Technical Paper
What the Flicker is going on here? Temporal Light Modulation in Automotive Lighting
2024-04-09
2024-01-2462
An unintended consequence of interior and exterior automotive lighting’s shift to pulse width modulation (PWM)-driven LEDs is the introduction of temporal light modulation (TLM), or “flicker”, to our roadways. TLM occurs when the output of a light source modulates over time, and there are three resulting visual effects: direct flicker, the stroboscopic effect, and the phantom array effect (PAE, also called the “beads” effect). The PAE is particularly relevant to automotive lighting. It is an effect of repeating dots, dashes, or parallel lines on the retina resulting from an interaction of the modulating light source and the observer’s normal eye saccades. It can be detected from ~80 to ~15,000 Hz (and occasionally higher) with peak visibility between 500 and 1000 Hz. Depending on the frequency, depth of modulation, and duty cycle, TLM can have serious effects (both visual and non-visual) on drivers and pedestrians ranging from distraction to nausea and disorientation.