| 摘要 |
The invention relates to an optical system which is adapted to form an image having a full 360° (panoramic)-direction angle of view on an image plane or project an image located on an image plane in a full 360° (panoramic)-direction angle of view, and which is of small-format size and has reduced light flare and high resolving power. The optical system comprises a front unit (10) having at least two reflecting surfaces (11, 12), each rotationally symmetric about a center axis (1), and a rear unit (20) that is rotationally symmetric about the center axis and has positive power. The first reflecting surface (11) is located opposite to an entrance pupil (6Y), and the second reflecting surface (12) is located on the same side as the first reflecting surface (11). The entrance pupil (6Y) in a section including the center axis is located between the outer periphery of the first reflecting surface (11) and the outer periphery of the second reflecting surface (12). A light beam coming from afar passes through the front unit (10) and the rear unit (20) in order, forming an image at a position of an image plane (30) off the center axis. The entrance pupil (6Y) is positioned off the center axis in the section including the center axis, and an entrance pupil (6X) is positioned on the center axis in a section that is orthogonal to the section including the center axis. The rear unit (20) is constructed of at least two groups.
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