CMOS Image Sensor Pixel Array Segmentation for Color Mismatch

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Solution Overview

Problem

In miniaturized CMOS image sensors, the shared pixel structure for two photodiodes to share one readout circuit leads to color mismatch issues when using the 2RSR scheme for high frame rates, due to restrictions in pixel charge transmission and A/D conversion time.

Innovation Solution

The image sensor design includes a pixel array with unit pixel areas that have first and second photo-electric conversion devices sharing a readout circuit, with each unit pixel area configured to output signals through different column lines based on odd and even readout signals, ensuring that photoelectrons of different colors are transmitted and output through distinct column lines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If a shared pixel structure is used to reduce unit pixel area, then the area of switch transistors per unit pixel is reduced, but color mismatch occurs when using 2RSR scheme for high frame rates

Engineering Contradiction:

Improveunit pixel areaVSAvoidcolor matching accuracy

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The pixel array is divided into first and second pixel arrays, where each array is dedicated to a specific color channel. This segmentation ensures that pixels of the same color share column lines, eliminating color mismatch while maintaining the shared readout circuit structure for area reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel array are assigned different color functions. Specifically, the first pixel array is dedicated to a first color and the second pixel array to a second color, allowing each region to have optimized characteristics for its specific color while maintaining overall system efficiency.

Inventive Principle:

Principle #3Local quality

2Productivity

If 2RSR scheme is used to achieve high frame rate, then the readout speed is improved, but color mismatch occurs due to restrictions in pixel charge transmission and A/D conversion time

Engineering Contradiction:

Improveframe rateVSAvoidcolor matching accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The pixel array is segmented into first and second pixel arrays corresponding to different color channels. Each array can be read out through dedicated column lines, allowing simultaneous readout of different color rows without color mixing, thus achieving high frame rate while maintaining color accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Column lines serve as intermediaries that are specifically assigned to transmit signals from pixels of the same color. This intermediary structure ensures that charge transmission and A/D conversion can proceed without color interference, enabling the 2RSR scheme to achieve high frame rates without color mismatch.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If two photodiodes share one readout circuit, then the number of readout circuits is reduced, but mismatch may occur between colors when they share the same column line

Engineering Contradiction:

Improvenumber of readout circuitsVSAvoidcolor matching accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Pixels sharing a readout circuit are segmented into different color groups, with each group assigned to specific column lines. This allows multiple photodiodes to share a readout circuit without color mismatch, as long as they transmit through color-dedicated column lines.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The readout circuit is designed to handle multiple color channels universally, but with the constraint that each color channel uses its dedicated column lines. This multi-functional readout circuit can serve multiple photodiodes of different colors while maintaining color accuracy through selective column line assignment.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration effectively suppresses color mismatch by ensuring that different colors are output through separate column lines during simultaneous readout, enhancing the accuracy and reliability of image capture in miniaturized CMOS image sensors.

Implementation Method 1

first and second photo-electric conversion devices sharing the readout circuit

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS9232161B2Unit pixels configured to output different pixel signals through different lines and image sensors including the same

Publication Date: 2016.01.05 SAMSUNG ELECTRONICS CO LTD

AI summary

An image sensor includes a pixel array and a plurality of pairs of column lines. The pixel array includes a plurality of unit pixel areas arranged in a plurality of rows and columns. Each of the unit pixel areas includes a readout circuit connected to a corresponding pair of column lines, and first and second photo-electric conversion devices sharing the readout circuit. Each of the unit pixel areas is configured to output a first pixel signal corresponding to a photoelectron generated by the first photo-electric conversion device through the first column line, and to output a second pixel signal corresponding to a photoelectron generated by the second photo-electric conversion device through the second column line.