LEDs are typically controlled with a discrete on–off PWM signal,
in which the on-time (duty cycle) is in theory linearly proportional
to the light output. More detailed discussion on the advantages
of LEDs over traditional light sources can be found in regard to the
noise and stability characteristics (Brophy, 1967; Rumyantsev et al.,
2004; Salzberg et al., 2005), and to biological applications such as
in widefield microscopy (Holman, 2007) and visual neuroscience
(da Silva Pinto et al., 2011).