ToF Pixel Charge Routing for Cover Glass Reflection Suppression
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Solution Overview
Problem
Existing ToF imaging systems face accuracy issues due to interfering elements like cover glass reflecting infrared light, causing mixed measurements and impairing depth sensing.
Innovation Solution
A ToF imaging system with a photonic mixer device using photo-sensitive elements and a drain gate to direct charge carriers, allowing control signals to manage charge distribution to suppress stray light and improve depth imaging behind cover glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sensor is placed underneath the cover glass to enable face recognition, then the device can perform depth imaging for authentication, but the infrared light is reflected by the glass causing mixed measurements and impaired depth accuracy
Solution Approach 1:
The photo-sensitive element is segmented into multiple charge storage regions (first element, second element, and gate) that can independently collect charge carriers. This segmentation allows the system to separate reflected light signals from the cover glass from direct light signals, enabling the drain gate to discard unwanted reflected charges while retaining useful depth measurement data.
Solution Approach 2:
The invention extracts and removes the harmful reflected light signals by providing a dedicated drain gate that collects and discards charge carriers generated by reflected infrared light from the cover glass. This extraction process separates the harmful reflection component from the useful depth measurement component, allowing accurate depth imaging to proceed despite the presence of the cover glass.
2Measurement precision
If a drain gate is added to direct charge carriers to suppress stray light, then depth measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The drain gate is merged with the existing photonic mixer device structure, integrating the stray light suppression function into the standard pixel architecture. Rather than adding a completely separate component, the drain gate is combined with the charge storage elements, allowing the system to suppress reflected light while maintaining a compact and efficient device structure.
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 system effectively suppresses stray light reflections from cover glass, enhancing depth measurement accuracy by directing charge carriers to a drain gate, thereby improving depth sensing performance.
Implementation Method 1
charge carriers generated in the photo-sensitive elements by received light
Data Source
AI summary
A time-of-flight (ToF) imaging system includes a photonic mixer device configured to perform ToF measurements using at least one photo-sensitive element. Each photo-sensitive element includes at least a first element with a modifiable first charge level, a second element with a modifiable second charge level, and a gate for transferring charges to a fixed potential. The ToF imaging system includes control circuitry configured to provide a control signal for the photonic mixer device. The control signal is configured to drive the at least one photo-sensitive element such that charge carriers generated in the at least one photo-sensitive element by received light are directed either to the first element, the second element or the gate, or such that charge carriers generated in the at least one photo-sensitive element by received light are directed either to the first element, the second element, the gate, or to the first and the second element.