The characteristics of lenses are mainly analyzed from optical, physical and chemical properties.
1. Optical properties: Optical properties are the basic properties of materials, which are consistent with various optical phenomena seen in daily life of lenses, mainly because the light is on the surface of the lens. Refraction and reflection, absorption of the material itself and other phenomena.
1. Refractive index: the value of light that deviates from its initial path after entering the transparent medium (lens material) from the air, usually between 1.4 and 1.9. For lens design, the significance of refractive index is that the higher the refractive index, the thinner the lens can be made. Therefore, the high refractive index lens material is thinner and more beautiful than the low refractive index material.
According to different refractive indexes, the classification of lens materials is as follows:
A. Ordinary refractive index 1.48≦n﹤1.54
B. The refractive index of the center-folding optical lens is 1.54≦n﹤1.64
C. High refractive index 1.64≦n﹤1.74
D. Ultra-high refractive index n≧1.74
2. Dispersion power: Dispersion power is an important characteristic of eye optics. Abbe number is used to reflect the dispersion power of lens materials. The Abbe number is inversely proportional to the dispersion force of the material, and the Abbe number of the lens material is usually between 30 and 60. The larger the Abbe number, the smaller the dispersion; the smaller the Abbe number, the greater the dispersion, and the greater the impact on the image quality. For all high-refractive materials (including glass and resin materials), lower Abbe numbers are more likely to produce chromatic aberration.
Although all lenses have chromatic dispersion, in the optical center area of u200bu200bthe lens, this interference factor can be ignored. Only the peripheral part of the high-dispersion lens, the chromatic dispersion phenomenon can be easily noticed by the optical lens, which is manifested as the off-axis object with colored stripes on the edge.
3. Reflectivity: When light is refracted on the surface of the lens, reflection will occur. The reflection of light will affect the clarity of the lens, and interfering reflected light will be produced on the surface of the lens. Generally, the higher the refractive index of the lens material, the more light is lost due to reflection. This phenomenon will cause an aperture phenomenon inside the lens, resulting in obvious thickness of the lens, the wearer's eyes will be covered by the reflection of light on the lens surface, the wearer sees a virtual image, the lens produces glare and reduces the contrast, etc. Of course, the interfering reflected light can be counteracted by plating multiple anti-reflection coatings on the surface of the lens.
4. Light transmittance: The light transmittance of the lens refers to the total amount of light that passes through the lens without being reflected or absorbed. The wearer's visual focusing lens is affected by the combination of three aspects: the intensity of the incident light and the incident spectral range, the absorption of the lens and the choice of the spectrum, and the sensitivity of the eye to different visible wavelengths.
5. Light absorption: The light absorption of the lens usually refers to the light absorption inside the material, which can be expressed by the percentage of light absorbed by the front and back surfaces of the lens. The absorption characteristics of the lens material itself will reduce the light transmittance of the lens. This part of the light loss is negligible for colorless lenses, but if it is a tinted or color-changing lens, the lens itself will absorb a large amount of light. This is also the design purpose of this type of functional lens, which is to reduce the amount of light incident.
Due to the influence of the transmittance of the lens itself, the clarity of vision quality is reduced, and the appearance of the wearer is affected. For example, the appearance of the lens is obviously vortex, and the eyes of the wearer cannot be seen by the opposite light.
The coated lens is a new technology that uses optical film and vacuum, and is coated with a certain thickness of single-layer or multi-layer optical film to improve the ability of the lens to reflect light. Play the role of enhancing or reducing the transmission of light to increase the transmittance of the lens.
The coating layers mainly include hard film, multilayer anti-reflection film, anti-fouling film, etc. The main function of each layer is:
Hard coat: increase the hardness of the lens surface and make it more wear-resistant.
Multilayer anti-reflection film: increase the visible light transmittance of the lens and the performance of anti-ultraviolet and anti-radiation.
Anti-fouling film: Due to the technical requirements of anti-reflection film, the film has a large inter-molecular space, and the surface of the lens is easy to contain dirt and dirt, while the material molecule particles of the anti-fouling film Small and small gaps between molecules make the surface of the lens more smooth and clean, and add water-proof, anti-fog, dust-proof and other anti-pollution functions.