| 摘要 |
Disclosed is a lens system which includes a first lens of negative optical power having a meniscus shape whose convex surface faces a front, a second lens of positive optical power forming a biconvex shape, an aperture stop, a third lens of negative optical power forming a biconcave shape, a fourth lens of positive optical power, and a fifth lens of positive optical power forming a biconvex shape, which are disposed in order from the front to a rear. Lens intervals, materials composing the lenses, and the like are specified, thereby obtaining a lens system in which a sufficient back focal distance is kept, and which is small in size, low in cost, and satisfactory in optical performance.
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