Optical glass convex-concave surfaces: fabrication, application. Lens, magnifying glass

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2018-03-18 07:25:34

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Optical glass is a specially made transparent glass, which is used as parts for optical devices. It differs from the usual purity and high opacity, uniform and colourless. It also strictly rationed dispersion and refractive power. Compliance with such requirements increases the complexity and cost of production.

optical glass

History

You Can find many examples of home use of lenses, e.g., magnifying glass - an ordinary magnifying glass will help to create a small projector from an ordinary smartphone, but the optical glass has appeared not so long ago.

Lenses are known since antiquity, but the first serious attempt to create a glass similar to that used in modern devices can be attributed to the XVII century. Thus, the German chemist, Kunckel in one of his writings mentioned phosphoric and boric acids, the component of glass. He also talked about borosilicate crown that is close to some modern materials. This can be called the first successful experience in manufacturing glass having a defined optical properties and a sufficient degree of physical and chemical homogeneity.

magnifying glass

Industry

Production of optical glass on an industrial scale began in the early nineteenth century. The Swiss Gian together with the Fraunhofer implemented in a factory in Bavaria a relatively stable method of producing such glass. The key to the success was the appointment of melt stirring with a circular motion vertically immersed in a glass clay bar. As a result, it was possible to obtain an optical glass satisfying quality with a diameter up to 250 mm.

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Modern trade

In the obtaining of colored optical glass additives substances with contents of copper, selenium, gold, silver and other metals. It is brewed from the charge. It is loaded in refractory pots, which, in turn, placed in a glass furnace. The composition of the batch may include up to 40% waste glass, the important point is the compliance of the composition of cullet and glass cooking. The glass melt during cooking, continuously stirred with a spatula made of ceramic or platinum. Thus, we achieve a homogeneous state.

Periodically, the melt is taken on a sample on which the quality is controlled. An important step of cooking is the lightness of the glass from chemicals-clarifiers initially added to the composition of the batch, starts the allocation of significant amounts of gases. Formed large bubbles that rise quickly, while grabbing the smaller bubbles are inevitably generated in the cooking process.

In conclusion, the pots are retrieved from the furnace and then slowly cooled. Cooling, slow special moves can last up to eight days. It should be uniform, otherwise the mass can be formed by mechanical stresses that cause cracks.

glass with a convex-concave surfaces

Properties

Optical glass is the material for the production of lenses. They, in turn, are divided by type of collecting and diffusing. To gathering belongs biconvex and PLANO-convex lens, and concave-convex, bearing the name "positive meniscus".

Optical glass has a number of characteristics:

  • Refractive index, which is determined by the two spectral lines called the sodium doublet;
  • The average dispersion, which refers to the difference between the refraction of red and blue spectrum lines;
  • Dispersion coefficient - a number that is set by the ratio of the average dispersion and refraction.

Colored optical glass used for the production of absorbing filters. Depending on material there are three basic types of optical glasses:

  • Inorganic;
  • Plexiglass (organic);
  • Mineral-organic.

The composition of the inorganic glass composed of oxides and fluorides. Quartz optical glass, too, refers to inorganic (chemical formula SiO2). Quartz has a low refraction and high index of light transmission, it is characterized by resistance. A wide range of transparency allows it to be used in modern telecommunications (fiber optic cables, etc.), silicate glass is indispensable in the manufacture of optical lenses, for example, of quartz make a magnifying glass.

PLANO-convex glass lens

Based On silicon

Transparent silica glass can be both an optical and technical. Optic is made by melting rock crystal, the only way you get a fully homogeneous structure. Opaque in the glass for color meet small gas bubbles inside the material.

In Addition to the quartz glass on the base of silicon is produced and the so-called silicon glass, which, despite similar base, has different optical properties. Silicon cells can refract X-rays and to pass infrared radiation.

spectacle lenses with diopters

Organic glass

The So-called Plexiglas on the basis of synthetic polymeric material. This transparent and solid material refers to a thermoplastic and is often used as a substitute for quartz glass. Plexiglass is resistant to many environmental factors such as high humidity and low temperature, but it is much softer and hence more sensitive to mechanical stress. Due to the softness of the organic optical glass just in progress - it could "take" even the simplest tool for cutting metal.

This material is suitable for laser processing, it is easy to apply a pattern or engraving. As the lens he perfectly reflects infrared rays but transmits ultraviolet and x-ray radiation.

Usage

Optical glass is widely used for the manufacture of lenses, which, in turn, are used in many optical systems. A single converging lens used as a magnifying glass. Technique lenses are important or main part of systems such as binoculars, scopes, microscopes, theodolites, telescopes, and cameras and video equipment.

No less important optical glass for the needs of ophthalmology, because without them it is difficult or impossible to correct defects of vision (myopia, astigmatism, hyperopia, violation of accommodation and other diseases). Lenses for glasses with diopters can be made either from quartz glass or high quality plastic.

the manufacture of optical glasses

Astronomy

Optical glass are important and most expensive component of any telescope. Many fans collect the refractors, it requires a little, but most importantly, a PLANO-convex glass lens.

At the beginning of the last century to manufacture a powerful astronomical lens, but rather on its polished, took several years. For example, in 1982 the millionaire Charles Yerkes asked the head of the University of Chicago, William Harper with a request to Finance the Observatory. The Yerkes invested in it about three hundred thousand dollars, and forty thousand went to the purchase of lenses for the most powerful at the time of the telescope on the planet. The Observatory was named in honor of financier Yerkes, and still this refractor with a lens diameter of 102 cm is considered the largest in the world.

The Telescopes with large diameters are reflectors, the mirror is a light-harvesting element.

There is another type of lenses used in astronomy and ophthalmology - glass with a convex-concave surfaces, which is called the meniscus. It can be of two types: scattering and gathering. In a scattering meniscus last part of the thicker Central and thinner collecting is a Central part.

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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

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