Compensation Filter for Coded Light Distortion
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Solution Overview
Problem
The existing coded light systems face distortion issues due to inter-symbol interference and modulation disturbances in the feedback loop, which affect the stability of the illumination level and the accuracy of data symbols in coded light signals.
Innovation Solution
A compensation filter is introduced to adaptively correct for distortion by measuring the current measurement feedback for each symbol, using an adaptive filter to determine and apply compensation based on the history of preceding symbols, thereby mitigating inter-symbol interference and maintaining a constant illumination level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If data symbols are modulated into the current through the illumination source, then data transmission is enabled, but distortion and inter-symbol interference occur in the current measurement feedback
Solution Approach 1:
The patent separates the current control function from the data modulation function by introducing a compensation filter that specifically targets and removes distortion caused by data symbols in the feedback path, allowing both functions to operate independently without interfering with each other
Solution Approach 2:
The compensation filter acts as an intermediary element in the feedback path that mediates between the distorted current measurement and the controller, selectively removing distortion components while preserving the actual current information needed for control
2Stability of the object's composition
If a feedback loop is used to maintain constant illumination level, then illumination stability is improved, but modulation disturbances affect the feedback measurement and cause symbol distortion
Solution Approach 1:
The compensation filter applies selective processing to different frequency components of the feedback signal, targeting only the specific distortion frequencies caused by data modulation while leaving the fundamental illumination control signals unaffected
Solution Approach 2:
The patent uses the existing feedback loop structure and enhances it by adding compensation based on the known data symbol sequence, creating a dual feedback mechanism that simultaneously maintains illumination stability and corrects symbol distortion
3Speed
If the line rate is high enough relative to modulation frequency in a rolling shutter camera, then different lines capture different phases of modulation waveform, but this requires high synchronization precision
Solution Approach 1:
The transmitter embeds synchronization information within the data symbol sequence itself, allowing the receiver to预先 determine the timing and phase relationships without requiring external synchronization signals or complex calibration procedures
Data Source
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AI summary
Current through an illumination source is controlled by means of a feedback loop whereby the current is measured and fed back to a current controller, which compares this to a set-point and based thereon outputs a current control signal which controls downstream power circuitry driving the current through the illumination source. This keeps the illumination at a steady dim level. Data is also coded into the illumination by modulating the current control signal, i.e. at the output of the current controller, but prior to the input to the power circuitry. The present disclosure provides a compensation filter arranged to apply a compensation to the error signal, to at least partially remove an effect of a distortion of the current measurement caused by the modulation of the data symbols into the illumination source current.