ABSTRACT
Recently an optoelectronic holography system was deployed in the clinic with the purpose of quantifying the tympanic membrane (TM) displacements of various mammal species, the objective being the understanding of their middle ear biomechanics. The optoelectronic holography system has an in-line configuration where the data gathered is decoded using lensless digital holography with the Fresnel approximation. This paper presents quantitative data obtained from an acoustically excited postmortem chinchilla's TM. To achieve this we used a robust customized windowed unwrapping method to unwrap the noisy optical phase obtained by subtracting phase maps of two recorded holograms and the results were compared with those obtained when using the unwrapping branch-cut algorithm. Additionally, phase maps obtained by the phase-stepping technique were compared applying both unwrapping methods. For in vivo applications particular emphasis is made on post-processing dual-shot-acquisition of holograms as one of various acquisition strategies and algorithms to diminish measurement error due to heartbeat, breathing, and patient's head motion as well as environment induced mechanical disturbances present in a noncontrolled environment, such as in a clinic. By recording only two holograms representing a stationary and deformed state of eardrum, respectively, we can increase the acquisition speed of the camera used to record faster events happening on the TM surface.
Subject(s)
Holography/instrumentation , Holography/methods , Image Interpretation, Computer-Assisted/instrumentation , Image Interpretation, Computer-Assisted/methods , Movement/physiology , Otoscopes , Tympanic Membrane/physiology , Algorithms , Animals , Chinchilla , Equipment Design , Equipment Failure Analysis , Otoscopy/methods , Tympanic Membrane/anatomy & histology , VibrationABSTRACT
Three-dimensional digital holography with three object-illuminating beams has been successfully used for the detection of surface strain in metallic objects. The optical setup that uses illuminating beams to irradiate the object from three directions means that all three object surface displacement components, x, y, and z, can be independently calculated and used to find the strain gradients on the surface. The results show the conversion of the complete surface displacement field into a surface strain field. The method is capable of measuring microstrains for out-of-plane surface displacements of less than 10 microm.