Measurement of the group refractive index of air by two-wavelength interferometry

An improved two-colour interferometer for length measurements was developed to reduce both the errors caused by air turbulence and the effects of chromatic aberration in the optical system. The method combines a fringe-counting technique and a phase-measurement technique. The phases of interference fringes with respect to laser wavelength 1 and synthetic wavelength s are detected simultaneously by only one detector by using a band-pass filter technique. We verified this new method by measuring lengths of up to 2 m and then comparing the results with those measured by an HP 5528 interferometer. The comparison shows that the relative accuracy of this improved method is 5 × 10-7.

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“…which can be derived from two-colour interferometry equations [6]. Equation ( 1) is then expressed by:…”

Section: Principlementioning

confidence: 99%

Length measurement by a two-colour interferometer using two close wavelengths to reduce errors caused by air turbulence

Zeng

Seta²,

Matsumoto³

et al. 1999

Meas. Sci. Technol.

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Group-phase refractive index method for improving the accuracy in two-color interferometric length measurements

Zeng

Matsumoto²,

Seta³

1999

Review of Scientific Instruments

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A group-phase refractive index method was developed for improving the accuracy of a conventional two-color method used in an interferometer for length measurements. This method uses two closer wavelengths to reduce the errors caused by air turbulence and the chromatic aberration. We describe the new method and demonstrate preliminarily its effectiveness by measuring the group refractive index of air using a vacuum cell. We then compared the results with those calculated using the Edlén equation. The mean difference between the measured and calculated values was 2.15×10−6 with a standard deviation of 2.0×10−6 for the vacuum cell with a length of 184.5 mm.

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Two-color absolute length measuring method based on pulse repetition interval lengths

et al. 2014

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Measurement of the group refractive index of air by two-wavelength interferometry

Cited by 4 publications

References 5 publications

Length measurement by a two-colour interferometer using two close wavelengths to reduce errors caused by air turbulence

Length measurement by a two-colour interferometer using two close wavelengths to reduce errors caused by air turbulence

Group-phase refractive index method for improving the accuracy in two-color interferometric length measurements

Two-color absolute length measuring method based on pulse repetition interval lengths

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