ASSIST Releases Publication on LED Light Source Flicker
August 14, 2012 - 9:32am
Studies led to development of calculations that provide estimations of the detection and acceptability of light source flicker for a given frequency and percent flicker.

The Alliance for Solid-State Illumination Systems and Technologies (ASSIST) released a new publication that addresses the issue of LED light source flicker. The publication, ASSIST recommends… Flicker parameters for reducing stroboscopic effects from solid-state lighting systems, provides calculation methods for estimating the detectability and acceptability of stroboscopic effects from flicker using the parameters of frequency and percent flicker. The calculation methods are based on Lighting Research Center (LRC) work published last year in Lighting Research & Technology journal.

Flicker and stroboscopic effects have been a concern with solid-state lighting (SSL), and industry and the ENERGY STAR program have debated the effects of frequency and other driving modes on the perception and acceptability of flicker. To provide further data and guidance in this area, ASSIST funded human factors studies of indirect flicker perception. The studies, led by LRC senior research scientist John Bullough, were designed to determine what light source parameters affect the detection of flicker and stroboscopic effects, and to assess subjective responses to flicker in terms of acceptance and comfort. Previous research had shown at what frequencies direct flicker is perceptible but did not identify thresholds and acceptance levels for indirect perception, nor a means of predicting these levels for SSL.

The results from these studies suggest that there is a tradeoff between the frequency and the modulation depth in the detection and acceptability of indirect flicker. Follow-up studies systematically evaluated this tradeoff and looked more closely at the relationship between frequency and percent flicker. The conclusions drawn from these studies led to the development of the calculation methods detailed in the ASSIST recommends publication, which provides estimations of the detection and acceptability of light source flicker for a given frequency and percent flicker.

Nadarajah Narendran, LRC director of research and organizer of the ASSIST program, notes that the methods offered can be used easily by LED lighting manufacturers to develop systems that minimize the effects of flicker. “For the past 10 years, the LRC and ASSIST’s industry members have investigated the technical problems impeding market acceptance of LED lighting. This is one example of the work that ASSIST is doing to provide the industry with solutions that can be implemented quickly and effectively,” said Dr. Narendran.

The ASSIST recommends publication is available on the ASSIST website at The published studies leading to the ASSIST recommendation can be found online. The first paper, “Effects of flicker characteristics from solid-state lighting on detection, acceptability and comfort,” was published last year in volume 43, issue 3, of Lighting Research and Technology. The second paper, “Detection and acceptability of stroboscopic effects from flicker,” is published in the online early access section of the same journal.


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