Concave Spherical Mirror Research Articles

Holographic grating based Ebert spectrograph

In this paper we discuss the aberration properties and design procedure of in-plane Ebert spectrograph using conventional as well as holographic diffraction gratings. In both cases the gratings are situated at the well-known √3-position so that the spectrum can be recorded on a flat surface. It has been found that the holographic grating system has better resolution than the conventional grating system. The design parameters of a medium sized holographic grating spectrograph in which a concave spherical mirror is mounted in the off-axis configuration have been specified. The performance of the spectrograph has been evaluated by plotting spot diagram.

Method for first-order design of a transfer optics system to throughput match a Fourier transform spectrometer to a sample cell without use of a field lens at the cell input

The realization that the usual optical geometry of an absorption cell is the frustrum of a cone and that a requirement can be put on any transfer optics system that eliminates the need for a field lens at the cell input leads to a powerful method of first-order optical system design through (1) determination of a required ray transfer matrix, unique except for sign, which requires a single concave spherical mirror (or lens) to implement and (2) getting additional degrees of freedom to make the system more practical at the expense of additional spherical mirrors (or lenses). Two successful applications of the method are described.

On the Twyman effect and some of its applications

This review is a survey of a number of papers on the Twyman effect, discovered in 1905, in the processing of optical glass. The subject of these works is a detailed study of the Twyman effect in optical glass, quartz and sapphire crystals, and metals in the form of thin wafers with a thickness of 1 to 0.1 mm. It has been established that plane-parallel wafers of the studied materials, ground on one side and polished on the other, bend until the surface becomes strictly spherical or elliptical, concave on the polished side with a radius of curvature in a quadratic dependence of the wafers' thickness and not depending on their size and shape. A phenomenological conclusion of the main law has been drawn. It reveals the physical sense of the Twyman effect through its connection with the surface tension of solids. Three new methods have been worked out which are rather interesting prospective applications of the Twyman effect (for studying anisotropy in crystals, for processing concave spherical mirrors, for measuring apparatus and for preparing a new type of spherical crystalline diffraction lattice for X-ray spectroscopy).

Procedure for multiparametric investigation of the combustion of metallic particles in a freely falling chamber

A new setup based on the observation of the behavior of metal particles burning inside a falling hermetically sealed chamber was created in order to improve the procedures for experimental combustion of metal particles in a freely falling chamber. The main part of the experimental setup, the falling platform, is illustrated. A spherical concave mirror, the optical system, the detachment shoe, and a photodiode 12 are described. The setup permits analyzing the effect of the velocity of the flow past the burning particle on the parameters and permits interrupting the burning of the particle at any time with sampling of the unburned residue for further analysis.

Measurement Of Long Radius Of Curvature

Several methods for the measurement of very long radius of curvature of a convex or concave spherical mirror are reviewed in this paper. These methods have relevance in the measurement of the radii of curvature of laser mirrors. The accuracies achievable with the various methods are compared and summarized.

Beam expander telescope design utilizing fast spherical primaries

An exact geometrical ray analysis has been used to derive the profiles for telescope secondaries that perfectly recollimate beams incident on fast concave spherical mirrors. Both Cassegrainian and Gregorian configurations are possible. The high magnification designs tend to redistribute the energy profile and may be used, for example, to make Gaussian beams more uniform.

Compact sensitive instrument for direct ultrasonic visualization of defects

A simple ultrasonic imaging cell based on the confocal combination of a plano-concave lens and a concave spherical mirror is described. When used in conjunction with a stroboscopic schlieren visualization system, it has the main attributes of a practical nondestructive testing instrument: it is compact, relatively inexpensive, and simple to operate; its sensitivity is fair, resolution and fidelity are good; it has a fairly large field of view and a test piece can be readily scanned. The scope of its applicability is described and discussed.

