Conjugate Image Plane Correlator with Holographic Disk Memory

A conjugate image plane correlator with holographic disk memory is proposed. Optical correlation between conjugate images reconstructed from a holographic disk and an input image on liquid-crystal television is executed with the rotation of the disk. Regardless of Fourier hologram recording with the pseudorandom diffuser, it is found possible to take out the diffuser from the original hologram recording scheme using an image reconstruction process and to get correlation signals between input and reconstructed conjugate images in the output plane of a two-lens imaging system. Generation of conjugate replicas with high contrast causes exact matching with an input image which results in high recognition performance for autocorrelation signals. The transfer function of an optical system can be controlled by adjustment of either hologram size or hologram area illuminated with a laser beam. Hence, the output intensity distribution can be adjusted by selecting a proper pupil function and the size of an output pupil defined by the input pupil size and the optical system magnification factor. The real-time character recognition by optical parallel high-speed processing for two dimensional images with position normalization is demonstrated.     

Generalized phase diversity for wave-front sensing

Phase diversity is a phase-retrieval algorithm that uses a pair of intensity images taken symmetrically about the wave front to be determined. If these images are taken about the system input pupil this is equivalent to a curvature-sensing algorithm. Traditionally a defocus aberration kernel is used to produce the phase-diverse data. We present a generalization of this method to allow the use of other functions as the diversity kernel. We discuss the necessary and sufficient conditions that such a function must satisfy for use in a null wave-front sensor. Computer simulations were used to validate these results.     

Simple method to measure the visual axis of the human eye

We propose a simple method to measure the angle "α" that the visual axis (VA) makes with the optical axis of the human eye. In this method, we capture the images of the pupil from three different angles, one along the VA and the other two along angles that are symmetrical with respect to the VA. These views of the pupil are captured simultaneously by a camera in a single photograph using a pair of plane mirrors. Assuming a model eye and with the help of finite ray tracing, we compute the value of α from the measured diameters of the three images of the pupil. Having a simple means to measure the value of α can be useful for optical modeling and analysis of the human eye. Measurement of the VA may also be useful in monitoring progressive myopia.     

Restoration of solar and star images with phase diversity-based blind deconvolution

The images recorded by a ground-based telescope are often degraded by atmospheric turbulence and the aberration of the optical system. Phase diversity-based blind deconvolution is an effective post-processing method that can be used to overcome the turbulence-induced degradation. The method uses an ensemble of short-exposure images obtained imultaneously from multiple cameras to jointly estimate the object and the wavefront distribution on pupil. Based on signal estimation theory and optimization theory, we derive the cost function and solve the large-scale optimization problem using a limited memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) method. We apply the method to the urbulence degraded images generated with computer, the solar images acquired with the swedish vacuum solar telescope (SVST, 0.475m) in La Paima and the star images collected with 1.2-m telescope in Yunnan Observatory. In order to avoid edge effect in the restoration of the solar images, a modified Hanning apodized window is adopted.The star image till can be estored when the defocus distance is measured inaccurately. The restored results demonstrate that the method is efficient for removing the effect of turbulence and reconstructing the point-like or extended objects.     

A new image processing method for evaluating the pupillary responses in a HMD-type eye-tracking device

In this paper, a new image processing method for evaluating the pupillary responses is described. This system is based on an eye-tracking system, using eye tracking and pattern recognition techniques with appropriate hardware and software. This pupillary response evaluation system includes a head-mounted display and a pinhole CCD camera. When the subject uses the head-mounted display to browse the screen of a computer, the CCD camera catches images of the subject's eye and transmits it to the computer. The program in the computer calculates the location and size of the pupil in the images. The pupil area calculation weighting function, visual fatigue detection, concentration detection, and eye/HMD slide compensation are included in the system. This allows the system to detect the pupil under different conditions. This system will know if anyone is using the system, then it evaluates the operating conditions of the subject, if the adjustment is correct, and guides the operator in using the system. The experimental results verified that this image system provides an economical and effective method for evaluating pupillary responses.     

Apodization to produce a monotonically-decreasing,radially symmetrical,point-spread function

A class of apodized pupil functions is derived which have the property of producing a point-spread function which decreases monotonically with increasing radius. This in turn produces coherent line and edge images which are free of the usual subsidiary diffraction maxima and minima. An example of one of these functions is given, together with the point, coherent line and coherent edge images produced.     

