Influence of Amplitude-only Filters in Optical Systems with Residual Longitudinal Chromatic Aberration

Abstract

The transverse and axial polychromatic responses of optical systems with residual chromatic aberration and an achromatic correction are studied. The influence of amplitude-only filters that produce apodization or hyper-resolution in a transverse section is shown. Filters that modify the responses along the axis are also shown. The differences between the responses of the aberration-free system with a filter and the aberrant systems with the same filter are compared.     

Tunable Optical Sectioning in Confocal Microscopy by use of Symmetrical Defocusing and Apodization

We present two novel optical methods to achieve a significative improvement in the optical-sectioning capacity of confocal scanning microscopes. The techniques, whose real power is the simplicity with which they can be implemented, consist of a suitable combination of symmetrical defocusing with two different manners of apodizing both parts of the confocal architecture. It is shown that the proposed techniques are useful in both the bright-field and the fluorescence modes and for reflection and transmission geometries.     

The Diffraction Theory of the Aberrations of Stigmatic Orthomorphic Optical or Electron Optical Systems Containing Toric Lenses or Quadrupoles

The diffraction theory of the aberrations of optical systems with an axis of rotational symmetry is now thoroughly established, and the extension to kindred electron optical systems is straightforward. In electron optics, however, certain types of systems containing quadrupoles are of importance, and such systems suffer from aberrations which affect only very oblique rays in axially symmetrical systems. The distortions of the wave surface which correspond to these new aberrations are listed in the present note, and Nijboer's expressions for the consequent disturbances in the image plane of a rotationally symmetrical system are supplemented accordingly. Only the special case—which is, nevertheless, an important one—of stigmatic systems, producing an image free of first-order distortion?, is considered. The analysis is applicable to electron optical orthogonal systems containing quadrupoles and optical systems containing parallel toric lenses alike.     

Optimization of a Bimorph Drive in Optical Measuring Systems with Feedback

The problem is considered of improving a bimorph drive used in optical measuring systems with feedback. In particular, a solution is given to the problem of determining the optimal parameters of a bimorph drive in a system. Experimental data are presented. Advantages and deficiencies of the drive are considered.     

Aberrations in Optical ProcessorsPhase Errors in the Transformed Plane

Compensations of phase errors on the Fourier transformed plane in coherent optical processors are studied by introducing suitable aberrations in the image reconstructing lens. The contributions of each type of aberration to those errors are analysed for the cases of convolution and optical correlation. Tolerance limits are obtained for the transforming lens and calculated for a typical case.     

Measurement of Residual Stresses with Optical Techniques

Abstract:  The goal of this work was the development of other experimental techniques to measure residual stresses, as an alternative to the hole-drilling method with strain gauges. The proposed experimental techniques are based on the use of Moiré interferometry and in-plane electronic speckle pattern interferometry (ESPI). Both are field techniques allowing the assessment of in-plane displacements without contact and high resolution. Grating replication techniques were developed to record high-quality diffraction gratings onto the specimen's surfaces. An optical set-up of laser interferometry was developed to generate the master grating (virtual). An in-plane ESPI set-up was also designed and implemented to measure displacements in one direction. The stress relaxation was promoted by the blind hole-drilling and the obtained fringe patterns (Moiré and speckle) were video-recorded. Image processing techniques were applied to assess the in-plane strain field. A finite-element code ( ansys ®) was used to simulate the stress relaxation process, whose values were compared with the experimental data, and to calculate the hole-drilling calibration constants.     

On the Efficiency of Infrared Filters in Optical Cryostats

In an optical cryostat, the sample temperature is limited by the 300 K thermal radiation transmitted through the observation windows. As discussed in this paper, the corresponding heat load should be brought much below the ??W level by using suitable cold IR filters. However, there are situations where one wants to directly check the absence of IR heating by running the same experiment with the cold observation windows either open or totally blocked. We describe a particular example which is the study of helium condensation in a silica aerogel. On this aim, we developed a simple and compact magnetic system able to move metallic shutters inside our optical cryostat. This allows us to set an upper bound of 1 ??W for the effect of 300 K thermal radiation on our sample. We discuss the relevance of this result to the operation of optical dilution refrigerators.     

Axial and Extra-axial Responses in Aberrated Optical Systems with Apodizers. Optimization of the Strehl Ratio

Abstract

The effect of non-uniform transmission filters on the axial and extra-axial responses of aberrated optical systems is studied. The axial Strehl ratio (SR) is increased by varying the filter transmission function and the extra-axial SR by shifting the filter position along the axis of the optical system. It is shown that a filter which optimizes the axial SR can also improve the extra-axial SR. There are some positions of the filter for which the total results are improved. These positions are explained from the lack of radial symmetry of the wave aberration. The filters which improve the SR are also studied in terms of energy transmission.     

