Let's talk about near-eye technology, the key to understanding how augmented reality (AR) headsets work. To get a handle on why this field is so vast and intriguing, we need to take a step back and talk about some core ideas with respect to technological development.

If you were to be teleported back to the 16th or 17th century into a cornfield, you'd have no idea what you were looking at. Corn stalks used to be planted many feet apart, as they were unable to support their own weight. This means they sagged onto the ground, lying almost flat.

So instead of nice, neat rows of lush green leaves, you'd be looking at thousands of humps of limp green and yellow plants – almost like poorly watered vines – against a backdrop of mostly brown.

There was a fundamental limitation to the ability to grow corn – and, before the 19th century, more or less any plant – in abundance. That limitation was the strength of the stalk. But scientists overcame this fundamental limitation through research, development and patience. They eventually developed genetic-splicing and cross-pollination techniques that allow for the tightly packed cornfields we see in places like Nebraska and Illinois today.

Why do we care about this, if we're talking about near-eye technology and augmented reality?

There is a fundamental limitation to the human eye that is currently being overcome with fascinating technology today – and it's opening up a large range of possibilities.

The human eye has a range of about thirty degrees to its peripheral. Outside of that, one can only "sense" objects, as opposed to making out details. In "regular" reality, this poses few threats to our understanding of information input. But in things like virtual reality (VR) and AR, this poses a problem.

Glasses have an angle wider than thirty degrees. In fact, many glasses get close to 180. This is a problem, as the difference between what you can see and what is in front of your eye is about 150 degrees. (This is admittedly an oversimplification, but you didn't click on this article to get into the intricacies of optical theory, did you?)

To be clear, in assisted reality (aR) this isn't much of a problem. aR devices simply give access to information – the information doesn't have to respond to the user's environment. This means a set of aR glasses can simply display a screen that adjusts to your eyes by adjusting to the 150-degree difference in a linear fashion.

But this used to cause all kinds of problems in augmented reality, as the angle you're using within the 30-degree range is constantly changing.

A swathe of technical solutions has been discovered in the last 30 years to overcome this problem.

In short, there are a few ways to get a virtual environment overlaid on a set of glasses. For the sake of your sanity – and because you can go on your own YouTube deep dive later – we'll look at the five major players in the industry.

Incoupling

Incoupling refers to a technique that allows one set of lenses to be embedded in another. If you watch the video below, you'll see a small lens inside the larger lens worn by the occupant, which then allows the image to be overlaid onto the surrounding environment.