Transparent Screen Selection
You can't do AR by simply placing a "transparent screen" over someone's eyes &mdash; the screen will be horribly out of focus.

There are two possible approaches that are commonly used:


Use a VR (non-transparent) display, but mix the image from your camera in with the picture elements generated by the augmentation software.
Use an optical beam splitter along with an ordinary non-transparent display. Between the display and the beam splitter, you have optics that cause the display to appear much farther away than it actually is, so that the user can focus on both the real world and the display at the same time.