Projector and optical engine thereof

A projector with an optical engine, comprising:

• a light source system, providing an incident light beam;
• a reflective light valve, located in the light path of the incident light beam for receiving the incident light beam from the light source system, and modulating the incident light beam for reflecting and outputting an image light beam or a dumped light beam;
• a first case, with the light paths of the incident light beam, the image light beam and the dumped light beam inside, providing a first opening located in the light path of the dumped light beam;
• a projection lens, connected to the first case and located in the light path of the image light beam for receiving the image light beam and projecting the image light beam to form an image;
• and
• a second case, connected to and intercommunicating with the first case via the first opening, wherein the dumped light beam enters the second case through the first opening and is reflected twice or more inside the second case, an inner wall of the second case applies to absorb the energy of the dumped light beam.