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If someone has short or long sight, is it possible to tune image on a computer monitor in such way, that a person could see it sharp as if they were wearing glasses? If not, will 3d monitor make it possible?

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Let's take a simple original picture to look at - just two nearby dots on a white background. If you have bad vision, the dots look blurred.

The way good vision works is to ensure that all the light hitting any particular small area of your retina comes from the same direction in front of you. Conversely, all the light coming from one direction hits one specific spot on your retina.

When you have bad vision, the light from a locus of nearby directions all hits on the same part of your retina, and the light from a particular direction is smeared out over an area on your retina. Hence, blurred vision is an averaging effect. When you look at the dots, you'll see them smear out into each other.

You might try to compensate for this by making a "counter-blurred" image where the source dots are smaller, but if the original dots are close enough that light from the center of one dot is spilling over to overlap light from the center of the second dot, making the dots smaller won't fix that problem. Hence, the dots will always appear blurred. You can't create the impression that the original has for someone with good vision.

A photograph is really just a bunch of nearby dots, and so the same problem applies.

I don't know about the 3D monitor, though. I suppose if it can control the direction of light coming off it, it could be modified to focus the light some and create a sharp image for someone with blurred vision.

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+1 .. and I thought it should be possible using deconvolution (thinking: blurring is just a convolution in the mathematical sense).. and then I read this (fake) paper ;) artis.imag.fr/Membres/Adrien.Bousseau/virtual_glasses/… –  Approximist Apr 11 '11 at 9:52
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Just a note about the 3D monitor. A 3D monitor cannot control the direction of light coming off of it (the phase). It simply presents two images at the same time, one for each eye, so that your brain re-creates a 3D effect. Now, if we had a holographic monitor, that would be a different story. A holographic monitor would require no 3D goggles, and would actually let you walk around the screen to see the scene from different angles, simultaneously. –  Colin K Apr 11 '11 at 14:45
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Not on regular monitor screen. The technology necessary to achieve such effect would be holographic display, holographic in the sense of wavefront synthesis. Although this device would be a 3D display, not all 3D display are holographic. You would need technologies such as spatial light modulator. Which only exists as low specs laboratory devices.

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The light source with this properties exists in technology named "Adaptive Optics".

So the answer is yes, if your monitor (not existing on market yet) has controllable phase source for each pixel on screen (like phased array antenna), and even more. Each pixel actually needs multiples of phase values, depending on angle of look. So for megapixel display you may need gigapixel of phasing elements which follow and compensate phase exactly to errors on the ray trace to location of retina cell of each individual eyeball, looking at screen.

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No, if you are someone who needs glasses the effect without them would be like a blur effect which can not be reversed the same strongly blurred picture can not be rendered to its original detailed focus.

Taking a picture without focusing the lens would have the same effect. You can neither create an image that will be sharp with an unfocused lens nor reconstruct the detailed image taken with an unfocused lens.

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This is a cold thread, but I think some of the answers are off base. Blurring of an incoherent image can be mathematically represented as a convolution, and if the blurring kernel is known and is invertible (no spectral zeros) then a deconvolution filter can be developed. Mathematically it does not matter the order in which the two linear filters are applied, so you could apply the deconvolution filter first. The problem is that a real image cannot have negative intensities, whereas the pre-deconvolved image is not guaranteed to be positive. One would have to bias the image upwards to preserve positivity. Then the observer would see a sharp image it would appear whitewashed.

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Well, I think that it is possible to create a "blurred" image from a real one in order to be correct for someone with short/long sight.

It is "only" an optical problem, and, as long as we can apply the paraxial approximation, it is a linear system, very suitable to a computer program. We know the laws that focus the rays in one point, so we can disturb these rays so that they arrive at a different point, and it would be possible to "tune" this point to be correct to every people.

I think that the point is that, from a correct and well-defined image, we can do a lot of things with it. If we have a blurred image, and we want to make it correct, it will be more difficult, because now we haven't got all the information as in the first case.

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Unfortunately, it's not just more difficult, it's impossible. The information you need is the phase. (Which is equivalent to @Mark Eichenlaub's mention of the 3-D monitor that "can control the direction of the light coming off it" -- even though I have no idea what a 3-D monitor does ;-) –  ptomato Nov 12 '10 at 23:40
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Consider the system: monitor -> eyeglasses -> eye. Assuming these are the correct glasses, the monitor is clearly in focus. Now move the eyeglasses towards the monitor, transforming them as necessary to keep the optical path the same. For that person, I'd argue the monitor remains sharply focused.

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protected by Qmechanic Mar 3 '13 at 20:58

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