3D Measurement of Large Structure by Multiple Cameras and a Ring Laser

This paper presents an effective mobile three-dimensional (3D) measurement system that can obtain measurements from the inside of large structures such as railway vehicles, elevators, and escalators. In the proposed method, images are acquired by moving measurement equipment composed of a ring laser and two cameras. From the acquired images, accurate cross-sectional shapes, which are obtained via a light-section method by each camera, are integrated into a unified coordinate system using pose estimation based on bundle adjustment. We focus on the method of separately extracting the information necessary for the two processes – the light-section method and pose estimation – from the acquired images. The laser areas used for the light-section method are detected by a bandpass color filter. Further, a new block matching technique is introduced to eliminate the influence of the laser light, which causes incorrect detection of corresponding points. Through an experiment, we confirm the validity of the proposed 3D measurement method.