Abstract: An improved detector having a reflective surface which is substantially insensitive to vibration. The detection surface comprises a thin layer of liquid metal which is disposed over a substantially rigid, wettable substrate. In a presently preferred embodiment, the detector comprises a receptacle having disposed therein a rigid brass plate covered by a thin layer of mercury. The detector is submersed in a suitable fluid, such as water, to which an acidic substance has been added to reduce the pH of the fluid to the range of 5 to 6.

Abstract: An improved system for ensonifying an object, which comprises upper and lower fluid-filled chambers. The chambers are separated by a partition including a lens; a further, movable lens may be disposed within the upper chamber. A reflective-type detector is disposed in the floor of the bottom chamber, and ports provided at opposite sides of the chamber for light impinging upon, and reflected from, the detector surface. A resilient closure at the upper end of the upper chamber conformably receives the surface of an object to be ensonified. A transducer producing the object, or ensonifying, acoustic beam is disposed within another fluid-filled enclosure one wall of which comprises a flexible membrane. The latter membrane is disposed against the upper side of the object to be ensonified and conforms thereto so that a relatively continuous fluid path is presented between the transducer and the object, and from the object to the detector.