Depth Resolution Enhancement in Time-of-Flight Cameras Using Polarization State of the Reflected Light

Abstract

Time-of-Flight (ToF) cameras are nowadays commonly used for depth measurements and are useful in applications, such as robotic navigation, gaming, and others. The depth measurements by the ToF camera are influenced by the systematic errors of the camera and the nonsystematic errors of the environment. This paper presents a novel method for reduction of depth measurement error using polarization state of the reflected light. Using polarization state of the reflected light, the nonsystematic errors introduced due to multipath interference, material properties, and color of the target object reduces, which reduces the depth errors. The idea is tested using SR-4000 3-D sensor and a linear polarizer in front of it. The transmission angle of the linear polarizer is varied for a fixed object distance from the camera. The depth error has a sinusoidal variation with clear maxima and minima. It is observed that the depth error is minimum when the polarization angle is equal to the ToF phase shift. The experimental results show a maximum of 87% reduction in depth error at 3000 mm distance using polarization angle equal to ToF phase shift. The reduction in the nonsystematic error in the ToF-based distance measurements using polarization of the reflected light will enable new applications, such as diffuser imaging, detection of transparent objects, and among others.