Rectangular Light Receiver Layout for Stable Optical Concentration Sensing
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Solution Overview
Problem
Optical concentration measurement devices face challenges in maintaining high precision and robust signal-noise ratio (SNR) in harsh environments with high temperature and humidity, and under vibration, due to displacement issues between light emitting and receiving units, leading to errors in concentration measurement.
Innovation Solution
The device employs a rectangular LED light source and a light receiving unit with uniform sensitivity, where the light guiding unit ensures that the light area on the receiving surface is either half or twice the size of the receiving surface, maintaining a stable SNR and robustness by controlling the spot size and shape within specific limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the spot diameter is enlarged to decrease light intensity per unit area, then the uniformity of light distribution is improved, but the amount of received light deteriorates and the SNR decreases
Solution Approach 1:
The invention changes the geometric parameters of the light receiving surface (making it larger than the spot diameter) and adjusts the light guiding unit to control the spot diameter within a specific range (0.3 to 0.7 times the light receiving surface diameter). This parameter optimization allows the light intensity to be distributed uniformly across the receiving surface while maintaining sufficient total light amount for high SNR.
2Ease of manufacture
If the device is made small size and low-cost, then the manufacturing cost and complexity are reduced, but maintaining high precision and robust SNR under vibration and environmental changes becomes difficult
Solution Approach 1:
The invention performs preliminary design optimization by defining specific geometric relationships between components (spot diameter as 0.3-0.7 times the light receiving surface diameter) before manufacturing. This preliminary configuration ensures that the device maintains high measurement precision and robust SNR under various environmental conditions without requiring complex additional components or post-manufacturing adjustments.
Solution Approach 2:
By optimizing the geometric parameters (light receiving surface size relative to spot diameter) and material properties, the invention achieves high precision measurement capability in a compact, cost-effective design. The specific parameter range ensures robust performance under vibration and environmental changes while keeping the device simple to manufacture.
3Adaptability or versatility
If displacement occurs in the relative positional relationship among light emitting unit, light guiding unit, and light receiving unit due to deformation or expansion, then the amount of light reaching the light receiving unit changes, but the SNR changes from the shipment value causing measurement error
Solution Approach 1:
The invention incorporates preliminary compensation design by configuring the light receiving surface to be larger than the spot diameter and defining specific geometric relationships between components. This preliminary design ensures that even when displacement occurs due to thermal expansion, moisture absorption, or vibration, the light receiving surface continues to capture sufficient light uniformly, maintaining stable SNR and measurement precision without requiring active compensation mechanisms.
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 configuration achieves a high and robust SNR, preventing measurement precision deterioration even under environmental changes or assembly errors, enhancing the device's versatility for use in on-vehicle sensors and other challenging conditions.
Implementation Method 1
a light guiding unit configured to guide light emitted by the LED light source to the light receiving unit
Implementation Method 2
a light receiving unit configured to have a rectangular light receiving surface having uniform sensitivity and output a single detection signal representing intensity of received light
Implementation Method 3
non-dispersive infrared type optical concentration measurement devices that, using a phenomenon that wavelength of infrared rays absorbed by a gas differs depending on the type of the gas, measure concentration of the gas by detecting the amount of absorption of the gas
Data Source
AI summary
An optical concentration measurement device includes an LED light source, alight receiving unit having a rectangular light receiving surface and outputting a detection signal representing intensity of received light, and light guiding units guiding light emitted by the LED light source to the light receiving unit, wherein a shape on the rectangular light receiving surface of light radiated on the light receiving surface is rectangular, the optical concentration measurement device measures concentration of an object to be measured existing in a light path formed by the light guiding units, based on the detection signal output from the light receiving unit, and the light guiding units guide light at a diffraction limit or greater in such a way that area of the light on the rectangular light receiving surface is ½ or less of area of the rectangular light receiving surface.