High-accuracy absolute distance measurement by means of wavelength scanning heterodyne interferometry

Dai, Xiaoli; Seta, Katuo

doi:10.1088/0957-0233/9/7/004

Cited by 78 publications

(30 citation statements)

References 13 publications

(14 reference statements)

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“…A significant amount of research on ADM's using wavelength scanning interferometers already exists. 3,4,5,6,7,8 In one of the most comprehensive publications on this subject, Stone et al describe in detail a wavelength scanning heterodyne interferometer consisting of a system built around both a reference and a measurement interferometer, 3 the measurement precisions of absolute distance ranging from 0.3 to 5 meters are ∼ 250 nm by averaging distance measurements from 80 independent scans.…”

Section: Introductionmentioning

confidence: 99%

High-precision absolute distance and vibration measurement with frequency scanned interferometry

et al. 2005

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In this paper, we report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. A high-finesse Fabry-Perot interferometer(F-P) was used to determine frequency changes during scanning. Two multiple-distance-measurement analysis techniques were developed to improve distance precision and to extract the amplitude and frequency of vibrations. Under laboratory conditions, measurement precision of ∼ 50 nm was achieved for absolute distances ranging from 0.1 meters to 0.7 meters by using the first multiple-distance-measurement technique. The second analysis technique has the capability to measure vibration frequencies ranging from 0.1 Hz to 100 Hz with amplitude as small as a few nanometers, without a priori knowledge.

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Section: Introductionmentioning

confidence: 99%

High-precision absolute distance and vibration measurement with frequency scanned interferometry

et al. 2005

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“…The first term gives the correct distance at time t = 0. The second term, however, is proportional to the speed L 1 and contains the same large factor / ⌬ that was previously encountered in relation (4). Note that this term is also dependent on ⌬ and thus on the direction of the frequency sweep.…”

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confidence: 63%

“…The first large error term only appears in third order. Relation (4) shows that ⌬ should be chosen as large as possible to reduce the measurement errors. The type of laser limits this to a value of the order of 100 GHz.…”

Section: ͑9͒mentioning

confidence: 99%

“…1,2 Truly absolute, single-stage distance measurements can be made by sweeping a laser over a known wavelength range and measuring the phase difference interferometrically during the sweep, usually called frequency-sweeping interferometry. 3,4 This method suffers from a basic drawback that has large consequences if the target moves during a measurement. A movement of the target over one optical wavelength is interpreted as the movement over one synthetic wavelength.…”

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confidence: 99%

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Correcting movement errors in frequency-sweeping interferometry

2005

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Absolute distance measurements can be performed with an interferometric method that uses only a single tunable laser. This method has one major drawback, because a small target movement of the order of one wavelength during a measurement will be interpreted as a movement of one synthetic wavelength. This effect is usually mitigated by adding a second (nonscanning) laser. We show that absolute distance measurements can be performed with only one laser if the movements encountered are smooth, on the time scale of one measurement. In this case the movement errors can be compensated with a simple algorithm that combines several subsequent measurements. Several different techniques can be used to measure absolute distances, among which are time-of-flight measurements, high-frequency modulation schemes, and interferometric methods. Of these, only the last two have the potential to achieve resolutions below a millimeter over several hundred meters. Most of these methods are not truly absolute distance measurements, but systems that are sensitive to changes on the scale of a certain synthetic wavelength. The total distance can be calculated only with a priori (low-resolution) knowledge of the distance or by cascading a number of systems with decreasing synthetic wavelengths. 1,2 Truly absolute, single-stage distance measurements can be made by sweeping a laser over a known wavelength range and measuring the phase difference interferometrically during the sweep, usually called frequency-sweeping interferometry. 3,4 This method suffers from a basic drawback that has large consequences if the target moves during a measurement. A movement of the target over one optical wavelength is interpreted as the movement over one synthetic wavelength. This problem is usually solved by adding a second laser, which reduces the sensitivity to movements of the order of the synthetic wavelength itself. 5,6 We explore a solution without a second laser, by measuring in the presence of movements and correcting for the movement errors in the data analysis. Our intended application is absolute distance metrology between satellites. The Darwin Space Interferometer, for example, would require knowledge of the absolute distance between two satellites with an accuracy of better than 100 m over a distance of 250 m. Consider an optical interferometer with a fixed optical path length difference L that is equipped to measure phase as a function of time. For fixed or slowly changing optical frequency , the phase is proportional to both the length and the frequency. Because the phase is usually measured modulo 2, the absolute phase is unknown. By unwrapping the phase over time it is, however, possible to measure phase differences. If the light source is a tunable laser that is swept from optical frequency 1 to 2 , the total phase difference will bewith c the speed of light, ⌬ the frequency difference of the sweep, and ⌳ the so-called synthetic wavelength defined byReversing Eq. (1), the length L should be calculated asThe length is thus directly proporti...

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“…Frequency sweeping interferometry ͑FSI͒ is one of them, generating a synthetic wavelength ͑much longer than the optical wavelength͒ that increases with decreasing sweep range. [2][3][4] The technique is not new, dating back ͑at least͒ to the 1980's ͑Ref. 5͒, but was not studied extensively until the development of tunable lasers and the emergence of external cavity diode lasers ͑ECDLs͒.…”

Section: Introductionmentioning

confidence: 99%

Calibration of the Fabry-Pérot free spectral range using a tunable laser in a Michelson interferometer

Cabral

Rebordão

2006

Opt. Eng

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Abstract. Coherent interferometric absolute distance metrology enables different techniques for length metrology. Measurements are made without ambiguity, by using either one or several synthetic wavelengths resulting from the beating of two or more wavelengths or, in the case of frequency sweeping interferometry ͑FSI͒, from a frequency sweep. These techniques require accurate measurements of the frequency variation, a task which is usually performed with a Fabry-Pérot ͑FP͒ interferometer. Sensor performances are highly dependent on the FP free spectral range ͑FSR͒, which must be accurately known. We describe a method to measure the FSR of an FP using a tunable laser in a Michelson interferometer, using both absolute and relative distance measurements. The optical setup is based on a frequency-sweeping sensor and a controlled translation table. An uncertainty of 45 ppm in the measurement of a 1-GHz FSR is obtained. The method is indicated for the calibration of the FP in the frequency-sweep-range-measuring subsystem of a frequency sweeping sensor absolute distance sensor as it does not require any addition hardware, configuring a self-calibration approach.

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High-accuracy absolute distance measurement by means of wavelength scanning heterodyne interferometry

Cited by 78 publications

References 13 publications

High-precision absolute distance and vibration measurement with frequency scanned interferometry

High-precision absolute distance and vibration measurement with frequency scanned interferometry

Correcting movement errors in frequency-sweeping interferometry

Calibration of the Fabry-Pérot free spectral range using a tunable laser in a Michelson interferometer

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