These knowledge points of optical filters are explained

        Filters are used to attenuate (absorb) certain wavelength bands of light waves or to select a small range of wavelength bands to pass through, while reflecting (or absorbing) other undesired wavelength bands. By changing the structure of the filter and the optical parameters of the film layer, various spectral characteristics can be obtained, so that the filter can control, adjust and change the transmission, reflection, polarization or phase state of the light wave. A commonality of filters is that no filter can make the image of a celestial object brighter, because all filters absorb certain wavelengths, making the object darker. The filter is made of plastic or glass and added with special dyes. The red filter can only pass red light, and so on.

        Optical filters are made by adding special dyes to plastic or glass substrates or evaporating optical films on their surfaces to attenuate (absorb) certain wavelengths of light waves or to select a small range of wavelengths to pass through, while reflecting. (or absorb) other unwanted bands. By changing the structure of the filter and the optical parameters of the film layer, various spectral characteristics can be obtained, so that the filter can control, adjust and change the transmission, reflection, polarization or phase state of the light wave.

        Filters do a great job. Widely used in the photography world. A color filter is an optical filter that expresses color. It can precisely select a small range of light waves to pass, and reflect other undesired wavelengths. Colored optical filters are usually installed in front of the light source so that the human eye can receive light of a certain color in saturation.

        A bandpass filter is a filter with a cutoff band on both sides of the transmission band of the spectral characteristic curve. Bandpass filters transmit only certain wavelength bands and block others. The width of such a filter is expressed in the range of wavelengths it allows to pass, which can range from a few nanometers to hundreds of nanometers. Bandpass filters are roughly classified according to their spectral characteristics