Capacitance Detection Device for Sheet Authentication
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Solution Overview
Problem
Conventional capacitance detection devices for authenticating sheet-like objects, such as bank bills and securities, face challenges in miniaturization and simplification due to complex structures and limited compatibility with other sensors, hindering their integration into compact and efficient systems.
Innovation Solution
A capacitance detection device with a first electrode and a second electrode arranged on either side of a conveyance path, forming an electric field and using an oscillating circuit to detect changes in capacitance, integrated with an image reading device to enable size reduction and simplify the configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compression-type roller and ultrasonic sensor are used for paper thickness detection, then foreign matter detection capability is improved, but device size and cost increase
Solution Approach 1:
The patent extracts the capacitance detection function from a separate complex thickness detection device and integrates it directly into the image reading device. By using a capacitance sensor that detects changes in capacitance between electrodes as the detection object passes through, the system achieves foreign matter detection without requiring separate compression rollers or ultrasonic sensors, thereby reducing overall device size while maintaining detection capability
Solution Approach 2:
The patent merges the capacitance detection device with the image reading device into a single integrated system. The capacitance sensor is positioned to detect the detection object simultaneously with or near the image reading position, combining authentication and imaging functions in one device, which reduces the number of separate components and overall system size
2Measurement precision
If a three-dimensional capacitance detection electrode shape is used, then detection precision is improved, but device complexity and miniaturization difficulty increase
Solution Approach 1:
The patent transitions from three-dimensional electrode structures to two-dimensional planar electrode arrangements. The first and second electrodes are arranged in overlapping regions viewed from the direction perpendicular to their surfaces, creating an electric field that effectively detects capacitance changes without requiring complex 3D shaping. This dimensional simplification maintains detection precision while enabling easier miniaturization and integration
Solution Approach 2:
The patent divides the capacitance detection system into separate first and second electrodes positioned on opposite sides of the conveyance path, with each electrode having a simplified planar structure. The detection function is segmented across these two simpler electrodes rather than requiring a single complex three-dimensional electrode, reducing manufacturing complexity while maintaining detection accuracy
3Volume of stationary object
If capacitance sensor and image reader are integrated, then device size is reduced, but compatibility and detection accuracy may be compromised
Solution Approach 1:
The patent segments the integrated device into distinct functional modules: the capacitance detection device with its oscillating circuit and detection circuit on separate circuit boards, and the image reading device with its light source and light-receiving element. This modular segmentation within integration allows each component to operate independently with optimized performance while maintaining compact overall device size
Solution Approach 2:
The patent creates a multi-functional integrated device that performs both capacitance-based authentication and optical image reading. The system is designed to handle multiple detection objectives simultaneously - detecting foreign matter through capacitance changes and capturing image information through optical means - thereby enhancing versatility and adaptability while maintaining a compact integrated form factor
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 allows for precise detection of foreign matter on sheet-like objects while reducing the device's size and complexity, enhancing compatibility with other sensors and improving the detection of image information.
Implementation Method 1
an oscillating circuit that forms an electric field between the first electrode and the second electrode
Implementation Method 2
a detection circuit that detects a change in capacitance between the first electrode and the second electrode
Data Source
AI summary
A capacitance detection device includes a first electrode (1) and a second electrode (2) at least partially facing each other with a conveyance path (5) therebetween, the conveyance path extending along a conveyance direction in which a sheet-like detection object (3) is conveyed, an oscillating circuit to form an electric field (9) between the first electrode (1) and the second electrode (2), a detection circuit to detect a change in capacitance between the first electrode (1) and the second electrode (2), a first board (11) and a second board (12) including at least one of the oscillating circuit or the detection circuit, an insulative first plate (6) arranged between the first electrode (1) and the conveyance path (5), and an insulative second plate (7) arranged between the second electrode (2) and the conveyance path (5).