US5299035A
Expired / Lapsed
US
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Holographic imaging through scattering media
Assignee: University of Michigan (System)
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Filing: 1992-03-25
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Granted: 1994-03-29
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Expires: 2012-03-25
Abstract
Abstract An image of an object embedded in a diffusing medium is formed by propagating a coherent or equivalent light pulse through the diffusing medium and applying a reference pulse so as to gate precisely the first emerging light transmitted through the diffusing medium. An ultra-short pulse, having a duration on the order of 150 fs, insures that only the first emerging light is used to form a hologram. Instability in the diffusing medium, which may be inherent therein, as is the case with living tissue, or artificially induced therein, such as by vibrating the specimen, ensures that a subsequent hologram has a different background noise and speckle pattern. Integration of such holograms causes the background noise to average out, but time-invariant features, such as the object being imaged, become increasingly more visible as more holograms are integrated.
Inventors
- 👤 Emmett N. Leith
- 👤 David S. Dilworth
- 👤 Hsuan S. Chen
- 👤 Ye Chen
- 👤 Joaquin L. Lopez
- 👤 Janis A. Valdmanis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 05:21
CPC Classifications
G; G03; G03H; G03H1/00; G03H1/04; G03H1/0402; G03H1/041; G03H2222/00; G03H2222/33; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
338 words
A method of imaging an object, the method comprising the steps of: propagating a first light pulse through an unstable diffusing medium in which the object to be imaged is embedded, the instability of said unstable diffusing medium being characterized by a diffusion characteristic which changes at a substantially predeterminable time rate of change; combining a light from said first light pulse which has been propagated through said unstable diffusing medium with a second light pulse, said second light beam pulse having a second pulse duration which is very short with respect to said time rate of change of said diffusion characteristic, whereby said diffusion characteristic changes only insignificantly during said second pulse duration, said second pulse duration and said substantially predeterminable time rate of change of said diffusion characteristic being related to one another such that said second pulse duration is decreased as said substantially predeterminable time rate of change of said diffusion characteristic is increased, said second light pulse being timed to combine with an initial portion of said first light pulse propagated through said unstable diffusing medium to form a holographic interference image; imaging said holographic interference image onto an optical input of a receiving device within a first exposure period having a predetermined duration which is short as compared to the time rate of change of the diffusion characteristic, said first exposure period being selected in response to substantially predeterminable time rate of change of said diffusion characteristic, whereby the diffusion characteristic changes insignificantly during said predetermined exposure period; and repeating said steps of propagating, combining, and imaging during a second exposure period having a predetermined duration which is short as compared to the time rate of change of the diffusion characteristic, said second exposure period commencing after expiration of an interexposure delay period following the expiration of said first exposure period, said interexposure delay period having a duration which is significant as compared to the time rate of change of the diffusion characteristic, whereby said diffusion characteristic changes during said interexposure delay period.
Claim 2
Independent Claim
338 words
A method of imaging an object, the method comprising the steps of: propagating a first light pulse through an unstable diffusing medium in which the object to be imaged is embedded, the instability of said unstable diffusing medium being characterized by a diffusion characteristic which changes at a substantially predeterminable time rate of change; combining a light from said first light pulse which has been propagated through said unstable diffusing medium with a second light pulse, said second light beam pulse having a second pulse duration which is very short with respect to said time rate of change of said diffusion characteristic, whereby said diffusion characteristic changes only insignificantly during said second pulse duration, said second pulse duration and said substantially predeterminable time rate of change of said diffusion characteristic being related to one another such that said second pulse duration is decreased as said substantially predeterminable time rate of change of said diffusion characteristic is increased, said second light pulse being timed to combine with an initial portion of said first light pulse propagated through said unstable diffusing medium to form a holographic interference image; imaging said holographic interference image onto an optical input of a receiving device within a first exposure period having a predetermined duration which is short as compared to the time rate of change of the diffusion characteristic, said first exposure period being selected in response to substantially predeterminable time rate of change of said diffusion characteristic, whereby the diffusion characteristic changes insignificantly during said predetermined exposure period; and repeating said steps of propagating, combining, and imaging during a second exposure period having a predetermined duration which is short as compared to the time rate of change of the diffusion characteristic, said second exposure period commencing after expiration of an interexposure delay period following the expiration of said first exposure period, said interexposure delay period having a duration which is significant as compared to the time rate of change of the diffusion characteristic, whereby said diffusion characteristic changes during said interexposure delay period.
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein said optical input in said step of imaging is a photoelectric device.
Claim 4
Dependent Claim
52 words
The method of claim 1 wherein there are further provided the steps of: reading said holographic interference image onto a digital computer; calculating in said digital computer to produce an image from said holographic interference image; repeating said steps of reading and calculating; and summing said images to form an integrated image.
