Optical lens cleaning requirements for polishing powder and quality judgment of optical lens
The cleaning of optical lenses is divided into pre-coating and post-coating cleaning. The processor should choose a different method of cleaning the optical lens according to the difference of the contaminants before and after coating, and choose the special coating Optical lens cleaner.
1, optical lens cleaning before coating
The primary pollutant for cleaning before coating is the core oil (also called grinding Edge oil, core-seeking is also called core-setting and core-taking, which refers to the process selected in order to obtain a regular radius and core accuracy), fingerprints, dust, etc. Because the coating process has extremely strict requirements on the cleanliness of the lens, the selection of cleaning agents is very important. While thinking about the cleaning ability of a certain cleaning agent, we must also think about its corrosiveness and other questions.
2, cleaning after optical lens coating
usually includes cleaning before inking, cleaning before joining lens design and before assembly Cleaning, of which cleaning before joining (joining refers to the bonding of two lenses with photosensitive adhesive into a regular shape to meet the needs that cannot be processed at one time, or a process that produces a more special curvature and light transmittance) requires the most severe. The pollutants to be cleaned before joining are mainly a mixture of dust, fingerprints, etc. The cleaning is not difficult, but there are very high requirements for the cleanliness of the lens surface, and the cleaning method is the same as the previous two cleaning techniques.
(1) The particle size of the optical lens powder is fine and uniform, within the allowable range;
(2) It has high purity and does not contain other mechanical impurities;
(3) The micro-powder particles need to have a certain crystal lattice shape, and form sharp edges and corners when broken to improve polishing efficiency ；
(4) It has very good dispersibility to ensure high efficiency and uniformity in the processing process. Dispersants can be appropriately added to increase the suspension rate;
(5) It has proper density and hardness, and has good wettability and suspension with water. The polishing powder needs to be mixed with water. The larger the size of the polishing powder, the greater the grinding force. The more suitable for harder materials, it should be noted that the laser focusing lens, the particle size of all polishing powder has a distribution problem, the average particle size or the median diameter D50 only determines the polishing speed, while the largest particle size The diameter Dmax determines the level of polishing accuracy. Therefore, in order to obtain high-precision requirements, the maximum particle size of the polishing powder must be controlled.
Optical lens can change the direction of light propagation, and can change the relative spectral distribution of ultraviolet, visible or infrared light. Optical lenses can be used to manufacture lenses, prisms, mirrors and windows in optical instruments. Components made of optical glass are key elements in optical instruments.
The difference between optical lens and other glasses is that as a component of the optical laser protection lens system, it must meet the requirements of optical imaging. Therefore, the judgment of the quality of optical glass also includes some special and stricter indicators. The quality judgment of optical glass has the following requirements:
1. The specific optical constants and the consistency of the optical constants of the same batch of glass
Each type of optical lens has a prescribed standard refractive index value for different wavelengths of light, which serves as the basis for optical designers to design optical systems. Therefore, the optical constants of the optical glass produced by the factory must be within the certain allowable deviation range of these values, otherwise the actual imaging quality will not match the expected result during the design and the quality of the laser collimator of the optical instrument will be affected.
At the same time, since the same batch of instruments are often made of the same batch of optical glass, in order to facilitate the unified calibration of the instruments, the allowable deviation of the refractive index of the same batch of glass should be compared with their deviation from the standard value. More stringent.
Second, high degree of transparency
The image brightness of the optical system is proportional to the glass transparency. The transparency of an optical lens to light of a certain wavelength is expressed by the light absorption coefficient Kλ. After the light passes through a series of prisms and lenses, part of its energy is lost by the interface reflection of the optical parts and the other part is absorbed by the medium (glass) itself. The former increases with the increase of the refractive index of the glass. For high refractive index glass, this value is very large. For example, the light reflection loss of one surface of the optical lens is about 6%.
Therefore, for an optical system containing multiple thin lenses, the main way to increase the transmittance is to reduce the reflection loss on the lens surface, such as coating a surface antireflection coating. For large-size optical parts such as the objective lens of an astronomical telescope, the transmittance of the optical system is mainly determined by the light absorption coefficient of the glass itself due to its large thickness. By improving the purity of the glass raw materials and preventing any coloring impurities from mixing in the entire process from batching to smelting, the light absorption coefficient of optical glass can generally be made less than 0.01 (that is, the light transmittance of glass with a thickness of 1 cm is greater than 99% ).
Operation steps for cleaning optical lenses:
(1) Wash hands, blow dry or wait to dry.
(2) Put on finger cots.
(3) Gently take out the lens for inspection.
(4) First use an air ball or nitrogen to blow off the dust on the surface of the lens. (If there are obvious contaminants or defects, observe with a microscope).
(5) Wrap the applicator (wooden stick, iron brazing) with absorbent cotton, do not expose the sharp part, wrap it into a cotton ball, the size of the cotton ball depends on Depending on the shape of the lens.