Illumination system and projection device

A projection device, comprising:

• an illumination system, at least one light valve, and a projection lens,
• wherein the illumination system is configured to provide an illumination beam and comprises a light source device, a light homogenizing element, and a polarization element,
• wherein the light source device is configured to provide a first beam, a second beam, a third beam, and a first compensation beam,
• the light homogenizing element is disposed on transmission paths of the first beam, the second beam, the third beam, and the first compensation beam and configured to convert the first beam, the second beam, the third beam, and the first compensation beam into the illumination beam, and
• the polarization element is disposed on the transmission paths of the first beam and the first compensation beam and located between the light source device and the light homogenizing element,
• wherein the at least one light valve is disposed on a transmission path of the illumination beam and configured to convert the illumination beam into an image beam, and
• the projection lens is disposed on a transmission path of the image beam and configured to project the image beam out of the projection device,
• wherein the first beam and the first compensation beam pass through the polarization element to change polarization states of the first beam and the first compensation beam to be the same as polarization states of the second beam and the third beam.