| 摘要 |
<P>PROBLEM TO BE SOLVED: To accommodate wavelength bands from visible to near infrared while suppressing enlargement of a lens system in a zoom lens, and to achieve both a high magnification ratio and a high performance. <P>SOLUTION: A zoom lens includes: a first lens group G1 having positive refractive power; a second lens group G2 having negative refractive power; a third lens group G3 having positive refractive power; and a fourth lens group G4 having positive refractive power, in order from an object side. The zoom lens is configured to change focal distances of all systems by changing a mutual interval by moving the second lens group G2 and the third lens group G3 along with an optical axis. The first lens group G1 has two sets of joint lenses joining a negative meniscus lens and a positive lens together in order from the object side, and a positive lens. When a focal distance of the first lens group G1 is defined as fG1 and a focal distance of all the systems in a telephoto terminal is defined as ft, a conditional expression (1) of 0.14<fG1/ft<0.26 is satisfied. <P>COPYRIGHT: (C)2012,JPO&INPIT |
