# US 10,311,805 B2 · System and method for driving electrowetting display device

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- Number: US 10,311,805 B2
- Document ID: US10311805B2
- Status: Granted
- Kind: B2
- Application number: 15/667,120
- Filed: 2017-08-02
- Published: 2017-11-16
- Granted: 2019-06-04
- Earliest claimed: 2015-06-29
- Assignees: Amazon Technologies, Inc.
- Applicants: Amazon Technologies, Inc.
- Inventors: Petrus Maria de Greef
- Web page: https://patentgrep.com/patent/US10311805B2

## CPC

- G09G 3/348: {based on the deformation of a fluid drop, e.g. electrowetting}
- G02B 26/005: {based on electrowetting}
- G06F 3/041: Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G09G 2300/0404: Matrix technologies
- G09G 2300/0456: with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
- G09G 2300/0469: Details of the physics of pixel operation
- G09G 2300/08: Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
- G09G 2320/066: for control of contrast
- G09G 2360/144: the light being ambient light
- G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data
- G09G 2380/14: Electronic books and readers
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A system and method of driving an electrowetting display device including a plurality of sub-pixels are presented. A sub-pixel in the plurality of sub-pixels is determined to be in an open state or a closed state and a target reflectance value is determined for the sub-pixel. For the sub-pixel in the open state, the target reflectance value is determined to be less than a first threshold value, and a reflectance value of the sub-pixel is set to either a minimum reflectance value or the first threshold value. For the sub-pixel in the closed state, the target reflectance value is determined to be less than a second threshold value, and the reflectance of the sub-pixel is set to either the minimum reflectance value or the second threshold value.

## Claims

### Claim 1

A method of driving a group of sub-pixels of an electrowetting display device, the method comprising:
for a first sub-pixel of the group of sub-pixels:
determining that the first sub-pixel is currently in an open state;
determining a first target reflectance value for the first sub-pixel;
determining that the first target reflectance value is above a first threshold value and below a second threshold value;
determining that the first target reflectance value is closer to the first threshold value than the second threshold value;
setting a first reflectance for the first sub-pixel to the first threshold value; and
calculating a first difference between the first target reflectance value and the first threshold value;
for a second sub-pixel of the group of sub-pixels:
determining that the second sub-pixel is currently in an open state;
determining a second target reflectance value for the second sub-pixel; and
generating an adjusted second target reflectance value by altering the second target reflectance value by an amount corresponding to the first difference.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
for the second sub-pixel:
determining that the adjusted second target reflectance value is above the first threshold value and below the second threshold value;
determining that the adjusted second target reflectance value is closer to the first threshold value than the second threshold value;
setting a second reflectance for the second sub-pixel to the first threshold value; and
calculating a second difference between the adjusted second target reflectance value and the first threshold value.

### Claim 3 (depends on 1)

The method of claim 1, further comprising:
for the second sub-pixel:
determining that the adjusted second target reflectance value is above the second threshold value; and
setting a second reflectance of the second sub-pixel to the adjusted second target reflectance value.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
updating a memory storing sub-pixel state data to indicate that the first sub-pixel has entered a closed state.

### Claim 5 (depends on 1)

The method of claim 1, wherein determining that the first sub-pixel is currently in an open state comprises checking a sub-pixel state database stored in a memory for a current state of the first sub-pixel.

### Claim 6

A method of driving a group of sub-pixels of a display device, the method comprising:
determining that a first sub-pixel of the group of sub-pixels is currently in an open state;
determining a first target reflectance value for the first sub-pixel;
determining that the first target reflectance value is greater than a first threshold value and less than a second threshold value;
determining that the first target reflectance value is closer to the second threshold value than the first threshold value;
setting a first reflectance of the first sub-pixel to the second threshold value in response to determining that the first target reflectance value is closer to the second threshold value than the first threshold value;
calculating a first difference between the second threshold value and the first target reflectance value; and
decreasing a second target reflectance value of a second sub-pixel in the group of sub-pixels by an amount related to the first difference.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
for the second sub-pixel:
determining that the second sub-pixel is currently in an open state;
generating an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determining that the adjusted second target reflectance value is closer to the first threshold value than the second threshold value;
setting a second reflectance for the second sub-pixel to the first threshold value; and
calculating a second difference between the adjusted second target reflectance value and the first threshold value.

### Claim 8 (depends on 7)

The method of claim 7, further comprising:
updating a memory storing sub-pixel state data to indicate that the second subpixel has entered a closed state.

### Claim 9 (depends on 6)

The method of claim 6, wherein determining that the first sub-pixel is currently in an open state further comprises checking a sub-pixel state database stored in a memory for a current state of the first sub-pixel.