Determining the complex point-spread function of a scanning differential heterodyne microscope

For a scanning differential heterodyne microscope, the two-dimensional point spread function and the pupil function are determined from experimental measurements of the intensity distribution of a probing beam. The phase components of these functions were restored from the measured distributions using the Gerchberg-Saxton algorithm. Based on the two-dimensional pupil function, the three-dimensional point-spread function is determined in the scalar approximation using the Debye integral. The aberration function of the microscope is analyzed from the viewpoint of the composition of aberrations and method of their balancing. The focusing adjustment criterion of the microscope for an object under study by the phase response from the test structure is considered.     

Use of a microelectromechanical mirror for adaptive optics in the human eye

Ophthalmic instrumentation equipped with adaptive optics offers the possibility of rapid and automated correction of the eye's optics for improving vision and for improving images of the retina. One factor that limits the widespread implementation of adaptive optics is the cost of the wave-front corrector, such as a deformable mirror. In addition, the large apertures of these elements require high pupil magnification, and hence the systems tend to be physically large. We present what are believed to be the first closed-loop results when a compact, low-cost, surface micromachined, microelectromechanical mirror is used in a vision adaptive-optics system. The correction performance of the mirror is shown to be comparable to that of a Xinetics mirror for a 4.6-mm pupil size. Furthermore, for a pupil diameter of 6.0-mm, the residual rms error is reduced from 0.36 to 0.12 microm and individual photoreceptors are resolved at a pupil eccentricity of 1 degrees from the fovea.     

瞳孔检测仪的研究及其光学系统设计

研究了一种双眼瞳孔检测仪,进行了光学系统的设计和理论计算.采用低照度CCD摄像机摄取在近红外和可见光照明情况下的瞳孔像,利用形态学等算法处理图像,可对图像进行直径精确检测和动态分析.实验表明,该仪器在0~200 lux照度级下的测量精度可达0.01 mm,完全可以满足眼科手术的精度要求.     

Golay6结构复杂光瞳成像研究

Golay6为非冗余的复杂光瞳结构,导出Golay6结构复杂光瞳的光瞳函数解析式和点扩散函数的解析式,在此基上用Matlab软件模拟了调制传递函数图像,并对目标图像进行模拟成像。针对所成像对比度下降问题,在不含噪声和含噪声情况下分别进行了讨论,利用分数阶微分算子对模拟所得图像进行图像增强,结果表明经分数阶微分算子空域增...     

Binocular adaptive optics vision analyzer with full control over the complex pupil functions

We present a binocular adaptive optics vision analyzer fully capable of controlling both amplitude and phase of the two complex pupil functions in each eye of the subject. A special feature of the instrument is its comparatively simple setup. A single reflective liquid crystal on silicon spatial light modulator working in pure phase modulation generates the phase profiles for both pupils simultaneously. In addition, another liquid crystal spatial light modulator working in transmission operates in pure intensity modulation to produce a large variety of pupil masks for each eye. Subjects perform visual tasks through any predefined variations of the complex pupil function for both eyes. As an example of the system efficiency, we recorded images of the stimuli through the system as they were projected at the subject's retina. This instrument proves to be extremely versatile for designing and testing novel ophthalmic elements and simulating visual outcomes, as well as for further research of binocular vision.     

消色差相位型超分辨光瞳滤波器的设计研究

提出并设计了一种消色差的相位型超分辨光瞳滤波器。详细分析了滤波器的设计参数对成像系统的光斑压缩比和斯特雷尔比影响。分别以方解石晶体和石英玻璃材料为例进行了设计,当光斑压缩比为0.83时,得到两种材料的消色差超分辨光瞳滤波器,可以分别在380～555nm和300～600nm的波长范围内实现消色差,同时可以有较高的斯特雷尔比。     

Optical transfer function analysis of circular-pupil wavefront coding systems with separable phase masks

This paper proposes a simple method to achieve the optical transfer function of a circular pupil wavefront coding system with a separable phase mask in Cartesian coordinates.Based on the stationary phase method,the optical transfer function of the circular pupil system can be easily obtained from the optical transfer function of the rectangular pupil system by modifying the cut-off frequency and the on-axial modulation transfer function.Finally,a system with a cubic phase mask is used as an example to illustrate the way to achieve the optical transfer function of the circular pupil system from the rectangular pupil system.     

