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optical glass

[guāng xué bō li]

Glass type

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Can change the propagation direction of light, and can change the relative of ultraviolet, visible or infrared light Spectral distribution Glass. In a narrow sense, optical glass refers to Colorless Optical Glass ； The generalized optical glass also includes colored optical glass Laser glass 、 quartz Optical glass Radiation resistant glass , ultraviolet infrared optical glass, fiber optical glass, acousto-optic glass, magneto-optical glass and light Photochromic glass 。 Optical glass can be used to make lenses, prisms, mirrors and windows in optical instruments. The components made of optical glass are the key components in optical instruments.^[1]

Chinese name: optical glass
Foreign name: Optical Glass
Purpose: Changing the direction of light propagation

Nature: Glass
Definition: Glass used in the field of optics
Application: Lens, prism, etc. in optical instruments

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eleven development
twelve rare earth element

concept

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Light transmitting Amorphous state (glassy) optical medium material. Can be used to make Prism , lens, filter and other optical elements, which can change the propagation direction, phase and intensity of light after passing through. According to different requirements, optical glass can be divided into three categories: ① Colorless optical glass, which is almost transparent in a wide range of visible and near-infrared bands, is the most widely used optical glass. According to the difference of refractive index and dispersion, there are hundreds of brands, which can be divided into two varieties, namely Mian optical glass (represented by K) and flint optical glass (represented by F). Crown glass is borosilicate glass, which becomes flint glass after adding alumina. The main difference between the two is that the refractive index and dispersion of flint glass are both large, so spectral elements are mostly made of it. ② Radiation resistant optical glass has various properties of colorless optical glass, and can basically not change the performance under radioactive irradiation. The type and brand of optical instrument used for γ irradiation are the same as those of colorless optical glass. Its chemical composition is to add a small amount of cerium dioxide on the basis of colorless optical glass to eliminate the color center formed by high-energy radiation in the glass, so that the light absorption of such glass changes little after irradiation. ③ Colored optical glass having specific absorption or transmission properties for certain wavelengths of light. Also known as filter glass, there are more than 100 varieties. The color filter can selectively absorb certain colors, while the neutral filter can absorb all wavelengths of light the same, just reducing the beam intensity without changing its color. The interference filter is based on the interference principle of light, reflecting unwanted colors instead of absorbing them.

In recent years, some new types of optical glass have been developed, such as glass with good infrared and ultraviolet transmittance; Glass with extremely high or low refractive index or dispersion; Glass that changes color with light intensity; Magneto optic glass in which the polarization plane rotates when light passes through the glass along the direction of magnetic force line; The electro-optic glass that produces birefringence under the action of an external electric field, etc.

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Optical glass is the foundation and important part of photoelectric technology industry. Especially after the 1990s, with the continuous integration of optics, electronic information science and new material science, the application of optical glass, as the basic material of optoelectronics, in the three fields of optical transmission, optical storage and optoelectronic display has made rapid progress, becoming one of the basic conditions for the development of social informatization, especially optoelectronic information technology.

With the sustained and stable development of the domestic economy, China's optical glass manufacturing industry has developed rapidly. According to the data of the National Bureau of Statistics, in 2010, the number of enterprises above designated size in the optical glass manufacturing industry reached 246, and the annual sales revenue of the industry was 23.405 billion yuan, up 53.70% year on year; The profit was 1.537 billion yuan, up 87.10% year on year; The asset scale reached 26.45 billion yuan, up 77.49% year on year. As the optical glass manufacturing industry is dominated by domestic sales, the impact of the financial crisis is relatively small, and the industry still shows a good growth momentum.

