Multi-feed Detection Apparatus with Dynamic Threshold Adjustment
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Solution Overview
Problem
Existing multi-feed detection systems, particularly in scanners, face challenges in accurately distinguishing between plastic cards and multi-feed conditions of paper due to similar ultrasonic wave reception levels, leading to potential mistaken determinations.
Innovation Solution
A multi-feed detection apparatus that includes a conveyance roller, an ultrasonic sensor, an imaging device, and a processor to generate line images, detect medium width and vertex count, estimate medium shape, and adjust or stop multi-feed detection based on the shape, thereby differentiating between card and paper conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic wave reception level is used for multi-feed detection, then multi-feed detection capability is improved, but false detection occurs when plastic cards are conveyed
Solution Approach 1:
The detection process is segmented into multiple stages: first using ultrasonic sensors for initial multi-feed detection, then using imaging devices to capture and analyze medium shapes. This segmentation allows the system to use different detection methods for different aspects, reducing false detections while maintaining detection capability.
Solution Approach 2:
An imaging device acts as an intermediary between the ultrasonic detection and the final determination. The imaging device captures visual information about the medium's shape, which serves as additional evidence to confirm or refute ultrasonic detection results, thereby reducing false positives when plastic cards are conveyed.
2Device complexity
If a fixed threshold value is used for multi-feed detection, then detection simplicity is improved, but detection accuracy deteriorates when different medium types are conveyed
Solution Approach 1:
The threshold value is made dynamic rather than fixed. The system adjusts the threshold based on the detected medium shape characteristics. For example, when a plastic card shape is detected, the system knows that ultrasonic reception levels will be higher, so it adjusts the threshold accordingly to prevent false multi-feed detection, while maintaining simple detection logic.
3Measurement precision
If multiple detection methods are combined, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The imaging device serves multiple functions: it captures medium shape information for threshold adjustment, provides visual confirmation for multi-feed detection, and can identify medium types. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while still achieving improved detection accuracy.
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 system effectively prevents false multi-feed detections by accurately identifying card shapes and adjusting detection thresholds, enhancing the accuracy of medium conveyance and reducing user intervention.
Implementation Method 1
an ultrasonic transmitter for transmitting an ultrasonic wave and an ultrasonic receiver for receiving the ultrasonic wave through the medium
Data Source
AI summary
A multi-feed detection apparatus includes a conveyance roller, an ultrasonic sensor for generating an ultrasonic signal, an imaging device to image the medium being conveyed by the conveyance roller and sequentially generate a line image, and a processor to detect a width of the medium in each line image for each line image, detect a vertex count of a medium included in the sequentially generated line image based on the width of the media in the each line image, detect a length of the medium in a direction perpendicular to the medium width, estimate a shape of a medium based on the vertex count and the length of the medium, and detecting media multi-feed by comparing the ultrasonic signal with a predetermined threshold value, and change the predetermined threshold value or stop detection of the medium multi-feed, based on the estimated shape of the medium.