Patent ID: 6301063
Filing Date: 2001-10-09
Classification: G02B

Abstract:
A color image readout lens comprising, successively from an object side, a first lens group comprising a lens having a positive refracting power with a convex surface directed onto the object side, a second lens group, comprising a biconvex lens and a biconcave lens cemented thereto, with a convex surface directed onto the object side, a third lens group comprising a biconcave lens and a biconvex lens cemented thereto, having a negative refracting power as a whole with a convex surface directed onto an image side, a fourth lens group comprising a positive lens with a convex surface directed onto the image side, and a fifth lens group comprising a negative meniscus lens with a stronger concave surface directed onto the object side;said color image readout lens further satisfying the following conditional expressions (1) to (3):61.5<.nu..sub.2, 0.006<.delta..theta..sub.2 (1)61.5<.nu..sub.5, 0.006<.delta..theta..sub.5 (2)0.06<(.phi..sub.2 /.phi..sub.T).multidot..delta..theta..sub.2 +(.phi..sub.5 /.phi..sub.T).multidot..delta..theta..sub.5 <0.14 (3)where .phi..sub.T is the refracting power of the whole system; .phi..sub.i, .nu..sub.i, and .delta..theta..sub.i are the refracting power, dispersion, and anomalous dispersion with respect to g-d line of the i-th lens from the object side, respectively; d.sub.j is the j-th surface space from the object side; and .delta..theta. is the anomalous dispersion defined by the deviation .delta..theta..sub.g,d of partial dispersion ratio .theta..sub.g,d with respect to g-d line from a reference line; .phi..sub.T, .phi..sub.i, and .nu..sub.i being obtained at e-line.