Compact Particulate Sensor Using Pulsed Light and Optical Filtering
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Solution Overview
Problem
Existing particulate air pollution detectors are large, stand-alone devices that cannot be easily integrated with portable communication devices, as they require an air pump and a hole on the host device, and are not effective in detecting fine particulate matter 2.5 (PM2.5) which is hazardous but not visible at low densities.
Innovation Solution
A compact particulate material sensor device that integrates with a system-on-chip (SOC) of a consumer electronic device, using a pulsed light source and photodetectors with optical and electronic filtering to detect scattered light from particulate matter while rejecting ambient light, allowing for detection of PM2.5 on a flat surface such as a phone back cover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing dust particle detectors use a pump to blow air into a dark tunnel with infrared light detection, then particulate air pollution can be detected, but the device becomes large and cannot be integrated with portable communication devices
Solution Approach 1:
The patent combines the light source, photodetectors, and optical filtering components into a single integrated sensor device that can be incorporated into portable communication devices. This merging eliminates the need for separate pump and tunnel components while maintaining PM2.5 detection capability.
Solution Approach 2:
The patent replaces the mechanical air pump system with a direct optical detection method where light is emitted through or near the device housing and scattered light from particulate matter is detected by photodetectors. This substitution eliminates the mechanical pump and tunnel structure, dramatically reducing device size.
2Measurement precision
If existing detectors use a dark tunnel structure, then back-scattered light can be detected, but the device requires a hole on the host device and cannot be easily integrated
Solution Approach 1:
The sensor device is designed to utilize the existing housing or back cover of the portable communication device as part of the optical path structure. The light source emits light through or near the housing, and the housing itself can serve as the optical tunnel, making the sensor universal for integration into various device forms without requiring additional holes or modifications.
Solution Approach 2:
The patent transitions from a three-dimensional tunnel structure to a two-dimensional planar integration where the light source, photodetectors, and optical filters are arranged on or near the device surface. This dimensional change allows integration into the flat housing structure of portable devices without requiring depth or additional holes.
3Measurement precision
If the sensor detects scattered light from PM2.5, then hazardous air pollution can be monitored, but ambient light contaminates the detection signal
Solution Approach 1:
The patent introduces optical filters as intermediary components between the photodetectors and the ambient environment. These filters selectively transmit the wavelength of light emitted by the light source while blocking ambient light wavelengths, thereby mediating the detection process to reject harmful ambient light contamination while maintaining sensitivity to scattered light from PM2.5.
Solution Approach 2:
The light source emits light in periodic pulses rather than continuously. The photodetectors are synchronized to detect signals only during or immediately after these pulse periods. This periodic action creates a temporal window for detection that distinguishes the scattered light signal from continuous ambient light, effectively rejecting the harmful ambient light contamination.
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 efficient detection of PM2.5 pollution, providing a portable and integrated solution for monitoring hazardous air pollution levels, enhancing inhalation health safety by effectively distinguishing scattered light from background light.
Implementation Method 1
detect light scattered from particulate material
Implementation Method 2
an optical filter can be formed over the photodetectors. The optical filter can be transparent to scattered light
Implementation Method 3
A number of photodetectors can be integrated with the semiconductor chip
Data Source
AI summary
A particulate matter sensing device includes a light source to generate a pulsed light at a first wavelength in response to a drive pulse. The device further includes one or more photodetectors. A thin-film filter is formed over the photodetectors and is tuned to be transparent to scattered light having a second wavelength substantially equal to the first wavelength. The scattered light is produced as a result of scattering of the pulsed light by the particulate matter. A charge collection circuit of the plurality of photodetectors electronically rejects background light.