Michiko Nishiyama

Wearable Sensing Glove With Embedded Hetero-Core Fiber-Optic Nerves for Unconstrained Hand Motion Capture

In this paper, we present a wearable sensing glove with embedded hetero-core fiber-optic nerve sensors that detect finger flexion to achieve unconstrained hand motion monitoring. The hetero-core fiber sensor is suited to the wearable sensing glove because it is capable of optical intensity-based measurements with excellent stability and repeatability using single-mode transmission fibers and is unaffected by temperature fluctuations. The hetero-core sensor elements are located on the back of the hand so that they are not affected by random wrinkles in the glove at the joints. As a result, the hetero-core flexion sensor after calibration is capable of detecting the joint angles of the fingers regardless of differences in hand size, and the hetero-core sensing technique enables the sensing glove to be constructed with a minimum number of sensor points. The optical loss performance of the hetero-core sensors reveals monotonic characteristics with respect to the flexion angle of joints. The optical loss is 1.35 dB for a flexion angle of approximately 97.2deg with accuracy of 0.89deg in the detected flexion angle. Real-time hand motion capture was demonstrated by means of the proposed sensing glove without restricting natural human behavior.

A Motion Monitor Using Hetero-Core Optical Fiber Sensors Sewed in Sportswear to Trace Trunk Motion

In this paper, a cameraless motion monitor has been described by introducing very thin sensor modules into sportswear, in which a single-mode hetero-core optical fiber sensor is fabricated. An elbow joint motion and a trunk motion are monitored by a sportswear on which the hetero-core optical fiber sensor modules are sewed so as to be sensitive to stretch on the wear. In order to get rid of the restriction to the human body, a two-plane model has been proposed in which only two sets of sensors simplify three kinds of motions at the trunk, which are anteflexion, lateral bending, and rotation. Additionally, the real-time monitoring system has been tested when golf swing motion is performed. As a result, it has been indicated that the motion, which consists of a composite of three motions, can be significantly analyzed by means of the two sensors. The developed system is viable to an unconstrained motion capture system intended for a teaching device in sports and rehabilitation fields.

A hydrogen curing effect on surface plasmon resonance fiber optic hydrogen sensors using an annealed Au/Ta 2 O 5 /Pd multi-layers film

In this paper, a response time of the surface plasmon resonance fiber optic hydrogen sensor has successfully improved with keeping sensor sensitivity high by means of hydrogen curing (immersing) process of annealed Au/Ta2O5/ Pd multi-layers film. The hydrogen curing effect on the response time and sensitivity has been experimentally revealed by changing the annealing temperatures of 400, 600, 800°C and through observing the optical loss change in the H2 curing process. When the 25-nm Au/60-nm Ta2O5/10-nm Pd multi-layers film annealed at 600°C is cured with 4% H2/N2 mixture, it is found that a lot of nano-sized cracks were produced on the Pd surface. After H2 curing process, the response time is improved to be 8 s, which is two times faster than previous reported one in the case of the 25-nm Au/60-nm Ta2O5/3-nm Pd multi-layers film with keeping the sensor sensitivity of 0.27 dB for 4% hydrogen adding. Discussions most likely responsible for this effect are given by introducing the α-β transition Pd structure in the H2 curing process.

Smart Pressure Sensing Mats with Embedded Hetero-Core Fiber Optic Nerve Sensors

In this article, we propose a smart mat application in the form of a thin mat placed on the floor designed for monitoring human motion, and specifically of a sole pressure mapping mat that uses hetero-core fiber optic nerve sensors. In addition to several advantages conferred by the use of optical fibers, namely, light weight, minimal use of material, and resistance to corrosion and electromagnetic interference, the novel hetero-core optic fiber nerve sensor is sensitive to the bending action of the hetero-core portion, and its fiber transmission line is unaffected by external disturbances such as pressure and temperature fluctuations owing to its single-mode stable propagation scheme. Therefore, the hetero-core fiber optic nerve sensor shows potential application for the distributed pressure sensing of natural human activities and for installation at various sites. Here, we successfully demonstrate the use of a distributed pressure sensing mat using hetero-core nerve sensors in detecting human activities in a bathroom by monitoring the motions of walking and falling and by sole pressure mapping.

Restraint-free wearable sensing clothes using a hetero-core optic fiber for measurements of arm motion and walking action

In recent years, unrestrained monitoring human posture and action is a field of increasing interest in the welfare of the elderly and the sport-biomechanics. The scope is this study is that we develop a wearable sensing clothes, which can detect entire body posture and motion using a hetero-core optic fiber sensor. This newly developed sensor can offers several advantages such as the simplicity of structure and fabrication, the stable single mode based operation, the temperature independent property, and the precise loss controllability on given macro bending. These properties are suitable for implementing unrestrained wearable clothes. In this paper, for monitoring flexion of joint without the disturbance of the rucks in the clothes, we proposed and fabricated the improved module structured in the joint ranging 0-90 degree. Additionally, in order to reduce the number of transmission line to be added due to monitoring the whole body posture and motion, we tested that two hetero-core sensors which are tandem placed in a single transmission line have been discriminated by the temporal differential of the optical loss. As a result, we have successfully demonstrated that the wearable sensing clothes could monitor arm motion and human walking without restraint to human daily behavior.

