Image Pickup Tone Correction for Backlight Halation and Noise
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Solution Overview
Problem
Existing image pickup technologies face challenges in preventing pixel signal saturation in backlight scenes, leading to halation issues, which can amplify noise and result in unnatural image appearances when attempting to correct halation through dynamic range expansion or shining correction.
Innovation Solution
An image pickup apparatus and method that perform tone correction by combining exposure control and gain control, with specific correction units determining appropriate amounts based on photographing conditions to prevent pixel signal saturation, and analyzing the scene to selectively apply dynamic range expansion and shining corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dynamic range expansion correction is performed to make brighter the image photographed by darker exposure, then the halation is prevented from occurring, but a noise component of the image may also be amplified to cause a decrease in S/N ratio
Solution Approach 1:
The patent applies different correction strategies to different regions of the image based on their luminance characteristics. For underexposed regions (luminance ≤ threshold), dynamic range expansion correction is applied to brighten them. For overexposed regions (luminance > threshold), shining correction is applied to reduce halation. This localized approach ensures that noise amplification is minimized while still correcting halation in appropriate regions.
Solution Approach 2:
The patent dynamically adjusts correction parameters based on scene analysis. The determination unit calculates appropriate correction amounts by analyzing the photographing scene and determining the ratio of halation regions to total image area. When the halation region ratio exceeds a threshold, shining correction parameter is increased; when it's below the threshold, dynamic range expansion correction parameter is increased. This adaptive parameter adjustment optimizes the balance between halation correction and noise control.
2Object-affected harmful factors
If shining correction processing is performed to lower the signal value of the halation region, then the halation is corrected, but with information on the tone of the halation region already lost, the corrected region may become an unnatural image that appears like a so-called solid image when the halation region is large to some extent
Solution Approach 1:
The patent applies different correction strategies to different regions of the image based on their luminance characteristics. For underexposed regions (luminance ≤ threshold), dynamic range expansion correction is applied to brighten them. For overexposed regions (luminance > threshold), shining correction is applied to reduce halation. This localized approach ensures that tone information is preserved in regions where it still exists while correcting halation in saturated regions.
Solution Approach 2:
The patent applies shining correction selectively rather than uniformly across the entire image. The determination unit calculates the ratio of halation regions to total image area and only applies strong correction when this ratio exceeds a predetermined threshold. This partial action approach prevents over-correction and maintains natural appearance in regions where halation is not a significant issue.
3Object-affected harmful factors
If correction processing is applied to prevent pixel signal saturation, then halation is reduced, but noise components may be amplified and image quality may deteriorate
Solution Approach 1:
The patent dynamically adjusts correction parameters based on scene analysis. The determination unit calculates appropriate correction amounts by analyzing the photographing scene and determining the ratio of halation regions to total image area. When the halation region ratio exceeds a threshold, shining correction parameter is increased; when it's below the threshold, dynamic range expansion correction parameter is increased. This adaptive parameter adjustment optimizes the balance between halation correction and noise control.
Solution Approach 2:
The patent employs a feedback mechanism where the determination unit continuously analyzes the photographing scene and adjusts correction parameters accordingly. By calculating the ratio of halation regions to total image area and comparing it against thresholds, the system provides feedback to the correction units to optimize correction strength. This feedback loop ensures that correction is applied appropriately without excessive noise amplification.
Data Source
AI summary
An image pickup apparatus, which is configured to perform tone correction for preventing saturation of a pixel signal value of a photographed image, the image pickup apparatus including: a first correction unit configured to perform first tone correction that combines exposure control and gain control on the pixel signal value of the image; a second correction unit configured to perform second tone correction for reducing a pixel signal value in a region in which the pixel signal value of the image is higher than a predetermined value; and a determination unit configured to determine a first correction amount to be used for the first tone correction and a second correction amount to be used for the second tone correction in accordance with a photographing condition.