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US4777443A
Expired / Lapsed
US
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Inspection apparatus based on nuclear magnetic resonance
Assignee: Hitachi Ltd
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Filing: 1987-11-12
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Granted: 1988-10-11
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Expires: 2007-11-12
Abstract
Abstract Disclosed in a nuclear magnetic resonance (NMR) based inspection apparatus using an SQUID flux meter for detecting a small NMR signal, in which a receiving coil for receiving the NMR signal from an object is connected to a mixer, which mixes a reference high-frequency signal with the NMR signal so that the NMR signal is reduced to a low-frequency signal having a differential component of frequencies of both signals, and the low-frequency signal is applied to the input coil of the SQUID flux meter so that it is converted into a voltage signal. The mixer circuit includes Schottky diodes operative at a liquid helium temperature or Josephson junctions, and the portions of apparatus from the reception coil up to the SQUID flux meter are operated in a superconductive state at a liquid helium temperature.
Inventors
- 👤 Masao Yabusaki
- 👤 Etsuji Yamamoto
- 👤 Takashi Onodera
- 👤 Yukiko Ogura
- 👤 Hideaki Nakane
- 👤 Shigeru Matsui
- 👤 Hideki Kohno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 11:27
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/32; G01R33/323; G01R33/326; G01R33/02; G01R33/035; G01R33/0354; G01R33/0358
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
108 words
An inspection apparatus based on nuclear magnetic resonance (NMR) comprising: means for exciting the nuclear spin of an object placed in a prescribed magnetic field; a receiving coil for receiving an NMR signal from said object; a high-frequency signal generator for producing a high-frequency signal with a prescribed frequency; a mixer for mixing said NMR signal with said high-frequency signal to convert said NMR signal into a low-frequency signal having a differential component of frequencies of said signals; and an SQUID flux meter having an input coil for receiving said low-frequency signal and adapted to convert a magnetic flux generated by said input coil into a voltage signal.
Claim 2
Dependent Claim
108 words
An inspection apparatus based on nuclear magnetic resonance (NMR) comprising: means for exciting the nuclear spin of an object placed in a prescribed magnetic field; a receiving coil for receiving an NMR signal from said object; a high-frequency signal generator for producing a high-frequency signal with a prescribed frequency; a mixer for mixing said NMR signal with said high-frequency signal to convert said NMR signal into a low-frequency signal having a differential component of frequencies of said signals; and an SQUID flux meter having an input coil for receiving said low-frequency signal and adapted to convert a magnetic flux generated by said input coil into a voltage signal.
Claim 3
Dependent Claim
25 words
An inspection apparatus according to claim 1 further comprising an A/D converter for converting the output of said SQUID flux meter into a digital signal.
Claim 4
Dependent Claim
27 words
An inspection apparatus according to claim 1, wherein said mixture comprises a double balanced mixer including a Schottky diode which is operative at a liquid helium temperature.
Claim 5
Dependent Claim
34 words
An inspection apparatus according to claim 1, wherein said mixer comprises a Josephson junction circuit in connection with a d.c. bias current source, said receiving coil, and the output of said high-frequency signal generator.
Claim 6
Dependent Claim
24 words
An inspection apparatus according to claim 4, wherein said Josephson junction circuit comprises a comprises a serial connection of a plurality of Josephson junctions.
Claim 7
Dependent Claim
78 words
An inspection apparatus according to claim 1, wherein said SQUID flux meter comprises an SQUID flux meter of a feedback type including a modulation means for modulating the signal received by said input coil, a loop circuit made up of a plurality of Josephson junctions for detecting a modulated magnetic flux, and a feedback means which demodulates the output signal of said loop circuit and feeds back the demodulated signal as an intersecting flux to said loop circuit.
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) | 1991-10-11 | 1992-04-11 | 1992-10-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-11 | 1996-04-11 | 1996-10-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-11 | 2000-04-11 | 2000-10-11 | $7700.00 | Window Closed / Lapsed |