Concave Spherical Mirror Research Articles

Modes in Spherical-Mirror Resonators

This work is the examination of a cavity mode approach to the mode structure of a laser. Solutions of the vector wave equation for electromagnetic fields in and between perfectly conducting oblate spheroidal cavities are examined for the case of wavelengths much less than cavity dimensions. These solutions are the field modes in Fabry—Perot type resonators with equal-radius concave spherical mirrors, or with concave—convex spherical mirrors, when the parameters of the oblate spheroids are chosen so that the radii of curvature and spacing on the axis of rotation match those of the resonator mirrors. Expressions for the transverse and longitudinal mode structures are derived. The eigenvalue equations are written, and are solved for the case of the two lowest-order modes.

A simple monochromator for ultraviolet microscopy

I N most commercial monochromators the aperture of the exit beam is much larger than that of a microscope condenser in its object space. Accordingly, unless extra mirrors or lenses are used, a considerable amount of light is lost and the dispersive power of the instrument is not fully utilized (e.g. [l, a]). We have found that a very useful and extremely simple monochromator can be built with an aperture ratio of the exit beam of 1:70 if the parts are arranged as in Fig. 1. There is one concave spherical mirror S, which yields an image of the entrance slit in the plane of the exit slit. Of the rays passing through the prism those nearest to the refracting rib are made to be minimally refracted. As the beam is converging, the other rays will undergo an ever greater than minimal deviation according as their distance from the refracting rib increases. It has been found that this results in a remarkably good compensation of the image faults caused by the off-axis position of the spherical mirror. For the purpose in hand the effectiveness of this compensation is amply sufficient throughout the visible and ultraviolet spectra as is evidenced by the high pressure mercury arc line images in Figs. 2 and 3. The complete reversal of the mercury line 254 m,u that occurs in the arc we used may serve to give an estimate of the amount of stray light present in the ultraviolet part of the spectrum (see Fig. 3). The relative intensities of the spectrum have been measured by means of a 1 P 28 RCA photomultiplier tube. It was found that at the 254 rnp setting of the monochromator, the photomultiplier current was less than 1 per cent of that at either 248 or 257 rnp. Apparently, the amount of stray light in the monochromator is negligible when used with a mercury arc.

A Dynamical Demonstration of f = R/2 for a Concave Spherical Mirror

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Geometrical Optics of Concave Mirrors and of Combinations of Mirrors

A study of the geometrical optics of a concave spherical mirror is made over the range of incidence from normal to grazing. An examination is made of methods of correcting for astigmatism at oblique incidence by the use of " crossed " mirrors (spherical and cylindrical), of " parallel " cylindrical mirrors, and of a single mirror with different radii of curvature in planes at right angles. Such a single mirror combines in one piece image formation and beam deviation.

SPECTRAL SENSITIVITIES FOR LEAF AND STEM GROWTH OF ETIOLATED PEA SEEDLINGS AND THEIR SIMILARITY TO ACTION SPECTRA FOR PHOTOPERIODISM

SPECTRAL SENSITIVITIES FOR LEAF AND STEM GROWTH OF ETIOLATED PEA SEEDLINGS AND THEIR SIMILARITY TO ACTION SPECTRA FOR PHOTOPERIODISM

Formation of Optical Images by X-Rays

Several conceivable methods for the formation of optical images by x-rays are considered, and a method employing concave mirrors is adopted as the most promising. A concave spherical mirror receiving radiation at grazing incidence (a necessary arrangement with x-rays) images a point into a line in accordance with a focal length f=Ri/2 where R is the radius of curvature and i the grazing angle. The image is subject to an aberration such that a ray reflected at the periphery of the mirror misses the focal point of central rays by a distance given approximately by S=1.5Mr2/R, where M is the magnification of the image and r is the radius of the mirror face. The theoretically possible resolving power is such as to resolve point objects separated by about 70A, a limit which is independent of the wave-length used. Point images of points and therefore extended images of extended objects may be produced by causing the radiation to reflect from two concave mirrors in series. Sample results are presented.

