FPGA Image Processing Apparatus for Flicker Detection
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Solution Overview
Problem
Existing image processing systems for vehicle-mounted cameras with rolling shutters face complexity and increased system control requirements when trying to identify and mitigate flicker from fluorescent light sources with different frequencies, particularly when crossing the Itoigawa-Shizuoka tectonic line in Japan, where power frequencies differ.
Innovation Solution
An image processing apparatus that includes a field programmable gate array (FPGA) for calculating pixel averages within a reference region, determining flicker presence and frequency by analyzing inter-frame differences, and adjusting exposure time to match the light source frequency, thereby simplifying the processing and system design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two types of exposure (normal and short time) are carried out to detect light source frequency, then flicker detection accuracy is improved, but control complexity and system complexity increase
Solution Approach 1:
The patent extracts only the necessary information (luminance distribution in vertical direction from single short-time exposure) needed for flicker detection, eliminating the need for multiple exposure types. This reduces control complexity while maintaining detection capability by focusing on the critical parameter that indicates flicker presence.
Solution Approach 2:
Instead of using normal exposure as the baseline and comparing with short-time exposure, the patent inverts the approach by using only short-time exposure images and detecting flicker through temporal changes in luminance distribution. This inversion simplifies the control mechanism while achieving the same detection goal.
2Measurement precision
If two types of exposure are carried out to detect light source frequency, then flicker detection accuracy is improved, but memory requirements increase
Solution Approach 1:
The patent extracts only the essential data (luminance distribution from current and previous short-time exposure frames) needed for flicker detection, eliminating the need to store multiple exposure types. This significantly reduces memory requirements while maintaining detection accuracy through temporal comparison.
Solution Approach 2:
The patent uses partial action by storing only the necessary previous frame data for comparison, rather than storing complete luminance distributions from multiple exposure types. This partial storage approach suffices for flicker detection while minimizing memory usage.
3Object-affected harmful factors
If a flicker elimination filter corresponding to 50 Hz or 60 Hz is used, then flicker is suppressed in that specific frequency area, but flicker occurs when crossing into the other frequency area
Solution Approach 1:
The patent implements dynamic adaptation by continuously detecting the current light source frequency through luminance distribution analysis and adjusting the flicker elimination filter parameters in real-time. This allows the system to adapt to frequency changes when crossing regional boundaries, maintaining flicker suppression across both 50 Hz and 60 Hz areas.
Solution Approach 2:
The patent uses feedback by continuously monitoring luminance distribution in vertical direction and using this information to adjust the flicker elimination filter settings. This closed-loop approach ensures the system automatically adapts to the current frequency environment, preventing flicker both in single-frequency areas and during transitions.
Data Source
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AI summary
An image processing apparatus includes: a difference calculation unit (51,115) that calculates a difference value of a feature amount of image data of a predetermined region between a present frame and a past frame; a first counting unit (117) that counts number of times when an absolute value of the difference value exceeds a threshold during a predetermined period of time; a second counting unit (120) that counts number of times when the difference value of the image data have different plus-minus signs between a present frame and a past frame during a predetermined period of time; and an identification unit (62) that identifies a light source frequency by comparing the output of the second counting unit (120) with a predetermined value when the output of the first counting unit (117) exceeds a predetermined value.