Design and Optimization of a Capacitive Micromachined Ultrasonic Transducer Micro-Array for Near Field Sensing

The design of a tool-tip mounted cMUT (capacitive micromachined ultrasonic transducer) micro-array for near field imaging of the retina is undertaken. For intra-vitreal applications, a uniformly excited NtimesN transducer array is limited to a size of 2mm times 2mm. The physical parameters of the array are constrained by the imaging requirements of a 2 mum resolution and a distance of 400 mum from the retinal surface. The mechanical and electrical parameters of the cMUT are calculated using a combination of the Mason equivalent circuit model and finite element techniques. Optimal transmit power and receive sensitivity for this imaging application are obtained by coupling the transducer model to a pseudo-spectral wave propagation model. The pseudo-spectral method is used to calculate the frequency dependent attenuation of the transmitted acoustic pulse through the vitreous and retinal media. The subsequent reflected wavefront is used to optimize the array transmit power and sensitivity