The Calculation of the Wavefront Aberration Polynomial

This paper presents a method of generating the wavefront polynomial using a set of orthogonal polynomials that are particularly relevant to the ray fans used in optical design and evaluation. This method avoids the unsatisfactory aspects of conventional curve-fitting techniques that use collocation, osculation or least-squares to establish a polynomial in ascending powers of the radial pupil coordinate and the cosine of the pupil azimuth angle.     

全光路像差校正自适应光学系统中共模波前传感器标定方法研究

根据光波在介质中的传播规律,首先详细分析了全光路像差校正自适应光学系统的工作原理,然后对常规方法标定共模波前传感器后的系统校正残余误差作了分析,并从校正残余误差和操作的简易程度两个方面分析了常规方法标定共模波前传感器存在的缺点,最后针对全光路像差校正自适应光学系统的特点,提出了两种新的共模波前传感器标定方法,详细推导了两种方法标定共模波前传感器后全系统的校正残余误差.结果显示,两种方法标定共模波前传感器后,其校正残余误差只与常规方法标定共模波前传感器后系统的校正残余误差中的一种误差有关.     

Aberration Tolerances Based on the Line Spread Function

Abstract

Approximate formulae are obtained for the influence of aberration on the image of an incoherent line, by a method corresponding to that used by Maréchal for the image of a point. The best forms of correction in the presence of higher-order aberrations, and the best focal planes, may be easily determined using tables of coefficients that are provided. For the case of asymmetric aberrations, the image shift to the diffraction focus is also simply found. This, and the tolerance formulae, also apply to the gradient of intensity in the image of an edge.     

Aberration structure

The computer-aided design of complex electron-optical systems proceeds in several stages, including field calculation, aberration evaluation and exploration of the effects of parasitic aberrations caused by misalignment, for example. We recall that the geometry and excitation of each component of a complex sequence can be dissociated from the magnifications at which the component is operating and we show how this useful separation can be achieved for superimposed deflection and round lens fields.     

用于21单元H—S波前传感器的自适应光学波前信号处理机

需要处理的数据量大要求处理的速度快，是应用于Ｈ－Ｓ波前传感器的自适应光以前信号处理机的主要特点。本文完成了利用ＴＭＳ３２０Ｃ２５作为处理器，应用于２１单元Ｈ－Ｓ波前传感器的实时波前信号处理的研制。该系统完成对Ｈ－Ｓ波前传感器输出的高帧频图象信号的采集、处理、并计算出波前校正所需的控制信号，处理速度不低于２５０帧／秒。     

Wavefront reconstruction from its gradients

Wavefronts reconstructed from measured gradients are composed of a straightforward integration of the measured data, plus a correction term that disappears when there are no measurement errors. For regions of any shape, this term is a solution of Poisson's equation with Dirichlet conditions (V = 0 on the boundaries). We show that for rectangular regions, the correct solution is not a periodic one, but one expressed with Fourier cosine series. The correct solution has a lower variance than the periodic Fourier transform solution. Similar formulas exist for a circular region with obscuration. We present a near-optimal solution that is much faster than fast-Fourier-transform methods. By use of diagonal multigrid methods, a single iteration brings the correction term to within a standard deviation of 0.08, two iterations, to within 0.0064, etc.     

Aberration and the Strehl ratio

An exact expression is derived for the Strehl ratio as a function of the minimum root-mean-square aberration value that may produce it. The result is applicable to any aperture and is shown to imply a similar expression for the Strehl ratio as a function of the minimum amplitude range of the aberration.     

A New Total Aberration Formula

A total aberration formula is defined as one which gives total ray or optical path aberration from finite raytrace data. Some known expressions of this kind are reviewed and a new expression for optical path aberration along skew rays is developed; this expression gives the maximum possible conservation of numerical precision.     

