| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a compact and light-weight inner focus type fixed-focus lens having superior imaging performance. <P>SOLUTION: A fixed focus lens comprises, in order from the object side, a first lens group G<SB POS="POST">11</SB>having a positive refractive power; a second lens group G<SB POS="POST">12</SB>having a negative refractive power; and a third lens group G<SB POS="POST">13</SB>having a positive refractive power. The first lens group G<SB POS="POST">11</SB>comprises, in order from the object side, a positive lens L<SB POS="POST">111</SB>, a positive lens L<SB POS="POST">112</SB>, a negative lens L<SB POS="POST">113</SB>, a negative lens L<SB POS="POST">114</SB>, and a positive lens L<SB POS="POST">115</SB>. An aperture stop ST for regulating a predetermined aperture is disposed between the negative lens L<SB POS="POST">113</SB>and the negative lens L<SB POS="POST">114</SB>. The first lens group G<SB POS="POST">11</SB>is fixed. The second lens group G<SB POS="POST">12</SB>comprises a negative lens L<SB POS="POST">121</SB>. The second lens group G<SB POS="POST">12</SB>moves along the optical axis to perform the focusing. The third lens group G<SB POS="POST">13</SB>comprises a positive lens L<SB POS="POST">131</SB>. The third lens group G<SB POS="POST">13</SB>is also fixed. <P>COPYRIGHT: (C)2012,JPO&INPIT |
