| 摘要 |
<p>A small-sized optical system for shooting an image having a 360° omnidirectional angle of filed without adversely influenced by the flare light and a high resolution or projecting an image at a 360° omnidirectional angle of filed. The optical system has a front group (10) including two reflective surfaces and two transmissive surfaces all being rotationally symmetrical with respect to the center axis (1), a rear group (20) being rotationally symmetrical with respect to the center axis and having a positive power, and an aperture (5) coaxial with the center axis. A light beam entering the front group travels through a first transmissive surface (11), is reflected by a first reflective surface (12) provided on the opposite side to the first transmissive surface with the center axis interposed toward the opposite side to the image plane, reflected by a second reflective surface (13) disposed on the same side as the first transmissive surface toward the image plane, exits outside from a transparent medium through a second transmissive surface (14), travels through the rear group (20), and focused onto an image plane (30). The entrance pupil (6Y) in the cross-section including the center axis (1) is disposed near the second reflective surface (13).</p> |
