Fáziseltéréstl

Fáziseltéréstl is a term used in physics and engineering to denote a phase shift, the difference in the phase angle between two periodic signals or waves. The shift is commonly expressed in radians or degrees and, for a constant frequency f, corresponds to a time delay Δt via φ = ωΔt, where ω = 2πf. In optics, a phase shift produced by a path length difference ΔL is φ = (2π/λ)ΔL, with λ the wavelength. Different conventions may apply opposite signs depending on the reference.

Causes of phase shifts include differences in propagation speed through media, geometric path differences, dispersion, modulation, and delays in measurement or processing systems. Phase shifts are central to interference phenomena: when waves with a given φ combine, they may interfere constructively or destructively, affecting the resultant amplitude.

Measurement and estimation methods rely on comparing phases. Interferometry (for example Michelson or Mach–Zehnder setups) directly measures phase differences between beams. Phase-sensitive detection, such as phase-locked loops or lock-in amplifiers, can extract phase information from noisy signals. In digital signal processing, phase unwrapping techniques are used to recover continuous phase across frequency bands.

Applications span telecommunications, where phase modulation and phase-shift keying encode information; radar and LIDAR, where phase differences relate to distance and motion; and optical imaging and metrology, including microscopy and material characterization. Phase information enables sensing of distances, refractive index changes, and dynamic properties of systems.

Challenges include the periodic nature of phase modulo 2π, which requires unwrapping to obtain continuous phase estimates; sensitivity to noise, dispersion, and multipath effects; and the need for careful calibration in instruments to avoid biased phase measurements.