Product Introduction

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optical glass

Glass material used for manufacturing lenses, prisms, mirrors, windows, etc. of optical instruments or mechanical systems. It includes colorless optical glass (usually referred to as optical glass), colored optical glass, radiation resistant optical glass, radiation resistant glass and optical quartz glass. Optical glass has high transparency, high uniformity in chemistry and physics (structure and performance), and specific and accurate optical constants. It can be divided into silicate, borate, phosphate, fluoride and chalcogenide series. There are many varieties, and they are mainly classified according to their positions in the refractive index (nD) - Abbe value (VD) diagram. Traditionally, various glasses with nD>1.60, VD>50 and nD<1.60 and VD>55 are classified as crown (K) glass, and other types of glasses are classified as flint (F) glass. Crown glass is generally used as convex lens and flint glass as concave lens. Generally, crown glass belongs to alkali containing borosilicate system, light crown glass belongs to aluminosilicate system, heavy crown glass and barium flint glass belong to alkali free borosilicate system, and most flint glass belongs to lead potassium silicate system. With the continuous expansion of the application field and variety of optical glass, its composition almost includes all elements in the periodic table.

An inorganic glassy material that transmits light through refraction, reflection, transmission, or changes the intensity or spectral distribution of light through absorption. It has stable optical properties and high optical uniformity.

Optical classification

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Colorless Optical Glass

It has special requirements for optical constants, and has the characteristics of high transmittance in the visible area, no selective absorption and coloring. By Abbe

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The number can be divided into coronal glass and flint glass, and each type can be divided into several types according to the refractive index and arranged in order according to the refractive index. It is often used as a lens, prism, reflector, etc. for telescopes, microscopes, cameras, etc.

Radiation proof optical glass

It has a large absorption capacity for high-energy irradiation, including high lead glass and CaO-B2O2 system glass. The former can prevent gamma ray and X-ray irradiation, and the latter can absorb slow neutrons and thermal neutrons, which are mainly used in nuclear industry, medical field, etc. as shielding and peeping window materials.

Irradiation resistant optical glass

Under certain γ - ray and X-ray irradiation, the transmittance of visible area changes less, and the type and brand are the same as those of colorless optical glass. It is used to manufacture optical instruments and peep windows under high-energy irradiation.

Colored optical glass

Also called filter glass. It has selective absorption and transmission performance for specific wavelengths in the ultraviolet, visible and infrared regions. According to the spectral characteristics, it can be divided into three types: selective absorption type, cut-off type and neutral gray; According to the coloring mechanism, it can be divided into ion coloring, metal colloid coloring and sulfur selenide coloring, which are mainly used to manufacture filters.

Ultraviolet and infrared optical glass

It has specific optical constant and high transmittance in the ultraviolet or infrared wave band, and is used as ultraviolet and infrared optical instruments or window materials.

Optical quartz glass

With silica as the main component, it has the characteristics of high temperature resistance, low expansion coefficient, high mechanical strength, good chemical performance, etc. It is used to manufacture prisms, lenses, windows, reflectors, etc. with special requirements for transmission of various wavebands. In addition, there are photomask plates, liquid crystal display panels, and image disc base sheet glass for large-scale integrated circuit manufacturing; Magneto optic glass in which the polarization plane rotates when light passes through the glass along the direction of magnetic line of force; When the light passes through the glass transmitting ultrasonic waves in a certain direction, the acousto-optic glass will diffract, reflect, converge or shift optical frequency.

Dispersion classification

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According to dispersion, it can be divided into two categories: coronal category (K) with small dispersion and flint category (F) with large dispersion.

① Crown like optical glass can be divided into fluorine crown (FK), light crown (QK), phosphorus crown (PK), heavy phosphorus crown (ZPK), crown (K), heavy crown (ZK), barium crown (BaK), lanthanum crown (LaK), titanium crown (TiK) and special crown (TK).

② Firestone optical glass can be divided into light flint (QF), flint (F), heavy flint (ZF), barium flint (BaF), heavy barium flint (ZBaF), lanthanum flint (LaF), heavy lanthanum flint (ZLaF), titanium flint (TiF), crown flint (KF) and special flint (TF). They are in the refractive index n D and dispersion coefficient v The relational images of are distributed in different fields.

