Apparatus and drive method for display light source

• US 20100283719A1
• Filed: 05/06/2010
• Published: 11/11/2010
• Est. Priority Date: 05/09/2009
• Status: Abandoned Application

• Current Assignee: Chen-Jean Chou
• Original Assignee: Chen-Jean Chou
• Inventors: Chou, Chen-Jean
• Application Number:
  US12/774,760
• Publication Number:
  US 20100283719A1
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A display device comprising a backlight and a light valve array, such as an array of liquid crystal (LC) cells, and a method for operating such display device are provided. The display and the method operate to reduce the intensity of the light source of the backlight during the period when the light valve (LC cell) is in the transition from a dark state to a bright state, and to increase the intensity during the period when the light valve (LC cell) is near or mostly completing its transition. As light transmission is ineffective in the dark or transitional state of the light valve, lighting power efficiency is improved by delivering the light mostly in the final state of the light valve.

Claims

1. A display device comprising:

a plurality of light emitting elements;

wherein the response time of said light emitting elements is T2;

a light modulator comprising a plurality of light valves modulating light directed thereto;

wherein the relaxation time from the fully charged state to the fully relaxed state of said light valve is T1, and wherein T1 is substantially greater than T2;

a control circuit performing recurring operations on said light emitting elements and said light valves;

said operations comprising setting the light valves according to an image information to display image;

said operations comprising;

3) applying image signal to a light valve according to the image data for displaying image;

4a) a delay period after operation

     3);

4b) after said delay period, applying the control signal that sets at least a light emitting element that illuminates said light valve in

     3) to a bright state;

wherein the response time of the light valve in response to said operation

     3) is T3;

said delay period is at least one-twentieth of T3.

2. The device according to claim 1 wherein said control signals for setting said light emitting element to a bright state set the light emitting element to an intensity substantially higher than the average light output of the light emitting element averaged over a period of one or more operation cycles.

3. The device according to claim 1 wherein the duration of operation 4a) is longer than operation 4b).

4. The device according to claim 1 wherein said operations further comprise:

1) applying the control signals for setting a light emitting element to off or a dimming state;

wherein said operation

     1) precedes operation

     3).

5. The device according to claim 4 wherein said operations further comprises 2) applying a control signal that sets a light valve illuminated by said light emitting element to a relaxed state.

6. The device according to claim 5 wherein in an operation cycle, said operation 2) precedes said operation 1) by a small fraction of T1;

or

said operation

     1) precedes said operation

     2);

or

said operation

     1) leads and overlaps operation

     2);

wherein a small fraction of T1 is less than 30% of T1.

7. The device according to claim 5 wherein in an image refreshing operation cycle, operation 2) precedes operation 3).

8. The device according to claim 1 wherein said plurality of light valves and said light emitting elements are arranged separately in plurality of groups;

wherein the groups of light valves are operated in coordination with the groups of light emitting elements in a manner that said operation

     3) operates on a group of light valves, setting the light valves according to image data, and said operation 4b) operates on a group of light emitting elements illuminating said group of light valves to a bright level after the delay period of 4a).

9. The device according to claim 5 wherein said operation step 1) sets all said light emitting elements to off or a dimming state, and wherein said operation 2) sets all Light valves to a relaxed state;

wherein in an operation cycle, said operation

     1) precedes or overlaps said operation

     2), and said operation

     2) precedes said operation

     3).

10. The device according to claim 5 wherein a group of said light valves are arranged to connect to a first common electrode, and wherein said operation 2), setting a light valve to a relaxed state, is effectuated on said group of Light valves by applying a control voltage to said first common electrode.

11. The device according to claim 10 wherein said common electrode connects to all light valves of the display, wherein said operation 2) operates on all light valves by applying a voltage to said common electrode, setting all light valves to the relaxed state.

12. The device according to claim 1 wherein a group of said light emitting elements is arranged to connected to a second common electrode, wherein said operation 1) is effectuated on the group of light emitting elements by applying a control voltage to the second common electrode.

