HMD Virtual Image Distance Adjustment for Eye Strain Relief
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Solution Overview
Problem
Prolonged use of head-mountable displays (HMDs) leads to eye strain, fatigue, and blurred vision due to sustained focus on a preset virtual image distance, causing eye muscle tension.
Innovation Solution
Adjust the virtual image distance based on eye tiredness detection using electromyographic (EMG) sensors and eye cameras to alleviate muscle strain by changing the focal length of the lens, reducing the need for constant focus tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the virtual image distance is fixed at a preset distance, then the HMD can maintain a stable display configuration, but the wearer experiences eye strain and fatigue due to sustained muscle tension
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed virtual image distance to a dynamic, adjustable distance. The system continuously monitors eye muscle tension via EMG sensors and automatically adjusts the focal length of the lens element, allowing the virtual image distance to change in real-time based on the wearer's physiological state. This resolves the contradiction by maintaining display stability through automated control while eliminating eye strain through adaptive focal adjustment.
Solution Approach 2:
The system implements feedback by using EMG sensors to detect eye muscle tension levels and feeding this information back to the control circuitry. The control system then adjusts the lens focal length accordingly, creating a closed-loop control system. This feedback mechanism allows the display to adapt to the wearer's changing eye conditions, maintaining stability while preventing harmful eye strain accumulation during prolonged use.
2Stability of the object's composition
If the HMD requires sustained focus on a preset virtual image distance, then the display system remains simple and stable, but the wearer's eye muscles experience continuous tension leading to blurred vision
Solution Approach 1:
The system applies self-service by enabling the HMD to automatically monitor and adjust its own display parameters without user intervention. The EMG sensors detect eye muscle tension, and the control circuitry autonomously modifies the lens focal length to optimize comfort. This self-regulating mechanism maintains display stability while continuously adapting to the wearer's physiological needs, eliminating the need for manual adjustment and preventing eye fatigue.
Solution Approach 2:
The patent implements parameter changes by dynamically modifying the focal length of the lens element based on detected eye muscle tension. Instead of maintaining a fixed optical parameter, the system varies the focal length in response to physiological feedback, thereby changing the virtual image distance. This parameter adjustment resolves the contradiction by preserving display system stability through controlled modification while significantly improving eye muscle comfort during extended wear.
3Object-affected harmful factors
If the virtual image distance is adjusted to alleviate eye strain, then eye comfort improves, but the display configuration becomes more complex
Solution Approach 1:
The system replaces complex mechanical adjustment mechanisms with an electronically controlled optical system. Instead of using movable lenses or adjustable mirrors that would increase mechanical complexity, the patent employs an EMG sensor-based detection system coupled with an electronically controllable lens element. This substitution reduces overall device complexity while enabling dynamic virtual image distance adjustment to alleviate eye strain.
Solution Approach 2:
The control circuitry serves multiple functions: it processes EMG sensor signals, determines eye muscle tension levels, calculates appropriate focal length adjustments, and actuates the lens element. This multi-functional integration reduces the need for separate dedicated components for each function, thereby minimizing device complexity while achieving the goal of reducing eye strain through dynamic distance adjustment.
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
Reduces eye strain and fatigue by naturally adjusting the focus, allowing extended use of HMDs with reduced discomfort.
Implementation Method 1
adjusting a focal length of the lens to correspondingly change the virtual image distance
Implementation Method 2
determining ciliary and extraocular eye muscle strain from electromyographic signals received from the HMD muscle sensor
Data Source
AI summary
Eye tiredness of a wearer of a head-mountable display is determined by a processor. The distance from eyes of the wearer of the head-mountable display to a virtual image displayed by the head-mountable display is adjusted by the processor based on the eye tiredness of the wearer of the head-mountable display that has been determined.