A Caltech Library Service

Improving the axial resolution in time-reversed ultrasonically encoded (TRUE) optical focusing with dual ultrasonic waves

Yang, Qiang and Xu, Xiao and Lai, Puxiang and Sang, Xinzhu and Wang, Lihong V. (2014) Improving the axial resolution in time-reversed ultrasonically encoded (TRUE) optical focusing with dual ultrasonic waves. In: Photons Plus Ultrasound: Imaging and Sensing 2014. Proceedings of SPIE. No.8943. Society of Photo-Optical Instrumentation Engineers , Bellingham, WA, Art. No. 894338. ISBN 9780819498564.

[img] PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


Focusing light inside highly scattering media beyond the ballistic regime is a challenging task in biomedical optical imaging, manipulation, and therapy. This challenge can be overcome by time reversing ultrasonically encoded (TRUE) diffuse light to the ultrasonic focus inside a turbid medium. In TRUE optical focusing, a photorefractive crystal or polymer is used as the phase conjugate mirror for optical time reversal. Accordingly, a relatively long ultrasound burst, whose duration matches the response time of the photorefractive material, is used to encode the diffuse light. With this long ultrasound burst, the resolution of the TRUE focus along the acoustic axis is poor. In this work, we used two transducers, emitting two intersecting ultrasound beams at 3.4 MHz and 3.6 MHz respectively, to modulate the diffuse light within their intersection volume at the beat frequency. We show that light encoded at the beat frequency can be time-reversed and converge to the intersection volume. Experimentally, TRUE focusing with an acoustic axial resolution of ~1.1 mm was demonstrated inside turbid media, agreeing with the theoretical estimation.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Wang, Lihong V.0000-0001-9783-4383
Additional Information:© 2014 Society of Photo-Optical Instrumentation Engineers. The authors thank Yan Liu for helpful discussions on resolution. This work was conducted at Washington University in Saint Louis, and sponsored in part by National Academies Keck Futures Initiative grant IS 13, and National Institutes of Health grants DP1 EB016986 (NIH Director’s Pioneer Award) and U54 CA136398.
Funding AgencyGrant Number
National Academies Keck Futures InitiativeIS 13
NIHDP1 EB016986
NIHU54 CA136398
Subject Keywords:tissue optics, optical imaging, time-reversed ultrasonically encoded (TRUE) optical focusing, optical phase conjugation, axial resolution, photorefractive crystal
Series Name:Proceedings of SPIE
Issue or Number:8943
Record Number:CaltechAUTHORS:20180912-094150179
Persistent URL:
Official Citation:Qiang Yang, Qiang Yang, Xiao Xu, Xiao Xu, Puxiang Lai, Puxiang Lai, Xinzhu Sang, Xinzhu Sang, Lihong V. Wang, Lihong V. Wang, } "Improving the axial resolution in time-reversed ultrasonically encoded (TRUE) optical focusing with dual ultrasonic waves", Proc. SPIE 8943, Photons Plus Ultrasound: Imaging and Sensing 2014, 894338 (3 March 2014); doi: 10.1117/12.2038797;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89562
Deposited By: Tony Diaz
Deposited On:12 Sep 2018 18:53
Last Modified:03 Oct 2019 20:17

Repository Staff Only: item control page