| 摘要 |
An ocular zoom lens is formed of three lens groups, of positive, positive, and negative refractive power, in order from the eye-point side. The second and third lens groups are moved along the optical axis in opposite directions during zooming, and the second lens group is formed of, in order from the eye-point side, a biconvex lens and a negative meniscus lens with its concave surface on the eye-point side, with the surfaces of the biconvex lens and the negative meniscus lens that face one another having different radii of curvature and being positioned on-axis with an intervening air space. Various conditions are preferably satisfied in order to ensure sufficient eye relief using a relatively small number of lens elements while providing increased freedom of design and enabling favorable correction of aberrations even for wide image angles.
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