Pixel Array Readout Circuit Arrangement for ToF Imaging

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Solution Overview

Problem

Time-of-flight (ToF) imaging techniques face challenges in achieving high resolution while minimizing power consumption, particularly in face recognition applications where high radiated power from planar light sources increases system power consumption and poses eye safety risks.

Innovation Solution

A pixel array with a structured light signal that forms separated light spots on the pixel array, utilizing a photodetector and readout circuit to detect and process reflected signals, and a processing circuit to calculate depth information, which reduces power consumption and enhances signal quality and resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a planar light source with uniform illumination is used to increase resolution and collect depth information of distant target objects, then imaging resolution is improved, but system power consumption increases and eye safety is compromised

Engineering Contradiction:

Improveimaging resolutionVSAvoidsystem power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent divides the uniform planar light source into multiple discrete light-emitting units arranged in an array. Each unit emits light independently, allowing selective activation and energy distribution across multiple zones, thereby reducing total power consumption while maintaining imaging resolution through the collective contribution of segmented light sources

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements non-uniform illumination by assigning different emission characteristics to different regions of the light-emitting array. Certain areas emit higher intensity light while others emit lower intensity, optimizing power distribution according to local imaging requirements and reducing overall power consumption compared to uniform illumination

Inventive Principle:

Principle #3Local quality

2Measurement precision

Engineering Contradiction:

Improveimaging resolutionVSAvoideye safety

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent segments the light source into multiple discrete units that can be independently controlled. This allows the system to distribute light emission across many low-intensity sources rather than using a single high-intensity source, reducing the risk of eye damage while maintaining sufficient total light for imaging resolution

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the illumination parameters by transitioning from uniform high-intensity illumination to non-uniform distributed illumination. By adjusting the intensity distribution across multiple light-emitting units, the system achieves required imaging resolution while keeping peak intensity below eye safety thresholds

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the pixel array uses a specific arrangement with readout circuits adjacent to photodetectors in perpendicular directions, then signal detection quality is enhanced, but device complexity increases

Engineering Contradiction:

Improvesignal detection qualityVSAvoidpixel array structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the readout circuit functionality into the pixel structure itself, with readout circuits positioned adjacent to photodetectors in perpendicular directions. This integration allows shared use of readout circuits across multiple photodetectors, reducing the total number of independent readout paths while enhancing signal detection quality through optimized signal routing

Inventive Principle:

Principle #5Merging (Combining)

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

The proposed solution achieves high-resolution imaging with reduced power consumption by concentrating energy and enhancing signal detection quality, while ensuring eye safety by minimizing the intensity of the light source.

Implementation Method 1

The photodetector is configured to detect the reflected signal and accordingly output a photo response signal

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

a time-of-flight (ToF) distance measuring technique calculates time of flight of the optical signal traveling from the transmitter side to the receiver side, thereby obtaining a distance between the target object and the transmitter/receiver side

Methodology Applied

Scientific EffectTime of Flight: Time of Flight

Data Source

PatentUS11442170B2Imaging system, pixel array of imaging system and image sensor

Publication Date: 2022.09.13 SHENZHEN GOODIX TECH CO LTD

AI summary

An image sensor including a pixel array which includes pixels for sensing a reflected signal, incident on the pixel array to form reflected light spots separated from each other. Each pixel includes a photodetector and a readout circuit. The photodetector is configured to detect the reflected signal and output a photo response signal. The readout circuit is configured to generate a pixel output according to the photo response signal. The pixels include a first pixel and a second pixel adjacent to the first pixel along a first predetermined direction. The readout circuit of the first pixel is adjacent to the photodetector of the second pixel along the first predetermined direction, and adjacent to the photodetector of the first pixel along a second predetermined direction perpendicular to the first predetermined direction. The pixel array has a small pixel pitch and a high fill factor.