Abstract

We have developed a millimeter and submillimeter Michelson-type bolometric interferometer based on a Martin–Puplett-type Fourier-transform spectrometer named multi-Fourier-transform interferometer (MuFT). We have succeeded in proving that the MuFT is capable of performing broadband imaging observations as theoretically proposed by our previous paper (OHM) [Appl. Opt. 45, 2576 (2006)]. We succeeded in acquiring the mutual coherence signal for an extended source in broadband. By analyzing the obtained mutual coherence signal following the formula proposed in OHM, 2D source images for each wavenumber from 5cm1(150GHz) to 35cm1(1.05THz) with a wavenumber interval of 0.4cm1(12GHz) were successfully extracted. The large dynamic range advantage of the MuFT proposed in OHM was confirmed experimentally.

© 2007 Optical Society of America

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References

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  1. A. R. Thompson, J. M. Moran, and G. W. Swenson, Jr., Interferometry and Synthesis in Radio Astronomy, 2nd ed. (Wiley-Interscience, 2001).
    [CrossRef]
  2. I. S. Ohta, M. Hattori, and H. Matsuo, "Development of multi-Fourier transform interferometer: fundamental," Appl. Opt. 45, 2576-2585 (2006).
    [CrossRef] [PubMed]
  3. J. E. Conway, T. J. Cornwell, and P. N. Wilkinson, "Multi-frequency synthesis: a new technique in radio interferometric imaging," Mon. Not. R. Astron. Soc. 246, 490-509 (1990).
  4. R. A. Sunyaev and B. Ya. Zel'dovich, "The observations of relic radiation as a test of the nature of x-ray radiation from the clusters of galaxies," Comments Astrophys. Space Phys. 4, 173-178 (1972).
  5. M. Hattori and N. Okabe, "A direct method for measuring heat conductivity in intracluster medium," Astrophys. J. 625, 741-747 (2005).
    [CrossRef]
  6. D. H. Martin and E. Puplett, "Polarized interferometric spectrometry for the millimetre and submillimetre spectrum," Infrared Phys. 10, 105-109 (1969).
    [CrossRef]
  7. M. Born and E. Wolf, Principles of Optics, 5th ed. (Pergamon, 1975), Chap. 10.

2006 (1)

2005 (1)

M. Hattori and N. Okabe, "A direct method for measuring heat conductivity in intracluster medium," Astrophys. J. 625, 741-747 (2005).
[CrossRef]

1990 (1)

J. E. Conway, T. J. Cornwell, and P. N. Wilkinson, "Multi-frequency synthesis: a new technique in radio interferometric imaging," Mon. Not. R. Astron. Soc. 246, 490-509 (1990).

1972 (1)

R. A. Sunyaev and B. Ya. Zel'dovich, "The observations of relic radiation as a test of the nature of x-ray radiation from the clusters of galaxies," Comments Astrophys. Space Phys. 4, 173-178 (1972).

1969 (1)

D. H. Martin and E. Puplett, "Polarized interferometric spectrometry for the millimetre and submillimetre spectrum," Infrared Phys. 10, 105-109 (1969).
[CrossRef]

Born, M.

M. Born and E. Wolf, Principles of Optics, 5th ed. (Pergamon, 1975), Chap. 10.

Conway, J. E.

J. E. Conway, T. J. Cornwell, and P. N. Wilkinson, "Multi-frequency synthesis: a new technique in radio interferometric imaging," Mon. Not. R. Astron. Soc. 246, 490-509 (1990).

Cornwell, T. J.

J. E. Conway, T. J. Cornwell, and P. N. Wilkinson, "Multi-frequency synthesis: a new technique in radio interferometric imaging," Mon. Not. R. Astron. Soc. 246, 490-509 (1990).

Hattori, M.

I. S. Ohta, M. Hattori, and H. Matsuo, "Development of multi-Fourier transform interferometer: fundamental," Appl. Opt. 45, 2576-2585 (2006).
[CrossRef] [PubMed]

M. Hattori and N. Okabe, "A direct method for measuring heat conductivity in intracluster medium," Astrophys. J. 625, 741-747 (2005).
[CrossRef]

Martin, D. H.

D. H. Martin and E. Puplett, "Polarized interferometric spectrometry for the millimetre and submillimetre spectrum," Infrared Phys. 10, 105-109 (1969).
[CrossRef]

Matsuo, H.

