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US4384208A
Expired / Lapsed
US
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Electron lens equipped with three magnetic pole pieces
Assignee: Jeol Ltd
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Filing: 1980-12-23
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Granted: 1983-05-17
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Expires: 2000-12-23
Abstract
Abstract An electron lens equipped with three magnetic pole pieces defining two gaps forms two magnetic fields. The magnetic fields are generated in said gaps by opposite and same strength excitation. The bore diameters of the middle and lower magnetic pole pieces are equal and the bore diameter of the upper magnetic pole piece is 1.5 to 5 times larger than those of the middle and lower magnetic pole pieces, so that radial (isotropic) distortion is eliminated and spiral (anisotropic) distortion is extremely reduced.
Inventors
- 👤 Katsushige Tsuno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:30
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/02; H01J37/04; H01J37/10; H01J37/14; H01J37/141
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
81 words
An electron lens consisting of upper, middle and lower magnetic pole pieces installed inside a yoke enveloping two excitation coils so that magnetic fields are generated with opposite and same strength excitation in the two gaps respectively between said three magnetic pole pieces, said middle and lower pole pieces have bores of substantially equal diameter and the bore diameter of said upper pole piece being 1.5 to 5 times larger than the bore diameters of the middle and lower pole pieces.
Claim 2
Dependent Claim
81 words
An electron lens consisting of upper, middle and lower magnetic pole pieces installed inside a yoke enveloping two excitation coils so that magnetic fields are generated with opposite and same strength excitation in the two gaps respectively between said three magnetic pole pieces, said middle and lower pole pieces have bores of substantially equal diameter and the bore diameter of said upper pole piece being 1.5 to 5 times larger than the bore diameters of the middle and lower pole pieces.
Claim 3
Dependent Claim
31 words
An electron lens of claim 1, wherein said two excitation coils are connected in series with respect to each other and supplied with the current from the same lens power supply.
Claim 4
Dependent Claim
32 words
The electron lens according to claim 1 wherein the bore diameter of the upper pole piece is approximately three times larger than the bore diameters of the middle and lower pole pieces.
Claim 5
Dependent Claim
27 words
The electron lens according to claims 1, 2, or 3 wherein the thickness of the middle pole piece adjacent the bore is about 1 to 2 mm.
Claim 6
Dependent Claim
29 words
The electron lens according to claims 1, 2, or 3 wherein the axial gaps between the upper and middle and middle and lower pole pieces are substantially the same.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-05-16 | 1986-11-15 | 1987-05-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-05-16 | 1990-11-15 | 1991-05-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-05-16 | 1994-11-15 | 1995-05-17 | $7700.00 | Window Closed / Lapsed |