| 摘要 |
A ultra-wide angle objective lens comprising a first group having a first lens element having a convex object surface facing the object and a concave image surface facing the image plane, and a second aspheric lens element, the second aspheric lens element having a varying power that is negative at its vertex; and that increases positively with radial distance from the vertex. A second group has at least one lens element and a positive power. A third group has at least a first and a second lens element and a positive power. The ratio of the total track to the focal length satisfies the condition that TT/fo=<33 and the image height on a focal plane is h(&thetas;)>f*&thetas;, where h(&thetas;) is the image height formed by an off-axis chief ray having a field angle &thetas;, and f is the effective focal length of the lens.
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