Dynamic LED Emission Patterns for HMD Tracking Resolution
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Solution Overview
Problem
Conventional tracking systems for head-mounted displays (HMDs) face challenges in accurately determining the position and orientation when the distance between the HMD and the external camera system exceeds a certain limit, as the infrared LEDs begin to merge, making it difficult to resolve unique LED centroids, leading to errors in tracking.
Innovation Solution
A coded tracking system where the HMD's locators, such as LEDs, dynamically adjust their emission pattern based on the resolution value determined by the imaging device, switching to a pattern with fewer LEDs emitting light and increased distance between them when resolution becomes poor, allowing for better tracking at longer ranges by reducing digitization errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If all LEDs are turned on during tracking, then the tracking system can capture sufficient light signals, but the LEDs merge when the distance is too great, making it impossible to identify unique LED centroids
Solution Approach 1:
The system segments the LED array into multiple groups that emit light in different patterns. Instead of all LEDs being on simultaneously, the locators are divided into subsets that activate sequentially or in different configurations, allowing the camera to resolve individual LEDs by capturing multiple images with different activation patterns.
Solution Approach 2:
The LED emission pattern is made dynamic rather than static. The system switches between different emission patterns (first pattern, second pattern, etc.) based on tracking conditions such as distance. This dynamic switching allows the system to adapt to varying distances and maintain centroid identification accuracy across different ranges.
2Length of stationary object
If the HMD moves far away from the camera, then the tracking range is extended, but the adjacent LEDs cannot be resolved in the image, leading to tracking errors
Solution Approach 1:
The system changes the emission parameters of the LEDs based on the determined resolution value. When the camera detects that LEDs are merging (low resolution value), it triggers a switch to a different emission pattern that increases the effective spacing between active LEDs, thereby improving resolvability at longer distances.
Solution Approach 2:
The system implements a feedback loop where the camera continuously monitors the resolution value of captured LED images. Based on this feedback, the pattern controller determines whether to switch between different emission patterns, ensuring optimal LED resolution is maintained across varying distances.
3Device complexity
If a fixed pattern of embedded devices is used, then the system structure is simple, but the system cannot adapt to varying distances, causing tracking failures at long ranges
Solution Approach 1:
The system employs periodic switching between different LED emission patterns. Rather than using a single fixed pattern, the locators periodically alternate between multiple patterns (first pattern, second pattern, third pattern, etc.), allowing the system to maintain adaptability to different distances while keeping the physical structure relatively simple.
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 approach enhances tracking accuracy over a wider range by improving the resolution of individual light sources, reducing errors, and optimizing performance for both near and far-range tracking conditions.
Implementation Method 1
An object being tracked, such as a head mounted display (HMD), has a plurality of locators, such as LEDs, which can be captured by a camera and analyzed
Data Source
AI summary
A coded tracking system includes an imaging device and a target object that includes a plurality of locators emitting light according to a first pattern. An image of the target object captured by the imaging device includes light received by the imaging device from a subset of the plurality of locators. A pattern controller is configured to determine a resolution value for an adjacent pair of light sources in the captured image. The resolution value is indicative of the pattern controller being able to resolve the adjacent pair of light sources as two separate sources. The pattern controller determines a second pattern for the locators based on the resolution value. The second pattern improves a likelihood that the pattern controller can resolve between individual light sources emitting light in the second pattern. The pattern controller instructs the target object for the locators to emit light according to the second pattern.