Optical filters allow a portion of the spectrum to pass (transmit) while blocking the remainder.Based on different application filters come in many levels of performance and also known as Color Glass Filter ,dichroic filter, Neutural Density Filter, IPL Filter ,Band pass Filter, IR Cut Filter , reflective filter, optical thin film filter, Birefringent filter and interference optical filter. The simplest types of filter are made of absorptive materials such as some colour filter glasses yellow glass GG420, orange glass OG570 and red glass RG695 etc.. Certain wavelengths of light can be absorped by these kinds of colour glasses. Interference filters or dichroic filters are more complex and higher performance because of multiple layers dielectric materials deposited on a substrate causing constructive/destructive interference of the light in order to achieve the required performance.