弱光波前探测用的阵列探测器

本文讨论了自适应光学系统中弱光波前探测器对阵列探测器的要求,指出弱光波前探测器中使用的阵列探测器必须是带像增强器的电荷耦合器件(ICCD),并对ICCD的参数设计及其极限探测能力进行了分析。     

Aberration effects in two-beam laser interferometers

In displacement measurements by two-beam interferometers, the wavefront curvature of a laser beam causes a systematic increase of the fringe period. This increase depends on beam collimation: It is null for a plane wave and proportional to the squared divergence of the beam. With interfering beams not perfectly recombined, an additional fringe-period error is caused, with the effect of counteracting and also of compensating for and prevailing over the usual error. We describe this hitherto unsuspected effect and give a correction equation.     

Spherical Aberration of Monocentric Doublet Lenses

A computer programme has been compiled which, for given pairs of refractive indices, sets up a monocentric doublet lens of unit focal length having zero primary spherical aberration, and traces a marginal ray through the system at a relative aperture of f/8. The results, presented graphically, show the pairs of refraction index values that give minimum higher-order spherical aberration.     

基于相位差法的波前检测技术

基于相位差法的波前检测技术,主要是利用在焦面和离焦位置上同时采集的一对图像,对光瞳上的波前相位分布进行恢复,同时也可以对目标进行恢复。与哈特曼波前传感器和剪切干涉仪等波前检测技术相比,相位差法具有光路简单、易于实现的特点,同时可以采用扩展目标作为参考源,主要适用于对实时性要求不高的领域。在计算机模拟大气湍流和成像系统的基础上,我们使用有限内存拟牛顿法对波前相位和目标进行了恢复。模拟研究结果表明,相位差法可以较准确的恢复出波前相位,并且最优化的离焦波面差为一个波长。     

Wavefront reconstruction by spatial-phase-shift imaging interferometry

Common-path imaging interferometers offer some advantages over other interferometers, such as insensitivity to vibrations and the ability to be attached to any optical system to analyze an imaged wavefront. We introduce the spatial-phase-shift imaging interferometry technique for surface measurements and wavefront analysis in which different parts of the wavefront undergo certain manipulations in a certain plane along the optical axis. These manipulations replace the reference-beam phase shifting of existing interferometry methods. We present the mathematical algorithm for reconstructing the wavefront from the interference patterns and detail the optical considerations for implementing the optical system. We implemented the spatial phase shift into a working system and used it to measure a variety of objects. Measurement results and comparison with other measurement methods indicate that this approach improves measurement accuracy with respect to existing quantitative phase-measurement methods.     

Aberration compensation in a grating interferometer

The transfer function of a grating interferometer with aberrated gratings is discussed. A geometrical configuration is developed that minimizes the aberrations of the output fringes in the interferometer, which is constructed with three hyperbolic gratings. Theoretical and experimental investigations show that it is possible to compensate for first-order aberrations of the interferometer and obtain straight output fringes if a suitable geometric configuration is used for both the recording of the grating components and the interferometer itself.     

激光光学系统的球差

依据斯特列尔判断，采用解线性方程组的方法讨论了高斯光束初级和高级球差的最佳校正形式，并以表格方式给出了最佳校正形式。讨论了按照均匀光波最佳校正形式对高斯光束进行像差平衡时的中心点亮度变化，研究表明，在工程实际中，采用普通光学系统的像差平衡理论对激光光学系统进行设计是完全可行的。     

Aberration in nonlinear acoustic wave propagation

Theory and simulations are presented indicating that imaging at the second-harmonic frequency does not solve the problem of ultrasonic wave aberration. The nonlinearity of acoustic wave propagation in biological tissue is routinely exploited in medical imaging because the improved contrast resolution leads to better image quality in many applications. The major sources of acoustic noise in ultrasound images are aberration and multiple reflections between the transducer and tissue structures (reverberations), both of which are the result of spatial variations in the acoustic properties of the tissue. These variations mainly occur close to the body surface, i.e., the body wall. As a result, the nonlinearly generated, second harmonic is believed to alleviate both reverberation and aberration because it is assumed that the second harmonic is mainly generated after the body wall. However, in the case of aberration, the second harmonic is generated by an aberrated source. Thus the second harmonic experiences considerable aberration at all depths, originating from this source. The results in this paper show that the second harmonic experiences similar aberration as its generating source, the first harmonic.