| 摘要 |
PURPOSE:To simplify lens constitution and to reduce the size thereof by constituting a titled lens of a 1st lens group having a negative focal length, 2nd lens group having a positive focal length, and 3rd length group having a negative focal length, constituting the entire system as 6-groups 6-elements lenses and forming these lenses so as to satisfy the specific condition. CONSTITUTION:The 1st lens group consists of a piece of negative meniscus lens (1st lens) with the concave face directed to an object side and the 2nd lens group consists of 4 groups 4 elements which are, successively from the object side, a positive 2nd lens, negative 3rd lens, negative 4th lens, and positive 5th lens. The 3rd lens group consists of a piece of negative meniscus lens (6th lens) with the concave face directed to the imaging side and the entire system is constituted of the 6-groups 6-elements lenses. The condition expressed by the equation 0.3<fH/fM<0.9 is satisfied. In the equation fM is the focal length of the entire system of the lens at unmagnification, fH is the focal length of the 2nd lens group. In addition, the 1st lens and 6th lens, 2nd lens and 5th lens, 3rd lens and 4th lenses are respectively of the same shape and symmetrical type. The extremely simple lens is thereby obtd. and a high effect is obtd. in the reduction of the size and cost thereof.
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