High speed sub-micron bit detection using tapered aperture mounted optical slider flying above a patterned metal medium

Rapid advances in the development of the digital network society have necessitated both large capacity and higher data transfer rate for every type of digital storage equipment. Proximity optical recording based on the near-field interaction principle promises to provide breakthroughs in overcoming rigid optical diffraction limits and wave length shortening limits. We have previously presented a compact optical head assembly consisting of a combination of a pyramidal hole processed silicon slider and light-wave guide combined suspension. Attaining higher recording density requires both a much smaller sized aperture and a highly efficient laser power delivery mechanism. To satisfy these requirements, we have introduced a planar lens and tapered aperture processed optical slider, delivering laser power through a single mode optical fiber, and we have demonstrated sub-micron size (150–200 nm-long) bit signals at more than a 10 MHz frequency band.The authors would like to thank Mr. Tamotsu Kusumi and Tadashi Sasagawa, Nikon Corp. for their processing of fine 350 nm line and space patterns on thin chromium films using short wavelength light lithography. The authors would like to thank Dr. Hisataka Takenaka and Dr. Hisashi Ito, NTT Advance Tecnology Corp., for forming a high quality carbon protective overcoat on the patterned media. The authors also would like to thank Dr. Takanori Doi, Toda Corp., for his helpful suggestions and careful treatment in forming the lubricant layer on the patterned metal media. The authors would also like to thank Mr. Masanori Sahara and Mr. Takashi Suzuki for their useful advice in applying the APD in our readout system.     

Tracking and readout characteristics of a minute aperture mounted optical head slider flying above a chromium patterned medium

Recent rapid progress in a digital network society necessitates storage devices with higher-density and faster transfer rates. In optical storage, a novel recording principle is eagerly awaited that will drastically improve recording density without being restricted by a wavelength shortening limit or a numerical aperture (NA) limit of the optics utilized. Storage based on the “near-field” principle is thought to be one of the most promising breakthroughs for overcoming various limitations governing traditional optical recording. We have already proposed an integrated optical head slider assembly that relies on the novel near-field principle for its operation; it is mounted on a minute tapered aperture and has a planar focusing lens and a micro silicon mirror. Readout signals corresponding to a 200-nm-long bit have demonstrated a frequency band up to approximately 10 MHz, using a chromium patterned medium. In this study, we have investigated the accuracy of the tracking characteristics of an aperture-mounted head slider by using linearly arranged 1-mm-long line-and-space patterns. Based on the step or inverse step responses that occur when an aperture flies obliquely across the linearly arranged pattern region boundary, we present a simple method of predicting accurate tracking characteristics in detail, and also by using a 350-nm line-and-space pattern signal, we were able to predict both tracking characteristics and tracking sensitivities of arbitrary wide tracks to a track width of 100 nm.     

100-nm-Wide track pattern readout using a protruded triangular aperture mounted optical head slider

In this study, we evaluated the read-out signal quality from narrow track patterns, utilizing linearly arranged slender track patterns, while changing the track width from 10 to 0.1 ??m and the pattern density from 200?nm line-and-space (L/S) to 120?nm L/S. To acquire narrow track readout signals, we adjusted the aperture??s in-plane position to cross a linear track at shallow angles of less than 1°, and we could successfully transform directly acquired signals into those of an aperture crossing tracks at a right angles. The results of an experiment utilizing a 10-??m-wide track (which is thought to represent an infinitely wide track) clarified that the stationary field was spread to an approximately 1.2?C1.6?times larger region than the typical aperture size of 330?nm. The results also clarified that the ??field spread?? depended on the pattern density, that is, the case in which polarization direction ?? equals 0 or 45°, and that the field spread increased monotonically as the line or space width became smaller. When the polarization direction equals 90°, the field spread had its local maximum when the line or space width was approximately 150?nm. An approximate prediction of the read-out signal amplitude was based on the rule that the signal amplitude was proportional to the net field spread that passed across the track pattern, and this prediction corresponded well to the experimental results, except when the interaction between the stationary field and the track side walls was not taken into account.     

