Patent US4085859A successfully refreshed from Google Patents.
Patent EP0025491A2 successfully refreshed from Google Patents.
EP0025491A2
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EP
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A method and apparatus for detecting one or more spectral features in a sample
Assignee: International Business Machines Corp
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Filing: 1980-07-24
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Granted: —
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Expires: 2000-07-24
Abstract
Abstract This invention is directed to a method and apparatus for detecting one or more spectral features in a sample (16). The method for detecting a single narrow spectral feature in a sample includes the steps of providing a beam of light (10) having an optical frequency bandwidth which is narrow compared to the width of the narrow spectral feature and having a centre frequency ωc which lies near the narrow spectral feature, phase modulating (12) the beam of light with a single RF frequency to provide a pure FM spectrum having upper and lower sidebands, exposing the sample (16) containing the narrow spectral feature to the modulated light so that only one of the FM sidebands probes the narrow spectral feature, photodetecting (18) the light emerging from the sample to detect a RF beat at the specific RF frequency used for phase modulation, and electronically monitoring (20) the amplitude of the RF beat signal to indicate the strength of the narrow spectral feature. A preferred embodiment of the invention is an apparatus for multiplex readout of information encoded by the presence or absence of photochemical holes burned in an inhomogeneous absorption band of a sample (16). The apparatus includes means (10, 12, 14) for using a frequency modulated laser light with widely spaced sidebands arranged so that only one of each pair of upper and lower sidebands probes the frequency location of each hole. The apparatus uses many simultaneous RF frequencies to drive the phase modulator (12) and produce the light with FM sidebands which simultaneously probes all the hole locations of interest. The apparatus includes photodetection means (18) to receive the light after it has passed through the samples and phase sensitive multiplex analyzing means (20) to process the electrical signals from the photodetection means to indicate the presence or absence of holes.
Inventors
- 👤 Gary Carl Bjorklund
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 08:53
CPC Classifications
G; G01; G01J; G01J3/00; G01J3/28; G01J3/42; G01J3/433; G01J3/4338
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
144 words
A method for detecting a single narrow spectral feature in a sample (16) characterised in that the method comprises providing a beam of light (10) having an optical frequency bandwidth which is narrow compared to the width of the narrow spectral feature and having a centre frequency w C which lies near the feature, phase modulating (12) the beam of light with a single RF frequency to provide a pure FM spectrum having upper and lower sidebands, exposing the sample (16) containing the narrow spectral feature to the modulated light so that only one of the FM sidebands probes the narrow spectral feature, photodetecting (18) the light emerging from the sample to detect a beat at the specific RF frequency used for phase modulation, and electronically monitoring (20) the amplitude of the RF beat signal to indicate the strength of the narrow spectral feature.
Claim 2
Independent Claim
144 words
A method for detecting a single narrow spectral feature in a sample (16) characterised in that the method comprises providing a beam of light (10) having an optical frequency bandwidth which is narrow compared to the width of the narrow spectral feature and having a centre frequency w C which lies near the feature, phase modulating (12) the beam of light with a single RF frequency to provide a pure FM spectrum having upper and lower sidebands, exposing the sample (16) containing the narrow spectral feature to the modulated light so that only one of the FM sidebands probes the narrow spectral feature, photodetecting (18) the light emerging from the sample to detect a beat at the specific RF frequency used for phase modulation, and electronically monitoring (20) the amplitude of the RF beat signal to indicate the strength of the narrow spectral feature.
Claim 3
Dependent Claim
16 words
A method as claimed in claim 1, including monitoring the phase of the RF beat signal.
Claim 4
Dependent Claim
25 words
A method as claimed in claim 1, in which the phase modulating RF frequency is swept to provide a spectrum of the narrow spectral feature.
Claim 5
Independent Claim
169 words
A method for detecting and recovering information contained in a broad spectral feature in a sample (16) whose absorption and index of refraction vary with time and optical frequency characterised in that the method comprises providing a beam of light (10) having an optical frequency bandwidth which is narrow compared to the desired resolution of the information in the broad spectral feature, phase modulating (12) the beam with a plurality of RF frequencies to provide a plurality of FM spectra having upper and lower sidebands which are widely spaced compared to the bandwidth of the original beam of light, exposing the sample (16) containing the broad spectral feature to the modulated light so that one of each pair of FM sidebands probes the broad spectral feature at a different optical frequency location, photodetecting (18) the light emerging from the sample to simultaneously detect beats at the specific RF frequencies used for phase modulation, and electronically monitoring (20) the amplitude of each RF beat signal as a function of time.
