菲涅耳数字全息成像系统的焦深

焦深是表征成像系统性能的重要参数.基于透镜相干成像的焦深判据,利用数值积分和计算机模拟的方法,分析和推导了菲涅耳数字全息成像系统的焦深,给出了相应的焦深表达式,并与利用理想成像四分之一波像差的判据得到的焦深进行了比较.结果表明:菲涅耳数字全息成像系统的焦深不同于透镜相干成像系统的焦深.在记录距离和CCD参数一定的条件下,离轴菲涅耳数字全息成像系统的焦深略大于同轴菲涅耳数字全息的焦深;离轴对称偏置情况下的焦深略大于非对称情况下的焦深.利用像强度判据得到的焦深,能够较好地表征数字全息成像系统的性能.     

相位光阑对光学系统中焦深的影响

焦深在高密度光盘存储系统中具有十分重要的作用,大焦深可以使调焦伺服系统容易跟踪盘面。采用标量衍射理论和基于德拜近似条件的矢量衍射理论,分别在低数值孔径和高数值孔径两种情况下,系统研究相位光阑对聚焦光学系统的轴向光强分布和焦深的影响。研究结果表明：相位光阑对光学系统的焦深影响很大,高数值孔径系统中,选择适当的相位光阑几何尺寸可以使焦深提高约6倍。     

三次位相板编码系统的频率信噪比分析

建立了一个基于新型光学/数字成像系统（三次位相板编码系统—CPP系统）的信噪比模型.该模型主要考虑了读出噪音及散粒噪音两种探测器噪音,同时加入光学系统调制传递函数（Modulation Transfer Function,MTF）的影响,考虑不同空间频率下噪音对信号的影响,推导出频率信噪比模型.利用该模型对一个光学/数字成像系统进行信噪比分析,结果表明,利用该模型进行分析后此光学系统可达到的理论焦深扩展范围为5个波长.     

手机成像系统的波前相位编码板光学特性的优化

设计了基于波前相位编码板的轻薄手机镜头,原始成像系统的焦深大小是0.017 mm,使用立方相位编码板,采用基于斯特列尔比的相位板优化方法,保持了在不同离焦位置成像系统MTF的稳定性,最终成像系统设计焦深达到0.136 mm,焦深扩展了8倍,经过Zemax软件仿真,验证了景深延拓的效果。设计结果表明,使用相位编码板即可增大定焦距手机系统的景深,使得系统结构紧凑,又克服了视场效应。     

波前编码显微物镜景深扩展的研究

为了解决传统显微物镜景深与分辨率的矛盾,采用波前编码的方法,设计研究了波前编码的10倍显微物镜,结合传统光学设计软件,采用基于MTF一致性的相位板参数的优化方法,实现了在像面附近一定范围内系统的点扩散函数一致性;此外,还设计了扩展三次相位编码板的10倍显微物镜,比较了采用两种不同相位板系统的焦深扩展的效果,结果显示三次相位板的焦深扩展效果较好,可以将传统10倍显微物镜的焦深扩展15倍。成像模拟仿真结果显示滤波后的编码像在±15倍焦深范围内成像清晰,从而扩大了系统的景深。     

提高微细图形光刻分辨力的相移滤波技术研究

详细研究了提高投影成像光刻分辨力的相移滤波技术的基本理论,给出了理论模型,进行了模拟计算.对不同掩模图形设计制作的不同优化滤波器进行光刻对比实验并取得实验结果.研究表明,相移滤波能显著提高部分相干成像系统光刻分辨力和增大焦深,同时能提高光能利用率,有利于提高光刻生产率,是一种有效提高光刻分辨力和焦深的波前工程技术.     

大焦深离轴超透镜的设计与制作

基于单层超表面结构,设计并制作了一种具有大焦深的离轴超透镜.利用相位叠加的设计方法,将偏转与聚焦这两个功能合二为一以实现离轴聚焦,并通过优化入射孔径和离轴偏转角来增大焦深.实验结果表明:当入射电磁波的频率为9 GHz时,离轴偏转角为27.5°,焦距为335.4 mm,这与30°和350 mm的预设值比较符合.在8,9和10 GHz三个频率下的焦深分别为263.2,278.5和298.2 mm,分别对应波长的7.02倍、8.36倍和9.98倍.该离轴超透镜结构简单,具有良好的离轴聚焦能力和较大的焦深,这在小型化、平面化的大焦深成像系统以及离轴光学系统中具有潜在的应用前景.     

改进型分形波带片的焦深特性研究

提出了一种具有增大焦深特性的改进型分形波带片(FZP).分析并推导了改进型分形波带片基于优化参数w的周期公式;计算了改进型分形波带片在菲涅耳近似下的衍射光场分布以及对应的横向光场分布特性因子,包括分辨率因子(G),施特雷尔比(S)以及旁瓣强度因子(M);同时分析了在不同的径向坐标r和r2下的改进型分形波带片的焦深特性,...     

