Wavelength conversion element 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 transmission path of the illumination beam and configured to convert the illumination beam into an image beam, the projection lens being disposed on a transmission path of the image beam and configured to project the image beam, and the illumination system comprising an excitation light source and a wavelength conversion element, wherein:

• the excitation light source is configured to provide an excitation beam;
• and
• the wavelength conversion element is disposed on a transmission path of the excitation beam and comprises a rotatable disc, a first spoiler structure and a second spoiler structure, wherein:
• the rotatable disc has a supporting surface and a back surface opposite to the supporting surface;
• the first spoiler structure is disposed on the supporting surface and arranged along a first track surrounding a center of the rotatable disc;
• and
• the second spoiler structure is disposed on the back surface and arranged along a second track surrounding the center, wherein a centroid of at least one of the first spoiler structure and the second spoiler structure is deviated from the center.