Methods and apparatuses for addressing chromatic aberrations and purple fringing

• US 8,786,709 B2
• Filed: 12/24/2012
• Issued: 07/22/2014
• Est. Priority Date: 01/28/2008
• Status: Expired due to Fees

• Current Assignee: FotoNation Limited (Adeia Inc.)
• Original Assignee: DigitalOptics Corporation Europe Limited (Adeia Inc.)
• Inventors: Stec, Piotr, Murray, Larry, Drimbarean, Alexandru
• Primary Examiner(s): CUTLER, ALBERT H
• Application Number:
  US13/726,510
• Publication Number:
  US 20130208151A1
• Time in Patent Office: 575 Days
• Field of Search: 348/187, 348/188
• US Class Current: 348/187
• CPC Class Codes: G06T 5/006 Geometric correction correction of chromatic aberrations adapted to be used in an image pickup device containing an electronic image sensor H04N23/10; detecting, correcting, reducing or removing artefacts resulting only from the lens unit, e.g. flare, shading, vignetting or "cos4" H04N25/61
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation
• CPC Class Codes: H04N 25/611 Correction of chromatic aberration

Abstract

Methods and systems for detecting and correcting chromatic aberration and purple fringing are disclosed. Chromatic aberration can be addressed by separating an image into color planes and then adjusting these to reduce chromatic aberration by using a specific calibration image (calibration chart) as an empirical method to calibrate the image acquisition device. Purple fringing can be corrected by initially addressing color aberration resulting from the lateral chromatic aberration (LCA). The LCA is first removed and then the correction is extended to purple fringing. A discovery is relied upon that the purple fringing is created in the direction of the chromatic aberration and is more pronounced in the direction of the chromatic aberration.

Claims

1. A processor-implemented method of correcting lateral chromatic aberrations in digital images within a digital image acquisition device, comprising:

calibrating a camera-lens pair, wherein the calibrating comprises;

detecting a point of a test image based on one or more characteristics of the point;

determining that the point is part of a measurement point;

measuring aberration of one or more colors at the measurement point; and

interpolating scattered data;

acquiring a digital image;

correcting lateral chromatic aberrations within the digital image, including;

finding a displacement for a current pixel in a temporary buffer;

designating the displacement as a relative position in a source buffer; and

interpolating a displacement value; and

outputting, storing, displaying, projecting, or transmitting a corrected digital image which has been corrected for lateral chromatic aberrations in two dimensions, or a further processed version of the digital image, or combinations thereof.

2. The method of claim 1, wherein the measuring aberration comprises thresholding.

3. The method of claim 1, wherein the calibrating further comprises:

finding and storing first and second data points in a first dimension;

applying linear interpolation to empty points between the first and second data points;

substituting value of second point to value of first point; and

incrementing a second dimension and repeating one or more times.

4. The method of claim 1, wherein the interpolating comprises applying a sinc filter.

5. The method of claim 4, wherein the sinc filter comprises a 5×

5 sinc filter.

6. The method of claim 1, wherein the interpolating said displacement value comprises estimating said displacement value by inverse distance weighting.

7. One or more non-transitory processor readable media having code embedded therein for programming a processor to perform a method of correcting lateral chromatic aberrations in digital images, wherein the method comprises:

calibrating a camera-lens pair, wherein the calibrating comprises;

detecting a point of a test image based on one or more characteristics of the point;

determining that the point is part of a measurement point;

measuring aberration of one or more colors at the measurement point; and

interpolating scattered data;

acquiring a digital image;

correcting lateral chromatic aberrations within the digital image, including;

finding a displacement for a current pixel in a temporary buffer;

designating the displacement as a relative position in a source buffer; and

interpolating a displacement value; and

outputting, storing, displaying, projecting, or transmitting a corrected digital image which has been corrected for lateral chromatic aberrations in two dimensions, or a further processed version of the digital image, or combinations thereof.

8. The one or more non-transitory processor readable media of claim 7, wherein the measuring aberration comprises thresholding.

9. The one or more non-transitory processor readable media of claim 7, wherein the calibrating further comprises:

finding and storing first and second data points in a first dimension;

applying linear interpolation to empty points between the first and second data points;

substituting value of second point to value of first point; and

incrementing a second dimension and repeating one or more times.

10. The one or more non-transitory processor readable media of claim 8, wherein the interpolating comprises applying a sinc filter.

11. The one or more non-transitory processor readable media of claim 10, wherein the sinc filter comprises a 5×

5 sinc filter.

12. The one or more non-transitory processor readable media of claim 7, wherein the interpolating said displacement value comprises estimating said displacement value by inverse distance weighting.

13. A portable digital image acquisition device comprising a lens, an image sensor, a processor, and one or more processor readable media having code embedded therein for programming the processor to perform a method of correcting lateral chromatic aberrations in digital images, wherein the method comprises:

calibrating a camera-lens pair, wherein the calibrating comprises;

detecting a point of a test image based on one or more characteristics of the point;

determining that the point is part of a measurement point;

measuring aberration of one or more colors at the measurement point; and

interpolating scattered data;

acquiring a digital image;

correcting lateral chromatic aberrations within the digital image, including;

finding a displacement for a current pixel in a temporary buffer;

designating the displacement as a relative position in a source buffer; and

interpolating a displacement value; and

outputting, storing, displaying, projecting, or transmitting a corrected digital image which has been corrected for lateral chromatic aberrations in two dimensions, or a further processed version of the digital image, or combinations thereof.

14. The portable digital image acquisition device of claim 13, wherein the measuring aberration comprises thresholding.

15. The portable digital image acquisition device of claim 13, wherein the calibrating further comprises:

finding and storing first and second data points in a first dimension;

applying linear interpolation to empty points between the first and second data substituting value of second point to value of first point; and

incrementing a second dimension and repeating one or more times.

16. The portable digital image acquisition device of claim 13, wherein the interpolating comprises applying a sinc filter.

17. The portable digital image acquisition device of claim 16, wherein the sinc filter comprises a 5×

5 sinc filter.

18. The portable digital image acquisition device of claim 13, wherein the interpolating said displacement value comprises estimating said displacement value by inverse distance weighting.