GB1308839A - Scanning electron microscope - Google Patents

Abstract

1308839 Electron microscopes NIHON DENSHI KK 19 April 1971 [18 April 1970] 27312/71 Heading H1D In a scanning electron microscope the specimen is located in a strong magnetic field, of which the portion in front of the specimen serves to focus secondary electrons emitted from the specimen. In Fig. 1 the specimen 6 is located within the lens 7, and secondary electrons return back along the axis and are attracted to the detector 8 by its positive potential. The beam is scanned by the coils 5, and the output signal is displayed on a cathode-ray tube 12 scanned synchronously. Transmitted electrons are collected by a detector 9 which provides an alternative display signal. The energization of the lens 7 may be varied in order to vary the size of the area on the specimen which is scanned by the beam (Fig. 2, not shown). In a modification (Fig. 3, not shown), the specimen is located within the centre polepiece of three polepieces energized by the lens coil. Secondary electrons focused the centre and upper polepieces are deflected into the detector by a further magnetic field (Fig. 3) or by an electric field (Fig. 5, not shown). The centre and lower polepieces focus a transmission image for display on a fluorescent screen when the scanning system is disabled and the lenses modified to direct a parallel beam of electrons on the specimen. In a modification, Fig. 6 (not shown), the field between the centre and upper polepieces is produced by a separate permanent magnet or a separate energizing coil. In another arrangement, Fig. 10 (not shown), the deflecting means is attached to the upper pole of the objective lens, and a specimen holder is mounted on balls on the objective lens.