Abstract

In scanning IR systems with cooled quantum detectors, the Narcissus signature usually has a limiting effect on the perceived image quality, and so it is important that it be assessed accurately before manufacture. We describe a new finite ray-tracing method in which each ray represents an equal amount of flux falling on the detector. Such methods require many rays; therefore a full error treatment is given that allows designers to estimate the necessary number of rays to obtain the required accuracy and also to calculate the standard deviation of the error in the final computed result.

© 1997 Optical Society of America

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References

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  1. J. M. Lloyd, Thermal Imaging Systems (Plenum, New York, 1975).
    [CrossRef]
  2. R. E. Fischer, “What’s so different about IR lens design?” in Lens Design, W. J. SmithKaiser Electro-Opt. Inc., eds., Proc. SPIECR 41, 117–139 (1992).
  3. A. S. Lau, “The Narcissus effect in infrared optical scanning systems,” in Stray Light Problems in Optical Systems, J. D. Lytle, H. E. Morrow, eds., Proc. SPIE107, 57–62 (1977).
    [CrossRef]
  4. E. Ford, D. Hasenauer, “Narcissus in current generation FLIR systems,” in Infrared Optical Design and Fabrication, R. Hartmann, W. J. Smith, eds., Proc. SPIECR 38, 95–119 (1991).
  5. J. W. Howard, I. R. Abel, “Narcissus: reflections on retroflections in thermal imaging systems,” Appl. Opt. 21, 3393–3397 (1982).
    [CrossRef] [PubMed]
  6. S. J. Dobson, A. Cox, K. Lu, “Calculation and optimization of Narcissus using paraxial ray tracing,” Appl. Opt. 35, 3059–3064 (1996).
    [CrossRef] [PubMed]
  7. J. L. Rayces, L. Lebich, “Exact ray-tracing computation of Narcissus equivalent temperature difference in scanning thermal imagers,” in Current Developments in Optical Design and Optical Engineering II, R. E. Fischer, W. J. Smith, eds., Proc. SPIE1752, 325–335 (1992).
    [CrossRef]

1996 (1)

1982 (1)

Abel, I. R.

Cox, A.

Dobson, S. J.

Fischer, R. E.

R. E. Fischer, “What’s so different about IR lens design?” in Lens Design, W. J. SmithKaiser Electro-Opt. Inc., eds., Proc. SPIECR 41, 117–139 (1992).

Ford, E.

E. Ford, D. Hasenauer, “Narcissus in current generation FLIR systems,” in Infrared Optical Design and Fabrication, R. Hartmann, W. J. Smith, eds., Proc. SPIECR 38, 95–119 (1991).

Hasenauer, D.

E. Ford, D. Hasenauer, “Narcissus in current generation FLIR systems,” in Infrared Optical Design and Fabrication, R. Hartmann, W. J. Smith, eds., Proc. SPIECR 38, 95–119 (1991).

Howard, J. W.

Lau, A. S.

A. S. Lau, “The Narcissus effect in infrared optical scanning systems,” in Stray Light Problems in Optical Systems, J. D. Lytle, H. E. Morrow, eds., Proc. SPIE107, 57–62 (1977).
[CrossRef]

Lebich, L.

J. L. Rayces, L. Lebich, “Exact ray-tracing computation of Narcissus equivalent temperature difference in scanning thermal imagers,” in Current Developments in Optical Design and Optical Engineering II, R. E. Fischer, W. J. Smith, eds., Proc. SPIE1752, 325–335 (1992).
[CrossRef]

Lloyd, J. M.

J. M. Lloyd, Thermal Imaging Systems (Plenum, New York, 1975).
[CrossRef]

Lu, K.

Rayces, J. L.

J. L. Rayces, L. Lebich, “Exact ray-tracing computation of Narcissus equivalent temperature difference in scanning thermal imagers,” in Current Developments in Optical Design and Optical Engineering II, R. E. Fischer, W. J. Smith, eds., Proc. SPIE1752, 325–335 (1992).
[CrossRef]

Appl. Opt. (2)

Other (5)

J. M. Lloyd, Thermal Imaging Systems (Plenum, New York, 1975).
[CrossRef]

R. E. Fischer, “What’s so different about IR lens design?” in Lens Design, W. J. SmithKaiser Electro-Opt. Inc., eds., Proc. SPIECR 41, 117–139 (1992).

