Image display

• US 20030201956A1
• Filed: 04/30/2002
• Published: 10/30/2003
• Est. Priority Date: 04/30/2002
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Anderson, Daryl, da Cunha, John M.
• Granted Patent: US 7,061,480 B2
• Time in Patent Office: Days
• US Class Current: 345/82
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0857 Static memory circuit, e.g. flip-flop
• CPC Class Codes: G09G 2360/141 the light conveying information used for selecting or modulating the light emitting or modulating element
• CPC Class Codes: G09G 2360/142 the light being detected by light detection means within each pixel
• CPC Class Codes: G09G 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/02 by tracing or scanning a light beam on a screen
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]

Abstract

A display cell includes a light sensor, a display element coupled to light sensor; and a memory coupled to the light sensor. A display and an optically addressable display system using a display cell are provided. Methods for using a display cell are also provided.

Claims

1. A display cell, comprising:

a light sensor;

a display element coupled to the light sensor; and

a memory coupled to the light sensor.

2. The display cell of claim 1, further comprising:

a switch having a selector, an input, and an output, wherein;

the light sensor is coupled to the switch selector;

the display element is coupled to the switch input or output; and

the memory comprises an energy storage element coupled to the switch selector.

3. The display cell of claim 2, further comprising a resistor coupled to the switch selector.

4. The display cell of claim 2, wherein:

the light sensor is a photo diode having a cathode and an anode; and

the display element is a light emitting diode (LED) having a cathode and an anode.

5. The display cell of claim 4, wherein:

the cathode of the photo diode is coupled to the switch selector; and

the anode of the LED is coupled to the switch output or the cathode of the LED is coupled to the switch input.

6. The display cell of claim 5, wherein the switch comprises a field effect transistor (FET) having a gate, a source, and a drain, wherein:

the gate is the switch selector;

the drain is the switch input; and

the source is the switch output.

7. The display cell of claim 6, wherein the energy storage element is coupled between the FET gate and the FET source.

8. The display cell of claim 7, further comprising a resistor coupled between the FET gate and the FET source.

9. The display cell of claim 6, wherein the energy storage element is a gate capacitance of the FET as measured from the FET gate to the FET source.

10. The display cell of claim 9, further comprising a resistor coupled between the FET gate and the FET source.

11. The display cell of claim 2, wherein the light sensor is a photo transistor having a collector and an emitter.

12. The display cell of claim 1, wherein:

the memory comprises a state machine having an input, an output, and a reset;

the light sensor is coupled to the state machine input; and

the display element is coupled to the state machine output.

13. The display cell of claim 12, wherein:

the light sensor is a photo diode having a cathode and an anode; and

the display element is a light emitting diode (LED) having a cathode and an anode.

14. The display cell of claim 13, wherein:

the photo diode cathode is coupled to the state machine input; and

the LED anode is coupled to the state machine output.

15. The display cell of claim 14, wherein the photo diode anode is coupled to the state machine reset.

16. The display cell of claim 1, further comprising:

a switch having a selector, an input, and an output, wherein;

the memory is a state machine having an input, an output, and a reset;

the selector is coupled to the state machine output;

the light sensor is coupled to the state machine input; and

the display element is coupled to the switch input or the switch output.

17. The display cell of claim 16, wherein:

the light sensor is a photo diode having a cathode and an anode, wherein the photo diode cathode is coupled to the state machine input; and

the display element is a light emitting diode (LED) having a cathode and an anode, wherein the LED anode is coupled to the switch output or wherein the LED cathode is coupled to the switch input.

18. The display cell of claim 17, wherein the switch comprises a field effect transistor (FET) having a gate, a source, and a drain, wherein:

the gate is the switch selector;

the drain is the switch input; and

the source is the switch output.

19. The display cell of claim 18, wherein the photo diode anode is coupled to the state machine reset.

20. A display, comprising a plurality of display cells, at least one of the display cells comprising:

a light sensor;

a display element coupled to the light sensor; and

a memory coupled to the light sensor.

21. The display of claim 20, wherein at least one of the display cells further comprises a switch having a selector, an input, and an output, wherein:

the light sensor has an output coupled to the switch selector; and

the display element has an input and an output, wherein the display element input is coupled to the switch output or the display element output is coupled to the switch input.

