Assemble lens technology and spectacle lenses cannot be 'lifetime'
For this lens, the process of assembling the lens is the process of adjusting aberrations (spherical aberration, coma, astigmatism, curvature of field, distortion, and two kinds of chromatic aberration). Here we mainly introduce the 'star point' commonly used in factories. law'.
The star point method is to use transmitted light on a glass plate coated with aluminum film (the aluminum film is very thin, and some parts will transmit light) to produce diffraction spots, and then pass Observation with a microscope system that needs to adjust the lens. In theory, if the lens has no aberrations, the diffraction spots seen in the eyepiece field of view should be Airy disks plus several very thin rings, so the process of adjusting the lens is to change the lens while observing the shape of the diffraction spots Real-time process of parameters.
For the masters who have rich experience in adjusting lenses, they can see at a glance which aberrations exist in the lens and how to adjust the optical lens. For novices who are just getting started, this is quite difficult.
The following is a summary of the shape of the diffraction spot and the correspondence of various aberrations:
1. Spherical aberration: The brightness of the Airy disk accounts for the wrong proportion of the brightness of the entire diffraction spot (theoretically 84%) or the diffraction ring is too thick; the general solution is to turn the lens holder Or add spacers between the lens mounts to change the air gap (you need to use software to simulate the sensitivity of each air gap, and then decide where to change the lens);
2. Comatic aberration: as the name suggests, it is the shape of the diffraction spot like the tail of a comet; the general solution is to adjust the coaxiality. The above-mentioned 'the gap between the second group and the mirror body is about 0.1 to 0.2' is for this purpose. In addition, it should be noted that the coma is often the most obvious when the lens has just been assembled with the optical lens, so it is generally to adjust the coaxiality, correct the coma, and then observe other aberrations.
3. Astigmatism: Need to rotate the lens to observe, usually by changing the glass to improve The surface shape of the glass is out of tolerance);
4. Field curvature: Observe the spots of the center field of view and the edge field of view out of focus;
5. Distortion: The shape of the diffraction spots is irregular. If it is not a problem of the design itself, this kind of anomaly often needs to be dealt with from the surface of the lens.
After many people wear glasses, they often wear them until they break or become unusable. According to a recent large-scale survey, among consumers who use resin lenses, 29.2% of them only replace a pair of focusing lenses every 3 years or more, and 36.4% of them do not only change a pair of focusing lenses when their glasses are worn out. Replace the glasses. In fact, if the lens is 'overtime service
Teenagers whose degrees change very quickly are best to change their glasses every six months to a year. Adolescents are at the peak of eye use. Due to long-term use of eyes at close range, ciliary muscle adjustment spasm will occur, and myopia is particularly prone to deepen.
Adolescents who overuse their eyes need to refraction once every six months (mydriatic refraction). If the glasses are no longer suitable for changes in the refractive power of myopic eyes, they should be replaced in time. Of course, if it is pseudomyopia, after the pupil dilation, the eyes are rested and treated with drugs, and the vision can be restored without the need for glasses.
Here, it is important to point out that adolescents must dilate pupils and refraction aspheric lenses when changing glasses. Optometry glasses should not be sloppy, and glasses must be matched with prescriptions issued by regular hospitals.
In addition to subjective refraction, optometry should be mydriatic refraction. The adolescent’s ocular muscle adjustment function is too strong, and mydriasis refraction can understand their truth. The refractive status and refractive power. The refractive power of the matched lens should be consistent with the refractive power on the prescription. If the deviation exceeds the national standard, the development of myopia or hyperopia will be accelerated.
The reading glasses of the elderly should also be replaced regularly. Presbyopia is caused by the aging of the lens. As people age, the degree of lens aging will increase. Only the corresponding increase in the lens power required for correction can meet the needs of the daily life of the elderly. There is no uniform rule for the specific replacement time. When the elderly feel difficult to read the newspaper wearing glasses, and the eyes are sore and uncomfortable, they should be replaced.