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Optical Engineering

32×32 pixel array complementary metal-oxide semiconductor imaging sensor for laser Doppler blood-flow measurement
Author(s): Diwei He; Chayut Kongsavatsak; Barrie R. Hayes-Gill; John A. Crowe; Stephen P. Morgan
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Paper Abstract

A 32×32 pixel array has been fabricated in a 0.35-μm complementary metal-oxide semiconductor process with the aim of producing two-dimensional laser Doppler blood-flow images. In the design, each pixel contains five basic elements: a photodiode, a front-end consisting of a current to voltage converter, voltage amplifier, antialiasing filter, and buffer. The analog design is optimized for the detection of laser Doppler blood-flow signals and thus offers advantages over conventional sensors. The analog outputs are passed through an on-chip multiplexer and digitized by an external analog-to-digital converter. The sensor has been fully characterized electrically and optically using modulated electrical and optical signals. A calibration process for fixed pattern noise reduces the standard deviation of the ac gain by a factor of 2. The imaging response is tested by imaging a vibrating test structure and a rotating diffuser. Blood-flow measurements on a finger before and after occlusion demonstrate that the sensor array is capable of detecting blood-flow signals from tissue. The knowledge gained from the characterization of the design can be used to develop a fully integrated laser Doppler blood-flow sensors with a higher number of pixels.

Paper Details

Date Published: 1 May 2011
PDF: 12 pages
Opt. Eng. 50(5) 054403 doi: 10.1117/1.3580661
Published in: Optical Engineering Volume 50, Issue 5
Show Author Affiliations
Diwei He, The Univ. of Nottingham (United Kingdom)
Chayut Kongsavatsak, The Univ. of Nottingham (United Kingdom)
Barrie R. Hayes-Gill, The Univ. of Nottingham (United Kingdom)
John A. Crowe, The Univ. of Nottingham (United Kingdom)
Stephen P. Morgan, The Univ. of Nottingham (United Kingdom)

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