Rayleigh range

Determination of the Rayleigh range

Beam path of focused beam.

For a Gaussian beam the depth of focus is defined by the ­Rayleigh range 2⋅zR in which the beam waist diameter Øspot does not ­increase more than a factor of 1.41.

λ = wavelength in µm

Øspot = beam waist diameter in µm


Spot size: Øspot = 7.1 µm

Wavelength: λ = 780 nm

Rayleigh range: 2zR=20.3 µm