PROJECTION LENS

Provided is a projection lens including a first lens, a reflective optical device, a second lens, a third lens and a fourth lens from an image side to an object side in turn. The first lens is of a negative focal power, an image side of the first lens is of a convexity, an object side of the first lens is of a concavity; the reflective optical device enables light to be bended; the second lens is of a positive focal power, an object side of the second lens is of a convexity; the third lens is of a positive focal power, an image side of the third lens is of a convexity, an object side of the third lens is of a concavity; and the fourth lens is of a positive focal power. A diaphragm is arranged between first lens and second lens, meeting 0.25<ImgH/D<0.55.