Optical filter is an optical device used to select the required radiation band. A common feature of filters is that no filter can make the imaging of celestial bodies brighter, because all filters will absorb certain wavelengths, making objects darker. The filter is made of plastic or glass with special dyes. The red filter can only let the red light pass through, and so on. The transmittance of glass sheet is similar to that of air, and all colored light can pass through, so it is transparent. However, after dyeing with dye, the molecular structure changes, the refractive index also changes, and the passage of some colored light changes.
Filters are widely used in photography. Color filter is a kind of optical filter that represents color. It can accurately select the light wave in a small range to pass through, and reflect other unwanted bands. Color optical filters are usually installed in front of the light source, so that the human eye can receive saturated light of a certain color. All optical elements are precision instruments, especially optical filters, whose surfaces are easily scratched. Improper cleaning and storage may damage the surface of the filter surface, reduce its application performance and shorten its service life. Therefore, the correct maintenance method is very important.
Let's discuss the small details that should be paid attention to in the normal use of optical glass filters:
1. During normal use, it shall be taken and placed as carefully as possible, and pay attention to the external environment to prevent scratching the filter.
2. Wear a finger sleeve when contacting the filter to avoid the corrosion of the substrate surface by salt and acidic substances on your hands.
3. When taking the filter, hold the edge of the filter by hand, and do not touch the light transmission surface of the filter even with a finger sleeve.
4. The filter should be placed on a soft and clean object, not on glass, metal, table or unclean paper.
5. Store it in clean capacitor paper or special lens cleaning paper. The storage temperature should be about 23 ℃ and the humidity should not be higher than 40%. It's better to put it in a dry storage cabinet.
6. When there are stains on the surface, clean it immediately. Because dust can easily scratch the surface.
7. If the acid left by fingers stays too long, it is easy to react with the surface coating material and become permanent stains. Therefore, the surface stains of the filter should be cleaned in time.
8. If there are stains or finger marks on the surface, wipe it with absolute ethanol or similar functional solvent. The specific method is as follows: put a dust-free finger cover on your fingers, wet the towel with absolute ethanol, drag the edge of the towel soaked with ethanol, and move in a single direction on the surface of the filter. During the wiping process, use light force as much as possible. Too much pressure may damage the filter surface. The purpose of using solvent is to dissolve the viscous attachment in the residue on the surface of the filter. However, it is worth reminding that any cleaning may reduce the surface grade at the micro level.
9. Do not stack the filters together to avoid wear.