Piezoelectric Proximity Detection with Capacitance and Ultrasonic Sensing
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Solution Overview
Problem
Existing touch panels cannot detect objects, such as hands, that are at a distance away from the operation surface, limiting the detection range.
Innovation Solution
A proximity detection device utilizing a piezoelectric body with first and second electrodes for capacitance detection and ultrasonic transmission/reception, combined with a charge measurement unit, to detect objects both near and far from the operation surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor is used for touch detection, then touch and touch position can be detected on the touch surface, but the detection distance is limited and objects at a distance cannot be detected
Solution Approach 1:
The patent combines a capacitive sensor unit for near-field touch detection with an ultrasonic sensor unit for far-field object detection into a single proximity detection device. This merging allows the device to detect objects at various distances by utilizing both sensing mechanisms, thereby resolving the limitation of capacitive sensors alone which can only detect objects in direct contact or very close proximity to the touch surface.
Solution Approach 2:
The proximity detection device is designed with multi-functionality to perform both capacitive touch detection and ultrasonic distance detection. The device can switch between these two detection modes or use both simultaneously depending on the distance to the object, making it universally applicable for detecting objects ranging from direct contact to several feet away, thus enhancing its adaptability across different detection scenarios.
2Measurement precision
If only capacitive sensing is used, then the device structure remains simple, but the detection distance is limited
Solution Approach 1:
The sensor unit is segmented into two distinct functional components: a capacitive sensor unit for detecting objects in close proximity and an ultrasonic sensor unit for detecting objects at a distance. This segmentation allows each component to be optimized for its specific detection range while working together to provide comprehensive distance detection capability, balancing the trade-off between structural complexity and detection performance.
Solution Approach 2:
The patent extends the detection capability from a two-dimensional touch surface detection to a three-dimensional spatial detection by adding the ultrasonic sensing dimension. While the capacitive sensor handles objects on or near the surface, the ultrasonic sensor adds the ability to detect objects in the air above the surface at various distances, effectively adding a vertical detection dimension that resolves the distance limitation.
3Measurement precision
If capacitive sensor detects touch on surface, then touch position is detected accurately, but objects separated from operation surface cannot be detected
Solution Approach 1:
The patent merges capacitive sensing and ultrasonic sensing capabilities into a unified proximity detection system. The capacitive sensor continues to provide accurate detection for objects on or near the operation surface, while the ultrasonic sensor extends this capability to detect objects that are separated from the surface by a greater distance, thereby maintaining measurement precision across different detection ranges.
Solution Approach 2:
The ultrasonic sensor acts as an intermediary detection mechanism for objects that are too far away for direct capacitive detection. When an object is positioned at a distance beyond the capacitive sensor's effective range, the ultrasonic sensor transmits sound waves that reflect off the object and return to the detector, serving as an intermediary method to bridge the detection gap and enable accurate proximity measurement for distant objects.
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 detection of objects at various distances by switching between capacitance and ultrasonic methods, providing a simple configuration for accurate detection of object proximity and shape.
Implementation Method 1
a proximity detection unit that has a piezoelectric body and first and second electrodes disposed in contact with the piezoelectric body
Implementation Method 2
first and second electrodes disposed in contact with the piezoelectric body to detect proximity of an object
Implementation Method 3
a charge measurement unit connected to at least one of the first and second electrodes to measure electric charge
Data Source
AI summary
A proximity detection device with a detection distance for detecting an object separated to some extent from an operation surface is provided. The proximity detection device includes a proximity detection unit that has a piezoelectric body and first and second electrodes disposed in contact with the piezoelectric body to detect proximity of an object, a signal applying unit that causes the proximity detection unit to perform capacitance detection and ultrasonic transmission and/or ultrasonic reception by applying a plurality of signals of different frequencies to at least one of the first and second electrodes, and a charge measurement unit connected to at least one of the first and second electrodes to measure electric charge.