Moran, J. M.

A. R. Thompson, J. M. Moran, and G. W. Swenson, Jr., Interferometry and Synthesis in Radio Astronomy, 2nd ed. (Wiley-Interscience, 2001).
[CrossRef]

Ohta, I. S.

Okabe, N.

M. Hattori and N. Okabe, "A direct method for measuring heat conductivity in intracluster medium," Astrophys. J. 625, 741-747 (2005).
[CrossRef]

Puplett, E.

D. H. Martin and E. Puplett, "Polarized interferometric spectrometry for the millimetre and submillimetre spectrum," Infrared Phys. 10, 105-109 (1969).
[CrossRef]

Sunyaev, R. A.

R. A. Sunyaev and B. Ya. Zel'dovich, "The observations of relic radiation as a test of the nature of x-ray radiation from the clusters of galaxies," Comments Astrophys. Space Phys. 4, 173-178 (1972).

Swenson, G. W.

A. R. Thompson, J. M. Moran, and G. W. Swenson, Jr., Interferometry and Synthesis in Radio Astronomy, 2nd ed. (Wiley-Interscience, 2001).
[CrossRef]

Thompson, A. R.

A. R. Thompson, J. M. Moran, and G. W. Swenson, Jr., Interferometry and Synthesis in Radio Astronomy, 2nd ed. (Wiley-Interscience, 2001).
[CrossRef]

Wilkinson, P. N.

J. E. Conway, T. J. Cornwell, and P. N. Wilkinson, "Multi-frequency synthesis: a new technique in radio interferometric imaging," Mon. Not. R. Astron. Soc. 246, 490-509 (1990).

Wolf, E.

M. Born and E. Wolf, Principles of Optics, 5th ed. (Pergamon, 1975), Chap. 10.

Zel'dovich, B. Ya.

R. A. Sunyaev and B. Ya. Zel'dovich, "The observations of relic radiation as a test of the nature of x-ray radiation from the clusters of galaxies," Comments Astrophys. Space Phys. 4, 173-178 (1972).

Appl. Opt. (1)

Astrophys. J. (1)

M. Hattori and N. Okabe, "A direct method for measuring heat conductivity in intracluster medium," Astrophys. J. 625, 741-747 (2005).
[CrossRef]

Infrared Phys. (1)

D. H. Martin and E. Puplett, "Polarized interferometric spectrometry for the millimetre and submillimetre spectrum," Infrared Phys. 10, 105-109 (1969).
[CrossRef]

Mon. Not. R. Astron. Soc. (1)

J. E. Conway, T. J. Cornwell, and P. N. Wilkinson, "Multi-frequency synthesis: a new technique in radio interferometric imaging," Mon. Not. R. Astron. Soc. 246, 490-509 (1990).

Space Phys. (1)

R. A. Sunyaev and B. Ya. Zel'dovich, "The observations of relic radiation as a test of the nature of x-ray radiation from the clusters of galaxies," Comments Astrophys. Space Phys. 4, 173-178 (1972).

Other (2)

M. Born and E. Wolf, Principles of Optics, 5th ed. (Pergamon, 1975), Chap. 10.

A. R. Thompson, J. M. Moran, and G. W. Swenson, Jr., Interferometry and Synthesis in Radio Astronomy, 2nd ed. (Wiley-Interscience, 2001).
[CrossRef]

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Figures (13)

Fig. 1
Fig. 1

Flow chart of the image synthesis method in the MuFT.

Fig. 2
Fig. 2

Coordinate systems and designations used in the observation of the extended source. The source is assumed to be very far away. (This figure refers to Fig. 1 in OHM.)

Fig. 3
Fig. 3

Illustration of the source and light collecting part (LiC). Top view is shown in (A) and side view is shown in (B). A photograph taken from the collimation mirror side is shown in (C). A blackbody source is designated as the source. Images of two wire grids under the two entrance windows of the FI part, WGs 1 and 2, are visible in the mirrors (1.a) and (2.a). These are apertures of the MuFT. The interval of the center of these images is the baseline length of the MuFT.

