Method and system for automatic correction of chromatic aberration

• US 20070242897A1
• Filed: 04/18/2006
• Published: 10/18/2007
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Innovation Asset Collective
• Original Assignee: Tandent Vision Science, Inc.
• Inventors: Maxwell, Bruce, Friedhoff, Richard, Bushell, Steven
• Granted Patent: US 7,865,031 B2
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• 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

Abstract

In a first exemplary embodiment of the present invention, an automated, computerized method is provided for an automatic chromatic aberration correction. The method comprises the steps of setting a range of test correction factors, applying the test correction factors of the range, incrementally, to a test block of the image, measuring chromatic aberration error at the test block after application of each of the test correction factors, and selecting a test correction factor having a lowest chromatic aberration error.

Claims

1. An automated, computerized method for an automatic correction of chromatic aberration in an image, comprising the steps of:

setting a range of test correction factors;

applying the test correction factors of the range, incrementally, to a test block of the image;

measuring chromatic aberration error at the test block after application of each of the test correction factors; and

selecting a test correction factor having a lowest chromatic aberration error.

2. The method of claim 1 wherein the step of applying the test correction factors of the range, incrementally, to a test block of the image is carried out by repeating the step for each of a plurality of test blocks in the image and selecting a test correction factor having a lowest chromatic aberration error at each of the plurality of test blocks.

3. The method of claim 2 comprising the further step of identifying each of the plurality of test blocks by dividing the image into discrete segments and identifying a test block within each segment.

4. The method of claim 3 wherein each segment of the image comprises a concentric circle.

5. The method of claim 3 wherein the step of identifying a test block within the segment is carried out by determining a point having a highest dark/light contrast within the segment.

6. The method of claim 1 wherein the step of measuring chromatic aberration error at the test block after application of each of the test correction factors is carried out by plotting N band color channels for pixels of the test block in a color space, defining a reference line between darkest and brightest pixels of the plot and measuring a chromatic aberration error as function of pixel distance from the reference line.

7. The method of claim 1 comprising the further step of applying the selected test correction factor to correct chromatic aberration in the image.

8. The method of claim 3 comprising the further step of applying each of the selected test correction factors to correct chromatic aberration in a corresponding segment of the image.

9. The method of claim 3 comprising the further step of utilizing the selected test correction factors to generate a model of the test block correction factors, to provide a correction factor model for the image for correcting chromatic aberration in the image.

10. The method of claim 9 wherein the model is generated as a function of a polynomial model algorithm.

24. The method of claim 5 comprising the further step of ascertaining whether the block having a highest dark/light contrast within the segment, contains pixels that are clipped at a bright end, and disregarding one of that block and individual pixels of that block, if such a condition is ascertained.

11. An automated, computerized method for an automatic correction of chromatic aberration in an image, comprising the steps of:

setting a range of test correction factors;

for each of the test correction factors of the range, applying the test correction factor to the image and plotting N band color channels for pixels of the image after application of a test correction factor from the range, in a color space;

defining a reference line of the plot;

measuring a chromatic aberration error as a function of pixel distance from the reference line; and

selecting a test correction factor from the range having a lowest chromatic aberration error.

12. The method of claim 11 wherein the N bands comprise RGB color values.

13. The method of claim 11 wherein the reference line is a centerline between a bright pixel and a dark pixel of the plot.

14. The method of claim 11 wherein the step of plotting N band color channels for pixels of the image in a color space is carried out by plotting pixels of a test block of the image.

15. The method of claim 11 wherein the range of test correction factors is set by fixing a number of incremental steps between relative values for the N bands.

16. The method of claim 15 comprising the further steps of after selecting a test correction factor from the range having a lowest chromatic aberration error, resetting the range of test correction factors around the correction factor having the lowest chromatic aberration error, and repeating the steps of claim 11 for the reset range of test correction factors.

