Abstract: An illumination system includes a light source providing a first light beam, a first light uniformizing element disposed on a transmission path of the first light beam, a wavelength conversion element, and an optical part. The wavelength conversion element is disposed on the same transmission path and converts the first light beam into a second light beam. The optical part is disposed on a transmission path of the second light beam. The wavelength conversion element is disposed between the first light uniformizing element and the optical part. The second light beam includes a first portion, which is transmitted toward the first light uniformizing element, and a second portion, which is transmitted toward the optical part, reflected by the optical part, and further transmitted and passes through the wavelength conversion element for being transmitted toward the first light uniformizing element. A projection device including the illumination system is also provided.

Abstract: An illumination system includes a light source providing a first light beam, a first light uniformizing element disposed on a transmission path of the first light beam, a wavelength conversion element, and an optical part. The wavelength conversion element is disposed on the same transmission path and converts the first light beam into a second light beam. The optical part is disposed on a transmission path of the second light beam. The wavelength conversion element is disposed between the first light uniformizing element and the optical part. The second light beam includes a first portion, which is transmitted toward the first light uniformizing element, and a second portion, which is transmitted toward the optical part, reflected by the optical part, and further transmitted and passes through the wavelength conversion element for being transmitted toward the first light uniformizing element. A projection device including the illumination system is also provided.