| Ultrasound transducer solutions were proposed for imaging the posterior segment of the human eye. In one approach, concentric annular type dual element transducers for second harmonic imaging at 20 MHz/40 MHz were designed and fabricated for imaging the posterior segment of the eye. The outer ring element was designed to transmit the 20 MHz signal and the inner circular element was designed to receive the 40 MHz second harmonic signal. Multiple prototype transducers were fabricated and characterized quantitatively. Images of a posterior segment of an excised pig eye and a choroidal nevus of human eye were obtained and the advantages of dual element harmonic imaging were demonstrated. In another approach, 20 MHz 192 element convex array transducers have been designed, fabricated, and characterized. It was demonstrated that convex array transducers of 20 MHz with an aperture curved both in azimuth and elevation direction could be fabricated with an acceptable uniformity in element-by-element performance. All 192 elements of the array were fully characterized by the pulse-echo test, crosstalk measurement, insertion loss test and synthetic aperture imaging. Average pulse-echo loop sensitivity was --63.7 dB and average --6 dB fractional bandwidth 69.2%, which are acceptable for imaging purpose. Ringing of echoes was substantially reduced by using a lower composite kerf by the interdigital pair bonding for fabricating 1-3 composites. Created images of ex vivo porcine eye tissues with a trapezoidal field of view were shown to a wider view angle than linear arrays. |
