Traffic Light Detection Using Monochrome Conversion and Blob Analysis

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Solution Overview

Problem

Existing traffic light detection methods based on color are unreliable, particularly for green traffic lights, due to interference from ambient light, and lack robustness in distinguishing red traffic lights.

Innovation Solution

A method and system that convert color images into monochrome scale images, apply binary conversion using brightness or channel values, and utilize geometric parameters and classifiers to identify candidate blobs, with specific thresholding and morphology operations to enhance detection accuracy for both green and red traffic lights.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If color-based detection is used for green traffic lights, then the detection process is simple, but the detection reliability deteriorates due to ambient light interference

Engineering Contradiction:
Improvedetection process complexityVSAvoidgreen traffic light detection reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The detection process is segmented into multiple stages: initial color-based candidate identification, followed by monochrome scale conversion, binary image processing, blob analysis with geometric parameters, and final classification. This segmentation allows the system to maintain simplicity in candidate selection while adding robustness through subsequent processing stages.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

A monochrome scale image is introduced as an intermediary between the color image and final detection. This intermediary representation converts color information to intensity information, making the detection process less sensitive to ambient light color variations while preserving the structural information needed for reliable detection.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Device complexity

If color-based detection is used for red traffic lights, then the detection process is simple, but the detection robustness deteriorates

Engineering Contradiction:
Improvedetection process complexityVSAvoidred traffic light detection robustness
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The system changes the parameter space from color-based detection to intensity-based detection in the monochrome scale. For red traffic lights, this transformation allows the use of geometric parameters and binary image analysis that are more robust to environmental variations while maintaining detection accuracy.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The system performs preliminary conversion to monochrome scale image and binary image processing before final classification. This preliminary action prepares the data in a form that is more suitable for robust detection, filtering out noise and irrelevant information before the final decision is made.

Inventive Principle:
Principle #10Preliminary action

3Reliability

If multiple processing steps are added to improve detection accuracy, then detection reliability improves, but processing time increases

Engineering Contradiction:
Improvetraffic light detection accuracyVSAvoidimage processing time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The system applies processing steps selectively: all images undergo color-to-monochrome conversion and binary processing, but blob analysis and classification are applied only to candidate regions identified in earlier stages. This partial action approach maintains high accuracy while reducing overall processing time by avoiding exhaustive analysis of all image regions.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentUS9811746B2Method and system for detecting traffic lights
Publication Date: 2017.11.07 HARMAN INT IND INC
  • US9811746B2 patent drawing
  • US9811746B2 patent drawing
  • US9811746B2 patent drawing

AI summary

A method for detecting traffic lights is provided. The method includes: obtaining a color image captured by a camera; converting the color image into a first monochrome scale image; converting the first monochrome scale image into a first binary image; identifying a first set of candidate blobs in the first binary image based on at least one predetermined geometric parameter; and determine whether a first region in the color image, which first region corresponds to one of the first set of candidate blobs, is a green traffic light using a green traffic light classifier. The accuracy and efficiency may be improved.