| 摘要 |
PURPOSE:To compose the zoom lens for a compact LS camera of a small number of lens elements and to reduce the cost by composing the lens system of three lens groups and making both surfaces of at least one lens aspherical. CONSTITUTION:The zoom lens consists of three elements, i.e. a 1st lens group with positive refracting power, a 2nd lens group with positive refracting power, and a 3rd lens group with negative refracting power in order from the object side, and the air intervals of the respective lens groups are varied to vary the focal length of the whole system. Then at least one lens is a both-surface aspherical lens. When both surfaces of the most object-side lens in the 1st lens group are made aspherical, the comatic aberration at the peripheral part of the image plane which can not be suppressed by the front surface when one surface is aspherical is compensated by the rear surface. At this time, the rear surface compensates even the spherical aberration. Further, the aspherical surfaces in the 1st lens group are used to compensate the distortion. When the both-side aspherical surface lens is used, correction is performed excessively by the front surface and the spherical aberration which is corrected excessively is compensated by the rear surface.
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