Capacitive Sensing in Uniform Conductors via Dielectric Intermediary
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Solution Overview
Problem
Capacitive input sensing devices are hindered by the presence of uniform conductors, such as water, which saturates the device and makes it difficult to detect changes in capacitance caused by input objects.
Innovation Solution
A processing system and method for capacitive input devices that includes sensor electrodes and a determination module to detect the presence of a uniform conductor and determine the presence or position of input objects based on displacement of the conductor by dielectric objects, allowing for effective sensing even when submerged in water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive sensing is performed in the presence of a uniform conductor (e.g., water), then the device can operate in submerged environments, but the uniform conductor saturates the device and makes capacitance changes undetectable
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the sensor electrode and the uniform conductor (water). This dielectric layer has different permittivity than the water, creating a refractive index difference that allows total internal reflection to occur at the interface. The reflected light carries information about the presence and position of input objects through changes in the optical path, enabling detection without direct electrical contact and avoiding saturation of the sensor by the conductive medium.
Solution Approach 2:
The patent replaces direct electrical capacitive sensing with optical sensing. Instead of measuring capacitance changes directly through the conductive medium (which causes saturation), the system uses light propagation and total internal reflection at the dielectric-water interface. Input objects modify the optical path by changing the refractive index or blocking light, and these optical changes are detected and converted into position information, substituting electrical measurement with optical measurement to avoid the saturation problem.
2Reliability
If sensor electrodes directly contact the uniform conductor to enable sensing, then the device can detect input objects, but the conductor saturates the sensor and prevents detection of capacitance changes
Solution Approach 1:
A dielectric layer is positioned between the sensor electrode and the uniform conductor (water) to serve as an optical intermediary. This layer enables total internal reflection at the dielectric-water interface when light strikes at appropriate angles. The presence and position of input objects alter the optical path through refractive index changes or light blocking, which are detected as changes in reflected light intensity or pattern, providing reliable detection without direct electrical contact.
Solution Approach 2:
The patent transitions from electrical domain sensing to optical domain sensing. By using light propagation, reflection, and refraction phenomena instead of electrical capacitance measurement, the system operates in a different physical dimension that is not affected by the conductive properties of water. This dimensional transition allows the sensor to function reliably in environments that would saturate traditional capacitive sensors.
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
Enables reliable detection of input objects and their positions in sensing regions submerged in uniform conductors by differentiating between the input objects and the conductor through dielectric constants and displacement, effectively overcoming the saturation issue.
Implementation Method 1
capacitive input sensing in the presence of a uniform conductor... determine a displacement of at least part of the uniform conductor from a region of the input surface by an input object based at least in part on a change in capacitance measured on a subset of the plurality of sensor electrode
Data Source
AI summary
In an example, a processing system for a capacitive input device includes: a sensor module including sensor circuitry, the sensor module configured to: operate a plurality of sensor electrodes to determine input in a sensing region of the input device; a determination module configured to: determine that an input surface of the input device is at least partially interfacing a uniform conductor; and determine a displacement of at least part of the uniform conductor from a region of the input surface by an input object based at least in part on a change in capacitance measured on a subset of the plurality of sensor electrodes; determine at least one of a presence or position of the at least one input object on the input surface based on the determined displacement.