A multi-piece combined filter is the core component of cameras, video cameras, and CCTV optical systems. It is generally composed of one or more pieces of optical grade crystal, wave plate and blue glass. The birefringence characteristics of artificial crystal, infrared cut-off film, anti-reflection film, etc. are used to effectively filter out the moiré fringes caused by high-frequency light waves. The blue glass performs chromatic aberration correction and better restores the true color of the image.