Abstract

We describe a dual-mirror wide angle optical design, which removes the radial distortion associated with traditional all-sky optics for a chosen altitude. The wide angle mirror system provides a transform of the sky, for a selected altitude, as if the viewer is situated at the center of the Earth. Other advantages of the system include (1) real time achromatic transform, (2) higher optical gain compared to pure lens systems, (3) a quasi-telecentric optic capable of taking narrowband interference filters without modification, and (4) a uniform sky spatial resolution everywhere on the detector. Disadvantages include (1) cost of manufacture and (2) focusing issues, especially near the horizon.

© 2009 Optical Society of America

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References

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  1. C. Lance and R. H. Eather, “HAARP Imager,” Report ADA- 277469 (Defense Technical Information Center, 1993).
  2. C. Stormer, The Polar Aurora (Oxford University, 1955).
  3. M. J. Kosch, M. W. J. Scourfield, and E. Nielsen, “A self-consistent explanation for a plasma flow vortex associated with the brightening of an auroral arc,” J. Geophys. Res. 103, 29383-29391 (1998).
    [CrossRef]
  4. F. J. Garcia, M. J. Taylor, and M. C. Kelley, “Two-dimensional spectral analysis of mesospheric airglow image data,” Appl. Opt. 36, 7374-7385 (1997).
    [CrossRef]
  5. M. J. Kosch, T. Hagfors, and E. Nielsen, “A new Digital All-Sky Imager experiment for optical auroral studies in conjunction with the STARE coherent radar system,” Rev. Sci. Instrum. 69, 578-584 (1998).
    [CrossRef]
  6. N. Radic and Z. Andreic, “Aspheric mirror with constant angular magnification,” Appl. Opt. 31, 5915-5917(1992).
    [CrossRef] [PubMed]
  7. Z. Andreic and N. Radic, “Aspheric mirror with constant angular magnification II,” Appl. Opt. 33, 4179-4183(1994).
    [CrossRef] [PubMed]
  8. G. Hough, “Evolution of periodicity and scale length in auroral dynamics,” Ph.D. thesis (University of Natal, 1994).
  9. G. Hough and M. W. J. Scourfield, “WAND auroral imager for SANAE,” S. Afr. J. Antarct. Res. 21, 113 (1991).
  10. Z. Andreic and N. Radic, “All-sky camera with a concave mirror,” Appl. Opt. 35, 149-153 (1996).
    [CrossRef] [PubMed]
  11. A. R. Greenleaf, Photographic Optics (MacMillan, 1950).

1998 (2)

M. J. Kosch, M. W. J. Scourfield, and E. Nielsen, “A self-consistent explanation for a plasma flow vortex associated with the brightening of an auroral arc,” J. Geophys. Res. 103, 29383-29391 (1998).
[CrossRef]

M. J. Kosch, T. Hagfors, and E. Nielsen, “A new Digital All-Sky Imager experiment for optical auroral studies in conjunction with the STARE coherent radar system,” Rev. Sci. Instrum. 69, 578-584 (1998).
[CrossRef]

1997 (1)

1996 (1)

1994 (1)

1992 (1)

1991 (1)

G. Hough and M. W. J. Scourfield, “WAND auroral imager for SANAE,” S. Afr. J. Antarct. Res. 21, 113 (1991).

Andreic, Z.

Eather, R. H.

C. Lance and R. H. Eather, “HAARP Imager,” Report ADA- 277469 (Defense Technical Information Center, 1993).

Garcia, F. J.

Greenleaf, A. R.

A. R. Greenleaf, Photographic Optics (MacMillan, 1950).

Hagfors, T.

M. J. Kosch, T. Hagfors, and E. Nielsen, “A new Digital All-Sky Imager experiment for optical auroral studies in conjunction with the STARE coherent radar system,” Rev. Sci. Instrum. 69, 578-584 (1998).
[CrossRef]

Hough, G.

G. Hough and M. W. J. Scourfield, “WAND auroral imager for SANAE,” S. Afr. J. Antarct. Res. 21, 113 (1991).

G. Hough, “Evolution of periodicity and scale length in auroral dynamics,” Ph.D. thesis (University of Natal, 1994).

Kelley, M. C.

Kosch, M. J.

M. J. Kosch, T. Hagfors, and E. Nielsen, “A new Digital All-Sky Imager experiment for optical auroral studies in conjunction with the STARE coherent radar system,” Rev. Sci. Instrum. 69, 578-584 (1998).
[CrossRef]

M. J. Kosch, M. W. J. Scourfield, and E. Nielsen, “A self-consistent explanation for a plasma flow vortex associated with the brightening of an auroral arc,” J. Geophys. Res. 103, 29383-29391 (1998).
[CrossRef]

Lance, C.

