Abstract

A Lyot–Öhman filter for imaging near the solar He i 1083-nm line is described. Fast and continuous spectral tunability is provided by nematic liquid crystals. This solid-state filter has a free spectral range of 2.35 nm and a spectral resolution of 0.135 nm at the operating wavelength of 1083 nm. A wide-fielded design was used for both static and electro-optic retarder elements, facilitating use in fast imaging systems. A first-light He i image of the Sun is presented.

© 1997 Optical Society of America

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References

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  1. L. Wallace, K. Hinkle, W. Livingston, “An atlas of the photospheric spectrum from 8900 to 13600 cm-1 (7350 to 11230 Å),” (National Solar Observatory, Tucson, Ariz., 1993).
  2. B. Lyot, “Le filtre monochromatique polarisant et ses applications en physique solaire,” Ann. Astrophys. 7, 31–79 (1944).
  3. Y. Öhman, “A new monochromator,” Nature (London) 141, 157–158 (1938).
  4. J. W. Evans, “The birefringent filter,” J. Opt. Soc. Am. 39, 229–242 (1949).
    [CrossRef]
  5. J. Hobbs, “Tunable liquid-crystal filter helps study stellar emission,” Laser Focus World 29, 29 (1993).
  6. P. Miller, “Tunable narrowband birefringent filters for astronomical imaging,” in Instrumentation in Astronomy VII, D. L. Crawford, ed., Proc. SPIE1235, 466–473 (1990).
    [CrossRef]
  7. K. Johnson, “Liquid crystal-on-silicon smart pixel spatial light modulators,” presented at the Rocky Mountain Optical Society Monthly Meeting, Boulder, Colo., 18 January 1996.
  8. X. Wang, J. Yao, “Transmitted and tuning characteristics of birefringent filters,” Appl. Opt. 32, 4505–4508 (1992).
    [CrossRef]
  9. B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
    [CrossRef]
  10. R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
    [CrossRef]
  11. A. Title, W. Rosenberg, “Tunable birefringent filters,” Opt. Eng. 20, 815–823 (1981).
    [CrossRef]
  12. J. Beckers, L. Dickson, R. Joyce, “Observing the sun with a fully tunable Lyot–Öhman filter,” Appl. Opt. 14, 2061–2066 (1975).
    [CrossRef] [PubMed]
  13. H. P. Jones, J. W. Harvey, V. Andretta, “Joint observations of the chromosphere, transition region, and corona from SOHO and NSO/Kitt Peak,” in Solar Dynamic Phenomena and Solar Wind Consequences, (European Space Agency, Paris, December1994), pp. 345–354.
  14. G. Kopp, “Tunable birefringent filters using liquid crystal variable retarders,” in Polarization Analysis and Measurement II, D. H. Goldstein, D. B. Chenault, eds., Proc. SPIE2265, 193–201 (1994).
    [CrossRef]
  15. Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
    [CrossRef]
  16. D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).
  17. D. F. Elmore, D. H. Hassler, K. Streander, “Chromospheric helium-I imaging photometer: a new instrument for high time cadence solar 1083 nm observations,” Appl. Opt. (to be published).

1995

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

1993

J. Hobbs, “Tunable liquid-crystal filter helps study stellar emission,” Laser Focus World 29, 29 (1993).

B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
[CrossRef]

1992

X. Wang, J. Yao, “Transmitted and tuning characteristics of birefringent filters,” Appl. Opt. 32, 4505–4508 (1992).
[CrossRef]

1991

Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
[CrossRef]

1981

A. Title, W. Rosenberg, “Tunable birefringent filters,” Opt. Eng. 20, 815–823 (1981).
[CrossRef]

1975

1949

1944

B. Lyot, “Le filtre monochromatique polarisant et ses applications en physique solaire,” Ann. Astrophys. 7, 31–79 (1944).

1938

Y. Öhman, “A new monochromator,” Nature (London) 141, 157–158 (1938).

Andretta, V.

