The color filter selectively transmits light in a specific wavelength range, while absorbing the rest. They usually block longer and shorter wavelengths (bandpass) only by long wave pass, short wave pass or wavelength band. The passband can be narrower or wider; The transition or cutoff between the maximum and minimum transfers can be sharp or gradient. There are filters with more complex transmission characteristics, such as having two peaks rather than a single band; These are usually older designs traditionally used for photography; More regular filters are used in scientific and technical work.
Optical filters are usually used for photography (sometimes with special effects filters and absorption filters), and in many optical instruments and in color stage lighting. In astronomy, optical filters are used to limit light to the spectrum of interest, such as studying infrared radiation without visible light, which affects the film or sensor and overwhelms the desired infrared. Optical filters are also essential in fluorescence applications such as fluorescence microscopy and fluorescence spectroscopy.
Photo filter is a special case of optical filter, and many materials here are applicable. Photographic filters do not need precisely controlled optical properties and precisely defined filter transmission curves designed for scientific work, and sell a large number of photos at a lower price than many laboratory filters. Some photographic effect filters, such as star effect filters, are not related to scientific work.
Optical filter is a device that selectively transmits light of different wavelengths. It is usually realized by plane glass or optical plastic. These optical products are coated with interference coating after coating technology. The optical properties of filters are described by their frequency response, which specifies how the amplitude and phase of each frequency component of the input signal are modified by the filter.
Visible light that can be seen in human eyes is arranged from long to short wavelength, and in turn is red, orange, yellow, green, green, blue and purple. The wavelength range of red light is 0.62-0.76 μ m； The wavelength range of violet light is 0.38-0.46 μ m。 The shorter the wavelength of violet light is called ultraviolet, and the longer the wavelength of red light is called infrared. The naked eye can not see infrared. Because the digital camera uses CCD to sense all light (visible light, infrared and ultraviolet rays, etc.), this makes the image taken is very different from the image produced by visible light only seen by our naked eye. To solve this problem, the manufacturer of light guide block has added an infrared filter between the lens and CCD, which is used to block infrared rays from entering the CCD, so that the CCD can only sense visible light, so that the image taken by the digital camera is consistent with the image we see with the naked eye.