Method and apparatus for modulating the perceptible intensity of a light emitting display

• US 4,149,111 A
• Filed: 11/25/1977
• Issued: 04/10/1979
• Est. Priority Date: 11/25/1977
• Status: Expired due to Term

• Current Assignee: Leidos, Inc. (Leidos Holdings, Inc.)
• Original Assignee: Leidos, Inc. (Leidos Holdings, Inc.)
• Inventors: Coates, William J. Jr.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/854,891
• Time in Patent Office: 501 Days
• Field of Search: 365/116, 340/324 M, 340/340, 340/335, 340/343, 315/169 R, 315/169 TV
• US Class Current: 315/169.4
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 3/2944 by varying the frequency of sustain pulses or the number of sustain pulses proportionally in each subfield of the whole frame
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: H04N 3/125 using gas discharges, e.g. plasma

Abstract

A method and apparatus for modulating the perceptible intensity of the presentation of a light emitting display which light emitting display emits light by gas discharge and recombination of ions and free electrons of a display medium; includes a system clock, the interruption of which causes the interruption of the presentation of the light emitting display; and is capable of retaining display information upon the interruption of a light sustaining signal or the electrical power as a result of an accumulation and retention of electrical charge across the display medium. The apparatus comprising a repetition means for generating a repetition pulse train signal having a controllable frequency and duty cycle; an indication means for generating a retention signal that identifies when the light emitting display is capable of retaining display information; a synchronization means coupled to said repetition means and to said indication means for generating a gating signal which is synchronized with the retention signal and the repetition pulse train signal; and stopping means coupled to said synchronization means for interrupting the system clock in synchronization with the gating signal. Variations of this invention include circuitry which generates a control system clock signal by clock pulse train generator and modified stopping means. Other variations enable the light emitting display to be turned off over extended periods of time.

Claims

1. An apparatus for interrupting the presentation of a light emitting display, said light emitting display being of the type which emits light by the ionization discharge of a display medium, and which includes a system clock signal, the interruption of which causes an interruption in the presentation of the light emitting display, and which is capable of retaining display information on the interruption of a light sustaining signal as a result of the accumulation and retention of electrical charge across said display medium, such apparatus comprising:

(a) turn-off means for generating a turn-off signal to indicate when the presentation of the light emitting display is to be interrupted;

(b) indication means for generating a retention signal which identifies when the light emitting display is capable of retaining display information;

(c) synchronization means coupled to said turn-off means and to said indication means for generating a gating signal which is in synchronization with the turn-off signal and the repetition signal; and

(d) stopping means coupled to said synchronization means for interrupting the system clock signal of the light emitting display in synchronization with the gating signal so that the presentation of the light emitting display is interrupted.

2. The apparatus of claim 1 which further comprises a clock means for generating a clock pulse train signal, said stopping means being coupled to said clock means and to said synchronization means, and said stopping means generating a simulated system clock signal by interrupting the clock pulse train signal in synchronization with the gating signal, said simulated system clock signal being connected to said light emitting display such that the simulated system clock signal overrides the system clock signal of the light emitting display whereby the presentation of the light emitting display is interrupted.

3. The apparatus of claim 1 wherein the inactive state of the turn-off signal indicate when the presentation of the light emitting display is to be interrupted.

4. The apparatus of claim 1 wherein the active state of the retention signal identifies when the light emitting display is capable of retaining display information upon the interruption of the light sustaining signal.

5. The apparatus of claim 4 wherein the active state of the indication means is after the gas discharge of the display medium and is before the next transition, either positive or negative, of the light sustaining signal.

6. The apparatus of claim 1 wherein the inactive state of the gating signal is in synchronization with the inactive state of the turn-off signal and the active state of the retention signal.

7. The apparatus of claim 1 which further comprises a power down means for turning off the electrical power which is applied to the light emitting display after the system clock has been interrupted whereby a high impedance is coupled to the light emitting display.

8. A method for interrupting the presentation of a light emitting display, said light emitting display being of the type which emits light as a result of the ionization discharge of a display medium, and which includes an internal system clock signal, the interruption of which results in the interruption of the presentation of the light emitting display, and which is capable of retaining display information upon the interruption of a light sustaining signal as a result of the accumulation and retention of electrical charge across said display medium, such method comprising:

(a) generating a turn-off signal to indicate when the presentation of the light emitting display is to be interrupted;

(b) generating a retention signal to identify when the light emitting display is capable of retaining display information;

(c) generating a gating signal in synchronization with the turn-off signal and the retention signal; and

(d) interrupting the system clock signal in synchronization with the gating signal so that the presentation of the light emitting display is interrupted.

9. An apparatus for modulating the perceptible intensity of the presentation of a light emitting display, said light emitting display being of the type which emits light by the ionization discharge of a display medium, and which includes a system clock signal, the interruption of which causes an interruption in the presentation of the light emitting display, and which is capable of retaining display information upon the interruption of a light sustaining signal as a result of the accumulation and retention of electrical charge across the display medium, such apparatus comprising:

(a) repetition means for generating a repetition pulse train signal having an adjustable frequency which is lower than the frequency of the system clock signal;

(b) indication means for generating a retention signal which identifies when the light emitting display is capable of retaining display information;

(c) synchronization means coupled to said repetition means and to said indication means for generating a gating signal which is in synchronization with the repetition pulse train signal and the retention signal; and

(d) stopping means coupled to said synchronization means for interrupting the system clock signal of the light emitting display in synchronization with the gating signal.

10. The apparatus of claim 9 which further comprises a clock means for generating a clock pulse train signal, said stopping means being coupled to said clock means and to said synchronization means, and said stopping means generating a simulated system clock signal by interruption the clock pulse train signal in synchronization with the gating signal, said simulated system clock signal being connected to said light emitting display such that the simulated system clock signal overrides the system clock signal of the light emitting display whereby the presentation of the light emitting display is modulated.

11. The apparatus of claim 9 wherein the frequency of the repetition pulse train signal is adjustable between zero and 100 Hz.

12. The apparatus of claim 9 wherein the duty cycle of the repetition pulse train signal is adjustable between zero and 100%.

13. The apparatus of claim 9 wherein the inactive portion of the repetition pulse train signal indicates when the presentation of the light emitting display is to be interrupted.

14. The apparatus of claim 9 wherein the active state of the retention signal identifies when the light emitting display is capable of retaining display information.

15. The apparatus of claim 9 wherein the active portion of the gating signal is in synchronization with the active state of the repetition pulse train signal and wherein the inactive portion of the gating signal is in synchronization with the inactive state of the repetition signal and the active state of the retention signal.

16. The apparatus of claim 9 wherein the system clock is interrupted in synchronization with the inactive state of the gating signal.

17. A method for modulating the perceptible intensity of a light emitting display, said light emitting display being of the type which emits light by the ionization discharge of a display medium, and which includes a system clock signal, the interruption of which causes an interruption in the presentation of the light emitting display, and which is capable of retaining display information on the interruption of a light sustaining signal as a result of the accumulation and retention of electrical charge across the display medium, such method comprising:

(a) generating a repetition pulse train signal which has an adjustable frequency which is lower than the frequency of the system clock;

(b) generating a retention signal which identifies when the light emitting display is capable of retaining display information;

(c) generating a gating signal which is in synchronization with the repetition pulse train signal and the retention signal;

(d) interruption the system clock in synchronization with the gating signal;

(e) adjusting the duty cycle of the repetition pulse train signal so that the perceptible intensity of the light emitting display is modulated; and

(f) adjusting the frequency of the repetition pulse train signal so that the perceptible intensity of the light emitting display is modulated and so that no perceptible flicker is detected.