Traffic Light Detection via AC Phase Synchronization
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Solution Overview
Problem
Existing traffic light detection systems struggle to accurately detect distant traffic lights due to insufficient image size, which makes it difficult to determine circularity and thus fails to detect small traffic lights effectively.
Innovation Solution
A traffic light detecting device that captures images in the vehicle's travel direction and uses a reference signal generating unit to set multiple phase-shifted reference signals synchronized with the alternating current power cycle, allowing for phase adjustment to detect synchronized pixels with varying luminance, enabling accurate detection of traffic lights regardless of size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If circularity-based detection is used to identify signal lamps, then detection accuracy for nearby traffic lights is improved, but detection capability for distant traffic lights deteriorates due to insufficient image size
Solution Approach 1:
The invention changes the detection parameter from geometric circularity to temporal luminance variation. By monitoring how luminance changes over time in sync with the AC power cycle, the system can detect traffic lights at any distance without requiring a minimum image size, thus resolving the contradiction between detection accuracy and image size requirements
Solution Approach 2:
The invention utilizes the periodic nature of AC power supply (50/60Hz) to create periodic reference signals. By comparing luminance variations with these periodic reference signals, the system can identify traffic lights through their characteristic flicker pattern, enabling detection regardless of distance or image size
2Reliability
If multiple phase-shifted reference signals are used to synchronize with AC power cycle, then detection sensitivity for distant traffic lights is improved, but device complexity increases
Solution Approach 1:
The invention segments the AC power cycle into multiple phase-shifted reference signals (typically three signals shifted by 120 degrees). This segmentation allows the system to capture luminance variations at different phases of the AC cycle, improving detection sensitivity while keeping each individual reference signal simple
Solution Approach 2:
The multiple phase-shifted reference signals serve multiple functions: they can detect traffic lights at any phase of the AC cycle, provide redundancy for more reliable detection, and work together to identify the correct phase through correlation analysis. This multi-functionality improves reliability without requiring complex individual components
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 method allows for high-accuracy detection of distant traffic lights by extracting synchronized pixels with luminance variations matching the alternating current power cycle, excluding other electric lights and improving detection sensitivity even when image size is too small for circularity determination.
Implementation Method 1
The traffic light detecting unit extracts from the image a synchronized pixel with a luminance which varies in synchronization with the reference signal having the phase adjusted to the phase of the alternating current power
Data Source
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AI summary
A traffic light detecting device includes an image capturing unit (11) configured to capture an image in the travelling direction of a vehicle, and a traffic light detecting unit (12) configured to detect a traffic light from the image. The traffic light detecting unit (12) sets reference signals (L01 to L03) the number of which is a multiple of three, and phases of which are shifted each other by a time obtained by dividing a cycle of an alternating current power supplied to the traffic light by the multiple of three, and adjusts a phase of the reference signal (L01) which is closest to the phase of the alternating current power, to the phase of the alternating current power. The traffic light detecting unit (12) extracts from the image a synchronized pixel (53b) with a luminance which varies in synchronization with the reference signal (L01) having the phase adjusted to the phase of the alternating current power, and judges that a traffic light is present at a position of the synchronized pixel.