System and method for driving electrowetting display device

1. A method of driving an electrowetting display device including a plurality of sub-pixels, the method comprising:

determining whether a sub-pixel in the plurality of sub-pixels is in an open state or a closed state;

determining a target reflectance value for the sub-pixel;

for the sub-pixel in the open state:

determining that the target reflectance value is less than a first threshold value, the first threshold value being a value less than a maximum reflectance value and greater than a minimum reflectance value; and

setting a reflectance value of the sub-pixel to the minimum reflectance value or the first threshold value; and

for the sub-pixel in the closed state:

determining that the target reflectance value is less than a second threshold value, the second threshold value being a value greater than the first threshold value, and

setting the reflectance value of the sub-pixel to either the minimum reflectance value or the second threshold value.

2. The method of claim 1 , wherein the first threshold value is a highest reflectance value that causes the sub-pixel to be in a closed state when the reflectance value of the sub-pixel is set to the first threshold value and wherein the second threshold value is a lowest reflectance value that causes the sub-pixel to be in an open state when the reflectance value of the sub-pixel is set to the threshold value.

3. The method of claim 1 , further comprising, after setting the reflectance value of the sub-pixel, calculating a quantization error by determining a difference between the reflectance value of the sub-pixel and the target reflectance value.

4. The method of claim 3 , further comprising:

determining a second target reflectance value for an adjacent second sub-pixel of the plurality of sub-pixels; and

modifying the second target reflectance value for the adjacent second sub-pixel by increasing or decreasing the second target reflectance value of the adjacent second sub-pixel by an amount dependent upon the quantization error.

5. A method of driving an electrowetting display device including a plurality of sub-pixels, the method comprising:

determining whether a sub-pixel in the plurality of sub-pixels is in an open state or a closed state;

determining a target reflectance value for the sub-pixel; and

setting a set reflectance value of the sub-pixel based upon whether the sub-pixel is in the open state or the closed state and the target reflectance value, wherein the set reflectance value is a different value from the target reflectance value.

6. The method of claim 5 , including, for the sub-pixel in the open state:

determining that the target reflectance value is less than a first threshold value, the first threshold value being less than a maximum reflectance value; and

setting the set reflectance value of the sub-pixel to either a minimum reflectance value or the first threshold value.

7. The method of claim 6 , further comprising setting the first threshold value to a highest reflectance value that causes the sub-pixel to be in a closed state when the reflectance value of the sub-pixel is set to the first threshold value.

8. The method of claim 6 , wherein setting the set reflectance value of the sub-pixel to either the minimum reflectance value or the first threshold value includes:

comparing the target reflectance value to the minimum reflectance value and the first threshold value; and

setting the reflectance value of the sub-pixel to the first threshold value when the target reflectance value is closer to the first threshold value than the minimum reflectance value.

9. The method of claim 5 , including, for the sub-pixel in the closed state:

determining that the target reflectance value is less than a second threshold value, and

setting the set reflectance of the sub-pixel to either a minimum reflectance value or the second threshold value.

10. The method of claim 9 , wherein the second threshold value is a lowest reflectance value that causes the sub-pixel to be in an open state when the set reflectance value of the sub-pixel is set to the second threshold value.

11. The method of claim 9 , wherein setting the set reflectance of the sub-pixel to either a minimum reflectance value or the second threshold value includes setting the set reflectance value of the sub-pixel to the minimum reflectance value when the target reflectance value is closer to the minimum reflectance value than the second threshold value.

12. The method of claim 5 , further comprising, after setting the set reflectance value of the sub-pixel, calculating a quantization error by determining a difference between the set reflectance value of the sub-pixel and the target reflectance value.

13. The method of claim 12 , further comprising:

determining a second target reflectance value for an adjacent second sub-pixel of the plurality of sub-pixels; and

modifying the second target reflectance value for the adjacent second sub-pixel by increasing or decreasing the second target reflectance value for the adjacent second sub-pixel by an amount dependent upon the quantization error.

14. A display device, comprising:

a sub-pixel including:

a plurality of sub-pixel walls defining a cavity, and

a first fluid and a second fluid within the cavity, the first fluid being immiscible with the second fluid; and

a display controller including:

an input line for receiving data relating to a target reflectance of the sub-pixel; and

an output line for providing at least one display signal level for applying a voltage to a first electrode in the sub-pixel to establish a driving voltage for the sub-pixel,

wherein the display controller is configured to:

determine whether the sub-pixel is in an open state or a closed state;

determine a target reflectance value for the sub-pixel; and

set a set reflectance value of the sub-pixel based upon whether the sub-pixel is in the open state or the closed state and the target reflectance value, wherein the set reflectance value is a different value from the target reflectance value.

15. The display device of claim 14 , wherein the controller is configured to, for the sub-pixel in the open state:

determine that the target reflectance value is less than a first threshold value, the first threshold value being less than a maximum reflectance value; and

set the set reflectance value of the sub-pixel to either a minimum reflectance value or the first threshold value.

16. The display device of claim 15 , wherein the first threshold value is a highest reflectance value that causes the sub-pixel to be in a closed state when the reflectance value of the sub-pixel is set to the first threshold value.

17. The display device of claim 14 , wherein the controller is configured to, for the sub-pixel in the closed state:

determine that the target reflectance value is less than a second threshold value; and

set the set reflectance of the sub-pixel to either a minimum reflectance value or the second threshold value.

18. The display device of claim 17 , wherein the second threshold value is a lowest reflectance value that causes the sub-pixel to be in an open state when the set reflectance value of the sub-pixel is set to the second threshold value.

19. The display device of claim 14 , wherein the controller is configured to, after setting the set reflectance value of the sub-pixel, calculate a quantization error by determining a difference between the set reflectance value of the sub-pixel and the target reflectance value.

20. The display device of claim 19 , wherein the controller is configured to:

determine a second target reflectance value for an adjacent second sub-pixel of the plurality of sub-pixels; and

modify the second target reflectance value for the adjacent second sub-pixel by increasing or decreasing the second target reflectance value for the adjacent second sub-pixel by an amount dependent upon the quantization error.