White point uniformity techniques for displays

• US 9,940,879 B2
• Filed: 10/05/2011
• Issued: 04/10/2018
• Est. Priority Date: 10/05/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Gettemy, Shawn Robert, Wurzel, Joshua Grey, Guillou, Jean-Pierre Simon, Xu, Ming, Doyle, David Andrew
• Primary Examiner(s): Ketema, Benyam
• Application Number:
  US13/253,739
• Publication Number:
  US 20130088522A1
• Time in Patent Office: 2,379 Days
• Field of Search: 345690, 345102
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

The present disclosure generally relates to systems and techniques for calibrating displays to improve the white point uniformity between similar type devices. In one embodiment, a backlight includes multiple strings of LEDs, where each string is driven by a separate driver, or driver channel. Each string may be separately tested at a base current to determine its emitted chromaticity, and values indicative of the emitted chromaticities may be stored within the backlight as calibration values. The calibration values may then be used to determine the driving strength for each string that allows the display to produce the target white point when the light from the strings is mixed. Further, in certain embodiments, adjustments also may be made to the LCD panel based on the emitted chromaticities at the base current.

Claims

1. A display, comprising:

a first string of first light emitting diodes;

a second string of second light emitting diodes;

a storage containing calibration values representing a first emitted chromaticity of the first string when driven at a base current in isolation and a second emitted chromaticity of the second string when driven at the base current in isolation; and

a controller configured to determine a first driving strength for the first string and a second driving strength for the second string based on the calibration values, wherein the calibration values comprise a first set of chromaticity coordinates representing the first emitted chromaticity and a second set of chromaticity coordinates representing the second emitted chromaticity.

2. A display, comprising:

a first string of first light emitting diodes;

a second string of second light emitting diodes;

a storage containing calibration values representing a first emitted chromaticity of the first string when driven at a base current in isolation and a second emitted chromaticity of the second string when driven at the base current in isolation; and

a controller configured to determine a first driving strength for the first string and a second driving strength for the second string based on the calibration values, wherein the calibration values comprise a set of chromaticity coordinates representing a mixed chromaticity of the first emitted chromaticity and the second emitted chromaticity.

3. A method, comprising:

storing, in a storage of an electronic device comprising a backlight, calibration values representing emitted chromaticities for each of a plurality of strings of light emitting diodes driven at a base current in isolation; and

configuring a controller of the electronic device to determine individual driving strengths for each of the plurality of strings based on the calibration values, wherein the individual driving strengths are configured to align a mixed chromaticity for the plurality of strings with a target white point, wherein storing calibration values comprises storing sets of chromaticity coordinates and brightness values for each of the emitted chromaticities.