Adaptive SPAD Array Switching for Wide Dynamic Range Sensing
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Solution Overview
Problem
Existing SPAD-based radiation sensors face limitations in dynamic range due to noise, circuitry capacity, and device size, which compromise signal-to-noise ratio and require additional components, especially in applications like Point of Care testing and Electronic-Nose applications.
Innovation Solution
Adapting the number of SPADs used to detect radiation in inverse proportion to the intensity of incident radiation, with larger counters for lower intensity levels and fewer SPADs for higher intensity levels, minimizing circuitry and die size while maintaining signal-to-noise ratio.
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 measurement precision is improved, but device complexity increases due to increased associated circuitry
Solution Approach 1:
The patent implements dynamic switching between different SPAD subsets based on radiation intensity levels. At low radiation levels, a first subset of SPADs is activated to maximize signal-to-noise ratio. At high radiation levels, a second subset of SPADs is activated to handle the increased count rate. This dynamic adaptation resolves the contradiction by using more SPADs (and thus more circuitry) only when needed for low-level measurements.
Solution Approach 2:
The SPAD array is divided into multiple subsets that can be independently controlled. The first subset is optimized for low radiation level measurements with higher signal-to-noise ratio, while the second subset is optimized for high radiation level measurements. This segmentation allows the system to use only the necessary portion of the SPAD array for each measurement condition, reducing overall circuitry complexity.
2Measurement precision
If all available SPADs are used for both low and high intensity radiation, then measurement precision is improved, but die size increases substantially
Solution Approach 1:
The system dynamically selects which SPAD subsets to activate based on the detected radiation intensity level. This dynamic operation mode allows the same physical device with fixed die size to achieve the performance benefits of using all SPADs only when necessary, without permanently requiring a larger die area.
Solution Approach 2:
Instead of designing the die to always accommodate all SPADs being active simultaneously, the patent uses partial action by activating only the necessary subset of SPADs for each measurement condition. This allows a smaller die size to suffice, as not all SPADs need to be simultaneously operational.
3Device complexity
If the number of SPADs is reduced for high intensity radiation levels, then device complexity is reduced, but measurement precision at low levels deteriorates
Solution Approach 1:
The system switches between different SPAD subsets based on radiation intensity. When low radiation levels are detected, the first subset of SPADs is activated to provide high signal-to-noise ratio measurements. When high radiation levels are detected, the second subset is activated to handle the increased count rate. This dynamic switching resolves the contradiction by ensuring high precision is maintained when needed while reducing complexity when not required.
Solution Approach 2:
The system continuously monitors radiation intensity levels and uses this feedback to determine which SPAD subset should be active. This feedback mechanism ensures that the appropriate balance between precision and complexity is maintained by adapting the active SPAD subset to current measurement conditions.
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
Achieves a large dynamic range without increasing device size or compromising signal-to-noise ratio, optimizing power consumption and reducing the number of required components.
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
Data Source
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AI summary
A radiation-sensitive device (420) is disclosed. The radiation-sensitive device comprises: a plurality of single photon avalanche diodes (SPADs) (105-0), and processing circuitry (415) configured to determine an intensity of incident radiation using at least one of the plurality SPADs. An amount of the SPADs used to determine the intensity of the incident radiation varies in relation to the intensity of the incident radiation. Also disclosed in an associated method of determining an intensity of radiation incident upon such a radiation-sensitive device, and uses of the radiation-sensitive device in an electronic-nose or point-of-care apparatus, or for ambient light sensing.