System and method for achieving optimal display contrast in a mobile communication device

• US 20020054010A1
• Filed: 11/05/2001
• Published: 05/09/2002
• Est. Priority Date: 11/06/2000
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Tran, Phat H., Lowles, Robert J., Reksnis, Marek
• Granted Patent: US 7,209,150 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G06F 3/04897 Special input arrangements or commands for improving display capability
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: H04M 1/22 Illumination; Arrangements for improving the visibility of characters on dials
• CPC Class Codes: H04M 1/72448 with means for adapting the functionality of the device according to specific conditions

Abstract

A system and method for achieving optimal display contrast in a mobile communication device is provided. The system includes a memory device, a processor, a display driver, and a display. A user contrast setting is stored in the memory device, wherein the user contrast setting is selected from a range of user contrast settings. The processor includes an operating system that is configured to retrieve the user contrast setting from the memory device, convert the user contrast setting into a hardware contrast setting, and save the hardware contrast setting to a memory location. The display driver retrieves the hardware contrast setting from the memory location and generates a contrast control voltage as a function of the hardware contrast setting. The display is coupled to the contrast control voltage and has a variable contrast ratio, wherein the variable contrast ratio of the display is controlled by the contrast control voltage.

Claims

1. A mobile device, comprising:

a user contrast setting stored in a memory device, wherein the user contrast setting is selected from a range of user contrast settings;

a processor having an operating system configured to retrieve the user contrast setting from the memory device, convert the user contrast setting into a hardware contrast setting, and save the hardware contrast setting to a memory location;

a display driver that retrieves the hardware contrast setting from the memory location and generates a contrast voltage as a function of the hardware contrast setting; and

a display coupled to the contrast voltage and having a variable contrast ratio, wherein the variable contrast ratio of the display is controlled by the contrast voltage.

2. The mobile device of claim 1, wherein the display is a liquid crystal display.

3. The mobile device of claim 1, wherein the user contrast setting is an integer.

4. The mobile device of claim 1, wherein the hardware contrast setting is an integer.

5. The mobile device of claim 1, wherein the user contrast setting selected from the middle of the range of user contrast settings results in an optimal contrast ratio for the display.

6. The mobile device of claim 1, wherein the highest user contrast setting that may be selected from the range of user contrast settings results in a pre-selected high contrast ratio for the display.

7. The mobile device of claim 1, wherein the lowest user contrast setting that may be selected from the range of user contrast settings results in a pre-selected low contrast ratio for the display.

8. The mobile device of claim 1, wherein the display driver includes the memory location to which the hardware contrast setting is stored.

9. The mobile device of claim 1, further comprising:

a contrast offset stored in the memory device, wherein the contrast offset is used by the operating system to convert the user contrast setting into a hardware contrast setting.

10. The mobile device of claim 9, wherein the contrast offset is an integer.

11. The mobile device of claim 9, wherein the contrast offset is calibrated and stored in the memory device by a mobile device manufacturer.

12. The mobile device of claim 1, further comprising:

a contrast scale stored in the memory device, wherein the contrast scale is used by the operating system to convert the user contrast setting into a hardware contrast setting.

13. The mobile device of claim 12, wherein the contrast scale is an integer.

14. The mobile device of claim 12, wherein the contrast scale is calibrated and stored in the memory device by a mobile device manufacturer.

15. The mobile device of claim 1, wherein the display includes a backlight that adds luminance to the display when activated, and further comprising:

a backlight adjustment stored in the memory device, wherein the backlight adjustment increments or decrements the user contrast setting to compensate for the luminance from the backlight.

16. The mobile device of claim 15, wherein the backlight adjustment is an integer.

17. The mobile device of claim 15, wherein the backlight adjustment is calibrated and stored in the memory device by a mobile device manufacturer.

18. The mobile device of claim 1, further comprising:

an input device coupled to the processor that enables a mobile device user to input the user contrast setting;

wherein the operating system is further configured to receive the user contrast setting from the input device and save the user contrast setting to the memory device.

19. The mobile device of claim 18, wherein the input device is a keypad.

20. The mobile device of claim 18, wherein the input device is a thumbwheel.

21. The mobile device of claim 18, wherein the input device is a touchscreen

22. The mobile device of claim 1, further comprising:

a contrast offset stored in the memory device; and

a contrast scale stored in the memory device;

wherein the operating system converts the user contrast setting into the hardware contrast setting using the contrast offset and the contrast scale.

23. The mobile device of claim 22, wherein the operating system converts the user contrast setting into the hardware contrast setting using the equation HCS=S*USC+O, where HCS is the hardware contrast setting, S is the contrast scale, UCS is the user contrast setting, and O is the contrast offset.

25. The method of claim 24, comprising the additional step of:

receiving the user contrast setting from a mobile device user.

26. The method of claim 24, comprising the additional step of:

storing the hardware contrast setting in a memory location.

