Six Degree-of-Freedom Optical Tracker for Near-to-Eye Displays
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Solution Overview
Problem
Existing near-to-eye (NTE) display devices require complex, heavy, and expensive six degree-of-freedom tracking systems to accurately and efficiently track the position and orientation of a viewer's head, which is not suitable for compact, lightweight designs.
Innovation Solution
A six degree-of-freedom optical tracker system comprising light emitting diodes (LEDs), an LED controller, a single position sensing device, and a processor, where LEDs emit light sequentially, and the processor determines the structure's position and orientation using position data from the sensing device, while disabling LEDs outside the sensing device's field of view to reduce noise and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex six degree-of-freedom tracking system is used to achieve accurate head position and orientation tracking, then measurement precision is improved, but device complexity and weight increase
Solution Approach 1:
The tracking system is segmented into distinct functional modules: multiple LEDs are divided and positioned at specific locations on the head-mounted structure, each LED is controlled independently by separate drive circuitry, and the position sensing device is separated from the head-mounted portion. This segmentation allows each component to be optimized independently while maintaining overall system accuracy.
Solution Approach 2:
The system employs periodic action through sequential LED activation where LEDs are turned on and off in a predetermined sequence rather than simultaneously. The LED controller activates each LED individually for brief periods, creating a time-multiplexed signal pattern that the position sensing device detects to calculate head position and orientation. This periodic activation reduces power consumption and simplifies the control system.
2Measurement precision
If multiple LEDs are activated simultaneously to improve position detection accuracy, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The LED controller activates each LED individually for brief periods in a sequential manner rather than keeping all LEDs continuously on. This time-multiplexed approach ensures that at any given moment, only one or a few LEDs are active, dramatically reducing power consumption while still providing sufficient data points for accurate position and orientation calculation through the sequential detection pattern.
Solution Approach 2:
The system maintains continuous useful action by rapidly cycling through the LED sequence at a frequency high enough to provide continuous position tracking data. The sequential activation creates an effectively continuous information stream for the position sensing device, ensuring accurate real-time tracking without the energy waste of simultaneous continuous LED operation.
3Reliability
If all LEDs are kept active to ensure continuous tracking, then reliability is improved, but heat generation and power consumption increase
Solution Approach 1:
The system uses periodic LED activation with rapid cycling through the LED sequence, creating effective continuous tracking through high-frequency time-multiplexing. Each LED remains off for most of the cycle and activates only briefly when needed, minimizing heat generation while maintaining tracking reliability through the rapid succession of activation events that provide continuous positional information.
Solution Approach 2:
The system discards the need for simultaneous LED activation by recovering positional information through sequential detection. The position sensing device captures data from each LED as it activates in sequence, and the processor recovers complete position and orientation information by integrating the sequential measurements, eliminating the need for all LEDs to be active simultaneously and thereby reducing heat generation.
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 system provides a high precision, high speed, lightweight tracking solution for NTE display devices, enabling accurate and jitter-free registration and rendering of display elements, improving system accuracy and reducing heat generation.
Implementation Method 1
each LED is coupled to receive a drive current and is configured, upon receipt of the drive current, to emit light
Implementation Method 2
The position sensing device has a field of view (FOV) and is configured to receive the light emitted from each of the LEDs within the FOV and to supply position data for each LED
Data Source
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AI summary
A six degree-of-freedom optical tracker system includes LEDs that are mounted on a structure, and are each configured to emit light. An LED controller is coupled to the LEDs and supplies drive current to each of the LEDs in a manner that causes the LEDs to sequentially and individually emit light. A single position sensing device that is spaced apart from each of the LEDs receives the light emitted from each of the LEDs and supplies position data for each LED. A processor receives the position data and determines the position and orientation of the structure relative to the single position sensing device.