CMOS Image Sensor Interlaced Pixel Exposure Bracketing
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Solution Overview
Problem
CMOS image sensors in mobile devices often have insufficient dynamic range to capture outdoor scenes accurately, leading to signal-to-noise ratio discontinuities and image quality issues when combining multiple frames with different exposure lengths.
Innovation Solution
A method and device that capture a first image with a longer exposure length and multiple images with shorter exposure lengths on a CMOS image sensor, combining these into a high dynamic range image with reduced signal-to-noise ratio discontinuities and minimized motion blur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple frames with different exposure lengths are combined to compensate for insufficient dynamic range, then the dynamic range of the captured image is improved, but signal-to-noise ratio discontinuities occur between frames
Solution Approach 1:
The pixel array is divided into multiple subsets (first subset and second subset) that are interlaced, with each subset capturing frames with specific exposure lengths. This segmentation allows different exposure brackets to be captured simultaneously without sequential transitions, eliminating SNR discontinuities at frame boundaries while maintaining comprehensive dynamic range coverage.
Solution Approach 2:
The patent transitions from temporal stacking of multiple frames to spatial distribution across interlaced pixel subsets. By capturing multiple exposure brackets simultaneously in different spatial regions and then combining them, the system eliminates the temporal discontinuities inherent in sequential frame capture while maintaining the dynamic range benefits.
2Measurement precision
If multiple frames are combined to achieve higher dynamic range, then detail in bright and shadow areas is improved, but motion blur increases
Solution Approach 1:
Multiple exposure brackets are prepared simultaneously in interlaced pixel subsets before final combination. This preliminary parallel capture ensures that all exposure levels are available at the same moment in time, allowing motion compensation during the combining process while maintaining detail accuracy across the full dynamic range.
3Quantity of substance
If a single long exposure is used to capture dark areas, then signal strength in shadow regions is improved, but bright areas become saturated and lose detail
Solution Approach 1:
The pixel array is segmented into interlaced subsets where some pixels capture with long exposure for dark areas while others capture with short exposure for bright areas. This segmentation allows simultaneous optimization for both extremes of the dynamic range without the saturation and signal weakness problems of single-exposure approaches.
Solution Approach 2:
Different regions of the pixel array are assigned different exposure characteristics based on local lighting conditions and dynamic range requirements. This local quality approach allows each region to be optimized for its specific capture needs while contributing to the overall high dynamic range image.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the creation of high dynamic range images with improved signal-to-noise ratio and reduced motion blur, effectively addressing the limitations of existing technologies by simultaneously capturing multiple frames with different exposure lengths.
Implementation Method 1
capturing, on a first subset of pixels on an image sensor, a first image with a first exposure length
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
Methods, devices, and computer program products for image sensors with overlapped exposure brackets supporting multiple short exposures are described. In one aspect, a method of capturing an image is disclosed. The method includes capturing, on a first subset of pixels on an image sensor, a first image with a first exposure length. The method further includes simultaneously capturing, on a second subset of pixels on an image sensor, a plurality of images with a second exposure length, wherein the second exposure length is shorter than the first exposure length. The method further includes combining the plurality of images with a second exposure length into a second image. Finally, the method includes combining the first image and the second image.