SPAD Image Sensor Photon Counting With Counter Overflow Timing
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Solution Overview
Problem
Single-photon avalanche diodes (SPADs) face high power consumption due to the use of large bit counters for counting numerous photons, which increases circuit size and power consumption.
Innovation Solution
A single-photon avalanche diode-based image sensor estimates the total number of photons by utilizing the overflow time point of a counter, reducing power consumption by counting only a portion of the total photons.
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 only a portion of total photons using a limited-bit counter (e.g., 8 bits counting 0-255 photons) rather than using a large-bit counter to count all photons. The counter is intentionally designed with insufficient bits to overflow, and the overflow time point is used to estimate total photon count, thereby reducing power consumption while maintaining acceptable measurement accuracy
Solution Approach 2:
The patent changes the parameter of counter bit depth from large (e.g., 16 bits or more) to small (e.g., 8 bits), and compensates for the reduced counting capacity by using the overflow time point information to estimate total photons. This parameter change directly reduces circuit size and power consumption
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 patent applies partial action by counting only a portion of total photons using a limited-bit counter (e.g., 8 bits counting 0-255 photons) rather than using a large-bit counter to count all photons. The counter is intentionally designed with insufficient bits to overflow, and the overflow time point is used to estimate total photon count, thereby reducing circuit size while maintaining acceptable measurement accuracy
Solution Approach 2:
The patent changes the parameter of counter bit depth from large (e.g., 16 bits or more) to small (e.g., 8 bits), and compensates for the reduced counting capacity by using the overflow time point information to estimate total photons. This parameter change directly reduces circuit size
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 while maintaining excellent image quality under varying illumination conditions.
Implementation Method 1
the single-photon avalanche diode has very high sensitivity because it uses avalanche multiplication to amplify a single incident photon
Data Source
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AI summary
According to an embodiment of the present disclosure, a single-photon avalanche diode-based image sensor may comprise: a single-photon avalanche diode (SPAD) which generates a plurality of pulses corresponding to a plurality of photons, received during a predetermined exposure time, respectively; a front-end circuit which receives a set of pulses received during a partial time of the exposure time among the plurality of pulses; a counter which counts the number of pulses in the set of pulses; and a global clock which provides a plurality of clock pulses to the front-end circuit from after the partial time, wherein the quality of an image acquired using the SPAD is determined based on the timing of the global clock.