Tapered Waveguide for Infrared Gas Sensor Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Infrared light absorption gas concentration measurement devices face accuracy issues due to the risk of infrared light being incident on the band pass filter at angles greater than a predetermined angle, which affects measurement accuracy when using anti-reflection films with non-zero reflectance materials.
Innovation Solution
A gas concentration measurement device featuring a waveguide member with a tapered inner peripheral surface, including a first curved portion with decreasing cross-section along the longitudinal axis, reduces the energy of obliquely incident infrared light by reflecting it, thereby minimizing the impact on the band pass filter's transmission band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an anti-reflection film made of inexpensive material with non-zero reflectance is used, then the manufacturing cost is reduced, but the infrared light is reflected and incident on the band pass filter at an angle greater than the predetermined angle, causing the transmission band to shift and measurement accuracy to decrease
Solution Approach 1:
The patent extracts the harmful reflective function from the anti-reflection film by introducing a separate waveguide member with tapered inner peripheral surface. This waveguide member specifically handles the obliquely incident light through total internal reflection, while the anti-reflection film focuses only on reducing reflectance for normally incident light, thereby resolving the contradiction between using inexpensive materials and maintaining measurement accuracy.
Solution Approach 2:
The waveguide member acts as an intermediary component between the anti-reflection film and the band pass filter. It intercepts and redirects obliquely incident infrared light through its tapered structure, preventing this light from reaching the band pass filter at harmful angles. This intermediary structure allows the use of inexpensive anti-reflection film materials without compromising measurement accuracy.
2Measurement precision
If the anti-reflection film is made of material with reflectance close to zero, then the measurement accuracy is maintained, but the material selection is limited and manufacturing cost increases
Solution Approach 1:
The patent separates the function of handling oblique light reflection from the anti-reflection film material itself, extracting this function and assigning it to the waveguide member structure. This allows the anti-reflection film to use inexpensive materials with non-zero reflectance while the waveguide member ensures that obliquely incident light does not reach the band pass filter, thereby maintaining measurement accuracy without limiting material selection.
3Measurement precision
If obliquely incident infrared light reaches the band pass filter, then the transmission band shifts and measurement accuracy decreases, but removing all such light would reduce the overall light intensity reaching the detector
Solution Approach 1:
The waveguide member with tapered inner peripheral surface creates a localized solution at the specific location where oblique light interception is needed. The tapering geometry is designed to intercept only obliquely incident light while allowing normally incident light to pass through to the detector. This local quality approach maintains transmission band stability without significantly reducing overall light intensity reaching the detector.
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 enhances measurement accuracy by reducing the energy of obliquely incident infrared light, ensuring more precise gas concentration measurements.
Implementation Method 1
A portion or entirety of the inner peripheral surface of the wave-guiding portion includes a tapered region... The waveguide member reflects the infrared light that has entered the wave-guiding portion through the entrance portion in the tapered region
Implementation Method 2
a band pass filter; a detector that detects the infrared light from the light source through a band pass filter
Implementation Method 3
a detector that detects the infrared light from the light source through a band pass filter
Implementation Method 4
infrared-light-absorption gas concentration measurement devices are used to analyze sample gas by utilizing the fact that the sample gas absorbs infrared light in a specific wavelength range
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A gas concentration measurement device (100) includes a light source (20) that emits infrared light, a detector (60) that detects the infrared light through a band pass filter (41), and a waveguide member (90) including a wave-guiding portion (93) having a tubular inner peripheral surface, an entrance portion (91) that is formed at one side of the wave-guiding portion (93) and through which the infrared light from the light source (20) is introduced, and an exit portion (92) that is formed at the other side of the wave-guiding portion (93) and guides the infrared light that has passed through the wave-guiding portion (93) toward the detector (60). A portion or entirety of the inner peripheral surface of the wave-guiding portion (93) includes a tapered region having a cross section that decreases along a direction from the entrance portion (91) to the exit portion (92). The waveguide member (90) reflects the infrared light that has entered the wave-guiding portion (93) through the entrance portion (91) in the tapered region, so that energy of the infrared light that is obliquely incident on the band pass filter (41) is reduced.