共查询到20条相似文献,搜索用时 15 毫秒
1.
Zhu Y Odate S Sugaya A Otaki K Sugisaki K Koike C Koike T Uchikawa K 《Applied optics》2011,50(18):2815-2822
We propose a design method of phase-analysis algorithms based on two-dimensional grating phase shifting for Talbot interferometry, Talbot-Lau imaging, or the Ronchi test. These algorithms are designed to separate the two orthogonal shearing wavefronts and eliminate error effects of unwanted diffraction orders, simultaneously. Taking the effect of multidiffraction into account, moving the two-dimensional grating along a certain pass leads to a series of phase-shifted interfrograms, from which two orthogonal shearing wavefronts are derived, for the tested wavefront to be retrieved. The designing process is demonstrated, and the residual errors are analyzed via simulation works and experimental comparison. 相似文献
2.
In this paper, we describe a zonal wavefront sensor in which the photodetector array can have a smaller number of rows. The test wavefront is incident on a two-dimensional array of diffraction gratings followed by a single focusing lens. The periodicity and the orientation of the grating rulings of each grating can be chosen such that the +1 order beam from the gratings forms an array of focal spots in the detector plane. We show that by using a square array of zones, it is possible to generate an array of +1 order focal spots having a smaller number of rows, thus reducing the height of the required detector array. The phase profile of the test wavefront can be estimated by measuring the displacements of the +1 order focal spots for the test wavefront relative to the +1 order focal spots for a plane reference wavefront. The narrower width of the photodetector array can offer several advantages, such as a faster frame rate of the wavefront sensor, a reduced amount of cross talk between the nearby detector zones, and a decrease in the maximum thermal noise. We also present experimental results of a proof-of-concept experimental arrangement using the proposed wavefront sensing scheme. 相似文献
3.
Latimer P 《Applied optics》1994,33(22):4983-4987
Cornu's spiral is used in the testing and extension of a recent explanation of the Talbot effect, which occurs in the Fresnel domain. The results confirm all parts tested. They also indicate that each band of a Talbot plane is controlled primarily by light from only a few slits of the grating, contrary to earlier assumptions. Increases in slit width are found to limit the number of Talbot planes that can be observed. 相似文献
4.
Analytic phase-factor equations for Talbot array illuminations 总被引:4,自引:0,他引:4
Under specific circumstances the fractional Talbot effect can be described by simplified equations. We have obtained simplified analytic phase-factor equations to describe the relation between the pure-phase factors and their fractional Talbot distances behind a binary amplitude grating with an opening ratio of (1/M). We explain how these simple equations are obtained from the regularly rearranged neighboring phase differences. We point out that any intensity distribution with an irreducible opening ratio (M(N)/M) (M(N) < M, where M(N) and M are positive integers) generated by such an amplitude grating can be described by similar phase-factor equations. It is interesting to note that an amplitude grating with additional arbitrary phase modulation can also generate pure-phase distributions at the fractional Talbot distance. We have applied these analytic phase-factor equations to neighboring (0, pi) phase-modulated amplitude gratings and have analytically derived a new set of simple phase-factor equations for Talbot array illumination in this case. Experimental verification of our theoretical results is given. 相似文献
5.
Podanchuk D Kurashov V Goloborodko A Dan'ko V Kotov M Goloborodko N 《Applied optics》2012,51(10):C125-C132
A holographic wavefront sensor based on the Talbot effect is proposed. Optical wavefronts are measured by sampling the light amplitude distribution with a two-dimensional (2D) precorrected holographic grating. The factors that allow changing an angular measurement range and a spatial resolution of the sensor are discussed. A comparative analysis with the Shack-Hartmann sensor is illustrated with some experimental results. 相似文献
6.
We present what we believe to be a novel method for order sorting a Fabry-Perot interferometer using a Fourier transform spectrometer (FTS) in tandem. We demonstrate how the order sorting is achieved using a model instrument response as an example of an instrument working in the 5-25 microm band, although the method is generally applicable at all wavelengths. We show that an instrument of this type can be realized with a large bandwidth, a large field of view, and good transmission efficiency. These attributes make this instrument concept a useful technique in applications where true imaging spectroscopy is required, such as mapping large astronomical sources. We compare the performance of the new instrument to grating and standard FTS instruments in circumstances where the measurement is background and detector noise limited. We use a figure of merit based on the field of view and speed of detection and find that the new system has a speed advantage over a FTS with the same field of view in all circumstances. The instrument will be faster than a grating instrument with the same spectral resolution once the field of view is >13 times larger under high background conditions and >50 times larger with detector performances that match the photon noise from Zodiacal light. 相似文献
7.
