Wellenfront

Wellenfront, or wavefront in optics, is a surface over which the optical phase of a propagating wave is constant. For monochromatic light in a uniform medium, the wavefront is perpendicular to the local direction of energy flow; the wave propagates normal to the surface. The speed of propagation is c/n, with c the vacuum speed and n the refractive index.

Real wavefronts vary in shape: planar wavefronts occur in collimated beams or at large distances, while spherical wavefronts originate from a point source. More generally, curved wavefronts arise from lenses, mirrors, or spatial phase variations. The shape of the wavefront determines how rays emerge and how images form.

Wavefront quality is a measure of optical aberrations. Wavefront error can be quantified by RMS or peak-to-valley deviation from an ideal shape. In imaging and astronomy, wavefront sensing and correction are used to improve resolution: Shack–Hartmann sensors, interferometric methods, and adaptive optics measure the wavefront and compensate phase distortions in real time.

Mathematically, the wavefront is the surface on which the optical phase φ(x,y,z,t) = ωt − k·r is constant. The gradient ∇φ is normal to the wavefront and aligns with the local propagation direction; rays are drawn perpendicular to wavefronts (geometric optics). The wavefront concept underlies Huygens’ principle and the Fresnel–Kirchhoff diffraction framework.