Introduction to AI Robotics, Second Edition by Murphy Robin R.;

Author:Murphy, Robin R.;
Language: eng
Format: epub
Tags: Algorithm; Artificial Intelligence; AI; robotics; robots; computer science; sensing; navigation; uncertainty; hierarchical robotics; reactive robotics; hybrid deliberation/reactive robotics; multiagent; path-planning; mobile robots; computer vision; range sensing
Publisher: MIT Press

11.4.3  RGB-D Cameras

RGB-D CAMERA

RGB-D cameras are a combination of a IR light striping system (except instead of stripes of light, random dots are projected) with a regular RGB visible light camera. These are sometimes called RGB+D or just RGBD cameras. RGB-D cameras project IR light read by a camera tuned for the IR frequency of light. The IR dots are invisible to the human eye. Thus a separate RGB camera can be mounted next to the IR camera to perceive the same scene without dots and make it visible to the human eye. The low-cost Microsoft Kinect and ASUS Xtion cameras use essentially the same technology for videogames and were immediately adopted for use by roboticists.

However, as noted in Suarez and Murphy,201 the RGB-D cameras are not sufficient for general robotics for three reasons. First, RGB-D cameras are typically optimized for the videogame market, where the camera is stationary, indoors, and the gamer adjusts the lighting in the room and turns the camera system until it produces consistent results. In mobile robots, the robot may move through regions that have much different lighting conditions than does an indoor recreational room. Bright light and direct sunlight wash out the IR projection. Second, the IR light is an active sensor. Thus objects with reflective surfaces or sharp edges and angular surfaces that create specular reflection cause the IR image to be noisy. Third, RGB-D cameras are tuned for projection and receptivity over specific ranges. In the case of a Kinect, that range is 1.2 m to 3.5 m. If a robot needs to perceive depth closer than 1.2 m or farther than 3.5 m, the Kinect will not be of use.

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