Optical Sensor Offset Compensation for Wearable Bio Data Sensing
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Solution Overview
Problem
Existing wearable devices with optical sensors face accuracy issues in bio data sensing due to offsets in current removal circuits, which are difficult to effectively remove unnecessary photocurrent components, leading to degraded sensing accuracy.
Innovation Solution
A wearable device with an optical sensor that includes a current removal circuit with a bias voltage generator, reference voltage generator, and voltage-to-current converter, controlled by a controller to minimize offset influence by alternating input and output terminals of amplifiers, thereby removing a portion of the direct current component from the photocurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a current removal circuit with amplifier is used to remove DC component from photocurrent, then the ability to remove unwanted current is improved, but amplifier offset introduces errors that degrade measurement precision
Solution Approach 1:
The patent applies periodic action by alternately switching the amplifier between two operating states: in the first state, the amplifier processes the photocurrent signal; in the second state, the amplifier is configured to measure and capture its own offset voltage. By periodically toggling between these states and subsequently subtracting the measured offset from the signal, the system effectively removes the unwanted offset component while preserving the bio data measurement accuracy.
2Device complexity
If a simple current removal circuit is used, then device complexity is reduced, but the circuit cannot effectively compensate for offset errors
Solution Approach 1:
The patent implements self-service by designing a circuit where the same amplifier that processes the photocurrent signal also performs self-diagnosis of its own offset voltage. The amplifier alternates between signal processing mode and offset measurement mode, using its own internal resources to characterize and compensate for its deficiencies. This eliminates the need for separate offset calibration circuits or additional compensation components, achieving high precision with minimal added complexity.
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 approach minimizes errors in bio data by effectively reducing the impact of amplifier offsets, ensuring accurate and reliable sensing of bio signals such as heart rate and oxygen saturation.
Implementation Method 1
a light emitter configured to irradiate a user's body with light, a light receiver configured to generate a photocurrent by receiving reflected light from the user's body
Data Source
AI summary
A wearable device includes an optical sensor having a light emitter configured to irradiate a user's body with light and a light-receiving unit configured to receive reflected light from the user's body to generate a photocurrent, a current removal circuit configured to generate a current for removing a portion of a direct current (DC) component of the photocurrent, and a controller configured to control an operation of the current removal circuit, and generate bio data based on a current obtained by removing a portion of the DC component equivalent to the current generated by the current removal circuit from the photocurrent.