Abstract

A polarization Fourier spectrometer is described that improves on the previous versions built by others and can be used from 0.3 μ to 2.5 μ. Several practical problems in the construction and data reduction are discussed, and a number of typical results are presented to show the performance of the instrument.

© 1974 Optical Society of America

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References

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  1. L. Mertz, J. Phys. Rad. (Paris) 19, 233 (1958).
    [CrossRef]
  2. W. M. Sinton, J. Quant. Spectrosc. Rad. Trans. 3, 551 (1963).
    [CrossRef]
  3. L. Mertz, Astron. J. 71, 749 (1966).
    [CrossRef]
  4. W. H. Steel, Interferometry (Cambridge U. P., Cambridge, 1967), pp. 102ff.
  5. L. Mertz, Transformations in Optics (Wiley, New York, 1965), pp. 51ff.
  6. DC-200 silicone fluid has an index of refraction in the visible of roughly 1.4 and transmits from the uv to the ir. It is available in a wide range of viscosities from the Dow Corning Co.
  7. J. Connes, P. Connes, J. Opt. Soc. Am. 56, 896 (1966).
    [CrossRef]
  8. R. Hanel, M. Forman, T. Meilleur, R. Westcott, J. Pritchard, Appl. Opt. 8, 2059 (1969).
    [CrossRef] [PubMed]
  9. M. L. Forman, W. H. Steel, G. A. Vanasse, J. Opt. Soc. Am. 56, 59 (1966).
    [CrossRef]
  10. F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957), p. 542.
  11. J. B. Oke, R. E. Schild, Astrophys. J. 161, 1015 (1970).
    [CrossRef]
  12. References to previous calibrations of Regulus relative to Vega are D. H. P. Jones, I. Astron. Union Symp. 24 (Academic, New York, 1966), p. 141; K. Bahner, Astrophys. J. 138, 1314 (1963); J. B. Oke, Astrophys. J. 140, 689 (1964); D. S. Hayes, Astrophys. J. 159, 165 (1970).
    [CrossRef]

1970 (1)

J. B. Oke, R. E. Schild, Astrophys. J. 161, 1015 (1970).
[CrossRef]

1969 (1)

1966 (3)

1963 (1)

W. M. Sinton, J. Quant. Spectrosc. Rad. Trans. 3, 551 (1963).
[CrossRef]

1958 (1)

L. Mertz, J. Phys. Rad. (Paris) 19, 233 (1958).
[CrossRef]

Connes, J.

Connes, P.

Forman, M.

Forman, M. L.

Hanel, R.

Jenkins, F. A.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957), p. 542.

Jones, D. H. P.

References to previous calibrations of Regulus relative to Vega are D. H. P. Jones, I. Astron. Union Symp. 24 (Academic, New York, 1966), p. 141; K. Bahner, Astrophys. J. 138, 1314 (1963); J. B. Oke, Astrophys. J. 140, 689 (1964); D. S. Hayes, Astrophys. J. 159, 165 (1970).
[CrossRef]

Meilleur, T.

Mertz, L.

L. Mertz, Astron. J. 71, 749 (1966).
[CrossRef]

L. Mertz, J. Phys. Rad. (Paris) 19, 233 (1958).
[CrossRef]

L. Mertz, Transformations in Optics (Wiley, New York, 1965), pp. 51ff.

Oke, J. B.

J. B. Oke, R. E. Schild, Astrophys. J. 161, 1015 (1970).
[CrossRef]

Pritchard, J.

Schild, R. E.

J. B. Oke, R. E. Schild, Astrophys. J. 161, 1015 (1970).
[CrossRef]

Sinton, W. M.

W. M. Sinton, J. Quant. Spectrosc. Rad. Trans. 3, 551 (1963).
[CrossRef]

Steel, W. H.

M. L. Forman, W. H. Steel, G. A. Vanasse, J. Opt. Soc. Am. 56, 59 (1966).
[CrossRef]

W. H. Steel, Interferometry (Cambridge U. P., Cambridge, 1967), pp. 102ff.

Vanasse, G. A.

Westcott, R.

White, H. E.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957), p. 542.

Appl. Opt. (1)

Astron. J. (1)

L. Mertz, Astron. J. 71, 749 (1966).
[CrossRef]

Astrophys. J. (1)

J. B. Oke, R. E. Schild, Astrophys. J. 161, 1015 (1970).
[CrossRef]

J. Opt. Soc. Am. (2)

J. Phys. Rad. (Paris) (1)

L. Mertz, J. Phys. Rad. (Paris) 19, 233 (1958).
[CrossRef]

J. Quant. Spectrosc. Rad. Trans. (1)

W. M. Sinton, J. Quant. Spectrosc. Rad. Trans. 3, 551 (1963).
[CrossRef]

Other (5)

References to previous calibrations of Regulus relative to Vega are D. H. P. Jones, I. Astron. Union Symp. 24 (Academic, New York, 1966), p. 141; K. Bahner, Astrophys. J. 138, 1314 (1963); J. B. Oke, Astrophys. J. 140, 689 (1964); D. S. Hayes, Astrophys. J. 159, 165 (1970).
[CrossRef]

W. H. Steel, Interferometry (Cambridge U. P., Cambridge, 1967), pp. 102ff.

L. Mertz, Transformations in Optics (Wiley, New York, 1965), pp. 51ff.

DC-200 silicone fluid has an index of refraction in the visible of roughly 1.4 and transmits from the uv to the ir. It is available in a wide range of viscosities from the Dow Corning Co.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1957), p. 542.

