Lighting Industry, Research

The Latest On Temporal Light Modulation (TLM) / Flicker

The Latest On Temporal Light Modulation (TLM) / Flicker

The American Lighting Association Engineering Committee recently received a presentation from the “Flicker Queen,” researcher Naomi Miller, at Pacific Northwest National Laboratory (PNNL). Ms. Miller provided a summary of her latest research at PNNL on temporal light modulation (TLM), more commonly known as flicker.

She and PNNL colleagues completed a human subjects study on the visibility of two forms of flicker: the stroboscopic and the phantom array effects. That study showed clear response differences between the two and was able to identify TLM-sensitive subjects who are more likely to experience headaches, migraines, nausea, or other negative responses from TLM. The results have been submitted to a journal for review, and it is hoped will lead to a metric that will help identify and mitigate problematic TLM.

During her presentation, Ms. Miller made the following recommendations to reduce TLM / flicker:

  • Combine PWM with CCR and PFM to reduce luminance
  • If you MUST use PWM, raise the frequency above 20,000 Hz
  • Use sign waves instead of rectangular waves
  • Reduce modulation depths
  • Increase duty cycles (90% is usually okay, <10% is usually terrible)
  • Avoid AC LEDs unless they have significant board-mounted capacitors.

Ms. Miller’s most recent publication is What the Flicker Is Going on Here? Temporal Light Modulation in Automotive Lighting, an SAE technical paper. (Miller, N., and Irvin, L., “What the Flicker Is Going on Here? Temporal Light Modulation in Automotive Lighting,” SAE Technical Paper 2024-01-2462, 2024,

Other industry activity around flicker is occurring. The IES has drafted a new standard, TM-39: Quantification and Specification of Flicker. The IES Vision Science Committee reviewed the draft and approved the document. Soon, TM-39 will be made available for public review, to be announced in the IES IGNITE Bulletin and posted on the IES website. A review copy will cost $25. Additionally, the IES LM-90 Committee will be working on updating their measurement guidelines. LightNOW plans to announce when final versions of TM-39 and LM-90 are published.

Are you aware of other industry activity around TLM / flicker? Email me at

Image: CIE


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David Shiller
David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.


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