Coin Imaging Lighting Near-Normal and High-Angle Incidence
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Solution Overview
Problem
Existing coin processing systems face issues with high discrimination errors due to variations in coin surface reflectance caused by aging and wear, and are slow, costly, and require significant space for imaging, especially when processing bulk coins.
Innovation Solution
The use of a linear array of optical coin-imaging sensors with multiple light emitting sources providing near-normal and high-angle lighting for high-speed imaging and processing, capable of capturing multiple spectral characteristics, and allowing for real-time reconfiguration to capture both uniform and edge-enhanced images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-angle lighting is used for coin imaging, then the system structure is simple, but discrimination errors increase due to variations in coin surface reflectance
Solution Approach 1:
The lighting system is segmented into multiple independent light sources positioned at different angles (normal incidence and oblique angles). Each light source independently illuminates the coin surface from a specific direction, allowing the system to capture reflectance characteristics from multiple perspectives. This segmentation enables accurate discrimination of coin features while maintaining independent control of each lighting element.
Solution Approach 2:
Different regions of the coin surface are illuminated with different quality and intensity characteristics based on their orientation. Normal incidence lighting provides uniform illumination for overall surface features, while oblique lighting creates enhanced contrast for edge and relief features. This local quality differentiation allows the imaging system to capture both macro and micro surface characteristics simultaneously.
2Measurement precision
If high-resolution imaging systems are used to capture detailed coin surface information, then measurement precision improves, but processing speed decreases
Solution Approach 1:
The system uses periodic illumination sequences with different lighting angles and patterns to capture coin surface information. By rapidly alternating between normal and oblique lighting conditions, the system accumulates detailed surface data over multiple quick exposure cycles rather than requiring a single long exposure, thereby maintaining high processing speed while achieving precise surface characterization.
Solution Approach 2:
The system replaces mechanical scanning or physical contact measurement methods with optical field-based imaging. Multiple light sources create simultaneous multi-angle illumination that captures three-dimensional surface topography through optical reflection patterns, eliminating the need for mechanical movement or contact probes and enabling high-speed non-contact measurement.
3Productivity
If conventional imaging systems are used for bulk coin processing, then space requirements are significant, but the system can handle large volumes of coins
Solution Approach 1:
The system merges multiple lighting functions into a compact integrated imaging head that combines normal and oblique light sources in a single spatial footprint. This consolidation allows the imaging system to perform multiple measurement functions simultaneously without requiring separate imaging stations or large spatial separation between components, enabling high-volume processing in a compact configuration.
Solution Approach 2:
The system transitions from two-dimensional planar imaging to three-dimensional surface characterization by adding the angular dimension through oblique lighting. This dimensional enhancement allows the system to extract depth and topography information from reflectance patterns, increasing the information density per unit area and reducing the physical space needed for equivalent measurement capability.
4Reliability
If multiple light sources are used to capture spectral characteristics, then coin validation accuracy improves, but energy consumption increases
Solution Approach 1:
The system employs periodic activation of different light sources rather than continuous operation of all sources. Each light source is activated in sequence or in specific combinations based on the measurement requirements, allowing the system to capture comprehensive spectral and angular reflectance data while minimizing total energy consumption through duty-cycled operation.
Solution Approach 2:
The system uses the coin's own reflective properties across different angles and wavelengths to generate the measurement signals required for validation. By illuminating the coin with multiple angles and analyzing the reflected light patterns, the system extracts authentication information passively from the coin's inherent optical characteristics without requiring active emission or complex signal generation from the coin itself.
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
This solution enables faster, more accurate, and cost-effective coin processing with reduced space requirements, improving the ability to authenticate and validate coins by capturing detailed surface information and topography variations.
Implementation Method 1
The first light emitting device emits light onto a surface of a passing coin at normal or near-normal incidence
Implementation Method 2
The second light emitting device emits light onto the surface of the passing coin at high-angle incidence
Implementation Method 3
The photodetector senses light reflected off the surface of the passing coin and outputs a signal indicative of coin image information
Data Source
AI summary
Currency processing systems, coin processing machines, and methods of imaging coins are presented herein. A currency processing system is disclosed which includes a housing with an input area for receiving coins and receptacles for stowing processed coins. A disk-type coin processing unit is coupled to the coin input area and coin receptacles. The coin processing unit includes a rotatable disk for imparting motion to coins, and a sorting head adjacent the rotatable disk with shaped regions for guiding moving coins to exit channels through which the coins are discharged to the coin receptacles. A sensor arrangement mounted adjacent the rotatable disk includes one light emitting device for emitting light onto a coin surface at near-normal incidence, and another light emitting device for emitting light onto the coin surface at high-angle incidence. A photodetector senses light reflected off the coin surface and outputs a coin-image signal for processing the coin.