Rearview Video Flicker Correction for PWM LED Lights
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Solution Overview
Problem
Streaming video images captured from cameras, especially those with amplitude modulated light sources like PWM LED vehicle lamps, often result in flickering artifacts when rendered on displays due to mismatched exposure times and frame rates.
Innovation Solution
A display system and method that includes an image processing unit capable of detecting PWM LED lights, differentiating them from other time-varying light sources, tracking their pulsing patterns, and correcting flicker artifacts by adjusting pixel values to match the 'on' state of the lights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard video capture and display methods are used with PWM LED light sources, then the system operates with standard exposure times and frame rates, but flicker artifacts appear in the displayed images
Solution Approach 1:
The system performs preliminary detection of PWM LED light sources in captured images before displaying them. By identifying the presence of PWM LEDs and analyzing their pulsing patterns in advance, the system can pre-calculate appropriate exposure times and frame rates that will eliminate flicker, rather than reacting to flicker after it has occurred
Solution Approach 2:
The system dynamically changes exposure time and frame rate parameters based on the detected PWM LED characteristics. When PWM LEDs are detected, the system adjusts these parameters to match the LED pulsing frequency, thereby eliminating flicker artifacts in the displayed images
2Object-affected harmful factors
If exposure time is adjusted to match light source frequency to suppress flicker, then flicker is reduced, but the system becomes more complex requiring detection and analysis capabilities
Solution Approach 1:
The system performs self-diagnosis by automatically detecting the presence of PWM LED light sources and analyzing their pulsing patterns. This self-service capability allows the system to autonomously determine the appropriate exposure time and frame rate adjustments needed to eliminate flicker, without requiring external intervention or complex manual configuration
Solution Approach 2:
The system implements a feedback mechanism where detected PWM LED characteristics inform subsequent image capture and display parameters. By continuously monitoring for PWM LEDs and adjusting exposure/frame rate based on detected patterns, the system creates a closed-loop control system that automatically optimizes display quality
3Measurement precision
If frame rate is increased to capture PWM LED pulsing patterns, then flicker can be corrected, but data processing requirements and computational load increase
Solution Approach 1:
The system applies partial action by selectively processing only those image regions containing PWM LED light sources. Rather than analyzing entire images or increasing overall frame rate for all content, the system focuses computational resources only on detecting and characterizing PWM LEDs where needed, thereby reducing overall processing load while maintaining accuracy
Data Source
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AI summary
A display system is provided for a vehicle equipped with a camera for supplying streamed video images of a scene rearward of the vehicle. The display system includes an image processing unit for receiving the streamed video images and processing the streamed video images, and a display for displaying the processed streamed video images. To perform processing of the streamed video images, the image processing unit is configured to: detect amplitude-modulated light sources in the streamed video images, classify the detected amplitude-modulated light sources into one of several possible classifications, select the streamed video images in which an amplitude-modulated light source is detected that flickers based upon the classification of the amplitude-modulated light source, and modify the selected streamed video images to correct for flicker of any amplitude-modulated light sources in the selected streamed video images.