US4376249A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable axis electron beam projection system
Assignee: International Business Machines Corp
•
Filing: 1980-11-06
•
Granted: 1983-03-08
•
Expires: 2000-11-06
Abstract
Abstract An electron beam projection system having a projection lens arranged so that upon pre-deflection of the electron beam the electron optical axis of the lens shifts to be coincident with the deflected beam. The projection system includes means for producing an electron beam, means for deflecting the beam, a magnetic projection lens having rotational symmetry for focusing the deflected beam and a pair of magnetic compensation yokes positioned within the bore of the projection lens means. The pair of correction yokes 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. Upon application of current to the pair of compensation yokes the electron optical axis of the projection lens shifts to the position of the deflected beam so that the electron beam remains coincident with the shifted electron optical axis and lands perpendicular to a target.
Inventors
- 👤 Hans C. Pfeiffer
- 👤 Guenther O. Langner
- 👤 Maris A. Sturans
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 01:54
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: 16
Claim 1
Independent Claim
151 words
An electron beam projection system having a projection lens arranged so that upon predeflection of the electron beam the electron optical axis of the lens shifts to be coincident with said deflected beam comprising electron beam producing means for producing an electron beam, deflection means for deflecting said beam, magnetic projection lens means having rotational symmetry for focusing said deflected beam; and a pair of magnetic compensation yoke means positioned within the bore of said lens means, said pair of compensation yoke means 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 and cause the electron optical axis of said lens means to shift 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.
Claim 2
Dependent Claim
151 words
An electron beam projection system having a projection lens arranged so that upon predeflection of the electron beam the electron optical axis of the lens shifts to be coincident with said deflected beam comprising electron beam producing means for producing an electron beam, deflection means for deflecting said beam, magnetic projection lens means having rotational symmetry for focusing said deflected beam; and a pair of magnetic compensation yoke means positioned within the bore of said lens means, said pair of compensation yoke means 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 and cause the electron optical axis of said lens means to shift 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.
Claim 3
Dependent Claim
78 words
An electron beam projection system in accordance with claim 1 wherein the first of said pair of magnetic compensation yoke means is located proximate to the first peak of a first derivative of said axial magnetic field strength distribution curve of said lens means and the second of said pair of magnetic compensation yoke means is located proximate to the second peak of a first derivative of said axial magnetic field strength distribution curve of said lens means.
Claim 4
Dependent Claim
32 words
An electron beam projection system in accordance with claim 1 or claim 2 wherein said electron optical axis of said lens means shifts in synchronism with the deflection of said electron beam.
Claim 5
Dependent Claim
31 words
An electron beam projection system in accordance with claim 1 or claim 2 wherein said axial magnetic field strength distribution curve of said lens means corresponds approximately to a Gaussian distribution.
Claim 6
Dependent Claim
49 words
An electron beam projection system in accordance with claim 1 or claim 2 wherein a dynamic correction coil compensates for distortion of astigmatism due to the rotational symmetry caused by the shift of the electron optical axis of said lens means to be coincident with said deflected electron beam.
Claim 7
Dependent Claim
39 words
An electron beam projection system in accordance with claim 1 which further includes dynamic focus correction coils which compensate for second order errors proportional to the second derivative of the axial magnetic field strength distribution of said lens means.
Claim 8
Dependent Claim
34 words
An electron beam projection system in accordance with claim 6 wherein said dynamic focus correction coils are driven by a current proportional to the square of the beam deflection distance from the symmetry axis.
Claim 9
Dependent Claim
130 words
In an electron beam column: a projection lens including pole piece means 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, first magnetic compensation yoke means positioned within the upper portion of the bore of said pole piece means; and second magnetic compensation yoke means positioned within the lower portion of the bore of said pole piece means; said first and second magnetic compensation yoke means in combination having a magnetic field distribution proportional to the first derivative of said axial magnetic field strength distribution of said projection lens which field distribution causes the electron optical axis of said pole piece means to shift upon application of current to said compensation yokes.
Claim 10
Dependent Claim
130 words
In an electron beam column: a projection lens including pole piece means 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, first magnetic compensation yoke means positioned within the upper portion of the bore of said pole piece means; and second magnetic compensation yoke means positioned within the lower portion of the bore of said pole piece means; said first and second magnetic compensation yoke means in combination having a magnetic field distribution proportional to the first derivative of said axial magnetic field strength distribution of said projection lens which field distribution causes the electron optical axis of said pole piece means to shift upon application of current to said compensation yokes.
Claim 11
Dependent Claim
68 words
In the electron beam column of claim 8 wherein said first magnetic compensation yoke means is located proximate to the first peak of a first derivative of said axial magnetic field strength distribution curve of said pole piece means and said second magnetic yoke means is located proximate to a second peak of a first derivative of said magnetic field strength distribution curve of said pole piece means.
Claim 12
Dependent Claim
30 words
In the electron beam column of claims 8 or 9 wherein said electron optical axis of said pole piece means shifts in synchronism with the position of said deflected beam.
Claim 13
Dependent Claim
29 words
In the electron beam column of claims 8 or 9 wherein said axial magnetic field strength distribution curve of said pole piece means corresponds approximately to a Gaussian distribution.
Claim 14
Dependent Claim
39 words
In the electron beam column of claims 8 or 9 including dynamic correction coil means to compensate for distortion of rotational symmetry caused by the shift of the electron optical axis to be coincident with said deflected electron beam.
Claim 15
Dependent Claim
42 words
In the electron beam column of claim 8 further including dynamic focus correction coil means to compensate for second order errors proportional to the second derivative of the axial magnetic field strength distribution on the shifted axis of said pole piece means.
Claim 16
Dependent Claim
32 words
In the electron beam column of claim 13 wherein said dynamic focus correction coils are driven by a current proportional to the square of the beam deflection distance from the shifted axis.
References Cited (Backward Citations)
US2494442A
Cited
US3597609A
Cited
US3715582A
Cited
US3894271A
Cited
US3930181A
Cited
US4000440A
Cited
US3984687A
Cited
US4112305A
Cited
US4122369A
Cited
US4117340A
Cited
US4199688A
Cited
US4199689A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-03-07 | 1986-09-06 | 1987-03-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-03-07 | 1990-09-06 | 1991-03-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-03-07 | 1994-09-06 | 1995-03-08 | $7700.00 | Window Closed / Lapsed |