| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a small-sized and high-performance observation optical system, a finder device equipped with the observation optical system, and a method for manufacturing the observation optical system. <P>SOLUTION: The observation optical system for observing an object includes, in order from an object side, a first lens having positive refractive power, a second lens having negative refractive power and a concave surface on the object side, and a third lens having positive refractive power and a convex surface on an eye point side, has an aspheric surface on at least one lens surface, and satisfies the following conditions: 0.80<(R22+R21)/(R22-R21)<2.00, and 1.10<f1/(-f2)<2.00, where R21 is a curvature radius of the object side surface of the second lens, R22 is a curvature radius of the eye point side surface of the second lens, f1 is a focal distance of the first lens, and f2 is a focal distance of the second lens. <P>COPYRIGHT: (C)2012,JPO&INPIT |
