CMOS Image Sensor Dual Charge Accumulation for Global Shutter Aliasing Correction
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Solution Overview
Problem
Existing solid-state image taking apparatuses face challenges in correcting aliasing signals without reducing the number of effective pixels, leading to image distortion and reduced resolution due to varying accumulation periods and noise components across pixel rows.
Innovation Solution
A CMOS-type image sensor with a pixel array configuration that includes two electric-charge accumulation sections per unit pixel, allowing for simultaneous exposure and correction of aliasing signals without reducing the number of effective pixels, by using a global shutter mechanism and a correction section that utilizes aliasing signal components from the second electric-charge accumulation section to correct signals in the first electric-charge accumulation section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a global shutter mechanism is used to achieve simultaneous accumulation periods for all pixels, then image distortion is eliminated and simultaneity is achieved, but the device complexity increases due to requiring two electric-charge accumulation sections per pixel
Solution Approach 1:
The pixel array is segmented into two distinct electric-charge accumulation sections within each pixel: a first accumulation section for capturing image signals and a second accumulation section for capturing aliasing signals. This segmentation allows independent processing of useful image data and noise correction data, resolving the contradiction by organizing complexity into functional segments.
Solution Approach 2:
The second electric-charge accumulation section acts as an intermediary that captures aliasing signals which would otherwise contaminate the first accumulation section. By introducing this intermediate structure, the patent enables noise subtraction without compromising the primary image capture function, thus maintaining reliability while managing complexity.
2Measurement precision
If correction pixels are added to correct aliasing signals, then aliasing correction is achieved, but the number of effective image-taking pixels is reduced
Solution Approach 1:
Each pixel in the array is given dual functionality by incorporating both a first electric-charge accumulation section for image capture and a second electric-charge accumulation section for aliasing signal capture. This multi-functionality eliminates the need for separate correction pixels, as every pixel contributes to both image formation and noise correction, thereby maintaining the full pixel count for effective imaging.
Solution Approach 2:
The patent merges the functions of image capture and aliasing correction into a single pixel structure by combining two accumulation sections within each pixel. This merging allows simultaneous performance of both functions without requiring additional dedicated correction pixels, thus preserving the quantity of effective pixels while achieving precise aliasing correction.
3Ease of operation
If signal electric charge is held in the electric-charge accumulation section for extended periods, then readout flexibility is improved, but aliasing signal deterioration increases due to leak components and noise
Solution Approach 1:
The patent applies preliminary action by capturing the aliasing signal in the second accumulation section at the same time as the image signal is captured in the first section. By performing the aliasing capture concurrently and immediately, the system minimizes the time during which aliasing signals can deteriorate, thereby reducing noise while maintaining readout flexibility.
Solution Approach 2:
The system uses feedback by utilizing the aliasing signal captured in the second accumulation section to correct the image signal from the first accumulation section. The correction section processes both signals, using the aliasing information as feedback to subtract and eliminate noise components, thus improving signal quality while preserving operational flexibility.
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 enables the production of images with simultaneous accumulation periods across all pixels, maintaining resolution and correcting aliasing signals without sacrificing the number of effective pixels, thus improving image quality and fidelity.
Implementation Method 1
Each of the unit pixels includes an opto-electric conversion device. The opto-electric conversion device carries out an opto-electric conversion process to convert incident light into signal electric charge
Data Source
AI summary
Disclosed herein is a solid-state image taking apparatus, includes: a pixel array section including unit pixels laid out two-dimensionally to form a matrix to serve as unit pixels each employing an opto-electric conversion device, a transfer transistor, a first electric-charge accumulation section, a read transistor, a second electric-charge accumulation section, a reset transistor, and an amplification transistor; a driving section; and a correction section.