Broadband Coverage Optical Sensor with Liquid Crystalline Materials and Pyroelectrics
- PDF / 995,598 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 102 Downloads / 212 Views
Broadband Coverage Optical Sensor with Liquid Crystalline Materials and Pyroelectrics Jingwen W. Zhang, Xiudong Sun, and Hua Zhao Department of Physics, Harbin Institute of Technology, Harbin, China, 150001 ABSTRACT By utilizing a thin layer of supertwisted liquid crystal and potassium sodium strontium barium noibate crystal material with excellent pyroelectric effect, a broadband coverage optical sensing concept was proposed. Coating the pyroelectric substrate with a carbon layer of excellent absorption in the frequency range of interest, the intensity of an incident mid- or far-IR radiation can be converted to a corresponding intensity variation of a reflected near-IR beam via optical modulation of the liquid crystal film. As the result, the spatial intensity distribution of an incident mid- or far-IR radiation can thus be perceived directly by a low-cost semiconductor sensor/ sensor array. With flexible design of wave collecting arrangement, the broadband coverage sensor is suitable for viewing IR-giving objects with a large field-of-view. INTRODUCTION Infrared (IR) sensing systems extend our vision beyond the short wavelength red into farIR by making visible the light naturally emitted by warm objects [1]. IR sensor development has been being an active field for military-, intelligence- and law-enforcement-related applications for many decades [2,3]. After several decades remaining in the limited sectors above for the reason of tremendous cost, a new era is ushered in by inexpensive IR sensors/sensor arrays developed recently. These IR sensors/sensor arrays could be used in a broad spectrum of civil applications, such as building inspection, home security, and nighttime walking aid situations. In the past, most interested are the two atmospheric “windows” where IR transmission is high: mid wave-IR (MWIR 3-5 μm) and long-wave IR (LWIR, 8-14 μm) ones [4], two electromagnetic (EM) wave regimes richly emitted off warm objects at ambient temperature. Recently, mid-IR to THz EM wave has exhibited a lot of scientific and commercial interests due to its extensive potential applications [5-8]. Among these applications are biological use in many sectors, such as medicine (disease and wound states, skin hydration, plaque, and bone density), homeland security (biological threat detection and explosive materials detection), astronomy exploration (planetary science and life detection), chemistry environmental sensing (water distribution and pollutants), biochemistry (DNA analysis), food industry (on-line water content monitoring) [9,10]. For technological applications, these frequencies allow much higher device performances, which may lead to a technological revolution in next generation analytic instruments, and commercial uses for long EM wave sensors are just sprouting as the technology enables new instrumentation and measurement systems. Polar dielectrics have long been of interest for electronic applications. Its extensive applications can be seen from several good reviews [11,12]. Generally, pyroelectricity, the release
Data Loading...
