| 摘要 |
PROBLEM TO BE SOLVED: To sensitively detect the shift of an interference fringe independent of the intensity variation of electron beams by installing an opening for detecting the average intensity of electron beams in addition to comb-like openings in a slit, separately detecting intensity of electron beams passing through both openings, and using the result of arithmetic processing as an image signal. SOLUTION: A detecting part of a detector 12 is divided by a dead part 17, and the intensity I1 of a probe beam 4 passing through a comb-like opening and the intensity I0 of the probe beam 4 passing through a large opening are independently outputted. A scanning deflector 8 is driven with a scanning control device 13 to scan both probe beams 4, I1/I0 is operated with a signal arithmetic unit 15, and a scanning image using operated result as a brightness signal is formed with an image forming device 14. Even when the intensity of both probe beams 4 is varied, an image whose contrast periodically changes to the shift of an interference fringe, that is, a contour image of the variation of the magnetic flux amount passing through between the probe beams 4 can be obtained.
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