Abstract

When signal images appear on the phosphorescent screen of a cathode-ray tube, they persist for some time before disappearing from view. This study investigated the visibility of signal images on one type of screen at different intervals from excitation to final disappearance.

Data were furnished by five observers viewing signal images on a P-7 screen of a PPI cathode-ray tube. It was found that the tube bias, which sets the brightness intensity of the rotating sweep, affects both the level of visibility and the duration of visibility. Increasing the bias, and hence dimming the scope, makes the signal traces visible over a longer period of time. Greatest visibility, at intervals longer than seven seconds after excitation, was obtained at the highest bias used. For more recent signals, optimum visibility results from using a lower bias but which yet presents a dim sweep. At high biases, a signal is at maximum visibility at the instant when it is excited by the sweep. At low biases, a signal is most visible immediately after its excitation. These patterns of visibility can be explained in terms of the contrast of the brightness level of the signal image with that of the scope background and by the lessened differential sensitivity of the eye at low intensities.

© 1948 Optical Society of America

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References

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  1. H. W. Leverenz, R.C.A. Rev. 7, 199 (1946).
  2. S. B. Williams and N. R. Bartlett, “Visibility on cathode-ray screens: Problems and methods” (in preparation).
  3. F. Hamburger and E. King, “A recording photometer and its use in studies of cathode ray screen displays” (in preparation).
  4. H. R. Blackwell, J. Opt. Soc. Am. 36, 624 (1946).
    [Crossref] [PubMed]

1946 (2)

Bartlett, N. R.

S. B. Williams and N. R. Bartlett, “Visibility on cathode-ray screens: Problems and methods” (in preparation).

Blackwell, H. R.

Hamburger, F.

F. Hamburger and E. King, “A recording photometer and its use in studies of cathode ray screen displays” (in preparation).

King, E.

F. Hamburger and E. King, “A recording photometer and its use in studies of cathode ray screen displays” (in preparation).

Leverenz, H. W.

H. W. Leverenz, R.C.A. Rev. 7, 199 (1946).

Williams, S. B.

S. B. Williams and N. R. Bartlett, “Visibility on cathode-ray screens: Problems and methods” (in preparation).

J. Opt. Soc. Am. (1)

R.C.A. Rev. (1)

H. W. Leverenz, R.C.A. Rev. 7, 199 (1946).

Other (2)

S. B. Williams and N. R. Bartlett, “Visibility on cathode-ray screens: Problems and methods” (in preparation).

F. Hamburger and E. King, “A recording photometer and its use in studies of cathode ray screen displays” (in preparation).

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Figures (9)

Fig. 1
Fig. 1

General scheme of apparatus used for studying visibility of signals at different exposures with varying amounts of delay following electronic excitation.

Fig. 2
Fig. 2

Peak brightness of the PPI sweep at different CRT biases.

Fig. 3
Fig. 3

Decay in brightness of scope background after excitation by sweep at four different CRT biases.

Fig. 4
Fig. 4

Visibility of signals on a P7 screen as a function of time after excitation.

Fig. 5
Fig. 5

Duration of visibility for signals of different strengths at four different CRT biases.

Fig. 6
Fig. 6

Strength of minimum detectable signal as a function of different CRT biases for various times of delay.

Fig. 7
Fig. 7

Visibility of signal at fluorescence and at short intervals of phosphorescence with four different CRT biases.

Fig. 8
Fig. 8

Difference in visibility of signal image at fluorescence and immediately afterwards (0.04 second) (visibility at fluorescence minus visibility immediately following).

Fig. 9
Fig. 9

Explanation of duration of visibility in terms of brightness contrast between signal image and scope background (data from brightness decay curves).

Tables (1)

Tables Icon

Table I Visibility in decibels of attenuation below reference voltage for different times of delay at four different CRT biases (means of 10 readings: 2 for each of 5 observers).