| 摘要 |
PURPOSE:To miniaturize the titled lens so as to be built in a camera and to efficiently correct various aberrations by allowing the lens to have a negative focal distance as a whole and arranging three groups consisting of the 1st negative lens, the 2nd positive lens and the 3rd negative lens successively from the object side with specific relation. CONSTITUTION:The lens system has the negative focal distance as a whole, consists of three groups of a 1st negative lens, a 2nd positive lens and a 3rd negative lens arranged successively from the object side and, when the focal distance is fc, the focal distance, a refractive index and Abbe number of the i-th lens from the object side are fi, ni and Vi, the radius of curvature on the i-th refractive face is ri and the i-th face interval is di, the lens system is constituted so as to satisfy the conditions shown by inequalities. Consequently, the lens system can be extremely miniaturized, can be built in the body of a lens shutter camera, and even when the lens system is optionally combined with a main lens in accordance with necessity, the aberration is efficiently corrected and a photograph of high quality can be obtained.
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