Microsoft Hololens Hardware - https://developer.microsoft.com/en-us/windows/mixed-reality/hololens_hardware_details
Mixed reality refers to a continuum of Virtual Reality (VR) technologies in which real and virtual objects are combined in a single display. While VR typically refers to environments that place the user in an immersive and completely computer generated virtual world, Augmented Reality (AR) preserves the user’s awareness of, and ability to interact with, their immediate physical context by compositing the real world and computer generated models in a blended 3d space. The idea of using AR to visualise designs or instructions in-situ to assist with manufacturing tasks has existed since the technologies conception. Caudell and Mizell first coined the term to describe a head-mounted see-through display (HMD) that would augment an aircraft assembly worker’s field of view with digital information, such as the location of drill holes in 3d space.
Caudell & Mizell - Augmented Reality Concept - http://ieeexplore.ieee.org/document/183317/
The Hololens is an optical head-mounted display that composites virtual content with the users field of view by rendering to a transparent stereoscopic light field display. The illusion of virtual content appearing fixed in place (registered to the physical environment) is achieved through a combination of 3D scan data created with an infrared depth camera and “inside out tracking” using feature pixels from RGB video. These cameras detect user gestures and hand location, and a 6DOF sensor on the device captures head position and orientation to infer the wearer’s gaze. Users interact with virtual content using a combination of gestures, gaze and voice commands.
The head-mounted display of the hololens has several advantages over AR and VR experiences viewed through the video screen of a phone or tablet. It frees up your hands to interact with your physical environment or digital content in a natural way. The position and depth of holograms is also easier to infer from the see through display than from mobile cameras with different focal lengths to your eyes.