Discovery of ways to optimize light sources for vision could lead to billions of dollars in energy savings

November 15, 2012

Vision researchers at Barrow Neurological Institute have made a groundbreaking discovery into the optimization of light sources to human vision. By tuning lighting devices to work more efficiently with the human brain the researchers believe billions of dollars in energy costs could be saved.

The research was conducted by Stephen Macknik, PhD, of Barrow's Laboratory of Behavioral Neurophysiology, and Susana Martinez-Conde, PhD, of Barrow's Laboratory of Visual Neuroscience. The study is published . The paper, titled "Optimizing the temporal dynamics of light to ," is believed to be the first attempt to tune light-emitting devices to the optimal temporal dynamics of the human visual system.

The discovery concerns the way humans perceive temporal modulations of light. For example, most light-emitting devices, such as , video monitors and televisions, flicker. Faster flicker rates result in reduced perception of flicker, which is more comfortable to viewers. In studying this phenomenon in the brain, the researchers discovered that there is a range of flicker dynamics of light that optimizes the perceived brightness of the light without increasing power.

"We found a temporal sweet spot in that can be exploited to obtain significant savings by redesigning light emitting devices to flicker with optimal dynamics to activate visual system neurons in the human brain," says Dr. Macknik.

The researchers estimate that if every light-emitting device in the U.S. – from light bulbs to cell phones – operated at for the human visual system, it could result in billions of dollars of savings in electricity and power.

To come to their conclusion, the researchers conducted experiments into two contradictory theories of temporal visual perception, or how bright a light appears. Bloch's Law states that the perceived contrast of a increases with its duration, but eventually plateaus at approximately 100 milliseconds. For example, a 5-millisecond flash will appear half as bright as a 10-millisecond flash, but a 200-millisecond flash will be just as bright as one of 400 milliseconds. The Broca-Sulzer Effect, on the other hand, states that perceived contrast increases with duration initially, but then peaks and falls again.

The researchers discovered that the discrepancy between Bloch's Law and the Broca-Sulzer Effect is caused by an intrinsic bias among experiment subjects, leading to dramatically skewed data. By improving their experimental design to overcome this bias, something that has never been before reported or intentionally controlled for, the results demonstrated that temporal vision actually follows the Broca-Sulzer Effect.

"Researchers have been studying temporal vision for more than 125 years, but because ours is the first experiment of its kind to control for all known forms of criteria, it is the first to accurately measure the role of temporal dynamics in brightness perception," says Dr. Macknik. "Thus, the power savings are ripe for the picking because we can adjust our lighting to flicker to take advantage of this peak in perception."

Explore further: Barrow researchers unravel illusion

More information: PNAS paper:

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4 / 5 (1) Nov 15, 2012
On the face of it, this looks like an easy way to save up to 50% of the energy consumption of lighting.

But a specific peak or trough in the perceived lighting necessarily coincides with some process in the brain. Now, all brain frequencies vary during the day, and this kind of lighting will lock the phase of some of them to the lighting.

This may have subtle long term effects, including changes in child brain development, disrupting the diurnal variation in brain processes, or mood control.

There was an article in Scientific American about a neurological study, where a baby cat was put in an environment where the light was from a 5Hz flash strobe only. Till the early adulthood the cat hadn't seen continuous light. It had learned to measure speed by the difference of position between flashes, and then in normal light it couldn't catch a mouse.

I'm not advocating fear of technology here, but I hope somebody (else than the inventors) study the effects.
not rated yet Nov 15, 2012
Great, but how much does it cost to optimize the flickering?
not rated yet Nov 16, 2012
Great, but how much does it cost to optimize the flickering?

If you use LED lighting then it's pretty minimal (and since there's already ideas for using the IR component of LED lights for information transmission then the components to get the flicker working would be already in there)

A caveat I would foresee is that different people might be susceptible to different flicker frequencies. Not every brain is the same. So we might get a solution where 95% of people save energy while 5% get headaches wherever they go.

At the very least some clinical studies should be done before putting such a system on the market.

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