Filter is a kind of optical element with targeted selection of spectral wavelength transmission, reflection, cut-off and attenuation. According to its function, it can be divided into band-pass filter, long wave-pass filter, short wave-pass filter, dichroic filter, neutral density filter (ND filter), notch filter, cold mirror, thermal mirror, color filter, etc.
These filters are widely used in spectral analysis, biomedicine, machine vision, fluorescence microscopy, industrial automation and other industries and product fields. The band-pass filter selectively allows and prevents the transmission of a certain spectral wavelength within its spectral range; Neutral density filter reduces the luminous flux by reducing the transmittance in the specified spectral wavelength range, which is conducive to the protection of sensors / electronic components. It is widely used in the field of laser optics / optoelectronics; Cold / hot mirrors can reflect and transmit light with long wavelength in the spectral range. They are widely used in lighting systems, which is conducive to eliminating the heat generated in the lighting system.