Plate Interferometer Research Articles

Integrated scatter plate and projection lens for scatter plate interferometer

Scatter plate interferometers provide a precise method to test the quality of concave mirrors. In this article we describe a method to integrate a scatter plate and a projection lens into a single binary micro-optical element, which is a crucial part of the scatter plate interferometer. We have designed an integrated element with the aid of a computer and fabricated it using the e-beam lithography method. We present experimental verification and some computer simulation results.

Electron beam fabrication of scatter plate for scatter plate interferometer

We have fabricated a computer-generated point symmetrical scatter plate with a negligible symmetry error for a scatter plate interferometer using electron beam writing equipment. The feature size of the scatterers in the scatter plate was 5 μm. The small scatterer size permits to test small f-number mirrors since the scattering angle of the light is large. This is the first example of such a fabrication of a scatter plate for the scatter plate interferometer. In this paper the advantages of the electron beam writing of a scatter plate are discussed and interferometric experiments are presented.

Computer simulation of the scatter plate interferometer by scalar diffraction theory

Detailed computer simulations of the scatter plate interferometer with random scatterers in the scatter plate are performed, for the first time to our knowledge, by use of the scalar diffraction theory in the paraxial domain. It is shown that the computer simulations produce output image patterns of the expected qualitative characteristics. A qualitative comparison of the computed pattern with the experimentally observed pattern is presented. The effects of translation of the scatter plate and distortion and tilting of the test object are also successfully simulated by the computer.

Fabrication of an array illuminator using tandem Michelson interferometers

Recently interferometric methods have been proposed for generation of arrays of equal intensity light spots. Double wedge plate interferometer and Michelson interferometers in tandem are used as array generators. However, there interferometric methods have poor light efficiency and low level of concentration of energy in addition to being bulky. We propose that a phase element realized by recording the cross interference pattern using Michelson interferometers in tandem on a photographic plate and subsequently bleaching it, can be used as a new type of array generator. The performance of such an element as an array generator is studied.

Holographic Array Illuminator Using Tandem Michelson Interferometers: Fabrication and Analysis

Abstract It has been reported that a double wedge plate interferometer and Michelson interferometers in tandem can be used to produce a cross pattern that can serve as an array of equal intensity light spots. In this paper we report on the holographic recording of this cross pattern. The phase hologram so produced serves as an array generator with some interesting characteristics. Theory and experimental results are presented.

Radius measurement by a zone plate interferometer

In this paper, we propose a differential interferometry to measure the radius of a concave mirror. This technique needs two sequential measurements before and after shifting the sample perpendicular to the optical axis. The radius of the spherical mirror is calculated from the difference of the phase distributions of the interferograms, and so the reference wavefront does not influence the measurement.

Neutron topography of interferometer output beams

Intensity distributions of the output beam of a perfect-crystal neutron interferometer recorded by a high-resolution position-sensitive detector are analysed. It was found that the interference pattern visibility is determined by an incoherent foundation of constant amplitude (no Moiré fringes were observed). A hypothesis about vibrations of the interferometer plates is presented. A modification of the setup following from this supposition increases the interference pattern visibility from 40% to 65–70%.

Programmable optical phase-mostly holograms with coupled-mode modulation liquid-crystal television

Commercial twisted nematic liquid-crystal television provides coupled phase and amplitude modulation. We propose a simple wedged shear plate interferometer for in situ measurement of its phase modulation and operating curve. For a given operating curve, the coupled-mode modulation holograms are designed with an iterative method. We adjust the operating curve by rotating the polarizer and analyzer to obtain the optimal operating curve. The phase-mostly holograms yield good-quality reconstructed images with the zero-order spot reduced to a minimum. Experimental results are shown.

Radius Measurement of a Concave Mirror by a Zone Plate Interferometer

A new technique to measure the radius of a concave mirror is proposed, in which the radius is calculated from the difference of the two interferograms obtained before and after shifting the sample perpendicular to or along the optical axis. By comparison of these two shifting directions, it is shown that since the amount of shift can be measured accurately and the result is insensitive to the tilt during the shifting, better accuracy can be obtained by shifting the sample along the optical axis.

