| 摘要 |
The invention relates to an optical system that is capable of taking images having a wide angle-of-view in simplified construction, is of small-format size and well corrected for aberrations, and has high resolving power. The optical system is an imaging system that is to image an object plane (4) having a rotationally symmetric concave shape about a center axis (1) on a planar image plane (5) orthogonal to the center axis and comprises a refracting element (3) formed of a transparent medium including a first transmitting surface (31) rotationally symmetric about the center axis (1) and extending along said object plane (4) and a second transmitting surface (32) rotationally symmetric about the center axis (1) and having a refractive index of greater than 1. A light beam from the object plane (4) is imaged on the image plane (5) through the refracting element (3). The second transmitting surface (32) is concave on the image plane (5) side and has negative power at a position off the center axis (1) and in a section including the center axis (1).
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