Ronchi Grating Research Articles

Macroscopic Violation of Duality Generated on a Laser Beam

It is shown theoretically and experimentally that passage of a laser beam through particular conventional Ronchi gratings prepares the beam in an altered state that violates quantum duality. The violation is characterized by a readily measured net transfer of energy between the prepared beam and an unmodified beam from a similar, independent laser. Notably, the experiment is conducted with the beams at macroscopic power levels where measurability of the duality-violating transfer is vastly improved over that of the discrete photon regime. These results are consistent with other recently reported experiments that have challenged the validity of the duality-related principle of complementarity.

Phase contrast microscopy with fringe contrast adjustable by using grating-based phase-shifter

In this paper a new phase contrast method with fringe contrast adjustable is proposed. In the Fourier plane of the object wave, two Ronchi gratings i.e., a central grating and a surrounding grating, are used to modulate the phases of the undiffracted and diffracted components, respectively. By loading the two gratings separately on spatial light modulator, the undiffracted and diffracted components can be measured independently, which simplify greatly the reconstruction process. Besides, the fringe contrast of the phase contrast interferogram can be adjusted by changing the modulation depth of the two gratings. The feasibility of the proposed method is verified by theoretical analysis and experiment.

Four-step spatial phase-shifting shearing interferometry from moiré configuration by triple gratings

A spatial phase-shifting shearing interferometry is presented in this paper. The whole optical configuration is simple and consists of three Ronchi gratings. Four phase-shifted shearing interferograms can be obtained simultaneously. The explicit intensity distributions of shearing interferograms are given and a corresponding four-step spatial phase-shifting algorithm is proposed to extract phase information from the new interferometry. This spatial phase-shifting configuration is applied to extract phase projection of a propane flame and a mathematical error analysis is presented.

Behavior of a periodic chromatic test with an achromatic Ronchi grating as a background

AbstractThe aim of this article is to study the influence of an achromatic Ronchi grating (white and black stripes) used as a background, over a periodic chromatic test (red or green). Depending on the grating frequency, two parameters were used to study this influence: modulation ratio and grating contrast. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2012

Collimation testing using coherent gradient sensing

In the present communication, an application of coherent gradient sensing (CGS) for collimation testing of an optical beam has been proposed. In the path of the beam to be tested, a set of two identical linear Ronchi gratings is introduced. The diffracted orders from the two gratings traveling in the same direction are isolated using spatial filtering arrangement. The resulting laterally sheared wavefronts carry information regarding the defocusing errors. The grating rotation mechanism has been incorporated for collimation setting. The results of experimental investigation are presented. Improved accuracy and precision has been achieved because the requirement of maintaining the grating separation to be equal to self-imaging distance as in Talbot interferometry has been alleviated.

Evaluation of the increment of the sampling in optical testing using substructured Ronchi gratings

In this paper, we use Ronchi substructured gratings to evaluate the increment of the accuracy in optical testing using a liquid crystal display. For this, we perform a comparison between the aberration function and the wavefront obtained with classical Ronchi gratings against the ones obtained using substructured Ronchi gratings. This analysis is performed for different gratings positions, both outside and inside of focus. We show the results obtained in the laboratory for a concave spherical mirror of 57.27 mm diameter and a radius of curvature of 397.55 mm. We conclude that by using substructured Ronchi gratings we can test a larger area of ronchigram.

Slope measurement of a phase object using a polarizing phase-shifting high-frequency Ronchi grating interferometer

An interferometric method to measure the slope of phase objects is presented. The analysis was performed by implementing a polarizing phase-shifting cyclic shear interferometer coupled to a 4-f Fourier imaging system with crossed high-frequency Ronchi gratings. This system can obtain nine interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope of a phase object, it is only analyzed using four patterns obtained in a single shot, and applying the classical method of phase extraction.

一种制作投影灰度正弦光栅的新方法

Traditional methods are difficult to fabricate the gray sinusoial grating in structured-light three-dimension projection measuring system,and if replaced by Ronchi grating will affect the measurement accuracy.A novel method for gray sinusoidal grating plate fabrication is presented.Through the analysis of transmittance curve of holographic silver halide plate,the reason that sinusoidal interference pattern of contrast degree for 1 can not be linearly recorded and transformed is pointed out.A new method of linear recording is proposed,which provides a pre-exposure uniformly incoherent light bias point.The experimental results show that the sinusoidal interference fringes record of symmetrical two-beam can be obtained by the spatial filtering method,and the linear and high contrast record of sinusoidal interference fringe can be achieved by exposure controlled accurately in the linear region of the holographic silver halide plate.

