Abstract

It is shown how fast (50–100 kHz) piezoelastic modulation of the full Stokes vector can be used in combination with large CCD-type detector arrays with long integration times. The technique is to use an optical demodulation system (replacing the lockin amplifiers in corresponding single-channel detector systems). This allows the CCD detectors to be used with integration times and readout rates as in ordinary photometry. Including an optical phase switch in the system, the effect of the large pixel-to-pixel sensitivity variations can be removed from the recorded polarization images. The beam splitter that suppresses atmospheric noise can be located immediately before the detectors instead of being part of the polarization analyzer.

© 1985 Optical Society of America

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References

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  1. A. Dollfus, “The French Solar Photoelectric Polarimeter and its Applications for Solar Observations,” in Planets, Stars and Nebulae, T. Gehrels, Ed. (U. Arizona Press, Tucson, 1974), pp. 695–729.
  2. J. O. Stenflo, “Solar Magnetic and Velocity-Field Measurements: New Instrument Concepts,” Appl. Opt. 23, 1267 (1984).
    [CrossRef] [PubMed]
  3. J. O. Stenflo, “Polarimeter Package for LEST,” LEST Technical Report 4 (Institute of Theoretical Astrophysics, U. Oslo, 1984).
  4. T. E. Andersen, R.B. Dunn, O. Engvold, “LEST Design Study,” LEST Technical Report 7 (Institute of Theoretical Astrophysics, U. Oslo, 1984).
  5. J. C. Kemp, “Piezo-optical Birefringent Modulators,” J. Opt. Soc. Am. 59, 950 (1969).
  6. M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
    [CrossRef]
  7. W. C. Livingston, J. W. Harvey, D. Trumbo, C. Slaughter, “Solar Magnetograph Employing Integrated Diode Arrays,” Appl. Opt. 15, 40 (1976).
    [CrossRef] [PubMed]
  8. D. M. Rust, “Some Design Considerations for a Satellite-borne Magnetograph,” in Measurements of Solar Vector Magnetic Fields, M. J. Hagyard, Ed., NASA Conf. Publ. 2374 (1985), pp. 141–152.

1984 (1)

1976 (1)

1974 (1)

M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
[CrossRef]

1969 (1)

Andersen, T. E.

T. E. Andersen, R.B. Dunn, O. Engvold, “LEST Design Study,” LEST Technical Report 7 (Institute of Theoretical Astrophysics, U. Oslo, 1984).

Blaha, F. C.

M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
[CrossRef]

Dollfus, A.

A. Dollfus, “The French Solar Photoelectric Polarimeter and its Applications for Solar Observations,” in Planets, Stars and Nebulae, T. Gehrels, Ed. (U. Arizona Press, Tucson, 1974), pp. 695–729.

Dunn, R.B.

T. E. Andersen, R.B. Dunn, O. Engvold, “LEST Design Study,” LEST Technical Report 7 (Institute of Theoretical Astrophysics, U. Oslo, 1984).

Engvold, O.

T. E. Andersen, R.B. Dunn, O. Engvold, “LEST Design Study,” LEST Technical Report 7 (Institute of Theoretical Astrophysics, U. Oslo, 1984).

Harvey, J. W.

Kemp, J. C.

Lampe, D. R.

M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
[CrossRef]

Livingston, W. C.

Mack, I. A.

M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
[CrossRef]

Rust, D. M.

D. M. Rust, “Some Design Considerations for a Satellite-borne Magnetograph,” in Measurements of Solar Vector Magnetic Fields, M. J. Hagyard, Ed., NASA Conf. Publ. 2374 (1985), pp. 141–152.

Slaughter, C.

Stenflo, J. O.

J. O. Stenflo, “Solar Magnetic and Velocity-Field Measurements: New Instrument Concepts,” Appl. Opt. 23, 1267 (1984).
[CrossRef] [PubMed]

J. O. Stenflo, “Polarimeter Package for LEST,” LEST Technical Report 4 (Institute of Theoretical Astrophysics, U. Oslo, 1984).

Trumbo, D.

White, M. H.

M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
[CrossRef]

Appl. Opt. (2)

IEEE J. Solid-State Circuits (1)

M. H. White, D. R. Lampe, F. C. Blaha, I. A. Mack, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels,” IEEE J. Solid-State Circuits SC-9, 1 (1974).
[CrossRef]

J. Opt. Soc. Am. (1)

Other (4)

D. M. Rust, “Some Design Considerations for a Satellite-borne Magnetograph,” in Measurements of Solar Vector Magnetic Fields, M. J. Hagyard, Ed., NASA Conf. Publ. 2374 (1985), pp. 141–152.

