Abstract

We report the operation of an imaging Nd:YAG microchip-laser synthetic-aperture radar, with which we imaged two-dimensional (2-D) models of military targets. The images obtained showed spatial resolution significantly better than the diffraction limit of the real aperture in the along-track dimension. The signal processing is described, and the measurement sensitivity is both predicted and verified. In addition, 2-D images with high resolution in both dimensions were generated by using an asymmetric aperture to match the along-track synthetic-aperture resolution with the across-track diffraction-limited resolution.

© 1995 Optical Society of America

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References

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  1. R. O. Harger, Synthetic Aperture Radar Systems: Theory and Design (Academic, New York, 1970).
  2. J. C. Curlander, R. N. McDonough, Synthetic Aperture Radar: Systems and Signal Processing (Wiley, New York, 1991).
  3. T. S. Lewis, H. S. Hutchins, “A synthetic aperture at 10.6 microns,” Proc. IEEE 58, 1781–1782 (1970).
    [CrossRef]
  4. C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).
  5. S. Marcus, B. D. Colella, T. J. Green, “Solid-state laser synthetic aperture radar,” Appl. Opt. 33, 960–964 (1994).
    [CrossRef] [PubMed]
  6. J. J. Zayhowski, “Microchip lasers,” Lincoln Lab. J. 3, 427–446 (1990).
  7. D. Park, J. Shapiro, “Performance analysis of optical synthetic aperture radars,” in Laser Radar III, R. J. Becherer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.999, 100–116 (1988).
  8. M. Skolnik, Radar Handbook (McGraw-Hill, New York, 1990).
  9. A. V. Oppenheim, R. W. Schafer, Discrete-Time Signal Processing (Prentice-Hall, Englewood Cliffs, N.J., 1989).
  10. H. L. van Trees, Detection, Estimation and Modulation Theory, Part I (Wiley, New York, 1968).

1994

1990

J. J. Zayhowski, “Microchip lasers,” Lincoln Lab. J. 3, 427–446 (1990).

1970

T. S. Lewis, H. S. Hutchins, “A synthetic aperture at 10.6 microns,” Proc. IEEE 58, 1781–1782 (1970).
[CrossRef]

Abshier, J. O.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Accetta, J. S.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Aleksof, C. C.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Colella, B. D.

Curlander, J. C.

J. C. Curlander, R. N. McDonough, Synthetic Aperture Radar: Systems and Signal Processing (Wiley, New York, 1991).

Fee, M.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Green, T. J.

Harger, R. O.

R. O. Harger, Synthetic Aperture Radar Systems: Theory and Design (Academic, New York, 1970).

Hutchins, H. S.

T. S. Lewis, H. S. Hutchins, “A synthetic aperture at 10.6 microns,” Proc. IEEE 58, 1781–1782 (1970).
[CrossRef]

Klossler, A.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Lewis, T. S.

T. S. Lewis, H. S. Hutchins, “A synthetic aperture at 10.6 microns,” Proc. IEEE 58, 1781–1782 (1970).
[CrossRef]

Majewski, R. M.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Marcus, S.

McDonough, R. N.

J. C. Curlander, R. N. McDonough, Synthetic Aperture Radar: Systems and Signal Processing (Wiley, New York, 1991).

Oppenheim, A. V.

A. V. Oppenheim, R. W. Schafer, Discrete-Time Signal Processing (Prentice-Hall, Englewood Cliffs, N.J., 1989).

Park, D.

D. Park, J. Shapiro, “Performance analysis of optical synthetic aperture radars,” in Laser Radar III, R. J. Becherer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.999, 100–116 (1988).

Peterson, L. M.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Schafer, R. W.

A. V. Oppenheim, R. W. Schafer, Discrete-Time Signal Processing (Prentice-Hall, Englewood Cliffs, N.J., 1989).

Schroeder, K. S.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

Shapiro, J.

D. Park, J. Shapiro, “Performance analysis of optical synthetic aperture radars,” in Laser Radar III, R. J. Becherer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.999, 100–116 (1988).

Skolnik, M.

M. Skolnik, Radar Handbook (McGraw-Hill, New York, 1990).

Tai, A. M.

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

van Trees, H. L.

H. L. van Trees, Detection, Estimation and Modulation Theory, Part I (Wiley, New York, 1968).

Zayhowski, J. J.

J. J. Zayhowski, “Microchip lasers,” Lincoln Lab. J. 3, 427–446 (1990).

Appl. Opt.

Lincoln Lab. J.

J. J. Zayhowski, “Microchip lasers,” Lincoln Lab. J. 3, 427–446 (1990).

Proc. IEEE

T. S. Lewis, H. S. Hutchins, “A synthetic aperture at 10.6 microns,” Proc. IEEE 58, 1781–1782 (1970).
[CrossRef]

Other

C. C. Aleksof, J. S. Accetta, L. M. Peterson, A. M. Tai, A. Klossler, K. S. Schroeder, R. M. Majewski, J. O. Abshier, M. Fee, “Synthetic aperture imaging with a pulsed CO2 TEA laser,” in Laser Radar II, R. J. Becherer, R. C. Harney, eds., Proc. Soc. Photo-Opt. Instrum. Eng.783, 29–40 (1987).

