Interference contrast

Interference between two circular waves - wavelength increasing from top to bottom, distance between centers increasing to the right.

The interference contrast describes the visibility ( contrast ) of an interference phenomenon quantitatively. It is defined as the ratio of the intensities of two consecutive maxima and minima:

${\displaystyle K={\frac {I_{\mathrm {max} }-I_{\mathrm {min} }}{I_{\mathrm {max} }+I_{\mathrm {min} }}}}$

• The optimal value is 1; in the case of the interference phenomenon being completely unrecognizable, it is 0.
• This definition assumes that the mean intensity is the same . Then the amplitude is the same as the intensity . Thus applies: . ${\displaystyle (I_{\mathrm {max} }+I_{\mathrm {min} })/2}$
  ${\displaystyle (I_{\mathrm {max} }-I_{\mathrm {min} })/2}$
  ${\displaystyle K=\mathrm {Amplitude} /\mathrm {Mittelwert} }$
• In the case of interference from light, the source-dependent coherence length is usually the limiting factor.

The interference contrast is especially important for interferometry , holography and phase contrast microscopy .