US 5,299,035 AGranted

Holographic imaging through scattering media

AssigneeUniversity of Michigan

InventorsEmmett N. Leith, David S. Dilworth, Hsuan S. Chen, Ye Chen, Joaquin L. Lopez, Janis A. Valdmanis

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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.

Claims31

Dependent claims

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.

2 more elements

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.

3 more elements

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.

3 more elements

Dependencies are inferred from the claim text.