22. The display of claim 20, wherein the memory comprises an energy storage element coupled to the switch selector.

23. The display of claim 22, wherein a resistor is coupled to the switch selector.

24. The display of claim 20, wherein:

the memory of at least one of the display cells comprises a state machine having an input, an output, and a reset, wherein;

the light sensor comprises an output coupled to the state machine input; and

the display element comprises an input coupled to the state machine output.

25. The display of claim 24, wherein:

the light sensor is a photo diode having a cathode and an anode, wherein the photo diode cathode is the light sensor output; and

the display element is a light emitting diode (LED) having a cathode and an anode, wherein the LED anode is the display element input.

26. The display of claim 20, wherein at least one of the display cells further comprises a switch having a selector, an input, and an output;

wherein;

the memory comprises a state machine having an input, an output, and a reset;

the display element has an input and an output, wherein the display element input is connect to the switch output, or the display element output is connected to the switch input;

the selector is coupled to the state machine output; and

and the light sensor comprises an output coupled to the state machine input.

27. The display of claim 26, wherein:

the light sensor is a photo diode having a cathode and an anode, wherein the photo diode cathode is the light sensor output; and

the display element is a light emitting diode (LED) having a cathode and an anode, wherein;

the LED anode is the display element input; and

the LED cathode is the display element output.

28. The display of claim 27, wherein the switch comprises a field effect transistor (FET) having a gate, a source, and a drain, wherein:

the gate is the switch selector;

the drain is the switch input; and

the source is the switch output.

29. An optically addressable display system, comprising:

a controller configured to receive image data;

a raster scanning source coupled to the controller, wherein the raster scanning source can generate at least one raster light beam;

a display, comprising;

a plurality of display cells, each comprising;

light sensing means for responding to at least one raster light beam; and

means for light display coupled to the light sensing means; and

means for memory coupled to the light sensing means.

30. A display cell, comprising:

means for light sensing;

means for light emitting coupled to the means for light sensing; and

means for memory coupled to the means for light sensing.

31. A method for displaying images, comprising:

positioning a raster light beam to activate a light sensor;

charging an energy storage element with the activated light sensor;

activating a display element using the charged energy storage element;

positioning the raster light beam to deactivate the light sensor;

discharging the energy storage element; and

keeping the display element active until the energy storage element is substantially discharged.

32. The method for displaying images according to claim 31, wherein discharging the energy storage element is accomplished, in part, by leaking current through the display element.

33. The method for displaying images according to claim 32, wherein discharging the energy storage element is accomplished, in part, by leaking current through a resistor.

34. A method for displaying images using an array of display cells each having at least one display element, comprising:

providing power to the display cells to turn each display element off;

storing a previous state for each display cell as “

off”

;

indexing a raster scanning source to a display cell;

determining whether a desired light output state is “

on”

or “

off”

for the display cell; and

activating a raster light beam of the raster scanning source if the logical exclusive-or (XOR) of the previous state for the display cell and the desired light output state for the display cell computes as “

on”

.

35. The method for displaying images according to claim 34, further comprising:

after the determining action, storing the desired light output state as the previous state for the display cell;

after the activating action, indexing the raster scanning source to a next display cell;

indexing a raster scanning source to an other display cell; and

repeating the determining and activating actions for the other display cell.

36. A display cell, comprising:

a field effect transistor (FET) having a gate, a source, and a drain;

a photo diode having a cathode and an anode, wherein the photo diode cathode is coupled to the FET gate;

a light emitting diode (LED) having a cathode and an anode, wherein the LED anode is coupled to the FET source or wherein the LED cathode is coupled to the FET drain;

an energy storage element coupled between the FET gate and the FET source; and

a resistor coupled between the FET gate and the FET source.

37. A display cell, comprising:

a state machine having an input and an output;

a photo diode having a cathode and an anode, wherein the photo diode cathode is coupled to the toggle flip-flop input;

a field effect transistor (FET) having a gate, a drain, and a source, wherein the gate is coupled to the toggle flip-flop output; and

a light emitting diode (LED) having an anode and a cathode, wherein the LED anode is coupled to the FET source or wherein the LED cathode is coupled to the FET drain.