SPAD Image Sensor Layout With Adjacent Pixel Photon Validation
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Solution Overview
Problem
Existing high spatial resolution solid-state image sensors face challenges in distinguishing between photons belonging to the detected light beam and background photons, leading to statistical noise and reduced precision in distance measurement, and require increased sensitive surface area for improved spatial resolution.
Innovation Solution
The image sensor design incorporates a logic unit and avalanche photodiode on a semiconductor substrate, with each pixel generating a unique trigger signal upon photon detection and confirming photon arrival through adjacent pixel validation within a predefined time window, enhancing spatial resolution without increasing physical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If each pixel generates independent electrical signals upon photon detection, then spatial resolution is maintained at pixel level, but statistical noise increases due to inability to distinguish signal photons from background photons
Solution Approach 1:
The system implements feedback by having each pixel's detection event trigger a validation query to neighboring pixels. The central pixel's signal is confirmed or rejected based on the responses from adjacent pixels within a predefined time window, creating a feedback loop that validates photon detection reliability
Solution Approach 2:
Neighboring pixels act as intermediaries that validate the detection events of the central pixel. Instead of direct independent detection, the system uses adjacent pixels as mediators to confirm whether detected photons are genuine signal photons or background noise through coordinated validation
2Reliability
If multiple avalanche photodiodes are connected per pixel to provide single proportional signal, then background photon discrimination improves, but spatial resolution decreases due to macropixel formation
Solution Approach 1:
The system segments the validation function from the detection function. Each pixel remains a独立的 detection unit maintaining spatial resolution, while the validation function is segmented and performed collaboratively by neighboring pixels through inter-pixel communication rather than combining multiple photodiodes into macropixels
3Device complexity
If independent pixel detection is used, then device complexity is reduced, but noise filtering capability is lost
Solution Approach 1:
The pixel array performs self-validation through inter-pixel communication. Each pixel independently detects photons but collectively validates detections through neighboring pixel responses, allowing the system to self-filter noise without external processing circuits or complex additional components
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 increases the spatial resolution and accuracy of photon detection by validating photon arrivals within a time window, reducing noise and improving precision while maintaining the same sensitive surface area, thereby enhancing the reliability of distance measurements.
Implementation Method 1
Each of the aforesaid pixels, in the single-photon implementations, comprises a reverse biased avalanche photodiode, also known as SPAD (Single-Photon Avalanche Diode), with responds independently from the others by emitting an elemental charge pack upon detection of a photon
Implementation Method 2
Each of the aforesaid pixels, in the single-photon implementations, comprises a reverse biased avalanche photodiode, also known as SPAD (Single-Photon Avalanche Diode)
Data Source
AI summary
A solid-state image sensor for detecting one or more photons includes a plurality of pixels sensitive to such photons, each of the pixels having a logic unit and an avalanche photodiode operatively connected to the logic unit, the logic unit being configured to provide an electrical signal different from the electrical signals provided by the logic units of the remaining pixels. The logic unit of each of the pixels is operatively connected to the logic unit of an adjacent pixel, such logic unit outputting the electrical signal when the avalanche photodiode belonging to the same pixel and the avalanche photodiode belonging to such adjacent pixel each detect at least one photon within a time window.