Visible Light Receiver Using Blue Light Extraction for High Speed
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Solution Overview
Problem
Visible light communication systems using blue light-excited white LEDs face challenges in achieving high transmission speed and long communication distance due to ambient light noise and low response speed of fluorescent materials.
Innovation Solution
A visible light communication system with a receiver that includes a receiving unit for blue light-excited white LEDs driven by a current signal with rising and falling pulses, a photoelectric converter, an equalizer for duobinary signal equalization, a discriminator for 3-value signal generation, a maximum-likelihood decoder, and a decoder for RLL decoding, which improves transmission speed and communication distance using a simple processing circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a blue light-excited white LED with fluorescent material is used for visible light communication, then the system can achieve generic light source compatibility and reasonable transmission speed, but the response speed of the fluorescent material limits the transmission speed to only several Mbps
Solution Approach 1:
The patent segments the white light into blue light and yellow light components using a beam splitter. The blue light component (from the blue LED) is used for high-speed data transmission, while the yellow light component (from the fluorescent material) is separated and can be used for other purposes or discarded. This segmentation allows the system to overcome the slow response of the fluorescent material by utilizing only the fast-response blue light for communication.
Solution Approach 2:
The patent extracts the blue light component from the white light emitted by the blue light-excited white LED using a bandpass filter or beam splitter. By taking out only the blue light portion, the system eliminates the limiting factor (slow fluorescent response) while retaining the advantage of using a generic white LED structure. The extracted blue light signal carries the modulated data at high speeds.
2Adaptability or versatility
If ambient light is present in the communication environment, then the system can operate in practical applications, but the ambient light acts as noise and degrades transmission quality
Solution Approach 1:
The patent converts the harmful effect of ambient light noise into a beneficial filtering mechanism. By using a bandpass filter tuned to the blue light wavelength, the system not only extracts the signal but also rejects out-of-band ambient light. The filter transforms the broadband ambient light (harmful noise) into a narrowband rejected signal, allowing only the desired blue light communication signal to pass through.
Solution Approach 2:
The patent employs a feedback mechanism where the received signal is monitored and processed to optimize communication performance. The system adjusts transmission parameters based on detected signal quality, compensating for ambient light interference dynamically. This feedback loop maintains reliable transmission despite varying ambient light conditions.
3Speed
If a color filter is added to transmit only blue light at the receiver side, then the transmission speed can be improved to tens of Mbps, but the device complexity increases
Solution Approach 1:
The patent makes the beam splitter or bandpass filter serve multiple functions: it simultaneously separates the blue light from the white light, filters out ambient light noise, and enables high-speed transmission. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving the desired speed improvement.
4Length of stationary object
If the communication distance is increased, then the system can cover larger areas, but the ambient light noise accumulates and degrades the signal quality
Solution Approach 1:
The patent introduces an intermediary filtering mechanism (bandpass filter or beam splitter) between the receiver and the ambient environment. This intermediary selectively transmits the blue light communication signal while blocking ambient light wavelengths. By placing this intermediary in the optical path, the system can extend communication distance without proportionally increasing the impact of ambient light noise, as the filter continuously rejects out-of-band interference regardless of distance.
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
The system achieves high transmission speed and increased communication distance while effectively suppressing ambient light noise, enabling efficient data transmission with a simplified circuit configuration.
Implementation Method 1
a photoelectric converter configured to convert the visible light signal received by the receiving unit into an electrical signal
Implementation Method 2
the fluorescent material disposed around the blue LED is excited by blue light emitted from the blue LED, and yellow light outputted from the fluorescent material is mixed with blue light emitted from the blue LED
Data Source
AI summary
A visible light communication receiver increases a communication distance from a transmitter to a receiver while realizing high transmission speed. The visible light communication receiver includes a receiving unit that receives a visible light signal from a blue light-excited white LED driven by a driving current signal generated by adding rising and falling pulses to respective rising and falling edges of a transmission data encoded according to a DC-free RLL code having a minimum run of 1 and NRZI-modulated prior to adding the rising and falling pulses; a photoelectric converter that converts the visible light signal into an electrical signal; an equalizer that equalizes the electrical signal to a duobinary signal; a discriminator that discriminates the duobinary signal to generate a 3-value signal; a maximum-likelihood decoder that ML-decodes the 3-value signal to output a decoded signal; and a decoder that RLL decodes the decoded signal.