可诱导人眼自主调节的动态像差测量仪

研究了人眼在近视力状态下自动调节产生的动态像差。采用哈特曼-夏克(Hartmann-Shack,H-S)原理研制了一套可诱导人眼屈光调节,并能测量不同调节状态下人眼像差的测量仪。诱导原理为用视标在人眼近距离范围内移动以诱发人眼屈光调节,哈特曼-夏克传感器同时进行像差的测量,可以获得人眼调节时的视觉信息。与干涉仪测量同一像差板进行相比,像差仪的测量精度均方根(RMS)值为λ/50,重复性为λ/500,具有较好的测量精度和重复性。在测量的10人19只眼中,最大的诱发调节幅度为8.6D,一般可诱发调节幅度为3~8D之间,占总人数的84%。     

Wave-front curvature compensation of polarization phase-shifting digital holography

An on-axis polarization phase-shifting digital holographic microscope, based on a normal upright optical microscope, is constructed to quantitatively measure both the amplitude and phase distributions of specimen. The condenser lens and microscope objective employed in the object beam path enhance the illumination and magnification of the image, however, they induce additional phase aberration of the object wave. The physical formation of the phase aberration is theoretically analyzed, and a formula for the object wave front involving the phase aberration in the CCD plane is derived. The phase aberration can be eliminated in the reconstruction procedure by measuring a specimen-free hologram and then fitting the aberration phase with a least square ellipsoidal model to determine the parameters of the system. This phase aberration compensation procedure also reduces some of noises in the reconstructed phase of the specimen. The practicability of this method is demonstrated by a test experiment on microlenses.     

Statistical description of wave-front aberration in the human eye

The wave aberration of the human eye has been measured by means of a Hartmann-Shack wave-front sensor in a population of normal subjects. The set of data has been used to compute the phase distribution, the power spectrum, and the structure function for the average eye to analyze the statistics of the ocular aberration considered as a phase screen. The observed statistics fits the classical Kolmogorov model of a statistically homogeneous medium. These results can be of use in understanding the average effect of aberrations on the retinal image and can serve as a tool to analyze the consequences of ocular-aberration compensation by adaptive optics, customized ophtalmic elements, or refractive surgery.     

Closed-loop adaptive optics in the human eye

We have developed a prototype apparatus for real-time closed-loop measurement and correction of aberrations in the human eye. The apparatus uses infrared light to measure the wave-front aberration at 25 Hz with a Hartmann-Shack sensor. Defocus is removed by a motorized optometer, and higher-order aberrations are corrected by a membrane deformable mirror. The device was first tested with an artificial eye. Correction of static aberrations takes approximately five iterations, making the system capable of following aberration changes at 5 Hz. This capability allows one to track most of the aberration dynamics in the eye. Results in living eyes showed effective closed-loop correction of aberrations, with a residual uncorrected wave front of 0.1microm for a 4.3-mm pupil diameter. Retinal images of a point source in different subjects with and without adaptive correction of aberrations were estimated in real time. The results demonstrate real-time closed-loop correction of aberration in the living eye. An application of this device is as electro-optic "spectacles" to improve vision.     

超视力人眼模型的研究

超视力人眼模型对充分发掘人眼视力达到“鹰视”具有重要意义。用Zernike多项式描述角膜前表面，用渐变折射率描述晶状体的折射率分布，同时考虑人眼视轴和光轴的夹角对成像的影响，利用光学设计软件Zemax建立了人眼超视力模型。将Zernike条纹矢高面应用到人眼模型中，能有效改变视轴方向(即5°视场)的成像质量，提高点扩散函数（PSF）值。采用晶状体渐变折射率符合人眼的实际解剖结构，可有效减小人眼像差。通过分析人眼极限分辨能力和人眼模型波像差，得出当空间频率为60周期/度时，该模型对目标高频细节感知的调制度可达到0.55。     

阴影像与眼像差仪的几何光学原理

Howland像差仪是一种由正负柱透镜中间夹着格栅组成的系统。它通过检出人眼透过像差仪所视的变形格栅图中的偏移变形量,来获得对应的人眼的波像差信息。建立了该系统的等效光学成像模型,从格栅所成阴影像的概念出发,得到其成像公式,给出人眼波像差计算方法。     

Modal tomography of aberrations of the human eye

The work is devoted to the research and development of a new method of modal phase tomography for diagnostics of aberrations of the human eye. Implementation of the method is based on a series of eye aberration measurements taken at different angles to the optical axis by means of a wave-front sensor. The technique of restoration permits the contributions of different elements of the eye to the total aberrations to be separated. The results of numerical research and a model experiment are presented.     

