Boosted Photodiode Time of Flight Sensor Architecture
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Solution Overview
Problem
Time of flight cameras face challenges in balancing performance parameters with physical size and power constraints, particularly in achieving real-time 3D image acquisition for both near and far objects, due to differences in power requirements and complexities related to frame rate, depth resolution, and sensor efficiency.
Innovation Solution
The implementation of a time of flight image sensor with boosted photodiodes that utilize both vertical and horizontal electric fields to increase the transfer speed of signal electrons, employing junction capacitance to accelerate electrons and reduce power consumption, with a low driving voltage and small physical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional time of flight systems use higher power requirements to improve measurement speed and range, then real-time 3D image acquisition performance is improved, but power consumption increases beyond acceptable limits for compact devices
Solution Approach 1:
The patent changes the electrical parameters of the photodiode by applying a boosted voltage (e.g., 3.3V or higher) during the transfer gate activation period. This voltage boost creates a stronger electric field that accelerates electron transfer from the photodiode to the storage node, thereby increasing the measurement speed and enabling real-time 3D image acquisition while keeping the overall system power consumption manageable through controlled timing of the voltage boost
2Area of moving object
If the sensor size is reduced to fit compact devices, then device portability is improved, but the ability to capture both near and far objects with sufficient depth resolution deteriorates
Solution Approach 1:
The patent applies different electrical conditions to different regions or time periods of the photodiode operation. By locally boosting the voltage during the critical transfer period and using different transfer gate timing for near and far object measurements, the system achieves high depth resolution for both near and far objects despite the small overall sensor size
3Speed
If multiple transfer gates are used to improve electron transfer efficiency, then measurement speed is improved, but device complexity increases
Solution Approach 1:
The patent uses periodic activation of transfer gates with different timing sequences. Multiple transfer gates are activated in a periodic manner during different time intervals within each frame period, allowing efficient electron transfer without requiring all gates to be active simultaneously, thus managing complexity while maintaining high transfer speed
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 speed and efficiency of time of flight measurements, reducing power consumption and enabling real-time 3D image acquisition in compact devices while maintaining performance parameters.
Implementation Method 1
a sensor that detects the light that is reflected from the object
Implementation Method 2
employing junction capacitance to accelerate electrons
Data Source
AI summary
An image sensor including a photodiode, a first doped region, a second doped region, a first storage node, a second storage node, a first vertical transfer gate, and a second vertical transfer gate is presented. The photodiode is disposed in a semiconductor material to convert image light to an electric signal. The first doped region and the second doped region are disposed in the semiconductor material between a first side of the semiconductor material and the photodiode. The first doped region is positioned between the first storage node and the second storage node while the second doped region is positioned between the second storage node and the first doped region. The vertical transfer gates are coupled between the photodiode to transfer the electric signal from the photodiode to a respective one of the storage nodes in response to a signal.