| 摘要 |
A compact lens has a front lens group of positive refractive power and a rear lens group of negative refractive power. The front lens group is composed of, in order from a photographic object side, a negative lens element and a biconvex lens element having a surface of stronger curvature on the object side. Overall symmetry with respect to the rear lens group is achieved by using a negative meniscus lens element with its concave surface on the object side for the negative lens element in the front lens group. The rear lens group is composed of a negative meniscus lens element L3 with its concave surface on the object side. This provides a compact overall lens structure of the so-called telephoto type having only three lens elements, making it possible to boost optical performance while being inexpensive. In addition, by satisfying certain conditional equations, it is possible to establish a good balance between the imaging performance at perimeter field angles and the compactness of the lens system as a whole.
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