h a l f b a k e r yWhat was the question again?
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Escalators in public places should be lit by slow-flashing strobe lights (the proportion of the population in whom this will trigger epileptic fits is very small). The flashes could be timed so that the escalator has moved exactly one step position between each flash of the strobe, giving the impression
of a stationary escalator with people jerkily moving up a step at a time. If you then increase the strobe frequency very slightly, the escalator will appear to move backwards while the people jump forward a step at a time.
Background information
http://www.epilepsy...tosensitiveepilepsy
There's a suggestion that just looking at a moving escalator is enough to trigger photo-sensitive epilepsy so I'm unsure whether adding a strobe (which makes the escalator appear stationary, but is itself a bright flashing light) will increase or decrease the risk of an epileptic attack. [hippo, Nov 08 2010]
[link]
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I think that an escalator is actually too slow to strobe properly, and the periods of "dark" time between the flashes would therefore be quite long. Too long in fact to create the impression of a continuous motion "held" in a static position. |
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So speed up the escalator. |
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And use a more powerful flash tube so the image stays on your retina longer. |
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I have explained why it won't work. A more powerful light will make no difference. The whole principal of a strobe lies in the ratio of dark spaces between momentary flashes of light. |
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(again) - The dark spaces would be too long to create the sense of a static motion. It's therefore bad science, but I'm not a scientist (unlike others on this site who might like to comment/correct what I'm saying) |
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I'm pretty sure most shopping malls already do this. That's what that epileptic scraper at the end of an escalator is for. |
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The flicker-fusion rate actually *rises* with increasing
brightness, so you would need a *less* powerful
light. |
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I think I can conceive of a version of this thing
that would
work. |
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First, instead of an escalator, a moving sidewalk
("travelator"), such as is found in many airports. Next,
paint transverse stripes on the standing surface: choose a
spacing such that, given the speed of movement, and
some suitable strobe frequency, the surface appears to
stand still. You'll see people moving forward on an
apparently stationary surface. Detune the strobe a bit and
the
travelator appears to go backwards while the
passengers move forwards, or to go forwards at a different
speed from the passengers. |
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(One necessary detail is that the railings be transparent,
which, for esthetic reasons, they already are in some
airports.) |
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This reminds me of the "Blink" episode of Dr Who. In this episode, creepy statues try to kill people, but only move when no-one is looking at them. In one scene, a flickering light causes a stroboscopic effect, and you see the statues incrementally move towards the trapped prey. |
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[mouseposture] - the "flicker-fusion" thing is about trying to take discrete, disjoint images and combining them into a perceived continuous seamless image. |
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However, the escalator *is* moving in a continuous, seamless fashion; and the idea is to attempt to make it appear to be discrete jumps. |
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Yeah, I'm having second thoughts about the relevance of
flicker-fusion.
And I'm starting to think it *might* work if the aim were an
illusion of *discontinuous* motion of passengers and
*stationary* steps -- I suspect it would be one of those
illusions which can be seen in either of two ways. Would
the visual system assume independent motion of
passengers and steps, or would it assume a rigid
connection between each passenger and the step they
were standing on?
Not sure about the escalator-moving-backwards idea,
though. |
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Put the passengers in stagecoaches, so the wheels do that weird backwards thing they do in Westerns. |
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