US3900734A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Scanning electron-beam instrument
Assignee: Cambridge Instruments Ltd
•
Filing: 1974-04-18
•
Granted: 1975-08-19
•
Expires: 1994-04-18
Abstract
Abstract In a scanning electron beam instrument such as a scanning electron microscope, including a variable-focus final lens following the scanning coils and consequently causing rotation of the scanning raster, electronic circuitry is incorporated between time base generators that generate the line and frame scanning signals and the scanning coils themselves, this circuitry mixing the signals according to known principles but being coupled to means controlling the final lens excitation so that the raster orientation at the specimen surface is independent of working distance and furthermore the circuitry includes attenuating means (or amplifying means) in at least one of the scanning signal channels such as to allow correction of distortion of the image introduced by tilting the specimen surface, this correction being consequently unaffected by changes in working distance.
Inventors
- 👤 David Kynaston
- 👤 Peter Irving Tillett
- 👤 Richard Stephen Paden
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 23:26
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/26; H01J37/28
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
243 words
A scanning electron beam instrument comprising means for forming a fine probe of electrons along an axis, a variable-focus electromagnetic final lens acting on said probe, line and frame time base generators capable of generating line and frame scanning signals, line and frame scanning coils disposed to act on said probe ahead of said final lens whereby to cause the formation of a raster on a specimen placed at the focus of said final lens, variable control means controlling the focal length of said final lens, signal mixing means connected to said frame and time base generators and operative to mix said signals and feed derived line and frame scanning signals to said line and frame scanning coils respectively, said derived signals being such as to rotate said raster about said axis as compared with a raster produced by said first-mentioned signals, an interconnection between said signal-mixing means and said variable control means such as to vary the rotation of said raster by said signal-mixing means in opposition to rotation of said raster introduced by said final lens, whereby the orientation of said raster at the focus is independent of the focal length of said final lens at least over a range of focal lengths, and relative attenuating means interposed between at least one of said time base generators and said signal mixing means, capable of varying the dimension of said raster at the focus in a given direction transverse to said axis.
Claim 2
Dependent Claim
243 words
A scanning electron beam instrument comprising means for forming a fine probe of electrons along an axis, a variable-focus electromagnetic final lens acting on said probe, line and frame time base generators capable of generating line and frame scanning signals, line and frame scanning coils disposed to act on said probe ahead of said final lens whereby to cause the formation of a raster on a specimen placed at the focus of said final lens, variable control means controlling the focal length of said final lens, signal mixing means connected to said frame and time base generators and operative to mix said signals and feed derived line and frame scanning signals to said line and frame scanning coils respectively, said derived signals being such as to rotate said raster about said axis as compared with a raster produced by said first-mentioned signals, an interconnection between said signal-mixing means and said variable control means such as to vary the rotation of said raster by said signal-mixing means in opposition to rotation of said raster introduced by said final lens, whereby the orientation of said raster at the focus is independent of the focal length of said final lens at least over a range of focal lengths, and relative attenuating means interposed between at least one of said time base generators and said signal mixing means, capable of varying the dimension of said raster at the focus in a given direction transverse to said axis.
Claim 3
Dependent Claim
51 words
The instrument set forth in claim 1 including second signal-mixing means interposed between said time base generators and said first-mentioned signal-mixing means ahead of said relative attenuating means, said second signal-mixing means being manually controllable to vary the orientation of said raster independently of the focal length of said final lens.
References Cited (Backward Citations)
US3753034A
Cited
US3746855A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-18 | 1979-02-17 | 1979-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-18 | 1983-02-17 | 1983-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-18 | 1987-02-17 | 1987-08-19 | $7700.00 | Window Closed / Lapsed |