Ken'ichi Nishiguchi

Pulse pre-pump method for cm-order spatial resolution of BOTDA

The distributed Brillouin scattering technique, using pulse width of 1ns, that is, one order of magnitude smaller than currently available in commercial applications of BOTDA, was successfully implemented and examined in laboratory environment by Bao et al. However, the two main problems prohibits its commercial use, namely, the measurement setting must be modified each time the measurements object is changed, and, furthermore, long-range measurements cannot be effectively carried out due to substantial increase in signal noise level with the measurement distance. This paper presents a new technique, which overcomes both of these problems, by introducing the pre-pump pulse in front of standard laser pulse. Theoretical analysis clearly demonstrates that the cm-order distributed sensing, independent of the fiber length, can be realized. Moreover, a quantitative analysis of strain measurement accuracy is also presented.

Omnidirectional vision system using two mirrors

Obtaining omnidirectional visual information for a study of mobile robots is important for understanding robot positioning. Usually, such vision systems use a fish-eye lens or a reflecting mirror (conical, spherical or hyperboloidal). A conventional system has a problem in that an unnecessary visual field occupies most of the image. The conventional one also has a problem where the camera image is blurred due to the physical property of the mirror and a clear image cannot be obtained, especially in a dark environment. In order to overcome these difficulties, we propose an omnidirectional vision system using two mirrors with a contrived curvature for obtaining a panoramic image. The vision system consists of two axisymmetric mirrors (like a reflecting telescope) and a CCD camera. Incident rays from 360 degree surroundings are reflected twice by a primary mirror and a secondary mirror, then enter the CCD camera. A theoretical consideration is made to estimate the degree of aberration for the reflecting optical system and it uses two mirrors with arbitrary curvatures. The design method is developed to minimize the aberration of the image after the reflections of the two mirrors. The vision system can realize a clear omnidirectional panoramic image with minimum blur. The optical characteristics of the design are evaluated and the results show the effectiveness of the proposed vision system.

Small target detection from image sequences using recursive max filter

This paper presents a new method for detection of small moving targets from noisy image sequences using a recursive filter, which contains a local maximum filter in the feedback loop. Since all the procedures contained in this method can be implemented by fully parallel algorithm, this method can be realized by a neural network and real-time processing is possible for image sequences at high frame rates. First we investigate the performance of the method on the assumption that the targets move randomly in an image plane and the background noise is white both in time and space. The results show that the proposed method has the ability to suppress the background noise and enhances small moving targets, and that the targets are detected only by thresholding after the processing of the recursive filter. There can be other backgrounds such as clutters and stationary objects. It is also shown that the above method is applicable after preprocessing of conventional time difference method, and is able to suppress these backgrounds. Next we analyze the performance of the method using the property of order statistics. The performance measure is the output signal-to-noise ratio and is represented analytically as a function of input SNR and the parameters included in the method. Finally, the recursive filter is optimized using the result of the analysis.

Optimization of Coverage Pattern for Regional Communications Satellite

An optimization problem of an antenna coverage pattern for a regional communications satellite when an antenna-pointing error exists is discussed. A new performance measure is introduced to evaluate the coverage pattern. This measure is defined as the statistical mean of the ratio between two areas, the full service area and the part of it covered by the antenna. The optimum coverage pattern which maximizes this measure under certain constraint is obtained. The results of numerical calculations are included to demonstrate the technique.

Determining the Position of a Mobile Robot Using an Omnidirectional Vision System

Abstract This paper presents a self-positioning system for a mobile robot. The proposed positioning system consists of an ODV (OmniDirectional Vision system) featuring two mirrors with a contrived curvature for obtaining a panoramic image with low aberration. The relative self-position can be estimated from three directional angles toward landmarks by the image processing of a panoramic image. An outdoor experiment which used a mobile robot shows that the proposed positioning system have high positioning accuracy even in the cluttered outdoor environment.