Novel solid state modulator for the infrared : the germanium chopper

Autor: Fairley, Peter Douglas
Rok vydání: 2000
Předmět:
Druh dokumentu: Electronic Thesis or Dissertation
Popis: Uncooled thermal imaging cameras in the 8 to 14 µm band use pyroelectric array detectors as the preferred technology. The systems advantages offered by these uncooled detectors are those of reduced cost, complexity and power consumption. The price paid for this uncooled technology is that the image must be modulated in order to generate a change in signal intensity on the detector. Currently this is achieved using a rotating chopper blade, which introduces moving parts to the system, and has the drawbacks of size and image degradation as camera motion changes the blade's rotational speed. A need has existed for considerable time for solid state broad optical bandwidth modulation in the infrared. The application requires modulation of the 8 to 14 µm band with high 'on' state transmission, although not necessarily a very low 'off' state transmission. Crucially this must be over a relatively large (1 cm2) aperture. The modulator should be insensitive to polarisation since this would halve the image intensity from a randomly polarised scene, reducing the system signal to noise ratio. Low power consumption, compactness, and the incorporation into a low f-number optical system are the systems requirements for this application. The specification is eased only by the moderate chopping frequencies
Databáze: Networked Digital Library of Theses & Dissertations
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