Fig. 4
Fig. 4

Optical layout of FI autocorrelation mode (AC mode; A) and FI mutual-correlation mode (MC mode; B). In the AC mode, the input beam is guided to WG3 through WG0. The AC mode can measure the autocorrelation interferogram only. In the MC mode, consider light rays that enter WGs 1 and 2 along the vertical axis. From the viewer's point of view, these beams run vertically in this figure to WGs 1 and 2. Rays reflected by the WGs travel toward roof-top mirrors along a horizontal axis.

Fig. 5
Fig. 5

Fourier spectrum of the blackbody source with mask A obtained in the AC mode. Upper panels showed amplitudes and lower panels showed phases in deg.

Fig. 6
Fig. 6

The baseline vector is measured with Mask A. The vector point of the baseline length is × acquired data. The baseline number is 54 (baseline length is from 18 to 28 cm, every 2 cm, and baseline angles are 30°, 45°, 60°, and 90°).

Fig. 7
Fig. 7

Analysis of interferogram when b = 18 cm and θ = 0°. The horizontal axis shows the sampling point number while the moved RTM was performing a way scan. This corresponds to the internal time lag τ. An interval of the sampling point corresponds to 5.062 μ m of the light-path-length difference, which is equivalent to the time lag of 1.687 × 10 14 s. (A) Fluctuation of DC was removed by baseline fitting, (B) interferogram after background subtraction, and (C) interferogram after central position correction so that the center of the interferogram reaches the center of the scan, and a phase of the complex visibility function becomes as explained in Section 4.

Fig. 8
Fig. 8

Fourier spectrum of the blackbody source with mask A obtained in the MC mode. Upper panels showed amplitudes and lower panels showed phases in degrees.

Fig. 9
Fig. 9

Maps obtained for three frequencies at 10 cm 1 ( 300 GHz ) , 15 cm 1 ( 450 GHz ) , and 20 cm 1 ( 600 GHz ) appear in right panels from top to bottom. For comparison, simulated maps also appear in left panels. A vertical and a horizontal axis are angular radius in the image plane, θ x and θ y , in radians. The amplitude of each contour map is normalized by the maximum value in each map. Contour levels are from 1.0 to 1.0 every 0.2 step.

Fig. 10
Fig. 10

Amplitude of the exact complex visibility function when the baseline vector is ( 18 cm , 0 c m ) , Mask A.

Fig. 11
Fig. 11

Comparison of the simulated synthesized images (left) and the observed synthesized images (right) of Mask A (top) and Mask B (bottom) obtained by applying the so-called large-dynamic range advantage of the MuFT. Vertical and a horizontal axes are θ x and θ y in radians, respectively. The contour maps are normalized by the maximum value in the map. Contour levels are from 1.0 to 1.0 every 0.2 steps.

Fig. 12
Fig. 12

Sampled points on the baseline vector plane for supplemental imaging experiments with different masks. The number of sampled points was 18 (baseline length is 18, 28, and 38 cm, baseline angle is 30°, 60°, and 90°).

Fig. 13
Fig. 13

Complex visibility functions of mask B obtained by the MC mode measurement with b x = 18 cm and b y = 0 cm are shown in left panels. The upper left panel shows amplitudes and lower left panel shows phases in deg. The observed and simulated maps of the mask at 30 cm 1 are shown in the top right and bottom right panels, respectively.

Tables (1)

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Table 1 Parameters of Imaging Experiments

Equations (5)

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Γ 12 ( b , τ ) Γ 12 ( τ ) = Ω { I ( θ , ν ) exp [ 2 π j ν c ( b · θ ) + 2 π j ν τ ] d ν } d 2 θ ,
Γ 12 ( r ) ( b , τ ) Γ 12 ( r ) ( τ ) = Ω { I ( θ , ν ) cos [ 2 π ν c ( b · θ ) + 2 π ν τ ] d ν } d 2 θ ,
Γ ^ 12 ( u , v , ν ) = Ω I ˜ ( θ , ν ) exp [ 2 π j ( u θ x + v θ y ) ] d 2 θ .
I ( θ , ν ) = Γ ^ 12 ( u , v , ν ) exp [ 2 π j ( u θ x + v θ y ) ] d u d v .
2 π 0 { 0 ν Γ ^ 12 ( b , ν ) i ˜ ( ν ) exp [ 2 π j ν c ( b · θ ) ] d ν } b 2 c 2 d φ = Γ ^ 12 ( u , v , ν ) i ( ν ) exp [ 2 π j ( u θ x + v θ y ) ] d u d v = B ( θ ) .

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