Inside-out 6-DoF ultrasonic controller tracking solution

15th January 2019
Alex Lynn

It has been announced that TDK Corporation is expanding its Chirp Microsystems ultrasonic product portfolio with Chirp SonicTrack, an ultrasonic six-degree-of-freedom (6-DoF) controller tracking solution for all-in-one virtual reality systems. Chirp SonicTrack is an inside-out tracking system that fuses ultrasonic and inertial sensor data to provide 6-DoF position and orientation tracking of a hand-held controller with sub-millimetre precision over a field of view of over 240°. 

The first VR system to use the SonicTrack tracking solution is the developer kit of HTC’s Vive Focus all-in-one VR system, where Chirp-enabled 6-DoF controllers allow users to experience immersive VR content with a standalone headset.

Powered by Chirp’s tiny, ultra-low power ultrasonic transceiver product, the CH-101, Chirp SonicTrack is the only inside-out tracking solution on the market today based on true 3D position information. The position tracking system utilises sonar by transmitting ultrasonic pulses between CH-101 sensors inside the VR system’s head-mounted display (HMD) and the hand-held controllers, providing 3D position information of the controllers relative to the HMD. Competing camera-based solutions have only 2D image data, requiring computation-intensive image processing from multiple cameras to estimate 3D position information.

Chirp’s true 3D ultrasonic sensing advantage results in a solution that is much lower power and better optimised for the mobile processors used in all-in-one VR/AR/XR systems. The CH-101’s omnidirectional response makes it easy to track controllers over an extremely wide field of view – another advantage over camera-based systems.

Michelle Kiang, CEO and co-founder, Chirp Microsystems, stated: “Chirp has solved the industry-wide problem of 6-DoF controller tracking for mobile VR systems. Unlike camera-based computer vision systems, ultrasonic tracking is computationally light. The ultrasonic tracking system also offers ultralow power consumption as the power required is only a few milliwatts – about a hundred times less than an optical tracking system.

“It allows us to offer an incredibly wide field-of-view so that the HMD never loses track of the controllers as the user moves around. These features make our tracking solution ideal for mobile VR and AR systems where system cost, heat dissipation and short battery life are killer problems. We couldn’t think of a better platform for our tracking technology than HTC’s VIVE Focus, which is the most capable all-in-one VR system on the market today.”

Adrian Tung, Senior Vice President of HTC, added: “At Vive, we are constantly striving to push the limits of what is possible within VR hardware and software to offer a premium experience for our customers. Through Chirp’s SonicTrack technology, we are able to quickly upgrade our Vive Focus Developer kits to support 6-DoF control input. This makes it easier for developers and businesses to implement intuitive controls, and also greatly expands the potential content library for Focus.”

Chirp SonicTrack is designed to enable VR system providers to introduce their own 6-DoF controllers with fast time-to-market. Chirp supplies a hardware reference design and the complete software stack, including a sensor fusion software library. Relative to a 3-DoF controller design, a Chirp SonicTrack 6-DoF controller requires only the addition of CH-101 ultrasonic sensors. The small size of these sensors gives customers flexible industrial design options for VR controllers and HMDs. The Chirp SonicTrack sensor fusion software library uses minimal processor resources and is ready for use on Qualcomm Snapdragon and other mobile processors.

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