Ranging Sensor Transfer Gate Drive Circuit for Accuracy
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Solution Overview
Problem
Variations in circuit characteristics within ranging sensors affect the accuracy of ranging results, particularly in indirect time-of-flight methods where charge transfer and accumulation processes are critical.
Innovation Solution
The ranging sensor design includes multiple transfer gates and storage nodes to manage charge transfer and accumulation, with a transfer gate drive unit controlling the gates to ensure balanced and accurate charge distribution across different paths, using ON/OFF control and negative bias driving to minimize unintended charge accumulation and characteristic differences between transfer gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple reading circuits are used for different floating diffusion regions, then charge reading capability is improved, but variation in circuit characteristics affects ranging accuracy
Solution Approach 1:
The patent merges multiple charge accumulation paths into a single shared reading circuit. Specifically, first and second floating diffusion regions accumulate charge from different transfer gates (third and fourth transfer gates), but both share a common reading circuit including a single amplifier and readout path. This eliminates the variation problems caused by having separate reading circuits while maintaining the ability to read charge from multiple accumulation regions.
2Adaptability or versatility
If multiple transfer gates are used to accumulate charge in different paths, then charge distribution flexibility is improved, but characteristic differences between transfer gates affect measurement precision
Solution Approach 1:
The patent combines multiple charge accumulation paths that use different transfer gates into a unified reading system. The first transfer gate transfers charge to the first floating diffusion region, while the second transfer gate transfers charge to the second floating diffusion region, but both regions share the same reading circuit. This allows flexible charge distribution through multiple transfer paths while eliminating measurement errors caused by transfer gate characteristic differences.
Solution Approach 2:
The patent introduces floating diffusion regions as intermediary nodes between transfer gates and the reading circuit. These floating diffusion regions serve as charge holding nodes that decouple the transfer gates from the reading circuit, allowing multiple transfer gates with different characteristics to feed into a single standardized reading path, thereby mediating the characteristic differences.
3Quantity of substance
If charge is accumulated in multiple floating diffusion regions, then charge accumulation capacity is improved, but complexity of reading circuits increases
Solution Approach 1:
The patent merges the reading functions for multiple floating diffusion regions into a single shared reading circuit. Instead of providing separate amplifiers and readout paths for each floating diffusion region, the invention uses one common amplifier and readout circuit that can sequentially or selectively read charge from either the first or second floating diffusion region, significantly reducing circuit complexity while maintaining full charge accumulation capacity.
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 approach enhances the accuracy of ranging results by offsetting characteristic differences in transfer gates, improving the precision of distance information generation and reducing noise, thereby improving the overall performance of the ranging sensor.
Implementation Method 1
a photoelectric conversion element that receives reflected light of light emitted by a light emitter
Data Source
AI summary
A ranging sensor includes a pixel including a photoelectric conversion element, a first storage node and a second storage node that store charge transferred from the photoelectric conversion element, a first transfer gate and a second transfer gate connected to the photoelectric conversion element so as to branch and transfer the charge generated in the photoelectric conversion element to different paths, a third transfer gate connected between the first storage node and the first transfer gate, a fourth transfer gate connected between the second storage node and the second transfer gate, a fifth transfer gate connected between the first storage node and the second transfer gate, and a sixth transfer gate connected between the second storage node and the first transfer gate, the ranging sensor including a transfer gate drive unit that drives each of the first to sixth transfer gates.