Fiber-Optic Probe Interferometry Without Probe Head Oscillation
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Solution Overview
Problem
Existing fiber optic distance measurement methods require a periodic oscillation of the probe head for phase modulation, complicating the design, increasing size, and limiting measurement data rate.
Innovation Solution
Operate a semiconductor light source with a periodically varying current to modulate the wavelength, using the phase position of the interference signal to determine distance without probe head movement, enabling high-resolution and high-repetition-rate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric bending arm is used to oscillate the probe head for phase modulation, then distance measurement can be achieved, but the device complexity and size increase
Solution Approach 1:
The patent replaces the mechanical piezoelectric bending arm system with an optical modulation approach. Instead of physically oscillating the probe head to modulate the optical path length, the invention modulates the wavelength of the semiconductor light source directly. This substitution eliminates the mechanical actuator and its associated complexity while achieving the same phase modulation effect needed for distance measurement.
Solution Approach 2:
The patent changes the wavelength parameter of the semiconductor light source periodically to achieve phase modulation of the interference signal. By modulating the operating current of the light source, the wavelength varies, which in turn modulates the optical path length difference between reference and measurement beams. This parameter change approach achieves distance measurement without mechanical movement.
2Measurement precision
If a piezoelectric bending arm is used to oscillate the probe head, then phase modulation is achieved, but the measurement data rate is limited to a few kilohertz
Solution Approach 1:
The patent replaces the mechanical oscillation system with an electrical/optical modulation system. The semiconductor light source can be modulated at much higher frequencies than mechanical systems allow, enabling measurement data rates in the hundreds of kilohertz range rather than just a few kilohertz. This eliminates the inertia limitation of the mechanical probe head oscillation.
Solution Approach 2:
The patent uses periodic modulation of the semiconductor light source wavelength through varying the operating current. This periodic action creates the necessary phase modulation for interferometric measurement at high frequencies. The modulation frequency can be chosen freely within the capabilities of the light source and detector, enabling high-speed measurements.
3Measurement precision
If a motion actuator is included in the fiber optic sensor, then distance measurement is possible, but the sensor size and complexity increase
Solution Approach 1:
The patent eliminates the motion actuator entirely by substituting mechanical probe head oscillation with optical wavelength modulation. The semiconductor light source is modulated electrically to achieve the same interferometric measurement function without requiring any moving parts in the probe head. This results in a much smaller, simpler sensor design.
Solution Approach 2:
The patent extracts and removes the motion actuator component from the fiber optic sensor system. By taking out the piezoelectric bending arm and replacing it with an electrical modulation approach applied to the light source, the design is simplified and the probe head size is reduced while maintaining measurement functionality.
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
Enables compact, robust fiber optic sensors with high measurement resolution and data rate without the need for a motion actuator, allowing for precise distance measurements.
Implementation Method 1
light from at least one semiconductor light source is fed into the fiber optic probe
Implementation Method 2
the semiconductor light source is operated with a periodically varying current, whereby a wavelength of the light emitted by the semiconductor light source also varies periodically
Implementation Method 3
A portion of the light emitted from a light exit of the probe onto a measurement object and reflected by the measurement object is made to interfere with a portion of the light reflected from a reference surface, whereby an interference signal is measured
Implementation Method 4
The interference signal can be measured, for example, with at least one photosensor
Data Source
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AI summary
The invention relates to a method for interferometric distance determination using a fiber optic probe (10), wherein light emitted from a light exit (111) of the probe (10) onto a measurement object (1) is caused to interfere with light reflected from the measurement object (1) by at least one semiconductor light source (23) feeding into the fiber optic probe, an interference signal is measured and a phase position of the measured interference signal with respect to a reference signal (Uref), which represents an oscillation position of the micro-optical probe (10), is used to determine the distance.The method is characterized in that the semiconductor light source (23) is operated with a periodically varying current, whereby a wavelength of the light emitted by the semiconductor light source (23) also varies periodically, and the phase of the measured interference signal with respect to the periodically varying current is used to determine the distance. The invention further relates to an arrangement configured for carrying out the method for interferometric distance determination.