Dual Near-Infrared Filters for Optical Sensor Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical sensors face challenges in reducing noise from visible light when detecting near infrared light, which affects their sensitivity and accuracy.
Innovation Solution
A structure comprising a support with a first and second near infrared transmitting filter, where the second filter shields longer wavelengths than the first, and a band pass filter, allowing for improved noise reduction and sensitivity by correcting light transmission and performing noise subtraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single near infrared transmitting filter is used to block visible light, then visible light noise is reduced, but near infrared light transmission is insufficient and sensitivity is limited
Solution Approach 1:
The patent divides the filtering function into two separate near infrared transmitting filters with different spectral characteristics. The first filter blocks visible light while transmitting near infrared light, and the second filter transmits a different wavelength range of near infrared light. This segmentation allows each filter to be optimized for its specific function, resolving the contradiction between noise reduction and light transmission.
Solution Approach 2:
The patent uses composite filtering structures where multiple filters with different spectral properties are combined. By compositeing the first and second near infrared transmitting filters, the system achieves both visible light blocking and enhanced near infrared light transmission across multiple wavelength ranges, simultaneously improving sensing accuracy and reliability.
2Reliability
If multiple filters are added to improve near infrared light transmission, then sensitivity is enhanced, but device complexity increases
Solution Approach 1:
The filtering system is segmented into two distinct filters placed at different positions, each with specific spectral characteristics. This segmentation allows for modular design where each filter can be independently optimized and replaced, managing complexity through functional division rather than a single complex filter.
Solution Approach 2:
Each filter is designed with local quality - the first filter has optimized characteristics for blocking visible light while transmitting specific near infrared wavelengths, and the second filter has different local characteristics for transmitting complementary near infrared wavelengths. This local optimization reduces overall system complexity by distributing functional requirements across specialized components.
3Adaptability or versatility
If filters with different spectral characteristics are used to detect multiple near infrared wavelengths, then detection capability is improved, but noise from visible light increases
Solution Approach 1:
The detection system is segmented into two filtering paths, each optimized for different near infrared wavelength ranges. The first filter path handles one wavelength range while blocking visible light, and the second filter path handles another wavelength range. This segmentation enables multi-wavelength detection capability while maintaining effective visible light noise rejection in each path.
Solution Approach 2:
The patent changes the spectral parameters of the two filters to operate at different near infrared wavelengths. By adjusting the transmission characteristics of each filter, the system achieves versatile detection capability across multiple wavelengths while each filter independently maintains strong visible light blocking performance, preventing noise infiltration.
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 enables detection of light with reduced noise and high sensitivity, allowing for simultaneous detection of near infrared light components with different wavelengths, enhancing the accuracy of applications like iris recognition and distance measurement.
Implementation Method 1
the first near infrared transmitting filter shields at least a part of visible light
Implementation Method 2
the second near infrared transmitting filter shields light up to a longer wavelength than a wavelength of the light shielded by the first near infrared transmitting filter
Data Source
AI summary
A structure includes a support and a first near infrared transmitting filter and a second near infrared transmitting filter that are provided at different positions on the support. A minimum value of a transmittance to light having a longer wavelength than longest wavelengths at which transmittances of the first near infrared transmitting filter and the second near infrared transmitting filter in a wavelength range of 600 to 1300 nm are 50% is 50% or higher, and a difference between a wavelength λ2 of light having the longest wavelength at which the transmittance of the second near infrared transmitting filter is 50% and a wavelength λ1 of light having the longest wavelength at which the transmittance of the first near infrared transmitting filter is 50% is 30 nm or longer.