Photon-Counting Photoelectric Conversion for Single-Photon Detection
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Solution Overview
Problem
Existing photoelectric conversion devices struggle to accurately measure changes in luminance at the level of a single photon and efficiently process high-speed phenomena due to limitations in synchronous operation and analog signal processing.
Innovation Solution
A photoelectric conversion device utilizing an avalanche photodiode (APD) with a stacked sensor and circuit chip configuration, incorporating counter circuits and threshold-based digital signal processing to detect address events, enabling real-time detection of luminance changes and high-speed phenomena by counting photons and setting digital detection conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If synchronous operation and analog signal processing are used in existing photoelectric conversion devices, then the device structure is relatively simple, but the device cannot accurately measure changes in luminance at the single photon level and cannot efficiently process high-speed phenomena
Solution Approach 1:
The patent replaces analog signal processing with digital signal processing. Specifically, it uses avalanche photodiodes to generate electrical signals from photons, then employs digital counter circuits to count these signals and digital logic circuits to process the counted values. This substitution of digital for analog systems enables precise single-photon level luminance change detection while maintaining manageable device complexity through standardized digital circuit design.
Solution Approach 2:
The patent changes the operational parameters by implementing threshold-based detection. It sets specific threshold values for photon counting (e.g., when the count value changes by a predetermined threshold or more), which enables the system to detect luminance changes at single-photon levels. This parameter-based approach allows precise measurement without requiring overly complex continuous analog processing.
2Measurement precision
If digital signal processing and threshold-based detection are implemented, then luminance change detection accuracy improves, but the data processing complexity increases
Solution Approach 1:
The patent extracts and processes only the essential information from the photon detection process. It uses counter circuits to count photons and then applies threshold-based filtering to extract only significant luminance changes. By taking out and processing only the relevant data (changes exceeding the threshold) rather than all raw data, the system achieves high detection accuracy while keeping processing complexity manageable.
Solution Approach 2:
The patent applies partial action by implementing detection only when photon count changes exceed a predetermined threshold. Instead of continuously processing all photon events, the system selectively processes only those events that represent significant luminance changes. This partial processing approach maintains high measurement precision for meaningful events while reducing overall processing complexity.
3Loss of information
If continuous data output is used, then all luminance information is captured, but data output volume increases when luminance is unchanged
Solution Approach 1:
The patent implements partial data output by comparing current photon count values with previous values and only outputting data when changes exceed a predetermined threshold. This selective output approach ensures that all significant luminance information is captured (maintaining information completeness) while minimizing data output volume by excluding redundant unchanged states from the output stream.
4Speed
If high-speed phenomena are processed, then detection speed improves, but processing efficiency decreases without optimized data output
Solution Approach 1:
The patent achieves both high detection speed and processing efficiency by implementing threshold-based selective data output. The system continuously monitors photon arrivals at high speed using avalanche photodiodes and counter circuits, maintaining fast detection capability. Simultaneously, it outputs data only when luminance changes exceed the threshold, improving processing efficiency by eliminating redundant data transmission and processing of unchanged states.
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
Enables precise detection of luminance changes at the single photon level, supports high-speed processing, and reduces data output when luminance is unchanged, enhancing accuracy and efficiency in capturing dynamic visual scenes.
Implementation Method 1
a photoelectric conversion device (hereinafter, photon counting sensor) that digitally counts the number of photons arriving at an avalanche photodiode (hereinafter, APD)
Implementation Method 2
arriving at an avalanche photodiode (hereinafter, APD)
Data Source
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AI summary
A photoelectric conversion device including a pixel configured to output a signal in response to incidence of a photon includes first measurement configured to measure the signal output from the pixel, second measurement means configured to measure time until the signal measured by the first measurement means reaches a first threshold, first storage means for storing, as a first time, a result of the measurement by the second measurement means at a first time point, comparison means configured to compare the first time stored in the first storage means and a second time measured by the second measurement means at a second time point later than the first time point, and output means configured to output a signal corresponding to a result of the comparison by the comparison means.