Abstract: In a four-sheet lens configuration composed of convex, concave, convex, and concave lenses, predetermined conditional expressions are satisfied so as to attain a compact size and a wider field angle in a lens system for reading out images, while correcting various kinds of aberration. Further, a bright lens system is obtained. Successively from the object side, a first lens (L.sub.1) comprising a positive meniscus lens with a convex surface directed onto the object side, a second lens (L.sub.2) comprising a biconcave lens, a third lens (L.sub.3.sub.)comprising a biconvex lens, and a fourth lens (L.sub.4) comprising a negative meniscus lens with a convex surface directed onto an imaging surface side are disposed, while the following conditional expressions (1) to (3) are satisfied:0.87<f(1/R.sub.8 -1/R.sub.7)<2.75 (1)0.23<R.sub.1 /f<0.38 (2)1.08<.vertline.N.sub.4 .multidot.f.sub.4 .vertline./f<3.