| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens of a wide angle of view suitable for a video camera without complicating lens constitution and lens frames by specifying the constitution of lenses. SOLUTION: This lens system of the wide angle of view is composed, successively from an object side, of a first group having positive refracting power, a second group having negative refracting power and a third group having positive or negative refracting power a fourth group having positive refracting power. The second group and the fourth group are moved at the time of variable power and the fourth group moves monotonously from the wide angle end to the object side toward the object side; in addition, the conditions 0<f4 /f1 <0.45 and -1.6<β4 T<-0.5 are satisfied. In the equations, f1 is the focal length of the first group, f4 is the focal length of the fourth group,β4 T is the magnification at the telephoto end of the fourth group. This zoom lens moves monotonously from the wide angle end to the object side toward the telephoto end and the fourth group is provided with the main variable power effect. Since the variable power effect in the second group is thereby decreased, and refracting power of the first group is made smaller and the wider angle of view is obtd.
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