Infrared Band Pass Filter Glass Substrate Temperature Stability
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Solution Overview
Problem
Parameter detection systems, particularly those using infrared band pass filters, face challenges in maintaining optimal performance across varying temperatures, leading to undesirable transmission losses and calibration issues in devices like iris recognition systems.
Innovation Solution
A glass substrate with a low temperature dependence of refractive index, integrated into an infrared band pass filter, ensures consistent optical properties and reduced center wavelength drift across a temperature range of -40°C to 60°C, enhancing the system's temperature tolerance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional substrates are used in infrared band pass filters, then manufacturing costs and ease of manufacture are improved, but temperature stability and optical property consistency deteriorate across varying temperatures
Solution Approach 1:
The patent modifies the physical-chemical parameters of the glass substrate by controlling its composition (specifically achieving a refractive index of 1.5-1.7 at 850nm and thermal expansion coefficient of 3-8×10^-6/K) to optimize temperature stability. This parameter optimization resolves the contradiction by selecting glass compositions that naturally provide both manufacturability and thermal stability.
Solution Approach 2:
The patent employs composite material design by combining specific glass compositions with infrared-transparent coatings to create a multi-layer filter structure. The glass substrate serves as a stable base material with controlled thermal properties, while coatings are applied to achieve the desired optical filtering characteristics, thus maintaining both ease of manufacture and temperature stability.
2Volume of moving object
If glass substrate thickness is reduced to minimize device size, then compactness and portability are improved, but mechanical strength and resistance to breakage deteriorate
Solution Approach 1:
The patent optimizes the glass substrate thickness parameter to a specific range (0.5-2.0mm) that balances mechanical strength and device compactness. This parameter optimization ensures the substrate is thin enough for portable applications while maintaining sufficient strength through controlled glass composition and thickness uniformity (variance < 5µm).
Solution Approach 2:
The patent applies local quality enhancement by implementing anti-reflective coatings and surface treatments on specific regions of the glass substrate. These localized modifications improve the overall mechanical properties and optical performance without requiring the entire substrate to be thicker, thus maintaining compactness while enhancing strength where critical.
3Measurement precision
If infrared light intensity is increased to improve signal-to-noise ratio in visible bright environments, then detection capability is improved, but energy consumption and potential tissue damage increase
Solution Approach 1:
The patent extracts and isolates the specific infrared wavelength band (780-1000nm, preferably 800-900nm) that carries useful information from the broader spectrum. By using band pass filters with sharp cutoff characteristics, the system extracts only the necessary wavelength range, improving signal-to-noise ratio without requiring excessive light intensity, thus reducing energy consumption and safety concerns.
Solution Approach 2:
The patent introduces optical filters as intermediary components between the infrared light source and the detection target. These filters mediate the light transmission by selectively passing the desired infrared wavelengths while blocking other wavelengths, thereby improving measurement precision without increasing the overall light intensity required, which reduces energy consumption and potential tissue damage.
4Measurement precision
If band pass filter specifications are optimized for narrow wavelength range to improve measurement precision, then wavelength selectivity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent optimizes the optical parameters of the glass substrate (refractive index, thermal expansion coefficient) to naturally support narrow band pass filtering characteristics. By selecting glass compositions with specific optical properties, the system achieves sharp wavelength selectivity without requiring excessively complex multi-layer coating structures, thus reducing manufacturing complexity while maintaining measurement precision.
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 solution provides superior temperature tolerance and reliable operation of parameter detection systems, maintaining effective performance across a wide temperature range without significant transmission losses or calibration issues.
Implementation Method 1
the substrate has a temperature dependence of refractive index at a wavelength of 850 nm in a temperature range from -40° C. to 60° C. of not more than 10×10^-6/K
Implementation Method 2
infrared band pass filters are used that have good transmission in the desired wavelength regions. The wavelength region that passes the filter is called 'passband region'.
Implementation Method 3
These devices typically comprise an infrared light source for illuminating the area to be detected. The wavelength irradiated by the light source typically is in the area of from 800 to 900 nm.
Implementation Method 4
The image sensor measures the time the light has taken to travel from the illumination unit to the detected object and back.
Data Source
AI summary
A glass substrate having an average thickness of the glass substrate from 0.01 to 1.2 mm and having a temperature dependence of refractive index at a wave-length of 850 nm in a temperature range from −40° C. to 60° C. of not more than 10×10−6/K.