While “Projection Based Augmented Reality” is a category in-itself, we are specifically referring to a miniature projector often found in a forward and outward-facing position on wearable augmented reality headsets. The projector can essentially turn any surface into an interactive environment. As mentioned above, the information taken in by the cameras used to examine the surrounding world, is processed and then projected onto a surface in front of the user; which could be a wrist, a wall, or even another person. The use of projection in augmented reality devices means that screen real estate will eventually become a lesser important component. In the future, you may not need an iPad to play an online game of chess because you will be able to play it on the tabletop in front of you.
Augmented reality devices are basically mini-supercomputers packed into tiny wearable devices. These devices require significant computer processing power and utilize many of the same components that our smartphones do. These components include a CPU, a GPU, flash memory, RAM, Bluetooth/Wifi microchip, global positioning system (GPS) microchip, and more. Advanced augmented reality devices, such as the Microsoft Hololens utilize an accelerometer (to measure the speed in which your head is moving), a gyroscope (to measure the tilt and orientation of your head), and a magnetometer (to function as a compass and figure out which direction your head is pointing) to provide for truly immersive experience.
Mirrors are used in augmented reality devices to assist with the way your eye views the virtual image. Some augmented reality devices may have “an array of many small curved mirrors” (as with the Magic Leap augmented reality device) and others may have a simple double-sided mirror with one surface reflecting incoming light to a side-mounted camera and the other surface reflecting light from a side-mounted display to the user’s eye. In the Microsoft Hololens, the use of “mirrors” involves see-through holographic lenses (Microsoft refers to them as waveguides) that use an optical projection system to beam holograms into your eyes. A so-called light engine, emits the light towards two separate lenses (one for each eye), which consists of three layers of glass of three different primary colors (blue, green, red). The light hits those layers and then enters the eye at specific angles, intensities and colors, producing a final holistic image on the eye’s retina. Regardless of method, all of these reflection paths have the same objective, which is to assist with image alignment to the user’s eye.
How Augmented Reality is Controlled
Augmented reality devices are often controlled either by touch a pad or voice commands. The touch pads are often somewhere on the device that is easily reachable. They work by sensing the pressure changes that occur when a user taps or swipes a specific spot. Voice commands work very similar to the way they do on our smartphones. A tiny microphone on the device will pick up your voice and then a microprocessor will interpret the commands. Voice commands, such as those on the Google Glass augmented reality device, are preprogrammed from a list of commands that you can use. On the Google Glass, nearly all of them start with “OK, Glass,” which alerts your glasses that a command is soon to follow. For example, “OK, Glass, take a picture” will send a command to the microprocessor to snap a photo of whatever you’re looking at.