A pair of good sports sunglasses, with or without polarized lenses, is a feature that everyone generally likes. Polarized lenses can use the principle of polarization to eliminate horizontal light. Only vertical light can enter into the eyes, which filters out the strong light, so that you can see the correction of position, distance, and color of the object that is not affected by glare. If you have to work under strong light or do outdoor activities for long times, wearing a pair of polarized sunglasses will make your eyes less susceptible to fatigue, less stress, and relatively comfortable to use.
Commonly used polarized lenses are made of PC materials, but not only PC materials can be made into polarized lenses. Other common polarized lenses include TAC (Triacetate Cellulose), resin polarized lenses, and glass polarized lenses.
》 TAC (Triacetate Cellulose) Polarized Lenses
TAC is the English abbreviation of cellulose triacetate. It is also a common polarized lens on the market. Due to the relatively low cost of production, the TAC sheet itself is a polarizing film. The TAC polarizing lens is a TAC plastic sheet that is pressed into a polarizing plate. Injection molding with PC lens, thickness is about 0.7mm-1.2mm, thinner than other types of polarized lenses. The lens and hardness are softer, impact resistance is low, and it is easy to be scratched and easy to peel off the film. The big advantage of TAC polarized lenses is that the stress is low (stress: the force per unit area), and most of the polarized lenses seen in casual sunglasses are TAC polarized lenses.
》 PC polarized lenses
The most common polarized lens is PC polarized lens. PC polarized lens forms a polarizing plate by sandwiching a PC plastic sheet outside the polarizing film. It is shot together with the PC lens to form a polarized lens. As a result, the PC polarized lens has higher hardness and thickness, falling between 1.8mm-2.2mm; the advantages are high impact resistance and not afraid of high temperature, the lens is also flexiable, and the safety is relatively improved. But even if the hardness is higher, without careful, it will still scratch the lens. The biggest difference between PC polarized lenses and TAC polarized lenses is that PC polarized lenses have greater stress, and the optical quality also varies with the influence of stress.
》 Resin polarized lenses
It is a high-end polarized lens. The resin lens is an organic material. The polymer lens structure is internal, and it is connected to form a three-dimensional network structure. The structure between molecules is relatively loose, so the light transmittance is as high as 84% -90%. Resin polarized lenses are relatively stable in optical quality due to their special material prices and manufacturing technology. They are usually used in high-end sunglasses or optical glasses. The most famous is Ray-Ban's exclusive polarized lens technology (Ray-Ban P3), which is made of resin that inside two polarized sheets, which used in the difficult curvature of frame, and the surface of P3 lens is equipped with oil-resistant coating by nano-technology, which is very easy maintenance and cleaning.
》 Glass polarized lenses
It is also a high-end polarized lens. Glass is the most scratch-resistant and heat-resistant lens material. It is not easy to deform and cause distortion. Compared with common PC polarized lenses, the impact resistance is much lower. In addition, the glass is fragile. It hardly appears on the products of sports sungalsses and is usually used on optical glasses or fancy casual sunglasses.
Polarized lenses are sandwiched between two lenses by a layer of polarizing film. If the environment is used in harsh environments such as high temperature, high humidity and high salinity, polarizing lenses is higher chance to removing the films than normal lenses. Choose a trusted brand with high quality assurance. The polarized lenses will have proper follow-up treatment even if they are removed, otherwise, you have to be prepared to buy another pair.
Finally, give everyone a little trick to distinguish between PC polarized lenses and TAC polarized lenses:
- Compare the thickness of two lenses. Thin lenses are usually TAC polarized lenses.
- Pick up two pairs of polarized lenses and stack them together to see the lens stress. Thin lenses without or with low stress are usually TAC lenses.
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