Sub-100-nm ROM pattern readout using a triangular protruded aperture mounted optical head slider

The continual advancement of the digital network society demands higher density and higher data transfer rates for all sorts of data storage. Optical memory based on the “near-field” principle is considered one of the most promising ones because it has no apparent physical density limit such as that due to the thermal instability encountered in magnetic recording. In light of this, we have previously demonstrated the superior readout performance of an optical head slider which is mounted on a non-circular aperture, specifically a triangular aperture having a bottom side size of 330 nm irradiated by polarized light, with this scheme indicating a clear signal response corresponding to a 70-nm-long single slit pattern. In order to fully realize the superior potential of the triangular aperture’s high spatial resolution and high signal output, it is essential to minimize aperture-to-medium spacing. In this paper, we introduce a protruded aperture mounted on a 1.5-mm-long miniaturized optical head slider whose aperture protrudes approximately 20 nm from an air-bearing surface level based on nano-step lithography technology. Utilizing a triangular aperture of 140 nm per side, a readout experiment was carefully performed at an aperture-to-medium spacing down to approximately 30 nm, corresponding to a circumferential velocity of 2.18 m/s. The influence of the incident light’s polarization direction (in relation to the bottom side of the triangular aperture) on the readout signals was evaluated by flying the aperture above a chromium patterned medium having single-space or line-and-space patterns whose line lengths ranged from 300 to 50 nm.     

Readout characteristics of a non-circular aperture mounted on an optical head slider flying above a medium having sub-100-nm-long patterns

The near-field principle combined with thin-film gas-lubricated slider bearing technology is thought to be one of the most promising breakthroughs to overcome the difficult optical diffraction limit (or wavelength shortening limit), which governs traditional optical recording performance. In light of this, we have demonstrated high linear density (150 nm pattern length) and high speed 10 MHz readout signals using the combination of a tapered circular aperture and a planar lens mounted on a quartz slider, flying above a metal patterned medium. In order to further improve both the spatial resolution and signal-to-noise ratio of this device, it is essential to minimize the spacing and laser power throughput of an aperture. Also investigated was the effectiveness of a non-circular aperture, which has approximately triangular configuration in combination with polarized light in simultaneously improving spatial resolution and increasing signal output. In this paper, we confirmed the predicted effectiveness on more practical condition of both high speed and compactness of head construction using a sub-micrometer size non-circular aperture, which was mounted on a 1.5-mm-long miniaturized optical head slider, flying above a ROM medium having sub-100-nm-long chromium patterns. The influence of the electric-field direction of the incident light and aperture to medium spacing on the readout signal are carefully evaluated by flying the aperture at spacing down to less than 50 nm.     

Design of an optical soft sensor for measuring fingertip force and contact recognition

Among the various ways to estimate user intention in hand exoskeletons, a contact force measurement is definitely the most straightforward and intuitive method. A force sensor, located at the center of a fingertip usually, hinders the tactile sensation of the user by blocking the contact between an object and the fingertip. To overcome this problem, a soft force sensor with horse shoe shape is utilized to measure the contact force and provide the tactile sensation to the user. This work presents the mechanical design, implementation and evaluation of a soft fingertip force sensor. To maximize tactile sensation of the user, we adopted a horse shoe shape structure to leave the finger pad exposed. An optical sensing mechanism was selected for its relatively fast response compared to other soft sensors. The whole sensor system has a soft exterior providing flexibility and a user-friendly interface. To evaluate the sensor’s performance, we carried out sensor optimization process and calibration experiment with a customized test bed. Then, we investigated both static and dynamic response and observed the mechanical behavior and light intensity changes caused by the cross sectional shape and base/agent ratio of PDMS. Lastly, we applied the proposed sensor to the glove type fingertip force monitoring system. The sensor estimates the index finger tip force with high accuracy (R ² = 0:96) within 5N range.     

