The high-load use of instruments and equipment is often prone to accidental failures. In particular, if optical instruments are fogged due to improper maintenance and use, they cannot function properly and cause obstacles in their work. Preventing optical instruments from fogging increases our experimental efficiency.
At present, many enterprise equipment maintenance management generally stay in the passive repair operation mode, and the management of instruments and equipment should also be planned.
Similarly, equipment maintenance management also needs to transform unplanned work into planned work. If we regularly check and maintain to reduce the occurrence of faults, especially the “three defenses” of the instrument, avoid the repair work , and ensure that the instrument can be put into normal function at any time.
In the use and storage of surveying and mapping instruments, in addition to the mildew phenomenon, there are often fogging of optical parts, which affects the normal use of the instrument, so it can take preventive measures against the main factors of fogging of optical signals.
Causes and harms of fogging of optical instruments
Fog refers to the polishing surface of optical parts, which exhibits the appearance of “dew”. Some of these substances are composed of oily dots, called oil mist, and some are composed of water droplets or water and glass to form a chemical reaction. It is called water-based fog: on some optical parts, there are two types of fog, called water-oil mixed fog, which are generally present on the glass surface in the form of “dew” or dry deposits.
Oily fog is usually distributed at the edge of the optical optics and extends toward the center, while some are distributed along the wiping marks. The formation of oily fog is mainly caused by oil contaminating the surface of the glass, or due to the diffusion of grease, and volatilization on the surface of the glass Caused.
For example, the accessories used for wiping optical parts have high fat content, or the tools used are greased, and the direct use of fingers to touch and touch optical parts can cause oily fog, or the chemical stability of the grease used on optical instruments is not good. If the diffusion or the method of use is improperly applied, the oil may spread to the optical parts to cause oily mist, or the oil of the instrument may be volatile, and oily vapor may be generated to form an oily mist.
The water-based mist is formed by the humid air under temperature changes, mainly distributed over the entire area of the part. The main cause is the humid gas, but the sealing performance of the instrument, the chemical stability of the optical glass, and the cleanliness of the glass surface. Relatedly, under high relative humidity, mold is easy to grow, and some molds grow large, and then produce secretions around the mycelium. Some of these secretions are liquid, and an aqueous mist is formed on the periphery of the liquid secretion.
The fog formed by any reason, because the droplets are spherically distributed on the surface of the optical part with a small radius of curvature, causing the incident light to scatter, in addition to reducing the effective transmittance of the instrument, and affecting the observation quality. . Some optical parts are fogged for a long time, and many micropores are formed on the surface of the corroded glass, which seriously causes the glass parts to be scrapped.
The fogging of optical instruments is not only serious in the southeastern part of China, but also in the drier areas. Because of the temperature difference, it will also fog. It is more affected than the optical instrument, and it is more difficult to prevent.
How to prevent the instrument from fogging
The anti-fog material of the optical instrument is required to have a good anti-fog effect, and the optical performance of the glass is not affected. The following hydrophobic film material can be used to achieve a good anti-fog effect.
- use anti-fogging agent
The use of ethyl hydrogen-containing dichlorosilane to treat chemically permeable double-coated and uncoated optical glass parts can form a relatively strong film layer, has hydrophobic properties, has good waterproof fog performance, and is easy to form and coat at the same time. - The surface of the optical parts can improve the mechanical properties of the glass, protect the glass surface from scratches to a certain extent, improve the chemical stability of the optical glass surface, use it to clean the glass, and has strong decontamination ability, and it is easy to remove the fingerprint. The saliva circle improves work efficiency, which is a good anti-fogging agent.
- vacuum coating method
Platinum-coated perfluoroethylene propylene, which is an inert fluoroplastic with high chemical stability, heat resistance, cold resistance and corrosion resistance. It has strong bonding strength with glass and metal and has good anti-mildew resistance. Fog performance. It can not only form an electroless coating on a general glass surface, but also form a protective film on a fluorinated film layer, and can form a film on the surface of a phosphate glass. - using non-sulfide silicone rubber seal putty
The optical instrument has good sealing performance and plays an important role in mildewproof and anti-fog. The non-sulfurized silicone rubber is greasy and is a kind of non-sulfided ether silicone rubber. It is composed of filler, colorant and structure control agent. The low temperature performance is significantly better than the original sealing wax, and other indicators are not lower than the sealing wax.
