Optical Positional Tracking Using Spatially Modulated Beacon Signals
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Solution Overview
Problem
Current positional tracking systems for virtual reality and augmented reality face challenges in precision, latency, and user setup complexity, particularly in home environments with transparent, shiny, or textureless objects, and require large tracking markers that modify the environment and increase HMD weight.
Innovation Solution
An optical tracking system using spatial coding technology with beacon transmitters that broadcast spatially modulated optical signals, allowing sensors to determine planar bearings and fuse with inertial measurements for high-resolution, low-latency position and orientation determination, enabling room-scale multi-user tracking without the need for large markers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large tracking markers are used to encode data, then tracking precision is improved, but the area of the object increases and the environment must be greatly modified
Solution Approach 1:
The patent changes the parameter of data encoding from spatial (large markers) to temporal (frequency modulation). By modulating the optical carrier frequency over time to encode data, the system achieves high-precision tracking without requiring large tracking markers, thus resolving the contradiction between tracking precision and marker area.
2Measurement precision
If tracking markers are placed on walls to map environment, then positional tracking is improved, but the ease of operation deteriorates due to complex calibration
Solution Approach 1:
The system employs self-calibrating algorithms that automatically determine the positions and orientations of transmitters and receivers without requiring manual calibration. The receivers autonomously identify transmitter locations and compute bearing angles, eliminating the need for users to perform complex calibration procedures while maintaining high positional tracking accuracy.
3Measurement precision
If tracking cameras are attached to HMD with good lens, then tracking precision is improved, but the weight of HMD increases significantly
Solution Approach 1:
The patent replaces heavy mechanical camera-based tracking systems with lightweight optical receivers that detect modulated light from transmitters. This substitution eliminates the need for heavy lenses and cameras on the HMD, significantly reducing weight while maintaining high tracking precision through optical frequency modulation and detection.
4Ease of operation
If natural image features are used instead of tracking markers, then ease of operation is improved, but measurement precision deteriorates in transparent, shiny, and textureless environments
Solution Approach 1:
The system changes the tracking parameter from visual feature recognition to optical frequency detection. By modulating and detecting the frequency of optical signals rather than relying on visual textures, the system achieves high precision tracking in environments where natural image features fail, such as transparent, shiny, or textureless surfaces.
5Manufacturing precision
If decoding is performed on PC instead of onboard processor, then manufacturing precision is improved, but loss of time increases due to data transmission
Solution Approach 1:
The patent segments the decoding function from the central PC and implements it locally on onboard processors attached to or integrated with the HMD. This segmentation allows real-time frequency modulation detection and data decoding to occur locally, eliminating data transmission delays while maintaining high decoding accuracy through dedicated processing units.
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
The system provides precise, low-latency, and easy-to-set-up tracking for multiple objects in room-scale volumes, maximizing tracking volume and scalability, while reducing environmental modification and HMD weight, and is robust against interfering reflections.
Implementation Method 1
beacon transmitters that broadcast spatially modulated optical signals
Implementation Method 2
allowing sensors to determine planar bearings
Data Source
AI summary
Optical positional tracking systems that may be used in virtual reality (VR)/augmented reality (AR) applications are described. Exemplary implementations comprise one or more receivers and one or more transmitters. Exemplary transmitters contain two orthogonal rotors that each emit a fan-shaped laser beam. Each beam is swept as the rotors are spun at constant speed. Exemplary optical receivers can be relatively small, and mounted at convenient locations on the VR display. These receivers consist of small optical detectors that may be mounted on head-mounted VR displays. Exemplary systems determine position by measuring the time at which each swept beam crosses each receiver/detector.