A filter includes two translucent bodies. Each of the translucent bodies has a first plane, a second plane that forms a wedge angle with the first plane, and a third plane that intersects with both the first plane and the second plane, first planes of the two translucent bodies are parallel to each other, and second planes of the two translucent bodies are parallel to each other. The filter also comprises a beam splitting film, where surfaces of both sides are respectively combined with the first planes of the two translucent bodies. Two reflective films are combined, respectively, with the second planes of the two translucent bodies.