A system for detecting pressure, acoustic or ultrasound waves within an entity having a surface including the steps of attaching a signal converting material to the surface. The waves are generated by direct ejection from the surface, generation via energy deposition on the surface, generated spontaneously or, generated by directing light energy to the light absorbing target. The absorbing target subsequently generates acoustic pressure waves. The acoustic waves propagate to the surface of the entity and the signal converting material, wherein the acoustic pressure waves create vibrations in the signal converting material； and detecting the waves in the signal converting material with an optical detection system. Information about the absorbing target is obtained by the absorbing target reflecting the waves. The signal converting material can be a gel-like material containing optical elements, a multi-layer patch, or other material.
