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Proceedings Paper

An instrumentation amplifier based readout circuit for a dual element microbolometer infrared detector
Author(s): D. J. de Waal; J. Schoeman
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Paper Abstract

The infrared band is widely used in many applications to solve problems stretching over very diverse fields, ranging from medical applications like inflammation detection to military, security and safety applications employing thermal imaging in low light conditions. At the heart of these optoelectrical systems lies a sensor used to detect incident infrared radiation, and in the case of this work our focus is on uncooled microbolometers as thermal detectors. Microbolometer based thermal detectors are limited in sensitivity by various parameters, including the detector layout and design, operating temperature, air pressure and biasing that causes self heating. Traditional microbolometers use the entire membrane surface for a single detector material. This work presents the design of a readout circuit amplifier where a dual detector element microbolometer is used, rather than the traditional single element. The concept to be investigated is based on the principle that both elements will be stimulated with a similar incoming IR signal and experience the same resistive change, thus creating a common mode signal. However, such a common mode signal will be rejected by a differential amplifier, thus one element is placed within a negative resistance converter to create a differential mode signal that is twice the magnitude of the comparable single mode signal of traditional detector designs. An instrumentation amplifier is used for the final stage of the readout amplifier circuit, as it allows for very high common mode rejection with proper trimming of the Wheatstone bridge to compensate for manufacturing tolerance. It was found that by implementing the above, improved sensitivity can be achieved.

Paper Details

Date Published: 23 June 2014
PDF: 10 pages
Proc. SPIE 9257, Sensors, MEMS and Electro-Optical Systems, 92570L (23 June 2014); doi: 10.1117/12.2066301
Show Author Affiliations
D. J. de Waal, Univ. of Pretoria (South Africa)
J. Schoeman, Univ. of Pretoria (South Africa)

Published in SPIE Proceedings Vol. 9257:
Sensors, MEMS and Electro-Optical Systems
Monuko du Plessis, Editor(s)

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