Claim 6
Independent Claim
169 words
A method for detecting and recovering information contained in a broad spectral feature in a sample (16) whose absorption and index of refraction vary with time and optical frequency characterised in that the method comprises providing a beam of light (10) having an optical frequency bandwidth which is narrow compared to the desired resolution of the information in the broad spectral feature, phase modulating (12) the beam with a plurality of RF frequencies to provide a plurality of FM spectra having upper and lower sidebands which are widely spaced compared to the bandwidth of the original beam of light, exposing the sample (16) containing the broad spectral feature to the modulated light so that one of each pair of FM sidebands probes the broad spectral feature at a different optical frequency location, photodetecting (18) the light emerging from the sample to simultaneously detect beats at the specific RF frequencies used for phase modulation, and electronically monitoring (20) the amplitude of each RF beat signal as a function of time.
Claim 7
Dependent Claim
16 words
A method as claimed in claim 4, including monitoring the phase of each RF beat signal.
Claim 8
Dependent Claim
36 words
A method as claimed in claim 4, in which the RF frequencies are chosen so that each narrow spectral feature contained in the broad sepectral feature is probed by one of each pair of FM sidebands.
Claim 9
Dependent Claim
31 words
A method as claimed in claim 4, 5 or 6, in which the optical bandwidth of the beam of light is centred at a frequency position within the broad spectral feature.
Claim 10
Dependent Claim
31 words
A method as claimed in claim 4, 5 or 6, in which the optical bandwidth of the beam of light is centred at a frequency position outside the broad spectral feature.
Claim 11
Independent Claim
142 words
An apparatus for detecting a narrow spectral feature in a sample (16) characterised in that the apparatus comprises a laser source (10) having a bandwidth narrower than the width of the narrow spectral feature and having a centre frequency Wc which lies near a selected narrow spectral feature, phase modulator means (12) for modulating the light from said laser source to a pure FM spectrum having upper and lower sidebands, means (14) for driving said modulator means with a single RF frequency to produce an FM sideband which probes the selected narrow spectral feature in the sample, photodetection means (18) to receive the light after it has passed through the sample, and electronic detection means (20) which is capable of monitoring the intensity of the RF electrical signals from said photodetection means to indicate the strength of the selected narrow spectral feature.
Claim 12
Independent Claim
142 words
An apparatus for detecting a narrow spectral feature in a sample (16) characterised in that the apparatus comprises a laser source (10) having a bandwidth narrower than the width of the narrow spectral feature and having a centre frequency Wc which lies near a selected narrow spectral feature, phase modulator means (12) for modulating the light from said laser source to a pure FM spectrum having upper and lower sidebands, means (14) for driving said modulator means with a single RF frequency to produce an FM sideband which probes the selected narrow spectral feature in the sample, photodetection means (18) to receive the light after it has passed through the sample, and electronic detection means (20) which is capable of monitoring the intensity of the RF electrical signals from said photodetection means to indicate the strength of the selected narrow spectral feature.
Claim 13
Dependent Claim
18 words
An apparatus as claimed in claim 9, in which the laser source means is a single frequency laser.
Claim 14
Independent Claim
154 words
An apparatus for multiplex readout of information encoded by the presence or absence of photochemical holes burned in an inhomogeneous absorption band of a sample (16) characterised in that the apparatus comprises, a laser source (10) having a bandwidth narrower than the width of the photochemical holes, phase modulator means (12) for modulating the light from said laser source to provide a plurality of widely spaced pairs of FM sidebands that are arranged so that only one of each pair probes the optical frequency of a hole, means (14) for driving said modulator means simultaneously with a plurality of different RF frequencies to produce light with FM sidebands which simultaneously probe all hole locations of interest, photodetection means (18) to receive the light after it has passed through the sample, and phase sensitive multiplex analyzing means (20) to process the electrical signals from said photodetection means to indicate the presence or absence of holes.
Claim 15
Independent Claim
154 words
An apparatus for multiplex readout of information encoded by the presence or absence of photochemical holes burned in an inhomogeneous absorption band of a sample (16) characterised in that the apparatus comprises, a laser source (10) having a bandwidth narrower than the width of the photochemical holes, phase modulator means (12) for modulating the light from said laser source to provide a plurality of widely spaced pairs of FM sidebands that are arranged so that only one of each pair probes the optical frequency of a hole, means (14) for driving said modulator means simultaneously with a plurality of different RF frequencies to produce light with FM sidebands which simultaneously probe all hole locations of interest, photodetection means (18) to receive the light after it has passed through the sample, and phase sensitive multiplex analyzing means (20) to process the electrical signals from said photodetection means to indicate the presence or absence of holes.
Claim 16
Dependent Claim
28 words
An apparatus as claimed in claim 11, in which the laser source has a bandwidth centre frequency Wc which is at the centre of the inhomogeneous absorption band.
Claim 17
Dependent Claim
24 words
An apparatus as claimed in claim 11 or 12, in which the means for driving said modulator means is an RF frequency comb generator.
Claim 18
Dependent Claim
22 words
An apparatus as claimed in claim 11 or 12, in which the means for driving said modulator means is a pulse generator.
References Cited (Backward Citations)
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