Head-Mounted Device Flicker Synchronization for Judder Mitigation
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Solution Overview
Problem
Head-mounted devices experience noticeable judder and double images due to light sources in the environment being modulated at frequencies different from the frame rate of cameras and displays, leading to user discomfort and motion sickness.
Innovation Solution
The device includes sensors to detect light frequency and phase, adjusting the frame rate and exposure periods of image sensors and displays to mitigate judder, using techniques such as frequency and phase locking to align camera exposures with light source characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frame rate of cameras and displays is kept fixed, then device operation is simple and stable, but judder and double images occur when light sources are modulated at different frequencies
Solution Approach 1:
The patent implements dynamic frame rate adjustment where the camera and display frame rates are no longer fixed but are dynamically adapted to match the detected light source frequency. The system continuously monitors the light frequency and adjusts the frame rate accordingly, transforming a static system into a dynamic one that responds to environmental conditions, thereby eliminating judder and double images.
Solution Approach 2:
The patent changes the operational parameters (frame rate and exposure time) based on the detected light source frequency. By adjusting these parameters dynamically, the system synchronizes image capture and display with the modulated light sources, preventing artifacts while maintaining reliable image quality across varying lighting conditions.
2Object-affected harmful factors
If the frame rate is adjusted to match light source frequency, then judder is reduced, but the system becomes more complex and requires continuous frequency detection
Solution Approach 1:
The patent implements a feedback mechanism where the light source frequency is continuously detected and this information is fed back to adjust the camera frame rate and exposure time. This closed-loop control system automatically compensates for varying light frequencies, reducing judder while managing system complexity through automated adaptation rather than manual configuration.
Solution Approach 2:
The system performs self-adjustment by automatically detecting the light frequency and configuring its own frame rate and exposure parameters without external intervention. This self-service capability reduces the need for complex manual control systems while effectively mitigating judder artifacts.
3Illumination intensity
If exposure periods are lengthened to capture more light, then image quality improves, but banding artifacts increase when light sources are modulated
Solution Approach 1:
The patent dynamically adjusts the exposure time parameter based on the detected light source frequency and characteristics. By optimizing exposure duration to match the light modulation cycle, the system captures sufficient light for good image quality while avoiding the integration of multiple light cycles that cause banding artifacts.
Solution Approach 2:
The patent synchronizes the exposure periods with the periodic nature of modulated light sources. By aligning exposure timing with the light frequency, the system captures light in a periodic manner that matches the source modulation, preventing banding while maintaining adequate illumination levels in the captured images.
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
Effectively reduces judder and double images, minimizing user discomfort and motion sickness by dynamically adjusting system frame rates and exposure times to match light source frequencies and phases.
Implementation Method 1
with a flicker sensor, sensing light in the scene; obtaining a frequency of the sensed light; and obtaining a phase of the sensed light
Data Source
AI summary
A method of operating an electronic device such as a head-mounted device to mitigate judder, double images, ghosting, and other display artifacts is provided. The method can include acquiring images of a scene with one or more cameras, outputting the acquired images of the scene with one or more displays, sensing light in the scene with a flicker sensor, obtaining a frequency and a phase of the sensed light, and setting or locking a frame rate of the cameras based on the frequency of the sensed light. The method can also include shifting or locking exposure periods of the cameras based on the phase of the sensed light. Determination of whether judder is present can involve computing a display artifact severity parameter and comparing that parameter to a threshold.