Yuzuru Kubota

Sensitivity property of a hetero-core-spliced fiber optic displacement sensor

A displacement sensor has been newly developed using a hetero-core spliced fiber optic element in a form of simple module structure and evaluated in terms of the accuracy, reproducibility, and sensitivity as an OTDR-based, tandem connected displacement detector, for the purpose of the full-scale environmental monitoring. The developed sensor module is designed to be sensitive to a relatively large displacement in the range 0-5 mm, for which a simple displacement-macrobending conversion mechanism in the module produces the change in the sensor transmission loss ranging from 0 to a few dB. The initial insertion loss only due to a hetero-core portion was 0.3 dB. The sensitivity showed a tendency proportional to the insertion length of hetero-core portion in the range from 1 to 2 mm. In contrast to conventional fiber distortion sensors such as FBG (fiber bragg grating) and BOTDR (Brillouin optical time domain reflectometer), the hetero-core technique introduced in this work shows no temperature dependence in its sensor principle since the use of hetero-core makes it possible that change in backward Rayleigh scattering can be successfully amplified with a relatively large curvature. The experiment promisingly showed sufficient reproducibility the sensing operation with the accuracy less than 0.1 % to the full span displacement of 5 mm.

Position measurement of container crane spreader using an image sensor system for anti-sway controllers

Speedy operation efficiency is constantly required of the container crane operators who work for cargo handling in the port. They are experts in suppressing the sway motion which is generated in the process of the handling. This undesirable motion may deteriorate the operation efficiency due to strained nerves of the operator. Therefore, an anti-sway controller has been required on practical job-site. To accomplish an adequate anti-sway control, sensors are also required to be able to measure the position of a crane spreader moving on. In this paper, we propose a position measurement system with an image sensor. The image sensor detects two devised landmarks attached to the upside surface of a spreader to measure the displacement and height to one. The image processing technique used for the sensor is a kind of robust template matching method, named vector code correlation (VCC), devised to consider the conditions of real environments. We employ the simple mechanism, so that the system can be easily applicable to existing container cranes. The details and performance of the measurement system are introduced together with the experimental results performed with the pilot system. We will also show that the system has the sufficient efficiency and accuracy for the use on practical job-site.

Measurement system design for sway motion based on image sensor

Speedy operation efficiency is constantly required of the container crane operators who work for cargo handling in the port. They are experts in suppressing the sway motion which is generated in the process of the handling. This undesirable motion may deteriorate the operation efficiency due to strained nerves of the operator. Therefore, an anti-sway controller has been required on practical job-site. To accomplish an adequate anti-sway control, sensors are also required to be able to measure the position of a crane spreader moving on. In this paper, we propose a position measurement system with an image sensor. The image sensor detects two devised landmarks attached to the upside surface of a spreader to measure the displacement and height to one. The image processing technique used for the sensor is a kind of robust template matching method, named Vector Code Correlation (VCC), devised to consider the conditions of real environments. We employ the simple mechanism, so that the system can be easily applicable to existing container cranes. The details and performance of the measurement system are introduced together with the experimental results performed with the pilot system. We will also show that the system has the sufficient efficiency and accuracy for the use on practical job-site.

Measurement accuracy on indoor positioning system using spread spectrum ultrasonic waves

This paper describes significant factors on spatial error distribution measured in a given indoor space with a local positioning system which utilizes spread spectrum ultrasonic waves generated by narrow directional ultrasonic transmitters. The positioning error has interestingly been discussed from the viewpoints of the dilution of precision (DOP) and the ranging error due to the transmitter directional characteristic, mainly. The indoor 3-D position is calculated by means of an algorithm using distances from the transmitters located at the four corners of the ceiling to a mobile receiver. From the result of these experiments, it has been usefully found that the positioning error can be more largely influenced on the DOP of vertical direction than it of horizontal direction and that its average is of 3.43[cm] rms for all 3-D measurable points. These findings obtained from the work imply that the 3-D indoor positioning can be realized with an acceptable centimeter-order of precision. Moreover, they suggest that it has to be considered from the viewpoints of not only the ranging error, which could be yielded by the distance measurement, but also the DOP, which is inevitably obtained by a geometrical arrangement relative to the transmitters and receiver.

