To allow reading angle to be wider and to improve the quality of the read picture at a low cost by using a four lens constitution and satisfying special conditions.

A first lens L1 is a positive meniscus lens having a convex face on an objective body side. A second lens L2 is a both concave face lens in which one of the concave faces, that has a larger curveture, faces toward an image forming surface side. A third lens L3 is a both convex face lens having same curvetures. A fourth lens L4 is a negative meniscus lens having a convex face on an image forming side. These lenses satisfy -5.5<f12/f<-28, 0.36<f3/f<0.46, -1.14<f2/f3<-0.8, -8.8<f4/D6<-6.0 and 0.23<R1/f<0.34 where (f) is the focal distance of the entire system, f12 is the combined focal distance of the lenses L1 and L2, f2 is the focal distance of the lens L2, f3 is the focal distance of the lens L3, f4 is the focal distance of the lens L4, R1 is the radius of the curveture of a first surface and D6 is the distance from a sixth surface to a seventh surface.