低频位相误差新校正方法模拟研究

 就多程放大系统中产生的低频位相噪声，提出用位相补偿反射镜来进行补偿的静态校正方法。用随机位相屏模拟光学元件产生的低频位相噪声，建立光传输模拟模型，引入等效位相片的概念，将数个光学元件对位相的影响简化为等效位相片，在此基础上对位相补偿反射镜的校正原理进行阐述。进而对双程光路校正过程进行了模拟研究，得到了很好的校正效果。     

激光束低频位相误差叠加规律研究

 用随机位相屏模拟光学元件产生的低频位相误差，并用RMS位相梯度对低频位相误差进行统计量化，通过对激光束传输过程进行模拟，对低频位相误差的叠加规律有了新发现，并对位相误差叠加规律进行了修改，为位相校正提供了理论上的依据；通过对光束聚焦过程进行研究，得到了低频位相误差影响光束焦斑尺寸的初步规律；并在此基础上提出了一种光束质量控制的新方法。     

Information fusion method for ocular aberrations measurement based on subjective visual compensation

The human eye is an imperfect refractive system which not only has defocus and astigmatism, but also has spherical aberration, coma and anomalistic high-order aberrations, all of which have certain influence on the imaging quality of retina. What's worse, aberration is further enlarged as a result of mydriasis in dark field and weak light, thus making the vision performance of human eyes far below diffraction limitation. Further research revealed that human eye visual imaging is not only connected with refractive system, but also is closely related to the subjective judgment of human brain and the process of neural system. In order to overcome the deficiencies, wave-front aberration measurement method and system that has subjective visual compensation is proposed and conducted in combination with objective measurement, which ensures more accurate and realistic measuring results. The experimental data revealed that wave-front aberration obtained from subjective visual compensation measuring method is smaller than objective measurement, which is the result of subjects’ adaptive correction when watching sighting targets. In addition, when subjects are watching different sighting targets, the fluctuation value of wavefront aberration is small. Therefore, it is concluded that subjective visual compensation measuring method contributes to aberration measuring improvement and obtains results match with the realistic state by taking into consideration the actual condition of human eyes when watching targets. Hopefully, these discoveries will be of positive and beneficial value to the determination of human eye aberration treatment.     

A tomographic method for diagnosis of human eye aberrations

A new method using modal phase tomography for diagnosis of human eye aberration was elaborated and investigated. The method enabled the separation of the contributions from the individual elements of the eye into summary aberrations. The forms of the radiation wavefronts from several reference sources being formed on the retina of the eye as initial data for analysis were considered. Distortions of every element of the eye were represented as a Tsernike polynomial expansion. In this work, the theoretical basis of the method, numerical investigation and experimental modeling results confirming the efficiency of the method are presented.     

汉折射波片用于发散光束的偏振像差分析

本文利用光线追迹法,对双折射波片用于发散光束的偏振像差进行了分析,并以标准1/4波片为例,给出了小角入射时的近似处理方法.     

人工晶体倾斜与偏心对人眼视功能的影响

基于Hwey-Lan Liou人眼生理模型,采用光线追迹的方法,分析了相同孔径下具有不同球差的人工晶体(IOL)在眼内的倾斜和偏心对人眼视功能的影响.IOL在眼内无倾斜和偏心时,负球差IOL对人眼视功能的改善优于无球差IOL和传统的正球差IOL;当IOL在眼内倾斜,偏心程度一定时,负球差IOL球差值越大,其倾斜和偏心对人眼视功能的降低越明显;植入无球差IOL的眼的视功能受其倾斜和偏心的影响较小,在IOL偏心1.0 mm,倾斜10°已使人眼有明显视觉不适的情况下,仍能表现出良好的光学性能,对人眼视功能的改善不仅优于正球差IOL,而且优于负球差IOL.     

散射板干涉仪的统计光学原理

用近代光学方法,对散射板干涉仪的基本光路进行了严格分析.用傅里叶光学证明先散射后透射与先透射后散射两条光路传播光的等价性,给出存在波偈差时这两条光路的变化.而后用统计光学方法讨论了干涉条纹产生的机理以及干涉条纹对比度与两块散板透过率相关性之间的关系,建立了散射板干涉仪的干涉条纹公式.分析结果与实验现象相符合,并可以解释以往理论不能解释的现象.     

