2D TDI CMOS Image Sensor for UAV Vibration Noise Reduction
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Solution Overview
Problem
Conventional CMOS image sensors struggle with low signal-to-noise ratio due to wind and mechanical vibrations in UAVs, especially with moving scene imagery, as they are limited to one-dimensional Time Delay Integration (TDI) and accumulate additional noise.
Innovation Solution
A two-dimensional time delay integration CMOS image sensor is developed, utilizing a first and second pinned photodiode with a series of electrodes for charge transfer, and a grid configuration of readout nodes and address lines to move charge at the same speed as the image, improving signal integration and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CMOS image sensors are used in UAVs, then the device complexity is low and ease of manufacture is good, but the signal to noise ratio deteriorates due to wind and mechanical vibrations
Solution Approach 1:
The patent transitions from conventional one-dimensional TDI to two-dimensional TDI by adding lateral charge transfer capability. Multiple pinned photodiodes are arranged in a 2D array with electrodes enabling charge movement in both vertical and lateral directions, allowing charge to follow the motion trajectory of moving scenes and significantly improving signal-to-noise ratio through enhanced integration capability.
Solution Approach 2:
The image sensor is divided into multiple pinned photodiodes arranged in an array, with each photodiode capable of independent charge collection and transfer. This segmentation enables parallel charge integration across multiple pixels, improving signal-to-noise ratio while maintaining CMOS manufacturing compatibility.
2Reliability
If one-dimensional TDI is implemented in CMOS, then the device complexity is moderate, but the signal to noise ratio improvement is less than proportional to the square root of the number of TDI channels due to additional noise accumulation
Solution Approach 1:
The patent converts the harmful effect of camera vibrations and scene motion into a beneficial charge transfer mechanism. By synchronizing charge movement with the direction and speed of scene motion, the system integrates multiple charge packets from the same spatial location over time, transforming vibration-induced charge displacement into enhanced signal integration and achieving signal-to-noise ratio improvement proportional to the number of TDI channels.
3Reliability
If CCDs with TDI are used, then the signal to noise ratio is improved, but the device complexity increases due to one-dimensional limitation and requirement for multiple chip systems
Solution Approach 1:
The patent merges multiple functional elements into a single integrated CMOS device. Multiple pinned photodiodes, charge transfer electrodes, and readout circuits are combined in one chip to form a complete two-dimensional TDI system, eliminating the need for multiple separate CCD chips and reducing overall device complexity while maintaining high signal-to-noise ratio performance.
4Measurement precision
If conventional CMOS sensors are used, then the ease of manufacture is good, but the measurement precision deteriorates with moving scene imagery due to low signal to noise ratio
Solution Approach 1:
The patent changes the operational parameters of the CMOS sensor by implementing time-delayed charge transfer synchronized with scene motion. The charge transfer timing and electrode activation sequences are optimized to match the velocity and direction of moving targets, enabling precise measurement of moving scenes while maintaining compatibility with standard CMOS manufacturing processes.
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 signal-to-noise ratio proportionally with the number of TDI channels, providing improved image clarity and stability against vibrations, enabling high frame rates and accurate target identification.
Implementation Method 1
the first pinned photodiode collects a charge when light strikes the first pinned photodiode
Implementation Method 2
a plurality of electrodes in series located between the first and the second pinned photodiodes, the plurality of electrodes are configured to transfer the charge from the first pinned photodiode to the second pinned photodiode
Data Source
AI summary
A two dimensional time delay integration CMOS image sensor having a plurality of pinned photodiodes, each pinned photodiode collects a charge when light strikes the pinned photodiode, a plurality of electrodes separating the plurality of pinned photodiodes, the plurality of electrodes are configured for two dimensional charge transport between two adjacent pinned photodiodes, and a plurality of readout nodes connected to the plurality of pinned photodiodes via address lines.