### Claim 10 (depends on 6)

The method of claim 6, further comprising:
for the second sub-pixel:
determining that the second sub-pixel is currently in an open state;
generating an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determining that the adjusted second target reflectance value is above the second threshold value; and
setting the second sub-pixel to the adjusted second target reflectance value.

### Claim 11 (depends on 6)

The method of claim 6, further comprising:
for the second sub-pixel:
determining that the second sub-pixel is currently in an open state;
generating an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determining that the adjusted second target reflectance value is closer to the second threshold value than the first threshold value;
setting a second reflectance for the second sub-pixel to the second threshold value; and
calculating a second difference between the second threshold value and the adjusted second target reflectance value.

### Claim 12 (depends on 6)

The method of claim 6, further comprising:
for the second sub-pixel:
generating an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determining that the adjusted second target reflectance value is below a minimum reflectance value;
setting a second reflectance for the second sub-pixel to the minimum reflectance value;
calculating a second difference between the minimum reflectance value and the adjusted second target reflectance value; and
decreasing a third target reflectance value of a third sub-pixel in the group of sub-pixels by an amount related to the second difference.

### Claim 13 (depends on 6)

The method of claim 6, further comprising:
selecting the second sub-pixel having a same color as the first sub-pixel.

### Claim 14 (depends on 6)

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

### Claim 15

A display device comprising:
a group of sub-pixels comprising a first sub-pixel; and
a display controller comprising:
an input line for receiving data relating to a target reflectance of the group of sub-pixels; and
a plurality of output lines coupled to the group of sub-pixel to control reflectance values of the group of sub-pixels;
wherein the display controller is configured to:
determine that the first sub-pixel of the group of sub-pixels is currently in an open state;
receive, via the input line, a first target reflectance value for the first subpixel;
determine that the first target reflectance value is closer to a second threshold value than a first threshold value;
control the first sub-pixel via one of the plurality of output lines to set the first reflectance of the first sub-pixel to the second threshold value in response to determining that the first target reflectance value is closer to the second threshold value than the first threshold value;
calculate a first difference between the second threshold value and the first target reflectance value; and
decrease a second target reflectance value of a second sub-pixel in the group of sub-pixels by an amount corresponding to the first difference.

### Claim 16 (depends on 15)

The display device of claim 15, wherein the display controller is further configured to:
determine that the second sub-pixel is currently in an open state;
receive, via the input line, a second target reflectance value for the second sub-pixel;
generate an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determine that the adjusted second target reflectance value is closer to the first threshold value than the second threshold value;
control the second sub-pixel via a second one of the plurality of output lines to set a second reflectance of the second sub-pixel to the first threshold value; and
calculate a second difference between the adjusted second target reflectance value and the first threshold value.

### Claim 17 (depends on 16)

The display device of claim 16, further comprising:
a memory coupled to the display controller, the memory including sub-pixel state data indicating current states of individual sub-pixels of the group of sub-pixels;
wherein the display controller is further configured to:
determine that the first sub-pixel is currently in an open state by checking the sub pixel state data stored in the memory for a current state of the first subpixel; and
update the sub-pixel state data to indicate that the second sub-pixel has entered a closed state.

### Claim 18 (depends on 15)

The display device of claim 15, wherein the display controller is further configured to:
determine that the second sub-pixel is currently in an open state;
receive, via the input line, a second target reflectance value for the second sub-pixel;
generate an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determine that the adjusted second target reflectance value is closer to the second threshold value than the first threshold value;
control the second sub-pixel via a second one of the plurality of output lines to set a second reflectance of the second sub-pixel to the second threshold value; and
calculate a second difference between the second threshold value and the adjusted second target reflectance value.

### Claim 19 (depends on 15)

The display device of claim 15, wherein the display controller is further configured to:
determine that the second sub-pixel is currently in an open state;
receive, via the input line, a second target reflectance value for the second sub-pixel;
generate an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determine that the adjusted second target reflectance value is above the second threshold value; and
control the second sub-pixel via a second one of the plurality of output lines to set a second reflectance of the second sub-pixel to the adjusted second target reflectance value.

### Claim 20 (depends on 15)

The display device of claim 15, wherein the display controller is further configured to:
receive, via the input line, a second target reflectance value for the second sub-pixel;
generate an adjusted second target reflectance value by decreasing the second target reflectance value by the amount corresponding to the first difference;
determine that the adjusted second target reflectance value is below a minimum reflectance value;
control the second sub-pixel via a second one of the plurality of output lines to set a second reflectance of the second sub-pixel to the minimum reflectance value;
calculate a second difference between the minimum reflectance value and the adjusted second target reflectance value; and
decrease a third target reflectance value of a third sub-pixel in the group of sub-pixels by an amount corresponding to the second difference.