In this paper, we propose a new lightweight and cost-effective 3D omnidirectional depth sensor based on laser triangulation in order to ensure a wide field of view (FOV) while achieving portability and affordability. The proposed sensor is tiny palm-sized and hence easily installed even on small moving objects, which is largely composed of a structured light-based 2D sensor and a rotating motor for creating a full 360 degree horizontal FOV, thus providing a 3D omnidirectional sensing capability. The structured lightbased 2D sensor is specially designed to maximize the vertical FOV by employing a fisheye camera and a laser beam passing through two cylindrical lenses for projecting a line onto a surface. From the rotational movement of the 2D sensor due to the mounted motor, its surroundings are scanned by extracting the corresponding 3D omnidirectional depth information from laser triangulation. The actual implementation is carried out to examine the technical feasibility of realizing the proposed 3D omnidirectioanl depth sensor. It turns out that the proposed depth sensor covers over 97 % area of its surrounding sphere. It is also observed through experiments that the proposed 3D omnidirectional depth sensor has similar accuracy to that of a Velodyne HDL-32, 32-channel light detection and ranging (LIDAR) sensor, at a range of 5 m to 6 m while providing much wider vertical FOV and higher vertical resolution. INDEX TERMS Omnidirectional depth sensor, structured light, field of view (FOV).
The objective of this study was to develop an edutainment robot which provides multi-sensory learning experiences to improve users' space perception and creativity. In particular, we focused on developing educational content for the study of the Korean alphabet (Hangul) using the robot. On the basis of the phonemic and modular nature of Hangul, we devised a block-shaped edutainment robot for the study of Hangul. The robot known as "HangulBot" is composed of a consonant block and a vowel block. By rotating and rearranging those blocks, a user can create different characters. To enable the robot to perceive the arrangement of the blocks and the distance between a consonant block and a vowel block, IR LEDs and photo transistors were used. The eight IR LEDs in the consonant block generate different radiation signals, and the vowel block perceives the arrangement of the blocks by receiving the signals. The distance between the two blocks is estimated by measuring the thresholding, and the corresponding sound of each arrangement is then played through a speaker installed in the vowel block. We executed two shortterm field trials with a twenty-seven month old child in June of 2011 and November of 2011 to ascertain children's initial reaction to HangulBot and how their reaction would change over time. While the results are preliminary, we noted several interesting findings. First, after several trials by the mother, the child felt comfortable with HangulBot. Second, the child intuitively followed the corresponding speech sounds which were generated by HangulBot according to the arrangement of the blocks. That is to say, the sound generated after the arranging the block intuitively induced the child to follow the sound. Third, the child's initial reaction to HangulBot was mostly block play, but after five months later, her reaction to the robot included not only block play but also active learning of the Korean alphabet. This result indicates that HangulBot could be an effective edutainment tool which improves space perception and creativity as well as linguistic abilities by stimulating both sides of the brain.
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