Coherent imaging

In coherent imaging, complex wave amplitudes add with their relative wave phases preserved. The measured light intensity includes wave interference between the contributions.

For an ideal on-axis coherent circular-pupil system the field transfer cutoff is ${\nu }_c=\mathrm{NA}/\lambda$. Incoherent intensity transfer extends to $2\mathrm{NA}/\lambda$. Field and intensity transfer functions must be distinguished.

The amplitude spread function is the complex field response to an optical point source. Its squared magnitude, with a specified point spread function normalization, gives the intensity point spread function.