27. The method of claim 24, wherein the user contrast setting is selected from a range of user contrast settings having a middle setting, and comprising the additional step of:

calibrating the contrast offset such that the middle setting in the range of user contrast settings corresponds to an optimal contrast ratio for the LCD.

28. The method of claim 27, wherein the calibration step is performed by a mobile device manufacturer.

29. The method of claim 24, wherein the user contrast setting is selected from a range of user contrast settings, and comprising the additional step of:

calibrating the contrast scale such that the range of user contrast settings falls between a pre-selected low contrast ratio for the LCD and a pre-selected high contrast ratio for the LCD.

30. The method of claim 29, wherein the calibration step is performed by a mobile device manufacturer.

31. The method of claim 24, comprising the additional steps of:

determining whether an LCD backlight is on; and

if the LCD backlight is on, then incrementing or decrementing the user contrast setting using a backlight adjustment value.

32. The method of claim 31, comprising the additional step of:

calibrating the backlight adjustment value such that the contrast ratio of the LCD when the LCD backlight is on is substantially the same as the contrast ratio of the LCD when the LCD backlight is off.

33. The method of claim 32, wherein the calibration step is performed by a mobile device manufacturer.

35. The method of claim 34, wherein the step of converting the user contrast setting into a hardware contrast setting is performed using the equation HCS=S*USC+O, where HCS is the hardware contrast setting, S is the contrast scale, UCS is the user contrast setting, and O is the contrast offset.

37. The method of claim 36, wherein the contrast offset value is initialized to zero.

38. The method of claim 36, wherein the contrast offset value is initialized to a predetermined value.

39. The method of claim 36, comprising the additional step of:

taking an image of the LCD, wherein the image is used to determine the contrast ratio of the LCD.

40. The method of claim 36, wherein the step of incrementing the contrast offset value until the contrast ratio reaches a peak value is performed by a method comprising the steps of:

determining whether the contrast ratio is higher than any previously measured values;

if the contrast ratio is higher than any previously measured values, then saving the contrast offset value and contrast ratio to a memory location, incrementing the contrast offset value, and determining an updated contrast ratio;

if the contrast ratio is not higher than any previously measured values, then determining whether the contrast ratio is a first measured value;

if the contrast ratio if the first measured value, then incrementing the contrast offset value and determining an updated contrast ratio; and

if the contrast ratio is not the first measured value, then setting the contrast offset on the mobile device to the saved contrast offset value.

41. The method of claim 36, wherein the step of incrementing the contrast offset value until the contrast ratio reaches a peak value is performed by a method comprising the steps of:

determining whether the contrast ratio is higher than any previously measured values;

if the contrast ratio is higher than any previously measured values, then saving the contrast offset value and contrast ratio to a memory location, incrementing the contrast offset value, and determining an updated contrast ratio;

if the contrast ratio is not higher than any previously measured values, then determining whether the contrast ratio is a first measured value;

if the contrast ratio is the first measured value, then incrementing the contrast offset value and determining an updated contrast ratio;

if the contrast ratio is not the first measured value, then determining whether the contrast ratio is substantially less than the saved contrast ratio;

if the contrast ratio is not substantially less than the saved contrast ratio, then incrementing the contrast offset value and determining an updated contrast ratio; and

if the contrast ratio is substantially less than the save contrast ratio, then setting the contrast offset value on the mobile device to the saved contrast offset value.

24. A method of controlling the contrast ratio of a liquid crystal display (LCD) in a mobile device, comprising the steps of:

storing a user contrast setting in a memory device;

converting the user contrast setting into a hardware contrast setting using a contrast offset and a contrast scale; and

converting the hardware contrast setting into a contrast voltage using a display driver, wherein the contrast voltage controls the contrast ratio of the LCD.

34. A method of controlling the contrast ratio of a liquid crystal display (LCD) in a mobile device, comprising the steps of:

storing a user contrast setting in a memory device;

storing a contrast offset in the memory device;

storing a contrast scale in the memory device;

converting the user contrast setting into a hardware contrast setting using the contrast offset and the contrast scale; and

converting the hardware contrast setting into a contrast voltage using a display driver, wherein the contrast voltage controls the contrast ratio of the LCD.

36. A method for calibrating a contrast offset value for a liquid crystal display (LCD) contrast control system in a mobile device, comprising the steps of:

adjusting a user contrast setting on the mobile device to a desired optimal value;

initializing the contrast offset value;

determining a contrast ratio of the LCD; and

incrementing the contrast offset value until the contrast ratio reaches a peak value.

42. A method for calibrating a contrast scale value for a liquid crystal display (LCD) contrast control system in a mobile device, comprising the steps of:

adjusting a user contrast setting on the mobile device to a highest setting;

initializing the contrast scale value;

determining a contrast ratio of the LCD;

incrementing or decrementing the contrast scale value until the contrast ratio reaches a desired maximum value.

