Design of near-field recording optics using truncated hemispherical SIL with cover-layer incident dual recording layers

In this paper, we propose a novel optics design for media inside near-field recording (NFR) using a truncated hemispherical solid immersion lens (HMS). To obtain strong advantage of data protection and high data capacity simultaneously, a truncated HMS based near field optics with cover-layer incident dual recording layers is designed. In this design, to improve the small optical tolerance of the truncated HMS unit and to adjust dual focusing positions, an additional aspheric lens surface is added on top of the truncated HMS and it is combined with zoom optics composed of two single lenses having a low numerical aperture (NA). Also, to compensate for chromatic aberration, which is a serious problem for optics using a blue laser diode, a diffractive optical element is also designed. Using zoom optics, an additional aspheric lens surface, and a diffractive optical element together, the wavefront aberration and chromatic aberration are effectively reduced in a broad range of cover-layer thicknesses and wavelength variations. In addition, in this paper, the effect of a gap induced aberration is investigated by analyzing the different behavior of each TM and TE wave for the cover-layer incident NFR optics.Paper presented at the 15th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 28–29 June, 2005.     

Assembly and evaluation of a SIL optical head for cover-layered incident NFR without disk contact with the bottom surface of a SIL

In the assembly of the solid immersion lens (SIL) optical head for cover-layered incident near-field recordings (NFRs), disk contact with the bottom surface of the SIL has previously been regarded as essential. This is because SIL optical heads are designed to interface with a cover layer. However, SILs can be contaminated and damaged by this contact. We present a new SIL optical head assembly method for cover-layered incident NFRs without disk contact with the bottom surface of the SIL. To achieve this, we added zoom optics to a Twyman–Green interferometer in the measurement beam optical path. Our assembly method eliminates SIL contamination problems and the assembly procedure becomes simple because of removing the disk contact process. In addition, it is not necessary to consider the aberrations induced by disk tilt and cover-layer thickness variation. The SIL optical head assembled by the proposed method has good optical performance satisfying the optical tolerances and the measured wavefront aberration is good agreement with simulations.     

Microfabricated silicon solid immersion lens

We present the microfabrication of a solid immersion lens from silicon for scanning near-field optical microscopy. The solid immersion lens (SIL) achieves spatial resolution better than the diffraction limit in air without the losses associated with tapered optical fibers. A 15-μm-diameter SIL is formed by reflowing photoresist in acetone vapor and transferring the shape into single-crystal Si with reactive ion etching. The lens is integrated onto a cantilever for scanning, and a tip is fabricated opposite the lens to localize lens-sample contact. Using the Si SIL, we show that microfabricrated lenses have greater optical transparency and less aberration than conventional lenses by focusing a plane wave of 633-nm light to a spot close to a wavelength in diameter. Microlenses made from absorbing materials can be used when the lens thickness Is comparable to the penetration depth of the light. Tolerance to errors in curvature and thickness is improved in micromachined lenses, because spherical aberrations decrease with lens diameter. We demonstrate scanning near-field optical microscopy with the Si SIL and achieve spatial resolution below the diffraction limit in air by resolving 200-nm lines with 633-nm light     

Application of megasonic cleaner to sub-micron particles of SIL optical flying head

 As the demand for large capacity storage drives has increased, the flying height of near-field recording (NFR) sliders becomes as small as 100 nm for super high storage density. Accordingly contamination problems have been a concern of information storage industry because it may cause a serious damage to solid immersion lens (SIL) of optical flying head. Sub-micro contaminants in air bearing of the NFR slider may affect the flyability and stability of the optical slider. In addition, the cleaning of small particles becomes more difficult as the contaminant particle size decreases because the adhesion force increases very much as the particle size decreases. Recently developed high-frequency ultrasonic (megasonic) cleaning technique have made it possible to remove sub-micron particles less than 100 nm without surface erosion and many remarkable results have been reported. In this paper, the megasonic technique is applied and tested for the cleaning of the flying head of NFR drive. 1 MHz ultrasound with maximum 100 W was used to remove polystyrene latex (PSL) particles and alumina particles deposited on the surface of the slider. Effective cleaning performance was observed without any damages on the slider surface using optical microscope and AFM at different ultrasonic energy levels and cleaning times. Received: 20 June 2002 / Accepted: 9 September 2002     

