Four point photo-conductance (FPPC) monitoring array for speckle and fringe motion sensing

Jonathan Bessette; Ashifi Gogo; Elsa Garmire

doi:10.1117/12.686184

18 October 2006 Four point photo-conductance (FPPC) monitoring array for speckle and fringe motion sensing

Jonathan Bessette, Ashifi Gogo, Elsa Garmire

Proceedings Volume 6379, Photonic Applications for Aerospace, Transportation, and Harsh Environments; 637903 (2006) https://doi.org/10.1117/12.686184
Event: Optics East 2006, 2006, Boston, Massachusetts, United States

Abstract

We report on the increase in frequency response of a semi-insulating GaAs Four Point Photo-Conductance (FPPC) remote vibration monitoring array. This simple, rugged device works by monitoring the lateral motion of an illumination pattern and has been demonstrated for remote, non-contact vibration sensing applications in the kilohertz regime at a distance over five meters. The FPPC sensor requires only a line-of-sight path to the object being probed (although later models are expected to work also with multimode fiber optics feed). Due to its construction and application to remote sensing, the FPPC device enables measuring vibrating bodies enclosed in a high temperature or pressure environment without adverse effects. This paper reports techniques for increasing the frequency response in these sensors. Experimental results will be given on sensors that have an approximate -3 db rolloff frequency of 10 kHz to 40 kHz. The performance improvements were achieved by replacing the opaque AuGe electrical contacts with transparent Indium Tin Oxide (ITO) contacts. These 80 nm thick films were deposited by RF sputtering at 3 mTorr Argon back pressure. Further frequency response improvements were obtained by increasing the array conductivity with background illumination from a red LED. These improvements are attributed to the reduction in lateral trapped space charge distribution across the active areas. The FPPC devices exhibited rise times of 1.5 microseconds and effective fall times of 100 microseconds. The pulse response exhibited tails with an underdamped oscillatory behavior; the damping increased with increasing background illumination.

Citation Download Citation

Jonathan Bessette, Ashifi Gogo, and Elsa Garmire "Four point photo-conductance (FPPC) monitoring array for speckle and fringe motion sensing", Proc. SPIE 6379, Photonic Applications for Aerospace, Transportation, and Harsh Environments, 637903 (18 October 2006); https://doi.org/10.1117/12.686184

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available