| 摘要 |
A non-spherical single lens comprises a first surface which is a non-spherical surface, the first surface being substantially zero in the curvature thereof near the optic axis and being of a non-spherical shape gradually displaced outwardly away from the optic axis, and a second surface which is a convex spherical surface of a radius of curvature r, ¦r¦ being a value equal or approximate to d which is the thickness of the lens.
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