Dichroic Element Common Path for Particle Size Measurement
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Solution Overview
Problem
Existing methods for measuring particle size distribution by light scattering often require complex arrangements to monitor and stabilize light sources, leading to increased costs, unwanted scattering, and reduced signal-to-noise ratios, particularly when using multiple wavelengths.
Innovation Solution
The use of a dichroic element to direct light beams of different wavelengths onto a common path, with a single detector to monitor and stabilize the power of both beams, reducing the number of optical components and minimizing stray reflections, thereby simplifying the apparatus and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex arrangements are used to monitor and stabilize light sources, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the monitoring of multiple light sources into a single common path using a dichroic element. Instead of having separate detection paths for each light source, the system merges them so that a single detector can monitor both the first and second light sources through the dichroic element, reducing device complexity while maintaining measurement accuracy
Solution Approach 2:
The dichroic element serves multiple functions simultaneously: it directs the first and second light beams onto a common path, allows the single detector to monitor both light sources, and enables power stabilization for both sources. This multi-functionality reduces the need for separate components, simplifying the overall apparatus
2Reliability
If multiple optical elements are used to monitor light sources, then power stabilization is achieved, but stray reflections and unwanted scattering increase
Solution Approach 1:
By merging the monitoring function into a single common path via the dichroic element, the patent reduces the number of optical elements that could generate stray reflections. The dichroic element itself is designed to minimize unwanted scattering while maintaining the necessary beam directionality for power monitoring and stabilization
3Measurement precision
If more optical components are used, then light source monitoring is achieved, but signal-to-noise ratio decreases
Solution Approach 1:
The patent merges the monitoring function into a single common path, reducing the number of optical components that could introduce noise through stray reflections and scattering. This consolidation improves the signal-to-noise ratio for light scattered by the sample while maintaining the ability to monitor and stabilize both light sources
Solution Approach 2:
The patent converts what would normally be wasted light energy (reflected light from the dichroic element) into a useful monitoring signal. By detecting the reflected portion of the first beam, the system utilizes light that would otherwise be lost to monitor power and stabilize the light source, improving the overall signal-to-noise ratio
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 results in a more cost-effective, simpler apparatus with enhanced signal-to-noise ratios and improved detection of light scattered by the sample, particularly for backscattered light, allowing for more accurate particle size distribution measurements.
Implementation Method 1
a dichroic element arranged to direct most of the power of the first and second beams onto a common path by transmission and reflection of the first and second beams respectively at the dichroic element
Implementation Method 2
a first detector arranged to detect a portion of the first beam reflected by the dichroic element
Implementation Method 3
a control system for controlling the power of the first beam, the control system being arranged to receive an output signal from the first detector and to adjust the power of the first beam in response thereto
Implementation Method 4
measuring particle size distribution for a sample by light scattering
Data Source
AI summary
Apparatus (100) for measuring particle size distribution by light scattering comprises a blue LED (102) and a 633 nm helium neon laser (104). Light output from the LED and laser is separately passed or reflected by a dichroic element (116) onto a common path through a sample cell (122) containing a sample, the particle size distribution of which is to be measured. Light scattered from the sample cell is detected by one or more detectors (112B-H). Light transmitted by the sample cell is detected by detectors 112A, 112J. Output signals from one or more of the detectors are passed to a computation unit (114) which calculates particle size distribution. A small percentage of light from the blue LED is reflected by the dichroic element to a detector (110). Similarly, a small percentage of light from the laser is passed by the dichroic element to the detector. Output signals from the detector are fed back to control units (106, 108) to stabilize the output power of the LED and laser.