Optical Filter with Dielectric Multi-Layer Film for Noise Reduction
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Solution Overview
Problem
Near infrared light used in optical sensors often includes noise from visible light, leading to decreased detection accuracy, and existing filters lack sufficient light fastness and moisture resistance, affecting long-term performance.
Innovation Solution
An optical filter configuration incorporating a near infrared transmitting filter with a dielectric multi-layer film or an organic layer between the dielectric multi-layer film and the near infrared transmitting filter, which selectively transmits desired wavelengths and suppresses noise, improving detection accuracy and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a near infrared transmitting filter is used to detect near infrared light, then detection capability is improved, but noise from visible light increases leading to decreased detection accuracy
Solution Approach 1:
The optical filter is segmented into multiple functional layers: a first optical filter layer that transmits near infrared light while blocking visible light, and a second optical filter layer that further refines the wavelength selection. This segmentation allows the filter to selectively transmit desired near infrared wavelengths while blocking visible light noise, thereby improving detection accuracy without sacrificing near infrared transmission capability
Solution Approach 2:
Different regions of the optical filter have different optical properties optimized for specific functions. The first optical filter layer is designed with local quality characteristics to transmit near infrared light (700-1100 nm) while the second layer provides localized wavelength selection to block visible light. This local quality differentiation enables the filter to simultaneously achieve high near infrared transmission and effective visible light noise rejection
2Reliability
If the wavelength of light used for detection is increased to use near infrared light, then invisibility to subjects and reduced scattering are achieved, but sensitivity of the optical sensor decreases
Solution Approach 1:
The optical filter parameters are specifically designed to compensate for the reduced sensitivity at near infrared wavelengths. The first optical filter layer transmits near infrared light with a peak transmission wavelength of 700-1100 nm, and the second layer is configured to maintain adequate transmission in this range. By optimizing the filter parameters (wavelength ranges, transmission percentages), the system maintains reliability through near infrared usage while mitigating the sensitivity decrease through careful parameter selection
3Duration of action of stationary object
If existing near infrared transmitting filters are used, then detection capability is achieved, but light fastness and moisture resistance are insufficient affecting long-term performance
Solution Approach 1:
The optical filter uses a composite structure combining a first optical filter layer and a second optical filter layer with different material properties. The first layer provides near infrared transmission functionality while the second layer enhances durability with improved light fastness and moisture resistance. This composite material approach allows the filter to maintain both detection capability and long-term reliability under various environmental conditions
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 proposed filter configuration enhances detection accuracy by reducing noise and improving light fastness and moisture resistance, ensuring consistent performance over time.
Implementation Method 1
a dielectric multi-layer film that is provided on the near infrared transmitting filter
Implementation Method 2
a near infrared transmitting filter... at least two wavelengths at which a transmittance in a wavelength range of 600 nm or longer and shorter than 1050 nm is 50%
Data Source
AI summary
Provided are an optical filter having excellent light fastness and moisture resistance and having excellent detection accuracy, a structure, and an optical sensor. An optical filter 10a includes a near infrared transmitting filter 1 and a dielectric multi-layer film 2. In this optical filter, the dielectric multi-layer film 2 and the near infrared transmitting filter 1 are in contact with each other, or an organic layer 3 is provided between the dielectric multi-layer film 2 and the near infrared transmitting filter 3. In the optical filter, at least two wavelengths at which a transmittance in a wavelength range of 600 nm or longer and shorter than 1050 nm is 50% are present, and in a case where a wavelength on a shortest wavelength side is represented by λ1 and a wavelength on a longest wavelength side is represented by λ2 among the wavelengths at which the transmittance is 50%, predetermined conditions are satisfied.