Pixel Circuit Drain Switching for Wide Dynamic Range Readout

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Solution Overview

Problem

Existing solid-state imaging devices face challenges in achieving a wide dynamic range for exposure radiation and fast image capturing while maintaining high noise performance.

Innovation Solution

The implementation of a pixel circuit with a charge storage structure and an amplification transistor, where the potential at the storage node controls the amplification transistor, and an amplifier drain circuit that transitions from a low potential to a high potential only after the reset period and before the readout period, enhancing the dynamic range without significantly increasing noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the pixel capacitance is increased to widen the dynamic range, then the light sensitivity range is improved, but the image capturing speed decreases due to longer integration time required

Engineering Contradiction:

Improvedynamic rangeVSAvoidimage capturing speed

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent applies dynamics by making the load potential variable rather than fixed. The amplifier drain circuit dynamically switches between a first potential (during reset) and a second potential (during readout), allowing the pixel circuit to adapt its operating characteristics. This dynamic adjustment enables the circuit to achieve both wide dynamic range and fast capturing speed by optimizing the load conditions at different operational phases.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the electrical parameter (load potential) of the amplifier drain line to resolve the contradiction. By transitioning the load potential from a first value during reset to a second value during readout, the circuit modifies its electrical characteristics to simultaneously achieve wide dynamic range (through appropriate potential selection) and fast image capturing (through optimized charge transfer conditions).

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the pixel circuit is optimized for fast image capturing, then the image capturing rate is improved, but the noise performance deteriorates

Engineering Contradiction:

Improveimage capturing rateVSAvoidnoise performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by performing the reset operation before the readout phase. The amplifier drain circuit is set to the first potential during the reset period to properly initialize the pixel circuit and reset the charge storage node. This preliminary resetting action ensures that when fast readout occurs, the circuit starts from a known clean state, preventing noise accumulation and maintaining noise performance even at high capturing rates.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements periodic action through the alternating reset and readout phases. The amplifier drain circuit periodically switches between the first potential (reset phase) and second potential (readout phase). This periodic cycling allows the circuit to maintain low noise levels through regular resetting while achieving fast continuous image capturing through the efficient readout phase.

Inventive Principle:

Principle #19Periodic action

3Speed

If the amplifier drain circuit transitions potential early, then the readout speed is improved, but the reset operation is compromised leading to increased noise

Engineering Contradiction:

Improvereadout speedVSAvoidnoise performance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent uses dynamics to control the timing of potential transitions in the amplifier drain circuit. The circuit is designed to maintain the first potential throughout the entire reset period, then transition to the second potential only after reset is complete and before readout begins. This dynamic timing control ensures that the readout can proceed at high speed once initialized, while the reset operation completes fully without interference, maintaining noise performance.

Inventive Principle:

Principle #15Dynamics

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 increases the dynamic range of the pixel circuit, allowing for wider light sensitivity and faster image capturing with improved noise performance.

Implementation Method 1

photoelectric conversion element configured to generate a detector current signal in response to incident radiation

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS12526544B2Image sensor assembly, solid-state imaging device and time-of-flight sensor assembly

Publication Date: 2026.01.13 SONY SEMICON SOLUTIONS CORP

AI summary

An image sensor assembly includes a pixel circuit including a charge storage structure and an amplification transistor. A load path of the amplification transistor is between an amplifier drain line and a pixel output node. A potential at a storage node of the charge storage structure controls the amplification transistor. An amplifier drain circuit is configured to pass a low potential to the amplifier drain line in a reset period and a high potential in a readout period. A transition from the low potential to the high potential is not before an end of the reset period and prior to a start of the readout period.