Pixel Circuit Pulse-Width Output for Analog Time-Difference Sensing

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Solution Overview

Problem

Conventional optical sensors require digital frame buffers to store pixel data, necessitating two frame buffers and limiting operations to the digital backend, whereas performing operations at the analog phase could be more efficient.

Innovation Solution

A pixel circuit that uses pulse width signals to represent detected light intensity and perform operations, including intra-pixel and inter-pixel operations, by employing a photodiode, transfer transistor, and temporal circuits with capacitors to store and convert light energy into detection signals, allowing analog operations without initial digital conversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If digital frame buffers are used to store pixel data, then data storage capability is improved, but device complexity and memory requirements increase

Engineering Contradiction:

Improvedata storage capabilityVSAvoiddevice complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent extracts the data storage function from the digital backend and implements it directly in the pixel circuit at the analog phase. The pixel circuit itself stores pixel data in analog form using capacitors, eliminating the need for separate digital frame buffers and reducing overall device complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an analog signal processing intermediary between the photodiode and digital conversion. By performing operations on analog signals before digital conversion, the system avoids the need for large digital frame buffers, reducing memory requirements while maintaining data storage capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If operations are performed in digital backend, then processing reliability is improved, but processing speed and efficiency deteriorate

Engineering Contradiction:

Improveprocessing reliabilityVSAvoidprocessing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent performs pixel-wise operations in the analog phase before digital conversion. By conducting additions, subtractions, and other operations on analog signals prior to ADC, the system achieves faster processing efficiency while maintaining reliability through subsequent digital verification.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a periodic switching mechanism that alternates between analog operations (for high-speed processing) and digital operations (for high-reliability processing). This periodic action allows the system to leverage the speed of analog processing while maintaining the reliability of digital processing at appropriate intervals.

Inventive Principle:

Principle #19Periodic action

3Duration of action of stationary object

If two frame buffers are used to store pixel data, then data retention capability is improved, but area and power consumption increase

Engineering Contradiction:

Improvedata retention capabilityVSAvoidarea

Core Design Contradiction:

Duration of action of stationary objectVSArea of stationary object

Solution Approach 1:

The patent merges the data storage function into the pixel circuit itself. By integrating analog storage capacitors within each pixel circuit, the system eliminates the need for separate frame buffer memory structures, significantly reducing the area required while maintaining data retention capability through the holding capacitor.

Inventive Principle:

Principle #5Merging (Combining)

4Speed

If analog operations are performed, then processing speed is improved, but signal precision and noise immunity worsen

Engineering Contradiction:

Improveprocessing speedVSAvoidsignal precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent implements feedback mechanisms where analog operation results are continuously monitored and corrected. By using feedback loops that adjust analog signals based on reference comparisons and error correction, the system maintains high signal precision during fast analog processing operations.

Inventive Principle:

Principle #23Feedback

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

Enables efficient pixel-wise analog operations, reducing the need for digital frame buffers and allowing operations to be performed directly in the analog phase, enhancing processing efficiency and data handling in optical sensors.

Implementation Method 1

a photodiode, a transfer transistor, a first node configured to store light energy from the photodiode

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS20250024172A1Pixel circuit selecting to output time difference data or image data

Publication Date: 2025.01.16 PIXART IMAGING INC

AI summary

There is provided a pixel circuit capable of outputting time difference data or image data, and including a first temporal circuit and a second temporal circuit. The first temporal circuit is used to store detected light energy of a first interval and a second interval as the time difference data. The second temporal circuit is used to store detected light energy of the second interval as the image data. The pixel circuit is used to output a pulse width signal corresponding to the time difference data or the image data in different operating modes.