| 摘要 |
PURPOSE:To obtain an optical path bending type projection lens which has excellent image forming characteristics and temperature characteristics by providing an aspherical reflection mirror with a toric surface. CONSTITUTION:A lens barrel 8 incorporates the 1st positive group 13, the 2nd group 17 consisting of the aspherical reflection mirror, the 3rd group 18 consisting of two lens elements 14 and 15, and the 4th negative group 16 successively from a screen side to a projection tube side. The surface shape of the aspherical reflection mirror of the 2nd group is made toric so as to suppress astigmatism. In another way, at least one toric lens may be used as a lens element in the 1st positive group 13 or the 3rd positive group 18. Further, a glass lens is put in partial charge of the majority of the power of the 3rd positive group to improve the temperature characteristics. |
