共查询到20条相似文献,搜索用时 10 毫秒
1.
In this paper, two-dimensional real time method of measuring the complex degree of spatial coherence of a laser light field is presented. Far-field interferogram is generated by a two-dimensional mask with non-redundant multiple apertures in the focal plane of the lens. The Fourier spectrum of the interferogram is analyzed in the term of classes of aperture pairs. Through using heights of the peaks in the magnitude spectrum, as well as intensities in the apertures, the modulus of the complex degree of spatial coherence was determined. The available experimental data of Young interferometry, confirmed the graphs obtained with the above methods. 相似文献
2.
A low-coherence reflectometer based on a conventional Michelson interferometer and a novel silicon detector chip with a two-dimensional array of pixels that allows parallel heterodyne detection is presented. We demonstrate acquisition of three-dimensional images with more than 100,000 voxels per scan at a sensitivity of -58 dB and a rate of 6 Hz. 相似文献
3.
A deformable membrane mirror is often used in closed loop adaptive optics systems to correct for aberrations and improve image quality. In certain applications, the correction of only one type of aberration is sufficient, the calibration procedure of the mirror can be simplified and the control scheme can be reduced to a fast feed forward system. For these cases we developed a procedure that is easy to implement, accurate and delivers a large correction range. An application example is the writing and readout of three-dimensional optical memory. Here the spherical aberration component is dominant and can be inferred from the focussing depth. We describe the principle of the new calibration and feed forward control scheme and give experimental results. 相似文献
4.
We present a practical adaptive optics system based on feedback interferometry. The system consists a polarizing radial-sheared Sagnac interferometer incorporating a multi-segmented mirror for wavefront correction. Correction of atmospheric aberration is demonstrated. 相似文献
5.
A number of years ago, Horn and Weinstein introduced a novel nonperturbative method, the t-expansion, for calculating ground-state expectation values for Hamiltonian systems. Recently Šamaj et al. have generalized the t-expansion technique and the related connected moments expansion to a more general canonical sequence. In the present work we have expounded upon this work and have applied this to the two-dimensional square anisotropic XXZ Heisenberg model. 相似文献
6.
For microscopic interference setups like an arrangement for in-line holographic microscopy a partially coherent illumination with volumes of coherence in the micrometer scale is sufficient and helpful. For the sensitive measurement of the area of spatial coherence, we use a 125 × 125 nanohole array with aperture diameters of 530 nm and periodic distances of 4 μm. In contrast to Young's double pinhole, multiple beams interfere with each other and a peak intensity enhancement by more than a factor of 1000 can be reached. From the diameter of interference spots, which are located in the Talbot planes, we determine the diameter of the area of spatial coherence in the range of 5–50 μm. Limitations of this technique are given by the numerical aperture of the used imaging lens (100×/0.75) as well as the periodic distance of the apertures within the array. 相似文献
7.
Timing errors in the transmitting and receiving electronic channels of an imaging system can generate different transmission and reception phase-aberration profiles. To decide if these two profiles need to be measured separately, an overlapping-subaperture algorithm has been proposed in a previous paper to measure the difference between timing errors in transmitting and receiving channels connected to each element in a two-dimensional array. This algorithm has been used to calibrate a custom built imaging system with a curved linear two-dimensional array, and the results are presented in this paper. The experimental results have demonstrated that the overlapping-subaperture algorithm is capable of calibrating the timing-error-difference profile of this imaging system with a standard deviation of only a few nanoseconds. Experimental results have also shown that the time-error-difference profile of this imaging system is smaller than one tenth of a wavelength and there is no need to measure the transmission and reception phase-aberration profiles separately. The derived average phase-aberration profile using the near-field signal-redundancy algorithm can be used to correct phase aberrations for both transmission and reception. 相似文献
8.
B. G. Podlaskin 《Technical Physics》2007,52(5):672-675
The concept of temporal noise spatial filtering when the image is represented in the Walsh-Hadamard basis and the signal is integrated directly on a photodetector is validated. Results are provided which prove that the rule of ordering the rows and columns of the matrix of the original transformation influences the localization and concentration of noise over the image field. 相似文献
9.
This paper presents a technique that distortion aberrations of an optical imaging system can be reduced by using spherical lenses accompanying a microlens array. This technique is implemented by putting a microlens array on the intermediate image plane in the imaging system. Our experimental result confirmed that distortion aberrations can be obviously reduced after applying our proposed techniques. 相似文献
10.
共形整流罩像差特性分析及校正方法 总被引:2,自引:1,他引:2
共形结构不仅具有良好的空气动力学性能,且不存在由于表面不连续造成的热梯度等问题,因而采用该结构的导弹整流罩更有利于导弹系统作战性能的提高。但共形结构中采用的非球面罩曲面使整流罩表现出许多不同于球形结构的动态特性,这给导引头中光学系统的设计带来很多困难。在分析共形结构一阶特性的基础上,利用矢量像差理论详细分析该结构中初级像差产生的原因及特点,并提出通过控制元件的倾斜和偏心来平衡所有观察视场中像差的方法。软件分析结果表明:加入倾斜偏心元件后可适当放大小观察视场中的像差,共形整流罩在各观察视场中具有较为稳定的像差特性,有效地改善了该结构的成像质量。 相似文献
11.
