Flicker Detection in Rolling Shutter Imaging Devices
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Solution Overview
Problem
Conventional imaging devices with rolling shutters struggle to detect flicker effectively, especially at high frame rates, as they require prior knowledge of the flicker frequency to reduce flicker in captured images, and high frame rates result in fewer cycles of the flicker pattern, making detection unreliable.
Innovation Solution
The implementation of automatic flicker detection using multiple image frames, where row-average values are computed and energy difference patterns are calculated to determine the flicker frequency, allowing for adjustments in exposure time to mitigate flicker, even at high frame rates where fewer cycles of the flicker pattern are present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional flicker detection methods are used, then flicker can be reduced when prior knowledge of flicker frequency is available, but detection becomes unreliable at high frame rates where fewer cycles of the flicker pattern are present
Solution Approach 1:
The patent transitions from analyzing temporal variations within a single frame to analyzing spatial patterns across multiple rows and columns simultaneously. By computing row-average values and comparing energy differences across the two-dimensional pixel array, the system can detect flicker patterns even when temporal sampling is limited at high frame rates.
Solution Approach 2:
The patent introduces intermediate computational steps including row-average value computation and energy difference pattern calculation. These intermediaries transform the raw pixel data into a form that highlights flicker characteristics, enabling reliable detection even with limited temporal cycles at high frame rates.
2Object-affected harmful factors
If the integration time is set to be a multiple of the flicker frequency, then flicker is reduced in captured images, but this requires prior knowledge of the flicker frequency which is not always available
Solution Approach 1:
The system performs self-diagnosis by automatically detecting the presence and characteristics of flicker in the captured scene. Through energy difference pattern analysis across multiple rows and columns, the imaging device can identify flicker conditions and adjust its operation accordingly without requiring external input or prior knowledge of the light source's flicker frequency.
Solution Approach 2:
The patent implements a feedback mechanism where the detected energy difference patterns inform subsequent imaging parameter adjustments. The system continuously monitors for flicker conditions and uses this information to modify exposure timing or other imaging parameters to mitigate flicker artifacts in real-time.
Data Source
AI summary
Common electronic devices having imaging systems that use a rolling shutter scheme suffer from flicker due to the oscillating brightness of an illuminating light source. Some imaging systems use fast frame rates that result in less than two cycles of the illuminating light source occurring during a single frame capture. For devices that employ rolling shutter schemes and fast frame rates, a method of data collection and processing is provided that utilizes a combination of multiple sets of more than two image data frames to automatically detect flicker. Measured patterns of energy differences between various image frames and a reference image frame may be compared with an expected pattern of energy differences to determine a probability of flicker detection due to a given flicker frequency. This probability of flicker detection may be used to activate flicker avoidance procedures in an electronic device.