SPAD Image Sensor Overflow Counting for Low-Power Photon Estimation
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Solution Overview
Problem
The use of a large-bit counter in single-photon avalanche diodes for counting photons leads to increased power consumption.
Innovation Solution
A single-photon avalanche diode-based image sensor that estimates the total number of photons by utilizing the overflow time point of a counter, counting only a subset of pulses during the exposure time and using a global clock to generate additional clock pulses after the overflow point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a counter with a large number of bits is used to count a large number of photons, then the counting accuracy is improved, but the circuit size increases and power consumption increases
Solution Approach 1:
The patent applies partial action by counting photons only until the counter overflows, then resetting and continuing the count in subsequent cycles. Instead of counting all photons in one exposure period with a large-bit counter, the system performs partial counting operations across multiple cycles, achieving accurate total photon measurement while using a smaller counter that consumes less power.
2Measurement precision
If a counter with a large number of bits is used to count a large number of photons, then the counting accuracy is improved, but the circuit size increases
Solution Approach 1:
The system performs partial counting operations across multiple cycles. The counter counts photons until overflow, then resets and continues counting in the next cycle. This approach achieves accurate total photon measurement without requiring a large-bit counter, thereby reducing circuit size while maintaining measurement precision.
Solution Approach 2:
The patent segments the photon counting process into multiple cycles. Each cycle counts photons until the counter overflows, then the system resets the counter and continues counting in the next cycle. This segmentation allows the use of a smaller counter divided into multiple bits, reducing overall circuit complexity while achieving accurate total counts through accumulated cycle data.
3Measurement precision
If the counter counts all pulses during the entire exposure time, then the total photon count accuracy is improved, but the power consumption increases
Solution Approach 1:
The patent implements periodic action by operating the counter in repeating cycles. The counter counts photons until overflow, then resets and begins counting again in the next cycle. This periodic operation allows the system to measure total photons accurately across multiple exposure periods while reducing power consumption compared to continuous operation of a large-bit counter throughout the entire exposure time.
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
Significantly reduces power consumption by counting only a portion of the total photons received, while accurately estimating the total photon count using the overflow time point of the counter.
Implementation Method 1
the single-photon avalanche diode uses an avalanche multiplication that amplifies a single incident photon
Data Source
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AI summary
A single-photon avalanche diode-based image sensor according to one embodiment of the present disclosure comprises: a single photon avalanche diode (SPAD) that generates a plurality of pulses corresponding to each of a plurality of photons received during a predetermined exposure time; a front-end circuit that receives a set of pulses, from among the plurality of pulses, received during a portion of the time of the exposure time; and a counter that counts the number of pulses in the set of pulses, wherein an end point of a portion of the time may be based on an overflow time point of the counter that counts the number of pulses in the set of pulses.