| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a variable power optical system which is able to achieve reduction in the size of an imaging apparatus and high image quality by correcting curvature of field and astigmatism. <P>SOLUTION: In the variable power optical system with a power of about three times, power arrangements of groups and curvature radii are appropriately adjusted in order to make size reduction and resolution maintenance compatible with each other. In the variable power optical system composed of a first lens group of negative refractive power and a second lens group of positive refractive power arranged in that order from object side, the second lens group is composed of a lens with positive refractive power and a lens of negative refractive power arranged in that order from object side, and satisfies the expressions given below. -2.3≤f<SB POS="POST">1</SB>/f<SB POS="POST">W</SB>≤-1.9 and 1.9≤(R<SB POS="POST">22a</SB>+R<SB POS="POST">22b</SB>)/(R<SB POS="POST">22a</SB>-R<SB POS="POST">22b</SB>)≤10, in which f<SB POS="POST">1</SB>is the focal distance of the first lens group, f<SB POS="POST">w</SB>is the focal distance of the entire system at the wide angle end, and R<SB POS="POST">22a</SB>and R<SB POS="POST">22b</SB>are curvatures of the lenses of negative refractive powers in the second lens group. <P>COPYRIGHT: (C)2012,JPO&INPIT |