The effects of an arbitrary small inclination between two cross gratings on the moiré fringes in Talbot interferometry are discussed when the frequencies of the grating differ in two perpendicular directions. We show that the small angles, alpha and beta, by which the beam-splitter cross grating is rotated around the two axes parallel to the two perpendicular line directions of the cross grating, have a greater influence on the moiré fringes with cross gratings than that with one-dimensional gratings. A simple and practical detection method for the angles between the two unparallel grating planes in Talbot interferometry is also proposed. The theoretical analyses are proved by experimental results. 相似文献
8.
We can form a grating image with two gratings having different pitches with an extended light source. It is called generalized grating imaging or the Talbot-Lau effect. When we want to obtain high contrast image with pure absorption gratings or pure phase gratings, the separation between the two gratings is restricted. This corresponds to the Talbot condition. In this paper, we propose to use a combination of absorption grating and phase grating to relax the separation restriction. The theory of generalized grating imaging is applied to the system with this kind of grating. Simulations are performed for calculating contrast variation and show that the proposed system practically relaxes the Talbot condition. An experiment verifies the result of the simulation. 相似文献
9.
Abstract Talbot fringe projection, a moiré technique, is applied to three-dimensional contouring of diffuse targets for absolute shape measurement. The basic system relies on depth coding the test target surface by projecting the Talbot image of a linear grating. A second grating, similar to that used for the Talbot image, is employed to obtain the moiré fringes. These fringes represent surface contours of equal depth. Using a phase measurement technique and digital image processing algorithms, the surface shape information is obtained from the contour maps. Experimental results, merits and limitations of the system are discussed. 相似文献
10.
剪切干涉仪光子计数法动态波前探测 总被引:1,自引:0,他引:1
实时动态波前探测技术是自适应光学系统最重要的单元技术之一。本文报导了在弱光条件下,利用动态剪切干涉仪和光子计数法进行弱光波前误差探测的实验。叙述了波前探测装置的原理,讨论了相位测量的主要误差源。实验结果表明,在每一探测周期内,仅有几十到一百个光电子脉冲的情况下,可获得波前信息。 相似文献
11.
We discuss the effects of a general small inclination misalignment, which is formed by rotation of the beam-splitter grating around an axis that is laid on the grating plane and that has an arbitrary angle with respect to the line direction of the grating, between the two grating planes on the moiré fringes in Talbot interferometry. It is shown that the small inclination angle has a significant influence on measurement results based on Talbot interferometry because both the period and the slope of the moiré fringes are sensitive to the angle, especially when the rotation axis is nearly parallel to the lines of the grating. Simple and practical detection methods for the small inclination angle are proposed, and the effects of the inclination angle on the contrast in the moiré fringes are also briefly discussed. 相似文献
12.
Talbot interferometry is used to study the surface profile of a transparent object. Periodic patterns are produced by illuminating a grating with a collimated laser beam. The object is placed on the self-image plane of the grating. The deformed grating image, which interferes with another grating, results in the Talbot interferometric fringes. The fringe pattern is recorded on a CCD camera for subsequent analysis, and the phase variation is achieved by a linear translation stage. In this application two specimens are tested to demonstrate the validity of the method; one is a transparent object with a spherical shape with a height of less than 350 microm, and the other is a transparent object with an uneven surface of 50-microm average height. The experimental results are compared with the test results obtained with the mechanical stylus method. 相似文献
13.
We introduce a profilometry sensor that combines phase shifting with a Talbot self-image of a sinusoidal grating as the illumination part of the sensor. Contrast of the Talbot diffraction pattern produced with a sinusoidal grating in a diverging beam is theoretically discussed and verified experimentally. The mathematical relationship that is used to convert the phase measured with this sensor to the corresponding relief of an object is derived in the Appendix. A ceramic former used in the production of lenses was profiled with this sensor, and measurement results are presented. 相似文献
14.
Arrizón V Rojo-Velázquez G 《Journal of the Optical Society of America. A, Optics, image science, and vision》2001,18(6):1252-1256
We present a compact analytical formulation for the fractional Talbot effect at the paraxial domain of a finite grating. Our results show that laterally shifted distorted images of the grating basic cell form the Fresnel field at a fractional Talbot plane of the grating. Our formulas give the positions of those images and show that they are given by the convolution of the nondistorted cells (modulated by a quadratic phase factor) with the Fourier transform of the finite-grating pupil. 相似文献
15.