Design anti-fog measures in use
- pay attention to anti-fog when designing the instrument
The structure of the instrument should strengthen the sealing performance to ensure that the instrument does not reduce the sealing performance under high temperature or low temperature to prevent the water mist caused by air leakage. Designers should pay full attention to selecting optical glass and materials with good chemical stability for anti-fog. Lay a good foundation. - pay attention to clean operation
The assembly and repair workshop must be cleaned and strictly in accordance with the operating procedures. Carefully wipe the optical parts. It is strictly forbidden to directly touch and take optical parts by hand. The tools for holding optical parts must be degreased and used to wipe the accessories used in optical parts. Cotton light, cloth, ethanol, ether, iodine and organic gaskets in contact with optical parts must be strictly degreased to control the amount of fat. The containers containing optical parts and the bottles containing ethanol and ether should be cleaned frequently and kept clean. These are all ways to reduce oily fog. - reduce the water vapor inside the instrument
Prevent water vapor from condensing on the glass surface, assemble as much as possible under dry conditions or dry the assembled instrument, such as dry nitrogen or air and place the desiccant. In the use and inventory of the instrument, try to control the relative humidity of the use environment and the warehouse is about 6%. For the correcting instrument, the revising instrument, etc., for the lens and precision optical components that can be taken down, take it down and put it into the drying cylinder in time. Protected internally and often keeps the instrument clean and reduces the core of the fog. - reasonable choice and use of grease
All kinds of dustproof greases and lubricating greases used in optical instruments must be materials with extremely low volatilization and good chemical stability. When applying grease on the metal parts of optical instruments, the parts must be cleaned first, so that the gasoline is evaporated. Apply grease and evenly and not too much. It is forbidden to apply grease and dust to the range of 10-15mm from the optics to prevent oil mist from spreading due to grease diffusion. - improve chemical stability
The electroless plating or vacuum coating method is used to deposit a hydrophobic film on the surface of the glass to improve the chemical stability of the glass, enhance the corrosion resistance of the glass, reduce fogging, and reduce the influence of water mist on the observation. The water material is coated with a transparent pseudo-hydrophilic film with certain physical properties, so that the water mist can be completely dispersed and uniformly dispersed in the film layer without affecting the observation. When the atmosphere is dry, the water in the film layer is naturally The ground volatilizes into the atmosphere. - mold removal, defogging
Once the optical instrument is foggy, it will cause adverse effects, and it will bring a lot of trouble to the repair work. Therefore, it is necessary to take precautions and pay attention to mold and anti-fog from the beginning of instrument design and manufacture. Strengthening maintenance during use is an important guarantee for anti-mold and anti-fog work. If the instrument has been moldy and fogged, it should be disposed of in time to avoid further damage.
After the instrument is mildewed, it should be treated in time. Otherwise, the surface and coating of the optical parts will be corroded, and even the glass will be corroded. It should be scrubbed with a common mixture or ethyl hydrogen dichlorosilane solution in time.
The solution is anti-fog and has a certain effect of removing fog and removing mold. The green filter of the multimeter is mostly phosphate glass, which is easy to fog, and it is difficult to wipe it clean.
It can be washed with dilute ammonia water, then washed with water, and then the surface of the filter is dried with the mixture. However, this kind of glass is very unstable.
If it is not used, wipe it in a dry dish or spray it in time, otherwise it will be mildewed. For silicate glass, try to avoid rubbing with alkaline substances, because alkali has corrosive effect on silicates.
If the optical parts are heavily moldy and foggy and have corroded the glass, only replace the glass or re-polish the optical parts. In short, the optical instruments should be based on prevention, and the mildew mist should be disposed of in time. In addition to the mildew, it is necessary to take anti-fog and mildew measures in time to protect the instrument and play a greater role.
