SPAD Array Particulate Sensor Noise Reduction

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Solution Overview

Problem

Existing particulate detection sensors face challenges in accurately measuring low concentrations of fine particles and PM2.5 due to noise interference, particularly from ambient temperature fluctuations, electromagnetic noise, and increased costs associated with complex circuit configurations and multiple components.

Innovation Solution

A particulate detection sensor utilizing a SPAD array with single photon avalanche diodes operating in Geiger mode, which projects light and receives scattered light to generate pulse signals, and a signal processing unit that calculates concentration based on pulse count values during lighting and lighting-off periods, effectively distinguishing scattered light from noise components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional light detecting elements and amplifier circuits are used, then the sensor can detect scattered light from particulates, but noise interference from thermal noise, shot noise, and electromagnetic noise significantly degrades measurement accuracy at low particulate concentrations

Engineering Contradiction:

Improveparticulate concentration detection accuracyVSAvoidnoise interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the operating parameters of the light detecting element by applying a reverse bias voltage greater than the breakdown voltage to operate in Geiger mode, enabling single-photon detection capability. This parameter change transforms the detection threshold and significantly improves signal-to-noise ratio for low concentration particulate detection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent divides the light detecting element into multiple independent SPADs arranged in an array, where each SPAD independently detects photons and generates pulse signals. This segmentation allows statistical processing of multiple detection channels, improving measurement accuracy and enabling noise discrimination through pulse counting

Inventive Principle:

Principle #1Segmentation

2Reliability

If complex circuit configurations with multiple amplifier stages and filters are implemented, then noise filtering capability is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvenoise rejection capabilityVSAvoidcircuit configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the complex amplifier circuitry and analog filtering stages from the detection system. By using SPADs that directly output digital pulse signals upon photon detection, the system removes the need for analog signal amplification and filtering circuits, thereby reducing device complexity while maintaining noise rejection capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the analog electronic amplification and filtering system with a digital pulse counting system. The SPADs directly convert optical signals into electrical pulse signals that can be counted and processed digitally, substituting complex analog circuitry with simpler digital processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If multiple light detecting elements and processing circuits are used to improve detection accuracy, then measurement precision increases, but the number of components and manufacturing cost increase

Engineering Contradiction:

Improvelow concentration particulate detection accuracyVSAvoidcomponent count

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent makes each SPAD in the array multi-functional by designing them to independently perform complete detection functions - photon detection, signal generation, and noise rejection - without requiring external amplifier circuits. Each SPAD acts as a self-contained detection unit, reducing the overall component count while maintaining high measurement precision through statistical processing of multiple channels

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances measurement accuracy, reduces noise interference, and minimizes component count, leading to a more cost-effective and reliable detection of particulate concentrations, even at low levels and in varying ambient conditions.

Implementation Method 1

a light detecting element (for example, photodiode) 505 that receives light 504 scattered by dust particles in the detection area 503

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

single photon avalanche diodes (SPADs), receives light projected from the light emitting element and scattered by the particulate, and outputs a pulse signal, the single photon avalanche diodes being arranged in an array and operating in a Geiger mode

Methodology Applied

Scientific EffectAvalanche Breakdown: Avalanche Breakdown

Data Source

PatentUS11009441B2Particulate detection sensor, dust sensor, air conditioning device, and control method of particulate detection sensor

Publication Date: 2021.05.18 SHARP KK

AI summary

A particulate detection sensor that detects concentration of a particulate in a fluid includes a light emitting element, a SPAD array light detecting unit, and a signal processing unit. The signal processing unit calculates the concentration of the particulate based on a first pulse count value in a lighting period and a second pulse count value in a lighting-off period.