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US3636248A
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US
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Acoustical holography by optically sampling a sound field in bulk
Assignee: Zenith Electronics LLC
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Filing: 1970-03-05
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Granted: 1972-01-18
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Expires: 1990-03-05
Abstract
Abstract A coherent monochromatic light beam is directed into a lightsound interaction cell in which a spatially modulated sound field of constant frequency-carrying image information is propagated nominally transversely to the beam by means of a transducer attached to the sound cell and driven by an appropriate constant frequency signal. The beam is focused about any desired point in the sound field so that a scattering interaction is obtained. The focal region is maintained narrower than the sound wavelength so that a temporal and spatial modulation is imparted to the light representative of the phase and amplitude of the sound field at the focal region. Interposed in the path of such modulated light is a photodetector preceded by a demodulator comprised of either a spatial filter or quarter-waveplate and analyzer. The photodetector extracts an output signal at the sound frequency whose phase and amplitude is representative of that of the sound field about the desired focal region. Such a signal may be recorded or displayed either conventionally, or holographically, if the output signal is mixed with a reference signal derived from the constant frequency transducer signal.
Inventors
- 👤 Adrianus Korpel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 16:00
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/11; Y; Y10; Y10S; Y10S359/00; Y10S359/901
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
227 words
A system for producing a signal varying in accordance with the acoustic amplitude and phase exhibited in a small localized region about any chosen point within a sound field of waves propagated at a constant acoustic frequency, comprising: a light sound interaction cell which includes a sound-conducting medium and which operates at a constant acoustic frequency to propagate sound waves throughout said medium establishing said sound field; means for projecting into said sound field a coherent monochromatic light beam incident in a direction generally transverse to that of the sound propagation; means for focusing said incident light beam into a small localized region about any desired point within said sound field, said focal region having a width in the direction of sound propagation at said point which is narrower than half the wavelength of the sound waves, said sound waves imparting temporal and spatial modulation in a scattering interaction in accordance with the phase and amplitude of said sound at said focal region to the light emerging from the sound field; and means including a photodetector receiving said emergent light for detecting the beat frequency between the scattered and nonscattered emergent light and for producing a signal in accordance with said beat frequency, said signal being simply related to said acoustic frequency and being modulated in accordance with the amplitude and phase in said small focal region.
Claim 2
Independent Claim
227 words
A system for producing a signal varying in accordance with the acoustic amplitude and phase exhibited in a small localized region about any chosen point within a sound field of waves propagated at a constant acoustic frequency, comprising: a light sound interaction cell which includes a sound-conducting medium and which operates at a constant acoustic frequency to propagate sound waves throughout said medium establishing said sound field; means for projecting into said sound field a coherent monochromatic light beam incident in a direction generally transverse to that of the sound propagation; means for focusing said incident light beam into a small localized region about any desired point within said sound field, said focal region having a width in the direction of sound propagation at said point which is narrower than half the wavelength of the sound waves, said sound waves imparting temporal and spatial modulation in a scattering interaction in accordance with the phase and amplitude of said sound at said focal region to the light emerging from the sound field; and means including a photodetector receiving said emergent light for detecting the beat frequency between the scattered and nonscattered emergent light and for producing a signal in accordance with said beat frequency, said signal being simply related to said acoustic frequency and being modulated in accordance with the amplitude and phase in said small focal region.
Claim 3
Independent Claim
271 words
A system for the display of image information borne by an acoustic field, comprising: a light-sound interaction cell which includes a sound-conducting medium, and which operates at a constant acoustic frequency to propagate sound waves throughout said medium, establishing a sound field; means for spatially modulating said sound field with image information; means for projecting into said sound field a coherent monochromatic light beam incident in a direction generally transverse to that of the sound propagation; means for focusing said incident light beam into a small localized region about any desired point within said sound field, said focal region having a width in the direction of sound propagation at said point which is narrower than half the wavelength of the sound waves, said sound waves imparting temporal and spatial modulation in a scattering interaction in accordance with the phase and amplitude of said sound at said focal region to the light emerging from the sound field; means including a photodetector receiving said emergent light for detecting the beat frequency between the scattered and nonscattered emergent light and for producing a signal in accordance with said beat frequency, said signal being simply related to said acoustic frequency and being modulated in accordance with the amplitude and phase in said small focal region; means for scanning an arbitrary cross section of said sound field with said focused region in a definite pattern and rate; and television display means for displaying said modulated signal and having a video scan synchronized in accordance with said means for scanning the sound field, said signal modulating said video scan to produce an image of said cross section.
