| 摘要 |
A projection lens consists of a first lens group including a positive lens, a second lens group including a meniscus type lens having a comparatively low refractive power, a third lens group including a bonded negative lens, a fourth lens group including a double convex lens, a fifth lens group including a lens having a comparatively low positive refractive power and a sixth lens group including a negative lens having a concave surface at the screen side, whereby, when a lens power of the whole lens system is 1 and a lens power of each lens group is designated by psi X(1-6), respective lens powers will be given by the following a-e: 0.1< psi 1<0.6a -0.2< psi 2<0.2b -0.5< psi 3<-0.1c 1.0< psi 4.5<1.5d -1.3< psi 6<-0.7e thus providing a temperature compensation by partly employing plastic component lenses for minimizing the efficiency from worsening, and then provided is a light weight projection lens with only six lens group while maintaining a high aperture ratio and high imaging power such as suited for a high definition television system.
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