| 摘要 |
Catadioptric optical systems are disclosed that comprise, objectwise to imagewise, a positive first lens, a meniscus second lens having a convex face oriented objectwise, a meniscus third lens having a concave face oriented objectwise, and a concave spherical mirror having a concave face oriented objectwise. Light from an object passes through the first through third lenses and reflects from the concave mirror to form an image between the third lens and the concave mirror. The system satisfies the condition |f123|/f>10, where f123 is the aggregate focal length of the first through third lenses, and f is an overall focal length of the system. The first and second lenses are preferably made of a specified optical material, collectively have a positive refractive power, and fulfill the condition |f12|/|f'12|>1, where f12 is the aggregate focal length of the first and second lenses, and f'12 is the focal length of a lens that would be formed by filling the space between the first and second lenses with the specified optical material. The system can also have a fourth lens positioned between the concave mirror and the image plane for correcting image plane curvature.
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