A Model to Demonstrate Spherical Aberration of a Concave Spherical Mirror

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A Long Optical Path in a Restricted Space

An instrument is described for attaining a long optical path by repeated traversal between a concave spherical mirror and a totally reflecting prism. Its properties are outlined and compared with those of other devices for similar purposes. The number of traversals is in principle unlimited (we have used ours in practice for several numbers of traversals up to twelve) but the angular spread of the final beam is less than that of the first traversal by an amount that might become serious for a very large number of traversals. The final image, which is almost free of aberration, is as large, and in favorable cases almost as bright, as the source; the prism yields greater brightness than an all-mirror device at short wave-lengths, but less at long wavelengths. The optical adjustments are simple, even for many traversals. The optics of the instrument is considered in detail, with special attention to the influence of the prism angle upon the effective aperture of the emergent beam. A model of the instrument, now in use, is described.

Spectrophotometry of reflecting materials

A method of adapting a photoelectric spectrophotometer to the measurement of reflecting materials is described. The specimen is illuminated normally and all the light diffused by the specimen between angles of 35? and 55? is focused on the photocell by reflexion from a spherical concave mirror. The C.I.E. conditions for the illumination and viewing of reflecting materials in colour measurement are thus closely adhered to, while the sensitivity of the spectrophotometer does not fall below 0.3 of its value when measuring transparent specimens.

Interference by reflexion from a concave spherical mirror

Interference by reflexion from a concave spherical mirror

Simply Constructed Ultraviolet Monochromators for Large Area Illumination

Several types of large ultraviolet monochromatic illuminator are described, in which water or other transparent liquid is used as the dispersing medium. The most readily made consists merely of a spherical concave mirror immersed in a basin of distilled water at an angle of about 30° from the horizontal; this acts as a crude prism somewhat on the principle of the Féry quartz prism, and gives monochromatic though distorted images of a high power horizontal mercury arc used as a source. By placing an exit slit of suitable shape in the focal plane these images can be isolated one at a time, giving surprisingly pure monochromatic radiation. Such an instrument of large size can be constructed at small expense and should be useful for many types of biophysical and photochemical work. A somewhat more expensive but more distortion-free instrument can be made by using a plane mirror under water with one or two large lenses of fused quartz. The horizontal position of the input face of the water prism greatly reduces convection currents, and renders large sheets of expensive optical material unnecessary. Instruments of both types with aluminum, chromium and platinum-coated glass mirrors over eight inches in diameter have been constructed and found to operate satisfactorily. Typical spectrum photographs taken with one of the concave mirror instruments show the degree of spectrum resolution obtained.

Ronchi's Method of Optical Testing

view Abstract Citations (11) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ronchi's Method of Optical Testing Anderson, J. A. ; Porter, Russell W. Abstract i. Ronchi's mei/zod.-Light from a slit is brought to a focus by the lens or mirror to be tested. A short distance in front of (or behind) the focal plane is placed a line- screen having a spacing of 40-200 lines per centimeter, so oriented that the lines are parallel to the slit image. The shadow lines seen by the eye placed at the focus indicate clearly the characteristics of the wave surface as it leaves the lens or mirror. This meth- od, which is described in Italian publications, is probably not so familiar to American readers as it deserves to be. 2. Modification of Ronchi's nzelhod.-Instead of a single slit, a line-screen ifiumi- nated by a frosted lamp or even by sky light may be used as the source, with the ad- vantage that the ifiumination is so greatly increased that all observations can be made in a fully illuminated room. Also, for testing concave spherical mirrors, or lenses and paraboloids with parallel light, only one screen is required, one-half of which serves as the source, the other half as the observing screen. In this case the lines of the image are automatically parallel to those of the observing screen. ~. A simple mounting for the screen and light-source is described. ~. Results of the examination of a number of lenses and of a slightly defective con- cave mirror are given; these show that the method is fully as sensitive as the Foucau~t knife-edge test Publication: The Astrophysical Journal Pub Date: October 1929 DOI: 10.1086/143213 Bibcode: 1929ApJ....70..175A full text sources ADS | Related Materials (1) Reprint: 1929CMWCI.386....1A

Laboratory Notes by Professor Tait - 3. On a simple Mode of explaining the Optical Effects of Mirrors and Lenses

It is very singular to notice how small a matter makes the difference between the intelligibility and unintelligibility of a demonstration to an audience as a whole not mathematical. In no part of Physics have I found this so marked as in the most elementary portions of geometrical optics. Such a formula aswhen interpreted directly as signifying that “the sum of the reciprocals of the distances of the object and image from the surface of a concave spherical mirror, is equal to double the reciprocal of the radius of the mirror,”. if understood at all, is understood as a sort of memoria technica which enables the student to make calculations; but unless he have some knowledge of mathematics it suggests absolutely no higher meaning.