| 摘要 |
An image pick-up lens system includes an aperture stop ( 10 ), a first lens ( 20 ), and a second lens ( 30 ) having a concave surface on an object side. The aperture stop, the first lens and the second lens are aligned in that order from the object side to an image side. The first lens has positive refracting power and has a diffraction grating formed on a convex surface on the image side. The second lens has positive refracting power. The system satisfies the following condition: (1) 1.4<T/f<1.7, wherein f is a focal length of the system, and T is a length from the aperture stop to an image pick-up surface ( 50 ) of the image side. Condition (1) limits the total length of the system in order to provide compactness. The system also satisfies other conditions (2)-(5) as disclosed, in order to provide compactness, cost-effectiveness and improved optical performance.
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