Refractive Index Gradient in Optical Sensor Cover to Reduce Stray Light
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Solution Overview
Problem
Existing detecting devices for non-invasive measurement of biological information, such as pulse waves, face accuracy issues due to stray light from the light-emitting portion being reflected by the cover member and incident on the light-receiving portion, leading to decreased detection accuracy.
Innovation Solution
A detecting device configuration that includes a light-emitting unit, a light-receiving unit, a holding member, a sealing member, a cover member, and a light transmissive member with refractive indices satisfying the relationship n1 ≤ n2 ≤ n3, where n1 is the refractive index of the sealing member, n2 is the refractive index of the light transmissive member, and n3 is the refractive index of the cover member, along with a wall member for light shielding to prevent direct light emission from the light-emitting unit to the light-receiving unit, effectively reducing stray light and enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cover member is provided to protect the light-emitting unit and light-receiving unit, then the device structure is improved and protected, but stray light is reflected by the back surface of the cover member and incident on the light-receiving portion, decreasing detection accuracy
Solution Approach 1:
A light transmissive member is introduced as an intermediary between the sealing member and the cover member. This intermediate layer has a refractive index that satisfies n1≤n2≤n3, serving as a mediator to gradually transition the refractive index from the sealing member to the cover member, thereby reducing reflection and preventing stray light from reaching the light-receiving portion.
Solution Approach 2:
The refractive index parameter is changed by introducing a light transmissive member with an intermediate refractive index value between the sealing member and the cover member. By satisfying the relationship n1≤n2≤n3, the gradual change in refractive index reduces reflection at interfaces, thereby reducing stray light while maintaining the protective function of the cover member.
2Measurement precision
If the refractive index of the light transmissive member is equal to or less than the refractive index of the cover member, then stray light is reduced and detection accuracy is improved, but additional structural components are required
Solution Approach 1:
The light transmissive member is positioned between the sealing member and the cover member, merging multiple functional layers into a compact integrated structure. This intermediate member combines light transmission functionality with refractive index management, achieving stray light reduction without requiring separate complex optical components.
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 significantly reduces stray light components and improves the signal-to-noise ratio, leading to higher detection accuracy and reduced power consumption by ensuring efficient light emission and reception, thereby enhancing the measurement of biological information like pulse waves and oxygen saturation.
Implementation Method 1
a light transmissive member that is between the sealing member and the cover member, wherein n1≤n2≤n3 where n1 is a refractive index of the sealing member, n2 is a refractive index of the light transmissive member, and n3 is a refractive index of the cover member
Data Source
AI summary
The detecting device according to the present disclosure includes a light-emitting portion emitting light, a light-receiving portion receiving the light emitted from the light-emitting portion and exiting from a living body, a holding member holding the light-emitting portion and the light-receiving portion, a sealing member sealing the light-emitting portion and the light-receiving portion, a cover member covering the holding member sealed by the sealing member, and a light transmissive member interposed between the sealing member and the cover member, wherein n1≤n2≤n3, where n1 is a refractive index of the sealing member, n2 is a refractive index of the light transmissive member, and n3 is a refractive index of the cover member.