Illumination system and projection device

A projection device, comprising an illumination system, a light valve, and a projection lens, the illumination system being configured to provide an illumination beam, the light valve being disposed on a transmitting path of the illumination beam to convert the illumination beam into an image beam, the projection lens being disposed on a transmitting path of the image beam to project the image beam, and the illumination system comprising:

• a light source, configured to provide a first beam;
• a first light-condensing lens, having a first-half portion and a second-half portion, wherein the first-half portion is located on a transmitting path of the first beam;
• a first optical element, disposed opposite to the first light-condensing lens, wherein the first optical element is located on a transmitting path of the first beam from the first-half portion and is configured to generate a second beam, and the second beam at least passes through the second-half portion;
• a first beam splitter, disposed on a transmitting path of the second beam and configured to reflect a first part beam of the second beam and allow a second part beam of the second beam to pass therethrough;
• and
• a mirror, disposed on a transmitting path of the second beam at least partially from the first beam splitter, wherein the first part beam of the second beam and the second part beam of the second beam form the illumination beam.