Radiant energy – With charged particle beam deflection or focussing – Magnetic lens
Patent
1981-09-03
1983-07-12
Smith, Alfred E.
Radiant energy
With charged particle beam deflection or focussing
Magnetic lens
250396ML, 250310, 250311, G21K 108, G21K 510, H01J 314
Patent
active
043933092
ABSTRACT:
The relation between the focusing distance (D) of the objective lens and the excitation current (I) of the objective lens is stored in a data memory. The initial focusing distance (D.sub.o) corresponding to the optimum excitation current is determined as a result of the focusing adjustment operation. Thereafter, the change (.DELTA.D) in the focusing distance due to the specimen shift along the optical axis of the objective lens is detected. The magnitude of the excitation current corresponding to the focusing distance (D.sub.o +.alpha.D) is read from said memory and a current of that magnitude is supplied to the objective lens.
REFERENCES:
patent: 3715582 (1973-02-01), Akahori et al.
patent: 3842236 (1974-10-01), Von Walter
Berman Jack I.
Jeol Ltd.
Smith Alfred E.
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