| 摘要 |
PROBLEM TO BE SOLVED: To obtain a projection lens projecting the original picture of a projection image by excellently correcting trapezoidal distortion or distortion aberration in an oblique direction by allowing the projection lens to have at least one lens surface without axial symmetric property. SOLUTION: The projection lens LP is provided with two lens groups L1 and L2 and a variable power action is executed to a telephone end from a wide angle end by moving both groups to a screen S side so that a gap between them is reduced. Thus, the size of the projection image projected on the screen S can be varied. That means, the screen S and the projection image LCD are mutually in parallel and both of them are orthogonally crossed in the optical axis Ax direction of the lens LP. Then, the projection image is enlarged and projected with the various kinds of magnification on the screen S by the lens LP. Besides, the lens surface ZRN without the axial symmetric property is used as the lens surface (r1) of the group L1 on the screen S side. By using the aspherical surface ZRN without the axial symmetric property in such a way, the various kinds of aberration (distortion) is effectively corrected.
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