Frequency-Modulated Distance Measurement Device Beat Signal Noise Reduction
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Solution Overview
Problem
Existing distance measurement technologies using light waves face challenges in accurately determining object distance due to noise interference, particularly amplitude noise, when phase differences are detected based on amplitude modulation.
Innovation Solution
A distance measurement device that generates transmission light by modulating the frequency of an optical carrier wave, interferes it with reference light to create beat signals, and calculates object distance based on the phase difference between these signals, thereby reducing noise interference and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplitude modulation is used for distance measurement, then phase difference detection can be performed, but amplitude noise interferes with measurement accuracy
Solution Approach 1:
The patent changes the modulation parameter from amplitude to frequency. By frequency-modulating the optical carrier wave instead of amplitude-modulating it, the system eliminates amplitude noise interference while maintaining the ability to detect phase differences for distance measurement. This parameter change transforms the measurement approach from one susceptible to amplitude noise to one that uses frequency information.
2Object-affected harmful factors
If frequency modulation is used to generate transmission light, then amplitude noise interference is reduced, but complex signal processing is required
Solution Approach 1:
The patent introduces a local oscillator as an intermediary component that generates reference light. This reference light is used to mix with the frequency-modulated transmission light and reflected light, converting the frequency modulation into measurable beat signals. The local oscillator acts as a mediator that simplifies the detection process by transforming frequency information into amplitude variations that can be easily processed.
3Measurement precision
If phase difference is detected from beat signals, then distance can be calculated, but measurement reliability is affected by noise
Solution Approach 1:
The patent replaces amplitude-based detection with frequency-based detection. By using frequency modulation and detecting phase differences in the resulting beat signals, the system substitutes the amplitude measurement mechanism with a frequency measurement mechanism. This substitution inherently improves reliability because frequency measurements are less susceptible to noise interference compared to amplitude measurements.
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 enhances distance measurement accuracy by minimizing the impact of amplitude noise and allows for precise distance calculation using phase differences without amplitude modulation, resulting in more reliable and noise-resistant measurements.
Implementation Method 1
a modulation means for generating transmission light acquired by modulating a frequency of an optical carrier wave, based on the distance measurement signal
Implementation Method 2
a first beat signal generation means for generating a first beat signal by causing the transmission light to interfere with reference light
Implementation Method 3
a second beat signal generation means for generating a second beat signal by causing the reflected light to interfere with reference light
Data Source
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AI summary
A distance measurement device (2000) generates transmission light by modulating an optical carrier wave. The distance measurement device (2000) transmits the generated transmission light, and receives reflected light acquired by the transmission light being reflected by a measured object 10. The distance measurement device (2000) generates a first beat signal by causing the transmission light to interfere with reference light. The distance measurement device (2000) generates a second beat signal by causing the reflected light to interfere with the reference light. The distance measurement device (2000) calculates a distance to the measured object (10), based on a difference between the first beat signal and the second beat signal.