Electronic Device Display with a Backlight

• US 20200133068A1
• Filed: 06/12/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Lu, Shin-Ying, Xu, Daming, Gorkhali, Suraj P., Herranz, Adria Fores, Son, Mookyung, Suh, Heesang, Yin, Victor H., Holsteen, Aaron L., Li, Xiaokai, Ge, Zhibing
• Granted Patent: US 10,866,458 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/0088 of the light guide or other optical sheets in the package
• CPC Class Codes: G02B 6/009 of the light source in the package G02B6/0021 takes precedence
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/13452 Conductors connecting driver circuitry and terminals of panels
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01R 12/62 connecting to rigid printed circuits or like structures
• CPC Class Codes: H01R 4/04 using electrically conductive adhesives
• CPC Class Codes: H05K 1/0281 Reinforcement details thereof
• CPC Class Codes: H05K 1/118 : specially for flexible printed circuits, e.g. using folded portions
• CPC Class Codes: H05K 1/147 : at least one of the printed circuits being bent or folded, e.g. by using a flexible printed circuit H05K1/148 takes precedence
• CPC Class Codes: H05K 1/189 : characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/094 : Array of pads or lands differing from one another, e.g. in size, pitch, thickness; Using different connections on the pads using different types of conductors H05K2201/0391
• CPC Class Codes: H05K 2201/10106 : Light emitting diode [LED]
• CPC Class Codes: H05K 2201/10136 : Liquid Crystal display [LCD]
• CPC Class Codes: H05K 2201/10674 : Flip chip
• CPC Class Codes: H05K 3/361 : Assembling flexible printed circuits with other printed circuits

Abstract

An electronic device may include display layers such as liquid crystal display layers and a backlight unit that provides illumination for the display layers. The backlight unit may include light-emitting diodes that emit light into the edge of a light guide film. To minimize the inactive area of the display, the light-emitting diodes may be tightly spaced to approximate a line light source instead of point light sources. Color and/or luminance compensation layers may be incorporated at various locations within the backlight structures to ensure that the backlight provided to the display layers is homogenous. A thin-film transistor layer of the display may be coupled to a printed circuit board by a flexible printed circuit. The flexible printed circuit may have additional solder mask layers to improve robustness, may include encapsulation, and may have traces with a varying pitch.

Claims

1. A method of calibrating an electronic device display, the method comprising:

using an image sensor, capturing an image of an electronic device display while the electronic device display displays a test image;

determining representative values based on the image of the electronic device display, wherein each representative value is associated with a respective portion of the electronic device display; and

based on the representative values, determining a compensation value for each display pixel in the electronic device display.

2. The method defined in claim 1, wherein determining the compensation value for each display pixel in the electronic device display comprises using extrapolation to determine the compensation value for each display pixel in the electronic device display.

3. The method defined in claim 1, wherein the electronic device display is configured to display an entirely white image as the test image.

4. The method defined in claim 1, wherein each respective portion of the electronic device display includes more than one display pixel and less than all of the display pixels in the electronic device display.

5. The method defined in claim 1, wherein determining the representative values comprises summing image signals from more than one imaging pixel in the image sensor.

6. The method defined in claim 1, wherein determining the representative values comprises averaging image signals from more than one imaging pixel in the image sensor.

7. An electronic device comprising:

an array of display pixels;

a backlight unit that provides backlight for the array of display pixels;

display driver circuitry coupled to the array of display pixels;

control circuitry that includes multiplication circuitry and a per-pixel gain table, wherein the control circuitry is configured to receive image data, modify the image data using the multiplication circuitry and the per-pixel gain table, and provide the modified image data to the display driver circuitry and wherein the display driver circuitry is configured to provide the modified image data to the array of display pixels.

8. The electronic device defined in claim 7, wherein the image data includes a respective pixel value for each pixel in the array of display pixels and wherein the per-pixel gain table includes a respective compensation factor for each pixel in the array of display pixels.

9. The electronic device defined in claim 8, wherein the control circuitry is configured to multiply each pixel value by its respective compensation factor using the multiplication circuitry to modify the image data.

10. The electronic device defined in claim 8, wherein the compensation factors in the per-pixel gain table compensate for variations in the backlight provided by the backlight unit.

11. An electronic device comprising:

an array of display pixels;

display driver circuitry configured to provide image data to the array of display pixels; and

control circuitry including a content processor that is configured to;

receive uncorrected pixel data for a current frame; and

generate modified pixel data for the current frame based on the uncorrected pixel data for the current frame and pixel data for a previous frame using at least one look-up table.

12. The electronic device defined in claim 11, wherein the control circuitry is configured to provide the modified pixel data to the display driver circuitry to be displayed on the array of display pixels.

13. The electronic device defined in claim 11, wherein the uncorrected pixel data includes black pixel data for a first display pixel and wherein the pixel data for the previous frame includes white pixel data for the first display pixel.

14. The electronic device defined in claim 13, wherein the white pixel data for the first display pixel includes at least one sub-pixel value that is truncated.

15. The electronic device defined in claim 14, wherein the at least one sub-pixel value is truncated for a white point adjustment.

16. The electronic device defined in claim 13, wherein the white pixel data for the first display pixel includes a first value for a first sub-pixel, a second value for a second sub-pixel value that is lower than the first value, and a third value for a third sub-pixel that is lower than the first value.

17. The electronic device defined in claim 16, wherein the uncorrected pixel data for the current frame has a value of 0 for the first, second, and third sub-pixels, and wherein the modified pixel data for the current frame includes a fourth value for the first sub-pixel that is equal to 0, a fifth value for the second sub-pixel that is greater than 0, and a sixth value for the third sub-pixel that is greater than 0.

18. The electronic device defined in claim 13, wherein the white pixel data for the first display pixel includes a first value for a green sub-pixel, a second value for a red sub-pixel value that is lower than the first value, and a third value for a blue sub-pixel that is lower than the first value.

19. The electronic device defined in claim 18, wherein the uncorrected pixel data for the current frame has a value of 0 for the green, red, and blue sub-pixels, and wherein the modified pixel data for the current frame includes a fourth value for the green sub-pixel that is equal to 0, a fifth value for the red sub-pixel that is greater than 0, and a sixth value for the blue sub-pixel that is greater than 0.

20. The electronic device defined in claim 11, wherein generating the modified pixel data for the current frame based on the uncorrected pixel data for the current frame and the pixel data for the previous frame using the at least one look-up table comprises increasing target pixel values for red and blue sub-pixels in pixels undergoing white-to-black transitions.