Self-Mixing Interference Distance Measurement via Peak Width Analysis
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Solution Overview
Problem
Existing distance measurement technologies using self-mixing interference (SMI) require advanced electronics for modulating the laser current, increasing technical efforts and potentially leading to inaccuracies due to modulation scheme distortions.
Innovation Solution
An apparatus and method that determine distance based on the peak width of the SMI signal, eliminating the need for laser current modulation by using a peak width determination unit and normalization to improve accuracy and reduce technical efforts, with optional features like feedback independent regime detection and adjustable focusing settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser current modulation is used for distance measurement, then distance determination is possible, but device complexity and technical efforts increase
Solution Approach 1:
The patent extracts the distance measurement capability from the complex current modulation system and implements it through a simplified peak width analysis method. By removing the modulation electronics and using only the natural peak width variation of the SMI signal, the system achieves distance measurement without advanced electronics.
Solution Approach 2:
The patent replaces the electronic modulation system with an optical-based measurement approach. Instead of using electrical current modulation to encode distance information, the system uses the optical interference pattern's peak width, which naturally varies with distance, thereby substituting electronic complexity with optical analysis.
2Measurement precision
If laser current modulation is used for distance measurement, then distance information can be obtained, but measurement accuracy deteriorates due to modulation distortions
Solution Approach 1:
The patent converts the natural variation in peak width, which would be a secondary characteristic in traditional methods, into the primary measurement parameter. By utilizing this previously overlooked feature, the system eliminates the need for modulation and its associated distortion problems, thereby improving measurement reliability.
Solution Approach 2:
The patent changes the measurement parameter from phase shift (which requires modulation) to peak width (which is naturally varying). This parameter change allows distance measurement to be performed using the inherent properties of the SMI signal without external modulation, thus avoiding modulation-induced inaccuracies.
3Device complexity
If peak width analysis is used for distance measurement, then device complexity is reduced, but measurement accuracy may be affected by frequency dependence
Solution Approach 1:
The patent applies preliminary normalization to the SMI signal before peak width analysis. By normalizing the frequency dependence in advance, the system removes potential sources of error that would otherwise affect measurement accuracy. This preliminary processing step ensures that the peak width directly reflects distance variations without being confounded by frequency effects.
Solution Approach 2:
The patent incorporates a feedback mechanism where the measured peak width is compared against reference values or calibration data. This feedback loop allows the system to compensate for any remaining frequency-dependent variations and to accurately translate peak width measurements into distance values, thereby maintaining high measurement precision.
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 reduces the complexity and cost of distance measurement electronics while enhancing accuracy by relying on peak width analysis and normalization, allowing for simpler and more precise distance determination without requiring advanced current modulation techniques.
Implementation Method 1
an SMI unit for generating an SMI signal, wherein the SMI unit comprises a laser emitting a first laser beam for being directed to an object and wherein the SMI signal depends on an interference of the first laser beam and a second laser beam reflected by the object
Data Source
AI summary
An apparatus, method and computer program for measuring a distance using a self-mixing interference (SMI) unit that generates an SMI signal. The SMI unit comprises a laser emitting a first laser beam directed to an object and wherein the SMI signal depends on an interference of the first laser beam and a second laser beam reflected by the object. A peak width determination unit determines a peak width of the SMI signal, and a distance determination unit determines a distance between the object and the SMI unit depending on the determined peak width of the SMI signal. Since the distance is determined depending on the peak width of the SMI signal, without requiring a laser driving current modulation, advanced electronics for modulating the driving current of the laser are not needed. This reduces the technical efforts needed for determining the distance.