Image Signal Processing for Fluorescent Flicker Reduction
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Solution Overview
Problem
Double or multiple exposure cameras face challenges in reducing fluorescent artifact effects due to flicker and color variations caused by fluorescent light sources, particularly when the sensor integration time is not a multiple of the fluorescent light period, leading to suboptimal image quality and false colors.
Innovation Solution
A method for processing image signals that involves determining the presence and period of fluorescent light, adjusting exposure times to align with the fluorescent light period, and applying a correction function to combine image signals, including phase-locking the short exposure time to the fluorescent light peak to minimize flicker and color errors, and applying a gain factor to shift problematic image parts out of the display range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor integration time is set to a multiple of the fluorescent light period to avoid flicker, then fluorescent artifact effects are reduced, but the short exposure time becomes inadequate for proper operation under fluorescent light conditions
Solution Approach 1:
The patent applies dynamics by making the exposure time configurable and adaptable based on detected fluorescent light conditions. The system dynamically adjusts the short exposure time to be a precise fraction of the long exposure time (1/R ratio) while both are synchronized to the fluorescent light period, allowing the camera to optimize exposure parameters in real-time based on environmental conditions.
Solution Approach 2:
The patent changes the exposure time parameters by establishing a mathematical relationship where short exposure time = long exposure time / R. This parameter transformation allows the short exposure to capture adequate light information while maintaining synchronization with the fluorescent light period, resolving the contradiction between artifact reduction and exposure adequacy.
2Illumination intensity
If the short exposure time is made several times shorter than the long exposure time to capture bright areas, then saturation in bright parts is avoided, but flicker and color variations increase under fluorescent lighting
Solution Approach 1:
The patent transforms the exposure time parameters by setting short exposure time = long exposure time / R, where R is the ratio between long and short exposure times. This mathematical relationship ensures that even the shortened exposure captures sufficient light information while maintaining synchronization with the fluorescent light period, thereby preventing color variations and flicker.
Solution Approach 2:
The system employs feedback by detecting the presence of fluorescent light and automatically adjusting the exposure time relationship. When fluorescent light is detected, the camera modifies the short exposure time to be a precise fraction of the long exposure time, creating a closed-loop control system that maintains color consistency under varying lighting conditions.
3Reliability
If manual switch or flicker detection mechanism is used to set integration time, then flicker is reduced for single exposure sensors, but multiple exposure time sensors cannot properly synchronize both long and short exposures
Solution Approach 1:
The patent achieves universality by creating a exposure time synchronization system that works for both single exposure and multiple exposure modes. The solution sets long exposure time to a multiple of the fluorescent light period and short exposure time to a fraction of the long exposure time (1/R ratio), making the system adaptable to different exposure configurations while maintaining flicker reduction across all modes.
Solution Approach 2:
The system applies dynamics by making the exposure time relationship configurable through the ratio parameter R. This allows the camera to dynamically adapt between different exposure configurations (single or multiple exposures) while maintaining synchronization with fluorescent light, providing versatility without sacrificing flicker reduction performance.
Data Source
AI summary
Methods are described for processing an image signal for double or multiple exposure cameras in order to reduce fluorescent artifact effects.