基于Talbot-Moiré法测量透镜焦距的莫尔条纹的图像处理

Based on Talbot effect and Moire fringes of Ronchi gratings,focal length measurement of the long focal length is carried out. The focal length of measured lens can be figured out accurately according to its relation to the slope coefficient of Moire fringes. To get the slope of Moire fringes, the image of Moire fringes is mainly filtered or smoothed by mathematics morphological method to enhance the contrast of fringes effectively. Then the filtered image is processed by thinning to single pixel width. The fringes are labeled to fitting lines to calculate the slope coefficient accurately,and the error of focal length is 0.10%.

Vibration Analysis at Microscale by Talbot Fringe Projection Method1

Abstract: This work focuses on the implementation of a structured light projection technique for the analysis of the 3D vibration modes of microsamples. The Talbot image of a Ronchi grating is projected onto the sample surface passing through one of the objective tube of a stereomicroscope thus realising a fringe projection system at a micrometric scale. An aluminium cantilever beam PZT‐driven into harmonic vibration served as test sample for investigating the possibility to get the full‐field vibration modes of micro‐objects. An automated Fourier transform analysis of the fringe patterns was performed to obtain the full‐field time‐resolved profile information of the sample at each frame delivered by a high‐speed camera with a micrometric resolution. A straightforward procedure for retrieving resonance frequency for different modes and vibration amplitudes along the whole sample surface was implemented. The great sensitivity and the full‐field capacities of the proposed experimental procedure allow to put in evidence differences between real and theoretical behaviours hence could be extremely useful for designing and testing structural dynamic response of microstructures and micro–electro–mechanical Systems.

Global measurement of water waves by Fourier transform profilometry

In this paper, we present an optical profilometric technique that allows for single-shot global measurement of free-surface deformations. This system consists of a high-resolution system composed of a videoprojector and a digital camera. A fringe pattern of known characteristics is projected onto the free surface and its image is registered by the camera. The deformed fringe pattern arising from the surface deformations is later compared to the undeformed (reference) one, leading to a phase map from which the free surface can be reconstructed. Particularly, we are able to project wavelength-controlled sinusoidal fringe patterns, which considerably increase the overall performance of the technique and the quality of the reconstruction compared to that obtained with a Ronchi grating. In comparison to other profilometric techniques, it allows for single-shot non-intrusive measurement of surface deformations over large areas. In particular, our measurement system and analysis technique is able to measure free surface deformations with sharp slopes up to 10 with a 0.2 mm vertical resolution over an interrogation window of size 450 × 300 mm2 sampled on approximately 6.1 × 106 measurement points. Some illustrative examples of the application of this measuring system to fluid dynamics problems are presented.

Determination of modulation transfer function of a printer by measuring the autocorrelation of the transmission function of a printed Ronchi grating

We show theoretically and verify experimentally that the modulation transfer function (MTF) of a printing system can be determined by measuring the autocorrelation of a printed Ronchi grating. In practice, two similar Ronchi gratings are printed on two transparencies and the transparencies are superimposed with parallel grating lines. Then, the gratings are uniformly illuminated and the transmitted light from a large section is measured versus the displacement of one grating with respect to the other in a grating pitch interval. This measurement provides the required autocorrelation function for determination of the MTF.

Ф630mm F/1.34抛物面的Ronchi光栅定量测量

The Ronchi grating is applied to measure the large-aperture aspheric surfaces in a quantitative way on the basis of self-made software which includes Ronchi null grating design, collection of Ronchi graph, and data processing. The measured concave parabolic mirror has a diameter of 630 mm and an F number of 1.34. The measurement result is approximately the same as that of the ZYGO interferometer. This analysis software and test method establish a good foundation for the quantitative measurement of the big error about the large-aperture aspheric surfaces of the next generation telescope.

Ronchi test with variable-frequency rulings

We present a new method for testing an optical surface. It uses the Ronchi test with variable-frequency rulings and a liquid-crystal display. The rulings can be formed by substructuring the spacing of a Ronchi ruling or combining several classical Ronchi rulings in a single variable-frequency ruling. This change allows us to observe smaller defects on the surface, because it enlarges the spatial-frequency domain of the ruling, and a larger dynamic range of detection of the Ronchi test can be obtained instead of increasing the resolution of the detection of the Ronchi test by iteratively changing classical Ronchi rulings with higher line density. As a result, we have found that it is possible to measure defects on a optical surface that are of size 57 nm (/11).

