Image processing method, image capture device, and computer readable medium for forming an image based on spatial frequency components

1. An image processing method comprising:

obtaining first, second and third image planes from at least one image sensor, the first image plane formed from light of a first spectral distribution, the second image plane formed from light of a second spectral distribution, and the third image plane formed from light of a spectral distribution which substantially covers the visible spectrum;

generating first spatial frequency components from the first, second and third image planes;

generating a second spatial frequency component from the third image plane;

applying a color transform to the first spatial frequency components from the first, second and third image planes to obtain at least first, second and third transformed first spatial frequency image planes;

combining the at least first, second and third transformed first spatial frequency image planes with the second spatial frequency component from the third image plane to form an image.

2. The image processing method of claim 1 , the step of generating a second spatial frequency component from the third image plane comprising subtracting the first spatial frequency signal for the third image plane from the third image plane.

3. The image processing method of claim 1 , the step of generating first spatial frequency components from the first, second and third image planes comprising filtering using a spatial low pass filter.

4. The image processing method of claim 1 , the step of generating first spatial frequency components from the first, second and third image planes comprising block averaging and sub sampling the first, second and third image planes.

5. The image processing method of claim 4 , further comprising the step of up sampling the transformed first spatial frequency color planes.

6. The image processing method of claim 1 , the color transform being a transform to a color space, the color space being the RGB, CYMK, XYZ or sRGB color space.

7. An image capture device comprising:

a sensor module operable to generate first, second and third image signals, the first image signal representing light intensity of a first spectral distribution, the second image signal representing light intensity of a second spectral distribution and the third image signal representing light intensity of a spectral distribution substantially covering the visible spectrum;

a frequency filter module operable to produce first spatial frequency components from the first, second and third image signals and a second spatial frequency component from the third image signal;

a color transform module to transform the first spatial frequency components of the first, second and third image signals;

a combination module to combine the transformed first spatial frequency components and the second spatial frequency component from the third image signal.

8. The image capture device of claim 7 , the sensor module comprising first, second and third image sensors, the first image sensor having a first color filter to capture the first image signal, the second image sensor having a second color filter to capture the second image signal, and the third image sensor being substantially spectrally unfiltered to capture the third image signal.

9. The image capture device of claim 8 , the first color filter being red and the second color being green.

10. The image capture device of claim 8 , the first color filter being red and the second color being blue.

11. The image capture device of claim 7 , the frequency filter module operable to obtain the first spatial frequency components of the image signals by block filtering.

12. The image capture device of claim 11 , the frequency filter module comprising storage for a plurality of partial sums.

13. The image capture device of claim 11 , the frequency filter module operable to down sample the first spatial frequency components of the image signals, and the combination module operable to up sample the transformed first spatial frequency components.

14. The image capture device of claim 13 , wherein the frequency filtering module is operable to block average over blocks having sides of an odd number of pixels and the combination module is operable to up sample using bilinear interpolation.

15. The image capture device of 13 , wherein the frequency filtering module is operable to block average over blocks having sides of an even number of pixels and the combination module is operable to up sample using nearest neighbor interpolation.

16. The image capture device of claim 8 , wherein the first and second image sensors are lower in spatial resolution than the third image sensor.

17. The image capture device of claim 7 being a scanner.

18. The image capture device of claim 7 , the sensor module comprising a single sensor; the image capture device further comprising an illumination component operable to produce an illumination of the first spectral distribution, the second spectral distribution and an illumination which substantially covers the visible spectrum.

19. A non-transitory computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform operations comprising:

obtaining first, second and third image planes from an image capture device, the first image plane formed from light of a first spectral distribution, the second image plane formed from light of a second spectral distribution, and the third image plane formed from light of a spectral distribution which substantially covers the visible spectrum;

generating first spatial frequency components for the first, second and third image planes;

generating a second spatial frequency component from the third image plane;

transforming the first spatial frequency components from the first, second and third planes into a color space;

combining the transformed first spatial frequency components with the second spatial frequency component.

20. The computer-readable medium of claim 19 , wherein the operations further comprise controlling the image capture device to capture the first, second and third image planes.