Transmittance refers to the clarity of the lens. The ratio of the total amount of light entering the eye after passing through the lens to the total amount of light reaching the lens. The higher the ratio, the better the light transmittance and the higher the clarity, generally at 91 %the above.
Here are the light transmittances of several kinds of lenses:
White light transmittance: 89% x 85 %Kesai sheet 85%
resin sheet light transmittance: 89-92%PC: 85-91%
Optical lens 92% Plastic lens 79%
Optical white film: 91%
Coated film: 98%
PC film: 99.5%
Without the addition and subtraction of the reflection film, the light transmittance is related to the refractive index of the material. Generally, the higher the refractive index, the lower the transmittance of the optical lens. The light transmittance of the material with a refractive index of 1.5 is about 92%, and the light transmittance of the material with a refractive index of 1.6 is about 89%.
So Yichao glasses suggest: When choosing high refractive index lenses, use lenses with plus and minus reflection coatings as much as possible. A good anti-reflection film can make the light transmittance of the lens reach about 99%, and the wearer can not only see more clearly, but also greatly improve the visual contrast and reduce visual fatigue.
A considerable number of practitioners, due to the inability to use the instrument correctly or the inability to place the lens correctly, as a result, the measured value cannot truly reflect the actual value, which makes the glasses not only unable to correct vision , It makes the patient more painful.
The emergence of focal meter (diopter) enables the vertex power test of the lens, optical lens, optical center positioning, and astigmatism axis calibration to be completed on the instrument. It should be said that the various data obtained after the regular inspection of the instrument by the metrology department and the standardized operation of the practitioners are accurate and reliable. However, according to our actual understanding, a considerable number of practitioners cannot use the instrument correctly or place the lens correctly. As a result, the measured value cannot truly reflect the actual value. As a result, the equipped glasses not only cannot correct the vision, but also make the patient more painful. Talk about a few more common issues. Hope it can attract attention.
1. Before measuring, the focal meter should be adjusted as necessary to ensure that the 'zero' position is correct, and the 'heart-to-heart' is printed so that the so-called 'zero' position is correct is the measurement The user should first rotate and adjust the eyepiece circle according to their own diopter until the black scale division (consisting of a group of concentric circles) in the focusing lens eyepiece is the clearest, and then turn the focusing handwheel until the green target division (green cross line) Or the circle surrounded by dots) is the clearest. At this time, observe the dial in the reading window to see if '0'D is aligned with the indicator line. If the 'zero' point is incorrect, first write down the error value and make corrections during measurement, that is: actual measured value u003d reading value one (zero position) error value. Note that this formula calculates algebraic sum values.
The second is to ask professionals in the measurement department to adjust. It should be noted here that in order to avoid measurement errors caused by eye adjustment, when adjusting the eyepiece circle, for myopic eyes or normal eyes under 45 years old, the diopter circle should be adjusted to positive dioptric first, and then gradually turned to negative dioptric Until the reticle is the clearest aspheric lens, it is the opposite of the above for hyperopia or normal eyes over 45 years old. When adjusting the focus handwheel, it should be rotated unidirectionally in the direction of increasing the positive value (or decreasing the negative value) until the target reticle image is clearest.
In fact, some practitioners often take measurements directly without first adjusting the diopter circle. What's more, some operators actually The zero point of the focus handwheel is aligned with the index line, and then the eyepieces are adjusted to leave the target reticle with the clearest image, and then the lens is measured. This is an extremely wrong approach. The so-called 'heart-to-heart. Otherwise, it will affect the positioning of the optical center of the lens, and you should find a professional to adjust it in time.