| 摘要 |
Along an optical axis from an object side to an image side, a short overall length imaging lens system with four lenses includes a first lens with positive power that is a meniscus spherical/aspherical lens with a convex surface on the object side; an aperture stop; a second lens with negative power that is a meniscus aspherical lens with a convex surface facing the object side; a third lens with positive power that is a meniscus aspherical lens and a concave surface on the object side; and a fourth lens with negative power that is a biconcave aspherical lens with at least one inflection point in the effective diameter range of the optical surface on the image side so as to make the positive power gradually change into negative power. Moreover, the imaging lens system satisfies the following conditions: 0.25 ≤ d 2 + d 4 + d 6 f s ≤ 0.40 ; 0.8 ≤ Y · tan ( ω ) Bf ≤ 2.7 Thereby the imaging lens system provides good aberration correction with reduced overall lens length. Moreover, due to simple shape of the optical surface of each lens, the lens is easy to be produced, the lens system is minimized and the cost is reduced.
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