Ambient Light Filter for Heart Rate Sensor Noise Reduction
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Solution Overview
Problem
Ambient light interference significantly affects the accuracy of heart rate detection sensors by masking small fluctuations in reflected light, and existing solutions either increase power consumption or fail to dynamically filter changing ambient light conditions.
Innovation Solution
An ambient light filter is introduced, comprising a sample and detection circuit, current amplifier, and control circuit that switches between modes to sample and filter ambient light noise from the optical current, allowing for dynamic filtering without increasing power consumption by detecting ambient light during optical pulse gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ambient light filtering is implemented using conventional methods, then detection accuracy is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic sampling of ambient light during optical pulse gaps. The control circuit switches the sample and detection circuit to first mode during these gaps to sample ambient light, then switches to second mode for normal detection. This periodic action allows ambient light filtering without continuous operation of the filtering circuit, thereby reducing power consumption while maintaining detection accuracy.
Solution Approach 2:
The patent performs preliminary sampling of ambient light during the optical pulse gaps before the next optical pulse arrives. By capturing ambient light characteristics in advance during the gaps, the system can compensate for ambient light interference in the subsequent detection phase without requiring continuous high-power filtering operations.
2Measurement precision
If fixed time period ambient light detection is used, then some ambient light filtering is achieved, but dynamic ambient light changes cannot be effectively filtered
Solution Approach 1:
The patent establishes a feedback mechanism where the control circuit continuously monitors the optical current and dynamically switches between first and second modes based on the presence of optical pulses. The sampled ambient light information from the first mode feeds into the detection process in the second mode, creating a closed-loop system that adapts to changing ambient light conditions in real-time.
Solution Approach 2:
The patent makes the detection system dynamic by implementing mode switching capability. The control circuit dynamically transitions between first mode (ambient light sampling) and second mode (normal detection) based on the optical pulse timing. This dynamic adaptation allows the system to effectively filter ambient light regardless of how rapidly lighting conditions change.
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
This solution enhances the accuracy of heart rate detection sensors by effectively filtering ambient light noise, maintaining detection accuracy without increasing power consumption, even in dynamic lighting conditions.
Implementation Method 1
The photo sensor may initially convert measured changes into optical signal changes, and then convert the optical signal to an electric signal by the photo element
Data Source
AI summary
An ambient light filter configured to filter ambient light noises from an optical current that is at least partially caused by an optical pulse sequence emitted by a light emitting device, can include: a sample and detection circuit configured to sample the optical current and to obtain a current component in a first mode, and to remove the current component from the optical current and to generate a detection signal in a second mode; a current amplifier configured to receive the detection signal, and to generate an amplified current signal; and a control circuit configured to switch the sample and detection circuit between the first and second modes, where the control circuit switches the sample and detection circuit to the first mode in at least one optical pulse gap, and switches the sample and detection circuit to the second mode when a next optical pulse arrives.