| 摘要 |
PROBLEM TO BE SOLVED: To make observable the transmitted ray of subjects of different sizes with the maximum resolution by changing the reduction rate of a transmitted ray image in a state of the positional relationship of an X-ray sensitive image surface and a pickup element fixed. SOLUTION: A zoom lens 5 is a lens system capable of variably setting only a focal length without changing the position of an image surface, and the transmitted ray images 41, 42 formed on an X-ray sensitive image surface 4 are focused on the pickup element 6 of a TV camera 71 with an arbitrary reduction rate. In the examination of a subject 31 of a size corresponding to the whole visual field W, the zoom lens 5 is variably operated, and the transmitted X-ray 41 of the subject 31 is approximately equalized to a pickup area of the pickup element 6. The pickup element 6 picks up the transmitted X-ray 41 with high resolution, and displays a picked-up image plane onto a monitor 72. Further, in the examination of a subject 32 occupying only a part (w) of the visual field W, the transmitted X-ray 42 of the subject 32 is focused with a size approximately same as the whole pickup area of the pickup element 6 by the variable operation of the zoom lens 5 to pick up the image with high resolution.
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