Strip of LEDs turn into a poster when you turn your head - where?
Erlend
Posts: 612
Some time ago I remember reading about the idea to strobe a strip if LEDs such that when you turned your head/eyes sideways a 'phantom' picture would emerge. Same principle as when a dotted line appears when you do the same looking at LED braking lights.
Anyone know a link to such a project - or product?
Erlend
Anyone know a link to such a project - or product?
Erlend
Comments
Erlend
Trick on these is a higher refresh rate on the order of hundreds of Hz to low Khz.
The size and shape integrity is poor, but when big, simple details are present, they are seen easily.
You don't happen to have a link to an article - or what name they go by? "LED strips" obviously return a lot of Christmas decoration...
Erlend
http://forums.parallax.com/discussion/103500/persistence-of-vision-led-text-display-and-my-failure-to-find-it
It worked best when they moved it. It worked for ones own eye movement, but as Rjo mentioned in the old thread, these vary.
I did some tinkering afterword. Dark room, glancing between two points. You can get the approximate refresh rates needed for you and likely similar others by glancing to and fro. Increase it, and what appears as discrete dots slowly becomes a bright smudge.
You want less than the smudge.
Short, but super bright duty cycle helps with image discrimination.
What I noted was the brain seems to have two basic modes.
When the eye is still, the POV image will basically add to what is seen. We've all seen that. The artifacts are clear and can endure a while, until the eye moves. Walk up to some one and wave it across their point of focus. They will see a lot of it, until they glance about, and it's gone quick.
When the eye moves, artifacts break down into two types.
One, I'll call the smudge type, seems to get filtered aggressively. If you fixate on your general field of vision, pull attention away from the center, and move your eyes, these are seen and fade rapidly, unless very seriously bright. Those levels of brightness leave artifacts that endure for a while. (Think sunlight on shiny car metal midday bright)
Some people can relax, blur the eyes, and sort of lose focus. That, plus a side to side eye move works best.
Refresh that is too high results in this. Image perception is poor. It's all just a smear.
The other type is seen as a series of atomic images. These tend to endure a lot longer and do not get as much filtering.
I don't know the why, just what I have observed.
You can see an example of the former in a dark room with a light source that is constant. Or very high refresh to be constant.
One of the best examples of the latter is on the freeway at night. Many cars employ just the wrong kind of LED refresh. It's super bright, low on duty cycle. A side to side glance can leave your vision speckled with red dots, really notable when they are braking.
Someone ought to study this. For me, the impact is sometimes profound, fatiguing and a major distraction. High refresh or constant lights get processed better, faster, maybe as one image. We mostly don't notice. I don't, but I noticed the bright tail light LEDs with that bright, short duty cycle right away.
For me personally, as a reference, a 60hz source, low percentage duty cycle, on a full eye swing, right to left, say, appears on the order of 10 to 30 or more to 1, where the 1 is a "pixel" seen, the rest distance between pixels expressed in pixels.
On a much less aggressive motion, say 30 degrees, that same source might be from 3 to maybe 10 to 1.
Another thing I found interesting is when one takes a single source, and looks around it in many directions, but not at it, circles around it maybe, or random, try to be jerky moves, the resulting artifacts are generally smooth curves, connected. This image detail is seen in the visual field for a little while.
When it's dark, where there isn't much in the field, details can be seen well outside the center of vision.
When it's bright, most of that is lost and lost very quickly. Details are fleeting, largely central vision only.
The outer vision, not central, appears to run faster and is far less color sensitive, as well as far less prone to artifacts that can endure.
My conclusion was people would need to learn to see these things as stable, fleeting images with their practiced eye movements.
Given they encounter one, I also feel a few glances, playfully done would see that person find a sweet spot fairly quickly.
A small, bright image might be generally successful in a wider range of lighting given image targets to glance at. Like emoticons maybe tops.
In darkness a larger image is plausible.
Where there is more light overall, the source is gonna have to be really bright, and image small, due to the very rapid fade outside central vision.
I did not have a multicolor source. I suspect some colors are going to be a lot better than others. The toy I saw used red LEDs. I tinkered with red myself too.
One more thing. Blue, with no other color component present will be just terrible.
We have a fraction of the blue sensitive cells that we do others, and they are sort of scattered about, effective resolution poor.
This stuff will sort of work, but images will be suggestive at best, unless blue is actually blue and white together, so bright blue, low saturation, not just a super intense blue. We need both for the brain to sort out any real detail from pure blue sources.
If I can find the toy, or a reference beyond these things I remember, I will post here.
It was some overseas thing, had a handle with batteries and a row of closely packed LEDs. It cycled through a few images. Wave it, one shows up. Wave it again, another one, or part of one, etc....
It was like that toy, but more barrel shaped. Nice find!
Erlend