Radiation resistance

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optical glass

Radiation resistant glass is a kind of generalized optical glass. include Radiation proof glass And radiation resistant glass. Anti radiation glass is mainly glass with greater absorption capacity for γ - ray and X-ray. When gamma rays or X-rays enter the protective glass, due to the photoelectric effect generated in the glass, the positive and negative electron pairs are generated, and the excited state and free state electrons are generated at the same time, the energy of the emitted gamma rays or X-rays is reduced, and the penetration is reduced, playing a protective role.

When the density of anti radiation glass increases, the shielding capacity increases accordingly. The density of anti gamma ray glass is usually not less than 4.5g/cm. In recent years, glass with density of 6.2~6.5g/cm has been used, and ZF series is commonly used.

Radiation resistant optical glass mainly refers to the optical glass that is not easy to be colored under the action of gamma rays. The designation of radiation resistant optical glass is still based on the optical glass designation, indicating the number of roentgen that can withstand radiation. For example, the optical constant of K509 radiation resistant optical glass is the same as K9, and it can withstand 10 roentgen doses of gamma rays. Ordinary glass generates free electrons after being radiated by high-energy rays, which combine with the vacancy inside the glass to form a color center. At the same time, it can also shift the atomic nucleus, destroy the normal structure, and also produce color centers, which can color the glass.

Formula ①

CeO2 is introduced into radiation resistant optical glass. After high-energy gamma ray irradiation, electrons can be trapped due to formula ①, so that no color center is generated inside the glass, and the absorption band of Ce and Ce is in the ultraviolet region. When the content of CeO2 is too high, the absorption band in the ultraviolet and infrared light extends to the visible light area, which increases the absorption in the blue area of the visible light, causing the glass to be yellow. At the same time, the color will also be deepened due to the influence of other components in the glass, so the content of CeO2 cannot be too high. The content of CeO2 in K509 is about 0.4%~0.5%, and that in K709 is about 1%.

Manufacturing materials

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optical glass

With high quality Quartz sand It is the primary material. Add auxiliary materials properly. Due to the high refractive index, low dispersion and good chemical stability of rare earth, optical glass can be produced and used to manufacture lenses of advanced optical instruments such as advanced cameras, cameras, telescopes, etc. For example, a kind of lanthanum glass with excellent optical properties containing lanthanum oxide lao 360% and boron oxide b2o 340% is an indispensable optical material for manufacturing lenses of advanced cameras and periscopes. In addition, the radiation proof glass can be produced by utilizing the radiation proof characteristics of some rare earth elements.

Production method

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The raw materials for producing optical glass are some oxides, hydroxides, nitrates and carbonates, and phosphate or fluoride are introduced according to the requirements of the formula. In order to ensure the transparency of glass, the content of coloring impurities must be strictly controlled, such as iron, chromium, copper, manganese, cobalt, nickel, etc. The ingredients shall be accurately weighed and evenly mixed. The main production processes are smelting, forming, annealing and inspection.

optical glass

① The smelting includes single crucible intermittent smelting method and tank furnace (see kiln) continuous smelting method. The single crucible smelting method can be divided into clay crucible smelting method and platinum crucible smelting method. Whichever smelting method is used, the mixer shall be used for mixing, and the temperature and mixing shall be strictly controlled to make the glass liquid highly uniform. Clay crucible can smelt most crown glass and flint glass with low cost, and is used when the melting temperature of glass exceeds the service temperature of platinum. Platinum crucibles can smelt glass with high quality and serious erosion to clay crucibles, such as heavy crown, heavy barium flint, rare earth glass and fluorophosphate glass. Platinum crucible is heated by electricity, generally using silicon carbide rod or silicon molybdenum rod electric furnace. However, high frequency heating can be used to produce glass with high crystallization tendency, rapid cooling and certain requirements for atmosphere.

Since the 1960s, countries have successively adopted continuous tank furnace smelting with platinum lining, which has greatly improved the output and quality of optical glass. This is the main trend of the development of optical glass production technology.

② The forming methods of forming optical glass include classical breaking method, rolling method and pouring method, but at present, leakage molding (using single crucible or continuous melting to flow out the feed liquid) is more and more widely used, which can directly pull the rod, drop the material and press or leak the material to form large sized blanks, and improve the utilization rate of material drops and product yield.

