New frequency‐domain electric birefringence spectrometer using an advanced digital lock‐in technique

1991 ◽  
Vol 62 (4) ◽  
pp. 948-956 ◽  
Author(s):  
Norio Ookubo
Keyword(s):  
Frequency Domain ◽  
Electric Birefringence ◽  
Lock In

Single-Pixel Spatial Frequency Domain Imaging System Based on Lock-in Photon-Counting Detection

2019 ◽  
Vol 39 (4) ◽  
pp. 0412002
Author(s):  
赵宽心 Zhao Kuanxin ◽  
李同心 Li Tongxin ◽  
侯茜 Hou Xi ◽  
但迈 Dan Mai ◽  
高峰 Gao Feng
Keyword(s):  
Spatial Frequency ◽  
Frequency Domain ◽  
Imaging System ◽  
Photon Counting ◽  
Spatial Frequency Domain Imaging ◽  
Lock In ◽  
Single Pixel ◽  
Spatial Frequency Domain

Intrachain conduction and main-chain conformation of conducting polymers as studied by frequency-domain electric birefringence spectroscopy

1994 ◽  
Vol 72 (13) ◽  
pp. 2073-2076 ◽  
Author(s):  
Takeshi Shimomura ◽  
Haruhiko Sato ◽  
Hiroshi Furusawa ◽  
Yasuyuki Kimura ◽  
Hajime Okumoto ◽  
...  
Keyword(s):  
Conducting Polymers ◽  
Frequency Domain ◽  
Main Chain ◽  
Chain Conformation ◽  
Electric Birefringence

A New Method of Dynamic Electric Birefringence Measurement Using a Sinusoidal Digital Lock-In System

1980 ◽  
Vol 19 (11) ◽  
pp. 2271-2278 ◽  
Author(s):  
Norio Ookubo ◽  
Yasushi Mori ◽  
Reinosuke Hayakawa ◽  
Yasaku Wada
Keyword(s):  
New Method ◽  
Electric Birefringence ◽  
Lock In

scholarly journals Laser Photothermoacoustic Heterodyned Lock-in Depth Profilometry in Turbid Tissue Phantoms

2021 ◽  
Author(s):  
Ying Fang ◽  
Andreas Mandelis ◽  
Gloria Spirou ◽  
I. Alex Vitkin ◽  
William M. Whelan
Keyword(s):  
Frequency Domain ◽  
Delay Time ◽  
Turbid Media ◽  
Laser Source ◽  
Depth Information ◽  
Chirp Signal ◽  
Sweep Method ◽  
Frequency Sweep ◽  
Linear Frequency ◽  
Lock In

Frequency-domain correlation and spectral analysis photothermoacoustic FD-PTA imaging is a promisingnew technique, which is being developed to detect tumor masses in turbid biological tissue. Unlike conventional biomedical photoacoustics which uses time-of-flight acoustic information induced by a pulsed laser to indicate the tumor size and location, in this research, a new FD-PTA instrument featuring frequency sweep chirp and heterodyne modulation and lock-in detection of a continuous-wave laser source at 1064 nm wavelength is constructed and tested for its depth profilometric capabilities with regard to turbid media imaging. Owing to the linear relationship between the depth of acoustic signal generation and the delay time of signal arrival to the transducer, information specific to a particular depth can be associated with a particular frequency in the chirp signal. Scanning laser-fluence modulation frequencies with a linear frequency sweep method preserves the depth-to-delay time linearity and recovers FD-PTA signals from a range of depths. Combining with the depth information carried by the back-propagated acoustic chirp signal at each scanning position, one could rapidly generate subsurface three-dimensional images of the scanning area at optimal signal-to-noise ratios and low laser fluences, a combination of tasks that is difficult or impossible by use of pulsed photoacoustic detection. In this paper, results of PTA scans performed on tissue mimicking control phantoms with various optical, acoustical, and geometrical properties are presented. A mathematical model is developed to study the laser-induced photothermoacoustic waves in turbid media. The model includes both the scattering and absorption properties of the turbid medium. A good agreement is obtained between the experimental and numerical results. It is concluded that frequency domain photothermoacoustics using a linear frequency sweep method and heterodyne lock-in detection has the potential to be a reliable tool for biomedical depth-profilometric imaging.

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