| 摘要 |
PROBLEM TO BE SOLVED: To provide a miniaturized reading lens in which various aberrations such as a color aberration at first are satisfactorily corrected in a spite of a large aperture of about F3 and having a high resolution by including at least one refractive index distributed lens satisfying specified conditions. SOLUTION: This lens is composed of three groups and three lenses of a first lens G1 consisting of the first group of positive power, a second lens G2 consisting of the second group of negative power and a third lens G3 consisting of the third group of positive power in order from the side of magnification. Then, at least one refractive index distributed lens GRIN satisfying the condition of|ϕs|<|ϕm|is included. Provided that,ϕs shows the power of the form of the refractive index distributed lens andϕm shows the power of the medium of the refractive index distributed lens. Since the satisfactory aberration correction is realized by an aberration correction effect of which this refractive index distributed lens GRIN has, large aperture expansion and miniaturization can be achieved by about a half of the conventional number of constitutive lenses.
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