To provide an optical system of a projected display device for preventing generated stray light without sacrificing brightness of projected images even when using DMD, and to provide the projected display device.
A projection lens 20 has a lens group comprising four groups of first lens group G1 to fourth lens group G4. A diaphragm 26 is arranged to be made eccentric between a second lens group G2 and a third lens group G3. In zooming, the second lens group G2, the diaphragm 26 and the third lens group G3 are integrated to be moved on an optical axis. On-light 51 is incident from the fourth lens group G4 to be emitted from the first lens group G1, diaphragm position is changed in zooming, even when zero degree light 52 being unnecessary light passes the diaphragm 26, the zero degree light 52 being the unnecessary light passing the diaphragm 26 strikes a lens holding member 29 of the second lens group G2, and a cross section provided there is reflected with a saw blade-like shading part 27 not to emit light to the outside of the second lens group G2.
SHOJI EISAKU
NAKAE NOBUYUKI
Ishibashi Masayuki
Masaaki Ogata
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