A Lattice-Theoretical Framework for Annular Filters in Morphological Image Processing

We study the idempotence of operators of the form ?∨id∧δ (where ?≤δ and both ? and δ are increasing) on a modular lattice ?, in relation to the idempotence of the operators ?∨id and id∧δ. We consider also the conditions under which ?∨id∧δ is the composition of ?∨id and id∧δ. The case where δ is a dilation and ? an erosion is of special interest. When ? is a complete lattice on which Minkowski operations can be defined, we obtain very precise conditions for the idempotence of these operators. Here id∧δ is called an annular opening, ?∨id is called an annular closing, and ?∨id∧δ is called an annular filter. Our theory can be applied to the design of idempotent morphological filters removing isolated spots in digital pictures.     

光学测量系统信噪比优化方法研究

在光学测量中常常受低信噪比问题的影响,导致测量结果的不确定度增大。近红外波段双向反射分布函数（BRDF）的测量由于红外信号强度偏弱,易受环境干扰,面临的低信噪比问题尤其突出。光学测量系统的信噪比问题一般产生自探测系统,对于红外测量系统来说,经常使用斩波器、锁相放大器进行弱信号测量,但同时也引入了噪声问题。因此,本文针对近红外波段BRDF测量信噪比问题,从探测器、斩波器、锁相放大器三部分着手,分析噪声来源并针对性地提出抑制方法与优化措施,以提升信号信噪比。优化后的测量系统较优化前抗噪声能力提高,可重复性由优化前的2.1%提升到1.6%。     

复合优化理论在不共轴光学系统CAD中的应用

讨论在不同轴光学系统的计算机辅助设计中如何用“复合优化”理论，主要是如何模拟评价函数，又怎样进行适应法处理，“复合优化”有何特色，并列举实例说明。     

Theoretical Studies of Synthetic Imaging Properties of Optical Arrays in Third-order Aberrations

Abstract

The third-order theory of synthetic images of three-dimensional optical arrays is presented using Lie algebraic methods and coordinate transformation. The generally applicable advantage of the third-order theory is shown, which includes the main results of first-order theory and the modification introduced by non-paraxial misalignment; it is consistent with diffraction theory and so overcomes the main difficulties of the first-order theory.     

Reversible Image Coding by the Use of Optical Fibres

We examine the possibility of using optical fibres to reversibly modify a picture in order to encode and to decode it. The decoder is to receive the coded picture in the form of a photographic transparency and the decoding process requires possession of the proper apparatus in addition to the code key. The new feature of the proposed devices lies in the greatly enhanced degree of coding security. We discuss two different methods of constructing the necessary device, and we estimate theoretically the expected degree of security for each.     

Analysis of Inhomogeneous Optical Systems by the Use of Ray Tracing. II. Three-dimensional Systems with Symmetry

We describe a new approach to the index reconstruction of three-dimensional optical systems with rotational symmetry, which is based on sampling ray paths that lie in the sagittal plane. Since the observed rays are distorted by the optical system itself, they cannot be used directly for index reconstruction. We present an iterative procedure to compute the true ray paths and then to find the index distribution. The utility of the method is verified on the model problem.     

基于残差平方和的光流场正则化方法

光流场的不连续性是光流场准确估计中最为重要的研究内容。提出利用最小二乘法和加权最小二乘法算法中残差平方和来对光流场进行正则化,以减少计算窗口中含有多种模式运动的概率,较好地解决了光流场的不连续性,从而使该算法具有鲁棒性。计算结果表明,该算法具有简单实用和运算速度快的特点。     

Wavelength Dependence of Optical Bistability in Molecular-beam-deposited ZnSe Interference Filters

Abstract

Complete ZnSe interference filters exhibiting optical bistability have been fabricated using ultrahigh-vacuum molecular-beam techniques. The wavelength dependence of the critical switching power was measured at five wavelengths between 521 and 676 nm for a filter with two-period ZnSe/BaF₂ multilayer reflectors and an initial assessment has been made of their long-term operational stability.     

Investigations of the Influence of Hologram Aberrations on the Light Intensity Distribution in the Image Plane

The aim in this paper is to analyse, for the examples chosen, the influence of particular aberrations of the point-object hologram on the light intensity distribution in the plane which is assumed to be the image plane. The numerical method used for calculating the light intensity at any image point is that presented in an earlier paper. The calculations have been carried out for three cases of holographic imaging. The recording and reconstruction geometry has been chosen so that it was possible to examine the influence of the particular aberration on the image quality. The calculated energy distribution in the aberration spots is consistent with those resulting from using third-order aberration theory as well as from ‘ray-tracing’ calculations.