Abstract
Extension of the dynamic range of liquid crystal tunable Lyot filter is demonstrated by incorporating with it a liquid crystal variable retarder as an eliminator for the third and fourth order peaks. The filter is continuously tunable in the range 500 nm to 900 nm with a nominal width in the range 50nm-100nm. Design procedure is described including the exact solution to the LC director profile and the suitability for biomedical optical imaging applications. Flexibility in the design is proposed by applying different voltages to the different liquid crystal retarders thus compensating for small thickness deviations from the nominal values and obtaining the high dynamic range.
Highlights
Birefringent filters are known for long time [1], lately they gained high practical importance due to the possibility of tuning them by a small voltage when made from liquid crystals (LCs)
liquid crystal tunable filters (LCTFs) based on nematic LCs exhibit response time in the tens of msec range depending on the configuration used, while higher speeds in the tens of microseconds range can be obtained using ferroelectric liquid crystals
In this paper we demonstrate an extension of the free spectral range (FSR) of Lyot-based filter by integrating with it an additional variable LC retarder that eliminates actively the unwanted interference orders
Summary
Birefringent filters are known for long time [1], lately they gained high practical importance due to the possibility of tuning them by a small voltage when made from liquid crystals (LCs). For biomedical imaging [26] the interest is usually in the therapeutic window (750-1300 nm) because the penetration depth in the tissue is high in this range; for analytes functional imaging such as for oxygen blood saturation measurement through the eye [27] one or more measurements are required in the visible range as well. This and together with the fact that Si detectors and CCD or CMOS cameras are reasonably sensitive up to 900nm, a practically desirable range is 500-900nm. In this paper we demonstrate an extension of the FSR of Lyot-based filter by integrating with it an additional variable LC retarder that eliminates actively the unwanted interference orders
Sign-in/Register to view highlights & summary 
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call