A new real-time shape acquisition with a laser scanner: first test results Vincenzo Niola n , Cesare Rossi 1 , Sergio Savino Department of Mechanical Engineering for Energetics (Di.M.E.), University of Naples ‘‘Federico II’’ Naples, via Claudio 21 80125, Italy article info Article history: Received 25 November 2009 Received in revised form 20 May 2010 Accepted 30 June 2010 Keywords: Shape acquisition Laser scanner Robotic application abstract The first results of a new method for real-time shape acquisition with a laser scanner are presented. The new method is essentially based on the use of a laser beam and a web-cam. A digital filter parameters identification was studied for the laser line detection in the image. After this, a model for the reconstruction in real-time of the laser line in the space was developed. The first test rig was just conceived to validate the method; hence, no high resolution cameras were adopted. Nevertheless, the tests have showed encouraging results. Tests were made on both plane and non-plane surfaces. First of all, it was confirmed that it is possible to calibrate the intrinsic parameters of the video system, the position of the image plane and the laser plane in a given frame, all in the same time. Moreover the surface shapes were recognized and recorded with an appreciable accuracy. The tests also showed that the proposed method can be used for robotic applications, such as robotic kinematic calibration and 3D surfaces recognition and recording. For this last purpose, the test rig is fitted on a robot arm that permits to the scanner device to ‘observe’ the 3D object from different and known positions. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction Laser scanning range sensors are widely used for high- precision, high-density three-dimensional (3D) reconstruction and inspection of the surface of physical objects [1]. The process typically consists of the following steps: planning a set of views; physically altering the relative object-sensor pose; taking scans; registering the acquired geometric data in a common coordinate frame of reference, and finally integrating range images into a non-redundant model [2]. Efficiency could be increased by automating or semi-automating this process. The first aim of the research was to study a procedure to elaborate image of laser, in order to obtain 3-D object reconstruc- tion; this, after an opportune system calibration. The technique was automated by developing an interactive GUI to acquire and to elaborate data. Reverse engineering is concerned with the problem of creating computer aided design (CAD) models of real objects by interpret- ing point data measured from their surfaces [2,3]. For complex objects, it is important that the measuring device is free to move along arbitrary paths and that it can make its measurements from suitable directions. This paper shows how a standard industrial robot with a laser profile scanner can be suitably used for those purposes. The system is planned to be a part of a future automatic system for the Reverse Engineering of unknown objects. The system was designed around a test rig that was developed at the Di.M.E. by means of a commercial linear laser and a common web- cam; this system is moved by a revolute robotic arm. The developed device permits to digitalize surfaces and to reproduce them, by means of machining. Such a device, hence, will permit a flexible and repeatable acquisition of forms; this is because the acquisition equipments will have an accurately controlled motion given by a robot. In fact, unlike static acquisition equipments, this equipment can move the camera system around the object to be analyzed without introducing problems of matching data. However, in this application, the vision system becomes an integrated device with the role of position transducer and recognition of shape and volume. In this way, it is possible to increase the robot performance, if the vision system is inserted into the robot control loop. 2. Experimental platform 2.1. Laser scanner module Our rig is based on a laser profile that essentially consists in a line laser and a camera. The laser beam defines a ‘‘laser plane’’ and the part of the laser plane that lies in the image view of the camera is denoted as the ‘‘scanning window,’’ Fig. 1. After an Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rcim Robotics and Computer-Integrated Manufacturing 0736-5845/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.rcim.2010.06.026 n Corresponding author. Tel.: + 39 081 7683482; fax: + 39 081 2394165. E-mail addresses: vincenzo.niola@unina.it (V. Niola), cesare.rossi@unina.it (C. Rossi). 1 Tel.: + 39 081 7683269; fax: + 39 081 2394165. Robotics and Computer-Integrated Manufacturing 26 (2010) 543–550