Masahiro Shikai

Accuracy of 2-Dimensional Object Location Estimation Using Leaky Coaxial Cables

The improvement of position estimation accuracy is a very important factor in various radar applications. This paper focuses on two-dimensional (2-D) location estimation in radar surveillance using leaky coaxial cables. A leaky coaxial cable is a kind of antenna and has recently attracted attention as a powerful tool for vehicle detection and as an intrusion detection sensor for perimeter security. We derive the Cramér-Rao bound (CRB) for a leaky coaxial cable sensing application and introduce the CRB ellipsoid to evaluate the accuracy of the 2-D location estimation of an object. The diameter and angle of a CRB ellipsoid indicates its error distribution. A leaky coaxial cable has an outer conductor with periodic slots. Its slot pattern determines the radiation characteristics such as the beam angle and harmonic radiation. We focus on the slot pattern to improve the estimation accuracy. Numerical analyses show that a slot pattern generating multi-beams improves the accuracy while single radiation is preferred for general use in communication applications.

Fingerprint Authentication Using Optical Characteristics in a Finger

Fingerprint is widely used in various personal authentication applications. It is because that fingerprints can achieve the best balance among authentication performance, cost, size of device, and ease of use. However, most of current fingerprint sensors have some problems to be solved. Those are that captured fingerprint images are easily affected by the condition of the finger surface and the manner of finger pressing due to the sensing principle, and it can degrade authentication performance. To solve these problems, we have developed a new fingerprint sensor that has a novel sensing principle. This sensor forms a fingerprint image based on optical characteristics of a fingers interior by scattered transmission light. Therefore, the images so obtained are not easily affected by the condition of the finger surface such as wet, wrinkled, and so on, and enable stable authentication. In this paper, we describe the operating principle of the new fingerprint sensor using optical characteristics in a finger, and show the effectiveness of the sensor by illustrating obtained fingerprint images

All optical encoder using optical delay

A novel concept for an all optical absolute position encoder whose sensing unit uses only passive elements is presented. Optical delay fiber loops are used to multiplex sensing channels. The device can be interrogated from a distant location using a single optical fiber which can be several kilometers long. Absolute position encoding is achieved by analog modulation of light intensity with well studied multiple slit patterns.

Optical passenger sensor by reflective light detection for automatic escalator

We have developed a new optical passenger sensor for automatic escalators that detects the presence and approximate position of a passenger by using reflective light detection. This sensor consists of a pair of modules that are attached to the end of the skirt guards and makes conventional posts unnecessary. The speed of the escalator with the sensor is controlled at three levels depending on the position of a passenger.