80万吨/年甲醇项目安全完整等级(SIL)回路计算实例分析

安全完整性等级(SIL)评估技术是近几年发展起来的针对石化行业一种基于风险的资产管理方法,国际标准IEC61508和IEC61511的制定为石化工业等过程工业的安全完整性水平评估提供了依据,对于石化行业的安全生产水平具有重要的促进作用。本文根据80万吨/年甲醇项目的安全完整性等级计算的过程介绍安全完整性等级的计算方法,为项目的建设验收以及装置的技术改造提供理论依据。     

Improved safety mode considering external shock direction for near-field recording system using SIL

To increase the near-field coupling efficiency in a near-field recording (NFR) system, extremely small air gap (less than 100?nm) between the solid immersion lens (SIL) and media should be maintained. However, maintaining the air gap is very important and difficult. Despite various anti-shock control methods, there are physical limitations to controlling the air gap against external shock. A safety mode that moves the actuator to the initial position for large external shock is currently being used. The existing safety mode exhibits good performance for downward shocks of 6?G amplitude and 10?ms duration time, but some problems arise for upward shocks of 3?G amplitude and 10?ms duration time. To avoid collision for upward and downward shocks, we present an improved safety mode that considers the direction of the external shock for an SIL-based near-field recording system. We analyzed the upward and downward shock responses of the NFR system. The shape of the pulse input was designed to minimize the overshoot of the actuator. Through various experiments, the amplitude and duration time of the pulse input were optimized. Even with an upward shock with 8?G and 10?ms, no collision was observed between the actuator and the media by using the improved safety mode with the optimized pulse input.     

Optical recording system using an integrated solid immersion lens

 Nobody doubts that the high area density recording and miniaturization of the devices in the data storage are in the general trend. What matters now is how to compact the data in a small area and how to decrease the device size. For the last decade, a lot of researchers engaged in the optical memory have expected the near-field recording (NFR) technology to be able to bring the remarkable results. However, they have been confronted with many obstacles including heat, contamination, dynamics of optical head in the unsealed environment, etc. In this paper, we propose the new concept of a solid immersion lens (SIL) with a potential to be able to resolve the critical issues on the way to the commercialization of the high areal density optical recording using the near-field recording technology. Received: 5 July 2001/Accepted: 17 October 2001     

Efficient Ray Tracing Through Aspheric Lenses and Imperfect Bokeh Synthesis

We present an efficient ray‐tracing technique to render bokeh effects produced by parametric aspheric lenses. Contrary to conventional spherical lenses, aspheric lenses do generally not permit a simple closed‐form solution of ray‐surface intersections. We propose a numerical root‐finding approach, which uses tight proxy surfaces to ensure a good initialization and convergence behavior. Additionally, we simulate mechanical imperfections resulting from the lens fabrication via a texture‐based approach. Fractional Fourier transform and spectral dispersion add additional realism to the synthesized bokeh effect. Our approach is well‐suited for execution on graphics processing units (GPUs) and we demonstrate complex defocus‐blur and lens‐flare effects.     

基于Navarro示意眼模型的视觉真实感绘制*

结合人眼光学建模和计算机图形学的真实感绘制技术,提出一种基于Navarro示意眼模型的人眼视觉真实感绘制方法.利用Navarro模型与传统的单透镜模型相比能够更精确地模拟人眼的特性,将Navarro模型引入视觉真实感绘制中;采用光线追踪方法,加入非球面折射面的计算,精确地模拟人眼的成像特性.实验结果表明此种方法能够更精...     

Fabrication of high fill-factor aspheric microlens array by dose-modulated lithography and low temperature thermal reflow

Microsystem Technologies - A cost-effective fabrication method for high quality and high fill-factor aspheric microlens arrays (MLAs) is developed. In this method, the complex shape of aspheric...     

