Optical Sensor Threshold Adjustment for Polymer Banknote Detection
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Solution Overview
Problem
Conventional paper sheet detection devices inaccurately detect polymer banknotes due to high light transmission through transparent regions, leading to erroneous determinations of their presence or absence, and this issue extends to other paper sheets with varying light transmission and reflection states.
Innovation Solution
A paper sheet detection device with an optical sensor system that includes a light-emitting and light-receiving portion, a storage for threshold values, an estimating module to determine the presence based on light levels, and a light amount adjustment mechanism to set the light-receiving level to a target value when no sheet is present, effectively distinguishing between transparent and non-transparent regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light transmission type optical sensor is used to detect polymer banknotes, then the presence of non-transparent regions can be detected, but transparent regions cause high light transmission leading to erroneous detection results
Solution Approach 1:
The patent segments the detection process into multiple stages: initial detection using a first threshold value, intermediate evaluation using a second threshold value, and final determination. This multi-stage segmentation allows the system to handle different light transmission states (non-transparent, transparent, and intermediate regions) separately, resolving the contradiction between detecting non-transparent regions and avoiding false positives from transparent regions.
Solution Approach 2:
The patent changes the threshold parameter dynamically based on the detected light-receiving level. When the light-receiving level falls between the first and second threshold values, the system transitions from initial detection mode to a different evaluation mode, adjusting the determination criteria accordingly. This parameter change enables accurate distinction between transparent and non-transparent regions.
2Device complexity
If a single threshold value is used for detection, then the device complexity is low, but the detection precision deteriorates due to inability to distinguish transparent and non-transparent regions
Solution Approach 1:
The patent implements dynamic threshold selection where the second threshold value is determined based on the first threshold value and the target light-receiving level. The system dynamically adjusts which threshold to use depending on the detected light-receiving level range. This dynamic approach improves detection precision without requiring multiple fixed threshold systems, thus avoiding excessive complexity.
Solution Approach 2:
The patent performs preliminary detection using the first threshold value to identify potential paper sheet presence, then uses the second threshold value for intermediate evaluation before final determination. This preliminary action structure allows the system to process different detection scenarios in sequence, improving precision while maintaining manageable complexity through structured decision-making.
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 enables accurate detection of paper sheets by setting specific threshold values and adjusting light emission to correctly identify the presence or absence of polymer banknotes and other paper sheets with different light states, preventing false negatives or positives.
Implementation Method 1
a light transmission type optical sensor having a light-emitting portion that emits light and a light-receiving portion that receives light emitted from the light-emitting portion
Implementation Method 2
when a polymer banknote is present between the light-emitting portion and the light-receiving portion, the light emitted from the light-emitting portion is blocked by the non-transparent region of the polymer banknote
Implementation Method 3
a light amount adjusting portion that adjusts an amount of light emitted by the light-emitting portion so that the light-receiving level of light in the light-receiving portion becomes the target light-receiving level
Data Source
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AI summary
A paper sheet detection device includes: an optical sensor that includes a light-emitting portion that emits light, and a light-receiving portion that receives the emitted light; a storage portion that stores a first threshold value used for determining whether or not a paper sheet is present in a path of the emitted light, a target light-receiving level set as a target value of a level of the light received by the light-receiving portion in a state where the paper sheet is not present, and a second threshold value that is set to a value that is greater than the first threshold value and less than the target light-receiving level; an estimating portion that determines whether the level of the light received by the light-receiving portion is equal to or greater than the first threshold value and less than the second threshold value, and that estimates whether or not the paper sheet is present; and a light amount adjusting portion that adjusts an amount of the light emitted by the light-emitting portion so that the level of the light received by the light-receiving portion becomes the target light-receiving level in the state where the paper sheet is not present when the estimating portion estimates that the paper sheet is not present after the estimating portion determines that the level of the light received by the light-receiving portion is equal to or greater than the first threshold value and less than the second threshold value.