METHOD AND SYSTEM FOR DETECTING FLICKER

• US 20140253754A1
• Filed: 03/04/2014
• Published: 09/11/2014
• Est. Priority Date: 03/06/2013
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: PAPIASHVILI, ILYA
• Granted Patent: US 9,288,404 B2
• Time in Patent Office: Days
• US Class Current: 348/226.1
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination

Abstract

An image processing system includes a plurality of active pixels and a plurality of flicker pixels. The active pixels output active pixel signals at a first readout frequency, and the flicker pixels output flicker pixel signals at a second readout frequency greater than the first readout frequency. A plurality of frequency detectors accumulate the flicker pixel signals and then perform frequency domain transformation of the accumulated flicker pixel signals. A frequency analyzer detects flicker by analyzing the flicker pixel signals which have been transformed into the frequency domain.

Claims

1. An image processing system comprising:

a plurality of active pixels to output active pixel signals at a first readout frequency;

a plurality of flicker pixels to output flicker pixel signals at a second readout frequency greater than the first readout frequency;

a plurality of frequency detectors to accumulate the flicker pixel signals and to perform frequency domain transformation of the accumulated flicker pixel signals; and

a frequency analyzer to detect flicker by analyzing the flicker pixel signals transformed into the frequency domain.

2. The system as claimed in claim 1, wherein each of the frequency detectors detects a dominant frequency among the flicker pixel signals transformed into frequency domain.

3. The system as claimed in claim 2, wherein the frequency detectors calculate confidence values indicating how dominant frequencies are different from remaining frequencies of the flicker pixel signals transformed into frequency domain.

4. The system as claimed in claim 3, wherein the frequency analyzer:

determines whether the confidence values are greater than a minimum confidence value, and

detects flicker when at least two of the confidence values are greater than the minimum confidence value.

5. The system as claimed in claim 1, further comprising:

an image sensor including the active pixels and flicker pixels, and

an image signal processor including the frequency detectors and the frequency analyzer.

6. The system as claimed in claim 1, further comprising:

an image sensor including the active pixels, the flicker pixels, the frequency detectors, and the frequency analyzer.

7. The system as claimed in claim 1, wherein:

the flicker pixels are located in a first region, an

the active pixels are located in a second region which does not overlap the first region.

8. The system as claimed in claim 1, wherein the flicker pixels are located between the active pixels.

9. The system as claimed in claim 1, further comprising:

a row driver to apply row selecting signals to the active pixels, the row selecting signals applied at the first readout frequency to read out the active pixel signals, the row driver to apply flicker selecting signals to the flicker pixels, the flicker selecting signals applied at the second readout frequency to read out the flicker pixel signals.

10. A method for detecting flicker in an image processing system, the method comprising:

accumulating flicker pixel signals output from flicker pixels;

performing frequency domain transformation for the accumulated flicker pixel signals; and

detecting flicker based on the flicker pixel signals transformed into the frequency domain, wherein the active pixels output active pixel signals at a first readout frequency, and the flicker pixels output the flicker pixel signals at a second readout frequency greater than the first readout frequency.

11. The method as claimed in claim 10, further comprising:

detecting a dominant frequency among the flicker pixel signals transformed into frequency domain.

12. The method as claimed in claim 10, further comprising:

applying row selecting signals corresponding to the first readout frequency to the active pixels to output the active pixel signals; and

applying flicker selecting signals corresponding to the second readout frequency to the flicker pixels to output the flicker pixel signals.

13. An image sensor, comprising:

a first number of active pixels; and

a second number of flicker pixels,

wherein the first number of active pixels outputs active pixel signals at a first frequency and the second number of flicker pixels outputs flicker signals at a second frequency greater than the first frequency.

14. The image sensor as claimed in claim 13, wherein the flicker pixels are arranged in a column between adjacent columns of the active pixels.

15. The image sensor as claimed in claim 13, wherein the first number is greater than one and the second number is one or more.

16. The image sensor as claimed in claim 13, wherein:

the active pixels are located in a first area, and

the flicker pixels are located in a second area which does not overlap the first area.

17. The image sensor as claimed in claim 13, wherein the flicker pixels are interleaved with the active pixels.

18. The image sensor as claimed in claim 17, wherein the active pixels are arranged in a plurality of first rows and the flicker pixels are arranged in a plurality of second rows interleaved with the first rows.

19. An image processing system including the image sensor claimed in claim 13.

20. An electronic device, comprising:

an image processor, and

the image sensor as claimed in claim 13 coupled to the image processor.