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Introduction to Materials for Optical Lens Processing

Optical lenses are transparent optical components that utilize optical phenomena such as reflection, refraction, and absorption to adjust the direction of light propagation, focus, or diffuse light. They are widely used in various fields, including optical instruments and photographic equipment. The choice of raw materials is crucial to the performance and quality of the lenses.

The raw materials for optical lenses mainly include various optical materials, such as colorless optical glass, colored optical glass, infrared optical materials, crystalline materials, vitreous materials, and plastic materials. Among these, optical glass is a key raw material for manufacturing optical lenses, while materials like resins and polycarbonate are also increasingly used in optical lens production.

Colorless Optical Glass typically includes crown glass (e.g., K9) and flint glass. Crown glass like K9 has specific refractive indices and Abbe numbers, characterized by high light transmittance, low dispersion, and excellent optical homogeneity. It is commonly used to manufacture various high-precision optical lenses, such as camera lenses and telescope lenses.

Colored Optical Glass is generally produced by adding specific metal oxides (e.g., iron, cobalt, nickel, chromium, manganese) to adjust the glass color, enhance absorption of specific wavelengths, and improve transparency. Alternatively, rare earth oxides (e.g., neodymium, europium, gallium, terbium, gadolinium, erbium, dysprosium) can be added to improve transparency and quality, enabling functions like spectral separation and filtration. Special dyes can also be used to impart specific colors while maintaining good optical performance.

Colored optical glass can be categorized into cut-off type, selective absorption type, neutral type, and others. For example, cut-off glass is named based on its cut-off wavelength, such as JB490, which denotes golden-yellow glass with a cut-off wavelength of 490 nm.

Infrared Optical Materials, such as those for the mid-infrared band, include common grades like the IRG1XX series (e.g., IRG101, IRG102). Each material has specific parameters like refractive index, density, and transmission band. The naming of infrared optical glass grades typically includes the transmission band and sequence number. For instance, IRG203 denotes infrared optical glass for the far-infrared band with sequence number 03.

Crystalline Materials Processing
For planar optical products, K9 glass is often used to make protective window glass for sensors or viewports. Material selection must consider transmission properties and mechanical performance. Such products are widely used in watch crystals, smartphone cover glass, and equipment windows.

1. Calcium Fluoride (CaF₂):
   Offers excellent transmission from UV (250 nm) to IR (9 μm), commonly used in windows, prisms, and lenses for UV-to-IR spectral applications. Its polished surfaces are highly stable with low absorption, making it suitable for high-power laser systems.

1. Magnesium Fluoride (MgF₂):
   Exhibits purple fluorescence under electro-optical heating. Its crystals provide excellent polarization, especially for UV and IR spectra. Often used in anti-reflective coatings for optical lenses to reduce glare and improve imaging quality.

1. Sapphire:
   Possesses excellent thermal, electrical, and dielectric properties, along with chemical resistance, high-temperature tolerance, good thermal conductivity, high hardness, and IR transparency. Often used as an alternative optical material for components like IR-transmitting windows (e.g., night vision cameras), satellite/space instruments, high-power laser windows, prisms, lenses, UV/IR windows, and cryogenic observation ports. Widely applied in high-precision instruments for aviation and aerospace.

Additionally, crystalline materials like Germanium (Ge) and Silicon (Si), though not "glass" in the traditional sense, play vital roles in optical lens manufacturing. They offer high transparency and excellent physical properties, especially for infrared optical systems.

Coating Materials
Specific raw materials are required during coating processes. The primary purpose of coating is to enhance optical performance—such as increasing transmittance and reducing reflection. Common coating materials include inorganic compounds like silicon oxide and zirconium oxide. These materials provide distinct refractive indices to form interfaces that improve optical properties. Advanced coating techniques can achieve specific optical effects, such as anti-reflection coatings and beam-splitting coatings.

Plastic Materials

• Resins:
  Offer advantages like lightweight, ease of processing, and low cost, making them widely used for eyeglass lenses and camera lenses. Special additives and coatings can enhance their abrasion resistance, scratch resistance, and UV protection.

• Polycarbonate:
  Features high light transmittance, impact resistance, and abrasion resistance. Often used for sports goggles, safety glasses, and other lenses requiring high durability.

In summary, different optical lens materials each have unique advantages and applications. Manufacturers select materials based on lens type, performance requirements, cost, and other factors to ensure high-quality production. With continuous technological advancements and the emergence of new materials, the raw materials and manufacturing processes for optical lenses will keep evolving.