Directional Capacitive Proximity Sensor Layout for Low-Power Ear Detection
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Solution Overview
Problem
Existing proximity sensors in mobile devices, particularly capacitive sensors, suffer from high power consumption and a high risk of false detections due to omnidirectional sensitivity, which is not efficiently addressed by current infrared or capacitive-based solutions.
Innovation Solution
A capacitive proximity sensor system with multiple internal and external electrodes, including a conductive shield and electronic circuit for weighted signal processing, providing improved direction discrimination and reduced power consumption by using a multi-electrode arrangement for 3D proximity detection, allowing for precise detection of body parts and rejecting false signals from irrelevant directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If capacitive sensors are used for proximity detection, then power consumption is reduced and device size is minimized, but false detection rate increases due to omnidirectional sensitivity
Solution Approach 1:
The capacitive sensor is divided into multiple independent electrodes (first electrode, second electrode, third electrode, fourth electrode) arranged at different positions and orientations. Each electrode detects capacitive changes in specific directions, allowing the system to segment the omnidirectional detection into directional components and identify the direction of approaching objects.
Solution Approach 2:
Each electrode is assigned a specific detection direction and function. The first and second electrodes detect objects approaching from the front, while the third and fourth electrodes detect objects from the back. This local specialization allows the sensor system to distinguish between relevant proximity (front) and irrelevant proximity (back/sides), reducing false detections while maintaining low power consumption.
2Measurement precision
If infrared optical sensors are used for proximity detection, then detection range and directivity are improved, but power consumption increases and device size increases
Solution Approach 1:
The patent replaces the infrared optical detection system with a capacitive sensing system. Instead of using optical components (infrared LEDs, photodetectors, lenses) that consume significant power and occupy space, the invention uses electrical capacitance measurement to detect proximity. The capacitive electrodes sense changes in electrical field caused by approaching objects, achieving detection functionality with much lower power consumption and smaller form factor.
Solution Approach 2:
The invention changes the detection parameter from optical properties (infrared light emission and detection) to electrical properties (capacitance changes). By measuring capacitive coupling between the electrodes and approaching objects, the system achieves proximity detection without the power-intensive optical components, while the multi-electrode arrangement provides the necessary directional information.
3Reliability
If the detection range of capacitive sensors is reduced to minimize false positives, then false detection rate decreases, but detection capability is severely limited
Solution Approach 1:
The patent transitions from single-point or limited-range detection to three-dimensional spatial detection by arranging electrodes in a multi-dimensional configuration. The electrodes are positioned to detect objects from different directions (front, back, sides), creating a volumetric detection space. This allows the system to maintain extended detection range while using directional information to filter out false positives from irrelevant directions.
Solution Approach 2:
The system processes signals from multiple electrodes simultaneously and uses the relative signal strengths and patterns to determine object direction. By comparing capacitive changes across different electrodes, the system can distinguish between objects approaching from the front (relevant) versus objects at the back or sides (irrelevant), maintaining detection sensitivity while reducing false positives through intelligent signal processing.
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 effectively reduces false detection rates and power consumption, enabling efficient directional proximity sensing in mobile devices with or without touch panels, while maintaining low component costs and compact size.
Implementation Method 1
one or a plurality of internal capacitive electrodes arranged for detecting electrical charges in response to proximity with a body portion
Data Source
AI summary
A proximity sensor for detecting proximity of a body portion in a first region while avoiding unwanted detection of a body portion in a second region, based on the capacities seen by a plurality of electrodes. An application of the inventive detector to a mobile phone, whereby the display is switched off, or various energy saving measure are taken, when the proximity sensor determines directional proximity with a body part, indicating that the user has brought the phone to the ear for placing a call.