CMOS Image Sensor Photon Counting Circuit for Low-Light Imaging
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Solution Overview
Problem
Current imaging devices face challenges in achieving low-noise, high-accuracy optical detection with a wide dynamic range, especially at low illuminance, due to the limitations of photon counters and analog-to-digital converters, which often result in high costs and reduced aperture ratios.
Innovation Solution
The proposed solution involves a CMOS image sensor with a pixel array, sensing circuits, and a determination result integration circuit that performs time-division photon counting, allowing multiple pixels to share sensing circuits and counters, thereby reducing circuit size and enabling high-performance photon counting with a wide dynamic range without the need for analog signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photon counter is used for high measurement accuracy, then detection precision is improved, but the system cost increases and dynamic range is limited
Solution Approach 1:
The patent divides the pixel array into multiple regions with different exposure times, allowing simultaneous measurement of both low-light and high-light scenarios. This segmentation enables the system to achieve high measurement precision across a wide dynamic range without requiring multiple separate devices
Solution Approach 2:
The patent implements dynamic exposure time control where different pixel regions have different exposure times based on local light intensity conditions. This dynamic adaptation allows the system to maintain high measurement accuracy while extending the measurable dynamic range
2Adaptability or versatility
If a photodiode with AD converter is used for large dynamic range, then measurement range is improved, but noise increases and system size increases
Solution Approach 1:
The patent replaces the analog signal processing chain (photodiode + AD converter) with a digital photon counting approach. By directly counting photons in the digital domain, the system achieves wide dynamic range without introducing analog noise or requiring high-speed AD conversion
Solution Approach 2:
The patent uses periodic exposure cycles with different durations for different pixel regions. This periodic measurement approach allows the system to capture both low-light and high-light signals within the same frame period, achieving wide dynamic range without continuous high-speed conversion
3Manufacturing precision
If the number of pixels is increased for higher resolution, then imaging quality is improved, but the system size and cost increase significantly
Solution Approach 1:
The patent makes each pixel region serve multiple functions by implementing variable exposure times within the same pixel array. This multi-functionality allows the system to achieve high resolution without requiring separate dedicated devices for different measurement conditions, thereby reducing overall system size and cost
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 configuration allows for accurate light intensity measurement and imaging with reduced noise and a wide dynamic range, even at low illuminance, while minimizing circuit size and eliminating the need for expensive external devices, thus providing high-precision imaging with reduced exposure and lower system costs.
Implementation Method 1
a pixel array section functioning as a light receiving section which includes photoelectric conversion devices and in which a plurality of pixels, which output electric signals when photons are incident
Data Source
AI summary
An imaging device including a pixel array section functioning as a light receiving section which includes photoelectric conversion devices and in which a plurality of pixels, which output electric signals when photons are incident, are disposed in an array; a sensing circuit section in which a plurality of sensing circuits, which receive the electric signals from the pixels and perform binary determination regarding whether or not there is an incidence of photons on the pixels in a predetermined period, are arrayed; and a determination result integration circuit section having a function of integrating a plurality of determination results of the sensing circuits for the respective pixels or for each pixel group, wherein the determination result integration circuit section derives the amount of photon incidence on the light receiving section by performing photon counting for integrating the plurality of determination results in the plurality of pixels.