Flexible color modulation tables of ratios for generating color modulation patterns

• US 6,466,190 B1
• Filed: 06/19/2000
• Issued: 10/15/2002
• Est. Priority Date: 06/19/2000
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Evoy, David R.
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): Sheng, Tom V
• Application Number:
  US09/596,923
• Time in Patent Office: 848 Days
• Field of Search: 345/87-89, 345/99, 345/691, 345/600-604
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence

Abstract

A method for providing intensity modulation for a display of an electronic device. The method uses tables of ratios for generating color modulation patterns. The method includes the step of defining a table of intensity values with each intensity value including a respective on-ratio and a respective off-ratio. A pixel intensity for a pixel of a display is selected by selecting a corresponding intensity value in the table. The pixel intensity is implemented by using an accumulator having an output for determining whether the pixel is on or off, wherein the pixel is on for zero and for positive values of the output and off for negative values of the output. The output is used to implement a duty cycle for the pixel, by turning the pixel on and off. The duty cycle is implemented by setting an initial output of the accumulator. The output is subsequently set to a value equal to the output minus the off-ratio if the pixel is on, and setting the output to the output plus the on-ratio if the pixel is off. Successively turning the pixel on and off in accordance with the output thereby implements a duty cycle for the pixel according to the on-ratio and off-ratio of the intensity value.

Claims

1. A method for providing intensity modulation for a display of an electronic device, the method comprising the steps of:

a) defining a table of intensity values, each intensity value including a respective on-ratio and a respective off-ratio;

b) selecting a pixel intensity for a pixel of a display by selecting a corresponding intensity value in the table; and

c) implementing the pixel intensity by using an accumulator, the accumulator having an output for determining whether the pixel is on or off, wherein the pixel is on for zero and for positive values of the output and off for negative values of the output, and wherein the output is used to implement a duty cycle for the pixel by;

c1) setting an initial output of the accumulator;

c2) setting the output to the output minus the off-ratio if the pixel is on; and

c3) setting the output to the output plus the on-ratio if the pixel is off, thereby implementing a duty cycle for the pixel according to the on-ratio and off-ratio of the intensity value.

2. The method of claim 1 wherein step b) further includes the step of:

receiving the pixel intensity from an application executing on the electronic device and selecting the corresponding pixel intensity value in the table.

3. The method of claim 1 wherein step a) further includes the steps of:

defining an on-ratio table using an on-ratio unit; and

defining an off-ratio table using an off-ratio unit.

4. The method of claim 3 further including the step of:

providing the on-ratio and the off-ratio to the accumulator via the on-ratio unit and the off-ratio unit.

5. The method of claim 1 wherein step a) further includes the step of:

defining the table of intensity values, each intensity value including a respective period.

6. The method of claim 1 wherein the display is a passive LCD (liquid crystal display) type display.

7. The method of claim 1 further including the step of:

maintaining a history of the accumulator output using a shift register.

8. A system for providing intensity modulation for a display of an electronic device, comprising:

a memory storing a table of intensity values, each intensity value including a respective on-ratio and a respective off-ratio, the memory coupled to receive a pixel intensity from an external application, wherein the pixel intensity is for a pixel of a display and is configured to select a corresponding intensity value in the table; and

an accumulator for implementing the pixel intensity, the accumulator coupled to the memory and having an output for determining whether the pixel is on or off, wherein the pixel is on for zero and for positive values of the output and off for negative values of the output, and wherein the output is used to implement a duty cycle for the pixel by;

c1) setting an initial output of the accumulator;

c2) setting the output to the output minus the off-ratio if the pixel is on; and

c3) setting the output to the output plus the on-ratio if the pixel is off, thereby implementing a duty cycle for the pixel according to the on-ratio and off-ratio of the intensity value.

9. The system of claim 8 wherein the memory further comprises:

an on-ratio unit for defining an on-ratio table; and

off-ratio unit for defining an off-ratio table, the on-ratio table and the off-ratio table implementing the table of intensity values.

10. The system of claim 9 wherein the on-ratio and the off-ratio are provided to the accumulator via the on-ratio unit and the off-ratio unit respectively.

11. The system of claim 8 wherein the table of intensity values each include a respective period.

12. The system of claim 8 wherein the display is a passive LCD (liquid crystal display) type display.

13. The system of claim 8 further comprising a shift register for maintaining a history of the accumulator output.

14. The system of claim 13 wherein the history of the accumulator output is used to generate an offset for similar intensities to avoid interference on the display.

15. A method for providing gray scale intensity modulation for a passive LCD display of a digital electronic device, the method comprising the steps of:

a) defining a table of intensity values, each intensity value including a respective on-ratio and a respective off-ratio;

b) selecting a pixel intensity for a pixel of a display by selecting a corresponding intensity value in the table;

c) implementing the pixel intensity by using an accumulator, the accumulator having an output for determining whether the pixel is on or off, wherein the pixel is on for zero and for positive values of the output and off for negative values of the output, and wherein the output is used to implement a duty cycle for the pixel by;

c1) setting an initial output of the accumulator;

c2) setting the output to the output minus the off-ratio if the pixel is on;

c3) setting the output to the output plus the on-ratio if the pixel is off, thereby implementing a duty cycle for the pixel according to the on-ratio and off-ratio of the intensity value; and

d) maintaining a history of the accumulator output using a shift register, wherein the history is used to generate an offset for similar intensities implemented by the accumulator to avoid interference on the display.

16. The method of claim 15 wherein step b) further includes the step of:

receiving the pixel intensity from a software application executing on the digital electronic device and selecting the corresponding pixel intensity value in the table.

17. The method of claim 15 wherein step a) further includes the steps of:

defining an on-ratio table using an on-ratio unit; and

defining an off-ratio table using an off-ratio unit.

18. The method of claim 17 further including the step of:

providing the on-ratio and the off-ratio to the accumulator via the on-ratio unit and the off-ratio unit.

19. The method of claim 15 wherein step a) further includes the step of:

defining the table of intensity values, each intensity value including a respective period.

20. The method of claim 15 further including the step of:

selecting the on-ratio for the accumulator or the off-ratio for the accumulator by using a multiplexer coupled to the accumulator.