Illumination system and projection device

A projection device, configured to generate an image light beam, comprising:

• an illumination system, configured to provide an illumination light beam, comprising:
• an excitation light source, configured to emit an excitation light beam;
• a light guide module, disposed on a transmission path of the excitation light beam;
• a collimation lens group, disposed on the transmission path of the excitation light beam;
• and
• a wavelength conversion element, disposed on the transmission path of the excitation light beam,
• wherein after being emitted from the excitation light source, the excitation light beam is reflected by the light guide module, passes through the collimation lens group, and is then transmitted to the wavelength conversion element in sequence, a part of the excitation light beam is reflected by the wavelength conversion element, passes through the collimation lens group, and then passes through the light guide module in sequence, another part of the excitation light beam is converted into a conversion light beam by the wavelength conversion element, and the conversion light beam passes through the collimation lens group and then passes through the light guide module,
• wherein the part of the excitation light beam and the conversion light beam emitted from the light guide module form the illumination light beam;
• a light valve, disposed on a transmission path of the illumination light beam and configured to convert the illumination light beam into the image light beam;
• and
• a projection lens, disposed on a transmission path of the image light beam and configured to project the image light beam out of the projection device.