Fringe analysis in scanning frequency interferometry for absolute distance measurement (original) (raw)
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.
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.
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.
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.
IMTC/98 Conference Proceedings. IEEE Instrumentation and Measurement Technology Conference. Where Instrumentation is Going (Cat. No.98CH36222), 1998
The paper reports results of an investigation on the main measurement uncertainty sources in a novel distance meter based on dispersive comb-spectrum interferometry. The light source is a commercial laser diode operating at 670 nm driven under the threshold condition, and emitting a beam with a comb-shaped spectrum. Sensitivity of the measurement to the operating conditions has been evaluated. Results from an experimental activity aimed at characterizing the laser and to measure the performance of a prototype implementation are also presented. The system is suitable to perform unambiguous non-incremental distance measurements over a range of 0.8 mm with a total uncertainty of about 1.5 pm.
Applied Optics, 1987
A method for measuring absolute distance by the wavelength shift of laser diode light has previously been proposed. In this work three serious systematic error sources for the method are discussed and some of the discussion is confirmed by experiment. The error sources are optical feedback effect, longitudinal mode distribution of laser light, and unwanted light reflected from optical devices (coherent noise). The optical feedback effect influences the wavelength shift of the emitted light. The mode distribution causes the periodic error dependent on the measured distance, and the maximum error is determined by the change in the intensity ratio of the submodes to the main mode. Coherent noise causes the periodic error also dependent on the distance, and the maximum error is determined by the amplitude ratio of the measuring lightwave to the noise. These systematic errors are observed in some demonstrative experiments.
IEEE Transactions on Instrumentation and Measurement, 2007
We present a new method for the measurement of the absolute distance of a remote target based on the laser diode self-mixing interferometry technique, which is assisted by an electronic feedback loop that is capable of improving the measurement accuracy. The feedback loop supplies a periodic change of the emitted wavelength that exactly corresponds to a single interferometric fringe. This allows the measurement of the target distance with higher accuracy, which, in principle, is limited only by the detection shot noise and not by the fringe quantization error that is typical for the conventional fringe-counting approaches. We developed a prototype that is capable of measuring the target distance with 0.3-mm accuracy in the 0.2-to 3-m range.
Optical Review, 2009
Based on the technique of dual-wavelength and principle of heterodyne interferometry, a modified method for measuring the absolute distance is proposed. Because two test lights suffer from the same influence of wavelength drift in the measurement setup, the minus effect coming from the wavelength drift can be offset. Therefore, the measurement accuracy can be significantly increased. The feasibility of this method was demonstrated with a measurement resolution of about 1.50 mm. This method provides the advantages of a simple optical setup, easy operation and rapid measurement. #
Optics & Laser Technology, 2008
The coherence length of a single mode laser diode (LD) can reach more than 10 m. It allows the application of this source of light to interferometric distance measurement, with a measurement range of several meters. However, the LD's wavelength tunability, which is a result of the dependence of the lasing wavelength on the injection current, prevents the realization of the theoretically possible metrological parameters of the interferometer. In this study, we analyze the influence of a low-frequency signal disturbance, e.g., noise or disturbing modulation inherent to the injection current of the LD, on the repeatability and measurement range of an LD interferometer used for displacement measurements. Both the measurement range and the resolution of the interferometer are found to be highly limited by this factor.
Dimensional Metrology and Frequency Sweeping Interferometry
Modern Metrology Concerns, 2012
Absolute distance metrology is needed for a wide gamut of applications with different 9 ranges and resolutions. One good example is space missions requiring independent 10 satellites working cooperatively: the management of such formations requires several levels 11 of metrology to keep the formation coherent and to enable guidance and navigation of the 12 complete formation (Calvel et al., 2004). Beyond a certain level of accuracy, at the end of the 13 metrology chain, optical metrology becomes mandatory to achieve the required high 14 accuracy.
Sensors, 2020
Micro absolute distance measurement (MADM) is widely used in industrial and military fields. To achieve high accuracy and frequency response, a polarized low-coherence interferometry (PLCI)-based method for MADM is proposed. The nearly linear relationship between the envelope center and m-order PLCI fringe (PLCIF) peak center is found and verified. Dispersion compensation is achieved by fringe peak position estimation and polynomial fitting to get rid of the dependence on an a priori model and birefringence parameters, and make this method very robust. Meanwhile, the zero-order PLCIF center is estimated and located to demodulate the measured displacement. Then, the measurement accuracy is raised by polynomial fittings. In comparison to conventional methods, the proposed method can effectively avoid jump errors and has a higher accuracy. Experimental results indicate that the measurement accuracy is higher than 19.51 nm, the resolution is better than 2 nm, and its processing data rat...
Absolute Distance (Thickness) Metrology Using Wavelength Scanning Interferometry
2009
AMIT RAVINDRA SURATKAR. Absolute Distance (Thickness) metrology using wavelength scanning interferometry. (Under the direction of DR. ANGELA D. DAVIES) Wavelength scanning interferometry offers a new dimension in precision metrology by measuring the cavity length (thickness), the cavity length variation over the cavity area (flatness), and the optical homogeneity within a transparent cavity; without any mechanical movement by implementing a tunable laser. This property is useful when the physical movement of an optic is not feasible using traditional phase shifting methods employing piezoelectric transducers and for characterizing solid optical cavities which require movement of one surface relative to the other. The cavity length that can be measured is limited by the wavelength scanning range a smaller cavity requires a larger tuning range. Tunable lasers are now available with very large tuning ranges in the near infrared, potentially extending the measurement range significantly...
Interference fringe detection system for distance measuring interferometer
Optics & Laser Technology, 2012
A novel photodetection system for a homodyne distance measuring interferometer by means of fringe counting method is presented. The system is based on applying compact size integrated photodetector operating with fringe pattern having fixed, finite period. 13-element integrated photodiode arranged in novel signal processing scheme receives interference fringes movement. Additional lens is used to adjust the fringe period to photoelements' distances. Due to the proposed configuration of the photoelement's signal processing and the applied lens the system has reduced sensitivity to interference fringe period errors caused by the angular misalignment of interfering beams. The theoretical analysis and experimental verification of the system metrological feasibilities are presented. Comparison of performance of examples of standard and novel detection systems is shown finally.
Physica Scripta, 2012
In this paper a simple low-coherence interferometric sensor for absolute position measurement based on central fringe maximum identification is presented. The channeled spectrum, captured by a commercial spectrometer, is analyzed by using the algorithm based on the fitting of the calculated autocorrelation function of the captured optical power spectrum with the sum of two Gaussian functions. The position of the central fringe is obtained directly from the separation between two fitted Gaussian functions. In order to boost the precision of such a built sensing system the position of the maximum of the central fringe is identified by a simple algorithm. The system currently provides unambiguous measurement over a range of 200 µm with a mid range error less than 1.4 nm. In addition to this, the sensor is characterized by a very small sensing head (bare single-mode fiber with the diameter of 125 µm) and by very high resistance to environmental influences, thus enabling the possibility of using very long down-lead sensing fiber.