Translation of "Brechwert" in English

A higher index or refraction is essential in the wavelength range decisive for the particular application.

Preferably one such immersion liquid has an index of refraction value of greater than 1.5.

The correction or the cylindrical refractive power can, in particular, be adjusted continuously.

Preferably, the refractive power and the astigmatism are calculated as follows:

With a constant refractive index n=1.525, the interior surface, thus, has a power of -3 dpt.

The other oxides can have an advantageous effect on the refractive index and the chemical resistance.

The refractive power of the incoming wavefront and/or refractive surface only influences the sec.

The refractive power and the astigmatism can be represented and determined one-dimensionally by imaging properties in the refraction plane by:

Thus, astigmatism, dioptric power, coma and spherical aberration, inter alia, are obtained for each direction of view.

Such an aspheric toric surface, therefore, establishes a cylindrical lens power of 2 diopters.

At intermediate orientations, the refractive power changes gradually from the greatest to the smallest value, or reverse.

The spherical power indicates what type of glasses you need to correct your vision problem.

A multifocal spectacle lens is described with a high positive focal power, with a convex front surface which comprises an aspheric focal portion with an additional near segment, a transition zone surrounding the focal portion and a rim zone, and with an inside surface which forms an afocal margin together with the rim zone.

The disadvantage of this layer system is in the choice of materials with high refractive index for the layer resting on the substrate.

In any event, however, due to the invented design not only ophthalmic lenses having constant refractive power or ophthalmic lenses having astigmatic power, but also ophthalmic lenses having progressive and, if required, also astigmatic power can be realized, which entirely or partially are produced by the variation of the refractive index or in which the correction of the aberrations entirely or partially occurs due to the variation of the refractive index, whereby the respective required variation of the refractive index may be attained by means of the invented concept of gradient-generating surfaces in conjunction with, as such, known fabricating processes.

Neither the density of at least 2.45 g/cm3 nor the refractive index of greater than 1.52, both of which are required of crystal glass, are achieved by the majority of the glass compositions indicated here.

In addition to the refractive index, the optical transmission in accordance with DIN 67507 and the standard chromaticity coordinates x and y in accordance with DIN 5033 for a glass thickness of 11 mm are shown.

The high content of Sb2 O3 and alkaline-earth oxides has the disadvantage that, caused by the high index of refraction of these glasses, sizable light losses due to scattering must be accepted in areas where the filters meet.

A lacquer system adapted to the refractive index of the glass to be coated is produced by mixing a silicic acid heteropolycondensate of 62.5 mole percent of diphenylsilane, 32.5 mole percent of methylvinylsilane and 5 mole percent of tetraethoxysilane with poly(methyl methacrylate) in a weight ratio of 7:3 and dissolving the resulting binder component in ethyl acetate, in a weight ratio of 1:4.

To produce a lacquer system matched to the refractive index of the glass surface to be coated, the silicic acid heteropolycondensate used in Example 1 is mixed with poly(methyl methacrylate) in a weight ratio of 1:1 and diluted with ethyl acetate in a weight ratio of 1:10 to 1:20.

After the coating has dried for three hours, it is overcoated with an unfilled lacquer (dilution 1:1) of matching refractive index, after which the coating is again dried for at least 1 day.

The refraction index of the respective lenses interposed into the observation system can be read through a window provided in the housing in magnified and illuminated form.

As spectacle lenses with a high positive focal power are normally manufactured in a casting process from a plastic material, the known spectacle lens with an "affixed" near segment is simple to manufacture; a spherically shaped recess for the near segment is simply worked into the mould for the single vision lens.

Finally, an optical lens made of a transparent plastic and a first layer made of SiO directly on the substrate is known (German DE 44 30 363), wherein the second layer is made of borosilicate glass with a refractive value of 1.47 (lambda 55 nm) and has a thickness of up to 3 i, preferably 2550 nm, and the layers three to seven are formed from TiO 3, SiO 2, Al 2 O 3 for the purpose of an antireflection effect.

Further, and based on the same reason, materials may be used which have a higher index of refraction n H, which in praxis is mostly linked to an increased absorption coefficient.

The course of the sinuous line, which hereinafter is also referred to as the principal line, is selected in such a manner that it coincides at least approximately with the principal line of vision when the glance is lowered, i.e. with the point of penetration of the visual ray through the surface with continuously varying power when the glance is lowered.

The BaO content of from 0.9 to 15.7% by weight which is provided according to SU 1534979 A1 and is absolutely necessary is to be regarded equally critically; these glass materials exhibit a refractive index n d of from 1.577 to 1.634.