MidCloud: an agent‐based middleware for effective utilization of replicated Cloud services

The Cloud relies heavily on resource replication to support the demands of the clients efficiently. Replicated Cloud services are distributed across large geographic areas and are accessible via the Internet. This paper describes MidCloud; an agent‐based middleware that provides Cloud clients with dynamic load balancing and fault tolerance mechanisms for effective utilization of replicated Cloud services and resources. MidCloud can be used to connect clients with multiple replicated Cloud services and provide fast and reliable service delivery from multiple replicas. Several approaches for load balancing and fault tolerance in distributed systems were introduced; however, they require prior knowledge of the environment's operating conditions and/or constant monitoring of these conditions at run time that allows the applications to adjust the load and redistribute the tasks when operational conditions change and when failures occur. These techniques work well when there is no high communication delay. Yet, this is not true in the Cloud, where data storage and computation servers are scattered all over the world and communication delays are usually very high. MidCloud deploys approaches to reduce the negative impact of high and dynamic delays on the Cloud servers and the Internet. The experimental results show the positive effects of using MidCloud to provide efficient load balancing and fault tolerance. Copyright © 2013 John Wiley & Sons, Ltd.     

In-situ fabrication of an out-of-plane microlens with pre-definable focal length

Out-of-plane microlenses are an important component for integrated optics. Unlike their in-plane counterparts, the fabrication of out-of-plane microlenses is more complicated, which limits their applications. In this paper, a new technique that is capable of fabricating out-of-plane microlenses is described. The resulting lenses have pre-definable focal length and can focus light beams not only in the horizontal plane, but also in the vertical plane. The fabrication process is completely compatible with the soft lithography technique. The lens chamber with two thin polydimethylsiloxane (PDMS) membranes was designed and fabricated together with microfluidic or other components using the same UV lithography mask. The lens was then formed in an in-situ fashion. Curable polymers were injected into the lens chamber and cured while pneumatic pressure was applied to keep the PDMS membranes deformed in a quasi-spherical profile. Pneumatic pressure and membrane thickness can be adjusted to control the resulting lens focal length. With a group of lens chambers with different membrane thickness, a single pressure line can be used to fabricate microlenses with different focal lengths. Since cured polymer was used as the lens filling material, the resulting lens can be used without a pressure source. Different polymers can be selected for desirable optical properties. The simulation and experimental results have proved the feasibility of this technique and resulting lens showed good focusing ability for a divergent light beam from an on-chip multi-mode optical fiber. The small design footprint, total compatibility with soft lithography and technical versatility of this technique make it particularly useful for intergrating out-of-plane microlens into microfluidic chips, which may open new possibilities for the development of on-chip optical detection system.     

基于轴对称非球面元件的加工模型研究

轴对称非球面元件具有优良的光学性能,在现代光学系统中的应用占有越 来越大的比例,对其加工质量和加工精度的高要求给光学元器件的制造业带来更大的挑战。 针对轴对称非球面的精密磨削加工系统中的金刚石砂轮加工要求,提出了合理的原理方案, 给出了合适的加工模型,为平面砂轮加工非球面元件提供了可行的技术方案。     

Micromachined silicon nitride solid immersion lens

We present a fabrication method for silicon nitride solid immersion lenses (SILs) integrated with atomic force microscope (AFM) cantilevers. We demonstrate a scanning optical microscope based on the microfabricated SIL that operates in reflection and transmission modes at a wavelength of /spl lambda/ = 400 nm. In this microscope, light is focused to a spot in a high refractive index SIL held close to the sample. The minimum spot size of a SIL-based microscope, which determines the transverse optical resolution, is /spl lambda//(2n) where n is the refractive index of the SIL. This is smaller than the minimum spot size of /spl lambda//2 in air. The SIL, therefore, makes possible optical resolution better than the diffraction limit in air. The full-width at half-maximum (FWHM) spot size of the SIL-based microscope is measured to be /spl sim/133 nm in transmission mode, which is /spl sim/1.98 times better than the spot size measured without the SIL (264 nm). This improvement factor is close to the refractive index of the silicon nitride SIL (n = 1.96).     