Thermal Performance Analysis of the Stationary Reflector/Tracking Absorber (SRTA) Solar Concentrator

The performance of a novel solar energy concentrating system consisting of a fixed, concave spherical mirror and a sun-tracking, cylindrical absorber is analyzed in detail. This concentrating system takes advantage of the spherical symmetry of the mirror and its linear image which, when taken together, form a tracking, solar-concentrating system in which only the small cylindrical absorber need move. The effects of mirror reflectance, concentration ratio, heat transfer fluid flow rate, radiative surface properties, incidence angle, an evacuated absorber envelope, and insolation level upon thermal performance of the concentrator are studied by means of a mathematical model. The simulation includes first order radiation and convection processes between the absorber and its concentric glass envelope and between the envelope and the environment; radiation processes are described by a dual-band, gray approximation. The energy equations are solved in finite difference form in order that heat flux and temperature distributions along the absorber may be computed accurately. The results of the study show that high-temperature heat energy can be collected efficiently over a wide range of useful operating conditions. The analysis indicates that mirror surface reflectance is the single most important of the principal governing parameters in determining system performance. Efficiency always increases with concentration ratio although the rate of increase is quite small for concentration ratios above 50. High fluid flow rate (i.e., lower operating temperature), an evacuated envelope, or a highly selective surface can enhance performance under some conditions. The conclusion of the study is that high-temperature heat energy can be generated at high efficiency by the present concentrator with present technology in sunny regions of the world.

Improvement of Absolute Accuracy for a Multiple Bounce Reflectometer Through a Detailed Effort to Reduce Systematic Errors

We have constructed a multiple-bounce reflectometer similar to the one designed by Kelsall. Systematic errors present the reflectivities measured on our multiple-bounce reflectometer have been significantly reduced for high-reflectivity mirrors. This reduction came about through careful study of all components in our system. The diffraction effects of the apertures in the reflectometer were studied with the aid of a computer program that calculated the radial intensity distribution due to the Fresnel diffraction from each aperture. The systematic errors arising from the attempt to measure a concave spherical mirror were studied and minimized. A second computer program calculated the systematic error introduced by pathlength changes as the number of bounces in the reflectometer increased. The replacement of the sample thermopile detector with a thin-film bolometer along with other equipment changes has improved the absolute accuracy to 0.001 for the measured reflectivities with a demonstrated precision of 0.0003. Previous measurements had been about 0.008 low compared to measurements on the V-W pass reflectometer at China Lake, California.

A Simple Method for Reducing Astigmatism from off-Axis Concave Spherical Mirrors

The advantages of mirror optics for spectrographic systems are well known, namely, that all wave lengths focus at the same place and that the reflection losses can be made very small. Most modern spectrographs use mirror optics. Some are able to use spherical mirrors1 while others must use off-axis paraboloidal mirrors2 to achieve the desired resolution. Inexpensive concave spherical mirrors are ideal for imaging the source on a spectrograph slit, except for the problem of astigmatism. Expensive off-axis corrected mirrors can be obtained, but they must then be used only at the designed off-axis angle. We have found a simple adjustable way to reduce the astigmatism from inexpensive spherical mirrors used at moderate off-axis angles.

Error Analysis to: Method for Approximating the Radius of Curvature of Small Concave Spherical Mirrors Using a He–Ne Laser

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text J. D. Evans, "Error Analysis to: Method for Approximating the Radius of Curvature of Small Concave Spherical Mirrors Using a He–Ne Laser," Appl. Opt. 11, 945-946 (1972) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Method for Approximating the Radius of Curvature of Small Concave Spherical Mirrors Using a He–Ne Laser

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text J. D. Evans and Frank Cooke, "Method for Approximating the Radius of Curvature of Small Concave Spherical Mirrors Using a He–Ne Laser," Appl. Opt. 10, 995-996 (1971) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

A New Optical System for Flame Spectroscopy with Special Reference to Thermally Assisted Anti-Stokes Fluorescence Applications

A new optical setup for increasing the intensity of atomic fluorescence flame spectrometry is presented. The arrangement consists of two concave spherical mirrors and an elliposidal mirror whose primary focus is located at the flame position, and secondary at the entrance slit of the monochromator. Approximately 10 times gain in the measured intensities was obtained. The system is also useful for flame emission work, for which about five times gain was observed. With a low background flame such as the air–H2 for the N2−H2 diffusion flame and 400 µ slits, calcium can be detected at the level of 0.005 µg/ml. Moreover, the observed thermally assisted anti-Stokes fluorescence of In and Ga can be of analytical importance since the detection limits with a total consumption burner and the air-H2 flame were found to be 0.015 and 0.02 µg/ml, respectively. Detection limits in atomic fluorescence for Cr, Tl, In, and Fe are also presented.

