Summary of basic knowledge points about glasses
1. Classification of Glasses:
The classification of glasses we usually refer to is mainly based on their uses, which can be divided into: optical glasses (including myopia glasses, astigmatism glasses and reading glasses), sunglasses (including common running sunglasses) and special-purpose goggles.
The basic structure of glasses
Frame: Specifically designed for holding lenses (this part is not available for glasses without frames). Its size is measured by the maximum distance of the horizontal inner diameter.
Temple: Its function is to ensure that the glasses are securely suspended over the ears. Its size is measured by the extended length from the center of the temple hinge to the end of the temple.
Bridge: Connect the two frames into one for easy wearing. Its size is the shortest horizontal distance between the two frames.
Hinge: It is used to connect the frame and the temple of the mirror. When the glasses is worn, the temple of the mirror is open and does not need to be closed. It can be stored later.
The knowledge of spectacle frames
(1) Specifications of spectacle frames:
1. The specifications and dimensions of spectacle frames are as follows:
The size of the Frame: The Odd numbers are from 33 to 59mm, and The Even numbers are from 34 to 60mm;
The size of the Bridge: The Odd numbers are from 13 to 21mm, and The Even numbers are from 14 to 22mm.
The size of the Temple : The Odd numbers are from 125 to 155mm, and The Even numbers are from 126 to 156mm.
2. Representation method:
Box method and reference line method (general glasses size marking)
Example:
56□14-140, this code represents the size of the frame is 56mm, the size of the bridge is 14mm,and the size of the temple is 140mm.
56(the size of the temple) - (represented by the horizontal line method) -14 (the size of the bridge) -135 (the length of the temple)
(2) Classification of eyeglasses:
1.According to the materials and manufacturing processes involved, eyeglass frames can be categorized into four main types: metal frames, non-metal frames, natural material frames, and hybrid frames.
(1) Metal frames:
This kind of frame is commonly referred to as gold frames, are primarily made from three categories of metallic materials: copper alloys, nickel alloys, and precious metals. These materials must possess specific properties such as appropriate hardness, flexibility, elasticity, wear resistance, corrosion resistance, lightweight characteristics, luster, and pleasing coloration. Consequently, most metal frames are fabricated from alloys or feature surface-treated metals to enhance their performance and aesthetics.
(2) Non-metallic materials:
These primarily refer to acetate fiber frames, which can be further categorized into two types: acetate fiber injection-molded frames (commonly known as plastic frames) and acetate fiber sheet frames (commonly known as sheet frames). Acetate fiber frames are characterized by excellent transparency, ease of coloring, polishability, resistance to aging, non-flammability, and good biocompatibility with skin. Plastic frames offer advantages such as a simple manufacturing process, low material consumption, relatively low cost, and the ability to be colored through techniques like dyeing, printing, and spraying. However, they exhibit relatively poor durability, limited plasticity, and inferior ductility. Sheet frames, on the other hand, feature superior smoothness and transparency, an aesthetically pleasing surface finish, enhanced toughness, improved durability, favorable anti-static properties, and excellent skin compatibility without causing allergic reactions. Additionally, they come in a wide range of colors and are available in configurations such as double-layered and triple-layered structures. Nevertheless, the processing of sheet materials is more complex and associated with higher production costs.
(3) Natural materials:
The primary natural materials used in the production of spectacle frames include hawksbill turtle shell, exotic wood, and animal horns.
Among these, wooden and ox horn frames are relatively uncommon.
The most widely recognized type is tortoiseshell frames. Tortoiseshell material is derived from the shells of marine turtles found in tropical oceans, with the main source being the West Indies.
This material offers several advantages, including its lightweight nature, attractive luster, ease of processing and polishing, thermoplastic properties, adhesion under heat and pressure, skin-friendly characteristics, durability, and collectible value. Among all types of spectacle frames, tortoiseshell frames are considered high-end products and are especially favored by middle-aged and older men.
A notable disadvantage is their susceptibility to breakage compared to materials such as celluloid; however, they can be repaired through bonding after damage. To prevent drying, tortoiseshell frames should be displayed immersed in water. Additionally, ultrasonic cleaning should be avoided during maintenance, as it may cause whitening and loss of luster. Due to international protection measures, hawksbill turtles are prohibited from being harvested, resulting in limited supply and high cost. The price of tortoiseshell varies significantly depending on quality, and it can be categorized into three grades based on color: top grade, superior grade, and common grade. Top-grade shells are extremely rare and characterized by pure golden yellow or pink hues. Superior-grade shells exhibit light yellow, light reddish brown, or light coffee tones, while common-grade shells are typically black or dark coffee in color. Lighter-colored tortoiseshell frames are generally preferred.
The Knowledge of spectacle lenses
Lens Material:
(1) Crystal Lens:
A crystal is a natural quartz material primarily composed of silicon dioxide. Colorless and transparent crystals are referred to as crystal, whereas colored variants are known as smoky quartz or brown crystal.
Brown crystal can be further categorized into dark black crystal, medium brown crystal, and light crystal based on the intensity of their coloration. Prior to the development of glass, crystal was predominantly used in the manufacture of eyeglass lenses. However, due to the limited availability of naturally occurring materials, only a small number of such lenses could be produced. In modern times, artificial crystal is widely manufactured through synthetic processes. Artificially synthesized crystal offers advantages such as high purity, minimal structural defects, excellent optical properties, and improved production efficiency, which significantly lowers the cost of crystal-based lenses. Typically, synthetic crystal is colorless and transparent. Through treatments such as laser or X-ray exposure, it can develop a brown tint. Additionally, there are distinctions between single-sided and double-sided treated varieties. Crystal is relatively dense and possesses high hardness, making it difficult to process. Furthermore, its ability to absorb infrared and ultraviolet radiation is inferior to that of glass. Natural crystal often exhibits birefringence, material inconsistency, and higher costs. Consequently, as a lens material, crystal is increasingly being replaced by glass and plastic alternatives.
(2) Glass Sheets:
Glass sheets are categorized into clear glass sheets, colored glass sheets, high refractive index sheets, and photochromic sheets.
Clear Glass Sheets: These have a light transmittance is at least 91%, and they do not absorb ultraviolet radiation. They exhibit excellent chemical and thermal stability.
Colored Glass Sheets: These are produced by adding various colorants to colorless optical glass, resulting in a range of colors such as gray, green, blue, red, and yellow. Colored glass sheets are primarily used for eye protection, shielding the eyes from harmful rays.
High Refractive Index Sheets: Also referred to as "ultra-thin sheets," these lenses feature a shallower curvature at the same diopter level, resulting in a thinner lens. They are especially suitable for the manufacturing and processing of high-diopter lenses.
Photochromic Sheets: Also known as photochromic glass sheets, these are lenses that change color in response to light intensity. Photosensitive agents such as silver halide, copper halide, or chromium halide are added to standard optical glass based on specific requirements. After exposure to light, these lenses can transition to different shades, including brown, brown-gray, and gray.
(3)Plastic sheets
commonly referred to as optical plastics or optical resins, are high-molecular-weight organic compounds manufactured through processes such as molding, casting, and injection molding. The primary advantage of plastic lenses is their high impact resistance. Even in the event of breakage, the resulting fragments are less sharp compared to those of glass, thereby offering enhanced safety. Commonly used types include acrylic, CR-39, and polycarbonate (PC).
