Biometric Sensor Light Guide for Crosstalk Noise Reduction
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Solution Overview
Problem
Biometric sensor modules in electronic devices face challenges with noise interference, such as crosstalk noise and stray light noise, which hinder accurate biometric information acquisition due to light not entering the user's skin or being detected by the light detector when the sensor and skin are not in close contact.
Innovation Solution
A light guide is disposed on the light path of the biometric sensor module to improve the rectilinear advancement of light and filter out noise, preventing crosstalk and stray light noise from being detected by the light detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a biometric sensor module is mounted without a light guide, then the structure is simpler and manufacturing is easier, but crosstalk noise and stray light noise are detected by the light detector, reducing measurement precision
Solution Approach 1:
A light guide is introduced as an intermediary component between the light source and light detector. The light guide channels light in a controlled manner, allowing only light that has passed through the user's skin to reach the detector while blocking direct light paths that would cause crosstalk noise. This mediator structure resolves the contradiction by enabling precise biometric measurement without significantly complicating the overall device architecture.
2Measurement precision
If the biometric sensor module is not in close contact with the user's skin, then ease of operation is improved, but stray light noise is detected by the light detector, reducing measurement precision
Solution Approach 1:
The light guide acts as an optical intermediary that maintains measurement precision even when the sensor module is not in direct contact with the skin. By channeling light through a defined path, the light guide ensures that only light interacting with the skin is detected, eliminating stray light noise that would otherwise enter when contact is poor. This allows the device to be worn comfortably without compromising measurement accuracy.
3Measurement precision
If additional processing operations are performed to remove stray light noise, then measurement precision is improved, but processing time increases and energy efficiency decreases
Solution Approach 1:
Instead of removing stray light noise through software processing after detection, the light guide performs preliminary action by physically preventing stray light from reaching the detector in the first place. The optical structure is designed to block unwanted light paths before the measurement occurs, eliminating the need for subsequent noise removal processing and thereby maintaining high processing rates and energy efficiency.
4Loss of information
If the light detector detects all light including noise, then device complexity is reduced, but loss of information occurs due to noise interference
Solution Approach 1:
The light guide serves as an optical intermediary that selectively transmits only the useful light signal while blocking noise. By positioning the light guide in the light path, it creates a controlled optical environment where only light that has interacted with the user's skin can reach the detector, preventing information loss due to noise interference without requiring complex post-processing or additional sensing 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
This solution enables the acquisition of noiseless biometric information, improves processing rate and energy efficiency of the sensor module, and enhances the comfort and functionality of wearable electronic devices by reducing noise effects.
Implementation Method 1
the light guide is disposed on the light path of the light source to improve the rectilinear advancement property of light in the traveling direction
Implementation Method 2
a light guide may be disposed on a light path of the biometric sensor module so that noise other than a signal related to a living body is not detected by the light detector
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An electronic device includes: a housing including a front plate oriented in a first direction and a rear plate oriented in a second direction; a display visible through at least a portion of the front plate; and a biometric sensor module located between the front plate and the rear plate. The biometric sensor module may include: a cover glass oriented in the second direction; at least one light source configured to emit light to the outside; a light detector disposed adjacent to the at least one light source, and configured to receive reflected light corresponding to light emitted from the light source; a light guide disposed between the light detector and the cover glass, and configured to provide a path of the reflected light received by the light detector; and a circuit board electrically connected to the at least one light source and the light detector.