The Common Test for Plane Mirrors

The optical test for the flatness of a plane mirror in conjunction with a concave spherical mirror has been analyzed in terms of the hyperboloid to which it can be thought to be referenced. This geometrical approach renders obvious the requirement to make two tests, the second after rotating the plane mirror 90 degrees about its normal. The expression for the separation of the astigmatic foci for a long radius of curvature, nearly flat, mirror is in agreement with previous derivations.

Boundary-layer structure in a shock-generated plasma flow: Part 2. Experiments using a new quantitative schlieren technique

The shock-tube side-wall boundary layer in a 1 eV, high-density argon plasma was studied experimentally using anew, simple, quantitative schlieren technique. The angular refraction of light which enters the shock-tube test section parallel to a side wall and passes through typically 1 mm thick boundary layers was determined in two separate wavelengths. This was done by measuring the displacements of two shadows formed by two thin wires placed in the point source light, which is reflected non-centrally by a concave spherical mirror. The experiments were of exploratory nature only, but clearly demonstrated the feasibility of the new technique in analysing plasma-boundary-layer flows. Measured electron density profiles in the high-temperature region of the sidewall boundary layers agreed within experimental errors with those calculated from the equilibrium-boundary-layer theory.

Objectives for Image Converters and Image Intensifiers

The design of objectives for image tubes is discussed with consideration given to the limited resolution of the tubes, the desired resolution in the object plane, and the desired field of view. Particular attention is given to the case of maximum quantum yield for given resolution and field of view. The design of a mirror objective is based on a spherical concave mirror as the main mirror and a plane mirror as the secondary.

Far-Infrared and Submillimeter Maser Oscillators with H2O and D2O

Construction and operating characteristics of far-infrared masers with water and deuterium oxide are presented. The maser tube is 5 cm in inner diameter with internal mirrors of about 5 m separation. The concave spherical mirrors of 6 cm diameter are used. Under the pulsed excitation of 5∼10 kV with 40 µs duration through the water vapor at about 0.2 Torr, strong maser oscillations are obtained at 47.4, 78.4, 79.1, 118.7, 120.1 and 220 µm wavelengths in H2O, and at 36.4, 72.7, 74.5, 84.3, 107.7 and 171.6 µm in D2O. Output characteristics against the gas pressure, the excitation voltage, and the longitudinal magnetic field are shown. At the optimum operation with the longitudinal magnetic fields peak output powers at 118.7 and 171.6 µm are estimated to be as large as about 3 and 6 W respectively.

Image formation with a concave spherical mirror

The author presents an elementary theory of image formation by a concave spherical mirror, elaborated for arbitrary angles of incidence and wide beams of rays. The image formation of a point source is either real, virtual or mixed according to the position of the source with respect to the mirror. If the ratio of the diameter of the mirror to its radius is at least 2∶3, the mirror does not provide virtual image formation. Point sources, the image formation of which is virtual (or mixed), form regions definable by simple constructions. At large angles of incidence it can happen that after reflection from the mirror the rays fall on the same mirror. A confuse image is produced. Some results on image formation with a concave spherical mirror can be extended to cylindrical and rotational surfaces with general meridian curves. Some formulae are derived for tangential image formation with a mirror having a parabolic meridian.

Optical method for adjusting concave spherical mirrors

Optical method for adjusting concave spherical mirrors

Reflecting Optics for Calibration of Spectroradiometers*

The requirements are given for absolute calibration of a spectroradiometer by means of an extended standard source. In some cases the extended source may be used without auxiliary optics, but in many cases a concave mirror is necessary or desirable. For such a mirror, a relation between incident and reflected steradiancy is derived. Brandenberg’s focusing relations for a concave spherical mirror are extended and applied to four practical cases, and it is shown that no loss in accuracy of calibration will result from the use of such mirrors provided that the source and the mirror are large enough. Experimental verification is given.