> Stereoscopic images are only part of the whole picture (pun intended).
They're actually pretty much the whole of the picture.
> One is the act of focusing the eye for the correct distance
That is a very short-term effect, if it happens at all. This is why contact lenses are often prescribed for monovision as people get older - the eye adapts *very* rapidly to changes from "the norm" in terms of focussing. This is why you can put on a pair of glasses with only very temporary disturbance to distance estimation, even if the prescription is really quite strong...
> the other is that each eye moves to focus the object of interest on the center of the retina
And, by positioning each entity within the image, the angle between the eyes is set for that entity, thus creating the 3D view. That is exactly how stereoscopic vision works - and it matters not whether the image is real or synthetic. The eye moves to place the object correctly...
> If you just use separate images beamed into each eye, you can have the
> correct image for an object close to you
You can also have the correct images for an object far away from you.
Here's an experiment to show you how it works: pick an object - any object, at the distance of your choosing. Can you see it in 3D? Good. You're now interpreting that 3D image according to two images - one in each eye. It really is that simple.
> Try to focus on both hands at the same time.
That has nothing whatsoever to do with 3D vision. It is how the human vision system ignores items in the vision path. And it's a temporary effect - wait a while, and you can focus on both.
> Don't do this for too long, or else you will get dizzy
Nope. Do this for a long time, and you acclimatise to it.
> You will see that they go slightly 'cross-eyed'
That's how stereoscopic vision works. The angle between the eyes is used as a reference. That angle is set by correlating the two images, and it happens whether the images are real or synthetic. It's also the reason why aliasing causes strange effects - which is why Ford Escort headliners used to look so odd, and why random dot autostereograms work.
> Stereoscopic vision together with both of these other effects are required
> for the brain to correctly determine depth
Absolutely untrue. Eyeline angle is an *effect* of stereoscopic images, and focussing is a feedback loop - it alters over time.
> If you only get one of them, some people can ignore the fact that the others are missing
Anyone looking at something with two working eyes is using sterescopic vision. That is the beginning and end of it. Look up the term if you don't believe me - it's "stereoscopic vision". Everything else you say implies some deep-seated misconception about how human (and most animal) vision works. But don't take my word for it - look it up. You will see that the separate images are all that is necessary.
> the current 3D TV cannot do this
It's a good job I wasn't talking about 3D TVs, then, isn't it? I'm talking about stereoscopic vision - the sort I'm using right now to look around me - which isn't reliant on any display technology. .