To provide an optical system for projectors 15 for efficiently transmitting light emitted from a light source 20 to an image forming part.

The optical system for the projectors 15 is composed of the light source 20, a rod integrator 25, a relay lens 45, and a convex meniscus lens 40. The rod integrator 25 makes light emitted from the light source 20 incident, emits a light flux uniformed from an emission outlet 28, and provides an incident side face with a reflection face 26 for reflecting the light returned from the emission outlet 28. The relay lens 45 transmits at least a part of the light emitted from the emission outlet 28 to the image forming part. The convex meniscus lens 40 is installed between the rod integrator 25 and the relay lens 45, and provides at least a part of a periphery with a reflection part 35 for reflecting the light emitted from the emission outlet 28 toward the emission outlet 28 at a larger angle than the angle of the light taken in the relay lens 45.