Secrets of HoloLens optics revealed

Recently and for the very first time we heard details of the Holographic Processing Unit in the HoloLens. It seems Microsoft is being a lot more open about the technology in the HoloLens, and have now also revealed the details of the special optics in the augmented reality device.

Unlike the simple LCD screens in virtual reality headsets, augmented reality headsets are a lot more complicated, requiring an image to be overlaid on a view of the real world.

To generate the image Microsoft uses two HD 16:9 “light engines,” which are small liquid crystal on silicon (LQoD) displays like on a Pico projector. The image then pass through imaging optics , a waveguide,  combiner and then diffraction gratings  that direct the image at your eye. The diffraction grating is created using a special coating on the surface of the glass, rather than glass itself.

The HoloLens uses 3 layers of diffractive gratings (seen in the first image) to generate RGB color holograms.

Microsoft also does eye tracking using an infra-red light and sensor to allow users to select items using their gaze.

Microsoft notes that the whole system needs to be exactly right, else the hologram would swim and users would get nauseous.

They also note that the HoloLens could adjust its interpupillary distance both horizontally (the most usual method) and vertically, which gave them the biggest “eye box” in the industry, meaning more people would use the device comfortably.

This ground-breaking technology, combined with the HPU, certainly explains why the HoloLens is worth every cent of its $3000 price.

The HoloLens is currently on sale to both researchers and for commercial use.  The Microsoft HoloLens Commercial Suite includes the Development Edition hardware as well as enterprise features for added security and device management. This suite acts as a solution for companies to confidently pilot and deploy HoloLens inside their organization.

The HoloLens can be found at the Microsoft Store here and read much more about the device at Toms Hardware here.