Retro-reflective interferometer

A method for measurement of displacements and/or mechanical vibrations of a movable element caused by an external force, the method comprising the steps of:

• irradiating at least one retro-reflective element by one or more radiation beams;
• reflecting back said one or more radiation beams by the at least one retro-reflective element to a radiation receiver located at a plane optically conjugated with a plane of the radiation beam, being in a far field of said movable element, wherein a radiation pattern is formed by said radiation beam as result of reflection from the at least one retro-reflective element;
• detecting a sequence of said retro-reflective radiation patterns in the far field by said radiation receiver;
• said radiation patterns are modified in displacement or intensity distribution thereof, by mechanical vibration or/and displacement of said movable element caused by the external force;
• converting said sequence of the radiation patterns into a digital signal indicative of the movement of said movable element in response to said external force;
• and
• determining, by an analyzing unit, amplitudes and frequencies of the detected vibrations and/or displacement values by processing of said radiation patterns sequence.

A system for detection and measurement of displacement or/and mechanical vibrations of a surface at a remote location, the system comprising:

• a transceiver unit comprising:
• a) at least two monochromatic radiation sources capable of emitting radiation beams having different wavelengths;
• b) a beam-splitting element, capable of splitting said radiation beams to at least two coherent partial beams of each wavelength;
• c) a radiation receiver located in a plane optically coupled with a beam-splitting plane;
• a movable unit at a remote location movably mounted with respect to said transceiver unit, said movable unit comprising:
• a) one or more movable elements that are susceptible to displacement and/or vibration by an external force applied on or at the remote surface;
• b) a retro-reflective element attached to at least one of said movable elements, wherein said retro-reflective element is capable of reflecting back the at least two coherent partial beams of each wavelength generated by the beam-splitting element, to form a sequence of interference patterns in a far field, wherein said patterns are modified by the displacement or/and mechanical vibration of said movable element;
• an analyzing element operationally associated with said radiation receiver for analyzing at least one of:
• a displacement change, an intensity change and/or a frequency change in said sequence of interference patterns;
• and
• a transmitter unit configured to transmit data obtained from the analyzing element to a remote location.