Optical engine unit and projection system

A projection system, comprising:

• a light source;
• and
• an optical engine unit, wherein the optical engine unit comprises:
• a light splitting assembly configured to split an illumination beam incident on the light splitting assembly into a first light beam and a second light beam;
• a first spatial light modulator configured to modulate the first light beam to form a first modulated light beam;
• a second spatial light modulator configured to modulate the second light beam to form a second modulated light beam;
• and
• a light combining apparatus comprising a light combining surface, wherein the light combining surface is a coated surface and configured to combine the first modulated light beam and the second modulated light beam into an emergent light beam and emit the emergent light beam, and an incident angle of the first modulated light beam on the light combining surface and that of the second modulated light beam being smaller than a total reflection angle of the light combining surface, and wherein the light source is configured to emit the illumination beam.