| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an inexpensive wide-angle lens system which has various aberrations excellently corrected from the visible light range to the near-infrared range, and has an angle of view exceeding 70°. <P>SOLUTION: The wide-angle lens consists of a first negative meniscus lens 11 which has a convex surface on an object side, a second lens 12 which has positive power, a third biconvex lens 13, and a fourth negative meniscus lens 14 which has a convex surface on an image side. Here the wide-angle lens satisfies a conditional expression (7')0.032<A-B<0.06 while A=(nt3-1)×(1-nt4)/(R7×R8/f<SP POS="POST">2</SP>) and B=(nd3-1)×(1-nd4)/(R7×R8/f<SP POS="POST">2</SP>), where nt3 is a refractive index on a t line of the third lens, nt4 is a refractive index on a t line of the fourth lens, nd3 is a refractive index on a d line of the third lens, nd4 is a refractive index on a d line of the fourth lens, R7 is a radius of curvature of an image-side surface of the third lens, R8 is a radius of curvature of an object-side surface of the fourth lens, and f is the focal length of the whole system. <P>COPYRIGHT: (C)2013,JPO&INPIT |
