MiniPOV and saccade displays?

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whoa
 
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MiniPOV and saccade displays?

Post by whoa »

Hey,

I searched around a bit and was surprised not to see this one discussed...

Any experieinces or any prospect of using the MiniPOV platform to create saccade displays?

http://www.star.t.u-tokyo.ac.jp/~junji/ ... /index.htm

Thanks for any advice,

Mark

sparr
 
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Re: MiniPOV and saccade displays?

Post by sparr »

The only difference in a saccade and a typical POV implementation is what moves (the eye or the LEDs). The issue with saccade displays is not with the POV setup, anything like the minipov or spokepov would work. The major hurdle is convincing a human's eyes to travel appropriately. There are ways to do this, such as specific visual stimulus, but that is a major undertaking to research and exploit.

whoa
 
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Re: MiniPOV and saccade displays?

Post by whoa »

It seems that a mid-sized saccade lasts about 50ms. I assume that rate of column change-over and gaps between display flashes is easily adjusted in MiniPOV software?

As for prompting saccades, that might be unimportant. For instance, SF's Exploratorium at one point had a large saccade display high in the rafters of a very large, long hall. No particular prompting was needed to guarantee that a lot of people would just randomly get the image flashed during a relevant saccade. The effect was surprising and cool, like discovering a secret.

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Seamus
 
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Re: MiniPOV and saccade displays?

Post by Seamus »

If I recall correctly (my visit was a long time ago), they had an exhibit set up in/near the center of the building, with small mirrored columns mounted on lazy-suzan bearings. By spinning the mirrors, your reflected view scanned past the saccade array and you saw the image clearly in your persistence of vision. Each image was displayed several times in succession, and they changed every few seconds or so. A display explained what you were seeing, how it worked, etc.

SteveBaker
 
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Re: MiniPOV and saccade displays?

Post by SteveBaker »

I think we can do better than "You'll have to experiment". The science behind this is very well known and understood.

The principle is very simple - you have a vertical column of LED's (could be just one color - could be multicolor) and you take some kind of a small image and display vertical stripes of the image in quick succession followed by a long-ish pause.

As the eye just happens to pan past the strip - the image is played out into the eye via persistance of vision. The area where the display is situated has to be fairly dark - or it doesn't work. They have the annoying/interesting property that people notice them - and then stare at where the image was in an effort to see it again...which of course stops it from working!

According to Wikipedia - there are two types of eye motion that can do this. One is just when your eye is switching from looking at one thing to looking at something else. The other is that even when you are staring fixedly at something, your eye twitches back and forth between 30 and 70 times a second - through an angle of about 20 arc-seconds. This latter thing is a way for the eye/brain to increase the spatial resolution of the retina...but because of that, the distance that the saccade travels isn't enough to produce an image that's bigger than one "pixel" on your retina.

So this must be talking about the saccade that happens when you simply switch from looking at one thing to looking at something else. You could probably make that happen "on demand" by having two conventional displays - one on each side of the saccade display and switch from showing pictures on one to showing pictures on the other. Every time you do that, most people are going to shift their gaze - and they'll see the saccade display happen.

That's an elegant way to present it because you end up somewhat in control of which direction the eye is moving. If you don't have that control then you can't display text because there would be a 50/50 chance of the person glimpsing a mirror-image of your text.

To make this work - you'd want to read http://en.wikipedia.org/wiki/Saccade - and pay careful attention to what it says under "Timing and Kinematics". Using some kind of a distraction to make people switch gaze "on command" you could control the angle their eyes sweep through - and thereby control the speed. Knowing the "initiation time" would give you the ability to position the image in space and time for optimum viewing.

It looks like you'd want to keep them looking (say) to the left of your display - then suddenly distract them with something new on the right. If you arrange that their eyes have to travel about 20 degrees to get from one to the other (you can't make it too much or they'll turn their heads too - and that'll mess things up) - then we'd expect (according to Wikipedia) a 200ms delay - followed by eye movement at maybe 400 degrees per second. If you put your display in the middle (between the two distractions) then you could display the image over a period of (say) 1/80th of a second - which is well within the 'persistance of vision' limits of around 1/60th second - and it would cover 5 degrees of their field of view...which ought to be pretty good.

Of course if you don't arrange distractions and such to try to make them switch their gaze - then it's going to be pretty random whether they actually see it or not.

Using multicolored LED's with PWM control of brightness - you could probably produce a pretty nifty full-color image! Of course changing a lot of LED's that quickly would be a challenge - but if you used one Ardino output per LED, you could write to the entire column with just a few instructions - so the vertical resolution of your picture would probably suck - but the horizontal resolution could be fairly detailed...good for a text display!

Good luck!

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Franklin97355
 
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Re: MiniPOV and saccade displays?

Post by Franklin97355 »

Take a look at some of these. http://www.subliminaryartworks.com/

SteveBaker
 
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Re: MiniPOV and saccade displays?

Post by SteveBaker »

Clever! The scrolling green title has a hidden stationary message that only appears if you scan your eyes across it at just the right rate and at just the right time from right to left. It's tough to see it though.

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