③ Annealing In order to eliminate the internal stress of the glass to the maximum extent and improve the optical uniformity, it is necessary to establish a strict annealing system for precision annealing.

④ The indexes tested include: optical constant, optical uniformity, stress birefringence, stripes, bubbles, etc.

quality requirement

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optical glass

The difference between optical glass and other glasses is that as a part of optical system, it must meet the requirements of optical imaging. Therefore, the judgment of optical glass quality also includes some special and strict indicators. There are the following requirements for optical glass: I. Consistency of specific optical constants and optical constants of the same batch of glass

Each type of optical glass has specified standards for light of different wavelengths Refractive index The numerical value can be used as the basis for optical designers to design optical systems. Therefore, the optical constants of the optical glass produced in the factory must be within a certain allowable deviation range of these values, otherwise the actual image quality will not conform to the expected results in the design and affect the quality of the optical instrument. At the same time, because the same batch of instruments are often made of the same batch of optical glass, in order to facilitate the unified calibration of instruments, the allowable deviation of the refractive index of the same batch of glass is more strict than their deviation from the standard value.^[2]

2、 High transparency

The imaging brightness of the optical system is proportional to the transparency of the glass. The transparency of optical glass to light of a certain wavelength is expressed by the light absorption coefficient K λ. After light passes through a series of prisms and lenses, part of its energy is lost in the interface reflection of optical parts and the other part is absorbed by the medium (glass) itself. The former increases with the increase of glass refractive index, which is very large for high refractive index glass. For example, the light reflection loss of one surface of heavy flint glass is about 6%. Therefore, for optical systems containing multiple thin lenses, the main way to improve the transmittance is to reduce the reflection loss of the lens surface, such as coating the surface antireflection coating. For large optical components such as the objective lens of an astronomical telescope, the transmittance of the optical system is mainly determined by the light absorption coefficient of the glass itself due to its large thickness. By improving the purity of glass raw materials and preventing any colored impurities from mixing in the whole process from batching to smelting, the light absorption coefficient of glass can generally be less than 0.01 (that is, the light transmittance of glass with a thickness of 1cm is greater than 99%).

Cold working

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A kind of super hard fireproof glass that uses chemical vapor phase heat treatment and a single piece of soda lime silicate glass to change its original molecular structure without affecting the original color and transmittance of the glass, so that it can reach the super hardness standard and meet the fire protection requirements under the impact of high temperature flame, and its manufacturing method and special equipment. It is made of the following components in weight ratio: potassium salt vapor (72% ～ 83%), argon (7% ～ 10%), gaseous copper chloride (8% ～ 12%), nitrogen (2% ～ 6%). It includes the following process flow: cutting with soda lime silicate glass as the substrate, cold processing of fine grinding → chemical vapor heat treatment of soda lime silicate glass after cold processing → coating the surface of soda lime silicate glass with fire protection film → special physical tempering treatment of soda lime silicate glass surface. The special thermal decomposition gasification equipment is composed of the cylinder body, the cylinder head which is sleeved with the cylinder body, and the reaction kettle which is integrally connected with the cylinder head.

development

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The development of optical glass and optical instruments are inseparable. The new reform of optical system often puts forward new requirements for optical glass, thus promoting the development of optical glass. Similarly, the successful trial production of new types of glass also often promotes the development of optical instruments in turn.

The optical material that was first used to make optical parts was natural crystal. It is said that ancient Asia used crystal as lens, while in ancient China natural tourmaline (tea mirror) and topaz were used. Archaeologists have proved that people in Egypt and us (during the Warring States Period) were able to make glass 3000 years ago. But glass as glasses and mirrors began in Venice in the 13th century. Engels once spoke highly of this in his "dialectics of nature", thinking it was one of the outstanding inventions at that time. Since then, Galileo, Newton, Descartes and others have also made telescopes and microscopes out of glass due to the development needs of astronomers and navigation. Since the 16th century, glass has become the main material for manufacturing optical parts.

