Line structure light calibration based on a freely placed single cylindrical object

Abstract

The traditional Zhang calibration method takes multiple checkerboard images at different positions, but in practical applications, surface measurement is usually required, in which case the planar target is not suitable. Thus, a calibration method is needed, using curved surface targets. In this paper, a line-structured light calibration method is presented based on a freely placed cylindrical object. The calibration process is as follows: the cylindrical target is placed freely and irradiated with a laser; The camera captures the target image and then the light strips of the cylindrical target and its two bus bars are extracted; The translation relation between the cylinder and the images is calculated according to the imaging principle and geometric relation; The center points of the light strip are converted to 3D coordinates according to the internal parameters of the camera for fitting the light plane. Two experiments are designed to verify the advantages of the method. The needle gauge experiment shows that 0.001 mm accuracy can be achieved in a single frame measurement, and the ring gauge experiment shows that the measurement accuracy of the system is increased by 20 %. This method is more applicable and more suitable than the traditional method for high-precision industrial 3D measurement.