US3614520A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electron beam injector and focusing means suitable for electron microscope
Assignee: Forgflo Corp
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Filing: 1968-09-12
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Granted: 1971-10-19
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Expires: 1988-09-12
Abstract
Abstract An electron beam focusing means including a grid cap and accelerating lenses is provided. To permit a small change of voltage on the grid cap to overcome the defocusing effect of a great change in voltage on the accelerating electrodes, a short focal length accelerating lens is positioned in the front focal length of the long focal length lens constituted by the high voltage accelerating electrodes.
Inventors
- 👤 John W Coleman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:21
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/02; H01J37/04; H01J37/06; H01J37/07; H01J3/00; H01J3/02; H01J3/029; H01J37/063
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
166 words
An electron gun of particular utility in the environment of an electron microscope comprising, in combination, means to produce an electron beam; a first accelerating lens of a relatively short focal length so positioned that the beam passes therethrough, and at a positive potential relative to said means to produce an electron beam; a second accelerating lens of a relatively long focal length compared with the focal length of said first lens and so positioned that the beam passes through the second lens after it passes through the first lens, said second lens being at a potential significantly more positive than said first lens, said second lens being spaced from said first lens by a distance less than the focal length of the second lens, whereby defocusing of said beam as a result of a significant change in the potential applied to said second lens is readily corrected by a relatively small change in the potential difference between said beam producing means and said first lens.
Claim 2
Dependent Claim
166 words
An electron gun of particular utility in the environment of an electron microscope comprising, in combination, means to produce an electron beam; a first accelerating lens of a relatively short focal length so positioned that the beam passes therethrough, and at a positive potential relative to said means to produce an electron beam; a second accelerating lens of a relatively long focal length compared with the focal length of said first lens and so positioned that the beam passes through the second lens after it passes through the first lens, said second lens being at a potential significantly more positive than said first lens, said second lens being spaced from said first lens by a distance less than the focal length of the second lens, whereby defocusing of said beam as a result of a significant change in the potential applied to said second lens is readily corrected by a relatively small change in the potential difference between said beam producing means and said first lens.
Claim 3
Dependent Claim
36 words
An electron gun according to claim 1 wherein said first accelerating lens comprises a plurality of electrodes spaced from each other and each at a potential significantly lower than the potential of said second accelerating lens.
Claim 4
Dependent Claim
82 words
An electron gun according to claim 2 wherein said means to produce an electron beam includes a cathode; and a grid cap in proximity to said cathode and having an opening therethrough for passage of electrons from said cathode; said grid cap being at a potential negative with respect to the potential of said first lens, and said grid cap potential being adjustable to provide said relatively small change in the potential difference between said beam producing means and said first lens.
Claim 5
Dependent Claim
32 words
An electron gun according to claim 1 which further includes means to deflect said electron beam, said means to deflect being positioned between said first accelerating lens and said second accelerating lens.
Claim 6
Dependent Claim
56 words
An electron gun according to claim 4 wherein said means to produce an electron beam includes a cathode; and a grid cap in proximity to said cathode and having an opening therethrough for passage of electrons from said cathode; and an ion trap between said means to produce the electron beam and said first accelerating lens.
Claim 7
Dependent Claim
32 words
An electron gun according to claim 5 which further includes additional lens means extending around said ion trap and between said means to produce the electron beam and said first accelerating lens.
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) | 1974-10-18 | 1975-04-19 | 1975-10-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-10-18 | 1979-04-19 | 1979-10-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-10-18 | 1983-04-19 | 1983-10-19 | $7700.00 | Window Closed / Lapsed |