| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an imaging optical system and the like consisting of compact wide-angle lenses of which various aberrations are satisfactorily corrected. <P>SOLUTION: The imaging optical system comprises, in order from the object side, four lenses: a first biconvex lens having positive refractive power; a second biconcave lens having negative refractive power; a third meniscus lens having positive refractive power with its concave surface facing the object side; and a fourth biconcave lens having negative refractive power. A diaphragm is disposed closest to the object side, and the imaging optical system satisfies the following conditional formulae: -0.9<f4/f<0---(1) and -0.04<(r8+r9)/(r8-r9)<1.3---(2), where f4 is a paraxial focal length of the fourth lens, f is a focal length of the whole imaging optical system, r8 is a radius of curvature of the object side surface of the fourth lens, and r9 is a radius of curvature of the image side surface of the fourth lens. <P>COPYRIGHT: (C)2012,JPO&INPIT |