H. P. Jones, J. W. Harvey, V. Andretta, “Joint observations of the chromosphere, transition region, and corona from SOHO and NSO/Kitt Peak,” in Solar Dynamic Phenomena and Solar Wind Consequences, (European Space Agency, Paris, December1994), pp. 345–354.

Beckers, J.

Burkepile, J.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Chovit, C.

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Dickson, L.

Elmore, D. F.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

D. F. Elmore, D. H. Hassler, K. Streander, “Chromospheric helium-I imaging photometer: a new instrument for high time cadence solar 1083 nm observations,” Appl. Opt. (to be published).

Evans, J. W.

Faust, J.

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Goedgebuer, J.

B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
[CrossRef]

Green, R.

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Hajek, P.

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Harvey, J. W.

H. P. Jones, J. W. Harvey, V. Andretta, “Joint observations of the chromosphere, transition region, and corona from SOHO and NSO/Kitt Peak,” in Solar Dynamic Phenomena and Solar Wind Consequences, (European Space Agency, Paris, December1994), pp. 345–354.

Hassler, D. H.

D. F. Elmore, D. H. Hassler, K. Streander, “Chromospheric helium-I imaging photometer: a new instrument for high time cadence solar 1083 nm observations,” Appl. Opt. (to be published).

Hassler, D. M.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Hinkle, K.

L. Wallace, K. Hinkle, W. Livingston, “An atlas of the photospheric spectrum from 8900 to 13600 cm-1 (7350 to 11230 Å),” (National Solar Observatory, Tucson, Ariz., 1993).

Hobbs, J.

J. Hobbs, “Tunable liquid-crystal filter helps study stellar emission,” Laser Focus World 29, 29 (1993).

Hundhausen, A. J.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Itoh, Y.

Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
[CrossRef]

Johnson, K.

K. Johnson, “Liquid crystal-on-silicon smart pixel spatial light modulators,” presented at the Rocky Mountain Optical Society Monthly Meeting, Boulder, Colo., 18 January 1996.

Jones, H. P.

H. P. Jones, J. W. Harvey, V. Andretta, “Joint observations of the chromosphere, transition region, and corona from SOHO and NSO/Kitt Peak,” in Solar Dynamic Phenomena and Solar Wind Consequences, (European Space Agency, Paris, December1994), pp. 345–354.

Joyce, R.

Kopp, G.

G. Kopp, “Tunable birefringent filters using liquid crystal variable retarders,” in Polarization Analysis and Measurement II, D. H. Goldstein, D. B. Chenault, eds., Proc. SPIE2265, 193–201 (1994).
[CrossRef]

Lecinski, A.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Livingston, W.

L. Wallace, K. Hinkle, W. Livingston, “An atlas of the photospheric spectrum from 8900 to 13600 cm-1 (7350 to 11230 Å),” (National Solar Observatory, Tucson, Ariz., 1993).

Lyot, B.

B. Lyot, “Le filtre monochromatique polarisant et ses applications en physique solaire,” Ann. Astrophys. 7, 31–79 (1944).

MacQueen, R. M.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Masuda, Y.

Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
[CrossRef]

Miller, P.

P. Miller, “Tunable narrowband birefringent filters for astronomical imaging,” in Instrumentation in Astronomy VII, D. L. Crawford, ed., Proc. SPIE1235, 466–473 (1990).
[CrossRef]

Novak, H.

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Öhman, Y.

Y. Öhman, “A new monochromator,” Nature (London) 141, 157–158 (1938).

Onokhov, A.

B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
[CrossRef]

Rosenberg, W.

A. Title, W. Rosenberg, “Tunable birefringent filters,” Opt. Eng. 20, 815–823 (1981).
[CrossRef]

Rottman, G. J.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Sarture, C.

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Seki, H.

Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
[CrossRef]

Stanger, A.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Streander, K.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

D. F. Elmore, D. H. Hassler, K. Streander, “Chromospheric helium-I imaging photometer: a new instrument for high time cadence solar 1083 nm observations,” Appl. Opt. (to be published).

Title, A.

A. Title, W. Rosenberg, “Tunable birefringent filters,” Opt. Eng. 20, 815–823 (1981).
[CrossRef]

Tomilin, M.

B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
[CrossRef]

Uchida, T.

Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
[CrossRef]

Wacogne, B.

B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
[CrossRef]

Wallace, L.

L. Wallace, K. Hinkle, W. Livingston, “An atlas of the photospheric spectrum from 8900 to 13600 cm-1 (7350 to 11230 Å),” (National Solar Observatory, Tucson, Ariz., 1993).

Wang, X.

X. Wang, J. Yao, “Transmitted and tuning characteristics of birefringent filters,” Appl. Opt. 32, 4505–4508 (1992).
[CrossRef]

Yao, J.

X. Wang, J. Yao, “Transmitted and tuning characteristics of birefringent filters,” Appl. Opt. 32, 4505–4508 (1992).
[CrossRef]

Am. Astron. Soc. Bull.

D. M. Hassler, D. F. Elmore, A. Lecinski, K. Streander, J. Burkepile, A. Stanger, A. J. Hundhausen, G. J. Rottman, R. M. MacQueen, “ACOS: HAO’s next generation coronal observing facility at Mauna Loa,” Am. Astron. Soc. Bull. 27, 970–971 (1995).

Ann. Astrophys.

B. Lyot, “Le filtre monochromatique polarisant et ses applications en physique solaire,” Ann. Astrophys. 7, 31–79 (1944).

Appl. Opt.

X. Wang, J. Yao, “Transmitted and tuning characteristics of birefringent filters,” Appl. Opt. 32, 4505–4508 (1992).
[CrossRef]

J. Beckers, L. Dickson, R. Joyce, “Observing the sun with a fully tunable Lyot–Öhman filter,” Appl. Opt. 14, 2061–2066 (1975).
[CrossRef] [PubMed]

IEEE J. Quantum Electron.

B. Wacogne, J. Goedgebuer, A. Onokhov, M. Tomilin, “Wavelength tuning of a semiconductor laser using nematic liquid crystals,” IEEE J. Quantum Electron. 29, 1015–1017 (1993).
[CrossRef]

J. Opt. Soc. Am.

Jpn. J. Appl. Phys. Lett.

Y. Itoh, H. Seki, T. Uchida, Y. Masuda, “A double-layer electrically controlled birefringence liquid crystal display with a wide viewing angle cone,” Jpn. J. Appl. Phys. Lett. 30, L1296–L1299 (1991).
[CrossRef]

Laser Focus World

J. Hobbs, “Tunable liquid-crystal filter helps study stellar emission,” Laser Focus World 29, 29 (1993).

Nature (London)

Y. Öhman, “A new monochromator,” Nature (London) 141, 157–158 (1938).

Opt. Eng.

A. Title, W. Rosenberg, “Tunable birefringent filters,” Opt. Eng. 20, 815–823 (1981).
[CrossRef]

Opt. Photon. News

R. Green, C. Sarture, C. Chovit, J. Faust, P. Hajek, H. Novak, “AVIRIS: a new approach to earth remote sensing,” Opt. Photon. News 6, 30–33 (1995).
[CrossRef]

Other

P. Miller, “Tunable narrowband birefringent filters for astronomical imaging,” in Instrumentation in Astronomy VII, D. L. Crawford, ed., Proc. SPIE1235, 466–473 (1990).
[CrossRef]

K. Johnson, “Liquid crystal-on-silicon smart pixel spatial light modulators,” presented at the Rocky Mountain Optical Society Monthly Meeting, Boulder, Colo., 18 January 1996.

