GB1358063A - Scanning electron microscope - Google Patents

Abstract

1358063 Scanning electron microscope NIHON DENSHI KK 31 Aug 1971 [11 Sept 1970] 40666/71 Heading H4F [Also in Division H1] A scanning electron microscope includes focusing electron lens 4, deflector 5V, 5H stigmator 21 for correcting astigmatism of the lens 4, means for changing the focal length of lens 4 between two values automatically and periodically, and display means such as cots 13, 14 for displaying the two scanned images. The stigmator is adjusted until the images (e.g. Figs. 4a, 4c, not shown) are the same (e.g. Figs. 5a, 5c, not shown). Generator 6H supplies sawtooth current to coil 5H (Fig. 2a, not shown) in synchronism with pulse generator output (Fig. 2b) to power source 8 producing positive or negative D.C. pulses (Fig. 2c) to auxiliary coil 9 to effect focal length charges. Specimen 10 produces signals (X rays, secondary electrons, reflected or transmission electrons) to detector 11, amplifier 12 and at grids 13c, 14c. Part of the signals from scanning signal generators 6V, 6H is supplied to deflecting coils 13V, 13H, 14V, 14H to effect a brightness modulation scanning image. Blanking signal generator 15 supplies signals (Figs. 2d, 2e) to grids 13b, 14b to effect alternate display of the two images. The auxiliary coil 9 may be replaced by a bias circuit 24 (Fig. 6, not shown) to effect small changes in output from generator 23 to lens 4. Fig. 7 (not shown) omits grid 13b, 14b, cut off being effected by circuit (25), while in Fig. 8 (not shown), biasing circuit (26) superposes two different voltages on signal to coil 13H so that the two images are displayed on the left and right hand sides of the C.R.T. face respectively. In Fig. 9 (not shown) switching signal generator 7 is synchronized with vertical scanning from generator 6V so that the scanning images corresponding to two focal distances are displayed in alternate frames.