SPAD Array Dynamic Range Extension via Temporal Multiplexing
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Solution Overview
Problem
SPAD-based radiation sensors face limitations in dynamic range due to noise at low radiation levels and saturation at high levels, requiring large arrays of SPADs which increase circuitry complexity and device size, while existing solutions with pinholes and apertures result in poor signal-to-noise ratio and additional components.
Innovation Solution
A radiation-sensitive device using an array of SPADs with circuitry configured to measure incident radiation through multiple measurement windows of varying durations, allowing for a trade-off between signal-to-noise ratio and dynamic range by adjusting the measurement window based on radiation intensity, minimizing inactive SPADs and using single-bit counters to reduce device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large amount of SPADs is used to improve signal-to-noise ratio at low radiation levels, then the signal-to-noise ratio is improved, but the device complexity and size increase due to associated circuitry
Solution Approach 1:
Multiple SPADs are combined into a single pixel unit with shared circuitry. The pixel level generator and counter resources are merged and shared across multiple SPADs, reducing the overall circuitry complexity while maintaining the signal-to-noise ratio through temporal multiplexing of measurements.
Solution Approach 2:
The measurement window duration is dynamically adjusted based on radiation intensity levels. For low radiation levels, longer measurement windows are used to accumulate sufficient signal, while for high radiation levels, shorter windows prevent saturation. This dynamic adaptation allows accurate measurement across a wide dynamic range without requiring additional hardware.
2Measurement precision
If a large amount of SPADs is used to improve signal-to-noise ratio at low radiation levels, then the signal-to-noise ratio is improved, but the device size increases
Solution Approach 1:
Multiple SPADs are combined into a single pixel unit with shared circuitry. The pixel level generator and counter resources are merged and shared across multiple SPADs, reducing the overall circuitry complexity while maintaining the signal-to-noise ratio through temporal multiplexing of measurements.
Solution Approach 2:
The circuitry is designed to be universal and multi-functional, serving multiple SPADs within a pixel. The same counter and control logic are reused across different SPADs through time-multiplexed operation, eliminating the need for dedicated circuitry for each SPAD and thereby reducing device area.
3Adaptability or versatility
If different SPAD areas with pinholes are used to adjust radiation intensity, then the dynamic range is extended, but the device size increases and additional components are required
Solution Approach 1:
The measurement window duration is dynamically adjusted based on radiation intensity levels. For low radiation levels, longer measurement windows are used to accumulate sufficient signal, while for high radiation levels, shorter windows prevent saturation. This dynamic adaptation allows accurate measurement across a wide dynamic range without requiring additional hardware.
Solution Approach 2:
The system changes the measurement parameter (time window duration) to adapt to different radiation intensity levels. By varying the integration time rather than physical aperture size, the system achieves dynamic range extension through parameter modulation instead of structural modification, avoiding additional components.
4Adaptability or versatility
If different SPAD areas with pinholes are used to adjust radiation intensity, then the dynamic range is extended, but the device size increases
Solution Approach 1:
The measurement window duration is dynamically adjusted based on radiation intensity levels. For low radiation levels, longer measurement windows are used to accumulate sufficient signal, while for high radiation levels, shorter windows prevent saturation. This dynamic adaptation allows accurate measurement across a wide dynamic range without requiring additional hardware.
Solution Approach 2:
The system changes the measurement parameter (time window duration) to adapt to different radiation intensity levels. By varying the integration time rather than physical aperture size, the system achieves dynamic range extension through parameter modulation instead of structural modification, avoiding 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 extends the dynamic range of the radiation-sensitive device while maintaining an adequate signal-to-noise ratio, allowing for efficient detection of both low and high radiation levels without increasing device size or adding components, effectively overcoming the limitations of existing technologies.
Implementation Method 1
Single Photon Avalanche Diode (SPAD) based photon counters offer the ability to detect very low levels of radiation by counting individual photons
Implementation Method 2
Single Photon Avalanche Diode (SPAD) based photon counters offer the ability to detect very low levels of radiation by counting individual photons
Data Source
AI summary
A radiation-sensitive device is disclosed. The device includes an array of single photon avalanche diodes (SPADs) and circuitry configured to measure an intensity of incident radiation from the array of SPADs with a plurality of different measurement windows to provide an associated plurality of results. The circuitry is configured to determine the intensity of the incident radiation from one of the plurality of results, a selection of the result determined by whether the result exceeds a maximum count defined, at least in part, by a duration of the measurement window associated with the result. An associated method of increasing a dynamic range of a radiation-sensitive device comprising an array of SPADs is also disclosed.