Abstract

The area and contour of a stimulus have been indicated experimentally as factors in its visibility. In order to evaluate the role of such factors in radar presentation, an experiment was conducted to determine the effect upon visibility of changes in the size and shape of a radar pip. A wide range of beam widths (which determine the angular dimension of the pip) and pulse lengths (which determine its radial dimension) was investigated at each of three test field brightnesses. Resuits show that visibility, on a decibel scale, is a linear function of the logarithm of beam width at each of the three brightness levels used. For the dim background visibility is also a linear function of the logarithm of pulse length. For the brighter backgrounds, on the other hand, visibility is shown to be a curvilinear function of the logarithm of pulse length. It is suggested that the reason for the difference between an increase in beam width and an increase in pulse length lies in the time factor. Doubling the beam width, for example, results in a greater increase in the time during which the pip is exposed to the eye than does a corresponding increase in the pulse length.

© 1949 Optical Society of America

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References

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  1. S. B. Williams and N. R. Bartlett, “Visibility on cathoderay tube screens: Problems and methods,” J. Psych. 25, 401 (1948).
    [CrossRef]
  2. Lamar, Hecht, Shlaer, and Hendley, “Size, shape and contrast in detection of targets by daylight vision. I. Data and analytical description,” J. Opt. Soc. Am. 37, 531 (1947).
    [CrossRef] [PubMed]
  3. R. H. Brown, “Spatial effects in human visual resolution,” J. Gen. Psychol. 35, 77 (1946).
    [CrossRef] [PubMed]
  4. R. H. Brown and J. I. Niven, “The relation between the foveal intensity threshold and the length of an illuminated slit,” J. Exper. Psych. 34, 464 (1944);J. I. Niven and R. H. Brown, “Visual resolution as a function of intensity and exposure time in the human fovea,” J. Opt. Soc. Am. 34, 738 (1944).
    [CrossRef]
  5. A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen seen at different intervals after excitation,” J. Opt. Soc. Am. 38, 329 (1948).
    [CrossRef] [PubMed]
  6. R. G. Hopkinson, “Visibility of cathode-ray-tube traces in radar displays,” J. Inst. Elec. Eng. 93, 795 (1946).
  7. R. Payne-Scott, “The visibility of small echoes on radar PPI displays,” Proc. Inst. Radio Eng. 36, 180 (1948).
  8. Williams, Bartlett, and King, “Visibility on cathode-ray tube screens: Screen brightness,” J. Psych. 25, 455 (1948).
    [CrossRef]
  9. A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen exposed for different intervals,” (Manuscript in preparation).

1948 (4)

S. B. Williams and N. R. Bartlett, “Visibility on cathoderay tube screens: Problems and methods,” J. Psych. 25, 401 (1948).
[CrossRef]

A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen seen at different intervals after excitation,” J. Opt. Soc. Am. 38, 329 (1948).
[CrossRef] [PubMed]

R. Payne-Scott, “The visibility of small echoes on radar PPI displays,” Proc. Inst. Radio Eng. 36, 180 (1948).

Williams, Bartlett, and King, “Visibility on cathode-ray tube screens: Screen brightness,” J. Psych. 25, 455 (1948).
[CrossRef]

1947 (1)

1946 (2)

R. H. Brown, “Spatial effects in human visual resolution,” J. Gen. Psychol. 35, 77 (1946).
[CrossRef] [PubMed]

R. G. Hopkinson, “Visibility of cathode-ray-tube traces in radar displays,” J. Inst. Elec. Eng. 93, 795 (1946).

1944 (1)

R. H. Brown and J. I. Niven, “The relation between the foveal intensity threshold and the length of an illuminated slit,” J. Exper. Psych. 34, 464 (1944);J. I. Niven and R. H. Brown, “Visual resolution as a function of intensity and exposure time in the human fovea,” J. Opt. Soc. Am. 34, 738 (1944).
[CrossRef]

Bartlett,

Williams, Bartlett, and King, “Visibility on cathode-ray tube screens: Screen brightness,” J. Psych. 25, 455 (1948).
[CrossRef]

Bartlett, N. R.

S. B. Williams and N. R. Bartlett, “Visibility on cathoderay tube screens: Problems and methods,” J. Psych. 25, 401 (1948).
[CrossRef]

A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen seen at different intervals after excitation,” J. Opt. Soc. Am. 38, 329 (1948).
[CrossRef] [PubMed]

A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen exposed for different intervals,” (Manuscript in preparation).

Brown, R. H.

R. H. Brown, “Spatial effects in human visual resolution,” J. Gen. Psychol. 35, 77 (1946).
[CrossRef] [PubMed]

R. H. Brown and J. I. Niven, “The relation between the foveal intensity threshold and the length of an illuminated slit,” J. Exper. Psych. 34, 464 (1944);J. I. Niven and R. H. Brown, “Visual resolution as a function of intensity and exposure time in the human fovea,” J. Opt. Soc. Am. 34, 738 (1944).
[CrossRef]

Hecht,

Hendley,

Hopkinson, R. G.