Claim 5
Dependent Claim
66 words
The method of claim 3 wherein there is further provided the step of integrating electronically a plurality of said holographic interference images obtained during respective exposure periods, whereby the effect of a background noise component in each such holographic interference image is reduced to an extent corresponding to the number of said holographic interference images being integrated, to obtain a composite image having reduced background noise.
Claim 6
Dependent Claim
17 words
The method of claim 1 wherein said unstable diffusing medium is the flesh of a living being.
Claim 7
Dependent Claim
38 words
The method of claim 1 wherein prior to performing said step of propagating there are provided the steps of: forming a source light pulse; and splitting said source light pulse to form said first and second light pulses.
Claim 8
Dependent Claim
31 words
The method of claim 1 wherein prior to performing said step of propagating there is provided the step of inducing instability in a diffusing medium to form said unstable diffusing medium.
Claim 9
Dependent Claim
29 words
The method of claim 7 wherein said step of inducing instability comprises the step of vibrating said diffusing medium, said diffusion characteristic being responsive to said step of vibrating.
Claim 10
Dependent Claim
72 words
The method of claim 1 wherein there are further provided the steps of: converting said holographic interference image onto a corresponding electrical signal; storing data corresponding to said electrical signal in said recording device; subjecting said data to Fourier transformation; filtering said transformed data to retain a portion thereof corresponding to a first-order diffracted beam of said holographic interference image; and reverse transforming said filtered data to form a processed image signal.
Claim 11
Dependent Claim
116 words
The method of claim 1 wherein said step of combining comprises the steps of: first illuminating an imaging diffuser of a beam combiner with said light from said first light pulse which has been propagated through said unstable diffusing medium; first propagating an image formed on said imaging diffuser along a first imaging path toward said optical input of said recording device; second illuminating a reflector of said beam combiner arranged in said imaging path to be substantially parallel to said imaging diffuser with said second light pulse; and second propagating said second light pulse reflected from said reflector of said beam combiner along a second imaging path toward said optical input of said recording device.
Claim 12
Dependent Claim
18 words
The method of claim 10 wherein said first and second imaging paths are not parallel to one another.
Claim 13
Dependent Claim
30 words
The method of claim 1 wherein said step of combining comprises the further step of synchronizing said second light pulse with a first transmitted light of said first light pulse.
Claim 14
Dependent Claim
27 words
The method of claim 12 wherein said step of synchronizing comprises the step of modifying the length of a path of travel of said second light pulse.
Claim 15
Independent Claim
148 words
A system for imaging an object embedded in a diffusing medium, the system comprising: first light source means for propagating a first coherent light pulse through the diffusing medium in which the object to be imaged is embedded; second light source means for producing a second coherent light pulse; combiner means for combining a light from said first coherent light pulse which has been propagated through said diffusing medium with the second coherent light pulse; synchronizing means for adjusting a time of issuance of said second coherent light pulse, whereby said second coherent light pulse is timed to combine with an initial portion of said first coherent light pulse propagated through said diffusing medium to form a holographic interference image; and recording means for receiving said holographic interference image and forming a hologram representative of said initial portion of said first light pulse propagated through said diffusing medium.
Claim 16
Independent Claim
148 words
A system for imaging an object embedded in a diffusing medium, the system comprising: first light source means for propagating a first coherent light pulse through the diffusing medium in which the object to be imaged is embedded; second light source means for producing a second coherent light pulse; combiner means for combining a light from said first coherent light pulse which has been propagated through said diffusing medium with the second coherent light pulse; synchronizing means for adjusting a time of issuance of said second coherent light pulse, whereby said second coherent light pulse is timed to combine with an initial portion of said first coherent light pulse propagated through said diffusing medium to form a holographic interference image; and recording means for receiving said holographic interference image and forming a hologram representative of said initial portion of said first light pulse propagated through said diffusing medium.
Claim 17
Dependent Claim
119 words
The system of claim 14 wherein the diffusing medium is an unstable diffusing medium, the instability of said unstable diffusing medium being characterized by a diffusion characteristic which changes at a substantially predeterminable time rate of change, said second coherent light pulse being characterized by a second pulse duration which is very short as compared to said time rate of change of said diffusion characteristic, said second pulse duration and said substantially predeterminable time rate of change of said diffusion characteristic being related to one another such that said second pulse duration is decreased as said substantially predeterminable time rate of change of said diffusion characteristic is increased, whereby said diffusion characteristic changes insignificantly during said second pulse duration.
Claim 18
Dependent Claim
64 words
The system of claim 15 wherein said recording means receives said holographic interference image within an exposure period having a predetermined duration which is short as compared to the time of change of the diffusion characteristic, said exposure period being selected in response to substantially predeterminable time rate of change of said diffusion characteristic, whereby the diffusion characteristic changes insignificantly during said exposure period.
