Infrared Optical Filter Stack for High-Yield Gas Sensing Modules
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Solution Overview
Problem
Existing optical modules, particularly those using non-dispersive infrared absorption gas concentration measuring devices, face challenges in optimizing optical filter specifications, leading to reduced mass productivity due to thicker multilayer films and decreased processability and yield.
Innovation Solution
An optical module comprising a plurality of optical filters with specific transmission and sensitivity characteristics, including a common transmission band, transmittance differences, and cutoff bands, is designed to improve mass productivity by simplifying the optical filter structure while maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision optical filters with thicker multilayer films are used, then measurement precision is improved, but manufacturing precision and productivity deteriorate
Solution Approach 1:
The patent divides the optical filter function into multiple separate optical filters, each with thinner multilayer films. Instead of using a single thick filter, the system employs multiple filters (first optical filter, second optical filter, etc.) with individual film thicknesses that are manageable and easier to manufacture, thereby improving productivity while maintaining measurement precision through the combined effect of multiple filters.
Solution Approach 2:
The patent optimizes the film thickness parameters of the multilayer films in each optical filter. By controlling the thickness of each layer within specific ranges and adjusting the overall film thickness to be within 14 μm or less, the patent achieves a balance between filter precision and manufacturability. This parameter optimization enables easier film formation processes and reduces warpage and chipping during production.
2Manufacturing precision
If thicker multilayer films are used in optical filters, then filter precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent segments the thick multilayer film into multiple thinner films across different optical filters. Each individual film layer is thinner and easier to deposit without causing warpage or chipping, while the collective effect of multiple filters achieves the desired precision. This segmentation makes the manufacturing process more manageable and improves ease of manufacture.
Solution Approach 2:
The patent changes the film thickness parameter to be within 14 μm or less for each optical filter, which is a manageable thickness that can be deposited without causing significant warpage or chipping during the film formation process. This parameter change improves ease of manufacture while maintaining sufficient filter precision through proper optical design.
3Reliability
If thicker multilayer films are used, then optical filter performance is improved, but yield decreases
Solution Approach 1:
The patent segments the optical filter system into multiple separate filters, each with thinner multilayer films that are less prone to defects during formation. Thinner films experience less stress and are less likely to chip or warp, resulting in higher yield. The combined performance of multiple thinner filters achieves the same reliability as a single thick filter while improving production yield.
Solution Approach 2:
The patent optimizes the film thickness parameter to 14 μm or less, which reduces the likelihood of defects such as warpage and chipping during film formation. This parameter change leads to fewer defective products and higher yield, while the optical performance is maintained through the multi-filter configuration and proper layer design.
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 optical module achieves improved mass productivity by reducing defects during film formation, suppressing warpage and chipping, and enhancing production stability without compromising precision.
Implementation Method 1
Different kinds of gas absorb infrared light at different wavelengths, and a non-dispersive infrared absorption gas concentration measuring device utilizes this principle and measures gas concentration by detecting the amount of absorption
Implementation Method 2
an optical filter that transmits infrared light of a specific wavelength according to the gas to be measured
Data Source
AI summary
A first and second optical filter of an optical module include 50 nm or more of a common transmission band with a transmittance of 60% or more in the wavelength range of 2000 to 10000 nm, a total of 200 nm or more of a certain wavelength range in which a transmittance difference is 20% or more outside the common transmission band, and a total of 1000 nm or more of a wavelength range in which the transmittance difference is less than 20% and the transmittance is less than 60% in a band closer to the common transmission band than the certain wavelength range on both sides of the common transmission band. A sensitivity in a cutoff band is 5% or less of the peak sensitivity as a result of multiplying a sensitivity spectrum of the infrared optical element by a transmission spectra of the plurality of optical filters.