| 摘要 |
PROBLEM TO BE SOLVED: To excellently correct chromatic aberration and Petzval's sum by constituting a lens of a homogeneous lens having negative refractive power and a specified radial type refractive index distribution lens which has positive refractive power and in which a refractive index is distributed in a radial direction from an optical axis, bringing the plane shaped parts of both lenses into contact with each other and satisfying a specified condition. SOLUTION: This lens is constituted of the homogeneous lens having the negative refractive power and one radial type refractive index distribution lens which has the positive refractive power and in which the refractive index is distributed in the radial direction from the optical axis, and is expressed by an expression N(r)=N00 +N10 r<2> +N20 r<4> ; and both surfaces of refractive index distribution lens are plane and at least one-side surface of the homogenous lens is plane, and the plane shaped parts of both lenses are brought into contact or stuck to each other and they satisfy a condition: 1/V10 <1/νh . Provided (r) expresses a distance from the optical axis in the radial direction, N(r) expresses the refractive index distribution at a point being the distance (r), N10 expresses the coefficient of 2i-order refractive index distribution, andνh expresses the Abbe number of the homogeneous lens, and V10 expresses dispersion corresponding to the coefficient of the 2i-order refractive index distribution of the refractive index distribution lens.
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