PROJECTION ZOOM LENS

摘要

PROBLEM TO BE SOLVED: To realize a projection zoom lens being suitable for a three-plate projector. SOLUTION: This zoom lens is constituted by disposing a 1st to a 5th groups in this order from an enlargement side and provided with a diaphragm S between the 3rd and the 4th groups. The 1st group G1 has negative refractive power and the 2nd group G2, the 3rd group G3, the 4th group G4 and the 5th group G5 have positive refractive power. When a projection distance is changed, the 1st group G1 is moved in the optical axis direction in order to keep the conjugate relation between a plane image and a projection image. When power is varied, the 1st group G1 and the 5th groups G5 are fixed and the 2nd group G2, the 3rd group G3 and the 4th group G4 are moved in the optical axis direction. Besides, the groups are constituted so as to satisfy conditions (1)-(4). (1) 0.3<|f1|/f2<0.6. (2) 0.5.fT/fw55.