refractive index
It is the ratio of the transmitted light angle of the lens to the incident light and the sine of the incident light angle. Its value is generally between 1.49-1.74. At the same degree, the higher the refractive index, the thinner the lens, but the higher the refractive index of the material, the stronger the dispersion.

scratch resistance
Refers to the degree of damage to the transmittance of the lens surface under the action of external force. The scratch of the lens is an important factor affecting the service life and visual effect of the lens. The friction haze value (Hs) is commonly used in China, and its value is generally between 0.2 and 4.5, the lower the better. The BAYER method is commonly used in foreign countries, and its value is between 0.8 and 4, the higher the better. Usually referred to as hardened resin lenses, the scratch resistance is better than that of ordinary resin lenses.

UV cutoff
Also known as UV value, it is an important indicator for evaluating the effective blocking of UV radiation by lenses. Its value must be greater than 315nm, generally greater than 350nm and less than 400nm. UV400 lenses, often heard in optical shops, can effectively block ultraviolet radiation. In addition, a radiation protection film can also be added to the resin lens.

Transmittance
Refers to the ratio of the projected light amount to the incident light amount of the lens. The higher the transmittance, the clearer the lens.

Abbe number
It is an inverse proportional index used to express the dispersion ability of transparent materials, and can be used to refer to the ability of the lens to resolve the color and lustre of the interference of visible light. Its value is between 32 and 60, the higher the Abbe number of the lens, the less distortion.

impact resistance
Refers to the mechanical strength of the lens to withstand the impact force. The impact resistance of resin lenses is stronger than that of glass lenses, and even some resin lenses cannot be broken.

Film firmness
It is an index used to refer to the life of the coating layer of the coated lens. Many consumers will require that the lenses are coated. Various films have different functions, and some lenses even have several types of films added. Common ones are anti-reflection film, hard film (anti-wear film), anti-radiation film and so on. If the ordinary lens can be seen clearly, there is no need to add the film. If it is necessary, the resin lens can be added with an anti-reflection film or a hard film, and the glass lens generally only has an anti-reflection film.

1) Anti-reflection film, which uses the principle of light interference to reduce the excess reflected light on the surface of the lens, improve the light transmittance, reduce the glare, and make people see more clearly. beautiful.

2) The addition of a hard coating can effectively protect the lens surface from wear and tear, and can also resist the damage of hard objects, extending the life of the lens. It is generally added to the front surface of the lens to enhance the anti-wear ability of the resin lens, and at the same time, the permeability of light is also enhanced.

3) Anti-radiation film can block harmful ultraviolet rays in sunlight,

Therefore, it is recommended to wear glasses that can absorb 99-100% of UV rays.

4) Anti-fouling film: Because the gap between the molecules of the reflective film is large, the surface of the lens is easy to hide dirt and dirt, while the material of the anti-fouling film has small molecular particles and small gaps between the molecules, which makes the surface of the lens smoother and increases the waterproof and anti-fouling properties. Fog, dust and other anti-pollution functions.

8. Anti-radiation performance: refers to the ability of the lens to shield electromagnetic radiation from an insulator into a certain degree of electrical conductor by evaporating a certain metal conductive substance. Anti-radiation lenses have become the mainstream of coated lenses.

9. Specific gravity: Indicates the density of the material. The smaller the specific gravity of the material, the lighter the lens can be made. Today, light lenses are increasingly favored by customers.

10. Polarized light: Polarized lenses can protect people from reflected light, and can enhance the visual contrast outdoors, especially when driving, polarized lenses can reduce the glare of the glare. You can see that polarized lenses are used on most tinted sunglasses.

11. Other physical indicators: flame retardancy, yellow index, anti-sag, discoloration, etc.