Using a new liquid-crystal polarization modulator for a polarimetric glucose sensor

Tsung Chih Yu, Yu Lung Lo

Research output: Contribution to journalConference articlepeer-review

1 Citation (Scopus)


This paper presents a new liquid-crystal polarization modulator comprising a nematic liquid-crystal variable retarder (LCVR) and two quarter-wave plates for the measurement of glucose concentrations. Rather than using a conventional Faraday modulator, this study firstly adopts a LCVR driven by sinusoidal signals to modulate the polarization angle of the light as a sinusoidal function. It is found that the variation frequency of the polarization angle doubles that of the driving signal, and the modulation depth is not proportional to the driving amplitude. These features are quite different from a Faraday modulator. Therefore, a signal demodulation algorithm which developed to adapt the particular features of the LC modulator enables the polarization rotation angle corresponding to the glucose concentration to be derived. The proposed measurement method has a minimum resolution of 0.05 degrees corresponding to a glucose concentration of 0.2 g/dl. Compared to its conventional counterparts, the developed polarimeter has a simpler structure, fewer optical elements, and a cheaper modulator component.

Original languageEnglish
Article number03
Pages (from-to)21-27
Number of pages7
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume5852 PART I
Publication statusPublished - 2005 Dec 12
EventThird International Conference on Experimental Mechanics and Third Conference of the Asian Committee on Experimental Mechanics - Singapore, Singapore
Duration: 2004 Nov 292004 Dec 1

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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