• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.65-71
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• 2003

To maximize the storage density in a localized hologram recording method, each hologram should be recorded as close as possible to its neighboring holograms. In this case, the reference beams used to record two adjacent holograms may overlap in spatial multiplexing. Through simulations and experiments, we show that there exists an optimal reference beam size to minimize the overlap for a given shifting distance of the reference beams in spatial multiplexing. Thus the advantages of the localized hologram recording method can be minimally sacrificed while the storage density is increased.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.2
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• pp.79-87
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• 2011

This paper presents the optimal design of an overlapped ultrasonic sensor ring for high resolution obstacle detection of an autonomous mobile robot. It is assumed that a set of low directivity ultrasonic sensors of the same type are arranged along a circle of nonzero radius at a regular spacing with their beams overlapped. First, taking into account the dead angle region, the entire range of obstacle detection is determined with reference to the center of an overlapped ultrasonic sensor ring. Second, the optimal design index of an overlapped ultrasonic sensor ring is defined as the area closeness of three sensing subzones resulting from beam overlap. Third, the lower and upper bounds on the number of ultrasonic sensors are derived, which can guarantee minimal beam overlap and also avoid excessive beam overlap among adjacent ultrasonic sensors. Fourth, employing a commercial low directivity ultrasonic sensor, an optimal design example of an overlapped ultrasonic sensor ring is given along with the ultrasonic sensor ring prototype mounted on top of a mobile robot. Finally, some experimental results using our prototype ultrasonic sensor ring are given to demonstrate the validity and performance of an optimally overlapped ultrasonic sensor ring for high resolution obstacle detection.