Abstract

Through the aid of electronic light amplifiers, observers can view terrain on moonless nights with near-daylight acuity. This improvement in vision is obtained by using imaging sensors with larger lenses, greater quantum efficiencies, wider spectral responses, and larger photosensitive areas than those of the unaided eye. The observer’s improved resolving power using these sensors can be calculated in terms of a limiting resolution vs light level and an elemental signal-to-noise ratio at any operating point. The analysis facilitates the comparison of sensors on an equal basis and provides the system designer with more detailed sensor operating data. As examples, the limiting performance is calculated for the image orthicon and the secondary-electron conduction camera tube with and without cascaded image intensifiers. The calculated results are compared to those measured and are found to be in good agreement.

© 1969 Optical Society of America

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References

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  1. J. W. Coltman and A. E. Anderson, Proc. IRE 48, 858 (1960).
    [CrossRef]
  2. A. Rose, J. Opt. Soc. Am. 38, 196 (1948).
    [CrossRef] [PubMed]
  3. J. S. Parton and J. C. Moody, Image Intensifier Symposium, Ft. Belvoir, Virginia,NASA SP-2 (1961).
  4. J. W. Coltman, J. Opt. Soc. Am. 44, 468 (1954).
    [CrossRef]
  5. G. W. Goetze, Advances in Electronics and Electron Physics (Academic Press Inc., New York, 1966).
  6. P. Wargo, H. Hannum, and H. R. Day, IRE Trans. Electron Devices 7, 2 (1960).
  7. This response was obtained by scaling that of the Westinghouse WX 30677 intensifier output diameter from 25 to 40 mm, assuming that the principal resolution limit of the intensifier is due to the phosphor.
  8. B. H. Vine, J. Soc. Motion Picture Television Engrs. 70, 432 (1961).

1961 (2)

J. S. Parton and J. C. Moody, Image Intensifier Symposium, Ft. Belvoir, Virginia,NASA SP-2 (1961).

B. H. Vine, J. Soc. Motion Picture Television Engrs. 70, 432 (1961).

1960 (2)

P. Wargo, H. Hannum, and H. R. Day, IRE Trans. Electron Devices 7, 2 (1960).

J. W. Coltman and A. E. Anderson, Proc. IRE 48, 858 (1960).
[CrossRef]

1954 (1)

1948 (1)

Anderson, A. E.

J. W. Coltman and A. E. Anderson, Proc. IRE 48, 858 (1960).
[CrossRef]

Coltman, J. W.

J. W. Coltman and A. E. Anderson, Proc. IRE 48, 858 (1960).
[CrossRef]

J. W. Coltman, J. Opt. Soc. Am. 44, 468 (1954).
[CrossRef]

Day, H. R.

P. Wargo, H. Hannum, and H. R. Day, IRE Trans. Electron Devices 7, 2 (1960).

Goetze, G. W.

G. W. Goetze, Advances in Electronics and Electron Physics (Academic Press Inc., New York, 1966).

Hannum, H.

P. Wargo, H. Hannum, and H. R. Day, IRE Trans. Electron Devices 7, 2 (1960).

Moody, J. C.

J. S. Parton and J. C. Moody, Image Intensifier Symposium, Ft. Belvoir, Virginia,NASA SP-2 (1961).

Parton, J. S.

J. S. Parton and J. C. Moody, Image Intensifier Symposium, Ft. Belvoir, Virginia,NASA SP-2 (1961).

Rose, A.

Vine, B. H.

B. H. Vine, J. Soc. Motion Picture Television Engrs. 70, 432 (1961).

Wargo, P.

P. Wargo, H. Hannum, and H. R. Day, IRE Trans. Electron Devices 7, 2 (1960).

Image Intensifier Symposium, Ft. Belvoir, Virginia (1)

J. S. Parton and J. C. Moody, Image Intensifier Symposium, Ft. Belvoir, Virginia,NASA SP-2 (1961).

IRE Trans. Electron Devices (1)

P. Wargo, H. Hannum, and H. R. Day, IRE Trans. Electron Devices 7, 2 (1960).

J. Opt. Soc. Am. (2)

J. Soc. Motion Picture Television Engrs. (1)

B. H. Vine, J. Soc. Motion Picture Television Engrs. 70, 432 (1961).

Proc. IRE (1)

J. W. Coltman and A. E. Anderson, Proc. IRE 48, 858 (1960).
[CrossRef]

Other (2)

G. W. Goetze, Advances in Electronics and Electron Physics (Academic Press Inc., New York, 1966).

This response was obtained by scaling that of the Westinghouse WX 30677 intensifier output diameter from 25 to 40 mm, assuming that the principal resolution limit of the intensifier is due to the phosphor.

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Figures (13)

Fig. 1
Fig. 1

Photoelectron-limited resolving power as function of photocathode illuminance and input image contrast (luminous sensitivity 1.8 × 10−4 A/lm, area 7.58 × 10−4 m2 and image integration time 0.2 sec).

Fig. 2
Fig. 2

Display signal-to-noise ratio for an ideal photoelectron-noise-limited sensor vs photocathode illuminance (conditions as in Fig. 1).

