Feedback projection for 3D measurements under complex lighting conditions

Active stereo vision based on the use of a projector and a camera is one of the major 3D measurement methods. Active stereo vision is a technique that is widely used because its ability to measure 3D shapes is robust to changes in ambient light in the environment. The technique involves the projection of patterns known as structured light from a projector, after which the resulting images are captured by a camera. However, active stereo vision is unable to perform effective measurements in scenes that include specular reflections or subsurface scattering. Although various methods have been proposed to solve this problem, no pattern capable of adapting to measuring varying optical properties has been proposed to date. Thus, an approach that enables projection patterns to be designed is not readily available. This led us to propose a new concept named “Feedback Projection for 3D Measurement” for adaptive measurement in a variety of scenes. In this concept, projection patterns are generated dynamically by adapting to the lighting scene to achieve high-speed and high-accuracy 3D measurements of scenes characterized by complex light reflectance. In the research presented in this paper, we resolve the 3D measurement problem as a problem of estimating the Light Transport (LT) matrix. Our proposed method consists of estimating the LT matrix and generating the projection pattern by using feedback projection. A numerical simulation is used to verify the concept of the proposed method.