ToF Depth Sensor Pixel Structure for Lower Error and Drive Current
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Solution Overview
Problem
Existing depth sensors face errors in object distance calculation due to internal structural limitations, necessitating a solution to minimize these errors and reduce driving current while maintaining accurate time of flight (ToF) calculations.
Innovation Solution
A depth sensor design incorporating a pixel structure with a first and second photo transistor, transfer transistors, and a switch to control voltage application, along with a substrate that applies a negative voltage during integration, allowing for accurate charge integration and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional pixel structure is used for depth sensing, then the device can perform basic ToF calculations, but errors in distance calculation occur due to structural limitations
Solution Approach 1:
The pixel is divided into multiple photo transistors (first photo transistor and second photo transistor) that operate with different photo gate signals. This segmentation allows separate charge integration paths that can be processed differently to eliminate systematic errors in ToF calculations, thereby improving measurement precision and reliability.
Solution Approach 2:
The invention applies a negative voltage to the substrate during the integration period, which changes the electrical parameters of the pixel structure. This parameter change optimizes charge collection efficiency and reduces errors in the ToF calculation, leading to improved distance measurement accuracy.
2Productivity
If high driving current is supplied to the row driver, then faster charge transfer and higher productivity are achieved, but power consumption increases
Solution Approach 1:
The row driver operates with periodic switching of transfer gate signals that synchronize with the integration periods. This periodic action allows the driver to transfer charges in controlled bursts rather than continuously, maintaining high transfer efficiency while reducing average power consumption.
Solution Approach 2:
The negative voltage applied to the substrate during integration modifies the electrical characteristics of the transistors, enabling more efficient charge transfer with lower current requirements. This parameter change reduces the power consumption of the row driver while maintaining productivity.
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 solution effectively minimizes errors in ToF calculations and decreases the driving current of the row driver, enhancing the reliability and efficiency of the depth sensor while reducing power consumption.
Implementation Method 1
a first photo transistor configured to integrate first charges based on a first photo gate signal that toggles during an integration period
Data Source
AI summary
A depth sensor and an image detecting system including the same are provided. The depth sensor includes a pixel that generates an image signal based on a sensed light. The pixel includes a first photo transistor that integrates first charges based on a first photo gate signal toggling during an integration period, a second photo transistor that integrates second charges based on a second photo gate signal toggling during the integration period, a first transfer transistor that transfers the first charges to a first floating diffusion node based on a first transfer gate signal, a second transfer transistor that transfers the second charges to a second floating diffusion node based on the first transfer gate signal, and a switch that is connected with the first photo transistor, the second photo transistor, the first transfer transistor, and the second transfer transistor.