Conformal HMD Display Alignment Using Dual Inertial Sensors
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Solution Overview
Problem
Existing wearable displays, such as Head-Mounted Displays (HMDs), face misalignment issues due to variations in interpupillary distances and operational conditions, leading to poor coupling and misalignment with tracking systems, which are cumbersome and expensive to recalibrate.
Innovation Solution
A conformal display system that continuously computes and compensates for relative geometric orientations between the HMD and the helmet, using inertial sensors and a transfer-alignment algorithm to align images with real-world scenes in real-time, enhancing accuracy and reducing the need for manual recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration is performed to align HMD with tracking system, then alignment accuracy is improved, but calibration time and cost increase
Solution Approach 1:
The system uses inertial sensors attached to both the HMD and support structure to automatically detect and compensate for relative movements without requiring manual calibration. The processor continuously calculates transformation parameters from sensor data, enabling the system to self-align in real-time
Solution Approach 2:
The system continuously monitors relative orientation between HMD and support structure using inertial sensors, feeds this information back to the processor, and dynamically adjusts the displayed image orientation to maintain alignment. This closed-loop feedback mechanism ensures continuous accuracy without re-calibration
2Measurement precision
If manual recalibration is performed for changing operational conditions, then alignment accuracy is improved, but operational complexity increases
Solution Approach 1:
The system automatically adapts to changing operational conditions by continuously processing inertial sensor data to detect relative movements between HMD and support structure. The processor dynamically updates transformation parameters without requiring user intervention or manual recalibration procedures
Solution Approach 2:
The system changes the orientation parameters of the displayed images in real-time based on processed inertial sensor data. By dynamically adjusting these parameters according to detected relative movements, the system maintains alignment accuracy across varying operational conditions
3Measurement precision
If inertial sensors are attached to both HMD and display to detect relative movements, then alignment accuracy is improved, but device complexity increases
Solution Approach 1:
The inertial sensors act as intermediaries that indirectly measure the relative orientation between HMD and support structure by detecting their respective movements independently. The processor then computes the transformation parameters from these intermediate measurements, avoiding the need for direct complex measurement mechanisms
Solution Approach 2:
The inertial sensors serve multiple functions: they track the movement of the HMD, track the movement of the support structure, and provide data for calculating relative orientation. This multi-functionality reduces the need for separate dedicated components for each measurement task
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
Facilitates real-time automatic alignment, improving HMD accuracy by dynamically adjusting images to conform with the user's line of sight and platform coordinates, thereby alleviating the need for lengthy and costly manual calibration processes.
Implementation Method 1
at least one first inertial sensor attached to the support-structure and configured to acquire support-structure inertial readings information indicative of the support-structure movements over time
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A transfer-alignment system for a Head-Mounted Display (HMD), and a display coupled to the HMD, wherein the display is adapted to display images rendered by a display-processor, and wherein the HMD is monitored by a tracking system configured to provide information indicating position and/or orientation of the HMD with respect to a Frame of Reference (FoR), the system comprising: at least one first inertial sensor attached to the HMD and configured to acquire HMD's Inertial Readings Information (IRI); at least one second inertial sensor attached to the display and configured to acquire display's IRI; and a processor configured to: obtain the HMD's IRI, the display's IRI and the information indicating the HMD's position and/or orientation with respect to the FoR; continuously analyze movement information of the HMD and the display to determine relative orientation therebetween; and cause the display-processor to adjust the images to conform with respect to the FoR.