龙基光栅在大口径非球面定量测量中的应用

龙基光栅在大口径非球面定量测量中的应用

The use of defocussed position of a Ronchi grating for evaluating the refractive index of lens

This report describes a Ronchi-grating shearing interferometric collimation method for determining the refractive index of a lens. A new formula has been deduced for the refractive index of the lens, which is independent of lens parameters. This newly developed device has two lenses. One of them collimates the light from a point source while the other acts as a decollimator. The point source acting as a test target is situated in the front focal plane of the collimator. The test lens is placed inside a glass cell in the back focal plane of the collimator. The Ronchi grating is exactly placed in the back focal plane of the decollimator, and a fringe-free space is observed in the common region. When the test lens is immersed in a liquid cell, it disturbs the focal point and hence interference fringes are observed. The combined system consisting of the test lens and the decollimator is moved to bring the focal point on the Ronchi grating. Thus, the difference between the two settings gives the amount of defocusing.

Moiré Analysis for Assessment of Line Registration Quality

This paper introduces objective macro and micro line registration quality metrics based on Moiré interference patterns generated by superposing a lenticular lens grating over a hardcopy test page consisting of high-frequency Ronchi rulings. Metrics for macro and micro line registration are defined and a measurement procedure is described to enhance the robustness of the metric computation over reasonable variations in the measurement process. The method analyzes low frequency interference patterns, which can be scanned at low resolutions. Experimental measurements on several printers are presented to demonstrate a comparative quality analysis. The metrics demonstrate robustness to small changes in the lenticular lens and grating superposition angle. For superposition angles varying between 2° and 5°, the coefficients of variance for the two metrics are less than 5%, which is small enough for delineating between test patterns of different print quality.

Wavefront Measurement for Long Focal Large Aperture Lens Based on Talbot Effect of Ronchi Grating

We propose a wavefront measurement method based on Talbot effect. It is well known that the wavefront of large aperture long focal lens is difficult to be measured. Here a new method for wavefront measurement of large aperture long focal lens is presented, which is accomplished by fitting the slope of sub-wavefront in the whole aperture while the sub-wavefront slope is got by calculating the shifted moiré fringe numbers formed by Talbot effect of Ronchi grating in different position of the aperture. The formula of calculating the angle of subwavefront slope from the shifted moiré fringe numbers is derived. Error analysis demonstrates that this method can be applied to the wavefront testing with high accuracy.

TALBOT EFFECT FOR DISPERSION IN LINEAR OPTICAL FIBERS AND A WAVELET APPROACH

We shortly recall the mathematical and physical aspects of Talbot's self-imaging effect occurring in near-field diffraction. In the rational paraxial approximation, the Talbot images are formed at distances ζ = p/q, where p and q are coprimes, and are superpositions of q equally spaced images of the original binary transmission (Ronchi) grating. This interpretation offers the possibility to express the Talbot effect through Gauss sums. Here, we pay attention to the Talbot effect in the case of dispersion in optical fibers presenting our considerations based on the close relationships of the mathematical representations of diffraction and dispersion. Although dispersion deals with continuous functions, such as gaussian and supergaussian pulses, whereas in diffraction one frequently deals with discontinuous functions, the mathematical correspondence enables one to characterize the Talbot effect in the two cases with minor differences. In addition, we apply, for the first time to our knowledge, the wavelet transform to the fractal Talbot effect in both diffraction and fiber dispersion. In the first case, the self similar character of the transverse paraxial field at irrational multiples of the Talbot distance is confirmed, whereas in the second case it is shown that the field is not self similar for supergaussian pulses. Finally, a high-precision measurement of irrational distances employing the fractal index determined with the wavelet transform is pointed out.

Fast distance measurements by use of dynamic speckles

A technique for fast measurements of the distance to an object's surface based on spatial filtering of dynamic speckle patterns is proposed. Exploitation of two spatial filters (Ronchi rulings) enables measurements to be independent of surface speed. Experimental verification of the technique is demonstrated at speeds of the surface as high as 50 m/s. The technique may find applications in machine-vision systems for acquisition of three-dimensional images and in control systems for on-line monitoring of fast-moving parts of industrial machines.