Analysis of Optical Disk Readout Signal Deterioration Caused by Dust on the Substrate

A noise power spectrum estimation method is presented for optical disk readout signal influenced by dust on the substrate. The noise due to dust has been modeled using geometrical optics and assuming the Poisson distribution for the dust particles. The noise power spectrum consists of two components: one comes from the effect of individual dust particles passing across the light beam, and the other comes from the effect of overlapping area of a particle and the inverted image of another particle. The feasibility of a thin-substrate optical disk was studied using this model. Dust will not have a serious effect on the readout signal when a 0.6 mm-thick substrate is used in place of the conventional 1.2 mm-thick substrate.     

一种新型磁光盘驱动器光学头光学系统

本文叙述了一种新型磁光盘驱动器光学头的光学系统,并从理论上阐明了磁光信息读取的基本原理.该系统改善了光学系统性能,减少了系统噪声,提高了光能利用率,并用于5(1/4)时的磁光盘驱动器开发研究,获得读取信息的信噪比优于50dB的结果.     

Optical Pickup with a Spherical Aberration Compensator Using a Crossed-Stripe Liquid Crystal Device

To increase recording density in an optical disk system, a two-lens system which enlarge its numerical aperture (NA) has been developed. When NA becomes larger, however, the spherical aberration due to disk thickness error increases. We propose an optical pickup with a spherical aberration compensator using nematic liquid crystal (LC). Our LC device is composed of two LC cells each of which has X and Y stripe electrodes, respectively. We discussed how the spherical aberration due to the disk thickness error can be compensated by combination of two crossed cylindrical phase distributions induced by the LC cells, and confirmed the compensation effect in a design example by simulation. We have also fabricated the crossed stripe LC device actually, and have obtained the experimental result which shows that amount sufficient to compensate the aberration is achieved.     

振荡吸积盘的光变研究

理论研究指出随机振荡吸积盘可能引起活动天体的光变,然而观测数据分析表明光变中除了含有随机噪声外还存在混沌因素.将混沌因素引入到随机振荡吸积盘中,构成"混沌+随机"振荡吸积盘模型.通过分析扰动的相图,直观再现了混沌吸引子的状态.研究结果表明:在随机因素占主导时,光变混乱无序;随机因素与混沌因素相当时,光变上下起伏类似于心电图;混沌因素占主导时,光变具有一定有序性.模拟光变曲线的关联维与观测数据的关联维一致,表明模拟光变曲线与观测结果之间存在内在联系.     

磁光盘光头瞬态光学特性研究

本文研究了磁光盘光头的瞬态光学特性,其结果实现了光头部件的最优化设计。     

光盘光学系统的矢量衍射理论分析

本文以完整的矢量衍射理论分析了光盘光学系统。首先将入射的聚焦光束分解为平面波谱 ,得到每个平面波的振幅矢量 ;然后计算光盘对每个平面波的衍射 ,得到衍射波的振幅矢量 ,从而得到了整个衍射波场的空间频谱 ;最后计算物镜光瞳上的能通量 ,得到光盘系统的读出信号。在衍射计算中 ,光盘被定义为二维金属光栅 ,根据信息符的不同模型 ,选用坐标变换方法、耦合波方法或模态方法。对于典型的 DVD光学系统来说 ,矢量理论的结论与标量理论相差甚远 ,要得到正确的结果就必须采用矢量衍射理论     

玻璃光盘基片

本文对制备光盘的各种材料的性能做了比较,叙述了采用白冕平板玻璃研制直径为133.35mm可擦除光盘基片的工艺过程,以及产品达到的性能指标。     

Collision Statistics of Driven Polydisperse Granular Gases

We present a dynamical model of two-dimensional polydisperse granular gases with fractal size distribution, in which the disks are subject to inelastic mutual collisions and driven by standard white noise. The inhomogeneity of the disk size distribution can be measured by a fractal dimension df. By Monte Carlo simulations, we have mainly investigated the effect of the inhomogeneity on the statistical properties of the system in the same inelasticity case. Some novel results are found that the average energy of the system decays exponentially with a tendency to achieve a stable asymptotic value, and the system finally reaches a nonequilibrium steady state after a long evolution time. Furthermore, the inhomogeneity has great influence on the steady-state statistical properties. With the increase of the fractal dimension df, the distributions of path lengths and free times between collisions deviate more obviously from expected theoretical forms for elastic spheres and have an overpopulation of short distances and time bins. The collision rate increases with df, but it is independent of time. Meanwhile, the velocity distribution deviates more strongly from the Gaussian one, but does not demonstrate any apparent universal behavior.     