R. O. Harger, Synthetic Aperture Radar Systems: Theory and Design (Academic, New York, 1970).

J. C. Curlander, R. N. McDonough, Synthetic Aperture Radar: Systems and Signal Processing (Wiley, New York, 1991).

D. Park, J. Shapiro, “Performance analysis of optical synthetic aperture radars,” in Laser Radar III, R. J. Becherer, ed., Proc. Soc. Photo-Opt. Instrum. Eng.999, 100–116 (1988).

M. Skolnik, Radar Handbook (McGraw-Hill, New York, 1990).

A. V. Oppenheim, R. W. Schafer, Discrete-Time Signal Processing (Prentice-Hall, Englewood Cliffs, N.J., 1989).

H. L. van Trees, Detection, Estimation and Modulation Theory, Part I (Wiley, New York, 1968).

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Figures (16)

Fig. 1
Fig. 1

Downlooking SAR measurement.

Fig. 2
Fig. 2

Block diagram of a heterodyne laser radar system. T/R, transmit–receive; BPF, bandpass filter; A/D, analog-to-digital.

Fig. 3
Fig. 3

Experimental configuration for microchip-laser-imaging SAR demonstration.

Fig. 4
Fig. 4

Received signal spectrum for all scans over a single target.

Fig. 5
Fig. 5

Peak-detected center-frequency measurements, their associated weights, and the computed center frequency that results from using a weighted least-squares-derived squint-angle estimate.

Fig. 6
Fig. 6

Correspondence between the spectrum of a single scan and the matched-filter envelope predicted by theory.

Fig. 7
Fig. 7

Diffraction-limited result arising from a single scan over the target for λ = 1.06 μm, L = 2.5 m, and D x = 0.25 mm.

Fig. 8
Fig. 8

SAR-processed result from a single scan over the target for λ = 1.06 μm, L = 2.5 m, and D x = 0.25 mm.

Fig. 9
Fig. 9

Diffraction-limited image of target model with the along-track dimension in the horizontal direction.

Fig. 10
Fig. 10

SAR-processed image of target model with the along-track dimension in the horizontal direction.

Fig. 11
Fig. 11

Diffraction-limited image of target model with the along-track dimension in the vertical direction.

Fig. 12
Fig. 12

SAR-processed image of target model with the along-track dimension in the vertical direction.

Fig. 13
Fig. 13

Diffraction-limited image of target model with the along-track dimension in the horizontal direction and using an asymmetric aperture.

Fig. 14
Fig. 14

SAR-processed image of target model with the along-track dimension in the horizontal direction and using an asymmetric aperture.

Fig. 15
Fig. 15

Diffraction-limited image of target model with the along-track dimension in the vertical direction and using an asymmetric aperture.

Fig. 16
Fig. 16

SAR-processed image of target model with the along-track dimension in the vertical direction and using an asymmetric aperture.

Equations (22)

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T = 2 λ L D x v .
ν D ( t , x ) = 2 v 2 λ L ( x v - t ) + ν IF ,             for | x v - t | T / 2 ,
ν IF = - 2 v λ sin θ - 2 v λ θ ,
h ( t ) = 1 T exp [ j 2 π ( ν ˙ D 2 t + ν IF ) t ] ,             for t T / 2 ,
ν ˙ D = - 2 v 2 λ L
W D ν ˙ D T 4 v D x .
CNR = η P T h ν W D ρ A R π L 2 exp ( - 2 α L ) ,
x SAR D x 2 .
r ( m ) = R 0 + m Δ R ,             0 m M - 1 ,
v ( m ) = 2 π T r r ( m ) .
h ˜ m , n = { T s T ( m ) exp { j 2 π [ ν ˙ D ( m ) 2 n T s + ν IF ( m ) ] n T s } ,             n T ( m ) 2 T s , 0 ,             - N / 2 n < - T ( m ) 2 T s , 0 ,             T ( m ) 2 T s n < N / 2.
H ˜ m , k n = - N / 2 N / 2 - 1 h m , n exp ( - j 2 π n N k ) ,             for 0 m < M ,             0 k < N .
y m , n 1 N k = 0 N - 1 H ˜ m , k X m , k exp ( j 2 π k N n ) ,             for 0 m < M ,             0 n < N ,
X m , k n = 0 N - 1 x m , n exp ( - j 2 π n N k ) ,             for 0 m < M ,             0 k < N .
z m , n y m , n 2 ,             for 0 m < M ,             0 n < N .
ν ^ IF ( m ) = 1 N T s arg max k n = - X m , k - n H n ,             for 0 k < N / 2 ,             0 m M - 1 ,
ν IF ( m ) = - 4 π λ T r ( R 0 + m Δ R ) θ ,             0 m M - 1.
y [ ν ^ IF ( 0 ) , ν IF ( 1 ) , , ν ^ IF ( M - 1 ) ] T ,
c - 4 π λ T r [ R 0 , R 0 + Δ r , R 0 + 2 Δ r , , R 0 + ( M - 1 ) Δ r ] T ,
y = c θ + n ,
θ ^ w = ( c T wc ) - 1 c T wy ,
w ( m ) = ( max k n = - X m , k - n H n ) 2 ,             for 0 k < N / 2 ,             0 m M - 1.

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