基于ARM的模拟量输入模块安全设计

根据IEC61508对可编程逻辑器件功能安全的要求,提出基于ARM的模拟量输入模块的安全设计。介绍该设计使用的诊断技术及其实现方法。该设计使用2块ARM分别用于工作和检测,具有较高的诊断覆盖率,符合IEC61508关于安全完整性的要求,适用于SIL3/SIL4的安全系统。     

Molding and hot forming techniques for fabricating plastic aspheric lenses with high blue-light transmittance

The purpose of this paper is to use micro-electroforming and hot-embossing technology as an alternative to high-cost precision cutting or traditional injection molding in the fabrication of plastic aspheric lenses with high Blu-Ray transmittance. The female dies for the aspheric lenses are fabricated from UV-cured SU-8 polymer via electrostatic attraction. However, SU-8 has a 405 nm Blu-Ray transmittance of only roughly 40–50%, which is not appropriate for use in high-density optical pickup systems. This paper, therefore, uses low stress, low surface roughness, nickel micro-electroforming and molding technologies and employs a micro hot-embossing system to form aspheric lenses with high Blu-Ray transmittance from COC plastic (transmittance: 88% at 405 nm). The resulting lenses have a clear aperture of approximately 1 mm and a numerical aperture of roughly 0.6. The electroforming mold has a roughness of approximately 8 nm as measured by AFM. The roughness of COC (n = 1.53) aspheric lenses after hot-embossing is approximately 146 nm (300 µm × 220 µm) as measured by white light interferometer (WYKO). The shape precision of the hot-embossing COC and original SU-8 (n = 1.67) aspheric lenses can be controlled with approximately 2.638% error. The spot size of the hot-embossed COC and original SU-8 aspheric lenses can be controlled with approximately 11% error. This error should account for the material refractive index difference and the shape error. The roughness and spot size were also tested using different pressing temperatures and forces. This technology could be developed to fabricate lenses in Blu-Ray 405 nm micro-optical systems.     

Recovering distributed objects

Distributed multithreaded applications operating in shared-nothing environments present challenges to classical fault tolerance mechanisms. The piecewise determinism assumption is lost (due to multithreading), and data must be replicated (because of the shared-nothing environment). In this paper, we explore a systematic approach to providing fault tolerance, by considering data-race-free programs that have the benefits of piecewise determinism and yet allow multithreading. We base our logging and recovery algorithm on a logical ring structure that allows the underlying distributed system to migrate threads, migrate and replicate objects, and perform multi-object transactions.     

Design of optical path of pickup for small form factor optical disk drive

We designed an optical path of pickup for the small form factor optical disk drive that is compatible with Blu-ray Disc format using 405 nm wavelength laser, 0.85 NA objective lens, and the 0.1-mm thick cover layer. The optical path consists of a high NA objective lens, a micro compensatory lens that is fabricated by micro-molding process, three reflective mirrors and a partial mirror. The optical performance of the optical path is analyzed and the expected yield ratio is calculated for 22 tolerance parameters by using Monte Carlo method. Finally, the micro compensatory lens is fabricated by micro-molding process.     

基于测量值计算像差的关键技术研究

针对加工非球面注塑模具成本高、周期长的缺点,提出一种改进的试制方法,用光学间隔和玻璃元件曲率半径补偿非球面面形误差产生的像差,以减少修模次数.为按实际非球面测量值计算像差,提出一种计算非球面参数的方法,用曲面上的三维坐标测量值提取标准非球面方程的参数.首先在两个相互垂直的近似的中心剖面附近取值,并分别投影到这两个平面上;然后拟合曲线;再用这两条曲线在各自的平面内截取一组平行直线成一组线段,改变直线的斜率,使各线段中点共线,确定非球面的对称轴和顶点坐标;最后,平移、旋转坐标系后,将三维坐标降维,用多项式拟合成二维曲线,同时将标准形式方程中的无理项展为泰勒级数,对比二者的系数,得到标准非球面方程的参数.大量随机取值计算的统计结果表明,算法的误差达到测量误差的1/3.