stepped cylinder. Coefficients of the laser plane are firstly optimized based on the principle of cross-ratio invariance to ensure the sensor's own accuracy. At each rotational angle, the laser plane intersects the cylinder, and corner points on the edges are extracted as feature points. Subsequently, an objective function is established by minimizing the average distance between rotated feature points and ideal circles and is solved using sequential quadratic programming method. After optimization, the average diameter error of the stepped cylinder is reduced by more than 90%. The relative errors of other typical features (ball diameter, cylinder diameter, groove depth) are all less than 0.15%. Measurement results of complex objects with different materials are also successfully obtained with their small features clearly observable.