Time-of-flight range imaging sensors acquire an image of a scene, where in addition to standard intensity information,
the range (or distance) is also measured concurrently by each pixel. Range is measured using a correlation technique,
where an amplitude modulated light source illuminates the scene and the reflected light is sampled by a gain modulated
image sensor. Typically the illumination source and image sensor are amplitude modulated with square waves, leading to
a range measurement linearity error caused by aliased harmonic components within the correlation waveform. A simple
method to improve measurement linearity by reducing the duty cycle of the illumination waveform to suppress
problematic aliased harmonic components is demonstrated. If the total optical power is kept constant, the measured
correlation waveform amplitude also increases at these reduced illumination duty cycles.
Measurement performance is evaluated over a range of illumination duty cycles, both for a standard range imaging
camera configuration, and also using a more complicated phase encoding method that is designed to cancel aliased
harmonics during the sampling process. The standard configuration benefits from improved measurement linearity for
illumination duty cycles around 30%, while the measured amplitude, hence range precision, is increased for both
methods as the duty cycle is reduced below 50% (while maintaining constant optical power).