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Optical glass
Optical glass refers to a quality of glass suitable for the manufacture of optical systems such as optical lenses, prisms or mirrors. Unlike window glass or crystal, whose formula is adapted to the desired aesthetic effect, optical glass contains additives designed to modify certain optical or mechanical properties of the glass: refractive index, dispersion, transmittance, thermal expansion and other parameters. Lenses produced for optical applications use a wide variety of materials, from silica and conventional borosilicates to elements such as germanium and fluorite, some of which are essential for glass transparency in areas other than the visible spectrum.
Various elements can be used to form glass, including silicon, boron, phosphorus, germanium and arsenic, mostly in oxide form, but also in the form of selenides, sulfides, fluorides and more. These materials give glass its characteristic non-crystalline structure. The addition of materials such as alkali metals, alkaline-earth metals or rare earths can change the physico-chemical properties of the whole to give the glass the qualities suited to its function. Some optical glasses use up to twenty different chemical components to obtain the desired optical properties.
In addition to optical and mechanical parameters, optical glasses are characterized by their purity and quality, which are essential for their use in precision instruments. Defects are quantified and classified according to international standards: bubbles, inclusions, scratches, index defects, coloring, etc.
The earliest known optical lenses, dating from before 700 BC, were produced under the Assyrian Empire: they were made of polished crystals, usually quartz, rather than glass.
It wasn't until the rise of the Greeks and Romans that glass was used as an optical material. They used it in the form of spheres filled with water to make lenses for lighting fires (burning glass), as described by Aristophanes and Pliny, or to make very small, indistinct characters larger and sharper (magnifying glass), according to Seneca.
Although the exact date of their invention is not known, glasses are said to have been described in 1299 by Sandro di Popozo in his Treatise on Family Conduct: "I am so altered by age, that without these lenses called spectacles, I would no longer be able to read or write. They have recently been invented for the benefit of poor old people whose eyesight has become bad". At the time, however, "glasses" were actually made from beryl or quartz.
The only lens available at the time, ordinary soda-lime glass, was unable to compensate for optical aberrations. However, it evolved slowly over the centuries. It was first lightened by the use of ashes, which contain manganese dioxide that transforms ferrous oxide (FeO) into ferric oxide (Fe2O3), which is much less colorful. Then, around 1450, Angelo Barovier invented "crystalline glass" (vetro cristallino) or "Venetian glass" (cristallo di Venezia), improving on the previous process by purifying the ashes by leaching to obtain a purer potash. Lime was introduced, first for economic reasons in the 14th century, then as a technical improvement in Bohemia in the 17th century (Bohemian glass), eliminating a very large proportion of impurities. This practice did not arrive in France until the middle of the eighteenth century. It was at this time that the Manufacture Royale de Glaces de Miroirs (Compagnie de Saint-Gobain S.A.) began to produce glass composed of 74% silica, 17.5% soda and potash, and 8.5% lime.
Thus, the first complex optical instruments, such as Galileo's telescope (1609), used ordinary soda-lime glass (the first crown glass), composed of sand, soda, potash and sometimes lime, which, although suitable for glazing or bottles, was hardly suitable for optical applications (distortion, blurred effect, irregularities, etc.). In 1674, the British inventor George Ravenscroft, wishing to rival Venetian and Bohemian crystal while being less dependent on imported raw materials, replaced lime with lead(II) oxide to compensate for glass's lack of resistance to humidity, thus inventing lead crystal (the first flint glass, named after the high-purity English siliceous stone used), brighter than ordinary glass, composed of silica, lead oxide and potash.
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Optical glass AI simulator
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Optical glass
Optical glass refers to a quality of glass suitable for the manufacture of optical systems such as optical lenses, prisms or mirrors. Unlike window glass or crystal, whose formula is adapted to the desired aesthetic effect, optical glass contains additives designed to modify certain optical or mechanical properties of the glass: refractive index, dispersion, transmittance, thermal expansion and other parameters. Lenses produced for optical applications use a wide variety of materials, from silica and conventional borosilicates to elements such as germanium and fluorite, some of which are essential for glass transparency in areas other than the visible spectrum.
Various elements can be used to form glass, including silicon, boron, phosphorus, germanium and arsenic, mostly in oxide form, but also in the form of selenides, sulfides, fluorides and more. These materials give glass its characteristic non-crystalline structure. The addition of materials such as alkali metals, alkaline-earth metals or rare earths can change the physico-chemical properties of the whole to give the glass the qualities suited to its function. Some optical glasses use up to twenty different chemical components to obtain the desired optical properties.
In addition to optical and mechanical parameters, optical glasses are characterized by their purity and quality, which are essential for their use in precision instruments. Defects are quantified and classified according to international standards: bubbles, inclusions, scratches, index defects, coloring, etc.
The earliest known optical lenses, dating from before 700 BC, were produced under the Assyrian Empire: they were made of polished crystals, usually quartz, rather than glass.
It wasn't until the rise of the Greeks and Romans that glass was used as an optical material. They used it in the form of spheres filled with water to make lenses for lighting fires (burning glass), as described by Aristophanes and Pliny, or to make very small, indistinct characters larger and sharper (magnifying glass), according to Seneca.
Although the exact date of their invention is not known, glasses are said to have been described in 1299 by Sandro di Popozo in his Treatise on Family Conduct: "I am so altered by age, that without these lenses called spectacles, I would no longer be able to read or write. They have recently been invented for the benefit of poor old people whose eyesight has become bad". At the time, however, "glasses" were actually made from beryl or quartz.
The only lens available at the time, ordinary soda-lime glass, was unable to compensate for optical aberrations. However, it evolved slowly over the centuries. It was first lightened by the use of ashes, which contain manganese dioxide that transforms ferrous oxide (FeO) into ferric oxide (Fe2O3), which is much less colorful. Then, around 1450, Angelo Barovier invented "crystalline glass" (vetro cristallino) or "Venetian glass" (cristallo di Venezia), improving on the previous process by purifying the ashes by leaching to obtain a purer potash. Lime was introduced, first for economic reasons in the 14th century, then as a technical improvement in Bohemia in the 17th century (Bohemian glass), eliminating a very large proportion of impurities. This practice did not arrive in France until the middle of the eighteenth century. It was at this time that the Manufacture Royale de Glaces de Miroirs (Compagnie de Saint-Gobain S.A.) began to produce glass composed of 74% silica, 17.5% soda and potash, and 8.5% lime.
Thus, the first complex optical instruments, such as Galileo's telescope (1609), used ordinary soda-lime glass (the first crown glass), composed of sand, soda, potash and sometimes lime, which, although suitable for glazing or bottles, was hardly suitable for optical applications (distortion, blurred effect, irregularities, etc.). In 1674, the British inventor George Ravenscroft, wishing to rival Venetian and Bohemian crystal while being less dependent on imported raw materials, replaced lime with lead(II) oxide to compensate for glass's lack of resistance to humidity, thus inventing lead crystal (the first flint glass, named after the high-purity English siliceous stone used), brighter than ordinary glass, composed of silica, lead oxide and potash.