Lock-in camera based heterodyne holography for ultrasound-modulated optical tomography inside dynamic scattering media

• Published in: Applied physics letters Vol. 108; no. 23; p. 231106
• Main Authors: Liu, Yan, Shen, Yuecheng, Ma, Cheng, Shi, Junhui, Wang, Lihong V.
• Format: Journal Article
• Language: English
• Published: United States American Institute of Physics 06-06-2016; AIP Publishing LLC
• Subjects: Applied physics; Digitization; Extreme values; Holography; Image contrast; Photonics and Optoelectronics; Scattering; Ultrasonic imaging
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4953630

Ultrasound-modulated optical tomography (UOT) images optical contrast deep inside scattering media.
Heterodyne
holography based
UOT is a promising technique that uses a camera for parallel speckle detection. In previous
works, the speed of data acquisition was limited by the low frame rates of conventional
cameras. In
addition, when the signal-to-background ratio was low, these cameras wasted most of their
bits representing an informationless background, resulting in extremely low efficiencies
in the use of bits. Here, using a lock-in camera, we increase the bit efficiency and reduce the data
transfer load by digitizing only the signal after rejecting the background. Moreover,
compared with the conventional four-frame based amplitude measurement method, our
single-frame method is more immune to speckle
decorrelation.
Using lock-in camera based UOT with an integration time of 286 μs,
we imaged an
absorptive object buried inside a dynamic scattering medium exhibiting a speckle
correlation time (
τ
c
) as short as 26 μs. Since our method can
tolerate speckle
decorrelation
faster than that found in living biological tissue (
τ
c
∼ 100–1000 μs), it is promising for
in vivo deep tissue non-invasive imaging.