We show that aberration corrections can be made in any arbitrary linear imaging system provided the aberrations are well characterized and at least one of these aberrations can be independently varied in a well-controlled manner. We derive a generalization of the Schr?dinger equation for wave propagation in aberration space assuming forward scattering. Transport equations in aberration space are derived. A general iterative algorithm which can retrieve the phase, and is robust in the presence of noise, is also derived. This is demonstrated using simulated data pertinent to electron microscopy, from a series of images with differing spherical aberration. 相似文献
12.
We discuss three methods to correct spherical aberration for a point to point imaging system. First, results obtained using
Fermat’s principle and the ray tracing method are described briefly. Next, we obtain solutions using Lie algebraic techniques.
Even though one cannot always obtain analytical results using this method, it is often more powerful than the first method.
The result obtained with this approach is compared and found to agree with the exact result of the first method. 相似文献
13.
Micron-scale-integrated optical gyroscopes based on the Sagnac effect have a broad array of potential applications in navigation and inertial motion sensing due to the benefit of on-chip integration and potential sensitivities exceeding micro-electromechanical gyroscopes. Here, we analyze the Sagnac effect in a two-dimensional array of evanescently coupled optical microring resonators. We show that the sensitivity to inertial rotations greatly exceeds that of a single resonator with equal enclosed area. Moreover, a comparison between two-dimensional arrays and Sagnac gyroscopes consisting of one-dimensional distributed microresonators arrays of equal footprint shows that the sensitivity to rotations of the two-dimensional array exceeds that of the one-dimensional structures by as much as several orders of magnitude for smaller arrays. 相似文献
14.
二维空间紫外LED阵列实现单光斑辐照固化系统的设计 总被引:2,自引:0,他引:2
新型大功率紫外LED具有电光转化效率高、光谱纯度高和体积小等优点,但单管LED功率仍很难满足光固化的要求,针对单光斑辐照要求,提出采用空间阵列UV-LED排布实现能量累加的方案。该方案通过单管LED聚光系统与集成阵列系统综合设计实现了各单元单光斑辐照度在辐照面上的合成,最终得到的光斑辐照度分布均匀、尺寸合理,阵列系统后工作距离长,完全满足现场应用的具体指标要求。通过外围电子线路控制阵列LED的电流强度及通断状态可实现光斑辐照度在(1000~1800) mW/cm2可调,光斑尺寸为1cm2,后工作距离为10cm。 相似文献
15.
Phase aberration correction in medical ultrasound using speckle brightness as a quality factor 总被引:1,自引:0,他引:1
Medical ultrasonic images are degraded by tissues with inhomogeneous acoustic velocities. The resulting phase aberration raises the off-peak response of the imaging system's point spread function (PSF), decreasing dynamic range. In extreme cases, multiple images of a single target are displayed. Phase aberration may become a limiting factor to image quality as ultrasonic frequency and aperture size are increased in order to improve spatial resolution. A method is proposed to correct for unknown phase aberration, which uses speckle brightness as a quality factor. The phase delays of a phased array transducer are modified, element by element, to maximize mean speckle brightness in a region of interest. The technique proposed is analogous to the correction technique used by Muller and Buffington [J. Opt. Soc. Am. 64 (9), 1200-1209 (1974)] to adaptively focus incoherent optical telescopes. The method is demonstrated using a computer model with several different simulated aberration profiles. With this model, mean speckle brightness is calculated using the two-dimensional PSF. Experiments have also been conducted in which speckle brightness is shown to increase as the phase delays of an ultrasonic scanner are modified in order to compensate for a rippled aberrating layer made of silicone rubber. The characteristics of the proposed method, and the possibility of employing it clinically to correct for unknown inhomogeneities in acoustic velocity, are discussed. 相似文献
16.
The complex degree of coherence over a telescope aperture is measured by processing instantaneous values of the complex degree of coherence fluctuated by turbulent atmosphere. Fringe patterns produced by a computer-controlled wave-front folding interferometer are analyzed in a short time by a photodiode array to calculate the instantaneous values of the complex degree of coherence. The system is applied to one-dimensional simulation experiments. 相似文献
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18.
We present an analysis for polarization-sensitive optical coherence tomography that facilitates the unrestricted use of fiber and fiber-optic components throughout an interferometer and yields sample birefringence, diattenuation, and relative optic axis orientation. We use a novel Jones matrix approach that compares the polarization states of light reflected from the sample surface with those reflected from within a biological sample for pairs of depth scans. The incident polarization alternated between two states that are perpendicular in a Poincaré sphere representation to ensure proper detection of tissue birefringence regardless of optical fiber contributions. The method was validated by comparing the calculated diattenuation of a polarizing sheet, chicken tendon, and muscle with that obtained by independent measurement. The relative importance of diattenuation versus birefringence to angular displacement of Stokes vectors on a Poincaré sphere was quantified. 相似文献
19.
Liang Lü 《中国光学快报(英文版)》2006,4(2)
A real-time two-dimensional (2D) triangulation range finder is presented, which is composed of two linear complementary metal oxidation semiconductor (CMOS) chips, two camera lenses, and four light emitting diodes (LEDs). The high order distortion in image aberrations is the main factor responsible for the coarse errors. The theoretical prediction is in good agreement with experiments and the correction equation is used to obtain more reliable results with the unique distortion coefficient in the whole working region. 相似文献
20.