| 摘要 |
An imaging optical element is comprised of a gradient index rod lens 12 of which external peripheral surface is a smooth surface without being processed by means of a flare-cut treatment and a field limitation stop member 14 mounted on the lens surface at the incidence side thereof. As for the stop member, the length t thereof is: t>lo.D/2X (where, lo: a lens working distance, D: a rod lens diameter, X: a radius of field of view), whereby the angle of incidence of beam theta at the center of the lens satisfies theta<tan-1(X/lo). It is effective especially when an application thereof is made to a rod lens array comprised of a plurality of rod lenses arranged into an array.
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