| 摘要 |
PURPOSE:To improve productivity and spherical aberration characteristics with small- sized, lightweight constitution by forming a prescribed distributed index lens and satisfying specific expressions as to refractive indexes, a constant of a refractive index distribution, radii of curvature of surfaces, focal lengths, a numerical aperture, and angles of normals to the surfaces and an optical axis. CONSTITUTION:The distributed index lens which has parallel cylindrical incidence and projection surfaces and a refractive index shown by an equation I at distance (r) from the center axis satisfies expressions II-VIII. The equality II which specifies the radius R of curvature of a surface allows numbers of lenses having parallel incidence and projection surfaces to be polished at the same time and reduces the cost and the inequality III limits the center and outermost peripheral refractive index of the lens; the inequality V corrects the spherical aberration, and the inequality VI reduces the size of the lens, the inequality VII collimates light intensely, and the inequality VIII prevents reflected light from a surface to a light source 1. Thus, the productivity is improved with the small-sized, lightweight constitution to reduce the manufacture cost.
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