h a l f b a k e r y"More like a cross between an onion, a golf ball, and a roman multi-tiered arched aquaduct."
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Nearsightedness comes from the eye being too long from front to back, so the focal point of the lens is in front of the retina, where it should be. This makes every point turn into a circle of light by the time it hits the retina. The circles overlap, producing blur.
Couldn't a TV or computer
monitor take this into account and correct for it? Instead of displaying the true image, the TV would display a pattern that produces the true image on the retina.
The pattern would pass through the lens and create circles that, when combined, produce the true image. This is related to coarse coding of receptors in vision, as opposed to sparse coding. Coarse coding allows for greater resolution with the same number of receptors. The question is whether this is true in the reverse case, with displays. Is it possible to get, using coarse-coded circles on the retina, the same resolution that the true image has?
If so, the computer would just have to calculate the correct pattern to display. This would come from the person's glasses prescription. In fact, the display device could just have a focus knob that you could adjust until it was clear to you.
Vision-correcting display
http://www.scienced...07/140729152921.htm
Researchers are developing vision-correcting displays that can compensate for a viewer's visual impairments to create sharp images without the need for glasses or contact lenses [xaviergisz, Jul 30 2014]
False_20arms_20for_20the_20short-sighted
[not_morrison_rm, Jul 30 2014]
[link]
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Whoa--did you just completely change your idea? |
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I'd still need my glasses for the very frequent occaisions when I need to show my co-workers stuff that's on my screen. |
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I changed it slightly soon after posting it, but nothing major. Are you thinking of the CD thing? |
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I thought someone had posted this recently - I thought it was [neilp] but I can't find it... |
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This is not even theoretically possible. To see why, consider an image with a single white pixel in the center of the screen surrounded by black. It will create a disc of white on the retina of the viewer if they are nearsighted. There is no value that the other pixels on the screen could assume to counteract that effect, because they would have to essentially subtract away light instead of add to it. I'm fairly certain this general effect would make it impossible for any kind of image processing to "correct" the image in the way that you have outlined. It might work if you were willing to permit a considerable reduction in the perceived contrast range of the picture, but I'll have to think about that some more... |
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Years ago I worked with someone who was visually impaired and they used a device that did this -- I can't remember if this was hardware or software, we're talking mid 80s. |
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You might be able to accomplish this with a huge, adjustable lens in front of the screen, allowing you to focus the image like binoculars do. But your head would need to be held stationary in relation to it.... Maybe you could use smaller lenses mounted on a piece of headgear-- wait that's eyeglasses. |
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I think it might be dead in the water after [pawebb]'s comment. I could see having a red pixel, a green pixel, and a blue pixel summing to white at a single point, but then you'd also have red, green, and blue all over the retina, and as [pawebb] pointed out, you can't subtract light. The basic problem is that light always wins over dark, so you can't use dark pixels to erase anything. |
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Yep, pawebb has it right. If you make the image blurry (to a normal person) by placing a lens in front of the screen (creating a focused virtual image at a location different than the actual screen) then this might work. Blurring an image will just make the image on the retina a blurrier version of an already blurred image. Sorry, won't work. |
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There still might be enhancements that could be applied to make the picture appear sharper to someone with imperfect vision. The sharpness control on most television is a very basic way of doing this. It increases the local contrast of an image near edges, making them stand out more prominently. |
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My camcorder display has this. |
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Maybe you could cover the screen with a large,
flexible lens filled with clear magnetic fluid. The
webcam could monitor the user's eyes and use
magnetic fields to move the fluid, shifting the focus
of the lens to adjust for head and eye position. |
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Ceci n'est pas a readable idea. Font too small. |
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