Capacitive Sensor Array for Foreign Object Detection in Media Stacks
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Solution Overview
Problem
Existing solutions for detecting foreign objects in self-service terminals, such as ATMs and interactive kiosks, are either expensive and complex or unable to identify non-metallic objects like rubber bands or plastic paper clips, leading to potential damage to terminal components and increased service calls.
Innovation Solution
A capacitive sensor array system that uses clamping plates with capacitive electrodes to detect both metallic and non-metallic foreign objects by measuring capacitance changes when media items are inserted, preventing damage and facilitating user notification to remove the objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a metal detector is used to identify foreign objects, then metallic foreign objects such as staples and metallic paper clips can be detected, but non-metallic foreign objects such as rubber bands or plastic paper clips cannot be identified
Solution Approach 1:
The patent replaces the metal detector (electromagnetic detection system) with a capacitive sensor array that uses electrical field-based capacitance measurement. This substitution enables detection of both metallic and non-metallic foreign objects by measuring changes in capacitance caused by any object with different dielectric properties than the surrounding medium, thereby expanding detection coverage while maintaining detection precision.
Solution Approach 2:
The patent changes the detection parameter from magnetic properties (metal detector) to electrical capacitance (capacitive sensor array). By measuring capacitance changes rather than magnetic field interactions, the system can detect both metallic and non-metallic foreign objects, as all materials have different dielectric constants that affect capacitance readings.
2Measurement precision
If a camera or image processing method is used to visually inspect inserted checks or banknotes, then all foreign objects can be identified, but the solution becomes expensive and complicated to implement
Solution Approach 1:
The patent replaces the complex optical system (camera and image processing) with a simpler electrical measurement system (capacitive sensor array). The capacitive sensors directly measure electrical field changes caused by foreign objects, eliminating the need for complex image capture, processing, and analysis algorithms, thereby reducing system complexity while maintaining detection accuracy.
Solution Approach 2:
The patent uses inexpensive capacitive sensors instead of expensive camera systems. Capacitive sensors are simpler, cheaper components that can be implemented as arrays of basic electrical elements, reducing the overall system cost while providing sufficient detection capability for foreign object identification.
3Device complexity
If no foreign object detection system is implemented, then the system remains simple and inexpensive, but foreign objects can damage media transport components leading to service calls and early component failure
Solution Approach 1:
The patent implements foreign object detection before the media items are transported through the terminal. The capacitive sensor array scans the stack of checks or banknotes at the insertion point, identifying foreign objects in advance and preventing them from entering the media transport mechanism, thereby protecting components from damage while maintaining system reliability.
Solution Approach 2:
The patent introduces a capacitive sensor array as an intermediary detection system between the user insertion point and the media transport mechanism. This intermediary layer detects foreign objects and triggers appropriate responses (such as alerting the user or rejecting the stack) before the media items can cause damage to internal components, thereby maintaining both simplicity and reliability.
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
Effectively identifies all types of foreign objects, reducing service calls and preventing early component failure by providing a cost-effective and straightforward detection method.
Implementation Method 1
A capacitive sensor array is used to detect foreign objects in a stack of media items
Data Source
AI summary
A system and method for identifying a foreign object in a stack of media items is disclosed. An upper clamping plate and an opposing lower clamping plate are positioned to hold a received stack of media items. Each clamping plate has an array of capacitive electrodes positioned on an inner surface thereof. Each of the capacitive electrodes in the one array positioned directly across from a corresponding one in the first array to form a capacitive electrode pair. A controller measures the capacitance of each capacitive electrode pair when the received stack of media items is positioned between the clamping plates, determine if a foreign object is present within the received stack of media items based on the capacitance measurements from each capacitive electrode pair, and generate a signal indicating that a foreign object has been detected when a foreign object is determined to be present.