Multiple Beam Wedge Plate Lateral Shear Interferometry in Transmission

Abstract It is shown that a multiple beam wedge plate interferometer can be used in transmission mode to display accurately the lateral aberration curve of a collimating lens. Experimental results showing the sharpened fringes and a comparison with the computed lateral aberration curves are given. Further, for larger shear, some new features are observed; these are explained by considering contributions of higher order terms in the Taylor's series expansion of the path function.

Modulation dynamics and spatiotemporal pattern generation in a microchip multimode laser

2N-1 different periodic oscillations are obtained experimentally in a microchip N-mode laser by different combinations of modulations at multiple relaxation oscillation frequencies that appear on the basis of antiphase dynamics among lasing modes. Application of mode-dependent periodic oscillations to generation of dynamic spatial patterns is demonstrated using a shear plate interferometer.

Simulation of A Wedge Plate Interferometer Using Holo Optical Elements

A wedge plate interferometer has been constructed using holo optical elements (HOEs). It comprises of two HOEs namely a Holo Shear Lens (HSL) and a Holo Shear Tilt Lens (HSTL). The combined effect of the two is to introduce a lateral shear and a tilt between the sheared wavefronts, the tilt beign orthogonal to the shear direction. This is equivalent to the conventional shear itnerferometer using a wedge plate for collimation testing. Theory and experimental results are presented.

A measuring method of a concave mirror by defocusing a scatter plate

Based on the fact that the phase variation is linearly proportional to the defocusing amount of the scatter plate, the additional phase shift can be achieved by defocusing the scatter plate in a controlled manner. Consequently, a method of how the phase shifting interferometric technique can be applied to the scatter plate interferometer is described. It has both the merits of a conventional scatter plate interferometer and the phase shifting interferometric technique. The validity of this method is demonstrated.

Phase Shifting Scatter Plate Interferometer Using a Polarization Technique

Abstract The structure of a conventional scatter plate interferometer is modified by a polarization technique, and a new type of phase shifting scatter plate interferometer is presented. It has both the merits of a conventional scatter plate interferometer and the phase shifting interferometric technique. The working of this interferometer is demonstrated.

Measurement of birefringence of optical materials using a wedged plate interferometer

A nondestructive technique for measuring the birefringence of optical materials such as calcite using wedged plate interferometer is presented. The sample needed for measuring the refractive index must be polished in the form of a parallel plate. The method is based on the measurement of the longitudinal displacement of the focus when the parallel plate is inserted in a converging beam of light. The displacement of the focus is a measure of the refractive index of the optical material. In the case of a uniaxial crystal, the displacement of the focus for the extraordinary ray is different from the displacement of the focus for the ordinary ray. Hence the birefringence of the crystal is determined by measuring the difference between the two focii. It is possible to obtain an accuracy up to 0.0002 in the measurement of birefringence depending on the sample thickness. The method should find its application for the characterization of new crystals in various material research and crystal growth laboratories.

Rotatable shear plate interferometer

A shear plate interferometer has been installed in a mount that allows the direction of shear to be rotated. With this instrument, the defocus and third-order aberrations in a laser beam can be measured very quickly, usually in about a minute including setup.

A null test of conic surfaces in zone plate interferometer

The use of a zone plate interferometer for a null test of conic surfaces is proposed. The zone plate used in this method can be produced optically and should be chosen so that its aberrations match those of the mirror under test. The condition for making the zone plate in this method is derived.

Accuracy of phase determination with unequal reference phase shift

In the fringe-scanning methods such as the three- and four-bucket methods, the phase of a reference wave is generally changed at equal intervals from 0 to 2π. In practice, however, it is difficult or almost impossible for some interferometers, such as the dynamic zone plate interferometer, to realize an equal phase shift and to make a full scanning of 2π, which are necessary for discrete Fourier transform analysis. We show that even in such a case, phases in an interferogram can be obtained by using a Fourier analysis in a continuous space, and we analyze the accuracy of the phase determination in case of additive noise.

Fringe scanning scatter plate interferometer using a polarized light

A fringe scanning scatter plate interferometer, which uses a polarized light to achieve the required phase shift between the reference and test beam, is described.

A null test of aspherical surfaces in scatter plate interferometer

Under the appropriate condition, it becomes possible that the excess optical path difference due to an off-axis scatter point cancels the optical path difference of an aspherical mirror from a spherical mirror. Using this condition, a new convenient method to realize the null test of aspherical mirrors is proposed without using any special optical element.