大相对孔径数字化X射线成像系统的光学设计

Low F~# digital X-ray radiography system

针对60mm×45mm尺寸碘化铯荧光屏,设计一个用于牙科诊断的X射线数字化成像光学系统。选用有效尺寸4.8mm×3.6mm的CCD作为接受器件,光学系统结构型式为复杂化双高斯型,相对孔径和全视场角分别达到F/0.9和35°,有效焦距9mm。全视场MTF在空间频率56lp/mm时高于0.75,全视场畸变为1.8%,边缘视场照度与中心视场照度之百分比达到80%。从设计结果可以看出,整个系统的像差得到了较好的校正,满足数字化X射线成像系统的使用要求。

An optical system of digital X-ray radiography based on CsI scintillation screen with 60 mm×45 mm dimension for dental diagnosis was designed.A CCD with a 4.8 mm×3.6 mm image surface was selected.The lens system had a complicated double-Gauss configuration.The F# and full field of view were up to F/0.9 and 35° respectively,the focal length was 9mm.The results showed that the modulation transformation function of full field of view was greater than 0.75 at the spatial frequency of 56 lp/mm,the distortion of full field of view was 1.8%,and the relative illumination reached 80%.The aberrations of the whole system were corrected,which met the requirements for the digital X-ray radiography system.