Back-Reflection Optical System for Particle Detection
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Solution Overview
Problem
Current particle detection systems in clean room environments face limitations due to high-order optical imperfections, parasitic scattering, and noise from molecular interactions, which hinder the detection of small particles and reduce sensitivity and signal-to-noise ratios.
Innovation Solution
The use of visible blue light and a back-reflection optical system that combines light from both directions onto a single APD detector element, enhancing sensitivity and signal-to-noise ratios by focusing light intensity and reducing background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-power laser beams are used to increase sensitivity and size resolution, then detection capability improves, but noise from parasitic scattering processes (air glow) increases
Solution Approach 1:
The patent converts the harmful effect of molecular scattering (air glow) into a beneficial filtering mechanism by using wavelength-selective optical elements that transmit particle scattering signals while blocking molecular scattering noise at specific wavelengths, thereby enabling high-power laser operation without excessive noise
Solution Approach 2:
The patent introduces wavelength-selective optical filters as intermediary components between the laser source and detector, which mediate the interaction by allowing only specific wavelength ranges to reach the detector, thus separating useful particle scattering signals from harmful molecular scattering background
2Use of energy by moving object
If infrared diode lasers are used for particle detection, then compactness and power efficiency improve, but detection sensitivity for small particles deteriorates
Solution Approach 1:
The patent changes the fundamental parameter of laser wavelength from infrared to visible blue/green range, which fundamentally alters the scattering characteristics and enables detection of smaller particles while maintaining compact diode laser architecture and power efficiency
3Measurement precision
If visible blue light is used instead of infrared light, then particle detection sensitivity improves, but sensitivity to background radiation increases
Solution Approach 1:
The patent converts the potential harm of background radiation sensitivity into a benefit by using wavelength-selective filters that specifically block background radiation at visible wavelengths while allowing particle scattering signals to pass, thereby achieving high sensitivity without excessive background noise
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 approach allows for superior detection of smaller particles with improved signal-to-noise ratios and reduced sensitivity to background radiation, enabling more accurate particle counting and sizing in clean room environments.
Implementation Method 1
a beam of light intercepts a predetermined volume of fluid and a light collection and detector system detects the light redirected by the suspended particles
Implementation Method 2
the unscattered radiation is removed from the system by absorption (usually in dedicated beam dumps) before it may create undesirable light noise
Data Source
AI summary
The current invention pertains to devices for counting and sizing particles suspended in a stream of fluid flowing in a predominant flow direction. Such devices comprise a fluid stream forming system having a directional element arranged to form the stream of fluid flowing in predetermined direction of fluid flow; a laser beam forming optical system including at least one source of laser light having at least one wavelength between 200 nm and 1000 nm, a profiling optical subsystem, having at least one collimator lens and at least one convergent lens, positioned to arrange the laser light in a laser beam along a laser beam axis directed substantially to illuminate a prearranged scattering volume of the stream of fluid, and at least one laser beam dump. Also, the device includes a wide-angle detecting subsystem and wide-angle back-reflecting subsystem.