A semi-transparent semi-reflective mirror (splitter) is an optical window coated with a translucent mirror-like film that can split a beam of light into two or more beams. The splitter reflects part of the incident light energy, absorbs a relatively small amount, and transmits the rest of the energy. The optical splitter has obvious neutral color characteristics. The spectroscope is made of multilayer dielectric film vacuum evaporation, no metal film will absorb the problem, the total ratio of penetration and reflection is close to 100. Made by vacuum evaporation, the penetration ratio can be changed after the light passes through the filter, for example: half can penetrate, half reflects, and has low absorption characteristics. Spectroscope is an optical device that can divide a beam of light into two beams, and is an important part in the middle of optical interferometer. It is usually made of a vertical optical glass coating. There are two main kinds of spectroscope products, one is polarizing spectroscope, and the other is non-polarizing spectroscope.