Share: What is the optical lens processing technology?

First, the origin of optical lenses

Optical lenses were originally used to make lenses of glass, is ordinary window glass or wine bottle on the knot, similar to the shape of the "crown", crown glass or crown brand glass name from. The glass at that time was very uneven and frothy. In addition to crown glass, there is another flint glass with a higher lead content. Around 1790, Frenchman Pierre Louis Junard discovered that mixing glass paste could produce glass with a uniform texture. In 1884, Ernst Abbe and Otto Schott of Zeiss founded Schott Glaswerke AG in Jena, Germany, and developed dozens of optical glasses in a few years, among which the invention of high refractive index barium crown glass was one of the important achievements of Schott Glass.

Two, optical lens cold processing process

The first one: milling, is to remove the uneven bubbles and impurities on the surface of the lens,(about 0.05-0.08) to play a forming role.

The second step is the finishing process, the milled lens will eliminate its damage layer and fix the R value.

The third is the polishing process, which is to polish the fine grinding lens again, this process is mainly to make the appearance better.

The fourth step is cleaning, after polishing the lens will clean the polishing powder on its surface. Prevent cracking.

The fifth step is edging, which is to grind the outer diameter of the original lens to the specified outer diameter.

The sixth step is coating, which will need to be coated with one or more layers of colored film or other film on the surface of the coated lens.

The seventh step is inking. It will be necessary to apply a layer of black ink to the edge of the lens to prevent reflection.

The eighth step is gluing, which is to combine two lenses with opposite R-values and the same outer diameter material with glue.

Iii. Optical lens raw material description

Lens materials use transparent media, mainly divided into inorganic and organic two categories. In our daily life, we will also encounter a natural medium crystal lens, which is a lens made of quartz ore. Ancient crystal can nourish the eyes, but in fact the main component of the crystal is silicon dioxide (sio2), the biggest advantage is high hardness and not easy to be damp, but the ultraviolet and infrared transmission rate is high, and the crystal density is not uniform, containing impurities, stripes and bubbles are produced, will form birefringence phenomenon, thereby affecting vision.

1, inorganic material - glass

Glass is a very special amorphous material that appears solid at room temperature, hard but brittle, and sticky at high temperatures. Glass has no fixed chemical structure and therefore no exact melting point. As the temperature rises, the glass material will become soft, viscous, and gradually from solid to liquid, this gradual change of characteristics we call the "glass state". This property means that glass can be processed and moulded at high temperatures. Optical lenses made of glass materials have very good light transmission, more transparent after surface polishing, because of high hardness, easier to process molding, higher precision.

(1) Ordinary glass materials (1.5 and 1.6) : Crown glass with a refractive index of 1.523 is the manufacturing material of traditional optical lenses, of which 60% to 70% is silica, and the rest is mixed by calcium oxide, sodium and boron and other substances.

(2) High refractive index glass materials: After years of research, lens manufacturers have found a way to improve the refractive index of the material while maintaining low dispersion, that is, to add new chemical elements to the glass. As early as 1975, lenses containing titanium were produced, with a refractive index of 1.7 and an Abbe number of 41; Fifteen years later, lanthanide lenses were produced, with a refractive index of 1.8 and an Abbe number of 34; In 1995, a material with a refractive index of 1.9 was added to the element niobium, and the Abbe number was 30, which is the highest refractive index lens material at present. It is widely used in various scientific laboratories and large enterprise R&D institutions for research and development and production in the field of optics.

(3) Stained glass materials: In the glass material mixed into some metal salts with special absorption properties will show the effect of coloring, such as: nickel and cobalt (purple), cobalt and copper (blue), chromium (green), iron, cadmium (yellow), gold, copper and selenium (red) and so on. These dyed lens materials are mainly used in the large-scale production of flat solar lenses or protective lenses. Some light-colored materials with special filterability (brown, gray, green or pink) are also used in the production of corrective lenses.

(4) Photochromic glass materials: photochromic phenomenon is a property that makes the material respond to the intensity of sunlight by changing the light absorption properties of the material. Its basic principle is to make ordinary glass (including plastic photochromic materials) darker under the influence of ultraviolet radiation, and lighter under the influence of ambient high temperature, both processes are reversible, and may always exist. This phenomenon is accomplished by activating molecules of photochromic substances mixed in the material. In 1962, the first generation of photochromic glass materials appeared, and their properties have been continuously improved since then. It is mainly added to the glass material silver halide crystals. These crystals react chemically under ultraviolet radiation, darkening the lenses. The color change principle of the first generation of photochromic glass materials is an electron exchange between silver atoms and chlorine atoms, which is manifested by silver chloride and the surrounding environment. In the absence of light, silver chloride is ionic, because silver ions are transparent, so the lens is also transparent; Under ultraviolet radiation, the unstable electrons leave the chloride ions, combine with the silver ions to form the metal silver and absorb the light, and the lens becomes darker. When the ultraviolet radiation is reduced, the moving electrons leave the silver atoms and return to the chlorine atoms, and the lens gradually returns to its original clear state. For general photochromic glass, the discoloration is also controlled by temperature, and the lower the temperature, the darker the color. Photochromic materials are mostly gray and brown, commonly known as gray and tea change, other colors can also be achieved through a special process. All eye lenses, including melted bifocal lenses and progressive lenses, can be manufactured using photochromic materials. In recent years, the development of photochromic resin lenses is rapid, and the material is constantly improved, and its refractive index is no longer limited to 1.50.

2. Organic materials

Organic materials can be divided into two categories: thermosetting materials, which have the property of hardening after heating, and will not be deformed when heated, and most of the lenses are based on this material, such as CR-39. Thermoplastic material, with the property of softening after heating, especially suitable for thermoplastic and injection molding, polycarbonate PC is such a material.

(1) Thermosetting materials 1) Common resin materials: (CR-39) The scientific name of carbonic acid propylene acetic acid, or allyl Glycol Carbonates, is the most widely used material for the production of common resin lenses. It was discovered by Columbia chemists in the 1940s and is the 39th material in a series of polymers developed by the United States Air Force, hence the name CR-39 (Columbia Resin No. 39). CR-39 was used in the production of corrective lenses for the eye from 1955 to 1960 and is the first generation of ultra-light, impact-resistant resin lenses. As a thermosetting material, CR-39 is a liquid monomer, which is polymerized and cured under the condition of heating and adding catalyst. Polymerization is a chemical reaction in which several monomers of the same molecular structure form a new polymeric molecule with different lengths and properties. As an optical lens, the parameters of the material properties of CR-39 are very suitable: the refractive index of 1.5 (close to ordinary glass lenses), the density of 1.32 (almost half of glass), the Abbe number of 58~59 (only a small amount of color emission), impact resistance, high light transmission, can be dyed and coated. Its main disadvantage is that the wear resistance is not as good as that of glass, and it needs to be coated with anti-wear film. Resin lenses can be modulated to process the curvature of the lens surface, so it is suitable for the production of aspherical lenses.