Camera Shutter Timing for High-Frequency Visible Light Data Detection
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Solution Overview
Problem
Conventional cameras with frame rates of 50 to 100 Hz are inadequate for detecting data embedded in light sources using high frequency modulation, as they require low modulation frequencies or noticeable variations in light output to function effectively, limiting the ability to retrieve data from multiple positions simultaneously in a scene.
Innovation Solution
A detection system utilizing a conventional camera and processing unit that captures a series of images with varying exposure instances within the frame time, allowing the determination of a repeating sequence of symbols embedded in the light output of a light source, enabling the use of cameras with lower frame rates to detect high-frequency modulated data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional cameras with frame rates of 50 to 100 Hz are used to detect data embedded in light sources, then the camera can operate at lower frame rates, but the modulation frequency must be reduced to match the camera's frame rate, making the light output variations noticeable to consumers
Solution Approach 1:
The camera frame time is segmented into multiple exposure instances, where each exposure instance captures light intensity during a specific time period corresponding to different symbol periods of the modulated signal. This allows the camera to effectively sample high-frequency modulated signals even though the overall frame rate is low, resolving the contradiction between low frame rate operation and high modulation frequency detection
Solution Approach 2:
The detection system uses periodic exposure instances within each frame time, where the exposure instances are repeated across multiple frames. This periodic sampling approach allows synchronization with the high-frequency modulated signal, enabling detection of high modulation frequencies while maintaining low overall frame rates and avoiding noticeable light variations
2Speed
If high frequency modulation is used to embed data in light output, then data can be detected without noticeable variations, but conventional cameras with low frame rates cannot capture the high frequency signals
Solution Approach 1:
The system dynamically adjusts the timing and duration of exposure instances within each frame to match the symbol period of the modulated signal. This dynamic synchronization allows the camera to accurately capture high-frequency modulated data even with low frame rates, resolving the contradiction between high modulation frequency and detection accuracy
Solution Approach 2:
The detection system preliminarily determines the symbol period and modulation characteristics before performing data detection. This preliminary characterization enables the system to configure exposure instances optimally for detecting high-frequency signals, ensuring accurate data retrieval despite the camera's low frame rate
3Measurement precision
If a single optical receiver points to a particular lamp, then data from that specific position can be detected, but data from multiple positions within a scene cannot be retrieved simultaneously
Solution Approach 1:
The camera-based detection system can simultaneously detect data from multiple light sources across different positions within a scene by capturing spatially resolved light intensity information in each image. This multi-functional capability allows a single detection device to perform both position-specific detection and multi-position simultaneous detection, resolving the contradiction between detection specificity and versatility
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
Enables the detection of data embedded in light sources using high-frequency modulation with conventional cameras, allowing for simultaneous data retrieval from multiple positions within a scene without noticeable variations in light output, thereby overcoming the limitations of existing techniques.
Implementation Method 1
Each pixel represents an intensity of a total light output of the illumination system at a different physical position within the scene
Data Source
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AI summary
The invention relates to a detection system for determining data embedded into the light output of a light source in a form of a repeating sequence of N symbols. The detection system includes a camera and a processing unit. The camera is configured to acquire a series of images of the scene via specific open/closure patterns of the shutter. The processing unit is configured to process the acquired series of images to determine the repeating sequence of N symbols. By carefully triggering when a shutter of the camera is open to capture the different symbols of the encoded light within each frame time of a camera, a conventional camera with a relatively long frame time may be employed. Therefore, the techniques presented herein are suitable for detecting the invisible "high frequency" coded light while using less expensive cameras as those used in the prior art.