Simple method for simultaneous determination of the phase retardation and fast axis of a wave plate

A simple method for simultaneous determination of the phase retardation and fast axis of a wave plate is presented. In this method, double light path compare system is adopted to achieve better accuracy. In the main optical path, laser beam passes successively through a polarizer, a wave plate to be measured, an analyzer, and then is incident on a detector. In the reference optical path, another detector is used to monitor the fluctuation of the light source. With rotation of the wave plate, the maximum and minimum output light intensity, rotation angle of the wave plate are detected in the main light path; corresponding light intensity are simultaneously detected in the reference light path. Based on the light intensity and the rotation angle, the phase retardation and fast axis of the wave plate can be determined simultaneously. The main advantage of this method is its simplicity of apparatus, easy operation, low cost, and high accuracy. We believe that the method reported in this paper should be a useful approach to measure a wave plate without requiring any complex and expensive components.     

Visualization of phase conjugate ultrasound waves passed through inhomogeneous layer

Compensation of phase distortions of ultrasound beams by means of parametric phase conjugation is visualized. Quasi-plane and focused primary beams were distorted by a polymer aberration layer introduced between the primary wave source and the wave phase conjugator. It is demonstrated acousto-optically that, while the acoustic field is strongly irregular in the area between aberration layer and conjugator, the phase conjugate wave visibly reproduces the primary beams in the area between the layer and the primary wave source. The phenomenon is observed in supercritical mode of parametric amplification when intensity of phase conjugate wave is high enough for manifestations of acoustic nonlinearities in water.     

四区域法消除偏振棱镜缺陷对波片相位延迟测量的影响

在起偏器-待测波片-检偏器系统基础卜提出一种四区域测量波片相位延迟量的方法.调整待测波片和检偏器的方位角,获得相应的四组光强值,通过线性运算得到待测波片的相位延迟量,完全消除了起偏器和检偏器不完全消光带来的误差.由于测量系统中不存在标准波片或其他相位调制元件,允许测量波长仅受偏振棱镜和探测器的限制,因此四区域法可适用于很大波长范围内的波片测量.以λ/4波片为例,理论分析了测量系统利用四区域测量法后的仪器误差为σφ≤士3.49065×10-3rad(约0.2°),精度比原算法提高约1个数量级.实验验证了四区域法能有效提高系统精度.     

微机械薄膜变形镜校正性能及控制算法

通过对微机械薄膜变形镜影响函数矩阵的奇异值分解,构建了变形镜可以校正的像差模式空间,分析了变形镜对正交基模式的校正能力和校正范围,提出了一种变形镜闭环迭代控制算法。通过对影响函数矩阵低秩近似的方法滤除校正性能较差的基模式的影响,实现了对畸变像差的有选择校正。以人眼出射波前为对象进行实验,通过比较不同模式项数校正时的效果,确定了最优校正模式项数的范围,通过设置残差容限的方法,消除了人眼晃动和眨眼的影响。实验结果表明:控制算法能通过选择合适的校正项数,提高变形镜的校正性能,并获取到了高清晰度的人眼视网膜图像,为眼科疾病诊断和治疗提供了一种新的观察手段。     

在测量人眼像差中信息融合方法的应用

建立了基于Hartmann-Shack传感器的主客观人眼波前像差测量系统,该系统使用Hartmann-Shack传感器客观测量人眼像差,分别对模拟眼和活体人眼进行了像差测量.同时系统中加入了主观测量人眼像差的部分,该系统能够同时进行客观和主观的像差测量,实现了使用信息融合的方法对测量结果进行数据处理.并结合了客观测量和主观测量的优点,使用信息融合的方法使测量结果更加合理.     

A novel method of high resolution imaging through random perturbation wave front

A novel method is proposed for eliminating the effect of the traditional optical aberration on high resolution imaging by random perturbation wave front and digital image processing. A random phase mask, whose phase spectrum fluctuation is accordant with Kolmogorov distribution, is positioned near the aperture stop of optical system, making the optical aberration image become random perturbation image, that is, the intermediate image. The blind deconvolution algorithm based on maximum-likelihood estimation technique is used to restore the intermediate image acquired by a digital detector. The effects of optical aberrations and the noise on the restoration image are explored. To demonstrate the validity of the method proposed, the computer simulation and laboratory experiments are carried out for the imaging of the optical system with primary aberration. The results have shown that the present method is well suited for effectively improving the imaging quality of the optical system with certain aberration, thus making the optical system resolution close to or reach the diffraction-limit of the optical system.