While virtual reality and augmented reality are within the same technological sphere, they are different things, which means Microsoft's HoloLens is different to products such as the Oculus Rift and Samsung Gear VR.
The key difference in layman terms is that virtual reality puts real world contexts into a virtually created world, whereas augmented reality places digital information into real world contexts.
Essentially this means that with augmented reality your environment becomes something to interact with, whereas virtual reality all takes place in a digitally created environment.
HoloLens is the most fleshed out augmented reality device at the moment, but a new patent by Microsoft could also turn the headset into a VR product.
At the moment, tech companies are either betting on augmented reality or virtual reality, but Redmond is developing HoloLens so that consumers will not have to make that choice. This may seem an easy accomplishment at first, after all the HoloLens looks like a virtual reality set, but actually converting the device to also be a VR headset took some engineering nous.
The patent filing (see below) states that Microsoft has developed a head mounted panel with electrochromic dimming module, which would mean users can switch the HoloLens from augmented to virtual reality.
HEAD-MOUNTED DISPLAY WITH ELECTROCHROMIC DIMMING MODULE FOR AUGMENTED AND VIRTUAL REALITY PERCEPTION
The technology provides a dimming module for a near-eye display, NED, device that controls an amount of ambient light that passes through the transmissive near-eye display to a user. The dimming module includes at least one electrochromic cell that enables variable density dimming so that the NED device may be used in an augmented reality (AR) and/or virtual reality (VR) application. The electrochromic cell may be a monochrome electrochromic cell having stacked layers of a monochrome electrochromic compound layer and insulator sandwiched between a pair of transparent substrates and conductors. A current may be applied to the conductor layers to control the amount of dimming in response to a dimming value. A NED device having a dimming module may be included in a visor, or other type of head-mounted display, HMD. The dimming module may be flat and supported by a flat waveguide mount in the user's field of view.
Basically the mechanism will allow users to use a button to dim out the external view, allowing them to be plunged into the immersion of virtual reality.
Considering developer kits for HoloLens are already heading out next month, it seems unlikely that Microsoft will be embedding this feature into the first generation devices. However, if Redmond can perfect the technology, expect to see it land on future HoloLens variants.