company news about In-Depth Look at Lens Materials: The Choice Between Optical Glass and Crystal Lenses

In-Depth Look at Lens Materials: The Choice Between Optical Glass and Crystal Lenses

1. Exploration of Lens Materials

• Advantages and Manufacturing Process of Optical Glass
  Optical glass is a material meticulously formulated from high-purity oxides such as silicon, boron, sodium, potassium, zinc, lead, magnesium, calcium, and barium. It undergoes high-temperature melting in platinum crucibles, followed by ultrasonic stirring to remove bubbles. Subsequently, it requires a prolonged, slow cooling process to prevent internal stress within the glass blocks. Once completely cooled, the glass blocks undergo rigorous measurement using optical instruments to ensure that all indicators, including purity, transparency, uniformity, refractive index, and dispersion, meet requirements. Through high-purity material formulation and refined melting processes, optical glass guarantees its purity and transparency, making it a superior lens material.

• Characteristics and Misconceptions of Crystal Lenses
  Crystal, a large quartz crystalline mineral, also has its unique application in the field of lens manufacturing. Although there are natural and synthetic crystals, those used for eyewear lenses, such as clear crystal, smoky quartz, and amethyst, are carefully selected and processed. Traditional Chinese beliefs about crystal's benefits for the eyes, such as cooling, reducing "heat," and anti-infective properties, lack scientific basis. There is a misconception regarding the protective ability of crystal lenses against ultraviolet (UV) and infrared (IR) rays in sunlight; in reality, they cannot effectively block these harmful rays. Wearing crystal lenses does not protect the eyes or prevent eye diseases.

2. Structural Types and Uses of Lenses

Lens structures come in various types, including single-vision lenses such as spherical, cylindrical, and sphero-cylindrical lenses, as well as multifocal lenses like bifocals, trifocals, and progressive addition lenses. Furthermore, lenses have different purposes, such as vision correction and eye protection. Vision correction lenses include those for myopia, hyperopia, astigmatism, and prisms for presbyopia. Protective lenses include tinted lenses and polarized lenses, each with different functions, such as UV absorption or IR absorption. Lens structures encompass single-vision and multifocal types, and materials include resin, meeting various needs for vision correction and protective functions.

3. Lens Selection Criteria

• Optical Performance and Comfort
  When selecting lenses, several aspects need consideration. Firstly, the optical performance of the lens is crucial as it directly affects visual quality. Secondly, comfort is an undeniable factor, given that lenses are worn for extended periods. Lenses need to possess optical properties like minimal aberrations, thinness, lightness, and high transmittance to enhance visual quality and wearing comfort.

• Safety and Durability
  Additionally, the durability and safety of the lens are equally important, relating to the lens's lifespan and the wearer's safety. The lens's thermal stability, chemical stability, and mechanical strength ensure its durability and safety during wear.

  • Good thermal stability: Maintains stable performance during temperature changes, preventing deformation or breakage due to thermal differences.

  • Stable chemical properties: Resistant to corrosion by chemicals, ensuring long-term quality.

  • Certain mechanical strength: Ensures the lens remains intact upon impact, safeguarding the wearer's safety.

4. Common Lens Materials

• Characteristics and Applications of CR-39
  Allyl diglycol carbonate (CR-39), also known as Columbia Resin, is a thermoset material. It is not only easily tinted and impact-resistant but also possesses good chemical stability. From approximately 1955 to 1960, CR-39 was widely used in the manufacture of ophthalmic corrective lenses, becoming the first generation of ultra-light and impact-resistant plastic lenses. Even today, CR-39 remains the material of choice for producing standard plastic ophthalmic lenses. CR-39 is a thermoset material widely used in lens manufacturing due to its good impact resistance and chemical stability.

• Applications, Advantages, and Disadvantages of PMMA and PC
  Polymethyl methacrylate (PMMA), commonly known as acrylic, is a thermoplastic material. Although it is lightweight, inexpensive, and easy to mold, its application in the eyewear industry is limited due to its tendency to deform under heat and poor abrasion resistance. In optics, PMMA is primarily used for manufacturing low-end sunglass lenses and contact lenses.
  Polycarbonate (PC) is also a thermoplastic material, offering excellent impact resistance and heat resistance. It can absorb ultraviolet radiation below 385nm, ensuring safety. Furthermore, PC is resistant to oil, grease, and acids, has low water absorption, high dimensional stability, and is an environmentally friendly material. Although it has drawbacks like high internal stress, susceptibility to cracking, poor coating adhesion, and being easily scratched, PC material still holds an important position in the optical field. It is commonly used for children's eyewear, sunglasses, protective goggles, and adult eyewear. PMMA is prone to deformation and has poor abrasion resistance, whereas PC offers high impact resistance and heat resistance, making it a common material for protective eyewear.