Double-pass imaging polarimetry in the human eye

A Mueller-matrix imaging polarimeter was developed to measure spatially resolved polarization properties in the living human eye. The apparatus is a double-pass setup that incorporates two liquid-crystal variable retarders and a slow-scan CCD camera in the recording stage. Series of 16 images for the combinations of independent polarization states in the first and second passages were recorded for two experimental conditions: with the camera conjugated either with the retina or with the eye's pupil plane. Spatially resolved collections of Mueller matrices and the degree of polarization were calculated from those images for both retinal and pupil planes.     

Apodization to produce a monotonically-decreasing,coherent line-spread function

A class of apodized pupil functions is derived, which have the property of producing a monotonically decreasing, coherent line-spread function. A simple example of such a function is given together with the line-spread function so produced.     

Focal field computation of an arbitrarily polarized beam using fast Fourier transforms

In this work the vectorial diffraction theory of Richards and Wolf is extended to compute the focal field components of an arbitrarily polarized beam using fast Fourier transform (FFT) operations. Here the arbitrarily polarized pupil function is written as the vector sum of two mutually perpendicularly polarized pupil functions. The FFT based focal field expressions are particularly useful to compute the focal field components of pupil functions without a simple analytical form. We have then applied these expressions to simulate the effects of Zernike mode aberrations on the point spread functions of a number of important cylindrical-vector beam profiles such as radially and azimuthally polarized and helical light beams.     

双Toraldo光瞳的共焦系统

Toraldo光瞳是超分辨中研究最多的光瞳之一.不过，由于实际中在制作精确度以及制造效率上的限制，它的应用受到了很大程度的制约.提出了双Toraldo光瞳的共焦系统，它能够用两个相对容易制作的Toraldo光瞳实现多区复杂Toraldo光瞳的功能. 关键词： 超分辨 Toraldo光瞳 共焦成像     

A new data processing and calibration method for an eye-tracking device pronunciation system

In this paper, a new data processing and calibration method for a pronunciation system of an eye-tracking device is described. The eye-tracking device was created using both head mounted display (HMD) technology and remote operation capabilities. A pattern recognition computer program was used to distinguish the pupil position and calculate its coordinates.This system can be adapted to provide a digital speech function. A new method for processing the image of the eye in the PC-based system was also developed. With one video CCD camera and frame grabber analyzing a series of human pupil images while the subject is gazing at the screen, an auto-calibration algorithm is used to obtain the direction of the eye gaze in real time. The computers provide the speech sound according to the location where the eye gazes exceed 0.5 s. The availability of multipurpose in this eye-tracking system with very simple equipment will be reconfirmed for future advanced research.     

一种胶片式的静态光学目标模拟器

光学成像敏感器是卫星姿态控制分系统的重要组成部分，用于月面景象的获取，可为月面着陆器完成障碍识别、路径规划和安全区域选取等功能提供图像信息来源。为实现光学成像敏感器装星后设备功能和性能的检测，需要一种可在室内为光学成像敏感器提供月面场景信息的光学仪器。设计和研制了一种胶片式的静态光学目标模拟器，该目标模拟器以胶片作为图像源，通过积分球均匀照明系统将胶片照亮，并经由光学镜头将胶片图像投射至无穷远处，从而供光学成像敏感器接收。设计完成的静态光学目标模拟器视场≥30°×30°，入瞳直径Φ5 mm，入瞳距离为41 mm，镜头焦距44.78 mm，图像像素分辨率≤1 024×1 024，各项指标均达到了光学成像敏感器装星后光闭路试验的要求。     

High resolution optical image restoration for ground-based large telescope using phase diversity speckle

Phase diversity speckle (PDS) is an image restoration technique which is based on the idea of phase diversity (PD). It uses multi-frame short-exposure image sequence to calculate their corresponding wave-front information. Each image pair consists of two images collected by two cameras at the same time with one in focus and the other with known defocus value. Multi-frame processing can significantly improve the target signal to noise ratio, and decrease noise influence. In this paper, based on the principle of pupil Fourier imaging, by adjusting the pupil size, we get different scales of the optical point spread function (PSF). Also, we analysis different camera noise distribution channels, location differences and other factors to optimize the objective evaluation function, and this can reduce the computational complexity and improve the processing speed of image restoration. In the indoor environment, we build optical platform, and use multi-frame phase diversity speckle to make experiment under different turbulence conditions. The experimental results show that the image restoration effect of the proposed method is close to the diffraction limit.