SPAD Focal Plane Readout Circuit for Uniformity and Light Protection
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Solution Overview
Problem
The existing single photon avalanche focal plane faces issues with non-uniform photon detection, sensitivity to strong light leading to performance degradation and chip damage, and interference from background light, limiting its application in complex environments with high spatial resolution and frame rate requirements.
Innovation Solution
A multifunctional readout circuit with a pixel array, uniformity correction, and adaptive imaging modes that adjust bias voltage and protect against strong light, enabling regional and global corrections to enhance imaging uniformity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the photosensitive array is expanded to increase detection area, then the coverage and detection capability are improved, but the uniformity of photon detection deteriorates due to material and process deviations
Solution Approach 1:
The patent divides the photosensitive array into multiple regions with independently adjustable bias voltages. By applying different bias voltages to different regions, the system compensates for local variations in detection uniformity caused by material and process deviations, allowing each region to be optimized independently while maintaining overall array functionality.
Solution Approach 2:
The patent dynamically adjusts the bias voltage parameter across different regions of the photosensitive array based on detected uniformity characteristics. This parameter adjustment compensates for manufacturing variations and maintains consistent photon detection performance across the expanded array area.
2Measurement precision
If the optical array chip operates in high sensitivity mode to detect single photons, then the detection sensitivity is improved, but the chip becomes vulnerable to strong light causing temperature rise and performance degradation
Solution Approach 1:
The patent implements dynamic switching between different operating modes (single photon detection mode and strong light protection mode) based on the incident light conditions. The system can adaptively adjust its sensitivity and bias voltage in real-time, allowing it to operate at high sensitivity when appropriate while protecting against damage from strong light through rapid mode transitions.
Solution Approach 2:
The patent employs preliminary protective measures by monitoring incident light levels and preemptively switching to protection mode before strong light can cause temperature rise or damage. The system detects potential harmful conditions and takes preventive action by adjusting bias voltages and switching modes before damage occurs.
3Device complexity
If a conventional single-echo readout circuit is used to simplify the readout structure, then the device complexity is reduced, but background light causes large numbers of false triggers reducing signal-to-noise ratio
Solution Approach 1:
The patent implements a multi-functional readout circuit that can operate in multiple modes (single-echo, multi-echo, and photon counting modes) depending on the detection requirements. This universal readout circuit maintains relatively simple structure while achieving high reliability by selecting the appropriate operating mode based on background light conditions and detection needs.
Solution Approach 2:
The readout circuit dynamically switches between different operating modes to optimize performance under varying background light conditions. By adapting its operation mode in real-time, the system maintains high signal-to-noise ratio without requiring a permanently complex circuit 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
Improves photon detection efficiency by 30% and increases the strong light threshold, allowing operation in diverse environments with high spatial resolution and frame rates, protecting the array from damage, and reducing false triggers.
Implementation Method 1
A photosensitive array thereof adopts a single photon avalanche diode array working in a 'Geiger mode'
Data Source
AI summary
A readout circuit of a single photon avalanche focal plane includes a pixel array circuit, a serial bus circuit, a clock and timing control circuit, a working mode control circuit, a clock generation circuit, temperature sensing circuits, data processing and storage circuits, I/O driving circuits, and a uniformity correction circuit. The pixel array circuit includes pixel unit circuits arranged in an array. The uniformity correction circuit is configured to improve imaging uniformity by performing regional offset adjustment on the pixel array circuit. By adjusting pixels in abnormal areas or a global bias voltage through uniformity correction, a scale of an array of the pixel array circuit is improved, and an SPAD array chip is protected from strong light, so that the readout circuit well meets application scenarios with complex environmental information, high spatial resolution ratio and high imaging frame rate.