A system for non-invasively detecting vital signs of a subject, including a) a sub-THz beam source, b) an optical interferometer that is configured to accept the sub-THz beam, split the sub-THz beam into a reference beam and a measurement beam, focus the measurement beam onto a subject, accept a reflection of the beam from the subject and combine the reflection of the measurement beam with the reference beam； c) a detector configured to detect the combined beam； and an electronic circuit configured to receive and analyze the detected combined beam and identify vital signs of the subject.
