Automatic methods for focus and astigmatism corrections in...

Details Automatic methods for focus and astigmatism corrections in... Automatic methods for focus and astigmatism corrections in...

2006-04-11

2006-04-11

Berman, Jack I. (Department: 2881)

Radiant energy

Inspection of solids or liquids by charged particles

Methods

C250S310000, C250S309000, C250S398000

Reexamination Certificate

active

07026614

ABSTRACT:
Automatic methods for focus and astigmatism corrections in a charged-particle beam instrument find an amount of excitation of the objective lens that provides the position of a circle of least confusion and can perform accurate automatic corrections of focus and astigmatism. The edge components of the original image along the X- and Y-directions are extracted separately, using respective filters. Noise reduction and normalization of numerical values are performed for each of the resulting two sets of data. Two-dimensional matrices of numerical values indicating the edge components in the X- and Y-directions, respectively, are found independently. The sums of the elements of the matrices are taken as focus evaluation values of the original image in the X- and Y-directions, respectively.

REFERENCES:
patent: 4554452 (1985-11-01), Suganuma
patent: 5144129 (1992-09-01), Kobayashi et al.
patent: 5313062 (1994-05-01), Yamada
patent: 6825480 (2004-11-01), Watanabe et al.

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