煤粉颗粒流在不同焦点位置条件下的激发特性

将激光诱导击穿光谱技术应用到煤粉颗粒流测量中,分析激光与样品流相互作用,并考察不同的聚焦焦深对等离子体激发特性的影响。在自行搭建的两相流的实验台架上,在大气环境条件下,利用激光器分别对1.0,0.5,0,-0.5, -1.0 mm焦深作用条件下的煤粉颗粒流进行击穿,同时利用光谱仪对等离子体信号进行采集。在相同的激光能量以及收光角度等条件下,改变聚焦激光的焦深,分析对比不同焦深下的等离子体温度、电子密度以及对煤元素分析中关注的C, Si和Al三个代表元素的光谱强度的变化规律。结果表明,不同的激光聚焦焦深对等离子体温度、电子密度和元素光谱强度的影响规律较为明显,三个参数整体变化规律是一致的,最优点为0 mm,其次为1.0,0.5,-0.5 mm,最劣点为-1.0 mm。     

激光光刻中焦深概念的新探讨

焦深大小将直接影响激光光刻加工的最细线宽和线条的边缘倾角从而影响被加工器件性能.传统的几何光学焦深概念对有光刻胶存在时的激光光刻已不适用.本文导出了会聚的高斯光束用于激光光刻时在光刻胶内的光场近似分布形式,由此可判断出光刻胶对光刻线条的分辨率和焦深的影响,从而提出激光光刻时焦深的新概念和估算.     

一种新型衍射超分辨光学器件

提出了一种提高通过光学系统的部分光线的空间频率,来提高系统分辨率的新型衍射超分辨光学器件。该器件通过把部分低频光线移到高频带,使得艾里斑的主斑变小,同时焦深也得到了延长,模拟计算结果表明,在中心峰值强度相等的条件下,用该器件所获得的超分辨效果比目前最好的纯相位型超分辨光阑要好。     

Optimization of Axial Intensity Point Spread Function

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Axicons用于光学超分辨

提出了用圆锥棱镜构建光束整形器.该器件能将圆形光束转换成环形光束,由它所产生的环形光束的直径是可调的,即系统超分辨效应具有可调节性.给出了理论分析和数值模拟,模拟结果表明此器件可以实现光学超分辨,改变几何参数可以调节超分辨效应.     

Optimization of Axial Intensity Point Spread Function

It is known that for the converged laser beam, the axial intensity distribution corresponds to a Gaussian curve, that is, the intensity on the focal plane is the peak intensity. When it defocuses, the intensity would decrease rapidly. In optical data storage, for instance, we expect the intensity within a certain distance to be almost equal. In this paper, we propose to use a pure phase superresolution apodizer to optimize the axial intensity distribution of the converged laser beam and at the same time improve the resolution. The intensity point spread function remains almost identical in a wide range within the focal depth.     

Gradient force pattern, focal shift, and focal switch in an apodized optical system

In this paper, the evolution of the gradient force pattern, focal shift, and focal switch induced by a three-portion pure phase-shifting apodizer is numerically investigated in detail. The results show that the proposed apodizer may induce tunable gradient force on the particles in the focal region, focal shift, and focal switch. By adjusting the geometrical parameters of the phase-shifting apodizer, multiple traps may occur with changeable distance between them, and the shape of the optical trap also evolves evidently. More interestingly, for certain geometrical parameters of the proposed apodizer, by changing the phase shift of inner annular portion, the considerable focal shift may occur with focal switch accompanying, which is discussed to show that this kind of apodizer may be a very promising method of transporting trapped particles.     

Blue laser phase change recording system

The migration paths from DVD phase change recording with red laser to the next generation optical disk formats with blue laser and high NA optics are discussed with respect to optical aberration margins and disc capacities. A test system for the evaluation of phase change disks with more than 20 GB capacity is presented and first results of the recording performance are shown.     

基于DVD读取头的光学探头电路设计

随着工业精密测量对于精度和分辨率的要求越来越高,光学探头在工业精密测量中得到了广泛的应用。由于DVD读取头的聚焦误差信号FES(Focus Error Signal)即S曲线的一部分与失焦距离成线性关系,因此稍作改进就可以做光学探头,用来进行微小位移的测量[1]。文中给出了其电路设计,该电路分成两个部分,一个是LD功率自动控制电路,一个是FES获取电路。经过实验测试,利用该电路可以获得良好的S曲线,可实现对微器件(几何尺寸数毫米至数微米,精度参数多为微纳米数量级)的精确测量。该电路设计具有结构简单、抗干扰能力强等突出优点。     

Transverse superresolution and focal shift with rotational tunable phase mask

This paper reports the imaging characteristics of an optical system can be modified by our designed polarization pupil mask. The novel rotational symmetric polarization pupil mask design based on combination of half-wave and quarter-wave plates is introduced for realizing the focal shift and extending focal depth of an optical system and the procedure for designing is presented. Numerical results show when an appropriate rotational symmetric polarization pupil mask is used as an apodizer in the optical imaging system, it not only can effectively achieve the continuously focal shift in a small range and extend focal depth of the optimized system, but also can evidently increase the transverse resolution of the optimized system at the genuine focal plane.     

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%)。     

DYNAMIC CHARACTERISTICS OF STEPPED CANTILEVER BEAMS CONNECTED WITH A RIGID BODY

The object of this work is to analyze the dynamic characteristics of the portal frame which consists of two stepped beams including a thin plate and a torsional spring at the discontinuous point and a rigid body connecting each beam tip. This structure is available in a lot of cases that need higher stiffness and linear motion of the tip mass. For example, it might be used for an optical pick-up actuator, using piezoelectric materials, for the high area density CD, DVD or the next generation of optical memory devices, which require superrigidity and linear motion in focusing. The mathematical modelling and the derivation of the equation of motion are given for the cantilevers with identically paralleled and stepped beams. The equation of motion and the associated boundary and the continuous conditions are analytically obtained by using Hamilton's variational principle. The exact solutions are presented and compared with the results obtained by FEM Tool (IDEAS).