Image Sensor Dual Gain Contrast Brightness Distribution
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Solution Overview
Problem
The uniform gain contrast scheme in image sensors limits the expansion of the output dynamic range, especially for low-contrast images, and reduces the input dynamic range, leading to image degradation, particularly in high-contrast scenarios.
Innovation Solution
An image sensor employing a dual gain contrast scheme that calculates the minimum and maximum brightness values for dark and bright regions, respectively, to determine specific contrast gains for each region, allowing for dynamic adjustment of image brightness distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a uniform gain contrast scheme is applied to adjust image brightness, then the brightness distribution is simplified to process, but the output dynamic range expansion is limited for low-contrast images and input dynamic range is reduced for high-contrast images
Solution Approach 1:
The image is divided into multiple brightness regions (dark region, middle region, bright region) based on histogram analysis. Each region is assigned a different gain value (first gain, second gain, third gain) to optimize contrast adjustment for that specific region, thereby expanding output dynamic range without reducing input dynamic range
Solution Approach 2:
Different gain values are applied to different brightness regions of the image. The first gain is applied to dark regions, the second gain to middle regions, and the third gain to bright regions. This localized adjustment ensures that each region's dynamic range is optimized according to its specific characteristics, improving overall image quality while maintaining input dynamic range
2Manufacturing precision
If histogram equalization is used to optimize brightness distribution, then optimal brightness distribution is achieved, but hardware architecture becomes complicated as pixel count increases
Solution Approach 1:
Instead of implementing complex histogram equalization hardware, the patent changes the approach by using pre-calculated gain values (first, second, and third gains) corresponding to different brightness regions. The contrast adjustment is achieved by multiplying pixel values in each region by their respective gain values, which is computationally simpler and more suitable for hardware implementation while still achieving optimal brightness distribution
Data Source
AI summary
Provided is an image sensor that can solve the limitation in expanding an output dynamic range, which is caused when a uniform gain contrast scheme is applied, and prevent the reduction of an input dynamic range, thereby stably adjusting the distribution of image brightness. The image sensor includes a contrast gain adjuster for adjusting a brightness distribution of an image detected from a pixel array by controlling a contrast gain of an inputted pixel data. The contrast gain adjuster calculates a minimum brightness value of a dark region and a maximum brightness value of a bright region from the image brightness distribution, the dark region and the bright region being divided according to a set reference value.