| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging device equipped with a zoom lens which is made more inexpensive and more compact than the conventional one while satisfying desired image-forming performance. SOLUTION: This imaging device is equipped with a zoom lens system forming an optical image with light from an object and an imaging device converting the optical image formed by the zoom lens system to an electronic video signal. The zoom lens system consists of a 1st lens group having positive power, a 2nd lens group having negative power, a 3rd lens group having positive power and a 4th lens group having positive power in order from the object side and is constituted to vary power by fixing the 1st lens group and the 4th lens group and moving the 2nd lens group and the 3rd lens group on an optical axis so that a space between the respective lens groups may be changed. The 1st lens group consists of a homogeneous single lens and the zoom lens system satisfies 6.9<f1/fw<250, provided that f1 is the focal distance of the 1st lens group and fw is the focal distance of an entire system at a wide-angle end.
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