Claim 19
Dependent Claim
26 words
The system of claim 16 wherein the diffusing medium is living tissue, and said predetermined duration of said exposure period is less than approximately 40 ms.
Claim 20
Dependent Claim
44 words
The system of claim 16 wherein there are provided a plurality of exposure periods sequentially in time, and there is further provided hologram integration means for integrating a plurality of holograms corresponding to holographic interference images obtained during respective ones of said exposure periods.
Claim 21
Dependent Claim
73 words
The system of claim 18 wherein said respective one of said exposure periods are separated in time by respective interexposure delay periods, each such interexposure delay period being selected in response to said time rate of change of the diffusion characteristic, so as to have a duration which is significant as compared to the time rate of change of the diffusion characteristic, whereby said diffusion characteristic changes significantly during said interexposure delay period.
Claim 22
Dependent Claim
16 words
The system of claim 19 wherein said interexposure delay period is longer than approximately 1 ms.
Claim 23
Dependent Claim
58 words
The system of claim 14 wherein said first and second light source means comprise: a laser source for producing a beam of coherent light in the form of a plurality of short pulses of light; and beam splitter means for receiving said beam of coherent light and dividing same to produce said first and second coherent light pulses.
Claim 24
Dependent Claim
32 words
The system of claim 21 wherein said beam splitter means is arranged so that said first coherent light pulse contains a higher amplitude of optical energy than said second coherent light pulse.
Claim 25
Dependent Claim
35 words
The system of claim 21 wherein said short pulses of light from said laser source have a repetition rate wherein a multiplicity of such short pulses of coherent light are produced during an exposure period.
Claim 26
Independent Claim
122 words
A method of imaging an object, the method comprising the steps of: generating a series of short duration pulses of coherent light; dividing the coherent light to produce object and reference beams of said short duration pulses of coherent light; propagating said object beam of said short duration pulses through a diffusing medium in which the object to be imaged is embedded to form a transmitted light in the form of elongated short duration pulses; combining a first transmitted light from each of said elongated pulses which have been propagated through said diffusing medium with said reference beam of said short duration pulses; and imaging said holographic interference image onto an optical input of a recording device within a first exposure period.
Claim 27
Independent Claim
122 words
A method of imaging an object, the method comprising the steps of: generating a series of short duration pulses of coherent light; dividing the coherent light to produce object and reference beams of said short duration pulses of coherent light; propagating said object beam of said short duration pulses through a diffusing medium in which the object to be imaged is embedded to form a transmitted light in the form of elongated short duration pulses; combining a first transmitted light from each of said elongated pulses which have been propagated through said diffusing medium with said reference beam of said short duration pulses; and imaging said holographic interference image onto an optical input of a recording device within a first exposure period.
Claim 28
Dependent Claim
103 words
The method of claim 24 wherein said diffusing medium is characterized by a diffusion characteristic which changes at a substantially predeterminable time rate of change, and said first exposure period has a predetermined duration which is short as compared to the time rate of change of the diffusion characteristic, said second pulse duration and said substantially predeterminable time rate of change of said diffusion characteristic being related to one another such that said second pulse duration is decreased as said substantially predeterminable time rate of change of said diffusion characteristic is increased, whereby the diffusion characteristic changes insignificantly during said predetermined exposure period.
Claim 29
Dependent Claim
86 words
The method of claim 25 wherein during said step of propagating, said short duration pulses of said object beam are elongated in time in response to said diffusing medium, said reference beam of said short duration pulses retaining a pulse duration which is very short as compared to said time rate of change of said diffusion characteristic, said pulse duration being selected in response to substantially predeterminable time rate of change of said diffusion characteristic, whereby said diffusion characteristic changes insignificantly during said second pulse duration.
Claim 30
Dependent Claim
59 words
The method of claim 25 wherein there are further provided the steps of: recording said holographic interference image; repeating said steps of generating, propagating, combining, and imaging during a subsequent exposure period to produce a subsequent holographic interference image; and integrating said holographic interference image and said subsequent holographic interference image to produce a composite image having reduced noise.
Claim 31
Dependent Claim
35 words
The method of claim 27 wherein in said step of generating, a plurality of said short duration pulses of coherent light are generated during each of said exposure periods for each respective holographic interference image.
Claim 32
Dependent Claim
30 words
The method of claim 28 wherein said steps of propagating, combining, and imaging are repeated for each of said short duration pulses of coherent light generated during said exposure period.
Claim 33
Dependent Claim
40 words
The method of claim 24 wherein there is further provided the step of synchronizing said short duration pulses of said reference beam with said first transmitted light of respective ones of said elongated short duration pulses of said object beam.
Claim 34
Dependent Claim
28 words
The method of claim 30 wherein said step of synchronizing comprises the further step of adjusting a path length of said reference beam of said short duration pulses.
References Cited (Backward Citations)
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