Correction schemes for display panel sensing

• US 10,564,774 B1
• Filed: 06/14/2018
• Issued: 02/18/2020
• Est. Priority Date: 04/07/2017
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chang, Sun-Il, Cho, Myung-Je, Brahma, Kingsuk, Richmond, Jesse A., Kim, Hyunsoo, Shen, Shiping, Hwang, Injae, Zhang, Rui, Gao, Shengkui, Lin, Hung Sheng, Ryu, Jie Won, Tan, Junhua, Nho, Hyunwoo
• Primary Examiner(s): Lubit, Ryan A
• Application Number:
  US16/008,997
• Time in Patent Office: 614 Days
• CPC Class Codes: G02F 1/133509 Filters, e.g. light shielding masks
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/0686 with two or more screen areas displaying information with different brightness or colours
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]

Abstract

Methods for mitigation of sensing error effects in display panels are disclosed. Display panels, such as pixel-based panels, may have circuitry to sense the luminance values, compare measurements with target luminance values, and provide corrections. Sensing errors, such as ones caused by sensor hysteresis and thermal fluctuations, may lead to overcorrections and visible artifacts. Mitigations schemes discussed herein include filtering of sensed signal with low pass filters, partial correction strategies, and feedforward sensing schemes. Circuitry that implements these schemes are also discussed.

Claims

1. An electronic device comprising:

a display panel comprising at least an array of pixels;

sensing circuitry that measures a luminance of the array of pixels and produces sensing data from the measurement;

filtering circuitry that produces filtered sensing data from the sensing data, wherein the filtering circuitry applies a two-dimensional low pass filter;

data processing circuitry that receives the filtered sensing data and produces a correction map; and

a display driver configured to receive an image data and the correction map and adjust the luminance of the array of pixels and cause the display panel to display an image based on the image data and the correction map.

2. The electronic device of claim 1, wherein the two-dimensional low pass filter comprises a box filter, a triangular filter, or a Gaussian filter.

3. The electronic device of claim 1, wherein the two-dimensional low pass filter comprises a cut-off frequency substantially between 0.1 and 1.5 cycles per degree.

4. The electronic device of claim 1, wherein the two-dimensional low pass filter comprises a cut-off frequency that is above a frequency of thermal error and below a frequency of hysteresis error.

5. The electronic device of claim 4, wherein the hysteresis error comprises a trap error or a de-trap error.

6. A closed-loop method to filter sensed data for display panel correction comprising:

receiving image data;

receiving sensing data associated with a display panel from sensing circuitry coupled to the display panel;

filtering the sensing data to produce filtered sensed data consisting of low-frequency content from the sensing data;

converting the filtered sensed data to display correction data;

combining the display correction data with the image data to produce corrected image data; and

causing the display panel to display the corrected image data.

7. The method of claim 6, wherein converting the filtered sensed data to the display correction data comprises converting luminance units to display voltage units.

8. The method of claim 6, wherein filtering the sensing data comprises performing a convolution between a two-dimensional low-pass filter and the sensed data.

9. The method of claim 8, wherein the two-dimensional low-pass filter comprises a combination of an even number of two-dimensional box filters.

10. The method of claim 6, wherein converting the filtered sensed data comprises a look-up table.

11. The method of claim 6, wherein converting the filtered sensed data comprises:

producing a total correction map based on a difference between the filtered sensed data and the image data; and

producing the display correction data based on the total correction map and a step limit, wherein the step limit is based on a perception threshold.