LPG-based optical fibre sensor for acoustic wave detection

In this work, a long period grating (LPG)-based optical fibre sensor system has been designed and set up, following which it has been evaluated and optimized for acoustic wave detection. The device relies upon the interaction of the acoustic wave with a LPG placed between two pillars (with one being movable) and exposed to a range of representative acoustic waves generated by a loudspeaker placed at a known distance from the sensor thus created. Through determining the response both to the variation of the magnitude and the frequency of the acoustic signals generated by the loudspeaker, the long period grating-based sensor system created has been successfully characterized, showing clear sensitivities to specific acoustic frequencies, irrespective of the signal intensity variations. In addition, these frequencies are found to be closely related to the configuration of the LPG, i.e. the LPG bending curvature created which can be varied, in this laboratory set-up, by changing the distance between the pillars. The experimental results obtained are in good agreement with those obtained from a modified elastic string theory approach, and thus show potential for the use of LPG-based technique for acoustic wave detection in various media, to create a compact and easy to use sensor system.     

Mechanical characteristics of a contact optical head slider operating on a metal-layered medium

 Advances in a digital network society require both higher density and higher transfer rates in all sorts of storage systems. Even in optical recording, the trend toward higher density and larger capacity requires novel surface-recording technologies that can drastically diminish head-to-medium spacing, resulting in an improvement in spatial resolution and, finally, a higher recording density. In this paper, we propose a novel contact optical head slider that is able to almost cancel the suspension load by generating hydrodynamic pressure, thus realizing a lower net contact force. A trial-manufactured contact slider being processed four sliding pads on air-bearing surfaces has indicated a gentle variation of both the acoustic emission signal intensity and the friction force as the circumferential velocity changes. Furthermore, a time-domain simulation was performed to investigate the effects of the damping of a medium surface (lubricant) both on slider bouncing and on contact force. Received: 5 July 2001/Accepted: 1 November 2001     

Remote optical detection of biomass burning using a potassium emission signature

A remotely detectable signature for biomass burning that is specific to flaming combustion is found in the strong emission lines of potassium (K) at 766.5 nm and 769.9 nm. Ground level spectra of a test fire illustrate the high contrast signal provided by K emission. Image data collected at high altitude using the Airborne Visible Infrared Imaging Spectrometer (AVIRIS) sensor and analysed for K emission vividly displays the fire fronts of a 1995 fire in Brazil. Sensors for K emission can use silicon detector technology for advantages in high sensitivity, low cost, wide area coverage and fine spatial resolution.     

Joint underwater target detection and tracking with the Bernoulli filter using an acoustic vector sensor

In this paper, we study the problem of joint underwater target detection and tracking using an acoustic vector sensor (AVS). For this challenging problem, first a realistic frequency domain simulation is set up. The outputs of this simulation generate the two dimensional FRequency–AZimuth (FRAZ) image. On this image, the random finite set (RFS) framework is employed to characterize the target state and sensor measurements. We propose to use the Bernoulli filter, which is the optimal Bayes filter emerged from the RFS framework for randomly on/off switching single dynamic systems. Moreover, to increase the performance of detection and azimuth tracking in low signal-to-noise ratio (SNR) scenarios, a track-before-detect (TBD) measurement model for AVS is proposed to be used with the Bernoulli filter. Sequential Monte Carlo (SMC) implementation is preferred for the Bernoulli filter recursions. Extensive simulation results prove the performance gain obtained by the proposed approach both in estimation accuracy and detection range of the system.     

采用光纤干涉腔的瓦斯图像探测传感器研究

针对红外线吸收式瓦斯传感器难以解决的问题:可调谐光源昂贵,调制解调原理复杂并且可靠性低.充分发挥白光干涉的简单可靠、灵敏度高的优势,利用瓦斯中甲烷引起空气折射率变化的特点,构成光纤空气腔的马赫-曾德尔(Mach-Zehnder)干涉仪.通过杨氏干涉在白板上形成干涉条纹,条纹参数和瓦斯体积分数成比例变化.解析条纹变化在高精度测量时采用摄像头进行信息采集,再利用图像分析软件进行瓦斯体积分数计量.同时还可以通过无线与光纤网络进行远程传递.通过实验证明:该方法精确度和灵敏度比较高,可靠性好,使光学瓦斯传感器能够广泛应用.     