Accuracy evaluation of a hetero-core splice fiber optic sensor

A Hetero-Core Splice Fiber Optic Sensor has a very simple structure in which a short-length, different core-size fiber is inserted in a single-mode-fiber network line with a low transmission loss for the wavelength of 1.31μm. In this study, a displacement sensor has been newly developed using a hetero-core spliced fiber optic element in a form of simple module structure and has been evaluated in terms of the accuracy as an OTDR(Optical Time Domain Reflectometer)-based measurement, for the purpose of the full-scale environmental monitoring. The developed sensor module is designed to have a coverage sensitive to a relatively large displacement in the range 0-5mm, for which a simple displacement-macrobending conversion mechanism has been adopted. A nickel alloy Invar with an extremely low linear expansion coefficient is used for the main parts of the module. Displacement is given to the module with a highly accurate micrometer of a minimum resolution of 0.5μm. The sensitivity showed a tendency proportional to the insertion length of hetero-core portion in the range from 1 to 2mm. The experiment promisingly showed sufficient reproducibility in the sensing operation with the accuracy less than 0.1% to the full span displacement of 5mm. Additionally, a pressure gauge using a hetero-core spliced fiber optic element has been newly developed in a form of module structure by applying the developed displacement sensor. The pressure gauge is designed to measure the change in length of a bellows due to pressurized air. The experiment achieved the measurement accuracy 0.3%[%FS] with highly showing the capability of all-light wave-based liquid level monitoring as a first demonstration based on a single mode fiber transmission concept, which could be very useful for environmental preservation.

Container crane system using an anti-sway controller with an image sensor

Speedy operation efficiency is constantly required of the container crane operators who work for cargo handling in the port. They are experts in suppressing the sway motion which is generated in the process of the handling. This undesirable motion may deteriorate the operation efficiency due to strained nerves of the operator. To overcome this problem, we propose an anti-sway controller with an image sensor for a container crane. The image sensor measures the displacement of the spreader. Especially, the measured displacement is in real time fed back to the controller. The image processing technique here is a kind of robust template matching method, named Vector Code Correlation (VCC), devised to consider the conditions of real environments. The anti-sway controller is installed on the spreader. The controller has a role to suppress the sway motion of the spreader, as soon as possible. We employ the simple mechanism, so that it can be easily applicable to an existing system. The details and performance of the container crane system is introduced together with the experimental results performed with the model system. In this paper, we will also show that the system has the sufficient efficiency and accuracy for the use on practical job-site.

Novel fiber optic sensor using heterocore structures and its applications

A novel structure of fiber optic sensor has been developed which is characterized by a short-length, different core- size fiber insertion in a fiber as a transmission network line. Two types of a macrobending sensor and an environment sensitive sensor are demonstrated. The macrobending sensor is expected in the use as multi-points (quasi-distributed) sensor. The environment sensitive sensor has the capability of interrogating with environmental conditions. The detailed structure and sensing principle of these new types of sensors are reported together with an experimental setup example arranged from the practical point of view and its attractive applications.

Diode laser interrogated single-mode fiber optics with a hetero-core structure for a wearable glove sensing application

We have developed hetero-core fiber techniques interrogated with a semiconductor diode laser based on single-mode transmission for wearable glove sensing applications. The hetero-core fiber sensor is suitable for the wearable sensing glove because of the advantages of the capable optical intensity-based measurement with the excellent stability of the usage of the single-mode transmission fiber and independence of temperature fluctuation. In order that the hetero-core sensor was unaffected to the random wrinkles at the position of joints in a glove garment, the hetero-core sensor elements were located in the back of hand. As a result, the hetero-core flexion sensor could detect the joint angle of fingers regardless of differences of their size of hands, and the hetero-core sensing technique enables the sensing glove to equip the minimum number of sensors. The optical loss performances of the hetero-core sensors have indicated monotonic characteristics with the flexion angle of joints. The optical loss change is 1.35 dB for the flexion angle of approximately 97.2 degrees with accuracy of detectable flexion angle of 0.84 degree. Real-time hand motion capturing was successfully demonstrated by means of the proposed wearable sensing glove with hetero-core fiber techniques without restricting human natural behaviors.

Practical applications of the brightness approximation plane method with a simple parameter

When processing an image that contains complex intensity changes, it is generally difficult to select an appropriate processing technique and to determine suitable weighted coefficients for a specific purpose since such choices require an advanced level of understanding and experience of image processing technology. To overcome these problems that occur in actual applications, we have attempted to simplify the parameter setting for detecting complex intensity changes by using the brightness approximation plane method that is capable of detecting a wide range of intensity changes by adjusting the sizes of its parameters. This paper describes the advantages of applying this simplification to applications in real environments. In addition, we verified the effect of changing the section size on the ability of the method to detect intensity changes and how this detection ability was affected by using a one-parameter filter compared with using a conventional differential filter ; this was done by estimating the acceptable range for intensity gradients and the robustness to capture noise. The experimental results for detection ability and robustness demonstrated that the proposed method has considerable potential to be used on-site in practical applications.

Void creating inside a transparent resin material using nano-pulse Nd: YAG laser

In our laboratory, new three-dimensional memory using interference pattern caused by void array has been proposed. In this method, Interference pattern is obtained by irradiating visible laser to void arrays as a slit. Information has been written in transparent materials with void array and read out with interference pattern analysis and the void array restoration. The void creating from 4&mgr;m to 10&mgr;m has been successful using nano-pulse Nd: YAG laser. These created voids are fulfilled conditions of forming an interference pattern. It is suggested that reading out of information has been available using interference pattern. Probability of the void creating is too low and a crack might be generated on the past investigation. In this study, the parameter of irradiation energy and number of irradiation has been explored for the void creating with high probability.