1.base material quality.
The substrate quality determines the durability of the lens and the reliability of the coating. Good substrate clear and bright, long use time and not easy to yellow; And some lenses do not take long to turn yellow, and even the coating falls off. Good lens without a scratch, scratch, hair, pitting, the lens oblique to the light observation, high finish. There are no spots, stones, stripes, bubbles and cracks inside the lens, and the light is bright.
2.Grade of lens.
Mass-produced lenses are divided into different grades due to differences in intrinsic quality, and the prices of superior and inferior products vary greatly.
3.Refractive index.
The higher the refractive index, the thinner the lens, and the higher the price.
4.coating and anti-ultraviolet treatment.
Resin sheet can be hardened (scratch resistance), anti-reflection, anti-static, dustproof, waterproof coating processing as many as a dozen layers, different coating processing has a different role, if reduce the coating processing process, the quality of the lens will be greatly discounted. Similarly, if the lenses do not prevent uv as uv lenses wear, so it is very harmful to the eyes.
5. Lens brand.
Brand differences lead to differences in quality and price. The quality of lens is directly reflected in the brand of lens. Famous brand lenses are of good quality and stable.
6. Test the transparency and optical uniformity of lens.
Hold the lens 30 cm away from the eye and observe the distant scenery through the lens. If the scenery is clear and without deformation, and there is no scene jump when moving the lens slowly, the transparency and optical uniformity of the lens are good.
7. Determine the axial direction of astigmatism lens.
On a blank sheet of paper to draw a perpendicular cross fork, put the lens in the spider rotate graphic above 30 centimeters, visible lens move the cross the cross fork, lens inside and when connected to stroke cross graphics, graphics was positively cross, where column lens axis and straight line, then the lenses were repeatedly moving along a straight line; Observe which line diverges more from the line outside the lens when moving, and this line is the direction of the scatterlight axis.
8. Test the optical center displacement.
Draw a large cross on a piece of white paper in a thin, clear, straight line. Hold the lens between the eye and the cross, observe the shape of the cross from the mirror with one eye, if the inside and outside of the mirror are not in line, you can move the lens, so that the inside of the lens and the outside of the mirror cross line. Use a brush or fountain pen to place a small point on the cross center of the lens, which is the optical center. After pointing the optical centers of both lenses, observe and compare whether the bilateral optical centers are symmetrical, and measure the distance between the two centers with a small ruler to see whether the distance between the two centers is consistent with the prescribed distance to the pupil. If the cross in the lens is bent, it shows that there is internal stress or uneven optical density of the lens.
9.wear feeling.
Wear without any feeling, dizziness, eye swelling, observation objects are not blurred, not deformed. When buying, hold glasses in hand and look at distant objects with one eye through the lens. Shake the lens up and down. The illusion of movement of distant objects should not occur.
10. Protection.
High quality lenses can effectively block uv rays and provide effective uv protection for the wearer.
Post time: Nov-10-2021