Lenses polishing

In the classical polishing process the surface is smoothed to a mirror level, so that specular reflections can occur on opaque surfaces and be perceived as luster or gloss. In case of transparent materials, such as lenses, polishing minimizes the amount of incident light physically scattered by asperities and small defects. In both mentioned... 

Use of Duboscq-type colorimeter. The colorimeter must be kept scrupulously clean. The cups and plungers are rinsed with distilled water and either dried with soft lens-polishing material or rinsed with the solution to be measured. 

Cast molding is an increasingly used manufacturing process for both rigid gas-permeable and hydrogel contact lenses. In this process, two molds, made from a variety of plastics, are used. A female mold forms the lens front surface (convex) and a male mold forms the lens back surface (concave). The plastic molds are made from metal tools or dies that are usually stainless steel, precision lathed, and polished to the specified lens design. A variety of mold materials are used. The polymerized, hardened lens is released from the mated molds and is processed in much the same way as the spin-cast lenses described above. 

This system consists of a symmetrical pair of lens elements connected by a small volume of liquid. Each lens consists of a single spherical interface between the liquid and a lens rod. The lens element is formed by polishing a small concave spherical surface in the end of a sapphire rod. At the opposite end of the rod, a thin film piezoelectric transducer is centered on the axis of the lens surface. 

Aside from the basic approach to polishing, the most critical component of a CMP tool is the wafer earrier. As with CMP tools, wafer carriers have evolved from roots in lens grinding and in the silicon wafer polishing industries to meet requirements specific to polishing silicon-based integrated circuits. 

High polishing speeds are essential in todays economy, and the latest equipment employs much higher spindle speeds and pressures than those used just a few years ago. Cerium oxide is ideal under these more modern conditions, A spherical lens that required 8 minutes to polish 15 years ago is now polished in less than one minute, A toric (cylinder) lens that previously took 15 minutes to polish, now requires 4-1/2 minutes. 

For use in infrared optics, zone-refined germanium is recast or grown into forms suitable for lens and window manufacture. Polycrystalline castings of up to 115 kg and single crystals of up to 90 kg are routinely made. After the germanium is annealed, it is cut and ground into lens- or window-blanks, which are then polished, coated, and assembled into an ir system (see Infrared and raman spectroscopy, infrared technology). 

The condensing lens focuses the incident light to a beam width of about 0.08 mm inside the sample, contained between two highly polished fused silica windows and a Teflon spacer. The volume of the measuring cell is 150/d, but the sample volume participating effectively in the scattering amounts to only about 0.1 1. 

Black coral can take a high polish, but in some species it retains a natural sheen, and, viewed through a lOx lens, displays a structure of tiny bubble-like bumps on the surface. 

In polishing glass for optical use, the lens crafter is primarily interested in smoothing the surface. There have been several proposed mechanisms by which the glass surface is made smooth during polishing as reviewed by Holland and Izumitani. These... 

In the field of optics, a lens is a device used for focusing or defocusing a beam of light. It is commonly formed from a disk-shaped blank of transparent material, such as glass, plastic, or fused quartz both sides are ground and polished, with at least one surface being polished with a curve. The word lens is derived from the Latin word for lentil, since the shape of a lens resembles the curved surface of a lentil bean. 

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