| 摘要 |
PURPOSE:To obtain a lens system which can compensate aberration in excellent manner even with small size having performance of F3.5-2.8, angle of view 84 deg.-92 deg. and fB 1.4-1.7, by constituting the lens system with 7 groups and satisfying a prescribed condition. CONSTITUTION:A lens system consists of the 1st group of positive meniscus lens, the 2nd and 3rd groups of negative meniscus, the 4th group comprising positive single, combined or split lens, the 5th group comprising negative combined or split lens, the 6 group of psitive meniscus, and the 7 group of positive lens. The relation of 0.5f<¦f123¦<0.75f and f123<0, 0.5f<D4+D5<0.9f is satisfied, where f123 and (f) are resultant focus of the 1st-3rd groups and the overall system and D4 and D5 are the thickness of the 4th and 5th lenses respectively. The relation for the 5th group with combined lens is nb'-nb<0.1 and rb<0, where (rb) is bonded plane taken concave for aperture, and (nb) and (nb') are refractive index before and after the bonded plane. |
