Defocusing the eye and computer monitors Im not sure whether this is the right site to post this on, but here goes :
We are often told to relax our eyes when using computer/tv screens for extended periods of time. I often find that I forget to do this. In view of this, I was thinking if it would be possible to periodically display something on the screen to encourage the eye to focus at infinity.
I assume that the eyes are focused on the plane of the monitor screen during normal operation. However, would it be possible to blur the view on the screen in just the right way so as it would precisely simulate light that would come from an much larger (imaginary) screen placed further away. Is this possible?
My hunch is that this isn't possible, but I cant really articulate why. However, I am also thinking of the case of those 'magic eye' images, that encourage you to defocus the eye to a focal length different from the plane of the picture.
P.S. Im interested in the optical physics here not the technical engineering, hence the post here...
 A: It is not possible. Let's say you could voluntarily focus at infinity, then every pixel displayed on the screen is not seen as a "point" (for this argument we can assume pixels are points), but as a blurred object. So what you see is all these blurred points overlapping each other. If you display a blurred picture, and your eye additionally blurs it again, you can not attain a sharp image. So it is for the simple reason that blurring twice will never give a sharp image.
Additionally, even if this was possible, it would still be strenuous on the eye, because the eyes get part of the information on where to focus from the offset between left and right eye. This is also why 3D-movies cause some people's eyes to hurt.
A: One may be able display something blurred, such that the viewer has to focus on it by moving away from the screen. But who would like to keep moving back and forth? Moreover, I don't think that is practically possible.
Continuous bright rays of light from the screens cause a high level of strain on our eyes. Hence, it's best to look outside the window at regular intervals and focus on something far away. The best that can be done is to remind the viewer at regular intervals to focus at a distant object. Other than this, I don't think there is any possible way out.
