Band Pass Filter Structure for Temperature-Stable Sensor SNR
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Solution Overview
Problem
Existing distance-measuring sensors face a decrease in signal-to-noise ratio (SN ratio) due to environmental temperature changes, particularly when using light sources with narrow luminescence peaks, as the deviation between luminescence and transmission wavelengths leads to reduced light incidence and increased noise.
Innovation Solution
A sensor design incorporating a band pass filter with a band pass layer and support where the thermal expansion coefficient of the layer is greater than the support's, and the elastic modulus of the layer is less than the support's, ensuring the transmission wavelength adapts to temperature changes, maintaining high SN ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow band pass filter with small half-width is used to suppress external light and improve SN ratio, then the SN ratio is improved, but the transmission wavelength deviates from the luminescence wavelength of the light source due to temperature changes, reducing the amount of light incident into the light-receiving element
Solution Approach 1:
The patent applies parameter changes by selecting a band pass filter material whose transmission wavelength shifts in response to temperature changes. Specifically, the transmission wavelength of the band pass filter is designed to increase with temperature increase, matching the wavelength shift characteristic of the light source, thereby maintaining alignment between transmission and luminescence wavelengths across temperature variations.
Solution Approach 2:
The patent utilizes thermal expansion effects by choosing a band pass filter material that exhibits thermal expansion characteristics. The transmission wavelength of the band pass filter changes in response to thermal expansion/contraction of the filter material, allowing the filter to dynamically track the light source wavelength shifts due to temperature changes and maintain optimal light transmission.
2Reliability
If a wide band pass filter with large half-width is used to maintain transmission wavelength alignment with light source under temperature changes, then the light incidence is maintained, but external light cannot be sufficiently cut, reducing noise suppression
Solution Approach 1:
The patent applies parameter changes by selecting a band pass filter material whose transmission wavelength shifts in response to temperature changes. Specifically, the transmission wavelength of the band pass filter is designed to increase with temperature increase, matching the wavelength shift characteristic of the light source, thereby maintaining alignment between transmission and luminescence wavelengths across temperature variations.
Solution Approach 2:
The patent utilizes thermal expansion effects by choosing a band pass filter material that exhibits thermal expansion characteristics. The transmission wavelength of the band pass filter changes in response to thermal expansion/contraction of the filter material, allowing the filter to dynamically track the light source wavelength shifts due to temperature changes and maintain optimal light transmission.
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 sensor maintains a high SN ratio and accurate measurements despite environmental temperature fluctuations by aligning luminescence and transmission wavelengths, effectively suppressing noise and improving measurement accuracy.
Implementation Method 1
a thermal expansion coefficient of the band pass layer is greater than a thermal expansion coefficient of the support, and an elastic modulus of the band pass layer is less than an elastic modulus of the support
Data Source
AI summary
Provided are: a sensor that is used as a distance-measuring sensor or the like and where a high SN ratio can be obtained and high-accuracy measurement can be performed even in a case where an environmental temperature changes; and a band pass filter that is used for the sensor. The sensor includes: a light source; a band pass filter; and a light-receiving element, in which the band pass filter includes a band pass layer and a support that supports the band pass layer, and in a case where a thermal expansion coefficient of the band pass layer is represented by α1, an elastic modulus of the band pass layer is represented by E1, a thermal expansion coefficient of the support is represented by α2, and an elastic modulus of the support is represented by E2, α1>α2 and E1<E2 are satisfied.