Focus correcting screen

Question

With the rapid approach of VR, and being someone who's always needed glasses! I have been curious about this for a while.

Is it possible to correct the focus of a lens by adjusting the image on a screen. So at present the image is distorted because althought it is perfect on the screen, the intermediate lens (i.e. the one in my eye!) is faulty. Would it be possible to change the screen image to compensate for that lens.

My intuition tells me it isn't because everything is x distance away, but it would be good to get an actual scientific reason for this, and maybe what it would take to make that work (if it is / would be at all possible)

@KyleKanos I actually didn't know that existed! It may do (the different perspective would be interesting) but equally, I'm curious of how this works purely from a physics angle too. — Michael B, Mar 15 '16 at 12:20
TBH, I don't see much physics here. At best, you could say yes because glasses exist; but whether it can be done is an engineering question (or maybe a programming question, since it is a video or game). — Kyle Kanos, Mar 15 '16 at 12:23
@KyleKanos I suppose ultimately the question is can an (2d?) image (whether a screen, a photo etc) be adjusted in such a way that it brought into focus by an intermediate lens. The engineering question might be how to implement it, but first the physics question of why / how it would (/wouldn't) work needs to be understood. That's the one I'm interested in. — Michael B, Mar 15 '16 at 12:29
The answers is that it depends on your screen. A normal 2d screen can not do this, but a (true) holographic screen could. In the latter case the image would appear sharp to you and blurry for people who don't have your prescription strength glasses. You can simulate this by putting on someone else's glasses... it's especially fascinating with glasses that correct high astigmatism... no matter how close one gets to an object, the blur never goes away! — CuriousOne, Mar 15 '16 at 23:38
Possible duplicate of Is it possible to blur an image in such way that a person with sight problems could see it sharp? — , Mar 16 '16 at 07:07
I apologize for the close message -- this is definitely not engineering. It is however a duplicate of the above linked question. Unfortunately the system just goes with what a majority said (in this case, "engineering") and pretends everyone was unanimous in that. — , Mar 16 '16 at 07:08

score 1 · Accepted Answer · answered Mar 15 '16 at 14:34

(image copied with permission from A Framework for Aberration Compensated Displays, by Fu-Chung Huang and Brian A. Barsky)

I looked into this once ... The answer is "Yes!" At least to some extent anyway.

If you know someone's exact vision impairment, and you know the exact distance between their eyes and the screen, then you can warp the display on the screen to compensate for their vision impairment.

...But it won't be perfect -- it will still be a bit blurry. And you have to sacrifice image contrast.

In other words, you can create a funny-looking black-and-white pattern which, through impaired vision, looks like a less-blurry image. That image will not be black-and-white though. It will be "darker-gray-on-lighter-gray". (That's what I mean by "sacrificing image contrast".)

You can learn more about this topic by reading papers like these:

Pre-compensation for high-order aberrations of the human eye using on-screen image deconvolution

A Framework for Aberration Compensated Displays

There is ongoing research to make these systems work even better. Very cool.

That is pretty spectacular! and very much answers that 'surely it must be possible...' ponder that occurred in the back of my mind. As someone with a 'low order aberration' it is pretty exciting to think that this sort of thing is in the works already! Thank you for a great answer. — Michael B, Mar 15 '16 at 14:52

score 0 · Answer 2 · answered Mar 15 '16 at 14:16

You can produce a real image, i.e. an image on some physical medium like a screen, that is out-of-focus, but you cannot use any optical system to produce a focussed version of that image on your retina. The reason is that you lose all phase information when generating the real image. Now, what should be available in any VR system is a perfectly focussed image which is then relayed (i.e. with a lens) to a focal plane at some specified distance. By adjusting the lens system, you can essentially add your eyeglasses prescription to the VR default focal length.

There is another way to generate an image on your retina: use scanning light sources to "write" the image directly. Again, intermediate optics can set the focal distance for such a system.

I don't know which of these approaches current VR goggles use.

Focus correcting screen

2 Answers2