Variable Exposure CMOS Image Sensor Dynamic Range
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Solution Overview
Problem
Conventional image sensors face challenges in achieving optimal exposure durations, leading to either pixel saturation or loss of detail, and existing methods to increase dynamic range are either expensive or susceptible to motion artifacts.
Innovation Solution
The method involves capturing different portions of a scene with pixels of varying colors using alternating exposure durations, specifically for CMOS image sensors, where different exposure times are applied to different rows or color components to improve the signal-to-noise ratio and prevent saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a long exposure duration is used, then the dynamic range is improved, but pixel saturation occurs and image quality deteriorates
Solution Approach 1:
The pixel array is divided into multiple groups, with each group assigned a different exposure duration. This segmentation allows simultaneous capture of multiple exposure lengths within a single image, resolving the contradiction between long exposure (for dynamic range) and short exposure (for avoiding saturation).
Solution Approach 2:
The patent implements variable exposure durations dynamically across different pixel groups within the same image capture cycle. This dynamic approach allows the system to adapt exposure time to local scene requirements, improving both dynamic range and preventing saturation in different regions.
2Reliability
If a short exposure duration is used, then pixel saturation is avoided, but detail is lost due to low signal values
Solution Approach 1:
By segmenting the pixel array into groups with different exposure durations, the patent ensures that some pixel groups use longer exposures to capture detailed information in darker regions, while other groups use shorter exposures to avoid saturation in brighter regions.
Solution Approach 2:
Different regions of the image receive different exposure treatments based on local requirements. The patent applies local quality by assigning optimal exposure durations to specific pixel groups based on their local scene characteristics, preserving detail where needed while preventing saturation elsewhere.
3Duration of action of moving object
If multiple image sensors are used to capture multiple exposures, then dynamic range is improved, but device complexity and cost increase
Solution Approach 1:
A single image sensor performs multiple functions by capturing multiple exposure durations simultaneously through pixel group segmentation. This multi-functionality eliminates the need for multiple separate sensors, reducing device complexity and cost while maintaining the ability to capture wide dynamic range.
Solution Approach 2:
The patent merges multiple exposure captures into a single image by having different pixel groups simultaneously capture different exposure durations. This combining approach achieves the效果 of multiple sensors using only one sensor, reducing complexity while maintaining dynamic range improvement.
4Device complexity
If sequential image acquisitions are used, then device complexity is reduced, but motion artifacts are introduced
Solution Approach 1:
The patent uses periodic action by simultaneously initiating exposure in multiple pixel groups at different durations within the same capture cycle. This synchronized periodic exposure eliminates the time gap between acquisitions that causes motion artifacts in sequential methods.
Solution Approach 2:
The system dynamically controls different pixel groups to expose for different durations simultaneously, creating a dynamic multi-exposure capture that occurs within a single time window. This dynamic simultaneous capture avoids the temporal separation that introduces motion artifacts.
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
This approach enhances the dynamic range and signal-to-noise ratio of image sensors without requiring multiple sensors or sequential image acquisitions, reducing the risk of motion artifacts and improving image quality by optimizing exposure times for each color component.
Implementation Method 1
capturing a first portion of the scene with a first plurality of the pixels of a first color... capturing a second portion of the scene with a second plurality of the pixels of a second color
Data Source
AI summary
A method of capturing an image of a scene using an image capture device having an array of pixels, wherein the array of pixels includes pixels of different colors, includes, for a first duration, capturing a first portion of the scene with a first plurality of the pixels of a first color, and for a second duration, capturing a second portion of the scene with a second plurality of the pixels of a second color. The first and second durations are different and the first and second durations are chosen, at least in part, to improve the signal to noise ratio of the image capture device.