Abstract: Vibrations of a body are measured by attaching a vibrating element to the body, directing a beam of electromagnetic energy onto the vibrating element and collecting reflected electromagnetic energy from the vibrating element. The magnitude of the reflected electromagnetic energy is processed to determine vibration and/or temperature of the body. The magnitude of the reflected light is preferably a function of second degree of the position of said vibrating element. Processing said magnitude of reflected electromagnetic energy is preferably done by a Fourier series up to a second harmonic.

Abstract: The sensor comprises a vibrating sheet (1), mechanically connected to the body (5A) to be analyzed, and an optical triangulation recording system for recording the displacements of the movable part of the sheet, in particular the free end (1B) opposite to that which is restrained. The recording system comprises two optical fibers (7, 9) ending in microlenses (10, 12) having optical axes mutually inclined and converging in the movable part (1B) of the sheet.