Abstract
A method that uses digital heterodyne holography reconstruction to extract scattered light modulated by a single-cycle ultrasound (US) burst is demonstrated and analyzed. An US burst is used to shift the pulsed laser frequency by a series of discrete harmonic frequencies which are then locked on a CCD. The analysis demonstrates that the unmodulated light's contribution to the detected signal can be canceled by appropriate selection of the pulse repetition frequency. It is also shown that the modulated signal can be maximized by selecting a pulse sequence which consists of a pulse followed by its inverted counterpart. The system is used to image a 12 mm thick chicken breast with 2 mm wide optically absorbing objects embedded at the midplane. Furthermore, the method can be revised to detect the nonlinear US modulated signal by locking at the second harmonic US frequency.
Highlights
Due to optical scattering, it is challenging to map the absorption and scattering coefficients deep inside tissue with high resolution and high contrast using optical techniques alone.Ultrasound modulated optical tomography (USMOT), combining optical and ultrasonic techniques, has the potential to provide nonionizing and noninvasive functional imaging of tissue.Coherent light and ultrasound (US) are simultaneously applied to the samples and light that passes through the US focus is phase modulated due to both a change in the refractive index and a change in the displacement of scatterers within the focal volume [1]
A digital holography-based method is demonstrated for the detection of optical signals modulated by pulsed US
These pulses are strobed by synchronized optical pulses, which produce a detection response analogous to a lock-in amplifier
Summary
It is challenging to map the absorption and scattering coefficients deep inside tissue with high resolution and high contrast using optical techniques alone. Coherent light and ultrasound (US) are simultaneously applied to the samples and light that passes through the US focus is phase modulated due to both a change in the refractive index and a change in the displacement of scatterers within the focal volume [1]. This produces a modulated optical speckle pattern at the detector plane. Parallel lock-in detection [2] can be used to lock the US modulated light at a pixelated detector and obtains high signal-to-noise ratio (SNR) due to the large optical acceptance solid angle
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
