Illumination system and projection device

A projection device, comprising an illumination system, a light valve and a projection lens, wherein

• the illumination system is configured to provide an illumination beam, and comprises a laser light source, a wavelength conversion module, and a polarization conversion unit, wherein
• the laser light source is configured to provide a laser beam,
• the wavelength conversion module has a wavelength conversion region, and the wavelength conversion module is deposed on a transmission path of the laser beam, wherein the laser beam is converted into a wavelength conversion beam by the wavelength conversion region, a part of the wavelength conversion beam has a first polarization state, and another part of the wavelength conversion beam has a second polarization state, and
• the polarization conversion unit is located between the wavelength conversion module and the laser light source, wherein the polarization conversion unit has a plurality of first polarization conversion regions and a plurality of second polarization conversion regions, wherein the polarization conversion unit comprises a plurality of phase delay sheets correspondingly located on a plurality of surfaces facing the laser light source and located in the plurality of second polarization conversion regions of the polarization conversion unit, the wavelength conversion beam with the second polarization state leaves the polarization conversion unit after passing through a surface of the polarization conversion unit located in the plurality of first polarization conversion regions facing the laser light source, and the wavelength conversion beam with the first polarization state leaves the polarization conversion unit after passing through the phase delay sheet located in the second polarization conversion region,
• the light valve is deposed on a transmission path of the illumination beam, and is configured to convert the illumination beam into an image beam;
• and
• the projection lens is deposed on a transmission path of the image beam, and is configured to project the image beam out of the projection device.