| 摘要 |
To provide a high-brightness, small, low-cost optical apparatus which covers a wide-angle to super-wide-angle region and which reliably corrects various aberrations with a small number of lenses. At least one negative lens unit 1, a meniscus lens 2 that is convex on an object side, an aperture stop S, and a double-convex positive lens 3 are arranged in order from the object side. At least one of the lenses positioned on the object side of the aperture stop S and the positive lens 3 include respective aspherical surfaces. When va is an average Abbe number of all of the lenses excluding the meniscus lens, vb is an Abbe number of the meniscus lens, f is a focal length of the entire system, f12 is a combined focal length of the negative lens unit and the meniscus lens, ts is a distance between the aperture stop and the positive lens along an axis, L is a distance between a vertex of a lens surface nearest to the object side and a vertex of a lens surface nearest to the image side, t2 is a central thickness of the meniscus lens, thetas is an incident angle of a chief ray that passes through the aperture stop at a maximum angle of view, 1.4<va/vb, 0<ts/L<0.1, 0.2<t2/L<0.5, -10<f12/f<-1.0, and 25°<thetas<40° are satisfied.
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