Automated calibration of an optomechanical derotator using 6-axes parallel kinematics and industrial image processing algorithms

A concept for an optomechanical derotator is presented. The derotator allows optical measurements of rotating objects during operation. To guarantee a stationary optical image, the optical axis of the derotator needs to be coaxially aligned to the rotational axis of the measured object. The correlation between the movement of the optical image and a miscalibration is explained by a mathematical model. The movement of the optical image is tracked with a high-speed camera. Approximating the tracked path as a Limacon of Pascal, a parameter corresponding to the magnitude of the miscalibration is identified. This parameter is minimized by modifying the position and the orientation of the derotator with a hexapod. The limitations of this procedure are analyzed and further approaches are discussed.