TECHNIQUE FOR ADJUSTING A BACKLIGHT DURING A BRIGHTNESS DISCONTINUITY

• US 20090002564A1
• Filed: 06/24/2008
• Published: 01/01/2009
• Est. Priority Date: 06/26/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Wei, Barnhoefer, Ulrich T., Yao, Wei H.
• Granted Patent: US 8,648,781 B2
• Time in Patent Office: Days
• US Class Current: 348/687
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2310/0232 Special driving of display border areas
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

Embodiments of a system that includes one or more integrated circuits are described. During operation, the system receives a sequence of video images, and calculates brightness metrics associated with the video images in the sequence of video images. Then, the system determines an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scales brightness values of a given video image in the sequence of video images based on a given brightness metric associated with the given video image. Next, the system changes the intensity setting and scaling the brightness values when there is a discontinuity in the brightness metrics between two adjacent video images in the sequence of video images.

Claims

1. A system, comprising one or more integrated circuits, wherein the one or more integrated circuits are configured to:

receive a sequence of video images;

calculate brightness metrics associated with the video images in the sequence of video images;

determine an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scale brightness values of a given video image in the sequence of video images based on a given brightness metric associated with the given video image; and

change the intensity setting and scale the brightness values when there is a discontinuity in the brightness metrics between two adjacent video images in the sequence of video images.

2. The system of claim 1, wherein the given brightness metric includes a histogram of brightness values in the given video image.

3. The system of claim 1, wherein in the discontinuity includes a change in a maximum brightness value that exceeds a predetermined value.

4. The system of claim 1, wherein the one or more integrated circuits are further configured to apply a portion of changes in the intensity setting and a corresponding portion of the scaling of the brightness values on video-image basis in the sequence of video images;

and

wherein the portion is selected such that differences between adjacent video images is less than a predetermined value unless there is the discontinuity in the brightness metrics, in which case, the portion is selected such that differences between adjacent video images is greater than a predetermined value.

5. The system of claim 4, wherein a rate of change of the portion corresponds to a size of the discontinuity in the brightness metrics.

6. The system of claim 4, wherein the portion is applied using a temporal filter.

7. The system of claim 1, wherein the determined intensity setting of the light source for the given video image reduces power consumption of the light source.

8. The system of claim 1, wherein the scaling of the brightness values is determined on a pixel-by-pixel basis.

9. The system of claim 1, wherein the video image includes a frame of video.

10. The system of claim 1, wherein the brightness values are scaled based on a dynamic range of a mechanism that attenuates coupling of light from a light source to the display that is configured to display the video image.

11. The system of claim 1, wherein the light source comprises a light-emitting diode or a fluorescent lamp.

12. A system, comprising one or more integrated circuits, wherein the one or more integrated circuits are configured to:

identify a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

determine a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scale brightness values of the second video image based on a brightness metric associated with the second video image; and

apply the change in the intensity setting and scale the brightness values.

13. A system, comprising:

an input node configured to receive video signals associated with a sequence of video images;

an extraction circuit electrically coupled to the input interface, the extraction circuit operative to calculate brightness metrics associated with the sequence of video images based on the received video signals;

an analysis circuit electrically coupled to the extraction circuit, the analysis circuit configured to analyze the brightness metrics to identify a discontinuity associated with adjacent video images, including a first video image and a second video image, in the sequence of video images;

an adjustment circuit electrically coupled to the analysis circuit, the adjustment circuit configured to adjust a brightness of pixels in the second video image and to determine an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images; and

an output node electrically coupled to the adjustment circuit, the output node configured to output the video signals.

14. A method for adjusting a brightness of a video image, comprising:

identifying a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

determining a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scaling brightness values of the second video image based on a brightness metric associated with the second video image; and

applying the change in the intensity setting and the scaling of the brightness values.

15. A method for adjusting a brightness of a video image, comprising:

receiving a sequence of video images;

calculating brightness metrics associated with the video images in the sequence of video images;

determining an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scaling brightness values of a given video image in the sequence of video images based on a given brightness metric associated with the given video image; and

changing the intensity setting and scaling the brightness values when there is a discontinuity in the brightness metrics between two adjacent video images in the sequence of video images.

16. A computer-program product for use in conjunction with a computer system, the computer-program product comprising a computer-readable storage medium and a computer-program mechanism embedded therein for scaling a brightness of a video image, the computer-program mechanism comprising:

instructions for identifying a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

instructions for determining a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and for scaling brightness values of the second video image based on a brightness metric associated with the second video image; and

instructions for applying the change in the intensity setting and the scaling of the brightness values.

17. A computer system to scale a brightness of a video image, comprising:

a processor;

memory;

a program module, wherein the program module is stored in the memory and configurable to be executed by the processor, the program module including;

instructions for identifying a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

instructions for determining a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and for scaling of brightness values of the second video image based on a brightness metric associated with the second video image; and

instructions for applying the change in the intensity setting and the scaling of the brightness values.

18. A computer system configured to scale a brightness of a video image, comprising:

a processor;

a memory;

an instruction fetch unit within the processor configured to fetch;

instructions for identifying a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

instructions for determining a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and for scaling of brightness values of the second video image based on a brightness metric associated with the second video image; and

instructions for applying the change in the intensity setting and the scaling of the brightness values; and

an execution unit within the processor configured to execute the instructions for identifying the discontinuity, the instructions for determining the change in the intensity setting and for scaling of the brightness values, and the instructions for applying the intensity setting and the scaling of the brightness values.

19. An integrated circuit, comprising one or more sub-circuits, wherein the one or more sub-circuits are configured to:

receive a sequence of video images;

calculate brightness metrics associated with the video images in the sequence of video images;

determine an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scale brightness values of a given video image in the sequence of video images based on a given brightness metric associated with the given video image; and

change the intensity setting and scale the brightness values when there is a discontinuity in the brightness metrics between two adjacent video images in the sequence of video images.

20. An integrated circuit, comprising one or more sub-circuits, wherein the one or more sub-circuits are configured to:

identify a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

determine a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scale brightness values of the second video image based on a brightness metric associated with the second video image; and

apply the change in the intensity setting and scale the brightness values.

21. A portable device, comprising:

a display;

a light source configured to output light;

an attenuation mechanism configured to modulate the output light incident on the display, the display configured to display a video image; and

one or more integrated circuits, wherein the one or more integrated circuits are configured to;

identify a discontinuity in brightness metrics associated with adjacent video images, including a first video image and a second video image, in a sequence of video images;

determine a change in an intensity setting of a light source, which illuminates a display that is configured to display the sequence of video images, and scale brightness values of the second video image based on a brightness metric associated with the second video image; and

apply the change in the intensity setting and scale the brightness values.