Let p(;y) be a pulse field of identical pulses.
By modulating the pulse density of this field, we
can shape its spectrumS In this manner we can
approximate the spectrum of a given intensity
distribution in a certain frequency band.
Pierre M.T. van den Bulck,
"First-order error-diffusion considered as discrete pulse-density modulation", Proc. SPIE 1319, Optics in Complex Systems, (1 July 1990); doi: 10.1117/12.22161; https://doi.org/10.1117/12.22161