17. An automated, computerized method for measuring chromatic aberration in an image, comprising the steps of:

plotting N band color channels for pixels of the image in a color space;

defining a reference line of the plot; and

measuring a chromatic aberration error as a function of pixel distance from the reference line.

18. The method of claim 17, wherein the steps of claim 17 are performed on a test block pixels of the image.

19. The method of claim 18 wherein the reference line is a centerline between a bright pixel and a dark pixel of the plot of the test block of pixels.

20. The method of claim 18 wherein the reference line comprises a primary eigenvector of a covariance matrix of the test block of pixels.

21. A computer system which comprises:

a CPU; and

a memory storing an image file;

the CPU arranged and configured to execute a routine to set a range of test correction factors, apply the test correction factors of the range, incrementally, to a test block of the image file, measure chromatic aberration error at the test block after application of each of the test correction factors, and select a test correction factor having a lowest chromatic aberration error.

22. A computer system which comprises:

a CPU; and

a memory storing an image file;

the CPU arranged and configured to execute a routine to set a range of test correction factors, for each of the test correction factors of the range, apply the test correction factor to the image file and plot N band color channels for pixels of the image file after application of a test correction factor from the range, in a color space, define a reference line of the plot, measure a chromatic aberration error as a function of pixel distance from the reference line and select a test correction factor from the range having a lowest chromatic aberration error.

23. A computer system which comprises:

a CPU; and

a memory storing an image file;

the CPU arranged and configured to execute a routine to plot N band color channels for pixels of the image in a color space, define a reference line of the plot and measure a chromatic aberration error as a function of pixel distance from the reference line.

25. An automated, computerized method for an automatic correction of chromatic aberration in an image, comprising the steps of:

providing a raw image from an image sensor;

plotting N band color channels for pixels related to the raw image, in a color space;

p1 defining a reference line of the plot;

measuring a chromatic aberration error as a function of pixel distance from the reference line; and

generating a correction factor as a function of the measured chromatic aberration error, to correct chromatic aberration in the raw image.

26. The method of claim 25 comprising the further step of using the raw image with corrected chromatic aberration, to generate full image pixels.

27. The method of claim 25 wherein the pixels related to the raw image comprise pixels of a reference image generated as a function of the raw image.

28. A computer system which comprises:

a CPU; and

a memory storing an image file as a raw image;

the CPU arranged and configured to execute a routine to plot N band color channels for pixels related to the raw image, in a color space, define a reference line of the plot, measure a chromatic aberration error as a function of pixel distance from the reference line, and generate a correction factor as a function of the measured chromatic aberration error, to correct chromatic aberration in the raw image.

29. An optical device comprising:

a lens;

an image sensor coupled to the lens, to generate a raw image; and

a CPU coupled to the image sensor;

the CPU arranged and configured to execute a routine to plot N band color channels for pixels related to the raw image, in a color space, define a reference line of the plot, measure a chromatic aberration error as a function of pixel distance from the reference line, and generate a correction factor as a function of the measured chromatic aberration error, to correct chromatic aberration in the raw image.

30. The optical device of claim 29, wherein the optical device comprises a camera.

31. An automated, computerized method for measuring chromatic aberration in an image, comprising the steps of:

plotting N band color channels for pixels of the image in a color space;

defining a reference line of the plot;

measuring a chromatic aberration error as a function of pixel distance from the reference line; and

generating a correction factor as a function of the measured chromatic aberration error, to correct chromatic aberration in the image.

32. An optical device comprising:

a lens;

an image sensor coupled to the lens, to generate an image; and

a CPU coupled to the image sensor;

the CPU arranged and configured to execute a routine to plot N band color channels for pixels related to the image, in a color space, define a reference line of the plot, measure a chromatic aberration error as a function of pixel distance from the reference line, and generate a correction factor as a function of the measured chromatic aberration error, to correct chromatic aberration in the image.

33. The optical device of claim 32, wherein the optical device comprises a camera.