ECE Augmented Reality Head Mount

Background:

Augmented Reality(AR) is poised as a new paradigm for communication and computation. Users can see, often with a head mounted display, an environment that is augmented with digital assets that gives an almost immersive place where the physical world and the digital world combine. One of the most compelling use cases in AR is digital face-to-face conversations, much like the way video chats are today for 2D displays, but imagine actually feeling like you are in a space with another person who is digitally projected into this shared space. An element that is crucial for this experience is the ability to digitize the users face and body motions and expressions authentically.

Objectives:

The primary objective is to design, build, and test an adjustable head mount that meets the defined requirements. The intended use of the deliverable is as a demo in a convention/conference/tradeshow setting. Therefore, the head mount is expected to be easy to put on and take off, and to fit on a variety of users. The head mount needs to be designed to integrate the current prototype components together in a comfortable to wear footprint and easy for the user to move around to experience the system demo in a compelling way. Unlike the prototype this head mount will be designed to mount onto a Hololens 2. A secondary objective was to design our own standalone mount that could be used for future prototyping and testing.

Hololens 2 Design:

Our final design became like our second design idea above. We mounted the cameras and IMU's to the front of the Hololens 2 and the battery and StereoPi to the back. Mounting the cameras to the front allows for them to easily be placed in the same location every time. Mounting the battery and StereoPi to the back allows for more even weight distribution. Our design is comfortable to wear and securely houses all the necessary components.

For the cameras the mounts had to be secure to ensure that the camera angles would be the same across multiple users and uses. We decided to go with a clip design to allow for them to be easily put on and taken off and to be unobtrusive to the user. We added a thin layer of rubber to the inside of the clips to prevent sliding along the strap of the Hololens.

Part way through this project our sponsor asked if we could make the camera angles adjustable. We created a design that gave 20 mm of linear travel and 25° of angular travel. The linear adjustability is controlled by twisting a screw. The angular adjustability is controlled by a slider with a pin that locks at set angles, every 5° from 15°-40° from the vertical.

Once we had designed secure clips we then tested our camera angles. Our sponsor needed the cameras to be able to see the movement of the users facial features and limbs. We made the mounts with the same angle as the sponsors prototype and tested their view. We then showed the camera view to our sponsors to confirm that it was correct.

We decided to mount the Stereo Pi board and battery to the back of the Hololens because they are both larger components and there is more space to mount them there. Also, through our earlier weight distribution testing, we found that the weight was the most noticeable when the left and right sides were imbalanced and so we localized the stereo pi and battery at the center of the back to maintain balance. The difficult part was then creating a mount that matched the odd curvature of the back of the Hololens. We analyzed the radius of curvature of the Hololens back through a CAD model we found online and then created a mount from there. We iteratively tested and adjusted the mounting part of the stereo pi board and battery mount until it fit perfectly on the back of the Hololens. Since we were mounting to the back of the Hololens we decided to go with an elastic strap design for actually attaching it.

The purpose of the cable mounts is to contain the cables connecting the cameras and IMUs to the Stereo Pi board in a neat and compact manner. We created a small mount that went on the middle of the Hololens strap that neatly routed the cables to the Stereo Pi.

Standalone Design:

The main frame of the standalone head mount is comprised of a lightweight headband padded with a leather sleeve and an adjustable strap over the head for additional support. The components are then mounted to this headband with adjusted versions of the HoloLens 2 design