US3908124A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Phase contrast in high resolution electron microscopy
Assignee: United States Department of Energy
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Filing: 1974-07-01
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Granted: 1975-09-23
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Expires: 1994-07-01
Abstract
Abstract A device is provided for developing a phase contrast signal for a scanning transmission electron microscope. The lens system of the microscope is operated in a condition of defocus so that predictable alternate concentric regions of high and low electron density exist in the cone of illumination. Two phase detectors are placed beneath the object inside the cone of illumination, with the first detector having the form of a zone plate, each of its rings covering alternate regions of either higher or lower electron density. The second detector is so configured that it covers the regions of electron density not covered by the first detector. Each detector measures the number of electrons incident thereon and the signal developed by the first detector is subtracted from the signal developed by the record detector to provide a phase contrast signal.
Inventors
- 👤 Harald H Rose
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 00:48
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/02; H01J37/244; H01J37/26; H01J37/261; H01J37/263; H01J2237/00; H01J2237/244; H01J2237/2446; H01J2237/24465; H01J2237/245; H01J2237/24507
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
252 words
In a scanning transmission electron microscope operating in a condition of defocus such that there are within the cone of illumination regions alternately of the quality of higher electron density and of lower electron density, the alternate density regions being caused by the interference within the cone of illumination of electrons elastically scattered by the specimen with electrons unscattered by the specimen, a device for developing a phase contrast signal, comprising: a first detector positioned within the cone of illumination, and being of such radial configuration with respect to the optical axis that electrons within all alternate regions of the cone of illumination having one of the qualities of density are incident thereon, said first detector being responsive to electrons incident thereon to develop a first output signal representative of the intensity thereof, a second detector positioned within the cone of illumination and being of such configuration that electrons within the cone of illumination not incident upon said first detector are incident upon said second detector, said second detector being responsive to electrons incident thereon to develop a second output signal representative of the intensity thereof, a differencing circuit coupled to said first and second detectors and responsive to said first and second output signals therefrom to subtract said first output signal from said second output signal and to develop a phase contrast signal which is the subtraction of said first output signal from said second output signal, and utilization means coupled to said differencing circuit for utilizing said phase contrast signal.
Claim 2
Dependent Claim
252 words
In a scanning transmission electron microscope operating in a condition of defocus such that there are within the cone of illumination regions alternately of the quality of higher electron density and of lower electron density, the alternate density regions being caused by the interference within the cone of illumination of electrons elastically scattered by the specimen with electrons unscattered by the specimen, a device for developing a phase contrast signal, comprising: a first detector positioned within the cone of illumination, and being of such radial configuration with respect to the optical axis that electrons within all alternate regions of the cone of illumination having one of the qualities of density are incident thereon, said first detector being responsive to electrons incident thereon to develop a first output signal representative of the intensity thereof, a second detector positioned within the cone of illumination and being of such configuration that electrons within the cone of illumination not incident upon said first detector are incident upon said second detector, said second detector being responsive to electrons incident thereon to develop a second output signal representative of the intensity thereof, a differencing circuit coupled to said first and second detectors and responsive to said first and second output signals therefrom to subtract said first output signal from said second output signal and to develop a phase contrast signal which is the subtraction of said first output signal from said second output signal, and utilization means coupled to said differencing circuit for utilizing said phase contrast signal.
Claim 3
Dependent Claim
38 words
The device of claim 1 wherein said regions within the cone of illumination of alternate electron density are concentric with the cone of illumination, and wherein said first and second detectors are concentric with said cone of illumination.
Claim 4
Dependent Claim
45 words
The device of claim 2 wherein the defocus length Delta f of the microscope is within 8 d2/ lambda of Delta f -C1 where d is the limit of resolUtion, lambda is the electron wavelength and C1 is the first order coefficient of spherical aberration.
Claim 5
Dependent Claim
9 words
The device of claim 3 wherein Delta f -C1.
Claim 6
Dependent Claim
69 words
The device of claim 4 wherein the microscope has a Seidel order of n 3 and an angle of illumination of 1.71( lambda /C3)1/4 radians, and wherein electrons transmitted through the specimen and thereby directed between approximately 0.92( lambda /C3)1/4 radians and approximately 1.44( lambda /C3)1/4 radians with respect to the optical axis are incident upon said first detector where C3 is the third order coefficient of spherical aberration.
Claim 7
Dependent Claim
68 words
The device of claim 4 wherein the microscope has a Seidel order of n 5 and an angle of illumination of 1.87( lambda /C5)1/6 and wherein electrons transmitted through the specimen and thereby directed between approximately 1.23( lambda /C5)1/6 radians and approximately 1.77( lambda /C5)1/6 radians with respect to the optical axis are incident upon said first detector where C5 is the fifth order coefficient of spherical aberration.
Claim 8
Dependent Claim
40 words
The device of claim 2 wherein said first detector includes a zone plate having at least one ring and wherein said second detector includes a disc so positioned that said first detector is between said specimen and said second detector.
Claim 9
Dependent Claim
32 words
The device of claim 2 wherein said first detector includes a zone plate having at least one ring and wherein said second detector includes a zone plate having at least one ring.
References Cited (Backward Citations)
US3626184A
Cited
US3857034A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-22 | 1979-03-24 | 1979-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-22 | 1983-03-24 | 1983-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-22 | 1987-03-24 | 1987-09-23 | $7700.00 | Window Closed / Lapsed |