Dopplertehnika

Dopplertehnika refers to a family of techniques based on the Doppler effect, the change in frequency of a wave relative to the motion of its source or observer. These methods rely on transmitting waves—such as sound, light, or radio—and detecting the frequency shift of the waves after interaction with moving targets or scattering structures. The observed Doppler shift is proportional to the velocity component along the line of sight and depends on the angle between the wave direction and the motion.

In medical imaging, Doppler ultrasound is a widely used modality for assessing blood flow in vessels and the heart. It detects frequency shifts of echoes from moving blood cells to provide information about flow velocity and direction. Variants include pulsed-wave Doppler, continuous-wave Doppler, color Doppler (overlay of flow on anatomical images), and power Doppler (sensitive to flow presence without direction). Advantages include real-time, noninvasive assessment; limitations involve angle dependence, potential for aliasing, and operator influence.

Radar and lidar applications use Doppler techniques to measure the velocity of moving objects. Doppler radar is common in aviation, meteorology, and automotive safety systems, where radial velocity along the line of sight is estimated. In meteorology, Doppler radar maps wind speeds and detects precipitation motion.

In astronomy and spectroscopy, Doppler shifts of spectral lines reveal the radial velocities of stars and galaxies, aiding studies of stellar dynamics, exoplanets, and cosmic expansion. Acoustic Doppler velocimetry and related methods employ sound waves to measure fluid velocities in laboratory and industrial contexts.

Historically named for Christian Doppler, the technique spans science and engineering, providing a noncontact means to quantify motion across diverse domains.