Maintain the life of the lens and the structural design of the optical lens

by:Crylight     2021-06-06

The advantage of resin lenses is that they are light and not easy to break. The disadvantage is that they are not wear-resistant. The city we live in is full of dust and grease when FB. If you don't pay attention to maintenance, it will only take half a year. The correct method is to rinse off the dust on the front and back surfaces of the lens with tap water, apply detergent evenly on the surface of the lens, and then rinse off with water. The remaining water on the lens is dried with facial tissue. Generally speaking, lens 2 Clean once a day.

   Is it possible to use the lens without scratches, no matter what. The resin lens is processed by high temperature or ultraviolet curing of liquefied monomers. As the life cycle becomes longer, the environment and temperature change, the film on the surface of the lens and the material of the lens itself will undergo physical changes. The film will change when viewed under a microscope. It becomes uneven, and the local luminosity of the material itself is different from when it was prepared, causing light scattering, reduced comfort, and symptoms of dryness and swelling of the optical lens after long use. At this time, you should replace it. The lens is ready, and the time is about one and a half to two years.

   The common lenses are divided into substrates (lenses without film, used for dyeing purposes, very intolerant Polished), hardened film (silicide film, transparent and colorless, difficult to distinguish), green film (fluoride, increased light transmission), purple film (metal ion film, both light transmission and shielding of medium and high frequency radiation, the film itself With conductivity and shielding function). As long as it is a lens with a color film, the light transmittance can reach more than 97%.

  The hard film is mainly used by customers who have a bad working environment and poor self-care. The lens is not easy to be scratched and has a long life. However, the light transmittance is only 88 %, the lens is easier to reflect light in an environment where the light difference is relatively large (embodied in that the user can see the object behind from the inside of the lens, and the surface will reflect light when taking pictures).

   As we all know, optical lenses. For high-end lenses, optical design is very important, but how to transform a good optical design into a product is the most critical. But how are lenses (especially high-end lenses) manufactured, assembled and tested?

  Optical cold processing: Many friends who have not been in the optical cold processing workshop are very curious about the processing technology of optical lenses. In fact, optical cold processing is just like a stone The optical glass material of the shape is cut, rough-grinded, fine-grinded, polished, edging, coated, glued, etc. A complete set of processes, and finally the optical lens with the precision required by the drawing is obtained.

The marking of    optical lens requires strict tolerance analysis. The general processing accuracy given here is for reference only. In addition, it should be noted that the tighter the tolerance label, the greater the processing difficulty, and the higher the scrap rate of the workshop. For the lens that needs to be considered cost, this is the result of the focus lens combined with the tolerance analysis and carefully weighed of.

  Structural design

   1. Refer to the assembly drawing, change the lens mainly into the front Group, middle group, front pressure cap, middle group two, rear group, spacer, lens body, objective lens shell, pressure ring, spring, rear diaphragm and other parts.

  2. There are 5 lenses in this design. The first lens is fixed in the front group, and the second and third lenses are cemented together and fixed in the middle group. Here, the fourth lens is fixed in the second group, and the fifth lens is fixed in the rear group.

   3. The front group, the middle group, the middle group two, the back group, the spacer is placed inside the lens body, and then pressed by the pressure ring, and the lens body The outer side of the lens is screwed with the objective lens case and the front pressure cap. A spring (to protect the sample) is installed between the lens body and the objective lens shell, and the rear aperture is rotated in the objective lens shell.

  4. Someone must ask: Why fix the lens in the front group, middle group, middle group and back group instead of directly in the lens body ? That is an aspheric lens because the former method can be used to obtain higher coaxial accuracy. It uses an optical central instrument to determine the mechanical axis of the front group (the machining requirements for the front group are very high, requiring 'one size fits all'), and then Move the lens so that the optical axis of the lens is coaxial with the mechanical axis of the front group, and then dispense, expose and fix.

   5. The front group, middle group, rear group and the lens body have a smaller fit gap, the better, the front group, middle group, rear group outer diameter tolerance and mirror The inner diameter tolerance can be marked at about 5um.

   For this lens, the process of assembling the lens is the process of adjusting aberrations (spherical aberration, coma, astigmatism, curvature of field, distortion, two chromatic aberrations). This article mainly introduces the 'star point method' commonly used in factories.

   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.

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