13. The device according to claim 5 wherein the relaxed state of a light valve corresponds to a state where the voltage applied on the light valve is zero or near neutral.

14. The device according to claim 5 wherein said plurality of light valves form array of cells;

said control circuit comprising at least a data driver circuit for delivering image data to said light valves, and at least a scan driver circuit for selecting light valve cells to receive the image data according to a control timing;

wherein said scan driver comprising a plurality of output terminals each connecting to a plurality of light valve cells via a scan electrode;

wherein said scan driver further comprises a recurring discharge operation;

said discharge operation enabling a selected group of said scan driver terminals at a time so that all light valves connected to said group of scan driver output terminals are enabled at the same time to receive data from said data driver during such discharge operation.

15. The device according to claim 14 wherein said data driver operates to set a discharging voltage to its data output terminals for the period when said scan driver performs said discharging selection;

said discharging voltage setting the light vales to a relaxed state.

16. The device according to claim 1 wherein said operations further comprises 5) applying a control signal for setting a light valve to a charged or over-charged state.

17. The display device according to claim 16 wherein said charged or over-charged state of the light valve corresponds to a voltage near or higher than the voltage for operating said light valve for displaying a full range of gray scale.

18. The device according to claim 16 wherein said charged or over-charged state of the light valve corresponds to a dark state of said light valve.

19. The device according to claim 16 wherein said operation 5) precedes said operation 3).

20. The device according to claim 19 further comprising an operation 7) applying a control signal that sets a light emitting element to off or a dark state.

21. The device according to claim 20 wherein said operation 7) precedes operation 4b).

22. The device according to claim 1 wherein in said operation 4b), said control circuit applies the control signals for setting said light emitting element to a bright state according to a scaling relation with the average or maximum image brightness in the area illuminated by said light emitting element, wherein said scaling relation provides a brightness setting that increases with increasing average or maximum image brightness in said area for at least part of the brightness range.

23. The device according to claim 1 wherein a said light valve is a liquid crystal (LC) cell or a MEMS cell.

24. The device according to claim 5 wherein said relaxed state of said light valve corresponds to a bright state at which the LC cell allows the light to pass to the viewing side.

25. A method of operating a display device;

said device comprising;

a plurality of light emitting elements;

a plurality of light valves modulating light output from said light emitting elements;

said method comprising recurring operations of;

3) applying image signal to a light valve for displaying an image;

4a) a delay period after operation

     3);

4b) after said delay period, applying a control signal that sets at least a light emitting element that illuminates said light valve of

     3) to a bright state;

wherein the response time of the light valve in response to said operation

     3) is T3;

said delay period is at least a significant fraction of T3.

26. The method according to claim 25 wherein said operations further comprise:

1) applying the control signals that sets a light emitting element to off or a dimming state;

wherein said operation

     1) precedes operation

     3).

27. The method according to claim 25 wherein said control circuit performs recurring operations on said light emitting elements and said light valves;

said operations further comprising

     2) applying a control signal that sets a light valve in the area illuminated by said light emitting element to a relaxed state.

28. A circuit for operating a light valve and a light emitting element in coordination, said circuit performing recurring operations of:

applying a SELECT signal for enabling said light valve to receive an image data;

providing a delay time;

after said delay time, applying a lighting control signal for enabling power for driving said light emitting element;

wherein said delay time is substantially greater than zero.

29. The circuit according to claim 28 wherein said delay time is at least a significant fraction of the response time of said light valve in response to receiving said image data.

30. The circuit according to claim 28 wherein said operations further comprise a step of applying a control signal for setting said light valve to a charged or over-charged state.

31. The circuit according to claim 30 wherein said charged or over-charged state of the light valve corresponds to a voltage setting near or higher than the voltage that sets said light valve to the lowest gray scale.

32. The circuit according to claim 30 wherein said charged or over-charged state of the light valve corresponds to a dark state of said light valve.