Capacitive Sensor Under Display for Proximity Detection
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Solution Overview
Problem
Current front-facing proximity detection systems in devices, such as smartphones, often rely on infrared sensors which can reduce screen space, lead to mechanical issues, and cause pixel burn-in when placed under the display, increasing manufacturing costs and affecting user experience.
Innovation Solution
A capacitive sensor system is embedded under the smartphone screen, utilizing an array of electrodes coupled to a capacitance sensor and an impedance bridge to detect changes in capacitance, allowing for front-facing proximity detection without the need for infrared sensors, thus preserving screen space and reducing mechanical complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an infrared sensor is included in a notch or other area on the front side, then proximity detection function is achieved, but screen space is reduced
Solution Approach 1:
The patent combines the proximity sensing function with the existing display structure by integrating capacitive sensor electrodes into the display assembly. The sensor electrodes are positioned behind the display screen, merging the proximity detection function with the display structure, thereby eliminating the need for separate infrared sensor openings that would reduce screen space.
Solution Approach 2:
The patent introduces a capacitive sensor system as an intermediary between the user's face and the display. Instead of using optical infrared sensors that require physical openings, the capacitive sensor detects proximity through electrical field interactions, serving as a mediator that enables proximity detection without compromising screen integrity.
2Reliability
If an infrared sensor is included on a moveable element that pops out of a side of the screen, then proximity detection function is achieved, but mechanical complexity increases
Solution Approach 1:
The patent replaces the mechanical moveable element system with an electrical sensing system. Instead of using a physical sensor that pops out and moves, the capacitive sensor electrodes remain fixed behind the display and detect proximity through electrical field changes, eliminating mechanical movement and associated complexity.
Solution Approach 2:
Instead of having the sensor move to detect proximity, the patent inverts the approach by having the sensor remain stationary and detecting proximity through changes in electrical field capacitance. The sensor array stays fixed behind the display while the detected object (user's face) moves through the sensing field.
3Area of stationary object
If infrared sensors are included under the display, then screen space is preserved, but pixel burn-in occurs and manufacturing costs increase
Solution Approach 1:
The patent creates a functional copy of the proximity detection function using capacitive sensing rather than replicating the infrared sensor placement. The capacitive sensor electrodes provide a similar proximity detection capability but without the harmful effects of placing sensors directly under the display, avoiding pixel burn-in while preserving screen space.
Solution Approach 2:
The patent uses a different sensing mechanism (capacitive sensing) that is less expensive and avoids the durability issues of infrared sensors placed under the display. The capacitive sensor system is simpler, cheaper to manufacture, and eliminates the pixel burn-in problem associated with prolonged infrared sensor operation beneath the display.
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 capacitive sensor system effectively detects objects approaching the front of the device, improving user experience by maintaining screen real estate and reducing manufacturing costs while avoiding pixel burn-in and mechanical issues associated with infrared sensors.
Implementation Method 1
A capacitive sensor system is included in a device. The capacitive sensor system includes an array of sensor electrodes embedded in a device, such as under a smartphone screen, and coupled to a capacitance sensor.
Implementation Method 2
The capacitive sensor applies a voltage across the selected electrodes and measures a capacitance, or a quantity related to capacitance, between the selected electrodes.
Data Source
AI summary
A device for proximity detection includes multiple electrodes and an impedance sensor coupled to the electrodes. The impedance sensor may include three impedance elements and a sensing element arranged in a bridge configuration to offset an external impedance and detect changes to impedance in the environment of the device. The device further includes a proximity detector that obtains sensor measurements between multiple subsets of electrodes and analyzes the sensor measurements to determine whether an object is approaching the device.