DD153968A3 - OPTICAL FLUOROPHOSPHAT GLASS HAVING HIGH POSITIVE ANOMALIC TEA DISPLESION - Google Patents

Abstract

The invention relates to optical fluorophosphate glass with high positive anomalous partial dispersion in the blue part of the VIS spectral range, low dispersion (high dispersion coefficient) and variable, relatively high average refractive index. The glasses are suitable for correcting lens aberrations instead of previously used crystalline materials in optically imaging systems. They can be melted by conventional methods and with common raw materials in sufficient homogeneity for the application.

Description

2 19702 -1-

Title of the invention

Optical fluorophosphate glass with high positive at omaler partial dispersion

Field of application of the invention

Essential? Optical aberrations in lens systems are the chromatic and spherical aberration. While for the removal of the secondary color spectrum in the short-wave VLS spectral range materials with high positive anomalous relative partial dispersion in this area with the lowest possible dispersion (large dispersion coefficient) are required to correct aer spherical aberration glasses with an increased refractive index. Fluorophosphate glasses can be used for the most extensive color aberration correction in optical lens systems, i. used the construction of apochromats instead of previously used crystalline media v / earth. In general, the aim is to produce such glasses with the highest possible refractive index. According to the present invention, glasses having a high positive anomalous relative partial dispersion and a small dispersion with variation of the refractive index to relatively high refractive indices can be produced in optical quality and consequently find a wide field of application in optical imaging systems.

Character istik of the known technical solutions

The previously used to eliminate aberrations crystalline materials have compared to glasses

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the known disadvantages of poor mechanical properties and high manufacturing costs. Various patents have described fluorophosphate glass or beryllium fluoride glass compositions which have similar optical values (v> 75) and of which z ", T" are also given high values of the positive anomalous relative partial dispersion. However, these glasses have numerous disadvantageous properties due to their chemical composition. For example, the beryllium fluoride glasses (DS-AS 1 086 866) and the beryllium fluoride-containing fluorophosphate glasses (US Pat. 2,573,325, US Pat. No. 2,716,069) are high in their toxicity Kristallwuchsumsgeschv / indigkeit and poor optical homogeneity as a lens component in optical, imaging systems only under technologically difficult conditions «The use of alkali fluorides in fluorophosphate glasses (DB-OS 2 231 238, US 3 84-7 624, DE-AS 1 596 877) leads to an unfavorable viscosity-imparting characteristic for the production of the optical glasses and in addition to deterioration of the chemical resistance of the glasses. On the other hand, fluorides of unusual elements such as yttrium (DDR patent 104- 071) or complex fluorides (BED - OS 2 514 017, BRD-AS 1 596 877) have to be used to eliminate high crystal growth rates. In addition to the elimination of said adverse physical and chemical properties or "technologically conditioned characteristics such as toxicity, inhomogeneity, high crystal growth rates, poor chemical resistance and the use of rare raw materials or low viscosity up to relatively low temperatures is a greater variation, ie, an increase the refractive indices desirable »

The aim of the invention is the production of optical fluorophosphate glasses with high positive anomalous partial dispersion in the short-wave part of the VIS spectral region,

small dispersion (large dispersion coefficient) and relatively high refractive indices "The glasses should be able to be produced using conventional melt chemicals under technologically simple conditions in optical quality sufficient for the intended use.

Presentation of the essence of the invention

According to the present invention, optical fluorophosphate glasses having a high positive anomalous partial dispersion, small dispersion and a variable, relatively high refractive index in optical quality can be produced. According to the invention the object is achieved in that Fluorophosphatglaser be prepared from:

5.1 - 30 mole percent metaphosphates; and 7p - 94.9 fluorophosphons .

As metaphosphates are used:

2.5 - 20 mol% Ba (POo) ₂ and "O 15 mol% Zn (POo) ₂ and / or O - 6.2 mol%

As fluorides are used:

12-37.8 mol% AlF ₃ 11 51 mol% CaF ₂ 2.2-40 mol% MgF ₂ .

love the said fluorides can be introduced into the glass:

O-40 mol% SrF ₂ 0-16 MoIJS ZnF ₂ O - 13.3 mol% BaF ₂ .

The glasses produced from the constituents mentioned have refractive indices in the range of η 1.44 to η 1.55 * ν values in the range from 90.4 to 70.2, positive anomalous relative partial dispersion values in the range of ΔP "jif0, O14 to 0.042. The glasses have good athermal behavior (a nearly temperature-independent optical path length). In addition, through the use of lanthanum metaphosphate

-a favorable viscosity-temperature characteristic ^! obtained, which is advantageous for both the production of homogeneous glasses and for the ICristallisationsfestigkeit. Zinc metaphosphate contributes to the refractive index variation. Due to the chemical composition, the glasses have a high permeability from the near UV to the IR spectral range and steep absorption edges towards the UV region, so that they allow a wide range of application of the transmission characteristic. The glasses have good chemical resistance and are relatively insensitive to crystallization. The fluorine losses during the melting of the glasses are generally low. There is a dependence on the phosphate content, wherein in the range of 5 to 10 mol% metaphosphate, the fluorine losses below 5 wt% fluorine drop "The glasses can be melted under conventional methods in platinum crucible at 1273 K to 1573 K and cooled in preheated molds in the refrigerator ,

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embodiments

To illustrate the following table, it should be noted that the typical parameters of the new glasses are the following parameters: the Abbe number ν, the mean refractive index η, the relative partial dispersion P ^, and the deviation of the relative partial dispersion from the normal ΔΡ ~ τ? ι ·

Here v _Ä »P _n was. ", And A ^ _n . -mi calculated as follows? eg, Ji s, j?

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+ 0.0014832 ν _θ

The glass raw materials, expressed in Mo1%, are melted in the platinum crucible at 1273 K to 1573 K, refined and

Homogenized at 1273 K The melts are poured under IO73 K in preheated molds and cooled in the refrigerator having a temperature of 733 K cooled. The technological conditions can be varied within certain limits, depending on the composition.

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Claims (3)

Experienced in 3prüche 1 »Optical fluorophosphate glass with high positive anomalous partial dispersion, low dispersion and variable, relatively high average refractive index, characterized in that it is melted from the following batch compositions. 5.1 - 30 mol% metaphosphate of Ba and Zn and / or La, 70-94.9 moles of fluoride of Al, Oa and Mg. 2.2 - 40 MON YEARS 2 * Optical H ¹ Iuorophosphatglas according to item 1, characterized in that the fluorides in the batch compositions can be varied as follows: 12-37.8 mol% 11 - 51 MONTHS 3, optical fluorophosphate glass according to item 1, characterized in that for the variation of the optical and technological parameters in addition to the fluorides mentioned in point 2 can be introduced into the glass: