Ultrasonic Transducers for HMD Range Finding
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Solution Overview
Problem
Current virtual reality (VR) and mixed reality (MR) systems face challenges in accurately mapping and tracking environments and accessories within physical spaces, particularly due to limitations with light-based sensors such as LIDAR, which struggle with surfaces like glass and mirrors, and interference from bright sunlight.
Innovation Solution
Incorporating ultrasonic transducers on both head-mounted displays (HMDs) and accessories to send and receive ultrasonic signals, allowing for the generation of 3D maps and tracking of distances and positions, while also using inertial-measurement units (IMUs) to correct for motion and orientation data, enabling more comprehensive environment scanning and collision detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If light-based sensors (LIDAR) are used for range finding, then mapping speed and coverage are improved, but detection accuracy deteriorates on surfaces like glass and mirrors and in bright sunlight
Solution Approach 1:
The system divides the sensing function into multiple independent sensor types (ultrasonic transducers and light-based sensors) that operate separately but complement each other. Each sensor type handles specific detection scenarios where it excels, with ultrasonic sensors specifically targeting glass and mirror surfaces where optical sensors fail.
Solution Approach 2:
The system combines data from multiple sensing modalities (acoustic and optical) to create a composite environmental model. This multi-sensory approach allows the system to overcome the limitations of individual sensor types by integrating their respective strengths.
2Area of stationary object
If multiple ultrasonic transducers are added to both HMD and accessory, then environment scanning coverage is improved, but device complexity increases
Solution Approach 1:
The system adds spatial distribution of sensors across multiple devices (HMD and accessory) to expand coverage. By placing transducers on both the head-mounted device and the hand-held accessory, the system creates a distributed sensing network that covers a larger three-dimensional space.
Solution Approach 2:
The ultrasonic transducers serve dual functions: they act as both transmitters and receivers, and the same hardware configuration is used on both the HMD and accessory devices, allowing each component to perform multiple roles in the ranging system.
3Reliability
If ultrasonic transducers are used instead of light-based sensors, then detection reliability on difficult surfaces is improved, but susceptibility to environmental interference increases
Solution Approach 1:
The system uses ultrasonic waves as an intermediary medium for detection, replacing direct optical detection with acoustic wave propagation. This intermediary approach allows detection to occur through materials (like glass) that are transparent to sound but opaque or reflective to light.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides accurate and robust range finding capabilities, overcoming limitations of light-based sensors by effectively mapping and tracking environments and accessories, including hard-to-detect surfaces, and providing users with real-time collision alerts through audio, visual, and haptic feedback.
Implementation Method 1
the ultrasonic transducers on the HMD and/or the accessory send ultrasonic signals or 'pings' that reflect or echo off surfaces in the environment; the echoes are received by some number of ultrasonic transducers on the HMD and/or on the accessory
Implementation Method 2
range finding sensors (e.g., transmitters and receivers (or transceivers), for example ultrasonic transducers)
Implementation Method 3
Time delays for the echoes can be measured and analyzed to estimate the distances and relative positions of the surfaces
Implementation Method 4
track the relative position of the accessory with respect to the HMD using the ultrasonic transducers, or a combination of the ultrasonic transducers with motion and orientation information obtained from an inertial-measurement unit (IMU)
Data Source
AI summary
Range finding methods and apparatus that may be implemented by VR/MR systems that include a head-mounted display (HMD) and an accessory that the user holds or wears. Range finding sensors (e.g., ultrasonic transducers) may be included on the HMD and on the accessory and used to track distances to and relative position of walls, objects, and other obstacles within constrained physical environments such as rooms, gyms, yards, or fields, or in unconstrained physical environments. Range finding information from the sensors on the HMD and accessory can be used to generate a 3D map of the user's environment that can be used for various purposes in the VR/MR system. In addition to mapping the user's environment, the range finding methods and apparatus may also be used to track the relative position of the accessory with respect to the HMD.