In the 17th century, achromatism of optical systems became the central problem of optical instruments. At this time, due to the improvement of glass composition and the introduction of lead oxide into the glass, Hull obtained the first achromatic lens in 1729. Since then, optical glass has been divided into two categories: crown glass and flint glass.

In 1768, Ji Nan first made uniform optical glass in France by mixing clay rods, thus establishing an independent optical glass manufacturing industry. In the middle of the 19th century, several developed capitalist countries have established their own optical glass factories, such as Parra Mento (France) (1872), Chase (England) (1848), Schott (Germany), etc.

Optical instruments developed greatly in the 19th century. On the eve of the First World War, in order to rapidly develop military optical instruments, Germany demanded to break the limitation of the poor variety of optical glass. At this time, the famous physicist A Yuan took part in the work of Schott Factory. He added new oxides such as BaO, B2O3, ZnO, P2O3, etc. to the glass, and studied its influence on the optical constants of the glass. On this basis, barium crown, boron crown, zinc crown and other types of glass have been developed, and flint glass with special relative partial dispersion has also been trial produced. During this period, the variety of optical glass has been greatly expanded, so there are more complete cameras and microscope objectives in optical instruments.

Until the 1930s, most of the work was still carried out on the basis of Xiaote Plant. By 1934, a series of re crowned glasses were obtained, such as German SK-16 (620/603) and SK-18 (639/555). So far, it can be considered as a stage of the development of optical glass.

Before and after World War II, with the development of various optical instruments, such as aerial photography, ultraviolet and infrared spectroscopic instruments, and advanced photographic objectives, new needs for optical glass have arisen. At this time, the optical glass also has a corresponding new development. In 1942, American Morey and later Soviet Union and German scientists introduced rare earth and rare oxide into the glass successively, thus expanding the variety of glass and obtaining a series of optical glasses with high refractive index and low dispersion, such as German LaK, LaF, Soviet Union CTK and Т∨Ф series. At the same time, the research on low refractive index and large dispersion glasses has also been carried out and a series of optical glasses of fluotitanosilicate system have been obtained, such as the Soviet Union's лФ - 9, лФ - 12, Germany's F-16 and other varieties.

Since various new types of optical glass have more or less defects in processing or use performance, while expanding the field of optical glass, we also aim to improve the physical and physicochemical properties of various new types of optical glass. And production process.

From the above historical development process, it can be predicted that the future development direction of optical glass is:

① Making glass with high refractive index;

② Making glass with special relative partial dispersion;

③ Develop infrared and ultraviolet optical glass;

④ Replace some bad components in glass, such as radioactive THO2, toxic BcO, Sb2O3, etc;

⑤ Improve the chemical stability of glass;

⑥ Improve the transparency of glass and prevent the radiation coloring of glass;

⑦ Improve the process and reduce the price of new types of glass.

rare earth element

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In the 1930s, new rare earth element optical glasses appeared, mainly composed of oxides of lanthanum, thorium and tantalum. Rare earth element optical glass has high refractive index, which opens up new possibilities for the design of optical lens. Today's large aperture lenses mostly contain lanthanum glass. Thorium glass production has stopped because of radioactivity. Lead free optical glass

Lead free optical glass does not contain lead and arsenic, and is marked with N.

Optical glass classification

Glasses with similar chemical composition and optical properties are also distributed in adjacent positions on the Abbe diagram. Abbe diagram has a set of straight lines and curves, which divide Abbe diagram into many areas and classify optical glass; For example, crown glass K5, K7 and K10 are in Zone K, and flint glass F2, F4 and F5 are in Zone F. Symbols in glass names:

F stands for flint

K stands for the crown plate

B represents boron

BA for barium

LA stands for lanthanum

N represents lead-free

P stands for phosphorus

Physical parameters of optical glass

Vd Abbe number four significant digits

Nd refractive index seven significant digits

Ve four significant digits

Ne Seven significant digits