A. Dollfus, “The French Solar Photoelectric Polarimeter and its Applications for Solar Observations,” in Planets, Stars and Nebulae, T. Gehrels, Ed. (U. Arizona Press, Tucson, 1974), pp. 695–729.

J. O. Stenflo, “Polarimeter Package for LEST,” LEST Technical Report 4 (Institute of Theoretical Astrophysics, U. Oslo, 1984).

T. E. Andersen, R.B. Dunn, O. Engvold, “LEST Design Study,” LEST Technical Report 7 (Institute of Theoretical Astrophysics, U. Oslo, 1984).

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Figures (4)

Fig. 1
Fig. 1

Polarimeter scheme with piezoelastic modulators for the determination of the full Stokes vector. The four Stokes parameters (I, Q, U, and V) are modulated with high efficiency at four separate frequencies (dc, 2ω1, 2ω2, and ω1).

Fig. 2
Fig. 2

Operational diagram providing an overview of the optical demodulation system.

Fig. 3
Fig. 3

Solution for the beam splitter of Fig. 2 giving three linearly polarized output beams. By rotating the cubes in position angle, the relative intensities of the three beams may be adjusted. When α1 = 54.°7 and α2 = 9.°7, the three intensities are equal.

Fig. 4
Fig. 4

Scheme of an optical demodulator (one of the three units of Fig. 2). The piezoelastic modulator is modulated at frequency ω(δm = A sinωt). δr = 0 for demodulation of the signal at frequency 2ω (channels a and b for Stokes Q and U in Fig. 2), δr = π/2 for demodulation at frequency ω (channel c for Stokes V in Fig. 2). δps is switched between 0 and π. The two output beams of the Wollaston prism are imaged by the reimaging lens of Fig. 2 on two separate halves of a detector array (or, if so desired, on two separate detector arrays).

Equations (23)

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I = 1 2 ( I + x q Q cos 2 ω 1 t + x u U cos 2 ω 2 t + x υ V sin ω 1 t ) .
tan α 1 = ± 2 , α 2 α 1 = ± 45 ° ;
α 1 = 54 . ° 7 , α 2 = 9 . ° 7 .
δ m = A sin ω t .
δ = δ r + δ m + δ p s .
I 1 = 1 2 I ( 1 + cos δ ) , I 2 = 1 2 I ( 1 cos δ ) .
cos δ = ± cos δ m ,
cos δ = sin δ m
cos δ m J 0 ( A ) + 2 J 2 ( A ) cos 2 ω t , sin δ m 2 J 1 ( A ) sin ω t .
I 1 = 1 2 I [ 1 ± J 0 ( A ) ± 2 J 2 ( A ) cos 2 ω t ] , I 2 = 1 2 I [ 1 J 0 ( A ) 2 J 2 ( A ) cos 2 ω t ] .
I 1 = 1 4 I [ 1 ± J 0 ( A ) ] ± 1 2 x q J 2 ( A ) Q cos 2 2 ω 1 t
I 1 I 2 = ± 1 2 [ J 0 ( A ) I + x q J 2 ( A ) Q ] .
S 1 , 2 = e 1 , 2 I 1 , 2 .
S 1 S 2 = 1 4 { ( e 1 e 2 ) I ± ( e 1 + e 2 ) [ J 0 ( A ) I + x q J 2 ( A ) Q ] } ,
S Q = ( S 1 S 2 ) 0 ( S 1 S 2 ) π , S 1 = ( S 1 + S 2 ) 0 + ( S 1 + S 2 ) π ,
S Q = 1 2 ( e 1 + e 2 ) [ J 0 ( A ) I + x q J 2 ( A ) Q ] , S I = 1 2 ( e 1 + e 2 ) I .
S Q / S I = J 0 ( A ) + x q J 2 ( A ) Q / I .
S Q / S I = 0 . 43 x q Q / I .
I 1 = 1 2 I [ 1 2 J 1 ( A ) sin ω t ] , I 2 = 1 2 I [ 1 ± 2 J 1 ( A ) sin ω t ] .
I 1 = 1 4 [ I x υ J 1 ( A ) V ] , I 2 = 1 4 [ I ± x υ J 1 ( A ) V ] .
S 1 S 2 = 1 4 [ ( e 1 e 2 ) I ( e 1 + e 2 ) x υ J 1 ( A ) V ] , S 1 + S 2 = 1 4 [ ( e 1 + e 2 ) I ( e 1 e 2 ) x υ J 1 ( A ) V ] .
S V = 1 2 ( e 1 + e 2 ) x υ J 1 ( A ) V , S 1 = 1 2 ( e 1 + e 2 ) I .
S V / S I = 0 . 58 x υ V / I ,

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