Particle Counter Interference Detection for Small Particles
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Solution Overview
Problem
Existing particle counters face challenges in accurately counting small-size particles in fluids due to high background noise, particularly in chemical solutions used in semiconductor manufacturing, which hinders the detection of particles smaller than 30 nm.
Innovation Solution
A particle counter design that incorporates a light source, a light superimposition unit, an irradiation optical system, a detection optical system, a reference optical system, and a detector with light receivers to generate and count interference light beams from scattered and reference light beams, enhancing the signal-to-noise ratio and detection efficiency by using multiple reference light beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-divided light receiving element is used to reduce background noise, then the signal-to-noise ratio improves, but the effective light receiving area is reduced
Solution Approach 1:
The light receiving element is divided into multiple segments (first light receiver and second light receiver) with different functional roles. The first light receiver detects scattered light from particles, while the second light receiver detects reference light. This segmentation allows each receiver to be optimized for its specific function, improving the signal-to-noise ratio without unnecessarily reducing the total effective light receiving area.
Solution Approach 2:
A reference light beam is introduced as an intermediary to interfere with the scattered light beam. This reference light serves as a mediator that carries information about the optical path length, enabling the system to distinguish particle signals from background noise through interference patterns, thereby improving measurement precision.
2Productivity
If scattered light is directly detected from particles in chemical solution, then particle counting is performed, but high background noise from the chemical solution medium prevents detection of small-size particles
Solution Approach 1:
A reference light beam is introduced as an intermediary to interfere with the scattered light beam. This reference light serves as a mediator that carries information about the optical path length, enabling the system to distinguish particle signals from background noise through interference patterns, thereby improving measurement precision.
Solution Approach 2:
The system detects changes in the interference pattern (analogous to color/intensity changes) caused by variations in optical path length. When particles pass through the measurement region, they change the optical path length, which changes the interference pattern detected by the second light receiver, enabling particle detection despite background noise.
3Measurement precision
If the optical path length between light source and light receiver is increased to improve detection, then detection sensitivity improves, but the device size and complexity increase
Solution Approach 1:
The reference light beam and scattered light beam are merged through optical interference in a compact configuration. By using beam splitters and mirrors to combine these light paths in a controlled manner, the system achieves enhanced detection sensitivity without requiring a large physical separation between components, thus reducing device complexity.
Solution Approach 2:
The system uses interference in the optical domain (another dimension) to achieve path length differentiation without requiring large physical path length differences. By detecting phase differences through interference patterns rather than relying solely on physical distance, the system improves detection sensitivity while maintaining a compact device structure.
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 design enables the effective counting of small-size particles with improved signal-to-noise ratios and higher counting efficiency, specifically for particles smaller than 30 nm, by leveraging interference light beams and multiple reference light beams to reduce background noise.
Implementation Method 1
The interference light beam is generated by interference between the scattered light beam and one of the reference light beams that enter the light superimposition unit
Implementation Method 2
out of scattered light beams scattered by a particle contained in the fluid in the detection area
Data Source
AI summary
Provided is a particle counter including: a light source; a light superimposition unit configured to superimpose light beams; an irradiation optical system configured to irradiate a fluid in a flow passage with one of a plurality of light beams from the light source; a detection optical system configured to make a part of scattered light beams by a particle in the fluid enter the light superimposition unit; a reference optical system configured to split another one of the plurality of light beams into a plurality of reference light beams and makes the reference light beams enter the light superimposition unit; and a counting unit configured to count the particles on the basis of detection signals corresponding to an interference light beam received by a light receiver. The interference light beam is generated by interference between the scattered light beam and one of the reference light beams at the light superimposition unit, and is received by the light receiver corresponding to the reference light beam.