| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an imaging lens composed of four pieces lenses with a countermeasure for attached dust recently becoming a great problem in mass production process while obtaining higher performance in a smaller size than a conventional type and without influencing other specifications or productivity. <P>SOLUTION: The imaging lens for focusing a subject image on a photoelectric conversion section of a solid-state imaging element is composed of: a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens with at least one surface that is an aspherical surface having inflection points in positions other than an intersection with the optical axis and having negative refractive power. In this case, the first lens, the second lens and the fourth lens are fixed to an imaging surface and focusing is carried out by moving the third lens in the direction of the optical axis and the following conditional expression is satisfied. 0.7<f3/f<1.3 when f3: focal distance of the third lens and f: focal distance of the whole imaging lens system. <P>COPYRIGHT: (C)2012,JPO&INPIT |