《Optical Materials》2014,36(12):2496-2501
We introduce a figure of merit for the photon spin-to-orbital angular momentum conversion via electrooptic (EO) Pockels effect in single crystals. Relations for the effective EO coefficients are derived for different symmetry groups. We show that Bi12TiO20 crystals reveal the highest figure of merit among well studied crystalline EO materials. The efficiency of the spin-to-orbital angular momentum conversion is measured experimentally for a number of single crystals. 相似文献
16.
Behind periodic amplitude or phase objects, the object transmittance is repeated at the so-called Talbot distances. In these planes perpendicular to the propagation direction, Talbot self-images are formed. In the case of plane wave illumination, the distances between the self-images are equally spaced. A periodic pattern called optical carpet or Talbot carpet is formed along the propagation direction. We show theoretically how the presence of spherical particles (10 to 100 μm in diameter) behind gratings of 20 and 50 μm period affects the formation of Talbot carpets and Talbot self-images at 633 nm illumination wavelength. The scattering of the particles is modeled by the Fresnel diffraction of its geometrical shadow. We analytically calculate the interference of the diffraction orders of rectangular and sinusoidal amplitude gratings disturbed by the presence of particles. To verify our model, we present measurements of Talbot carpets perturbed with both opaque disks and transparent spheres, and discuss the effects for various size parameters. We present an approach to simulate the movement of particles within the Talbot pattern in real time. We simulate and measure axial and lateral particle movements within a probe volume and evaluate the effect on the signal formation in a Talbot interferometric setup. We evaluate the best system parameters in terms of grating period and particle-detector-distance for a prospective measuring setup to determine characteristics of flowing suspensions, such as particle volume concentration or particle size distribution. 相似文献
17.
Lu PP Bullington AL Beyersdorf P Traeger S Mansell J Beausoleil R Gustafson EK Byer RL Fejer MM 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(3):659-668
It may be advantageous in advanced gravitational-wave detectors to replace conventional beam splitters and Fabry-Perot input mirrors with diffractive elements. In each of these applications, the wavefront distortions produced by the absorption and subsequent heating of the grating can limit the maximum useful optical power. We present data on the wavefront distortions induced in a laser probe beam for both the reflected and diffracted beams from a grating that is heated by a Gaussian laser beam and compare these results to a simple theory of the wavefront distortions induced by thermoelastic deformations. 相似文献
18.
The detection limit is an important figure of merit for evaluating instrumentation and analytical methods. While the detection limit for techniques using linear calibration functions has been studied extensively, this fundamental metric has rarely been discussed for mass spectrometry that bases the calibration on the principle of isotope dilution. We have developed a formulation for the detection limit for isotope dilution mass spectrometry (IDMS) after a thorough analysis of the uncertainty of IDMS measurements. The new formulation describes the IDMS detection limit as a function of the enrichment of the isotopic spike and the linear calibration detection limits measured at the masses for the isotope ratio measurement. 相似文献
19.
Polarization-dependent Talbot effect 总被引:1,自引:0,他引:1
Lu Y Zhou C Wang S Wang B 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(9):2154-2160
The term "polarization-dependent Talbot effect" means that the Talbot self-imaging intensity of a high-density grating is different for TE and TM polarization modes. Numerical simulations with the finite-difference time-domain method show that the polarization dependence of the Talbot images is obvious for gratings with period d between 2 lambda and 3 lambda. Such a polarization-dependent difference for TE and TM polarization of a high-density grating of 630 lines/mm (corresponding to d/lambda=2.5) is verified through experiments with the scanning near-field optical microscopy technique, in which a He-Ne laser is used as its polarization is changed from the TE mode to the TM mode. The polarization-dependent Talbot effect should help us to understand more clearly the diffraction behavior of a high-density grating in nano-optics and contribute to wide application of the Talbot effect. 相似文献
20.
Flatness of the wavefront diffracted by grating can be mandatory for some applications. At ambient temperature, the wavefront diffracted by a volume phase holographic grating (VPHG) is well mastered by the manufacturing process and can be corrected or shaped by postpolishing. However, to be used in cooled infrared spectrometers, VPHGs have to stand and work properly at low temperatures. We present the measurement of the wavefront diffracted by a typical VPHG at various temperatures down to 150 K and at several thermal inhomogeneity amplitudes. The particular grating observed was produced using a dichromated gelatine technique and encapsulated between two glass blanks. Diffracted wavefront measurements show that the wavefront is extremely stable according to the temperature as long as the latter is homogeneous over the grating stack volume. Increasing the thermal inhomogeneity increases the wavefront error that pinpoints the importance of the final instrument thermal design. This concludes the dichromated gelatine VPHG technology, used more and more in visible spectrometers, can be applied as it is to cooled IR spectrometers. 相似文献