Characterization and evaluation of high frequency convex array transducers

High frequency, 20 MHz convex array transducers have been fabricated and characterized. An array geometry of 111 μm pitch, 23.6 mm radius of curvature, 52° maximum view angle, 7 mm elevation width, 192 elements and 30 mm geometric focus were chosen to cover the entire eyeball in one imaging plane. Pulse-echo measurements of all 192 elements showed that 8 elements were open with no shorted ones. The average values of measured parameters for all elements excluding open ones were -63.7 dB loop sensitivity, 19.6 MHz -6 dB center frequency and 69.2% -6 dB fractional bandwidth, all with less than 5% standard deviation. Element-to-element variation of measured parameters has been found to be acceptable for imaging purposes. Bovine eye images obtained by convex arrays provided a wider viewing area than those by linear arrays. Strong echoes from retinal layers of the posterior segment of a bovine eye were observed. Real-time images of excised bovine eyes have been acquired by a 64-channel imaging system.