3D depth sensing of active structured light field based on EPI

In this paper, a three-dimensional (3D) depth sensing system based on active structured light field imaging (ALF) is proposed. In light field imaging, one of most commonly used method for depth estimation is based on its Epipolar Plane Image (EPI), in which the slope of line features is related to parallax and is inversely proportional to the depth of the measured object. However, it is difficult to extract the line features accurately only according to the captured texture information of the object, especially in the case of weak texture, repeated texture and noise. Therefore, active phase feature provided by a phase-shifting fringe projection is introduced for this system, with which the line features in EPI can be extracted by simply searching correspondence points with the same phase value. In order to obtain depth map with measuring accuracy, a metric calibration method is proposed to establish the quantitative relationship between the slope of lines and depth. Besides that, due to the existence of distortions in the light field camera (LFC), the correspondence points in EPI cannot fit well enough with linear distribution, another calibration based on the LFC imaging model and Bundle Adjustment (BA) was implemented to correct distortions in the EPI, which can reduce the fitting errors of line features. experiment results proved that calibration method described above is effective, and the built ALF system sensor can work well for 3D depth estimation.