The utility model discloses an optical
system and a projection device, and relates to the technical field of
optics, and the optical
system is provided with a
first light-emitting
assembly, a spectroscope, a collimating lens group, a fluorescent wheel and a second light-emitting
assembly which are sequentially arranged along a first direction, and the second light-emitting
assembly is located at one side of the spectroscope along a second direction; the spectroscope is obliquely arranged, and a reflecting part is arranged on the side face, facing the fluorescent wheel, of the spectroscope; the fluorescent wheel comprises an
aluminum substrate, the
aluminum substrate is configured to rotate around a rotating shaft, the rotating axis of the
aluminum substrate is parallel to the first direction, a groove is formed in the side, facing the collimating lens, of the aluminum substrate, and the inner wall face of the groove is coated with fluorescent
powder; according to the optical
system, the
first light-emitting assembly, the spectroscope, the collimating lens group, the fluorescent wheel and the second light-emitting assembly are reasonably distributed, and the groove is formed in the aluminum substrate, so that the optical system is good in
light source uniformity and high in
optical efficiency.