Optical Capacitance Module for Precise Pressure and Touch Location
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Solution Overview
Problem
Existing capacitive input devices face challenges in accurately detecting pressure and location of user inputs due to susceptibility to environmental factors like humidity and inability to sense non-conductive objects, and strain gauge-based sensors are affected by temperature fluctuations and complexity.
Innovation Solution
A capacitance module incorporating a stack of layers with a capacitance measuring circuit and an optical pressure sensor, where deformation alters light transmission between LEDs to detect pressure and location, and a controller processes signals from multiple optical pressure sensors to determine input location and pressure values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive force sensing is used to detect pressure, then changes in capacitance can be measured, but the sensor is susceptible to environmental factors like humidity and cannot detect non-conductive objects
Solution Approach 1:
The patent replaces traditional capacitive sensing with optical sensing using LEDs and photodetectors. Light transmission through the deformable layer is measured, converting mechanical deformation into optical signal changes. This substitution eliminates susceptibility to humidity and electromagnetic interference while enabling detection of non-conductive objects through optical rather than electrical means.
Solution Approach 2:
The patent introduces an optical intermediary (light) as the mediator between the deformable layer and the detection system. Instead of directly measuring electrical capacitance changes, the system uses light transmission through the deformable layer as an intermediary to detect pressure, thereby isolating the sensing mechanism from environmental electrical interference.
2Measurement precision
If strain gauge-based pressure sensing is used, then force measurement is enabled, but the sensors are affected by temperature fluctuations and involve complex calibration
Solution Approach 1:
The patent replaces strain gauge-based mechanical sensing with optical sensing. Instead of measuring resistance changes in strain gauges that are sensitive to temperature, the system uses light transmission through the deformable layer, which is inherently less sensitive to temperature fluctuations and eliminates complex electrical calibration requirements.
Solution Approach 2:
The patent changes the measurement parameter from electrical resistance (in strain gauges) to optical transmission properties. By measuring light intensity transmission through the deformable layer rather than electrical resistance, the system achieves temperature insensitivity and simplified calibration, as optical properties of the materials remain more stable under temperature variations.
3Measurement precision
If dual sensors are used to measure forces over a greater range, then measurement range is extended, but device complexity increases
Solution Approach 1:
The patent makes the optical sensing system multi-functional by using the same LED-photodetector pairs to detect both pressure magnitude and input location. Instead of requiring separate sensor arrays for different measurement types, the optical system simultaneously provides comprehensive force measurement capabilities across the entire input surface, reducing overall device 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
The solution provides robust and accurate detection of pressure and location of user inputs, unaffected by environmental factors, with enhanced sensitivity and reduced complexity.
Implementation Method 1
an optical pressure sensor incorporated into the stack of layers aligned within the input sensitive area. The optical pressure sensor may be configured to detect deformation from a user input to the stack of layers within the capacitance input sensitive area.
Implementation Method 2
The optical pressure sensor may include a transmission light emitting diode (LED) and a measurement LED.
Data Source
AI summary
A capacitance module may include a stack of layers, a capacitance measuring circuit disposed on at least on of the layers of the stack of layers, the capacitance measuring circuit defining a capacitance input sensitive area associated with a face of the at least one layer, an optical pressure sensor incorporated into the stack of layers aligned within the input sensitive area, and a controller in communication with the capacitance measuring circuit and the optical pressure sensor, where the optical pressure sensor is configured to detect deformation from a user input to the stack of layers within the capacitance input sensitive area.