Patent EP0051733A1 successfully refreshed from Google Patents.
EP0051733A1
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EP
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Electron beam projection system
Assignee: International Business Machines Corp
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Filing: 1981-09-23
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Granted: —
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Expires: 2001-09-23
Abstract
Abstract The electron beam projection system includes means for producing an electron beam, means (43, 45) for deflecting the beam (39), a magnetic projection lens (33) having rotational symmetry for focusing the deflected beam and a pair of magnetic compensation yokes (55, 57) positioned within the bore of the projection lens means (33). The pair of compensation yokes (55, 57) has coil dimensions such that, in combination, they produce a magnetic compensation field proportional to the first derivative of the axial magnetic field strength distribution curve of the projection lens (33). Upon application of current to the pair of compensation yokes (55, 57) the electron optical axis of the projection lens (33) shifts to the position of the deflected beam so that the electron beam (39) remains coincident with the shifted electron optical axis and lands perpendicular to a target (59).
Inventors
- 👤 Guenther Otto Langner
- 👤 Hans Christian Pfeiffer
- 👤 Maris Andris Sturans
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 13:10
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/30; H01J37/3002; H01J37/3007; H01J37/02; H01J37/04; H01J37/147; H01J37/1472; H01J37/1474
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
171 words
An electron beam projection system having a projection lens (33) arranged so that upon predeflection of the electron beam (39) the electron optical axis of the lens (33) shifts to be coincident with said deflected beam comprising electron beam producing means for producing an electron beam (39), deflection means (43, 45) for deflecting said beam (39), and magnetic projection lens means (33) having rotational symmetry for focusing said deflected beam, characterized in that a pair of magnetic compensation yoke means (55, 57) positioned within the bore of said lens means (33, 47), said pair of compensation yoke means (55, 57) having coil dimensions such that, in combination, they produce a magnetic compensation field proportional to the first derivative of the axial magnetic field strength distribution curve of said lens means (33, 47) whereby the electron optical axis of said lens means (33, 47) shifts to the position of said deflected beam, so that said electron beam remains coincident with said shifted electron optical axis and lands perpendicular to a target (59).
Claim 2
Dependent Claim
171 words
An electron beam projection system having a projection lens (33) arranged so that upon predeflection of the electron beam (39) the electron optical axis of the lens (33) shifts to be coincident with said deflected beam comprising electron beam producing means for producing an electron beam (39), deflection means (43, 45) for deflecting said beam (39), and magnetic projection lens means (33) having rotational symmetry for focusing said deflected beam, characterized in that a pair of magnetic compensation yoke means (55, 57) positioned within the bore of said lens means (33, 47), said pair of compensation yoke means (55, 57) having coil dimensions such that, in combination, they produce a magnetic compensation field proportional to the first derivative of the axial magnetic field strength distribution curve of said lens means (33, 47) whereby the electron optical axis of said lens means (33, 47) shifts to the position of said deflected beam, so that said electron beam remains coincident with said shifted electron optical axis and lands perpendicular to a target (59).
Claim 3
Dependent Claim
88 words
An electron beam projection system in accordance with claim 1, characterized in that the first of said pair of magnetic compensation yoke means (55, 57) is located proximate to the first peak of a first derivative of said axial magnetic field strength distribution curve of said lens means (33, 47) and the second of said pair of magnetic compensation yoke means (55, 57) is located proximate to the second peak of a first derivative of said axial magnetic field strength distribution curve of said lens means (33, 47).
Claim 4
Dependent Claim
36 words
An electron beam projection system in accordance with claim 1 and/or 2, characterized in that said electron optical axis of said lens means (33, 47) shifts in synchronism with the deflection of said electron beam (39).
Claim 5
Dependent Claim
39 words
An electron beam projection system in accordance with at least one of the claims 1 to 3, characterized in that said axial magnetic field strength distribution curve of said lens means (33, 47) corresponds approximately to a Gaussian distribution.
Claim 6
Dependent Claim
62 words
An electron beam projection system in accordance with at least one of the claims 1 to 4, characterized in that a dynamic correction coil (69) is provided to compensate for distortion of astigmatism due to the rotational symmetry caused by the shift of the electron optical axis of said lens means (33, 47) to be coincident with said deflected electron beam (39).
Claim 7
Dependent Claim
55 words
An electron beam projection system in accordance with at least one of the claims 1 to 5, characterized in that further dynamic focus correction coils (71, 73, 75, 77) are included to compensate for second order errors proportional to the second derivative of the axial magnetic field strength distribution of said lens means (33, 47).
Claim 8
Dependent Claim
40 words
An electron beam projection system in accordance with claim 6, characterized in that said dynamic focus correction coils (71, 73, 75, 77) are driven by a current proportional to the square of the beam deflection distance from the symmetry axis.
Claim 9
Dependent Claim
167 words
An electron beam projection system including deflection yokes where said lens means (33, 47) has a projection lens (33)_ including pole piece means (35, 37) to produce magnetic field lines of rotational symmetry defining a geometrical electron optical axis, said field lines having a magnetic field strength distribution curve along said axis, in accordance with claims 1 to 7, characterized in that the first magnetic compensation yoke means (55) is positioned within the upper portion (35) of the bore of said pole piece means (35, 37); and second magnetic compensation yoke means (57) is positioned within the lower portion (37) of the bore of said pole piece means (35, 37); said first and second magnetic compensation yokes (55, 57) in combination have a magnetic field distribution proportional to the first derivative of said axial magnetic field strength distribution of said projection lens (33), whereby the electron optical axis of said pole piece means (35, 37) is shifted upon application of current to said compensation yokes (55, 57).
References Cited (Backward Citations)
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