微弯光纤力传感器实验研究

探索光纤在载荷力微扰下的输出与力的关系特性，利用压电陶瓷的振动驱动在力作用下的微弯变形器扰动光纤，改变其输出，实验表明，在0.5-12mN范围内输与力成线性关系，线性度为1％，且系统设计具有机械调零，过载保护功能。     

一种基于感声波纹结构的光学式声传感器

设计了一种基于硅MEMS敏感结构的光学式声传感器,其光学调制原理采用强度调制型,微敏感结构采用具有低应力波纹结构的感声薄膜芯片。对光纤与微敏感结构耦合技术进行实验研究,优化光学参数,并制作传感器样品。经实验测试,灵敏度达80mV/Pa。     

光纤声发射传感器的研究现状与展望

光纤声发射传感器是近年来出现的集光学、声学、电子学为一体的新型声发射传感器。介绍了光纤声发射传感器的原理、特点、研究现状和最新进展,以及各类传感器在不同领域的应用情况,提出了目前光纤声发射传感技术存在的问题、发展趋势与展望。     

Pulse-coupled time synchronization for distributed acoustic event detection using wireless sensor networks

Time synchronization has proven to be critical in sensor fusion applications where the time of arrival is utilized as a decision variable. Herein, the application of pulse-coupled synchronization to an acoustic event detection system based on a wireless sensor network is presented. The aim of the system is to locate the source of acoustic events utilizing time of arrival measurements for different formations of the sensor network. A distributed localization algorithm is introduced that solves the problem locally using only a subset of the time of arrival measurements and then fuses the local guesses using averaging consensus techniques. It is shown that the pulse-coupled strategy provides the system with the proper level of synchronization needed to enable accurate localization, even when there exists drift between the internal clocks and the formation is not perfectly maintained. Moreover, the distributed nature of pulse-coupled synchronization allows coordinated synchronization and distributed localization over an infrastructure-free ad-hoc network.     

Simulating the anchor lifting maneuver of ships using contact detection techniques and continuous contact force models

Multibody System Dynamics - Designing the geometry of a ship’s hull to guarantee a correct anchor maneuver is not an easy task. The engineer responsible for the design has to make sure that...     

基于无线传感器网络的岩体声发射信号监测系统

在分析了现有岩体声发射信号监测系统存在局限性的基础上,利用无线传感器网络和压缩感知技术,设计了一种新型岩体声发射信号监测系统,详细叙述了系统结构和软硬件实现方法,并将其应用于高速公路岩体边坡稳定性监测.实际应用结果表明,系统设计方案合理可行,且由于使用了压缩感知技术,在采样频率为200 kHz的情况下,也可实现声发射信...     

Position/force control of a manipulator mounted on a vehicle

To perform complex tasks with a mobile manipulator (consisting of a robot arm mounted on a vehicle) moving outdoors on an uneven ground, a first issue is to develop robust control laws for tasks in a vehicle-embedded frame. So, we have tested the behavior of the robot arm with classical control laws for several disturbances due to the motions of the vehicle. First, we have tested positioning tasks of the end effector with respect to its base reference frame with a Cartesian PID and a Cartesian Variable Structure Control—High Frequency. Then, we have tested hybrid and external force control structures for an experiment of following a surface situated on the vehicle. Results are presented in the form of graphs. © 1996 John Wiley & Sons, Inc.     

A tool breakage detection system using an accelerometer sensor

An on-line and in-process based monitoring system to detect tool breakage via an accelerometer was developed and successfully evaluated in an end milling operation. Prior to testing and evaluation of the tool breakage condition, a simulation model was developed. Transfer of the on-line vibration signal to the frequency domain employed the fast fourier transfer function, and set thresholds were used to determine the tool condition after various experimental tests. In comparison to other in-process methods, such as those that employ dynamometers and acoustic emission sensors, the proposed system is easy to set up and does not require changing of the mechanism. Additional benefits of the system are its high reliability and low cost. Thus, the new monitoring system is potentially useful for untended milling operations in on-line and real-time tool breakage detection in linked-cell manufacturing systems (L-CMS).