Claim 4
Independent Claim
271 words
A system for the display of image information borne by an acoustic field, comprising: a light-sound interaction cell which includes a sound-conducting medium, and which operates at a constant acoustic frequency to propagate sound waves throughout said medium, establishing a sound field; means for spatially modulating said sound field with image information; means for projecting into said sound field a coherent monochromatic light beam incident in a direction generally transverse to that of the sound propagation; means for focusing said incident light beam into a small localized region about any desired point within said sound field, said focal region having a width in the direction of sound propagation at said point which is narrower than half the wavelength of the sound waves, said sound waves imparting temporal and spatial modulation in a scattering interaction in accordance with the phase and amplitude of said sound at said focal region to the light emerging from the sound field; means including a photodetector receiving said emergent light for detecting the beat frequency between the scattered and nonscattered emergent light and for producing a signal in accordance with said beat frequency, said signal being simply related to said acoustic frequency and being modulated in accordance with the amplitude and phase in said small focal region; means for scanning an arbitrary cross section of said sound field with said focused region in a definite pattern and rate; and television display means for displaying said modulated signal and having a video scan synchronized in accordance with said means for scanning the sound field, said signal modulating said video scan to produce an image of said cross section.
Claim 5
Dependent Claim
69 words
A system as in claim 2 wherein said system further includes: a source of said constant acoustic frequency signal supplying said operating acoustic frequency to said sound cell; means for mixing a part of said acoustic frequency signal with said modulated photodetector signal; and wherein said video scan of said television means is modulated with said mixed signal to produce a holographic image of said sound field cross section.
Claim 6
Dependent Claim
37 words
A system as in claim 3 wherein said sound cell fUrther includes a receptacle for receiving an object within said sound field for examination, and wherein said means for spatially modulating said sound field comprises said object.
Claim 7
Dependent Claim
186 words
A system as in claim 1 which further includes means interposed in the path of said incident light beam for polarizing the light of said beam in a direction generally 45* to that of the propagation of the sound, and in which said sound-conducting medium is one which exhibits dynamic birefringence under the influence of said sound field to impart a further polarization to said emergent light such that at least part of said scattered component is rendered orthogonally polarized to the nonscattered incident-light component, and which further includes a quarter-waveplate disposed in the path of said emergent light having two principal axes of transmission, one of which is aligned in the direction of polarization of the nonscattered component and the other of which is aligned in the direction of polarization of the scattered component to transmit both components while introducing a 90* phase shift between said components, and an analyzer with its axis of transmission positioned in a direction generally 45* to that of each of said components to transmit their common component to said photodetector to detect said beat frequency and produce said signal.
Claim 8
Dependent Claim
55 words
A system as in claim 1 in which said means for detecting the beat frequency comprises: a spatial filter placed between said photodetector and said sound cell and extending in the direction of sound propagation transversely to the direction of light propagation, whose transmissivity varies with the position in the direction of the sound propagation.
Claim 9
Dependent Claim
15 words
A system as in claim 6 wherein said spatial filter comprises a neutral density filter.
Claim 10
Dependent Claim
24 words
A system as in claim 6 wherein said spatial filter comprises a variable height aperture, whose height varies in the direction of sound propagation.
Claim 11
Dependent Claim
25 words
A system as in claim 6 wherein said spatial filter comprises a knife edge in the path of said emergent light partially obstructing said light.
Claim 12
Dependent Claim
28 words
A system as in claim 6 wherein said means for detecting the beat frequency further includes a lens system placed between said sound cell and said spatial filter.
Claim 13
Dependent Claim
34 words
A system as in claim 10 wherein said lens system images said focal region approximately upon said spatial filter, such that said spatial filter lies within the depth of focus of said lens system.
Claim 14
Dependent Claim
31 words
A system as in claim 10 wherein said lens system images said focal spot at infinity, and said spatial filter is placed in the back focal plane of said lens system.
References Cited (Backward Citations)
US3488438A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-17 | 1975-07-19 | 1976-01-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-17 | 1979-07-19 | 1980-01-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-17 | 1983-07-19 | 1984-01-18 | $7700.00 | Window Closed / Lapsed |