Visible Light Demodulation via Pixel Amplifier Sequential Output
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Solution Overview
Problem
Conventional visible light communication systems face challenges in precisely extracting data due to overexposure and noise in images captured by digital cameras, limiting transmission speed and accuracy.
Innovation Solution
A visible light receiving method using a pixel amplifier sequential output type imaging element, which calculates differential values from exposure amounts of light and dark bands to demodulate signals, allowing for high-speed data reception without being limited by camera shutter speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a digital camera directly photographs a luminous visible light irradiated from the light source for illumination, then the exposure of the camera is automatically adjusted for the entire viewing surface, but the image of the light source goes blank and is photographed in an overexposed state, making it extremely difficult to precisely extract visible light transmission data
Solution Approach 1:
The patent applies local quality by differentiating between the light source region and non-light source regions in the image. The light source pixels are identified and separately processed to extract transmission data, while other regions maintain normal exposure processing. This allows the system to handle the overexposed light source area differently from the rest of the image, preserving data extractability from the light source without compromising overall image quality.
2Productivity
If the camera shutter speed is increased to capture faster transmission signals, then the transmission speed can be improved, but the camera's inherent shutter speed limitation prevents high-speed demodulation
Solution Approach 1:
The patent replaces the mechanical shutter mechanism with an electronic processing approach. Instead of using the camera's physical shutter to control exposure time for capturing fast signals, the system uses electronic image processing to extract transmission data from the captured image. This substitution allows demodulation speeds to exceed the camera's mechanical shutter speed limitations.
Solution Approach 2:
The patent transitions from time-based signal capture (limited by shutter speed) to spatial-based signal extraction. By encoding transmission information in the spatial distribution of light across the image sensor and extracting it through image processing, the system bypasses the temporal limitation imposed by the camera's shutter speed, achieving higher effective transmission speeds.
3Illumination intensity
If the LED is continuously lit during a period of digital value '0' to secure necessary illuminance, then illumination is maintained, but the LED cannot blink at high frequency to transmit high-speed data
Solution Approach 1:
The patent employs periodic action by modulating the LED at a high-frequency carrier wave (e.g., several MHz). The LED rapidly switches on and off at this carrier frequency, creating a blinking pattern that encodes data. Simultaneously, the duty cycle is adjusted to maintain adequate average illuminance. This periodic modulation allows high-speed data transmission while preserving illumination requirements.
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 stable and high-speed demodulation of visible light transmission signals, overcoming the limitations of conventional methods by precisely extracting pulse information from differential exposure values, thereby increasing transmission speed and accuracy.
Implementation Method 1
a pixel amplifier sequential output type imaging element, which accumulates electric charges in pixels in a row at an exposure time for each row of pixels
Data Source
AI summary
A visible light transmitting signal is modulated on the basis of an information signal to be transmitted, and is superimposed on a visible light to be transmitted. A camera (10) photographs the transmitted visible light by use of a pixel amplifier sequential output type imaging element (11), and the pixel amplifier sequential output type imaging element (11) amplifies electric charges generated in respective pixels by respective pixel amplifiers (22), to output imaging signals in sequence from the respective pixel amplifiers (22). Image data of light and dark bands acquired from the imaging signals are taken in by frame, and a differential value is calculated for displacement of exposure amounts of the respective pixels output in sequence or the respective rows. The transmitted information signal is demodulated on the basis of the differential value of the imaging signals of a plurality of samples serving respective pixels or respective rows as one sample in one frame.