Optical lens wear and material refractive index
Whether it is an optical lens made of inorganic or organic material, in daily use, friction with dust or grit (silicon oxide) will cause the lens to wear and scratches on the surface of the lens. In contrast, lenses made of organic materials have lower hardness and are more prone to scratches.
There are two main types of scratches on the surface of the lens that can be observed through a microscope. One is scratches caused by grit, which are shallow and small and generally not easy to detect; the other This kind of scratches are caused by larger grit, deep and rough, in the central area, which will affect the wearing effect of the lens.
The most fundamental way to judge and test the abrasion resistance of the anti-wear film is to use clinically, let the wearer wear the lens for a period of time, and then observe the wear of the lens with a microscope Happening. At present, the relatively quick and intuitive optical lens testing method is:
frosting test, the lens is placed in a container with gravel, and the grain size and hardness of the gravel are specified. Control the friction back and forth. After the end, use a haze meter to test the amount of diffuse reflection of light before and after the lens is rubbed, and compare it with the standard lens.
steel wool test, this method uses a prescribed steel wool, under a certain pressure and speed, rubs a certain number of times on the surface of the lens, and then uses it again The haze meter measures the amount of diffuse reflection of light before and after the lens is rubbed, and compares it with the standard lens.
Of course, we can rub the two lenses the same number of times with the same pressure, and then observe and compare them with the naked eye. The results of these two test methods are relatively close to the clinical results of long-term wear by the wearer.
Optical lenses include magnifier optical lenses, binoculars, door mirrors, jewellery mirrors, instrumentation lenses, medical glass lenses, car wash lights, etc. Various lenses have different functions and uses Different. The magnifying glass lens is a simple visual optical device used to observe the details of the object. It is a convergent lens with a focal length much smaller than the photopic distance of the eye. The size of an object imaged on the retina of the human eye is proportional to the angle (angle of view) the object opens to the eye.
A telescope is an optical instrument that uses concave and convex lenses to observe distant objects. The light passing through the lens is refracted or the light is reflected by the concave mirror to make it enter the small hole and converge to form an image, and then pass through a magnifying eyepiece to be seen.
The material purchase parameter of the lens is based on the refractive index, which determines the price of the lens. The following is a list and a brief description of the refractive index. We only focus on the domestic brand lenses above the B level.
1.50 (1.499) The most common resin lens on the market, the refractive index is relatively low, and myopia can reach up to 600 degrees. If the frame is larger, the edge of the lens will be thicker. The price ranges from 50-200, which is suitable for elementary and middle school students. The power often changes and the lens needs to be changed. The price is relatively cheap.
1.56 (1.556) At present, the relatively popular resin lens has a medium refractive index, commonly known as super thin film, but now it should be called a medium refractive lens, which can reach 800 degrees of myopia conventionally. The price ranges from 100-500, and it is recommended for customers within 800 degrees.
1.61 (1.607) This can be called a super thin sheet. The retail of domestic brands ranges from 300 to 600. Compared with the previous two aspheric lenses, the thickness is much thinner . Recommended within 1000 degrees.
1.67 (1.667) is now called ultra-thin lens, retail 600-1000 range, the power can be 1500 degrees, 500-600 myopic friends This lens should be a good choice. I use this refractive index lens myself. It has an aspherical design and is very comfortable for vision. The price is high (the lens is an imported lens, rarely made in China). It is recommended to be within 1200 Customer use.
1.74 (1.735) The thinnest lens currently available, with aspheric design, starting at 1,000 yuan, is all imported and affixed to domestic brands. It can be used by people who pursue beauty, beauty, and high quality, and the maximum temperature can reach 2000 degrees. It is recommended for people within 1500 degrees.