Compensating Window Lens Selection for HMD Camera Focus
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) face challenges in maintaining accurate camera focus due to variations in camera placement, leading to image distortions and reduced eye tracking precision, which are difficult to address without increasing manufacturing costs or HMD size.
Innovation Solution
The implementation of a compensating window system that dynamically selects the best lens from a plurality of options based on modulation transfer function measurements to correct tolerance-placement effects and boresight errors, using a mechanism such as a wheel or slider with varying diopters or a liquid lens, to optimize image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional HMDs use fixed camera placement, then manufacturing is simpler, but image focus accuracy deteriorates due to tolerance variations
Solution Approach 1:
The patent implements a dynamic lens selection system where multiple lenses with different diopter values can be switched based on measured focus requirements. The system dynamically determines which lens provides optimal focus for each camera unit and activates only that specific lens, transforming a static optical system into a dynamic one that adapts to manufacturing variations without requiring custom high-precision parts for each unit.
Solution Approach 2:
The system changes optical parameters by selecting from multiple lenses with different diopter values (e.g., -2.00, -1.50, -1.00, -0.50, 0.00). This parameter variation allows the system to compensate for focus errors caused by camera placement tolerances, transforming the problem from one requiring precise manufacturing to one solved by parameter selection.
2Manufacturing precision
If custom high-tolerance parts are used to correct focus errors, then image quality improves, but manufacturing costs increase
Solution Approach 1:
Instead of requiring custom high-tolerance camera mounts, the system uses standard lenses with varying diopter parameters. This allows manufacturers to use conventional, lower-cost camera placement fixtures while achieving precise focus through lens selection rather than precision mechanical positioning.
Solution Approach 2:
The patent creates multiple copies of standard lenses with different optical properties (different diopter values) rather than creating custom precision-machined camera mounting structures. This approach is more economical because it replicates optical elements rather than requiring expensive custom mechanical components for each camera unit.
3Measurement precision
If lens curvature is increased to improve focus, then image sharpness improves, but distortion increases
Solution Approach 1:
The system applies local quality optimization by selecting the specific lens curvature that is appropriate for each camera unit's position. Rather than using a single high-curvature lens for all units (which would cause distortion), each camera receives a lens with locally optimized curvature matched to its specific placement, achieving sharpness without excessive distortion.
4Manufacturing precision
If multiple lenses are provided for each camera, then focus accuracy improves, but device size increases
Solution Approach 1:
The system uses a dynamic switching mechanism that activates only one lens at a time for each camera based on measured focus requirements. This dynamic approach allows multiple lenses to be available in the system while ensuring that only the necessary subset is actively used, minimizing the space required compared to having all lenses simultaneously accessible to each camera.
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 allows for improved image capture and eye tracking accuracy by selecting the optimal lens, reducing the need for custom high-tolerance parts and maintaining HMD comfort and aesthetics, while enhancing the user's experience in artificial reality applications.
Implementation Method 1
receiving a captured image of a test target from a surface of an optical stack module. The captured image may be captured using a first lens
Implementation Method 2
compensating window system that dynamically selects the best lens from a plurality of options based on modulation transfer function measurements to correct tolerance-placement effects and boresight errors
Implementation Method 3
determine a modulation transfer function measurement for the captured image
Data Source
AI summary
Methods, apparatuses, and systems for using a compensating window to correct tolerance-placement effects on camera focus are provided. The system may receive a first captured image of a first test target from a surface of a target plane. The first captured image may be captured using a first lens of a camera. The system may determine a first modulation transfer function measurement for the first captured image. The system may determine that the first modulation transfer function measurement is within a threshold measurement. The system may send an alert indicative that the first lens is within the threshold measurement.