43. The method of claim 42, wherein the contrast scale value is incremented or decremented by a scale calibration step value.

44. The method of claim 43, comprising the additional step of:

initializing the calibration step value to a pre-selected maximum step value.

45. The method of claim 43, wherein the scale calibration step value is reduced each time the contrast scale value is incremented or decremented.

46. The method of claim 45, wherein the scale calibration step is reduced by one half each time the contrast value is incremented or decremented.

47. The method of claim 42, wherein the step of incrementing or decrementing the contrast scale value until the contrast ratio reaches a desired maximum value is performed by a method comprising the following steps:

determining whether the contrast ratio of the LCD is substantially equivalent to a desired maximum value;

if the contrast ratio is substantially equivalent to the desired maximum value, then saving the contrast scale value to the mobile device;

if the contrast ratio is not substantially equivalent to the desired maximum, then determining whether the contrast ratio of the LCD is above or below the desired maximum value;

if the contrast ratio is not substantially equivalent to the desired maximum, and if the contrast ratio of the LCD is above the desired maximum value, then decrementing the contrast scale value until the contrast ratio reached the desired maximum value; and

if the contrast ratio is not substantially equivalent to the desired maximum, and if the contrast ratio of the LCD is below the desired maximum value, then incrementing the contrast scale value until the contrast ratio reaches the desired maximum value.

48. The method of claim 42, wherein the step of incrementing or decrementing the contrast scale value until the contrast ratio reaches a desired maximum value is performed by a method comprising the following steps:

determining whether the contrast ratio of the LCD is within a pre-selected tolerance range of a desired maximum value;

if the contrast ratio is within the pre-selected tolerance range of the desired maximum value, then saving the contrast scale value to the mobile device;

if the contrast ratio is not within the pre-selected tolerance range of the desired maximum value, then determining whether the contrast ratio of the LCD is above or below the desired maximum value;

if the contrast ratio is not within the pre-selected tolerance range of the desired maximum value, and if the contrast ratio of the LCD is above the desired maximum value, then decrementing the contrast scale value until the contrast ratio reached the desired maximum value; and

if the contrast ratio is not within the pre-selected tolerance range of the desired maximum value, and if the contrast ratio of the LCD is below the desired maximum value, then incrementing the contrast scale value until the contrast ratio reaches the desired maximum value.

49. The method of claim 42, wherein the contrast scale value is initialized to zero.

50. The method of claim 42, comprising the additional step of:

taking an image of the LCD, wherein the image of the LCD is used to determine the contrast ratio.

51. A method for calibrating a backlight adjustment value for a liquid crystal display (LCD) contrast control system in a mobile device, comprising the steps of:

turning on a LCD backlight;

initialize the backlight adjustment value;

adjusting a user contrast setting on the mobile device to a pre-calibrated optimal value;

determining a contrast ratio of the LCD;

incrementing the backlight adjustment value until the contrast ratio reaches a peak value.

52. The method of claim 51, wherein the backlight adjustment value is initialized to zero.

53. The method of claim 51, comprising the additional step of:

taking an image of the LCD, wherein the image is used to determine the contrast ratio of the LCD.

54. The method of claim 51, wherein the step of incrementing the backlight adjustment value until the contrast ratio reaches a peak value is performed by a method comprising the steps of:

determining whether the contrast ratio is higher than any previously measured values;

if the contrast ratio is higher than any previously measured values, then saving the backlight adjustment value and contrast ratio to a memory location, incrementing the backlight adjustment value, and determining an updated contrast ratio;

if the contrast ratio is not higher than any previously measured values, then determining whether the contrast ratio is a first measured value;

if the contrast ratio is the first measured value, then incrementing the backlight adjustment value and determining an updated contrast ratio; and

if the contrast ratio is not the first measured value, then setting the backlight adjustment value on the mobile device to the saved backlight adjustment value.

55. The method of claim 51, wherein the step of incrementing the backlight adjustment value until the contrast ratio reaches a peak value is performed by a method comprising the steps of:

determining whether the contrast ratio is higher than any previously measured values;

if the contrast ratio is higher than any previously measured values, then saving the backlight adjustment value and contrast ratio to a memory location, incrementing the backlight adjustment value, and determining an updated contrast ratio;

if the contrast ratio is not higher than any previously measured values, then determining whether the contrast ratio is a first measured value;

if the contrast ratio if the first measured value, then incrementing the backlight adjustment value and determining an updated contrast ratio;

if the contrast ratio is not the first measured value, then determining whether contrast ratio is substantially less than the saved contrast ratio;

if the contrast ratio is not substantially less than the saved contrast ratio, then incrementing the backlight adjustment value and determining an updated contrast ratio; and

if the contrast ratio is substantially less than the save contrast ratio, then setting the backlight adjustment value on the mobile device to the saved backlight adjustment.