• Korean Journal of Optics and Photonics
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• v.29 no.3
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• pp.99-103
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• 2018

Optical coherence elastography (OCE) is based on optical coherence tomography (OCT), which is a noninvasive, high-resolution, cross-sectional imaging technique. In this paper, we have developed dynamic optical coherence elastography to measure elasticity, a mechanical property of tissue, by phase difference. A piezoelectric actuator was used for sinusoidal mechanical loading of samples. Before applying this method to biomaterial, we assessed the feasibility of OCE with samples of sponge, eraser, and sharp lead. Cross-sectional and phase-difference images of the sample were obtained under sinusoidal loading. The strain rate was calculated from the phase-difference information. To obtain the envelope of the phase-difference oscillations along the horizontal direction, Hilbert transformation was performed at each depth. The elevation of the envelope was represented by color mapping, and we could measure the relative elasticity within the sample by comparing the elevations. Finally, there was an advantage when we calculated the shear rate using self-interference in the sample arm, instead of the interference between sample and reference arms.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.96-107
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• 2011

Recently, studies of 3D HDTV broadcasting technology have been processed actively. Korea is making efforts to modify Advanced Television Systems Committee (ATSC) 8-Vestigial Side Band (8-VSB) systems for terrestrial 3D HDTV broadcasting services. We intend to adopt a new frame structure to use PN (Pseudo-Noise) sequence as frame header, and VSB modulation. PN sequence is used to recover carrier freqeuncy offset, carrier phase error. In this paper, we will describe this system as the modified ATSC systems. The receiver of the modified ATSC system should be able to estimate and recover carrier frequency offset exactly. A existing ATSC systems inserts pilot to recover carrier frequency offset, on the other hand the modified ATSC systems use PN sequence to recovery carrier frequency offset without the use of pilot. In this paper, we introduce carrier frequency recovery (CFR) scheme for the modified ATSC systems. The proposed CFR scheme is composed of coarse CFR scheme using Fitz algorithm and fine CFR scheme using a simple PN sequence correlation algorithm. And, the symbol information of QAM modulated signal is contained in both In-phase (I)channel and Quadrature-phase (Q)channel. However the symbol information of VSB modulated signal is contained in I channel, and Q channel is just Hilbert transform of I channel. For the reason, VSB modulated symbols can not have fixed phase like QAM modulated symbols, and VSB modulated symbols is more sensitive to carrier frequency offset. Therefore we perform phase correction of received PN sequence to improve performance.