Depth-enhanced 2-D optical coherence tomography using complex wavefront shaping

Abstract

We report the enhancement in the obtained signal and penetration depth of 2-D depth-resolved images that were taken by shaping the incident wavefront in optical coherence tomography (OCT). Limitations in the penetration depth and signal to noise ratio (SNR) in OCT are mainly due to multiple scattering, which have been effectively suppressed by controlling the incident wavefront using a digital mirror device (DMD) in combination with spectral-domain OCT. The successful enhancements in the penetration depth and SNR are demonstrated in a wide-range of tissue phantoms, reaching depth enhancement of up to 92%. The hidden structures inside a tissue phantom that could not be seen in conventional OCT are clearly revealed through our proposed system. Its 2-D imaging capability, assisted by further optimization of the system for real-time acquisition speed will boost wide-spread use of OCT for in-vivo tissue diagnosis.

Feedback-based wavefront shaping

“…A special case of iterative approaches was demonstrated by Nixon et al, who used an optical gain medium as an analog feedback mechanism to find lasing modes through scattering media [67]. Also, a promising direction may be to combine wavefront shaping with coherence gating, in order to achieve depth-selective focusing [68], or to reduce the amount of scattered light [69]. Feedback-based wavefront shaping can basically generate any spatio-temporal mode that one is able to detect; a feature that was convincingly demonstrated by Aulbach et al [70] who used spatial wavefront shaping in combination with a scattering medium to guide light into any desired spatio-temporal mode.…”

In vivodeep tissue imaging using wavefront shaping optical coherence tomography

“…By controlling the wavefront of an impinging beam, control of the light field transmitted through a turbid media can be achieved through linear coherent relationships between input and transmitted fields, which are described by scattering matrices [21][22][23] . Wavefront shaping approaches have been applied to low-coherence interferometry, including selective focusing in optical coherence microscopy 24 ; the penetration depth has been enhanced in spectral domain OCT 25,26 , called wavefront shaping OCT (WS-OCT); imaging deep in turbid media by collective accumulation of single-scattered waves from a time-resolved reflection matrix 27 . Exploiting this approach, significant advances have been made in the last few years in enhancing the penetration depth of low coherence interferometric imaging systems.…”

Collaborative effects of wavefront shaping and optical clearing agent in optical coherence tomography

“…The wavefront shaping technique also has much room for improvement. In our previous results 37 , the depth enhancement factor increases as the scattering of the tissue phantom is reduced. This trend shows a positive sign that further optimization of collaborative effect can lead to the synergetic effect of the both method, where the depth enhancement is greater than the sum of individual effects.…”

“…2. The system was adapted from an SD-OCT system by incorporating high-speed wavefront modulation 37 . In a conventional system, a collimated beam from an illumination source directly passes through a beam splitter and the divided beams arrive incident on a sample and a reference mirror, respectively.…”