Flat glasses have windproof and beauty functions, and some can also prevent the influence of ultraviolet rays or infrared rays on the eyes. As far as lens glass materials are concerned, there are white mirrors, color changing mirrors, coating mirrors, crystal mirrors, X-ray mirrors and X-ray mirrors.
Quality characteristics. The lens quality is divided into three grades: high, medium and low, or excellent, first and second. The higher the quality, the stronger the transparency and the more eye protection.
Fake products. Mainly counterfeit, imitate or pass off as imported famous brands and domestic famous products, such as "imitation of history". These products are characterized by poor materials, different background colors, poor processing, low surface finish and inaccurate luminosity; The color of the material is not straight, and there are many impurities such as bubbles and stones inside; Under the stress meter, it can be found that there is a large stress; The packaging is not standardized and there is no qualified mark.
Characteristics of defective products. In addition to some features of the above-mentioned counterfeit products, defective products also include edge chipping, scratches, sand holes, lines and so on. Some lenses are inaccurate in diopter, some lenses have low smoothness, and some lenses have a center thickness of less than 0.7mm, which is fragile and hurts eyes.
Identification method:
1. Identify the surface finish. Under a 60 watt incandescent lamp, it can be distinguished by a black background. High-quality products should not have obvious surface defects, such as scratches, pits, edge cracks, sand holes, water ripples, bubbles and so on.
2. Put the glasses about 33cm in front of your eyes. When you look at an object through glasses, there should be no obvious phenomenon of getting bigger or smaller, and there should be no sense of jumping. Otherwise, there is something wrong with the quality of the glasses.
3. Through instrument identification, it is better to keep the degree of three pieces unchanged and free from sundries.
4. Check whether the trademark, manufacturer and quality certificate are true and reliable. The lens of international famous brand products is often engraved with the manufacturer's trademark, which can be found by carefully observing the edge of the lens.
A bad flat mirror is bad for your eyes!