Fringe analysis in scanning frequency interferometry for absolute distance measurement (original) (raw)
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Absolute Distance Measurement with Sub-Fringe Resolution
A novel technique to measure absolute distances is presented. It is based on a Michelson interferometer where two tuneable lasers are superposed to create a synthetic wavelength. Relative and absolute interferometry theories are merged together. Its experimental realization allows absolute distance measurements with sub-fringe resolution. Preliminary results are presented in this work.
Optics Express, 2012
We present a novel system that can measure absolute distances of up to 300 mm with an uncertainty of the order of one micrometer, within a timeframe of 40 seconds. The proposed system uses a Michelson interferometer, a tunable laser, a wavelength meter and a computer for analysis. The principle of synthetic wave creation is used in a novel way in that the system employs an initial low precision estimate of the distance, obtained using a triangulation, or time-of-flight, laser system, or similar, and then iterates through a sequence of progressively smaller synthetic wavelengths until it reaches micrometer uncertainties in the determination of the distance. A further novel feature of the system is its use of Fourier transform phase analysis techniques to achieve sub-wavelength accuracy. This method has the major advantages of being relatively simple to realize, offering demonstrated high relative precisions better than 5 × 10 −5. Finally, the fact that this device does not require a continuous line-of-sight to the target as is the case with other configurations offers significant advantages.
In this paper, we suggest a novel system that is capable of measuring absolute distances with an uncertainty of one micrometer, or better, over a distance of up to 20 meters. This system consists of a Michelson interferometer, a tunable external cavity diode laser, a wavelength meter, a digital camera and a computer. The Michelson interferometer contains a reference arm mirror, a target arm mirror, a coherent light source, a white screen and a beam-splitter. The distance between the beam-splitter and the reference arm is known a priori with one-micrometer accuracy. The distance between the beam-splitter and the required measurement target arm is initially known with only a low precision accuracy of one-millimeter. The distance between the beam-splitter and the target arm is required to be measured with one micrometer uncertainty, or better. Index Terms— Absolute distance measurement, external cavity tunable diode laser, Fourier fringe analysis, Michelson interferometer, synthetic wa...
Applied Optics, 2003
Interferometry associated with an external cavity laser of long coherence length and broad wavelength tuning range shows promising features for use in measurement of absolute distance. As far as we know, the processing of the interferometric signals has until now been performed by Fourier analysis or fringe counting. Here we report on the use of an autoregressive model to determine fringe pattern frequencies. This concept was applied to an interferometric device fed by a continuously tunable external-cavity laser diode operating at a central wavelength near 1.5 microm. A standard uncertainty of 4 x 10(-5) without averaging at a distance of 4.7 m was obtained.
Applied Optics, 2013
We present a frequency-sweeping heterodyne interferometer to measure an absolute distance based on a frequency-tunable diode laser calibrated by an optical frequency comb (OFC) and an interferometric phase measurement system. The laser frequency-sweeping process is calibrated by the OFC within a range of 200 GHz and an accuracy of 1.3 kHz, which brings about a precise temporal synthetic wavelength of 1.499 mm. The interferometric phase measurement system consisting of the analog signal processing circuit and the digital phase meter achieves a phase difference resolution better than 0.1 deg. As the laser frequency is sweeping, the absolute distance can be determined by measuring the phase difference variation of the interference signals. In the laboratory condition, our experimental scheme realizes micrometer accuracy over meter distance.
Absolute distance metrology for long distances with dual frequency sweeping interferometry
Proc. of XIX IMEKO World Congress, …
Coherent absolute distance interferometry is one of the most interesting techniques for length metrology. In frequency sweeping interferometry (FSI), measurements are made without ambiguity, by using a synthetic wavelengths resulting from a frequency sweep. Accuracy is mainly dependent on the capability to measure the synthetic wavelength, using a Fabry-Perot interferometer (FP) to count resonances as frequency sweeps, and therefore the number of detected synthetic fringes. For large ranges, the number of fringes dominates performance, leading to a linear decrease of the accuracy with range. By increasing the size of the interferometer reference arm, and measuring both the distance and the reference arm independently, it is possible to maintain small distance high accuracy measurements, even for much larger range.
Dual frequency sweeping interferometry with range-invariant accuracy for absolute distance metrology
Proceedings of SPIE - The International Society for Optical Engineering, 2008
Coherent absolute distance interferometry is one of the most interesting techniques for length metrology. In frequency sweeping interferometry (FSI), measurements are made without ambiguity, by using a synthetic wavelengths resulting from a frequency sweep. FSI-based sensors are simple devices and fulfill an important role on any demanding space mission metrological chain. Their parameterization flexibility allows either technological or application-related tradeoffs to be performed.
Absolute distance measurement with a gain-switched dual optical frequency comb
Optics Express
The measurement of distance plays an important role in many aspects of modern societies. In this paper, an absolute distance measurement method for arbitrary distance is proposed and demonstrated using mode-resolved spectral interferometry with a gain-switched dual comb. An accuracy of 12 µm, when compared to a He-Ne fringe counting laser interferometer, for a displacement up to 2.5 m is demonstrated by tuning the repetition frequency of the dual comb from 1.1 GHz to 1.4 GHz. The compact measurement system based on a gain-switched dual comb breaks the constraint of periodic ambiguity. The simplification and improvements are significant for further industrial applications.
Subnanometer absolute measurements by means of mixed synthetic-optical homodyne interferometer
2011
A possible technique to measure absolute distances is presented. It is based on a Michelson interferometer where two tuneable lasers are superposed to create a very short synthetic wavelength. By exploiting relative and absolute interferometry theories merged together in a demonstrator experiment we have shown the possibility of absolute distance measurements with sub-fringe resolution.
Precise interferometric length measurement using real-time fringe fitting
Optik, 2011
We created a simple device for the measurement of nanoscale displacements consisting in a Twyman-Green interferometer with one mirror having a slight offset in the horizontal plane with respect to the direction perpendicular to the incoming beam and one mobile mirror, a CCD array camera that captures frames of fringes (interferograms) generated by the interferometer and a software that acquires the interferograms captured by the camera and fits the fringes in order to determine the initial spatial phase of the series of fringes and, consequently, to monitor the movement of the mobile arm of the interferometer. Because the interferograms were acquired and analyzed sequentially, the algorithm could be parallelized easily on a multiprocessor/multicore platform. The device can work in real-time in which case the maximum speed of the mobile arm of the interferometer for which we can obtain unambiguous results is 30 /8/s, which is, assuming a He-Ne laser as the light source, almost 2.5 m/s. In real-time conditions, the precision and accuracy of the measurement are low. In stationary conditions, however, the precision was determined to be below 1 nm.