Ensemble ALPR Decision Tree for Low-Quality Plate Recognition

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Solution Overview

Problem

Existing ALPR systems face challenges in achieving high accuracy for license plate recognition due to variations in lighting conditions and plate quality, leading to suboptimal performance in surveillance and law enforcement applications.

Innovation Solution

An ensemble ALPR method combining multiple engines, including a template-based solution and OCR, using a decision tree to integrate their outputs, with image encoding by shallow neural networks to determine the nearest match.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single ALPR engine is used, then the system complexity is low, but the recognition accuracy is insufficient due to variations in lighting conditions and plate quality

Engineering Contradiction:
Improvelicense plate recognition accuracyVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines multiple ALPR engines (including template-based and OCR engines) into an ensemble system that processes license plate images through several different recognition methods simultaneously. The outputs of these engines are then integrated to produce a final recognition result, thereby improving accuracy while managing system complexity through structured integration.

Inventive Principle:
Principle #5Merging (Combining)

2Measurement precision

If multiple ALPR engines are used to improve accuracy, then the recognition precision improves, but the computational resources and processing time increase

Engineering Contradiction:
Improvelicense plate recognition accuracyVSAvoidcomputational resources
Core Design Contradiction:
Measurement precisionVSPower

Solution Approach 1:

The patent implements a voting mechanism where multiple ALPR engines process the image, but only a subset of engines needs to agree on a result for it to be accepted. This partial action approach allows the system to benefit from multiple recognition methods while avoiding the full computational cost of all engines processing every single image, thus reducing overall computational resource requirements.

Inventive Principle:
Principle #16Partial or excessive action

3Measurement precision

If an ensemble method with multiple engines is deployed, then the recognition accuracy improves by nearly 4%, but the device complexity increases

Engineering Contradiction:
Improvelicense plate recognition accuracyVSAvoidensemble system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the ALPR system into distinct functional modules: template-based recognition engine, OCR engine, image preprocessing module, and a voting/decision mechanism. Each module operates independently with well-defined interfaces, allowing the complex ensemble system to be managed through modular design where each component can be developed, tested, and maintained separately.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentUS12482277B2System and method for reading license plate from an image using an ensemble method of ALPR systems
Publication Date: 2025.11.25 CONDUENT BUSINESS SERVICES LLC
  • US12482277B2 patent drawing
  • US12482277B2 patent drawing
  • US12482277B2 patent drawing

AI summary

Methods and systems of license plate recognition can involve subjecting an image captured by an image capturing device to image-processing by a group of different license plate recognition engines including a license plate recognition engine and a license plate reidentification engine, and using a decision tree to combine data from the license plate recognition engine and the license plate reidentification engine and generate a license plate identifier based on the data processed by the decision tree.