The Research On Large Depth-of-field Portable Three-dimensional Laser Scanner And Its Applications In Robot Vision

Laser-scanning technology based on the triangulation method has many advantages such as non-contact operation, fast acquisition speed, simple optical arrangement, low cost and good stability, etc., now it has been widely applied in the measurement of surfaces and molds, as well as in prosthesis design, rapid prototyping, and reverse engineering, etc. In recent years, with the development and progress in optical and microelectronic technologies, compact and portable 3D acquisition systems are integrated for acquiring the 3-D information of the object's surface from multiple angles and directions, and have been used for the space applications and robot vision. However, when it is applied to the measurement of object with large size and complicated profile, the limitation of small depth-of-field of conventional 3D acquisition system will usually lead to the low measurement precision. One has to edit multiple scanning paths and overlap corresponding scanning data to improve the measurement precision, but this process is time-consuming and inefficient.In this paper, in order to extend the depth -of field of 3D scanner, we tilt the Charge Coupled Device (CCD) plane according to the Scheimpflug condition, then construct the imaging model of the camera and theoretically derive the object-image equations of tilted camera system. We extend the depth -of field of 3D scanner from 30mm to 100mm by camera calibration experiments. Meanwhile, a segmental calibration method is proposed to effectively improve the measurement precision of the scanning system. Finally, a large depth-of-field portable three-dimensional laser scanner with measurement precision of 0.06 mm is developed successfully.In order to apply the large depth-of-field portable three-dimensional laser scanner to robot vision, a new eye-in-hand calibration method using a criterion ball with a known radius is proposed. Using this method, we successfully accomplished the object's 3D reconstruction experiment. It showed that 3D scanning results with high precision and good stability can be readily obtained using robot and the large depth-of-field portable three-dimensional laser scanner developed by ourselves, the maximum error is less than 0.2mm.