| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a small inner focus type optical system having a small, lightweight focusing group and a vibration-proof group and having an excellent imaging performance. <P>SOLUTION: The inner focus type optical system according to the present invention comprises, in order from an object side, a first lens group G<SB POS="POST">11</SB>of positive refractive power, a second lens group G<SB POS="POST">12</SB>of negative refractive power, a third lens group G<SB POS="POST">13</SB>of positive refractive power, and fourth lens group G<SB POS="POST">14</SB>of negative refractive power. The third lens group G<SB POS="POST">13</SB>is composed of a single positive lens L<SB POS="POST">131</SB>. Focusing from the state of focusing on an infinity object to the state of focusing on a shortest-distance object is carried out by moving the third lens group G<SB POS="POST">13</SB>from an imaging surface IMG side to the object side along an optical axis. <P>COPYRIGHT: (C)2013,JPO&INPIT |