Fig. 3
Fig. 3

A typical low-light-level television imaging system.

Fig. 4
Fig. 4

Peak-to-peak signal current Is, rms preamplifier noise Ipa rms photoelectron noise Ipc, and total rms noise In, vs photocathode illuminance for the WX 30654D SEC camera tube with and without a 40-mm intensifier for a 100% contrast image (SEC luminous efficiency 1.6 × 10−4 A/lm and photocathode area 7.58 × 10−4 m2).

Fig. 5
Fig. 5

Typical square-wave response for the WX 30654D SEC camera tube (curve A), sine-wave response for the 40-mm intensifier (curve B) and square-wave response for the composite ISEC (curve C).

Fig. 6
Fig. 6

Display signal-to-noise ratio for the WX 30654D SEC camera tube vs photocathode illuminance as a function of resolving power for a 30% input image contrast.

Fig. 7
Fig. 7

Limiting resolution vs photocathode illuminance for the SEC and ISEC camera at three values of input contrast (sensor parameters as in Fig. 4).

Fig. 8
Fig. 8

Peak-to-peak signal current Is, and rms noise currents for the 7.6 cm IO. The noise currents are the photoelectron noise Ipc, beam noise Ie, target noise It, first-dynode noise Id, and total noise In (photocathode luminous sensitivity 1.10−4 A/lm, area 7.58 × 10−4 m2 and input image contrast 100%).

Fig. 9
Fig. 9

Square-wave response of the IO operated above the knee of the signal current-photocathode illuminance curve (curve A), operated below the knee (curve B), and square-wave response of the IIO operated below the knee (curve C).

Fig. 10
Fig. 10

Limiting resolution vs photocathode illuminance for the IO as a function of input image contrast with optimum beam current (sensor parameters as in Fig. 8).

Fig. 11
Fig. 11

Peak-to-peak signal current Is and rms noise currents for the IIO. The noise currents are the photoelectron noise Ipc, the beam noise Ie, the preamp noise Ipa, and the total noise In (photocathode luminous efficiency 1.8 × 10−4 A/lm, area 7.58 × 10−4 m2, and input image contrast 100%).

Fig. 12
Fig. 12

Limiting resolution vs photocathode illuminance for the IIO with fixed and with optimum beam current as a function of input image contrast (sensor parameters as in Fig. 11).

Fig. 13
Fig. 13

Comparison of the limiting resolution of the IIO and the ISEC with equal input photocathodes and with fixed beam current.

Equations (19)

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SNR D = [ ( n ˙ max - n ˙ min ) t ] / [ ( n ˙ max + n ˙ min ) t ] 1 2 .
SNR D = ( i s max - i s min ) t 1 2 N [ 4 3 e ( i s max + i s min ) ] 1 2 .
C = ( i s max - i s min ) / ( i s max ) .
SNR D = C ( 2 - C ) 1 2 1 N [ i s max t 4 3 e ] 1 2 ,
SNR D = C ( 2 - C ) 1 2 1 N [ S A E max t 4 3 e ] 1 2 ,
N lim = 1 1.2 C ( 2 - C ) 1 2 [ S A E max t 4 3 e ] 1 2 .
SNR D = ( 0.75 t ) 1 2 N C i s max · R SQ ( N ) e 1 2 [ ( 2 - C ) i s max + 2 i n 1 + 2 i n 2 + ] 1 2 ,
SNR D = ( 0.75 t Δ f ) 1 2 N [ C i s max R S Q ( N ) / e v e h [ ( 2 - C ) e Δ f i s max / e v e h + 2 e Δ f i n 1 + 2 e Δ f i n 2 + ] 1 2 ] .
SNR D = [ ( 0.75 t Δ f ) 1 2 / N ] SNR V ,
SNR V = SNR VO · R SQ ( N ) .
SNR VO = ( C G T i s max / e v e h ) / [ ( 2 - C ) G T 2 e Δ f i s max e v e h + ( 2 - C ) G T e Δ f i s max e v e h + I PA 2 ] 1 2 ,
G T = ( e v e h I s max / S A E max ) .
SNR VO = ( C G T G P i s max / e v e h ) / [ ( 2 - C ) G T 2 G P 2 e Δ f i s max e v e h + 2 G P 2 G T 2 e Δ f i b e v e h + I PA 2 ] 1 2 ,
I S = C T M ( G T - 1 ) G M i s max / e v e h ;
I P C 2 = ( G T - 1 ) 2 G M 2 ( 2 - C ) T M e Δ f i s max / e v e h ;
I T 2 = G T G M 2 ( G T - 1 ) T M e Δ f i s max / e v e h ;
I e 2 = 2 G M 2 ( G T - 1 ) T M e Δ f i s max / m e v e h ;
I D 2 = 2 G M 1 G M 4 2 [ 1 - m m ] ( G T - 1 ) T M e Δ f i s max / e v e h ;
SNR VO = ( C G P ( G T - 1 ) G M T M i s max / e v e h ) / [ ( 2 - C ) G P 2 ( G T - 1 ) T M 2 e Δ f i s max e v e h + 2 G P ( G T - 1 ) G M 2 T M 2 e Δ f i s max m e v e h ] 1 2 .