The development of optical glass

The development of optical glass and that of optical instruments are inseparable. New reforms in optical systems often put forward new requirements for optical glass, thus promoting its development. Similarly, the successful trial production of new types of glass often, in turn, promotes the development of optical instruments.

The earliest optical materials used by people to make optical components were natural crystals. It is said that in ancient Asia, crystal was used as a lens, while in ancient China, natural tourmaline (tea mirror) and citrine were applied. Archaeologists have proved that people in Egypt and us (during the Warring States Period) were already able to make glass about 3,000 years ago. However, the use of glass as glasses and mirrors began in Venice in the 13th century. Engels highly praised this in his "Dialectics of Nature", considering it one of the outstanding inventions of that time. Afterwards, due to the development needs of astronomers and navigation, Galileo, Newton, Descartes and others also made telescopes and microscopes out of glass. Since the 16th century, glass has become the main material for manufacturing optical components.

By the 17th century, achromatic issues in optical systems had become a central problem for optical instruments. At this time, due to the improvement of the glass composition and the introduction of lead oxide into the glass, Hull obtained the first pair of achromatic lenses in 1729. Since then, optical glass has been divided into two major categories: crown glass and flint glass.

In 1768, Ji Nan was the first in France to produce uniform optical glass by stirring with a clay rod, thus beginning to establish an independent optical glass manufacturing industry. In the middle of the 19th century, several developed capitalist countries successively established their own optical glass factories, such as the Para-Muntu Company of France (1872), the Chance Company of Britain (1848), and the Schott Company of Germany (1848), etc.

Optical instruments made great progress in the 19th century. On the eve of World War I, Germany, in order to rapidly develop military optical instruments, demanded to break the limitation of the scarcity of optical glass varieties. At this time, the renowned physicist A Yuan joined the work at Short's Factory. He added new oxides such as BaO, B2O3,ZnO, P2O3, etc. to the glass and studied their influence on the optical constants of the glass. On this basis, types of glass such as barium crown, boron crown and zinc crown were developed, and at the same time, special relative partial dispersion flint glass was also trial-produced. During this period, the variety of optical glass expanded significantly, and thus a relatively complete set of camera and microscope objectives emerged in the field of optical instruments.

Until the 1930s, most of the work was still carried out on the basis of the Short Factory. By 1934, a series of precious glasses had been obtained, such as the German SK-16(620/603) and SK-18(639/555), etc. So far, it can be regarded as a stage in 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 spectrometers, and advanced photographic objectives, new demands emerged for optical glass. At this time, optical glass also saw new developments accordingly. In 1942, Morey of the United States and later scientists from the Soviet Union and Germany successively introduced dilute oxides and dispersed oxides into glass, 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 CTK and TAF, etc. Meanwhile, research on low refractive index and large dispersion glass was also carried out and a series of optical glasses with fluorotitanium silicate systems were obtained, such as Soviet LF-9, LF-12, German F-16 and other varieties.

Due to the fact that various new types of optical glass have more or less defects in processing or application performance, while researching and expanding the field of optical glass, efforts are also made to improve the physical and physicochemical properties of various new types of optical glass. And a lot of work has been done on the production process.

Looking at the above historical development process, it can be predicted that the future development direction of optical glass will be:

① Produce glass with an exceptionally high refractive index;

② Produce glass with special relative partial dispersion;

③ Develop infrared and ultraviolet optical glass;

④ Replace certain undesirable components in glass, such as radioactive THO2, toxic BcO, Sb2O3, etc.

⑤ Enhance the chemical stability of glass;

⑥ Enhance the transparency of glass and prevent it from being stained by radiation.

⑦ Improve the technological process to reduce the price of new types of glass.