The choice of lens can be considered from three aspects: material, function and refractive index.
material
Common materials are: glass lenses, resin lenses and PC lenses
Suggestions: CHILDREN active, from safety considerations, the best choice of resin lenses or PC lenses, high myopia patients had better choose glass lenses, adults can be selected according to personal interests, economic conditions suitable lens materials.
Glass lenses
High hardness, the lens is not easy to produce scratches, but no toughness, easy to break when hit; High transparency, light transmittance of 92%; Stable chemical performance, can resist the influence of all kinds of bad weather, and do not color, do not fade; But fragile, heavy weight, not suitable for teenagers to wear.
The resin lenses
Much lighter than glass, reduce the pressure of the wearer caused by the mirror, more comfortable; Impact resistance, not easy to break, even if broken into an obtuse Angle, no danger to human eyes; Can be dyed into a variety of colors, fog function is better than glass; But the lens wear resistance is poor, easy to break, low refractive index, relatively thicker than the glass sheet 1.2-1.3 times.
The PC lenses
Strong toughness, not easy to break, super impact resistance, high refractive index and light specific gravity, greatly reduce the weight of the lens, 100% UV protection, 3-5 years no yellowing; But processing is more difficult, the surface is easy to scratch, thermal stability is not good, 100 degrees will become soft. PC material lenses are generally used for sunglasses, less appear in the optical mirror, basically applied to flat glasses.
function
Common functions include: aspheric lens, spherical lens, sunshade lens, anti-blue light lens, anti-fatigue lens, multi-focal lens, etc. According to their own life and use of the corresponding lens function type.
Aspheric surface lens
The aspheric lens unifies the focus. Aspherical lenses are lenses whose radii of each point on the surface are determined by the multiimage higher order equation. Its surface radian is different from that of ordinary spherical lens, so it is necessary to change the surface of the lens in order to pursue the thinness of the lens. The spherical design used in the past increases the aberration and deformation, resulting in obvious unclear images, distorted horizon, narrow vision and other undesirable phenomena. The current aspheric design corrects the image, solves the distortion of the horizon and other problems, and makes the lens lighter, thinner and flatter, making the wearer more natural and beautiful.
The spherical lenses
Spherical aberrations of spherical lenses. A spherical lens is one in which both sides of the lens are spherical, or one side is spherical and the other is flat. Generally thicker, and through the lens to see things around the distortion, deformation and other phenomena, called aberration. By observing the wearer through the spherical lens, the deformation phenomenon of the facial contour can also be obviously found. Spherical lenses usually fit under -400 degrees. If the degree is higher, the lens will be thicker and the pressure on the nose will be greater. This is also a disadvantage of spherical lenses compared with aspheric lenses.
Generally speaking, compared with the aspheric lens, the aspheric lens with the same material and degree is flatter, thinner, more realistic, more natural and comfortable, which solves the problem that the traditional spherical lens has distortion when viewing objects around. The traditional spherical lens limits the wearer's visual field, while the aspheric lens reduces the edge aberration to the bottom, and its wide field of view can meet more needs of customers.
Blue light blocking lens
Blue blocking lenses are glasses that prevent blue light from irritating your eyes. It protects the eyes from blue light damage by blocking and reflecting high-energy short-wave blue light through special material lenses. Anti-blue light glasses are suitable for people who often play with computers and mobile phones.
Sunshade lens
Also known as a solar lens. People in the sun usually depend on the size of the pupil to adjust the flux of light to avoid strong light damage to the eye. It is generally divided into three categories:
(1) Color-changing lenses:
The main effect is to protect the eyes and prevent strong light stimulation. Lenses are colorless indoors, but they change from colorless to colored when exposed to strong light outdoors. When choosing colors for color-changing lenses, it is generally recommended to choose three colors: tan, green, and gray. Because these three colors conform to visual physiology, improve visual contrast and sharpness, and will not change the original color of the scene due to the lens.
(2) Stained lenses:
To prevent the sun's strong stimulation caused by eye damage. The lenses are dyed with different colors through a specific process to meet the needs of different visual environments. Stained lenses are not suitable for indoor use because they can interfere with visual effects. The COLOR PLATE THAT CAN PROVIDE ACCORDING TO MANUFACTURER COMMONLY, INDIVIDUAL BE FOND OF AND USE ENVIRONMENT TO DECIDE COLOR CHOICE.
(3) Polarizing lens:
A lens that allows only light in a particular polarization direction of natural light to pass through. To reduce the visual discomfort caused by glare, it is most suitable for outdoor sports. For example: sea sports, skiing and fishing.
Fatigue resistant lens
The general anti-fatigue lens adds +50~+60 degree adjustment load to the lens according to the principle of similar progressive piece, optimizes the myopia luminosity, restores the microwave motion to normal, restores the balance of the adjustment system of the glasses, and achieves the function without fatigue, thus achieving the complete "decompression" of the eyes.
Multiple focal lens
Also called progressive multiple focal lens, it is to point to in the same lens only in the area and almost run out area between, with diopter, gradual change from far with gradually close to use readings will be much light and almost run out of organic together, so on a lens at the same time have a look at distance, middle distance and close the required different luminosity.
The refractive index
Resin lenses commonly have: 1.50, 1.56, 1.60, 1.67, 1.74 refractive index
Common glass lenses have: 1.8 and 1.9 refractive index
In general, the lens with a higher refractive index produces a thinner lens. Of course, refractive index is not the only factor that determines the thickness of the lens. The pupil distance and the size of the frame also affect the thickness of the lens. The larger the pupil distance, the smaller the frame, the thinner the lens. For example, if the lens of 1.56 is also selected, the lens with pupil distance of 68mm is much thinner than the lens with pupil distance of 58mm. This is because the farther the lens is from the focal point, the thicker it will be. Refer to the comparison table reasonable selection of suitable refractive index lens, generally the higher the refractive index of the lens price is also higher, avoid blind selection of high refractive index lens.
Post time: Sep-10-2022