Why filling nitrogen in optical instrument ?
Nitrogen is a nearly inert gas , filling nitrogen in optical instrument can replace some expensive inert gas , high purity nitrogen can weaken the metabolism and aging degree of biological or most materials , slow oxidation process of metal material and has the mildew proof effect.
In addition , nitrogen with high purity has the excellent characteristic of low expansion rate when being heated. It will not produce high pressure or negative pressure when the temperature difference changes greatly, so that the mirror body will not produce dew. Nitrogen has another characteristic, which is poor permeability, only 30% to 40% of the normal air permeability.
Why is it necessary to fill an optical instrument with nitrogen instead of ordinary air ? In the production of optical instruments, if the interior is filled with common gas , then the internal hydrosphere and fungi will survive in the mirror. Once the temperature is low and humidity is appropriate, the inner lens will be covered with mycelia or mould. However, when the nitrogen is full, the internal metal parts are not easy to rust and will not corrode the inner waterproof gasket due to the unique oxidation relief of nitrogen. In addition, the proportion of moisture in the air is not small in daily life. When the temperature is low, the water in the air will change from the gaseous state to the liquid state and attach to the lens. Especially when the temperature difference changes obviously, you can see some water vapor inside the lens, which means there is no nitrogen filling in the mirror at all, or the nitrogen filling has failed. This is often a good way to test the presence of nitrogen in optical instruments.
In optical instruments, nitrogen is usually filled with nitrogen bottles .First take air out of the interior and then fill with pure nitrogen. Since nitrogen is filled under pressure, some impurities are carried out of the telescope , rifle scope ,magnifier scope or sight by high-pressure airflow , so it is more cleaner inside .
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