A superresolution optical disk with a combination of optical path filtering and saturable absorption techniques

Calculations have been done for the modulation transfer function of a superresolution optical disk with a combination of optical path filtering and saturable absorption techniques. The results reveal that optical path filtering alone can only equalize, to a certain degree, the spatial frequency response of the opticaldisk system, but it can not attain any response beyond the cutoff frequency. With an additional saturable absorption layer in-between the substrate and the information layer, it is found that the optical response both under and beyond the cutoff frequency can be greatly improved.     

Pressure-sensitive paint measurement on co-rotating disks in a hard disk drive

There is much demand for improvement in the performance of a hard disk drive (HDD) along with recent rapid developments of information technology. While high-speed disk rotation of a HDD is necessary to accommodate such needs, it causes disk flutter induced by pressure fluctuation on disks and degrades reliability of a HDD. In order to understand the mechanism of the fluttering phenomenon, it is important to know pressure field on the rotating disk. However, it is impossible to measure the pressure by ordinary methods such as pressure taps. Pressure-sensitive paint (PSP) is a pressure measurement technique based on the oxygen quenching of luminescence and enables us to measure the pressure non-invasively. In general, however, the temperature sensitivity of PSP makes it difficult to measure the precise pressure on the surface with temperature distribution. We measured the time-averaged pressure on the disk rotating at 10 000-20 000 rpm for the first time by adopting a temperature-insensitive PSP composed of pyrene sulfonic acid (PySO₃H) as a luminophore. It was found that the pressure forms a concentric circular distribution and decreases toward the center of the disk. Additionally, we elucidate how disk rotational speed and spacing between co-rotating disks influence on the pressure field.     

基于有限状态机的光存储伺服系统设计

采用有限状态机描述光存储伺服系统的状态转换过程。有限状态机通过CPLD硬件实现,以控制光学头的运动状态。根据DVD伺服标准的要求,设计超前滞后补偿器对整个伺服环路进行补偿。利用标准光学头和标准盘片对整个伺服系统进行了测试。测试结果表明,该伺服系统精度较高,聚焦精度小于10%,循迹精度小于20%,对于标准盘片能得到较高的Jitter(<8%)。     

二元光学元件和新型超分辨光盘读写头的设计研究

本文采用杨-顾相位恢复算法数值模拟设计了一个用于光盘读写头的二元光学元件,并构思了一种新型超分辨光盘读写头,在现有光盘读写头的激光波长处和数值孔径基础上,利用该二元光学元件实现光学超分辨,从而提高光盘存储容量.     

磁光盘静态测试仪

本文描述了一台由金相显微镜改装的,可擦重写磁光盘材料的评价装置。它具有激光功率,脉宽以及外磁场变化范围大的特点。同时,能进行材料读写性能,灵敏度,均匀性和重复擦写次数的测量。全部测量过程都由计算机控制,操作方便。使用结果表明,它是评价光盘材料和制盘工艺的有用设备。     

Spot Shape on Super-Resolution Optical Disks with a Photon-Mode Mask Layer

The spot shape on super-resolution optical disks with a photon-mode mask layer was theoretically analyzed. The spot shape was found to depend on the lifetime of the bleached state of the dyes, the light power, and the disk rotation speed. When the lifetime is short, the super-resolution spot shape is not produced at high disk speeds. On the other hand, a dye mask layer with long lifetime, such as a photochromic mask, can produce a sharp spot shape in the higher disk speed region, and therefore is suitable for obtaining a super-resolution disk with a high data transfer rate.     

参数不定的旋转圆盘在有界扰动下混沌振动的滑模变结构控制

为了消除具有不确定参数的旋转圆盘横向混沌振动,克服其对整个系统及工作状况的不利影响,假设作用在旋转圆盘上的集中力不确定且有界,并鉴于干扰的普遍存在性,对有界扰动下的旋转圆盘横向振动的四维非线性方程进行了复杂动力学特征分析,包括相轨迹图、Lyapunov指数和庞加莱映射图,这些特征加深了对其的认识,同时也证明该四维动力系统含有混沌吸引子.为了保证系统控制的鲁棒性,利用滑模变结构法,将旋转圆盘从混沌轨道先后控制到任意固定点和周期轨道,并用MATLAB模拟验证其有效性.结果证明,用滑膜变结构法能够使系统严格地跟 关键词： 旋转圆盘 混沌 滑模变结构控制 有界扰动     

光纤1/f热噪声的实验研究

光纤热噪声是限制光纤传感、测量系统性能的最终因素.但是低频区域呈1/f谱特性的光纤热噪声的形成机制迄今仍然存在争论.实验研究了光纤1/f热噪声水平与光纤内杂质离子浓度和光纤施加张力的关系,验证了这类热噪声来源于光纤内部的机械耗散引起的长度自发抖动,符合热机械噪声的理论假设.     

