Transparent heat mirrors of the antireflecting metal type with a dielectric/metal/dielectric structure are studied. It is found that dielectrics of lower refractive index give a higher cutoff wavelength, but the transition becomes more gradual. The angular behavior of these mirrors is also analyzed. The optimum mechanical efficiency obtainable with a plain collector and a carnot engine is given for different concentrations and refractive indices. Moreover it appears that using Al instead of Ag introduces appreciable absorption losses (~25-35%).
A simple light-slicing technique for the direct measurement of the free-surface shape h(x) in onedirectional transient liquid flows is studied. The method is used to determine h(x) with a precision of the order of 10(-2) mm along a line several centimeters long, allowing for height differences of some millimeters. It is useful for transient flows in rectangular channels in which capillarity and liquid adhesion at walls perturb lateral observations; the method can also be used for nondiffusive fluids in cases in which it is not advisable to add diffusive particles.
The generalized sine condition for an image-forming system with centering errors but allowing for one symmetry plane is derived according to the Fourier optics approach. The variation of the wave-front-aberration function associated with a small displacement of field coordinates is given. The symmetry properties of aberrations are discussed.͓(x o Ј , y o Ј)͔, coordinates at the entrance (exit) pupil with origin at Ẽ o (Ẽ o Ј).
A bare metallic grating illuminated by a plane, S-polarized electromagnetic wave can completely absorb one of the diffracted orders. These strong absorptions have been reported to be accompanied by two different types of behavior. Here we calculate, by means of an exact differential method, the phase versus angle-of-incidence curves for cycloidal metallic gratings with different groove-depth-to-period ratios. We show that an algorithm based on the electromagnetic theory of gratings can account for the experimentally observed behavior in the vicinity of a resonant anomaly. We also show that this type of study provides additional information about the position of the zeros of the scattering matrix in the complex plane.
Coma compensation in a parabolized Ebert monochromator is studied using the plate diagram. It is shown that two different criteria may be used: narrowest images or symmetrical ones; however, both may not be satisfied simultaneously. Symmetrical or narrowest images may be obtained for an extended range of wavelengths with displacement of at least one of the slits. With fixed slits only incomplete compensation may be obtained.
We calculate the complex degree of coherence for any interferometer in which there is amplitude division and simple interference. We consider the exact optical path length differences between both branches. We find that, when there is a localization surface, this degree of coherence is equivalent to the complex optical disturbance at the image of an aberrated isoplanatic optical system. Moreover, we show that the radius of the central lobe at the diffraction pattern of this equivalent system is the distance between rays when visibility is zero. This distance enables us to evaluate localization depth and adjustment tolerance.
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