| 摘要 |
An ultra wide angle zoom lens for a projection display system, includes: a liquid crystal panel displaying an image; a first lens group having a positive refractive power, formed by combination of two or more lenses, and correcting chromatic and spherical aberrations of incident light from the liquid crystal panel; and a total reflection mirror reflecting the incident light from the first lens group in a predetermined direction; a second lens group having a negative refractive power, formed by combination of two or more lenses, and correcting distortion and astigmatism of the incident light from the total reflection mirror. Here, a projection lens is constructed so that a magnification of the projection lens is adjusted by movement of the first lens group along an optical axis, and the second lens group is moved forward and backward according to the adjusted magnification of the projection lens so that a lens focusing can be adjusted, thereby satisfying the following equation: 3.2<bf1/f1<3.5; 0.75<f1/f2<1.0; and 5.0<d8/f1<7.0. Here, 'bf1' is a rear focal distance, 'f1' is a focal distance of the whole lenses, 'f2' is a focal distance of the second lens group and 'd8' is a distance between the first lens group 70 and the second lens group.
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