Near-Infrared Phosphor Composition for CMOS Vital Sensing
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Solution Overview
Problem
Existing light emitting devices used in noncontact vital sensing systems have insufficient emission intensity in the near-infrared range, failing to adequately cover the low light receiving sensitivity of general CMOS image sensors, leading to inaccuracies in vital information acquisition, especially in varying lighting conditions.
Innovation Solution
A phosphor represented by the formula (Gd1-x-y, Ln y, M II< x ) 3 M III< 2 (Ga1-z, M IV< z ) 3 O 12 :Cr3+< is used in a wavelength converter to emit near-infrared light, complementing the sensitivity of CMOS image sensors, with specific elements like Ca, Sr, Ga, and Ge enhancing the internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light emitting device outputs only visible radiation, then the device can be simple in configuration, but the light receiving sensitivity in the near-infrared range is insufficient for accurate vital information acquisition
Solution Approach 1:
The patent uses a composite phosphor material containing Gd3+, Cr3+, and Mn2+ ions in a garnet crystal structure. This composite material simultaneously emits visible light (from Gd3+ and Mn2+) and near-infrared light (from Cr3+), allowing a single light emitting device to provide both visible illumination and near-infrared radiation for accurate vital information acquisition, resolving the contradiction between device simplicity and measurement reliability
Solution Approach 2:
The light emitting device is designed to perform multiple functions: it provides visible light for general illumination and simultaneously emits near-infrared light for vital information sensing. This multi-functionality eliminates the need for separate light sources for different wavelength ranges, maintaining device simplicity while improving the reliability of vital information acquisition
2Reliability
If a light emitting device outputs visible radiation and near-infrared radiation, then the light receiving sensitivity in the near-infrared range is improved, but the emission intensity in the near-infrared range is still insufficient to cover the low sensitivity of CMOS image sensors
Solution Approach 1:
The patent optimizes the concentration parameters of the phosphor components, specifically setting Cr3+ concentration at 0.005≤x<0.05 and Mn2+ concentration at 0.05<y≤0.2, while maintaining the charge balance condition 3x+2y=z. These parameter changes maximize the near-infrared emission intensity from Cr3+ while ensuring sufficient visible light output, thereby covering the low sensitivity region of CMOS image sensors in the near-infrared range
Solution Approach 2:
The patent enhances the near-infrared emission characteristics locally within the phosphor material by introducing Cr3+ ions at specific concentration ranges. This localized optimization of emission properties at the material level ensures that the near-infrared emission intensity is sufficiently high to compensate for CMOS sensor sensitivity limitations, without compromising the visible light output
3Measurement precision
If the emission spectrum of the light emitting device does not match the light receiving sensitivity of the camera, then the device configuration can be simplified, but the accuracy of vital information obtained deteriorates
Solution Approach 1:
The patent employs a composite phosphor with multiple active ions (Gd3+, Cr3+, Mn2+) that naturally produce an emission spectrum covering both visible and near-infrared regions. This composite material approach simplifies device configuration by using a single phosphor type while achieving the complex spectrum-matching requirement for high-accuracy vital information measurement across different wavelength ranges
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 high fluorescence intensity in the red to near-infrared range, enabling accurate vital information acquisition even with low-sensitivity CMOS image sensors, improving the reliability of noncontact vital sensing systems.
Implementation Method 1
A phosphor represented by the formula (Gd1-x-y, Lny, MIIx)3MIII2(Ga1-z, MIVz)3O12:Cr3+ has a fluorescence peak within a wavelength range of 750 nm or more and less than 900 nm
Data Source
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AI summary
Provided is a phosphor 4 represented by general formula (1) below, [Chemical formula 1] (Gd1-x-y, Lny, MIIx)3MIII2(Ga1-z, MIVz)3O12:Cr3+ ... (1) (In the formula, Ln is one or more elements selected from La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb, and Lu, MII is a divalent element, MIII is a trivalent element, MIV is a tetravalent element, and x, y, and z satisfy 0 < x < 0.5, 0 ≤ y < 0.5, and 0 < z < 0.5.)