Temporal light interference

The magnitude, shape, periodicity and frequency of the TLM depends on many factors such as the type of light source, the electrical mains-supply frequency, the driver or ballast technology and type of light regulation technology applied (e.g. pulse-width modulation).

Furthermore, external factors such as incompatibility with dimmers or presence of mains-supply voltage fluctuations (power-line flicker) play a role and may cause additional temporal light modulations.

Various pulse modulation techniques and data rates can be applied depending on the function of the VLC system.

[2] VLC systems generally apply specific coding and modulation techniques to achieve robustness against common TLM disturbances.

TLMs from lighting equipment located in the neighbourhood where barcode scanners are applied can cause TLI.

[3] Recordings of slow-motion cameras in environments with temporal light modulations may induce artefacts on displays such as flickering or banding.

The European standard EN 12193 for sport lighting[4] specifies maximum levels of modulation depth (also called flicker factor FF) to obtain flicker-free pictures taken by high-speed cameras.

Figure 1: TLI tripyich: temporal light modulations that may interfere equipment.
Figure 1: TLI tripyich: temporal light modulations that may interfere equipment.