The invention relates to an optical filter. The optical filter comprises a transmitting substrate and a filtering film, wherein the filtering film is fixedly arranged on the transmitting substrate, gaps are formed in four corners of the filtering film, the profile of the gap in one of the corners of the filtering film is matched with a thumb shape, profile lines of the gaps of the other three corners are straight lines, the gap matched with the thumb shape is formed in a right lower corner of the optical filter, and an index finger profile is further arranged at a position, corresponding to athumb, of the transmitting substrate. After the adoption of the structure, the profile of the gap of one of the corners of the filtering film is matched with the thumb shape, the index finger profileis further arranged at the position, corresponding to the thumb, of the transmitting substrate, a worker is convenient to rapidly identify a front surface and a rear surface of the optical filter within a short time, and the surfaces are convenient to identify.