Digital holographic otoscope for measurements of the human tympanic membrane in vivo

We are developing an advanced computer-controlled digital optoelectronic holographic system (DOEHS) for diagnosing middle-ear conductive disorders and investigating the causes of failure of middle-ear surgical procedures. Our current DOEHS system can provide near real-time quantitative measurements of the sound-induced nano-meter scale motion of the eardrum. The DOEHS have been deployed and is currently being tested in clinical conditions, where it is being optimized for in-vivo measurements of patients. The stability of the measurement system during examination is crucial as the non-ideal clinical environment presents disturbances larger than the measured quantities from several domains - thermal, optical, electrical and mechanical. Examples include disturbances are due to heartbeat breathing, patients head’s motion as well as environment induced mechanical disturbances (0.1-60Hz, 0.01-100 μm). In this paper we focus on our current progress in the analysis and implementation of various acquisition strategies and algorithms for minimization of the measurement error due to mechanical disturbances in a clinic. We have also developed and implemented a versatile and modular otoscope head (OH) design providing a variety of capabilities for acoustic and displacement measurements of both post-mortem samples of varying sizes (1-12mm) as well as in-vivo examination of patients. The OH offers hybrid on-axis and off axis digital Furrier holographic setup for high resolution (λ/35) 4 phase step measurements as well as fast (<0.1ms) single frame measurements for improved performance in the clinical environment. We also focus on the development of a mechatronic positioning system (MOP) for aiding in the localization of the TM in patients.