The invention discloses a projection optical engine. The projection optical engine comprises a first turning reflector, a
light guide stick, a first
relay lens and a second turning reflector which are horizontally arranged in sequence, wherein a
light source is arranged below the first turning reflector; the projection optical engine further comprises a second
relay lens, a total-reflection
prism and a digital micromirror display
chip which are arranged above the second turning reflector in sequence; the incidence surface of the total-reflection
prism is inclined towards the second turning reflector; the second
relay lens is inclined, and the inclination angle of the second
relay lens is matched with the incidence surface of the total reflection
prism; the bottom end of the second turning reflector is close to the first
relay lens, and the top end of the second turning reflector is inclined towards the incidence surface of the total-reflection prism; the working surface of the digital micromirror display
chip is parallel to the outer side surface of the total-reflection prism and faces the total reflection surface of the total-reflection prism; a
projection lens is arranged on the outer side of the emergency surface of the total-reflection prism. The projection optical engine provided by the invention is reasonable in function
layout and compact in structure, and can realize high-efficiency light utilization and high-brightness light output.