Optical Intensity-Based Measurement of Multipoint Hetero-Core Fiber Sensors by the Method of Time-Differentiation in Optical Loss

In this paper, we propose the multipoint optical intensity-based measurement of tandem connected intrinsic fiber-optic sensors by means of monitoring time-differentiation in optical loss. The use of hetero-core sensors can make it possible that a simple optical intensity-based measurement combined with a time-differentiation method could be facilitated for the multipoint measurement because the hetero-core technique has a low insertion loss and a sizable loss change in the tandem usage. Addressing multi-sensors has been successfully demonstrated including one displacement sensor and two contact sensors, which are located along a single transmission line in real-time basis. The gait system is also efficiently improved to monitor the knee flexure and the sole contact sensors located in a single transmission line with a mirror at the terminal end of fiber in order to simplify the measurement system for unconstrained monitoring.

A Study on Sensor Multiplicity in Optical Fiber Sensor Networks

We have developed a novel optical fiber sensor network system with hetero-core spliced fiber optic sensors. Our previous work demonstrated that the system can play a dual role as a gigabit-class communication network and a sensing system when a limited number of sensors are used. However, optical devices are generally expensive. Thus, in order to use the devices efficiently, it is required that the system allow more sensors to be inserted into a fiber line. In this paper, we propose an enhanced system that can improve sensor multiplicity. The system utilizes a new type of sensor module that generates optical loss only for a short time. We analyze the relationship between sensor multiplicity and communication quality when using such sensor modules, and present results of the performance of this enhanced system in simulated experiments.

Rotational positioning measurement for the absolute angle based on a hetero-core fiber optics sensor

We proposed a new approach to measure the rotational angle and describe how the rotational positioning sensor could be devised arranging the hetero-core fiber-optic macro-bending sensors in terms of detecting the absolute rotational angle. The hetero-core fiber optic sensor has many advantages such as ability of macro-bend sensing with optical intensity-based measurement, single-mode transmission basis and independence of temperature fluctuation for external environment. Therefore, it is suitable that the rotational positioning sensor is fabricated with the hetero-core fiber-optic technique. We designed two types of the absolute rotational position sensor modules to convert the absolute rotational angle to the displacement. The result showed that the proposed rotational positioning modules were sufficiently sensitive to the given rotational angle with monotonic loss change characteristics. The hetero-core rotational positioning sensors were successfully perceptive with typical sensitivities approximately 0.77 and 0.71 dB in the rotational angle ranges of 60 - 360 and 60 - 180 degrees. The deviation of the module in the range of 60 - 180 degrees induced 1.74 % that corresponded to 2.13 degrees.

Multipoint Hydrogen Sensing of Hetero-Core Fiber SPR Tip Sensors With Pseudorandom Noise Code Correlation Reflectometry

In this paper, we describe multipoint hydrogen sensing in real time using surface plasmon resonance (SPR) fiber optic hydrogen tip sensors with Au/Ta2O5/Pd multilayers film combined with a time-domain interrogating system based on pseudorandom noise code correlation reflectometry. This method uses the correlation between a launched pseudorandom noise code signal and its reflection enabling simultaneous measurement at many points along the optical fiber in real time with a high signal-to-noise ratio. In a light intensity-based experiment with an 850-nm LED, the tested three hetero-core optical fiber hydrogen tip sensors proved to be reproducible responses with and without hydrogen absorption, with showing the similar time response and sensitivity compared with those of our previously reported sensor. Multipoint hydrogen detection was demonstrated using four SPR hydrogen tip sensors. Our experimental results showed that four sensors using the 25 nm Au/60 nm Ta2O5/5 nm Pd multilayer film exhibited a response time of ~25 s for a 4% hydrogen concentration. In addition, it was found that all sensors can detect the hydrogen concentration with sufficient sensitivities in real time.

Specific vibration frequency detection based on hetero-core fiber optic sensing scheme for security environment monitoring

Fiber optic sensors have a potential to make ideal vibration sensors for smart structures because they can be operated without supplying the power at the sensor itself, have the capability of resistance to corrosion and fatigue, immunity to electrical interference, usage for a long time and safe. Additionally, the fiber optic sensors are practically able to operate the remote sensing due to stable transmission fiber line. Especially, hetero-core optical fiber sensors for environmental monitoring system have several advantages such as high accuracy, repeatability and temperature independency. This paper reports a novel approach to dynamic measurements for vibrations of the window using two types of the hetero-core optical fiber vibration sensors. A first vibration sensor can detect a vibration with high sensitivity due to effectively convert the vibration into change in the curvature of the fiber sensor. A second type of vibration sensor, which is lower sensitivity than the first type sensor, can detect vibrations with a few millimeters in thickness. It is shown that the vibration frequency depends on a fiber length of the two fixed points. A characteristic of spectrum peak shows the relatively wide frequency bands with ranging from 400 to 5000 Hz and from 1000 to 4500 Hz as the fixed points distances in the ranges of 15–45 mm and 10–25 mm for the first and second types of sensors, respectively.