A self-mixing laser-diode interferometer for measuring basilar membrane vibrations without opening the cochlea

Andrei N. Lukashkin, Mikhail E. Bashtanov, Ian J. Russell

Research output: Contribution to journalArticle

Abstract

A laser-diode forms the basis of a displacement sensitive homodyne interferometer suitable for measurements from poorly reflective surfaces. The compact and cost-effective interferometer utilizes the self-mixing effect when laser light reflected from a moving target re-enters the laser cavity and causes phase dependent changes of the lasing intensity. A piezo positioner was used to displace the interferometer with known frequency and amplitude as a basis for real-time calibration of the interferometer's sensitivity. The signal-processing algorithm is described that allows measurements in presence of high amplitude noise leading to variation of the interferometer's operating point. Measurements of sound-induced basilar membrane displacements were made in the intact cochleae of rodents by focusing the laser beam of the interferometer through the transparent round window membrane. The interferometer provides a viable means for making subnanometre mechanical measurements from structures in the inner ears of small mammals, where opening of the cochlea is not practicable.

Original languageEnglish
Pages (from-to)122-129
Number of pages8
JournalJournal of Neuroscience Methods
Volume148
Issue number2
DOIs
Publication statusPublished - 30 Oct 2005

Keywords

  • Basilar membrane
  • Cochlear mechanics
  • Interferometry
  • Self-mixing

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