R. G. Hopkinson, “Visibility of cathode-ray-tube traces in radar displays,” J. Inst. Elec. Eng. 93, 795 (1946).

King,

Williams, Bartlett, and King, “Visibility on cathode-ray tube screens: Screen brightness,” J. Psych. 25, 455 (1948).
[CrossRef]

Lamar,

Niven, J. I.

R. H. Brown and J. I. Niven, “The relation between the foveal intensity threshold and the length of an illuminated slit,” J. Exper. Psych. 34, 464 (1944);J. I. Niven and R. H. Brown, “Visual resolution as a function of intensity and exposure time in the human fovea,” J. Opt. Soc. Am. 34, 738 (1944).
[CrossRef]

Payne-Scott, R.

R. Payne-Scott, “The visibility of small echoes on radar PPI displays,” Proc. Inst. Radio Eng. 36, 180 (1948).

Shlaer,

Sweet, A. L.

A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen seen at different intervals after excitation,” J. Opt. Soc. Am. 38, 329 (1948).
[CrossRef] [PubMed]

A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen exposed for different intervals,” (Manuscript in preparation).

Williams,

Williams, Bartlett, and King, “Visibility on cathode-ray tube screens: Screen brightness,” J. Psych. 25, 455 (1948).
[CrossRef]

Williams, S. B.

S. B. Williams and N. R. Bartlett, “Visibility on cathoderay tube screens: Problems and methods,” J. Psych. 25, 401 (1948).
[CrossRef]

J. Exper. Psych. (1)

R. H. Brown and J. I. Niven, “The relation between the foveal intensity threshold and the length of an illuminated slit,” J. Exper. Psych. 34, 464 (1944);J. I. Niven and R. H. Brown, “Visual resolution as a function of intensity and exposure time in the human fovea,” J. Opt. Soc. Am. 34, 738 (1944).
[CrossRef]

J. Gen. Psychol. (1)

R. H. Brown, “Spatial effects in human visual resolution,” J. Gen. Psychol. 35, 77 (1946).
[CrossRef] [PubMed]

J. Inst. Elec. Eng. (1)

R. G. Hopkinson, “Visibility of cathode-ray-tube traces in radar displays,” J. Inst. Elec. Eng. 93, 795 (1946).

J. Opt. Soc. Am. (2)

J. Psych. (2)

S. B. Williams and N. R. Bartlett, “Visibility on cathoderay tube screens: Problems and methods,” J. Psych. 25, 401 (1948).
[CrossRef]

Williams, Bartlett, and King, “Visibility on cathode-ray tube screens: Screen brightness,” J. Psych. 25, 455 (1948).
[CrossRef]

Proc. Inst. Radio Eng. (1)

R. Payne-Scott, “The visibility of small echoes on radar PPI displays,” Proc. Inst. Radio Eng. 36, 180 (1948).

Other (1)

A. L. Sweet and N. R. Bartlett, “Visibility on cathode-ray tube screens: Signals on a P7 screen exposed for different intervals,” (Manuscript in preparation).

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Figures (5)

F. 1
F. 1

Sample pips used in the experiment. a. Beam width = 1 degree; pulse length = 1 2 microsecond. b. Beam width = 60 degrees; pulse length = 1 2 microsecond. c. Beam width = 1 degree; pulse length = 30 microseconds, d. Beam width = 60 degrees; pulse length = 30 microseconds.

F. 2
F. 2

Visibility as a function of the logarithm of beam width for each of two pulse lengths at each of three brightness levels. The solid lines are drawn through points determined from the equations described in the text. The indicated empirical points are taken from Tables II, III, and IV.

F. 3
F. 3

Visibility as a function of the logarithm of pulse length for each of two beam widths at each of three brightness levels. The solid lines represent the empirical equations described in the text; the indicated empirical points are taken from Tables II, III, and IV.

F. 4
F. 4

Visibility as a function of beam width and pulse length for each of three brightness levels. The surfaces are drawn with values obtained from the empirical equations described in the text.

F. 5
F. 5

Visibility as a function of area (beam width in seconds of visual angle times pulse length in seconds of visual angle) for the dim background.

Tables (4)

Tables Icon

Table I Visual angles and transit times for the various beam widths and pulse lengths.

Tables Icon

Table II Visibility in decibels for the dim background.

Tables Icon

Table III Visibility in decibels for optimal background brightness.

Tables Icon

Table IV Visibility in decibels for the brightest background.

Equations (6)

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visibility = a log ( beam width ) + b ,
visibility = a log ( beam width ) + c log ( pulse lenght ) + d
V = 5.47 log B + 5.56 log P + 12.87 ,
V = 6.02 log B + 18.67 log log 4 P + 32.58 .
V = 7.61 log B + 8.14 log log ( 2.1 ) P + 27.90 .
V = 5.7 log Area + C ,