| 摘要 |
<p>[PROBLEMS] To provide a small-size inexpensive optical device covering a wide angle and ultra-wide angle range and having preferably corrected aberrations with a small number of sheets. [MEANS FOR SOLVING PROBLEMS] The optical device includes at least one negative lens group (1), a meniscus lens (2) convex at an object side, an aperture stop (S), a biconvex positive lens (3) arranged in this order from the object side. One of the lenses at the object side from the aperture stop (S) and the positive lens (3) have aspheric surfaces, respectively. When an average Abbe constant excluding the meniscus lens is va, the Abbe constant of the meniscus lens is vb, the focal distance of the entire system is f, the synthesized focal distance of the negative lens group and the meniscus lens is f12, the distance between the stop and the positive lens on the axis is ts, the length from the apex of the lens surface nearest to the object to the apex of the lens surface nearest to the image is L, the central thickness of the meniscus lens is t2, and the angle of the main ray of the maximum angle of view passing through the stop is ?s, the following relationships are satisfied: 1.4 < va/vb, 0 < ts/< L <0.1, 0.2 < t2/L < 0.5, -10 < f12/f < -1.0, 25 degrees < ?s < 40 degrees.</p> |