A. S. Lau, “The Narcissus effect in infrared optical scanning systems,” in Stray Light Problems in Optical Systems, J. D. Lytle, H. E. Morrow, eds., Proc. SPIE107, 57–62 (1977).
[CrossRef]

E. Ford, D. Hasenauer, “Narcissus in current generation FLIR systems,” in Infrared Optical Design and Fabrication, R. Hartmann, W. J. Smith, eds., Proc. SPIECR 38, 95–119 (1991).

J. L. Rayces, L. Lebich, “Exact ray-tracing computation of Narcissus equivalent temperature difference in scanning thermal imagers,” in Current Developments in Optical Design and Optical Engineering II, R. E. Fischer, W. J. Smith, eds., Proc. SPIE1752, 325–335 (1992).
[CrossRef]

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Figures (6)

Fig. 1
Fig. 1

Ray pattern.

Fig. 2
Fig. 2

Distance between successive cones in the telescope exit pupil plane.

Fig. 3
Fig. 3

Error analysis for the on-axis case.

Fig. 4
Fig. 4

Error analysis for a semifield angle of 6°.

Fig. 5
Fig. 5

Error analysis for a semifield angle of30°.

Fig. 6
Fig. 6

Narcissus signature.

Tables (2)

Tables Icon

Table 1 8–12-µm Thermal Imager

Tables Icon

Table 2 Narcissus Signature

Equations (22)

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F = dsE T A E π F s 2 ,
F = dsE T sin 2   α ,
F I T = dsE T sin 2   α I - sin 2   α I - 1 = dsE T 2 I - 1 sin 2   α max I tot 2 ,
N tot = N 0 1 + 3 + 5 + 7 + + 2 I tot - 1 = N 0 I tot 2 .
F ray T = dsE T sin 2   α max N tot ,
Δ T θ = E T 0 - E T 1 E T 1 / T   j = 1 j = M   γ j N cold θ j N tot × sinefct ,
τ j = γ j t Dj 2 1 - γ j 2 ,
Δ T θ = λ 1 λ 2   E T 0 ,   λ - E T 1 ,   λ R λ d λ λ 1 λ 2   E T 1 ,   λ T   R λ d λ × j = 1 j = M   τ j N cold θ j t OD N tot × sinefct ,
Δ T θ = C   j = 1 j = M   τ j N cold θ j t OD N tot × sinefct ,
δ Δ T 0 = C   j = 1 j = M   τ j t od   2 I cold i δ I cold i I tot 2   sinefct = j = 1 j = M   2 δ I cold j I cold j   Δ T 0 j ,
p δ I cold = 1 when - 0.5 < δ I cold 0.5 0 when   δ I cold - 0.5 ;   δ I cold > 0.5 .
σ 2 Δ T 0 j = 2 2 σ 2 δ I cold j I cold j 2   Δ T 0 j 2 = Δ T 0 j 2 3 I cold j 2 ,
S Δ T 0 = j = 1 j = M   σ 2 Δ T 0 j 1 / 2 = j = 1 j = M   Δ T 0 3   I cold j 2 1 / 2 .
δ Δ T 0 = 2 C t OD I tot 2   sinefct   j = 1 j = M   τ j I cold j δ I cold j .
p I cold = 1 I tot when   0 I cold I tot 0 when   I cold > I tot .
I tot = C   j = 1 j = M   τ j 2 3 t OD δ Δ T 0 sinefct .
2 π IF Δ   sin   α F Δ   sin   α = 2 π I .
δ Δ T θ = C   j = 1 j = M   τ j δ N cold j t OD N 0 I tot 2   sinefct = j = 1 j = M   δ N cold j N cold j   Δ T θ j ,
e 1 0.5 .
δ N cold = j = 1 j = M b   e 1 i 2 1 / 2 = σ e 1   M b ,
S Δ T θ = j = 1 j = M   σ 2 Δ T θ j 1 / 2 = j = 1 j = M   M b Δ T θ 2 12 N cold 2 j 1 / 2 .
I tot = C 2   j = 1 j = M   τ j 2 6 π t OD 2 δ Δ T θ 2   sinefct 2 1 / 3 ,

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