Distance Measuring Device Oscillator Fluctuation Compensation
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Solution Overview
Problem
Existing distance measuring devices using optical frequency combs face challenges in accurately measuring distance when fluctuations occur in the frequency of the oscillator, leading to variations in the frequencies of the processed signals, making it difficult to extract phase differences.
Innovation Solution
The device employs a local oscillator method to extract and beat down frequencies from an optical frequency comb, using a series of filters and mixers to generate and select difference frequency components that remain stable despite oscillator frequency fluctuations, allowing for stable measurement of phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the oscillator frequency is used to beat down the frequency of periodic signals, then the frequency components can be reduced to low frequency for measurement, but the oscillator frequency fluctuations cause large variations in the beaten down signal frequency
Solution Approach 1:
The patent introduces a frequency control unit that acts as an intermediary between the oscillator and the mixing process. This unit receives the oscillator output and generates a controlled frequency signal that is used to beat down the periodic signals. By mediating the frequency conversion process, the system can reduce the impact of oscillator fluctuations on the final measurement signal.
Solution Approach 2:
The patent implements a feedback mechanism where the frequency control unit monitors the oscillator output and adjusts the beaten down frequency accordingly. When oscillator frequency fluctuations occur, the feedback system detects these changes and compensates by adjusting the local oscillator frequency to maintain stable output frequency from the mixers, ensuring reliable phase difference measurements.
2Measurement precision
If high accuracy oscillator is used to reduce frequency fluctuations, then phase difference measurement becomes feasible, but the device complexity and cost increase
Solution Approach 1:
The patent changes the operating parameters of the frequency conversion process. Instead of relying on a single high-accuracy oscillator, the system uses a frequency control unit that dynamically adjusts the oscillator frequency and the beating process parameters. This allows the system to achieve accurate phase difference measurement by controlling the frequency conversion process rather than relying solely on oscillator stability.
Solution Approach 2:
The patent segments the frequency conversion function into multiple stages: the oscillator generates the base frequency, the frequency control unit processes and controls the frequency, and the mixers perform the actual beating down. This segmentation allows each component to operate at optimized performance levels, reducing the need for extremely high oscillator accuracy while maintaining measurement precision.
3Adaptability or versatility
If the oscillator frequency fluctuates by ±100 ppm, then the frequency variation reaches ±4 MHz, but using a filter to extract specific frequency becomes difficult
Solution Approach 1:
The patent introduces dynamic control of the frequency conversion process through the frequency control unit. Instead of using a static filter approach that requires precise frequency knowledge, the system dynamically adjusts the local oscillator frequency to track and compensate for oscillator fluctuations. This dynamic approach makes the frequency extraction process adaptive to varying conditions, reducing the difficulty of extracting specific frequency components even when oscillation frequency varies by ±100 ppm.
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 approach enables accurate distance measurement from phase differences between processed signals even when the oscillator frequency fluctuates, ensuring consistent frequency components and stable phase difference measurement.
Implementation Method 1
The first mixer 31 generates sum and difference frequency components of the beat signal from the measuring light receiving unit 6 and the periodic signal oscillated by the oscillator 50
Implementation Method 2
The fourth filter 51 extracts a beat signal having the difference frequency component from the frequency components generated by the first mixer 31
Implementation Method 3
the phase difference measuring unit 12 measures a phase difference of two beat signals extracted by the sixth filter 54 and the second filter 11
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A distance measuring device measures a distance from a phase difference of beaten down processing signals even when fluctuations occur in a frequency of an oscillator. The distance measuring device includes a laser unit 1 for generating an optical frequency comb as a laser light flux, a reference light receiving unit 3 for receiving reference light 27, and a measuring light receiving unit for receiving distance measuring light 28. A first mixer 31 and a second mixer 32 multiply received light signals of the measuring light receiving unit 6 and the reference light receiving unit 3 by a periodic signal of the oscillator 50. The periodic signal has a specific frequency. A fourth filter 51 and a fifth filter 52 extract frequency components which are different, from signal components generated by the first mixer 31 and the second mixer 32. The signals extracted by the fourth filter 51 and the fifth filter 52 are multiplied with each other by a third mixer. A difference frequency component is extracted by a sixth filter 54. A phase difference measuring unit 12 measures a phase difference of two processing signals from the sixth filter 54 and the second filter 11. A distance measuring unit 17 measures a distance based on the phase difference.