| 摘要 |
PROBLEM TO BE SOLVED: To excellently compensate aberration which can not be fully compensated only by a main lens system and to easily obtain high optical performance by providing an attachment lens with at least one diffraction optical element. SOLUTION: This attachment lens AL is attachably/detachably attached to the object side of the main lens system ML and the residual aberration of the main lens system ML is compensated so as to obtain the high optical performance. The lens AL is provided with at least one positive lens and one negative lens. Then, the lens AL is provided with at least one diffraction optical element and compensates the residual aberration, especially, the chromatic aberration of the main lens system ML. The diffraction optical element has an excellent effect to compensate the aberration, especially, the chromatic aberration caused on a refractive surface by the dispersion of glass. By variously changing the cylinder of cyclic structure so that an spherical lens-like effect is given, the aberration other than the chromatic aberration is reduced. |
