1T Pixel Image Sensor Noise Reduction via Reference Current Comparison

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Solution Overview

Problem

Current image sensors with 1T pixels lack detailed sensing methods, leading to inefficiencies in sensing pixel signals and noise removal.

Innovation Solution

An image sensor system that generates pixel signals based on incident light intensity and compares them with reference currents to produce digital signals, using a cell array with 1T pixels and reference cells, and a readout block to remove noise and generate digital pixel signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If 1T pixels are used instead of 4T pixels, then pixel size is reduced, but sensing precision and noise removal capability deteriorate

Engineering Contradiction:

Improvepixel sizeVSAvoidsensing precision

Core Design Contradiction:

Area of moving objectVSMeasurement precision

Solution Approach 1:

The pixel array is divided into multiple ranks that can be controlled independently. Each rank can be read out separately through the shared readout circuit, allowing parallel processing and reducing the burden on individual pixels while maintaining small pixel size

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Reference cells are introduced as intermediary elements that generate reference currents for comparison with pixel signals. These reference cells act as mediators to improve the precision of pixel signal sensing without increasing pixel size, as the comparison mechanism enables more accurate measurement of the small signals from compact 1T pixels

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If 1T pixels are used instead of 4T pixels, then device complexity is reduced, but sensing speed and processing efficiency deteriorate

Engineering Contradiction:

Improvetransistor count per pixelVSAvoidsensing speed

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The cell array is segmented into multiple ranks that can be controlled and read out independently. This segmentation allows parallel readout operations, where multiple ranks can be processed simultaneously through the shared readout circuit, thereby increasing overall sensing speed despite the simplified 1T pixel structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Reference currents are generated in advance by the reference cells before pixel signal comparison. This preliminary generation of reference currents enables faster comparison operations and reduces the time required for each pixel readout, thereby improving sensing speed without adding complexity to the pixel structure

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If simple 1T pixel structure is used, then manufacturing ease is improved, but noise removal capability deteriorates

Engineering Contradiction:

Improvepixel fabricationVSAvoidnoise

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

Reference cells serve as intermediary elements that generate clean reference currents free from photogenerated noise. By comparing pixel signals against these noise-free reference currents, the system effectively removes noise from the pixel signals while maintaining the simple 1T pixel structure that is easy to manufacture

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the parameter being measured by comparing current levels rather than directly measuring voltage signals from pixels. This parameter transformation from voltage to current comparison enables more effective noise removal, as the reference current provides a stable baseline for subtracting noise components from pixel signals

Inventive Principle:

Principle #35Parameter changes

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 allows for precise and efficient sensing of pixel signals, reducing noise and improving the speed of image sensing by controlling the cell array by ranks, resulting in enhanced image processing capabilities.

Implementation Method 1

generating the pixel signal may include: removing photogenerated charges from a photodiode; accumulating photogenerated charges corresponding to the intensity of the incident light on the photodiode

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS9462199B2Image sensors, image processing systems including same, and methods of operating the same

Publication Date: 2016.10.04 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of operating an image sensor includes: generating a pixel signal according to intensity of incident light; and generating a digital pixel signal based on a comparison between the pixel signal and at least one reference current. Accordingly, a current output from a 1T pixel in the image sensor is sensed such that the influence of noise is reduced and a pixel signal is sensed more precisely.