<p>An optical acoustoelectric transducer receives light reflected by a vibrating board and detects the displacement of the vibrating board. A surface-emitting luminescent device having a substantially uniform concentric intensity distribution of light emission is placed in the center of a common substrate. A photodetector element is provided to surround the luminescent device. A lens is also provided in the optical path between the substrate and the vibrating board to converge the light traveling toward and from the vibrating board. <IMAGE></p>
