Tunable Lens Distortion Compensation in VR Displays
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Solution Overview
Problem
Tunable lenses in display systems for virtual reality can introduce lens distortion, making it difficult for users to view satisfactory three-dimensional images, especially when not properly compensated for different focal lengths.
Innovation Solution
An electronic device with adjustable focal length lenses and a distortion compensation circuit that predistorts image frames using mapping and interpolation circuitry and look-up tables to compensate for lens distortion at various focal lengths, ensuring undistorted images are displayed across different focal settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tunable lenses are used to display virtual reality content at different focal lengths, then vergence-accommodation conflicts are reduced, but lens distortion is introduced
Solution Approach 1:
The system performs preliminary predistortion of image frames before they reach the tunable lenses. Distortion compensation circuitry applies opposite distortion patterns to the displayed images in advance, so that when the light passes through the tunable lenses, the pre-applied distortion is corrected and the final perceived image is undistorted.
Solution Approach 2:
The distortion compensation circuitry generates and applies anti-distortion patterns that are equal in magnitude but opposite in direction to the expected lens distortion. This preliminary anti-action counteracts the harmful distortion effect before it fully manifests, allowing the tunable lenses to function at different focal lengths without introducing unacceptable image distortion.
2Manufacturing precision
If distortion compensation is applied for multiple focal lengths, then image quality is improved, but device complexity increases
Solution Approach 1:
The distortion compensation system is segmented into separate lookup tables for different focal lengths. Each focal length setting has its own pre-calculated distortion compensation data stored in memory, allowing the system to handle multiple focal lengths independently. The distortion compensation circuitry switches between these segmented compensation patterns based on the current focal length setting.
Solution Approach 2:
Instead of implementing complex real-time distortion calculation algorithms, the system uses pre-calculated distortion compensation patterns stored as lookup tables. These tables contain copied and stored distortion correction data for various focal lengths, which can be quickly retrieved and applied without performing complex computations during operation.
Data Source
AI summary
An electronic device such as a head-mounted display or other display system may have a pair of adjustable focal length lenses. Control circuitry in the head-mounted display may adjust the adjustable focal length lenses so that the adjustable focal length lenses exhibit a series of different focal lengths. A graphics processor may generate undistorted image frames. The adjustable focal length lenses may exhibit a different amount of lens distortion at each focal length. To compensate for these different amounts of lens distortion, a distortion compensation circuit may predistort the undistorted image frames by an appropriate amount for each focal length. The distortion compensation circuit may include mapping and interpolation circuitry and look-up tables that store mapping and interpolation data for each of the focal lengths.