Yeah I always wanted to be able to do that too, but I don’t think it’s going to be easy. Sensors in the back of your eyes send a signal to our brain, basically using chemistry, and then the brain interprets the information it got and we “see” a picture in our mind. To invent some kind of way that a computer could interpret the information and get a picture out would be very hard, I’d say impossible for now since people are still trying to figure out how the brain works.
Google glasses are taking the first step in a slightly different direction, which is along the lines of your contact lens idea, these will probably be pretty normal in a few years. The next logical step is indeed to take the same idea and put it in a contact lens, and I’d guess that there’s a good chance that these will exist in the next decade or so. Maybe a little longer, like how do you get a battery into something you put in your eye?!
I see what you mean about the battery thing, I didn’t really think of the practicality! I also understand what you mean when you say that we still don’t fully understand the brain but I still think the idea is pretty cool! @grantkennedy