| 摘要 |
A high performance fixed focal length optical imaging system for example for a cine camera is operable to receive radiation from an object space and deliver the received radiation through the optical system so as to form an image at an image surface in an image space. The optical system comprises: a first positively powered lens group (501) and a second positively powered lens group (502) arranged in that order from object space to the image space of the optical system and aligned on a common optical axis, wherein the first positively powered lens group comprises a plurality of optical elements wherein at least one of the plurality of optical elements is stationary and at least one of the plurality of optical elements has an aspheric optical, surface, and the second positively powered lens group comprises at least one optical element and is operable to move axially along the common optical axis for focusing the imaging system, wherein at least one optical element of the second lens group has an aspheric optical surface. The imaging system has the advantage of providing high relative illumination and high contrast at elevated spatial frequencies even when using a fast aperture.
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