Camera ISP Parameter Changes for Contactless SpO2 Accuracy
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Solution Overview
Problem
Conventional remote photoplethysmography (rPPG) applications using commercial cameras struggle with robustness to light variability, making it challenging to accurately estimate peripheral oxygen saturation (SpO2) due to the complexity of digital camera image processing and the inability to control ambient light.
Innovation Solution
A method utilizing a camera with controlled ambient light and disabled image signal processor settings, combined with a machine learning model to process time-dependent signals from skin pixels, enabling accurate SpO2 estimation through a contactless sensor system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional digital cameras with unmodified ISP are used for remote SpO2 measurement, then the device is readily applicable to smartphone users, but the system suffers from poor robustness to light variability and inaccurate SpO2 estimation
Solution Approach 1:
The patent modifies multiple parameters of the image signal processor including disabling auto-white-balance, disabling bad pixel correction, disabling Bayer domain hardware noise reduction, disabling high-order lens-shading compensation, and disabling de-mosaic filtering. These parameter changes transform the camera from a conventional photography device to a measurement device that captures raw light data suitable for SpO2 estimation, thereby improving measurement precision while maintaining ease of manufacture through software configuration.
2Ease of operation
If conventional rPPG applications use commercial cameras with full ISP processing, then the system is easy to implement, but the processing complexity and inability to control ambient light reduce measurement reliability
Solution Approach 1:
The patent extracts and removes the image signal processing stage from the conventional camera pipeline by disabling multiple ISP functions. This extraction allows the system to work directly with raw sensor data, eliminating the harmful effects of automated processing that interfere with SpO2 measurement accuracy. The approach maintains ease of operation by using existing camera hardware while improving reliability through selective removal of processing steps.
3Adaptability or versatility
If ambient light is used as input for remote camera-based pulse oximetry, then the system can be implemented with existing cameras, but the uncontrolled ambient light creates technical challenges for accurate measurement
Solution Approach 1:
The patent changes the operational parameters of the camera to suit measurement purposes rather than photography. By disabling auto-white-balance and other adaptive processing features, the camera operates in a fixed, known state that simplifies the processing required to extract SpO2 information from ambient light. This parameter change reduces device complexity by eliminating the need to compensate for variable ISP processing while maintaining adaptability to use existing camera hardware.
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 system provides reliable and accurate SpO2 estimation in various environments, overcoming the limitations of conventional methods by enhancing the robustness to light variability and improving measurement precision.
Implementation Method 1
Peripheral oxygen saturation (SpO2) is estimated by measuring the amount of light that is transmitted or reflected by skin tissue in two well-chosen wavelengths
Implementation Method 2
The different hemoglobin types (e.g., oxyhemoglobin and deoxyhemoglobin) have different color responses to light based on oxygen saturation
Data Source
AI summary
Embodiments of the present disclosure relate to a method of estimating peripheral oxygen saturation (SpO2) in a human subject, and devices and apparatuses configured to perform the same.