Abstract-Observation of dehydration dynamics in biological tissues with terahertz digital holography

Lihan Guo, Xinke Wang, Peng Han, Wenfeng Sun, Shengfei Feng, Jiasheng Ye, and Yan Zhang

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-13-F173

A terahertz (THz) digital holographic imaging system is utilized to investigate natural dehydration processes in three types of biological tissues, including cattle, mutton, and pork. An image reconstruction algorithm is applied to remove the diffraction influence of THz waves and further improve clarity of THz images. From THz images of different biological specimens, distinctive water content as well as dehydration features of adipose and muscle tissues are precisely distinguished. By analyzing THz absorption spectra of these samples, temporal evolution characteristics of the absorbances for adipose and muscle tissues are described and compared in detail. Discrepancies between water retention ability of different animal tissues are also discussed. The imaging technique provides a valuable measurement platform for biological sensing.

© 2017 Optical Society of America

Abstract-Compressive sensing for direct millimeter-wave holographic imaging

Compressive sensing for direct millimeter-wave holographic imaging Lingbo Qiao, Yingxin Wang, Zongjun Shen, Ziran Zhao, and Zhiqiang Chen  »View Author Affiliations

http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-54-11-3280

Applied Optics, Vol. 54, Issue 11, pp. 3280-3289 (2015)
http://dx.doi.org/10.1364/AO.54.003280

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Direct millimeter-wave (MMW) holographic imaging, which provides both the amplitude and phase information by using the heterodyne mixing technique, is considered a powerful tool for personnel security surveillance. However, MWW imaging systems usually suffer from the problem of high cost or relatively long data acquisition periods for array or single-pixel systems. In this paper, compressive sensing (CS), which aims at sparse sampling, is extended to direct MMW holographic imaging for reducing the number of antenna units or the data acquisition time. First, following the scalar diffraction theory, an exact derivation of the direct MMW holographic reconstruction is presented. Then, CS reconstruction strategies for complex-valued MMW images are introduced based on the derived reconstruction formula. To pursue the applicability for near-field MMW imaging and more complicated imaging targets, three sparsity bases, including total variance, wavelet, and curvelet, are evaluated for the CS reconstruction of MMW images. We also discuss different sampling patterns for single-pixel, linear array and two-dimensional array MMW imaging systems. Both simulations and experiments demonstrate the feasibility of recovering MMW images from measurements at 1/2 or even 1/4 of the Nyquist rate.

© 2015 Optical Society of America