Pixel Array Reset Method Using Dual Charge Transfer

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Solution Overview

Problem

Existing reset methods for sensor pixel arrays fail to precisely control reset timing, leading to inaccuracies in output integrated electric charge and introducing noise such as KTC noise, which affects the quality of the output signal.

Innovation Solution

A reset method and device that utilize an electric charge accumulation unit and an electric charge storage unit with opposite polarities, where the control module manages the transfer of a preset amount of electric charge from the storage unit to the accumulation unit, ensuring precise voltage changes and reducing noise during the reset process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a reset voltage is used to detect and reset pixels, then the reset process can be initiated, but the reset timing cannot be precisely controlled

Engineering Contradiction:

Improvereset timing precisionVSAvoidoutput signal accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the conventional voltage-based reset control system with a dual-charge transfer system. Instead of using voltage detection and threshold comparison, the system uses precise control of electron charge transfer between capacitors. The first charge transfer unit transfers a first charge to the floating diffusion, and the second charge transfer unit transfers a second charge (with opposite polarity) to the same node. This charge-based control mechanism provides much higher precision in timing control compared to voltage detection, as the charge transfer amount can be precisely controlled by the switching timing of the transfer units.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If early or delayed reset timing occurs, then the reset process completes, but the integrated electric charge amount becomes inaccurate

Engineering Contradiction:

Improvereset operation completionVSAvoidintegrated electric charge accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the control unit monitors the integration process and precisely controls the timing of the second charge transfer. The control unit receives signals about the integration status and adjusts the timing of the second charge transfer to occur at the exact moment when the first charge from the photodetector has been fully integrated. This feedback-based timing control ensures that the reset operation completes while maintaining accurate measurement of the integrated electric charge, preventing both early and delayed reset errors.

Inventive Principle:

Principle #23Feedback

3Ease of operation

If conventional reset control is used, then the circuit can be reset, but image trailing occurs in after-reset pixels

Engineering Contradiction:

Improvereset operationVSAvoidimage trailing

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by transferring the second charge (with opposite polarity) to the floating diffusion node at a precisely controlled time just before or at the moment of reset. This preliminary charge transfer prepares the floating diffusion node to quickly and cleanly discharge any residual charge from previous integration cycles. By having this opposing charge ready and transferring it at the precise moment, the system ensures that after-reset pixels are cleanly reset without retaining any image information from before-reset pixels, thereby eliminating image trailing while maintaining ease of reset operation.

Inventive Principle:

Principle #10Preliminary action

4Productivity

If reset voltage detection method is used, then the reset process can proceed, but KTC noise is introduced

Engineering Contradiction:

Improvereset process executionVSAvoidKTC noise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the voltage-based reset detection and control mechanism with a charge-based mechanism. Instead of detecting voltage thresholds and using operational amplifiers or comparators that introduce KTC noise, the system uses controlled charge transfer between capacitors. The reset control is achieved by controlling the timing and amount of charge transfer from the second charge transfer unit, which has opposite polarity to the signal charge. This charge transfer approach eliminates the need for high-impedance voltage detection circuits and amplifiers, thereby eliminating the source of KTC noise while maintaining productive reset process execution.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11451729B2Reset method, reset device, and reset system and pixel array using the same

Publication Date: 2022.09.20 NINGBO ABAX SENSING ELECTRONICS TECH CO LTD

AI summary

The embodiments of the present disclosure provide a reset method, a reset device, a reset system and a pixel array using the same. The reset method includes an electric charge accumulation unit being configured to store a first electric charge and an electric charge storage unit being configured to store a second electric charge. A polarity of the first electric charge is opposite to a polarity of the second electric charge. The reset method includes controlling the electric charge storage unit to obtain the second electric charge; and resetting the electric charge accumulation unit so as to transfer a preset amount of the second electric charge from the electric charge storage unit to the electric charge accumulation unit, which includes a third port of the control module applying a control voltage to a second end of the electric charge storage unit; and meanwhile charging the electric charge storage unit during the process of transferring the second electric charge.