Projection lens

A projection lens configured to project an image beam provided by a light valve onto a screen, wherein the projection lens comprises a first lens, a second lens, a third lens, and a fourth lens in order from a screen side to a display side along an optical axis, wherein each of the first lens to the fourth lens has a screen side surface facing the screen side and allowing the image beam to pass, and a display side surface facing the display side and allowing the image beam to pass, wherein:

• the first lens has a negative refractive power, the second lens has a positive refractive power, the third lens has a negative refractive power, and the fourth lens has a positive refractive power;
• and
• the projection lens satisfies:
• 2<TTL/f<5,
• wherein TTL is a distance from the screen side surface of the first lens to the display side surface of the fourth lens on the optical axis, and f is an effective focal length of the projection lens.