What exactly is the HoloLens?

The HoloLens is a first of its kind head-worn, standalone computer with a sensor array, which includes microphones and multiple types of camera, a spatial sound speaker array, a light projector, and an optical waveguide.

The HoloLens is not only a wearable computer, it is also a complete replacement for the standard 2D display. It has the capability of using holographic projection to create multiple screens throughout an environment and fully 3D-rendered objects. With the HoloLens sensor array, these holograms can fully interact with the environment you are in.

The sensor array allows the HoloLens to see the world around it, to see the input from the user's hands, and for it to hear voice commands. Although Microsoft has been very quiet about what the entire sensor array includes, we have a good general idea about the components used in the sensor array; let's take a look at them:

• One IMU: The Inertia Measurement Unit (IMU) is a sensor array that includes an accelerometer, a gyroscope, and a magnetometer. This unit handles head orientation tracking and compensates for the drift that comes from the Gyroscope's eventual lack of precision.
• Four environment understanding sensors: These together form the spatial mapping that the HoloLens uses to create a mesh of the world around the user.
• One depth camera: This is also known as a structured light 3D scanner. This device is used for measuring the 3D shape of an object using projected light patterns and a camera system. Microsoft first used this type of camera inside the Kinect for the Xbox 360 and Xbox One. 
• One ambient light sensor: Ambient light sensors or photosensors are used for ambient light sensing and proximity detection.
• 2 MP photo/HD video camera: This is used for taking pictures and video.
• Four-microphone array: These do a great job of listening to the user and not the sounds around them. Voice is one of the primary input types with HoloLens.

Putting all of these elements together forms a Holographic computer that allows the user to see, hear, and interact with the world around them in new and unique ways: