Image Sensor Pixel Circulation Gates for Time of Flight Distance Measurement
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Solution Overview
Problem
Current image sensing devices face challenges in accurately measuring distance using the time of flight (TOF) principle due to limitations in effectively analyzing the time delay or phase shift between illumination and reflection, which affects the precision of distance calculation between the sensor and target objects.
Innovation Solution
The image sensing device incorporates a pixel array with circulation gates and transfer gates that separately control the movement and transfer of charge carriers, allowing for a more precise analysis of the time delay by generating and changing electric fields, thereby improving the accuracy of distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional image sensing devices use simple photoelectric conversion elements, then the device structure remains simple, but the precision of distance measurement using TOF principle deteriorates due to inability to effectively analyze time delay or phase shift
Solution Approach 1:
The pixel structure is segmented into multiple functional regions including photoelectric conversion elements, circulation gates, transfer gates, and floating diffusion regions. This segmentation allows independent control of charge carrier movement and transfer, enabling precise time delay analysis for TOF measurement while maintaining manageable structural complexity through modular design
Solution Approach 2:
The circulation gates are configured to dynamically change electric fields in different regions of the photoelectric conversion element based on circulation control signals. This dynamic control enables precise manipulation of charge carrier movement patterns, allowing accurate time delay or phase shift analysis for improved distance measurement precision
2Measurement precision
If circulation gates are added to control charge carrier movement, then the precision of time delay analysis is improved, but the device complexity increases due to additional gate structures and control signals
Solution Approach 1:
The circulation gates serve multiple functions: they create electric fields in different regions of the photoelectric conversion element, induce movement of charge carriers, and enable time delay analysis. This multi-functionality reduces the need for separate dedicated structures, thereby limiting the increase in device complexity while improving time delay analysis precision
3Productivity
If transfer gates are introduced to move charge carriers to floating diffusion regions, then the operational characteristics are enhanced, but the manufacturing complexity increases
Solution Approach 1:
The transfer gates are integrated with the circulation gate structure, and the floating diffusion regions are combined with the photoelectric conversion element array. This merging of functions and structures reduces the number of discrete components, thereby improving operational efficiency while limiting the increase in manufacturing complexity
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 enhances the operational characteristics of the image sensing device by enabling more effective analysis of the time delay, leading to improved precision in distance measurement between the sensor and target objects.
Implementation Method 1
a photoelectric conversion element to generate charges carriers by converting light incident upon the photoelectric conversion element
Implementation Method 2
configured to create an electric field in different regions of the photoelectric conversion element based on circulation control signals, and configured to induce movement of the charge carriers
Data Source
AI summary
The image sensing device includes a pixel array including a plurality of unit pixels is arranged in rows and columns. Each of the plurality of unit pixels includes a photoelectric conversion element to generate charge carriers by converting light incident upon the photoelectric conversion element, a plurality of floating diffusion regions spaced apart from the photoelectric conversion element to hold the charge carriers, a plurality of circulation gates located at sides of the photoelectric conversion element in each of a first direction and a second direction perpendicular to the first direction, configured to create an electric field in different regions of the photoelectric conversion element based on circulation control signals, and configured to induce movement of the charge carriers, and a plurality of transfer gates located between the circulation gates, and configured to transfer the charge carriers generated by the photoelectric conversion element to a corresponding floating diffusion region.