| 摘要 |
PROBLEM TO BE SOLVED: To increase a numerical aperture by using a specified refractive index distribution lens and a homogeneous plane/convex lens. SOLUTION: The system is constituted by combining the refractive index distribution lens 1 with refractive index distribution in a radial direction and the homogeneous plane/convex lens 2 with uniform refractive index. As for the lens 1, the lens face is flat or convexly spherical, and in the case the refractive index distribution is controlled to be n(r)<2> =n0 <2> . 1-(g.r)<2> +h4 (g.r)<4> + h6 (g.r)<6> +h8 (g.r)<8> + ...}, 1.45<=n0 <=1.80 and 0.45<=n0 .g.r0 <=0.90 are satisfied, provided that (r) denotes a distance from an optical axis, n(r) denotes the refractive index at the distance (r), (n0 ) denotes a refractive index on the optical axis, (r0 ) denotes a lens radius, (g) denotes coefficient of refractive index distribution, each of h4 and h6 ,... denotes refractive index distribution coefficient. Besides, as for the lens 2, the convex face is spherical, the lens 2 is arranged so that the optical axis of the lens 2 may be aligned with the optical axis of the lens 1, and 1.40<=n<=2.20 and 0.3r0 <=R<=2.0r0 are satisfied, provided that (n) denotes the refractive index of the homogeneous plane/convex lens 2, R denotes the radius of curvature of the convex face of the lens 2. |