C. Lance and R. H. Eather, “HAARP Imager,” Report ADA- 277469 (Defense Technical Information Center, 1993).

Nielsen, E.

M. J. Kosch, M. W. J. Scourfield, and E. Nielsen, “A self-consistent explanation for a plasma flow vortex associated with the brightening of an auroral arc,” J. Geophys. Res. 103, 29383-29391 (1998).
[CrossRef]

M. J. Kosch, T. Hagfors, and E. Nielsen, “A new Digital All-Sky Imager experiment for optical auroral studies in conjunction with the STARE coherent radar system,” Rev. Sci. Instrum. 69, 578-584 (1998).
[CrossRef]

Radic, N.

Scourfield, M. W. J.

M. J. Kosch, M. W. J. Scourfield, and E. Nielsen, “A self-consistent explanation for a plasma flow vortex associated with the brightening of an auroral arc,” J. Geophys. Res. 103, 29383-29391 (1998).
[CrossRef]

G. Hough and M. W. J. Scourfield, “WAND auroral imager for SANAE,” S. Afr. J. Antarct. Res. 21, 113 (1991).

Stormer, C.

C. Stormer, The Polar Aurora (Oxford University, 1955).

Taylor, M. J.

Appl. Opt. (4)

J. Geophys. Res. (1)

M. J. Kosch, M. W. J. Scourfield, and E. Nielsen, “A self-consistent explanation for a plasma flow vortex associated with the brightening of an auroral arc,” J. Geophys. Res. 103, 29383-29391 (1998).
[CrossRef]

Rev. Sci. Instrum. (1)

M. J. Kosch, T. Hagfors, and E. Nielsen, “A new Digital All-Sky Imager experiment for optical auroral studies in conjunction with the STARE coherent radar system,” Rev. Sci. Instrum. 69, 578-584 (1998).
[CrossRef]

S. Afr. J. Antarct. Res. (1)

G. Hough and M. W. J. Scourfield, “WAND auroral imager for SANAE,” S. Afr. J. Antarct. Res. 21, 113 (1991).

Other (4)

G. Hough, “Evolution of periodicity and scale length in auroral dynamics,” Ph.D. thesis (University of Natal, 1994).

C. Lance and R. H. Eather, “HAARP Imager,” Report ADA- 277469 (Defense Technical Information Center, 1993).

C. Stormer, The Polar Aurora (Oxford University, 1955).

A. R. Greenleaf, Photographic Optics (MacMillan, 1950).

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Figures (4)

Fig. 1
Fig. 1

Geographic grid covering 67.6 ° 72.6 ° N, 13.5 ° 26.0 ° E, in steps of 0.1 ° latitude and 0.25 ° longitude, at an assumed altitude of 100 km as seen through an all-sky lens from 69.35 ° N, 20.36 ° E in geographic coordinates. The data grid corresponds to approximately 10 × 10 km trapezoids.

Fig. 2
Fig. 2

Geometry showing the transform implemented, where r is the radius of the Earth, h is the transform altitude, θ is the local zenith angle, and ε is the angle subtended at the center of the Earth.

Fig. 3
Fig. 3

(a) Schematic of a traditional all-sky mirror lens (top) and the resulting image (bottom). The black disk represents the image area that is blocked by either the detector or a secondary mirror. The image radius linear in θ (or ε) is shown. (b) Schematic of a modified traditional all-sky mirror lens (top) and the resulting image (bottom). The maximum height of the primary mirror is not in the center but forms a doughnut. The black disk contains no useful information in the image. The image radius linear in θ (or ε) is shown.

Fig. 4
Fig. 4

(a) Schematic of the wide angle mirror system as implemented (left) and the resulting image (right). The primary mirror (bottom) performs the transform. The secondary mirror ensures that the local zenith is in the middle of the image with no cosmetic artifacts. The image radius linear in ε (or θ) is shown. The scale is arbitrary, but inches give realistic dimensions. (b) Schematic of the wide angle mirror system as implemented, showing the primary and secondary mirrors as well as the locus of radial and azimuthal focus of the primary mirror for objects at infinity. The scale is arbitrary, but inches give realistic dimensions.

Tables (1)

Tables Icon

Table 1 Parameters Associated with the WAMS Design Shown in Fig. 4 for a Transform Altitude of 100 km a

Equations (5)

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tan ( θ ) = ( h + r ) sin ( ε ) ( h + r ) cos ( ε ) r .
FOV = 2 tan 1 ( d 2 f ) ,
λ ε λ 0 = 1 ( N m N f ) 2 sin 2 ( ε ) ,
D n = c F s ( s f ) f 2 + c F ( s f ) ,
D f = c F s ( s f ) f 2 c F ( s f ) ,

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