Single-Shot Multi-Exposure Flicker Correction via Vertical Profile Modulation
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Solution Overview
Problem
Fluorescent lighting causes objectionable flicker in video images due to periodic brightness variations, leading to degradation in image quality, especially when the camera's refresh rate is not an integer multiple of the AC power supply frequency, resulting in horizontal banding and uneven light sampling.
Innovation Solution
A method and apparatus for correcting flickers in single-shot multiple-exposure images by computing vertical profiles for both long and short exposure data, calculating a flicker modulation function, and multiplying each pixel in the short exposure data by this function to compensate for flicker, using an image-capturing apparatus with a lens and image sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the camera uses standard refresh rate (e.g., 60 Hz) that is not an integer multiple of the AC power supply frequency, then the camera can operate at standard refresh rates for normal video capture, but fluorescent flicker causes periodic brightness variation in the captured images leading to observable flickering artifacts
Solution Approach 1:
The patent applies preliminary action by computing vertical profiles and detecting flicker characteristics before final image processing. The system identifies the flicker modulation function from the captured image data and uses this information to correct the flicker artifacts in subsequent processing steps, preventing the artifacts from appearing in the final output.
Solution Approach 2:
The patent changes parameters by computing a flicker modulation function that characterizes the periodic brightness variation, then applying this function to adjust the pixel values in the image data. This transforms the image data from a state with flicker artifacts to a state where the flicker is corrected, while maintaining the standard camera refresh rate operation.
2Measurement precision
If line-by-line sequential sampling is used in exposure image capture, then the image sensor can capture the entire image sequence, but each line is sampled at slightly different times causing horizontal banding when the exposure duration spans non-integer multiples of the AC power supply cycle
Solution Approach 1:
The patent applies parameter changes by computing vertical profiles that capture the temporal variation in light intensity across different lines of the image. The system detects the flicker characteristics from these profiles and applies a modulation function to uniformize the brightness across all lines, eliminating horizontal banding while preserving the complete image capture.
Solution Approach 2:
The patent uses preliminary action by analyzing the vertical profiles to detect flicker patterns before final image processing. The flicker modulation function is derived from this preliminary analysis and then applied to correct the horizontal banding artifacts, ensuring uniformity across the entire image while maintaining the sequential sampling approach.
Data Source
AI summary
A method for correcting flickers in a single-shot multiple-exposure image and associated apparatus is provided. The single-shot multi-exposure image includes first image data and second image data. The method includes the steps of: computing a first vertical profile for the first image data and a second vertical profile for the second image data; computing a flicker modulation function according to the first vertical profile and the second vertical profile; and multiplying each pixel in the second image data by the flicker modulation function to correct flickers.