H. P. Jones, J. W. Harvey, V. Andretta, “Joint observations of the chromosphere, transition region, and corona from SOHO and NSO/Kitt Peak,” in Solar Dynamic Phenomena and Solar Wind Consequences, (European Space Agency, Paris, December1994), pp. 345–354.

G. Kopp, “Tunable birefringent filters using liquid crystal variable retarders,” in Polarization Analysis and Measurement II, D. H. Goldstein, D. B. Chenault, eds., Proc. SPIE2265, 193–201 (1994).
[CrossRef]

L. Wallace, K. Hinkle, W. Livingston, “An atlas of the photospheric spectrum from 8900 to 13600 cm-1 (7350 to 11230 Å),” (National Solar Observatory, Tucson, Ariz., 1993).

D. F. Elmore, D. H. Hassler, K. Streander, “Chromospheric helium-I imaging photometer: a new instrument for high time cadence solar 1083 nm observations,” Appl. Opt. (to be published).

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Figures (6)

Fig. 1
Fig. 1

Non-normalized solar spectrum near 1083 nm, as observed through the Earth’s atmosphere. The He i line is a useful diagnostic of solar activity.

Fig. 2
Fig. 2

Optical configuration of the He i filter. Octagonal optics are used for ease of alignment. Each of the four stages contains a wide-fielded liquid-crystal cell. The three narrowest band stages have wide-fielded calcite elements. The elements are contacted by using an index-matched optical coupling compound in a temperature-stabilized housing (not shown).

Fig. 3
Fig. 3

Cross section of the dual-cell wide-fielded liquid crystals used in the filter. As voltage to a liquid-crystal cell increases, the elongated, birefringent molecules tip to be more orthogonal to the substrate surface. This tip changes the effective retardance of the cell for light traversing at normal incidence to the cell substrates, and it is the operating principle behind a liquid-crystal variable retarder. Although these are true zero-order retarders, at partial voltages a single liquid-crystal cell behaves asymmetrically to nonnormal incident light. In the dual-cell configuration shown, the off-axis effects in the second cell largely compensate for those of the first, greatly increasing the retarder’s field of view. The two light beams depicted thus have nearly identical effective retardances.

Fig. 4
Fig. 4

Filter transmission profile of a He i filter tuned to 1083.03 nm, using a continuum laboratory light source. The filter has a spectral resolution of 0.135 nm and a FSR of 2.35 nm. Transmission of the filter is 12.7% for unpolarized incident light. In use, transmission peaks outside the filter’s spectral range are blocked by a prefilter.

Fig. 5
Fig. 5

Transmission profiles at different angles of incidence show the effectiveness of wide fielding in the filter. The filter’s wide-fielded design minimizes the effects of different incidence angles, whether caused by an uncollimated beam or a non-normal alignment in a beam. As an incoming f/12 beam varies from normal incidence, the predominate effect in the filter transmission profile is a slight lowering of the main peaks and an increase in the sidelobes at ±(FSR/2) from the main peaks. These sidelobes are normally blocked by the spectrally broadest stage. The calcite retarder in this stage is not wide fielded, and at non-normal angles of incidence the spectral profile of the stage shifts considerably, allowing transmission of sidelobes it normally blocks. The remaining calcite elements and the liquid crystals are very insensitive to angle of incidence, as evidenced by the stability of the main peak positions and by the other small sidelobe intensities.

Fig. 6
Fig. 6

First-light solar disk image taken at He i on 31 May 1995 from the High Altitude Observatory. Solar north is shown. As these observations were made during a period of very low solar activity, only a few active regions are apparent. The dark spot north of disk center is from a magnetically active region. The small bright region near the northern pole indicates a coronal hole; a larger and more extended one is evident near the northern pole, extending toward the western (right-hand) limb. This image is the combination of two 30-ms exposures, one at the He i line and one in nearby continuum. (Photo courtesy of Alice Lecinski, High Altitude Observatory).

Tables (1)

Tables Icon

Table 1 Tuning Times of the Filter

Metrics