Image Capturing Apparatus Luminance Range Compression
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Solution Overview
Problem
Existing image capturing systems in low-illuminance environments increase noise and code amount when using Automatic Gain Control, leading to inadequate gradation correction and reduced encoding efficiency in surveillance cameras.
Innovation Solution
An image capturing apparatus that calculates exposure and performs range correction to compress luminance, identifying luminance changes and adjusting exposure or reference luminance values to minimize noise and maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Automatic Gain Control (AGC) is used to increase image luminance in low-illuminance environments, then the luminance of the image is increased, but noise is increased resulting in a larger code amount
Solution Approach 1:
The patent changes the luminance distribution parameters through gamma correction and luminance range compression. Instead of uniformly increasing gain, it applies non-linear transformation to the luminance values, compressing the dynamic range and redistributing luminance values to reduce noise amplification while maintaining visible luminance levels.
2Productivity
If gradation correction is performed to reduce code amount, then encoding efficiency is improved, but the image as a whole becomes darker or brighter resulting in inappropriate exposure
Solution Approach 1:
The patent dynamically adjusts gamma correction parameters and luminance range compression ratios based on the actual luminance distribution of the input image. By calculating statistical properties of the luminance histogram and adapting the correction curve accordingly, it maintains appropriate overall luminance while achieving effective gradation correction and reduced code amount.
3Productivity
If gradation correction is applied without considering signal change amount, then code amount is reduced, but image quality deteriorates due to insufficient or excessive correction
Solution Approach 1:
The patent implements a feedback mechanism where the luminance distribution after correction is evaluated, and the correction parameters are adjusted based on this feedback. The system calculates the luminance change amount and uses it to adaptively modify the gamma correction and range compression parameters, ensuring that correction is sufficient to reduce code amount but not excessive to degrade image quality.
4Productivity
If luminance range compression is performed, then code amount is reduced, but luminance distribution changes causing exposure issues
Solution Approach 1:
The patent employs adaptive luminance range compression where the compression ratio and target range are dynamically determined based on the input image's luminance characteristics. By adjusting the compression parameters according to the luminance histogram and scene requirements, it achieves code amount reduction while preserving natural luminance distribution and avoiding exposure problems.
Data Source
AI summary
The image capturing apparatus includes an image capturing unit for capturing a subject image, a calculating unit for calculating an exposure amount at a time of capturing by the image capturing unit, a range correction unit for performing range correction for compressing a range of luminance in an image signal captured by the image capturing unit, an identification unit for identifying a luminance change amount of an image signal caused by range correction, and a changing unit for, based on the luminance change amount identified by the identification unit, changing at least one of the exposure amount and a reference luminance value in an input/output characteristic in a case of performing the range correction.