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Figures (8)

Fig. 1
Fig. 1

Optical schematic diagram of instrument. For details see discussion in text. Orientation of polarizing components to produce the appropriately polarized beams can be seen, for example, in Fig. 1 of Mertz.3

Fig. 2
Fig. 2

Hyperbolic fringe pattern. Fringe pattern photographed in different colors through the entire instrument with field stop diaphragms removed. a, b, and c are relatively narrow-band photographs in blue, green, and red light, respectively, taken at the same wedge position while d is a white light photograph. All photographs were taken with the wedge set nominally for the white light fringe. The variations with colors of the central fringe are due to the large phase shift introduced by the air gap in the Babinet-Soleil compensator.

Fig. 3
Fig. 3

Instrumental phase correction. A typical low resolution curve of the sine of the phase of the interferogram as a function of wavenumber before any symmetrizing is performed. The nonsinusoidal nature of the curve is due primarily to the refraction at the air gap of the Babinet-Soleil compensator.

Fig. 4
Fig. 4

Instrument line shape. The profile of the green (5461-Å) mercury line as determined by an 8192-point transform with no apodization. Every fifth point is an actual data point while intermediate points have been interpolated with an appropriate sinc function. Full width half-maximum is 2.1 Å (7.0 cm−1); full width first nulls is 3.4 Å (11.3 cm−1).

Fig. 5
Fig. 5

Operation of automatic sky subtraction. Spectra of Neptune obtained from 256-point interferograms obtained with the University of Maryland 50-cm (20-in.) telescope. Spectral resolution with this number of points is roughly 410 cm−1 (100 Å at 5000 Å). The upper spectrum was obtained with the automatic sky subtraction suppressed while the lower spectrum (which has been displaced vertically) was obtained immediately thereafter with the sky subtraction operating. Night sky mercury features, due to lights of Washington, D.C. and of the university campus, are identified in the upper spectrum but are seen to be virtually eliminated from the lower scan revealing the methane absorption features characteristic of Neptune itself. Integration time was one sec/data point, and the instrumental response has not been corrected for.

Fig. 6
Fig. 6

Ratio of the intensity per unit wavenumber of Regulus to that of Vega. Vega is the traditional standard star for absolute energy calibrations and is used here also because it has a spectrum similar to that of Regulus, thus yielding a relatively constant intensity ratio. Most of the observations, including our own, represent integrations over the bandpasses of Oke and Schild,11 but some of the other observations12 refer to nonstandard bandpasses. Since the spectrum of Regulus has few lines, this has little effect. Error bars represent plus and minus one standard deviation as quoted by the various authors, and it is clear that the agreement is well within the statistical accuracy of the data.

Fig. 7
Fig. 7

Spectrum of 15 CVn based on 256-point interferogram obtained in 1 min of observation with 188-cm (74-in.) telescope at David Dunlap Observatory. Atmospheric extinction and instrumental response have not been removed. Points of discrete Fourier transform are arbitrarily connected by straight lines rather than interpolated. Noise is less than 1% of peak intensity and is consistent with expected photon statistics.

Fig. 8
Fig. 8

Spectrum of planetary nebula NGC 6572 based on 2048-point interferogram obtained in 20 min of observation with 188-cm (74-in.) telescope at David Dunlap Observatory. Atmospheric extinction and instrumental response have not been removed. Points are arbitrarily connected by straight lines. Line identifications are from previous investigators. Strongest lines have been cut off in figure, actual heights indicated by numbers in ( ) at top of figure. No identifications attempted in vicinity of 5000 Å due to confusion with side lobes of [0 III] lines.

Equations (7)

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B ( σ ) = k = 0 N - 1 A ( x k ) [ I ( x k ) - I ¯ ] × cos ( 2 π σ x k ) ( 2 - δ k 0 - δ k N - 1 ) ,
2 ( σ ) = k = 0 N - 1 A 2 ( x k ) e k 2             cos 2 ( 2 π σ x k ) ( 2 - δ k 0 - δ k N - 1 ) 2 ,
2 = e 2 ( 1 τ 0 + 2 k = 0 N - 1 A k 2 / τ k + 1 2 A N - 1 2 / τ N - 1 ) .
2 = e 2 k = 0 N - 1 w k 2 / τ k ,
τ k = T w k / k = 0 N - 1 w k .
2 = e 2 T ( k = 0 N - 1 w k ) 2 .
2 = e 2 T N k = 0 N - 1 w k 2 .

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