Absorptive and dispersive optical profiles in fluctuating environments: A stochastic model

In this study, we determined the absorptive and dispersive optical profiles of a molecular system coupled with a thermal bath. Solvent effects were explicitly considered by modelling the non-radiative interaction with the solute as a random variable. The optical stochastical Bloch equations (OSBE) were solved using a time-ordered cumulant expansion with white noise as a correlation function. We found a solution for the Fourier component of coherence at the third order of perturbation for the nonlinear Four-wave mixing signal and produced analytical expressions for the optical responses of the system. Finally, we examined the behaviour of these properties with respect to the noise parameter, frequency detuning of the dynamic perturbation, and relaxation times.     

卫星光通信中恒星背景噪声分析及抑制方法研究

建立了以恒星目视星等、等效温度为参数的恒星辐射谱模型,使利用恒星数据库进行背景噪声分析变得更加简捷。在此基础之上,分析了恒星自身特点及卫星光通信终端参数对背景噪声的抑制能力,提出并定义了抑制参数Ψ,以评价卫星光通信系统的抗噪性能;同时考虑背景噪声光功率对卫星光通信的影响,给出了补偿方法;分析结果表明,通过提高CCD采样频率、降低光学系统带宽等方法,可以有效地减少恒星噪点,降低恒星背景光对卫星光通信系统的影响。该项工作为进一步优化卫星光通信系统参数,提高其空间运行的稳定性打下了基础。     

Drive-based recording analyses at >800 Gfc/in using shingled recording

Since the introduction of perpendicular recording, conventional perpendicular scaling has enabled the hard disk drive industry to deliver products ranging from ∼130 to well over 500 Gb/in² in a little over 4 years. The incredible areal density growth spurt enabled by perpendicular recording is now endangered by an inability to effectively balance writeability with erasure effects at the system level. Shingled magnetic recording (SMR) offers an effective means to continue perpendicular areal density growth using conventional heads and tuned media designs. The use of specially designed edge-write head structures (also known as ‘corner writers’) should further increase the AD gain potential for shingled recording. In this paper, we will demonstrate the drive-based recording performance characteristics of a shingled recording system at areal densities in excess of 800 Gb/in² using a conventional head.Using a production drive base, developmental heads/media and a number of sophisticated analytical routines, we have studied the recording performance of a shingled magnetic recording subsystem. Our observations confirm excellent writeability in excess of 400 ktpi and a perpendicular system with acceptable noise balance, especially at extreme ID and OD skews where the benefits of SMR are quite pronounced. We believe that this demonstration illustrates that SMR is not only capable of productization, but is likely the path of least resistance toward production drive areal density closer to 1 Tb/in² and beyond.     

On the Similarity of the Statistical Characteristics of Spontaneous Radiation of a Quantum Amplifier at Different Gain Factors

The transformation laws governing the statistical properties of the quantum noise of an optical amplifier when its gain factor and spectral line profile are varied are considered. The correlation functions of quantum noise both at the amplifier output and after nonlinear transformation normalized to the correlation time of quantum noise at the amplifier output were found to be independent of the amplifier gain provided that it exceeds 10 for the Gaussian spectral line profile and 10³ for the Lorentzian profile. The spectral density of quantum noise transformed in a nonlinear system was shown to possess the same similarity property. It was found that the statistical characteristics possess a similarity property even in the case of variation of the spectral line profile from Gaussian to Lorentzian. It was concluded that such a characteristic of quantum noise of an optical amplifier as the correlation time bears virtually all information on the above-mentioned statistical properties at a reasonably large amplifier gain. The similarity property revealed has an important application. It allows finding the matching condition between the optical signal spectrum and the gain profile of the optical quantum amplifier to achieve the highest sensitivity of signal detection by the amplifier.