Photon-Counting Light Detector with Avalanche Photodiode Array
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Solution Overview
Problem
Existing light detectors face challenges in accurately measuring light levels over a wide dynamic range, especially outdoors, due to variations in illuminance and temperature, which affect detection efficiency and dynamic range, and are prone to saturation and noise.
Innovation Solution
A light detector comprising a photon-counting type light-receiving unit with an avalanche photodiode in Geiger mode, a quenching resistor, and an integrating unit that converts binary pulse outputs into a proportional light measurement, allowing for simultaneous detection of multiple photons and reducing dead-time through parallel processing and array configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photon-counting type light detector is used, then detection sensitivity is improved, but the dynamic range is reduced due to pulse merging at high light levels
Solution Approach 1:
The patent divides the light detection function into multiple independent photodetector elements arranged in an array. Each element operates independently with its own pulse output, allowing parallel processing of light signals. This segmentation prevents pulse merging by distributing the detection load across multiple channels, thereby expanding the dynamic range while maintaining high detection sensitivity.
Solution Approach 2:
The patent transitions from single-point photon counting to spatially-resolved detection by arranging photodetectors in a two-dimensional array. This dimensional expansion allows simultaneous detection of multiple photons across different spatial positions, converting the limitation of pulse merging in time domain to a优势 in space domain, thus achieving wide dynamic range measurement.
2Productivity
If the measurement period is shortened to improve productivity, then the response speed is improved, but the measurement precision is reduced
Solution Approach 1:
The patent performs preliminary integration of light signals during the measurement period, accumulating photon events in real-time. This preliminary action allows the system to maintain short measurement periods for fast response while still achieving sufficient measurement precision through continuous signal accumulation during the brief interval.
Solution Approach 2:
The patent implements continuous signal integration and accumulation during the measurement period, ensuring that useful detection action continues without interruption. This continuous processing maintains measurement precision even when the overall measurement period is shortened, as the system continuously accumulates valid photon events throughout the brief measurement window.
3Adaptability or versatility
If outdoor light detection is performed, then the field of application is expanded, but the measurement precision is reduced due to wide dynamic range requirements
Solution Approach 1:
The patent employs a dynamic measurement approach where the system adapts to varying outdoor light conditions by processing signals from multiple photodetector elements in parallel. The dynamic range is handled through real-time signal accumulation and statistical processing, allowing the system to maintain measurement precision across widely varying illuminance levels from bright sunlight to dim ambient light.
Solution Approach 2:
The patent changes the detection parameter from single-photon counting to integrated signal accumulation across multiple detectors. This parameter change allows the system to handle outdoor conditions with wide dynamic range by summing signals from multiple elements, where the total accumulated signal maintains precision even when individual detector signals vary widely in intensity.
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
The solution enables stable and accurate light detection across a wide dynamic range, independent of temperature variations, with expanded dynamic range and reduced noise, while maintaining efficiency and cost-effectiveness by using a semiconductor avalanche photodiode in a CMOS process.
Implementation Method 1
When a photon falls on the APD, an electron-hole pair is generated, the electrons and the holes are accelerated with a high electric field, causing impact ionization
Implementation Method 2
new electron-hole pairs cause impact ionization one after another in a manner similar to an avalanche
Implementation Method 3
a quenching resistor
Data Source
AI summary
There is provided a light detector having a light-receiving unit including a light-receiving element of a photon-counting type that receives incident light and outputs a binary pulse indicating presence or absence of photon incidence, and an integrating unit that calculates an output value in which a total of pulse widths of pulses is integrated over a measurement period.