Ring-Form Particle Concentration Measuring Device
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Solution Overview
Problem
Conventional particle concentration measuring devices face challenges in accurately measuring particle concentration in clean rooms with non-uniform airflow and struggle to detect fine particles due to airflow disturbance and insufficient light intensity, especially when trying to measure small particles in indoor spaces.
Innovation Solution
A particle concentration measuring device with a ring-form measurement region, a planar light curtain, and a particle detecting unit that calculates concentration based on the volume of airflow passing through the light curtain, allowing for high-accuracy detection of particles without disturbing the airflow and enabling the measurement of fine particles by adjusting the light-receiving time and vane angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sampling tube is installed at the measurement target position to measure particle concentration, then the measurement can be performed at the target point, but the airflow changes due to the suction and the degree of freedom in measurement place is reduced
Solution Approach 1:
The invention extracts the measurement function from the airflow path by using a remote measurement approach. The laser beam and camera are positioned separately from the airflow, allowing measurement without installing sampling tubes that would disturb the flow. The measurement volume is defined by the laser pulse and shutter timing rather than a physical sampling tube.
Solution Approach 2:
The invention introduces light (laser beam) as an intermediary to measure particle concentration without physically contacting or disturbing the airflow. The laser beam acts as a mediator that interacts with particles optically, allowing remote detection of particle concentration while maintaining airflow uniformity.
2Measurement precision
If the suction pump operation is adjusted to make airflow velocity and suction speed equal, then measurement accuracy improves, but it is practically difficult to adjust them to be equal
Solution Approach 1:
The invention replaces the mechanical sampling system with an optical measurement system. Instead of using a suction pump to draw air through a sampling tube, the system uses a laser beam and camera to optically detect particles in the airflow. This eliminates the need to match suction speed with airflow velocity, greatly simplifying operation.
3Quantity of substance
If the suction time is increased to obtain sufficient sampled air volume, then enough particles are captured, but particle concentration in a space far more upwind than the target point is also detected which deteriorates detection accuracy
Solution Approach 1:
The invention uses preliminary action by defining the measurement volume in advance through laser pulse width and shutter timing. The measurement region is predetermined by the optical parameters before measurement begins, allowing precise control of the sampled volume without extending upwind contamination.
Solution Approach 2:
The invention employs periodic action through pulsed laser illumination and synchronized shutter timing. The laser emits periodic pulses and the camera shutter opens at specific intervals to capture images during the laser pulse duration, enabling precise control of the measurement time window and corresponding air volume.
4Volume of stationary object
If the laser pulse width and shutter time are made extremely short to measure small particles in indoor spaces, then the sampling volume is reduced, but the light intensity becomes insufficient for measurement
Solution Approach 1:
The invention uses parameter changes by adjusting laser power and camera sensitivity to compensate for shorter exposure times. The laser pulse width and shutter time are optimized to balance the sampled volume with sufficient light intensity, and the laser power is increased to maintain adequate signal strength despite reduced integration time.
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 device achieves high-accuracy particle concentration measurement in clean rooms with uniform unidirectional flow, detecting fine particles of 1 µm or less without airflow disturbance, and can be adapted for non-straight flow types by linearly moving components, ensuring accurate volume calculation and improved light reception.
Implementation Method 1
a light curtain forming unit forming a planar light curtain in the inner opening
Implementation Method 2
a particle detecting unit receiving scattered light from particles passing through the light curtain to detect the particles
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A particle concentration measuring device includes: a measurement region formation part which has a wall (10) of substantially ring-form and through an inner opening of which gas relatively flows orthogonally; a light curtain forming unit (12A, 12B) forming a planar light curtain (FL) in the inner opening: a particle detecting unit (15) receiving scattered light from particles passing through the light curtain (FL) to detect the particles; and a calculating unit (22) calculating particle concentration based on the total number of the particles detected by the particle detecting unit (15) in a volume of an airflow passing through the light curtain (FL) in a unit time.